EP4325142A1 - Ejector having an actuation mechanism with a pilot valve and an equalization passage between two cylinder chambers - Google Patents
Ejector having an actuation mechanism with a pilot valve and an equalization passage between two cylinder chambers Download PDFInfo
- Publication number
- EP4325142A1 EP4325142A1 EP22190394.1A EP22190394A EP4325142A1 EP 4325142 A1 EP4325142 A1 EP 4325142A1 EP 22190394 A EP22190394 A EP 22190394A EP 4325142 A1 EP4325142 A1 EP 4325142A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- needle
- ejector
- nozzle
- inlet
- cylinder chamber
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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- 230000007246 mechanism Effects 0.000 title claims abstract description 16
- 239000012530 fluid Substances 0.000 claims abstract description 138
- 238000004891 communication Methods 0.000 claims abstract description 23
- 238000011144 upstream manufacturing Methods 0.000 claims description 7
- 239000003507 refrigerant Substances 0.000 abstract description 3
- 230000007704 transition Effects 0.000 description 17
- 238000005057 refrigeration Methods 0.000 description 14
- 239000000463 material Substances 0.000 description 9
- 238000006073 displacement reaction Methods 0.000 description 6
- 230000008859 change Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000012423 maintenance Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2341/00—Details of ejectors not being used as compression device; Details of flow restrictors or expansion valves
- F25B2341/001—Ejectors not being used as compression device
- F25B2341/0013—Ejector control arrangements
Definitions
- the present invention relates to an ejector, e.g. for a refrigeration circuit with circulated refrigerant, with a primary (fluid) inlet, a secondary (fluid) inlet, a (fluid) outlet, a nozzle, and a mixing portion for mixing fluid supplied with a high pressure at the primary inlet and fluid sucked from the secondary inlet.
- the invention further relates to an ejector assembly with at least two ejectors.
- fluid is supplied by the refrigeration circuit with the high pressure to the primary inlet.
- the refrigeration circuit supplies fluid to the secondary inlet with a secondary pressure that is less than the high pressure.
- the nozzle jets the fluid received at the primary inlet into the mixing portion. Thereby, a flow velocity is increased. Fluid received at the secondary inlet is additionally sucked into the mixing portion. As a result, the fluid received at the primary inlet mixes with the fluid received at the secondary inlet in the mixing portion. Thereafter, the combined fluid flow leaves the ejector through the outlet.
- a diffuser is arranged between the mixing portion and the outlet. In some applications, a flow of fluid through the nozzle can be prevented. By this, the ejector is closed.
- ejectors are known from WO 2018/159320 A1 , US 7,841,193 B2 , JP 4 134 918 B2 , and EP 1 923 575 A2 .
- Fast opening or closing of an ejector can cause fast pressure variations in the refrigeration circuit employing the ejector, e.g. pressure peaks. This can lead to damages of components of the refrigeration circuit. Furthermore, this can lead to instability in the controlling of the refrigeration system.
- stepper motors are particularly expensive and not perfectly suitable for all applications.
- an ejector e.g. for a refrigeration circuit with circulated refrigerant, according to claim 1.
- the ejector comprises:
- the present invention ensures smooth opening and closing of the ejector. Pressure peaks due to fast opening and/or closing are reliably avoided.
- the implementation is cost-effective. For example, no expensive stepper motor is needed in order to ensure smooth opening and closing.
- the risk is reduced that the needle moves with excessive speed and/or flutters due to external pressure fluctuations, e.g. to fluctuations of a primary pressure applied to the primary inlet by an external refrigeration circuit.
- Fluid from the primary inlet can enter the first cylinder chamber via the chamber inlet. This allows filling up the first cylinder chamber while the (volume of) the first cylinder chamber increases.
- the drain passage is configured for discharging fluid from the second cylinder chamber when the pilot valve is open. This allows decreasing the (volume of) the second cylinder chamber (by displacement of the piston in the cylinder).
- the equalization passage allows that fluid flows from the first cylinder chamber to the second cylinder chamber.
- the pilot valve is closed.
- no fluid is discharged from the second cylinder chamber.
- the piston is displaced in order to maximize (the volume of) the second cylinder chamber.
- the second cylinder chamber is filled up by the fluid from the first cylinder chamber entering the second cylinder chamber through the equalization passage while the (volume of) the second cylinder chamber increases. At the same time, the (volume) of the first cylinder chamber is decreased.
- the drain passage is blocked (closed) when the solenoid valve is in a closed state.
- the chamber inlet, the equalization passage, and the drain passage may be completely integrated in the ejector. They are not constituted by fluid connections provided by an environment or any outer element. In particular, they are not constituted by any fluid connections of a refrigeration circuit employing the ejector that are not part of the ejector as such.
- the actuating mechanism is for moving the needle along a longitudinal direction between the opened position and the closed position.
- the cylinder may extend parallel to the longitudinal axis and the piston may be configured to reciprocate parallel to the longitudinal axis in the cylinder for either maximizing (the volume of) the first cylinder chamber (such that the needle is in the opened position) or maximizing (the volume of) the second cylinder chamber (such that the needle is in the closed position).
- the longitudinal direction may be parallel to a central axis.
- the cylinder, the piston, the needle, the needle seat, the nozzle, and/or the mixing portion may extend at least substantially along the central axis.
- a diffuser portion may be formed downstream of the mixing portion.
- the diffuser portion may extend along the central axis.
- the (whole) ejector extends substantially along the central axis.
- a piston area is a cross-section area of the piston.
- the piston area may be defined within a plane perpendicular to the longitudinal direction.
- the piston area is at least 1000 times a flow cross-section of the equalization passage. Especially, the piston area may be at least 1600 times the flow cross-section of the equalization passage.
- the flow cross-section of the equalization passage limits, by its flow resistance, a flow rate (e.g. measured in ml/s) between the first cylinder chamber to the second cylinder chamber.
- the total volume change of the second cylinder chamber during opening increases with increasing piston diameter.
- a closing time is extended.
- the piston's velocity during opening is slower.
- the piston's velocity reaches a substantially constant value shortly after transition from the opened position to the closed position has started. This value may be related to the flow rate divided by the piston area.
- the piston area may be at least 1200 times a flow cross-section of the drain passage, especially at least 1920 times.
- the flow cross-section of the drain passage limits a fluid discharge rate (e.g. measured in ml/s), with which fluid can be discharged from the second cylinder chamber via the drain passage when the pilot valve is open.
- a net flow rate for the second cylinder chamber may be (at least substantially) determined by the fluid discharge rate and the flow rate of fluid entering through the equalization passage.
- the piston's velocity may reach a substantially constant value shortly after transition from the closed position to the second position has started. This value may be related to the net flow rate divided by the piston area. If the piston area and hence the total volume change of the second cylinder chamber required for opening are increased, the opening time is extended.
- piston area increases with respect to the flow cross-section of the equalization passage while the flow cross-section of the drain passage remains the same.
- piston area increases with respect to the equalization passage as well.
- a needle seat area which is a cross-section area of the needle seat where the needle engages the needle seat in the closed position, is in the range from 1,005 to 1,4 times a flow cross-section of the nozzle.
- the cross-section area of the needle seat is particularly small. Accordingly, the effects of pressure changes at a needle tip when then the needle is arriving at the needle seat and starting to lift off from the needle seat are minimized. This facilitates smooth and controlled opening and closing of the ejector.
- the ejector may comprise a housing. This ensures protection of the components inside the housing.
- the housing may include a main sleeve. An interior of the main sleeve may extend along the central axis.
- the housing may further include a top cover.
- the top cover can be fixed to an end of the main sleeve in the longitudinal direction at a side opposite to the outlet.
- the top cover may be removably fixed to the main sleeve. This facilitates maintenance.
- the pilot valve is a solenoid valve.
- Solenoid valves are particularly inexpensive, reliable, and easy to control. It is not necessary to control an exact opening degree of the pilot valve.
- the present invention ensures smooth opening and closing also in the case that the pilot valve can be switched only between an open state and a closed state. No additional intermediate states of the pilot valve are needed in order to keep the movement speed of the needle below a pre-determined threshold.
- the piston area corresponds to at least 20 times the needle seat area.
- a stroke of the needle between the closed position and the opened position correspond to at least 2*(A noz / ⁇ ) 0,5 , where A noz is the flow cross-section of the nozzle.
- the ejector comprises a check valve function for preventing fluid flow from the outlet to the secondary inlet.
- the first cylinder chamber may be a piston-rod side cylinder chamber.
- the second cylinder chamber me be the cylinder chamber in the same cylinder at the other side of the piston.
- the needle may be formed integrally with the piston.
- the needle may be a piston rod at the same time. This is a particularly reliable, cost-effective, and lightweight implementation. It may include at least one hole extending thorough the piston.
- the equalization passage is formed (completely) in the piston. This allows fast and cost-efficient production.
- the flow cross-section of the equalization passage may be in the range from 1,2 to 2,5 times the flow cross-section of the drain passage when the pilot valve is in its open state. This ensure that a flow resistance of the drain passage is higher than a flow resistance of the equalization passage. Only a slight pressure drop from the first cylinder chamber to the second cylinder portion occurs even during the needle's transition from the closed position to the opened position. The movement velocity of the piston and the needle can be precisely controlled and kept low. This further facilitates smooth opening of the ejector.
- the flow cross-section of the drain passage can be determined by the flow cross-section of the pilot valve.
- the pilot valve can be designed to be as small as possible. This reduces the costs. Accordingly, the flow cross-section of the equalization passage may be in the range from 1,2 to 2,5 times a flow cross-section of the pilot valve when the pilot valve is in its open state.
- a flow cross-section of the chamber inlet is larger than the flow cross-section of the equalization passage.
- the flow cross-section of the chamber inlet may be at least 5 times, especially at least 10 times, the flow cross-section of the equalization passage.
- the needle seat is at least axially fixed with respect to the housing. This facilitates precise opening and closing of the ejector.
- the nozzle may be arranged in an interior of the housing. It may be at least axially fixed with respect to the housing.
- the nozzle may comprise a throat portion and a divergent nozzle portion.
- the throat portion may define the flow cross-section of the nozzle.
- the divergent nozzle portion may be arranged downstream of the throat portion. It may be of a conical shape, wherein an inner diameter increases towards a downstream end of the nozzle. The downstream end of the nozzle may protrude towards the mixing portion.
- a nozzle inlet is formed directly upstream of the nozzle, wherein the nozzle inlet tapers toward the nozzle, wherein the needle seat is located in the nozzle inlet, and wherein a length of the nozzle inlet may correspond to at least 1,8 times the stroke of the needle between the closed position and the opened position.
- the nozzle inlet and the nozzle can be formed in a one-piece component, e.g. in a nozzle insert.
- the nozzle insert may be mounted to an insert assembly holder that is mounted in the housing, e.g. in an interior of the main sleeve.
- the nozzle insert may be fixed to the housing. However, it may be removably fixed to the housing in order to facilitate maintenance.
- the ejector can comprise a resilient member acting against minimizing (the volume of) the second cylinder chamber by the piston.
- the resilient member urges the piston towards maximizing (the volume of) the second cylinder chamber.
- the resilient member may urge the needle towards its closed position.
- the resilient member may engage directly with the piston and/or directly with the needle.
- the resilient member may be provided between an end wall of the cylinder at the side of the second cylinder chamber and the piston. The resilient member facilitates the transition of the needle from its opened position to its closed position.
- the resilient member may include a coil spring.
- the ejector is configured such that the opening time of the needle is at least 0,5 s, e.g. at least 1 s.
- the long opening time prevents fast pressure variations and hence reduces a risk of damages in a refrigeration circuit employing the ejector.
- the ejector is configured such that the closing time of the needle is at least 1 s, e.g. at least 2 s.
- the long closing time prevents fast pressure variations and hence reduces a risk of damages in a refrigeration circuit employing the ejector.
- the ejector is configured such that the needle moves, during the transition from its closed position to its opened position (in normal operation), with a substantially constant velocity over a displacement length corresponding to at least 70 % of the stroke. This ensures controlled and smooth opening and reduces the risk of damages in any refrigeration circuit employing the ejector.
- the ejector is configured such that the needle moves, during the transition from its opened position to its closed position (in normal operation), with a substantially constant velocity over a displacement length corresponding to at least 70 % of the stroke. This ensures controlled and smooth closing and reduces the risk of damages in any refrigeration circuit employing the ejector.
- Substantially constant velocity may mean that the velocity changes by 15 % at the maximum during the respective movement phase.
- the flow cross-section of the nozzle is at least 50 mm 2 .
- the ejector exhibits a high capacity.
- the cylinder is formed by a cylinder insert and the top cover.
- the cylinder insert may be inserted in an interior of the main sleeve.
- the cylinder insert may be removably mounted in the main sleeve. This facilitates maintenance.
- the ejector may comprise an elastic member, for example a spring, especially a coil spring.
- the elastic member may bias the cylinder insert against the top cover.
- the second cylinder chamber may be arranged at the side of the top cover. This ensures proper sealing between those elements. This ensures that the pressure propagation to the second cylinder chamber is determined by the pressure propagation from the first cylinder chamber to the second cylinder chamber via the equalization passage. A risk of substantial leakage and pressure propagation from the primary inlet to the second cylinder chamber that bypasses the equalization passage is reduced.
- An annular end face of the cylinder insert for abutting on the top cover may be ground flat.
- the elastic member may be squeezed between the cylinder insert and a member that is at least axially fixed with respect to the housing.
- the elastic member may be squeezed between the cylinder insert and the insert assembly holder.
- the ejector comprises a filter between the primary fluid inlet and the needle seat.
- the filter may be arranged circumferentially about the needle and the needle seat. It may be supported by the elastic member.
- the needle is made of a first material and the needle seat is made of a second material, wherein a hardness of the second material is higher than a hardness of the first material.
- the hardness of the second material may correspond to at least 1,4 times the hardness of the second material.
- the nozzle insert (which includes the needle seat) is made of the second material.
- an ejector assembly comprising at least two ejectors according to any one of the described embodiments and modifications.
- the ejectors may be arranged in parallel.
- a flow cross-section of a second one of the at least two ejectors is different from a flow cross-section of a first one of the at least two ejectors.
- the flow cross-section of the second one can be at least 1,2 times the flow cross-section of the first one.
- a flow cross-section of an element (like a passage, a channel, or the like, e.g. the nozzle), this may mean a minimum cross-section of the respective element along an intended flow direction through the element.
- FIG. 1 An embodiment of an ejector 1 according to the present invention is shown in Fig. 1 .
- the ejector 1 comprises a primary (fluid) inlet 2, a secondary (fluid) inlet 7, and an (fluid) outlet 12.
- the primary inlet 2 may be also referred to as high pressure inlet 2.
- the ejector 1 extends along a central axis C.
- a longitudinal direction L is parallel to the central axis C.
- fluid can flow from the first inlet 2 through a nozzle 5, a mixing portion (which includes a convergent mixing portion 6 and a cylindrical mixing portion 10), and a diffuser portion 11 to the fluid outlet 12.
- fluid is drawn from the secondary inlet 7 into the mixing portion 6.
- the fluid drawn from the secondary inlet 7 joins the fluid from the primary inlet 2 in the convergent mixing portion 6. This results in mixing of the fluid from the primary inlet 2 and the fluid drawn from the secondary inlet 7 in the convergent mixing portion 6 and the cylindrical mixing portion 10 that follows downstream of the convergent mixing portion 6.
- the ejector 1 includes a needle valve mechanism with a needle 20 and a needle seat 26.
- the needle 20 If the needle 20 is in a closed position (not shown), it abuts the needle seat 26 and blocks the fluid connection between the primary inlet 1 and the nozzle 5. This prevents that fluid from the primary inlet 1 can enter into the nozzle 5 and flow further into the convergent mixing portion 6. This corresponds to a closed state of ejector 1.
- the needle 20 is lifted from the needle seat 26 by a needle stroke S (see Fig. 4 ). This allows fluid flow from the primary inlet 2 into the nozzle 5.
- the stroke S is the displacement of the needle 20 along the longitudinal direction L between its opened position and its closed position.
- the stroke S may be at least 10 mm, for example in the range from 12 mm to 30 mm.
- a housing 70 of the ejector 1 includes a main sleeve 71, an upstream-side top cover 76, a first diffuser tube 74, and a second diffuser tube 75.
- the first diffuser tube 74 and the second diffuser tube 75 form at least a downstream part of the diffuser portion 11.
- the housing 70 further includes a primary (fluid) inlet connector 72, which is fixed to the main sleeve 71 and forms the primary inlet 2, and a secondary (fluid) inlet connector 73, which is fixed to the main sleeve 71 and forms the secondary inlet 7.
- the ejector 1 further comprises an actuating mechanism 30 for moving the needle 20 along the longitudinal direction L between the opened position and the closed position.
- the actuating mechanism 30 comprises a pilot valve 50 and a piston 31.
- the piston 31 is arranged in a cylinder 35 and can be axially displaced within the cylinder 35 (i.e. along the central axis C).
- the needle 20 is mechanically connected to the piston 31 such that the axial movement of the piston 31 in the cylinder 35 is transferred to movement of the needle 20 along the longitudinal direction L. Accordingly, the needle 20 can be moved from its opened position to its closed position and vice versa by corresponding axial movements of the piston 31.
- the needle 20, the piston 31, and the cylinder 35 are all arranged coaxially along the central axis C and the needle 20 is at least axially fixed to the piston 31.
- the needle 20 and the piston 31 can be formed integrally (in one piece) as shown in Figs. 1 to 3 .
- the needle 20 (in particular a needle stem 25) also constitutes a piston rod for the piston 31.
- the cylinder 35 can be formed by a cylinder insert 77 and the top cover 76 as shown in Figs. 1 to 3 .
- the cylinder insert 77 is arranged in an interior of the main sleeve 71 and directly abuts the top cover 76.
- the cylinder insert 77 guides the piston 31 and its piston rod (which is the needle 20 in this embodiment).
- the piston 31 is configured to form a first cylinder chamber 37 and a second cylinder chamber 38 within the cylinder 35. It can divide an interior of the cylinder 35 into the first cylinder chamber 37 and the second cylinder chamber 38 (along the longitudinal direction L).
- a volume of the first cylinder chamber 37 is maximized (maximal) when the needle 20 is in its opened position. It is minimized when the needle 20 is in its closed position. It may decrease (at least substantially) to a minimum volume (small residual volume) when the needle 20 is in its closed position (not shown, corresponds to a lowermost possible position of the piston 31 in Figs. 1 to 3 ).
- a volume of the second cylinder chamber 38 is maximized (maximal) if the needle 20 is in its closed position. It is minimized when the needle 20 is in its opened position (correspond to an uppermost possible position of the piston 31 as shown in Figs. 1 to 3 ). It may decrease (at least substantially) to zero when the needle 20 is in its opened position.
- an annular end wall 40 which is provided on a surface of the piston 31 facing the second cylinder chamber 38, causes that a residual volume of the second cylinder chamber 38 remains even if the needle 20 is in its opened position. This ensures that the equalization passage 32 is not closed when the needle 20 is in the opened position.
- a primary (fluid) inlet chamber 3 is formed at a side of the cylinder insert 77 in the longitudinal direction L that faces away from the top cover 76.
- the primary inlet connector 72 opens into the primary inlet chamber 3.
- the first cylinder chamber 37 is in fluid communication with the primary inlet 2 via a chamber inlet 36.
- the chamber inlet 36 is a fluid connection provided between the primary inlet chamber 3 and an end of the cylinder 35 in the longitudinal direction L at the side of the needle 20 (an end of the cylinder 35 at the side of the first cylinder chamber 37, i.e. a lower end of the cylinder 35 in Figs. 1 to 3 ).
- the chamber inlet 36 may be formed in the cylinder insert 77, for example as at least one bore extending along the longitudinal direction L. In the embodiment shown in Figs. 1 and 2 , four or six of such bores are formed in the cylinder insert 77. Two of them can be seen in Figs. 1 and 2 .
- the other end of the cylinder 35 in the longitudinal direction L is in fluid communication with the secondary inlet 7 via a drain passage.
- the pilot valve 50 is arranged in the drain passage. When the pilot valve 50 is in its closed state, it blocks (closes) the drain passage. When the pilot valve 50 is in its open state, the drain passage is open and the second cylinder chamber 38 is in fluid communication with the secondary inlet 7.
- the drain passage is formed between the second cylinder chamber 38 on the one hand and, on the other hand, the secondary inlet 7 and/or a space that is in (direct) fluid communication with the secondary inlet 7.
- the drain passage is formed between the second cylinder chamber 38 and a secondary (fluid) inlet chamber 8, which is in direct fluid communication with the secondary inlet 7.
- the second cylinder chamber 38 is in fluid communication with the outlet 12 via the drain passage when the pilot valve 50 is in an open state.
- the drain passage with the solenoid valve 50 is formed between the second cylinder chamber 38 and the fluid outlet 12 and/or a space that is in fluid communication with the fluid outlet 12 in this case.
- a blocking means e.g. a check valve, can be employed to prevent fluid flow from the secondary inlet 7 to the fluid outlet 12 via the drain passage.
- the drain passage may be formed completely within the ejector 1. It is integrated in the ejector 1 as such.
- the drain passage includes a fluid connection 39 between the upper end of the cylinder 35 (the second cylinder chamber 38) and an upstream side of the pilot valve 50.
- Said fluid connection 39 may be also referred to as the chamber outlet 39.
- the chamber outlet 39 may be formed by at least one channel, for example two channels, within the top cover 76.
- the drain passage includes a first fluid passage 54 formed in the top cover 76, a second fluid passage 55 that is also formed in the top cover 76, a fluid passage 56 formed in the main sleeve 71, and a fluid passage 57 formed between the main sleeve 71 and an insert assembly holder 78.
- the fluid passage 57 is a substantially annular gap between the main sleeve 71 and the insert assembly holder 78.
- the drain passage opens into the secondary inlet chamber 8.
- the secondary inlet connector 73 also opens into the secondary inlet chamber 8. Hence, the downstream side of the pilot valve 50 is in fluid communication with the secondary inlet 7, and the second cylinder chamber 38 is in fluid communication with the secondary inlet 7 when the pilot valve 50 is in its open state.
- the second cylinder chamber 38 is in fluid communication with the first cylinder chamber 37.
- the fluid communication is provided by an equalization passage 32.
- the equalization passage 32 includes longitudinal bore through the piston 31.
- the equalization passage 32 may be formed completely within the ejector 1. It is integrated in the ejector 1 as such.
- the pilot valve 50 includes a valve seat 51, a valve member 52, and an actuator 53.
- the actuator 53 is configured to switch the pilot valve 50 between an open state and a closed state thereof.
- the pilot valve 50 is a solenoid valve.
- the actuator 53 is a solenoid actuator.
- the pilot valve 50 is a part of the ejector 1.
- the valve seat 51 may be integrally formed with the housing 70 or an insert fixed to the housing.
- the valve seat 51 is mounted within the top cover 76.
- a (minimum) flow cross-section A pci of the chamber inlet 36 is larger than a (minimum) flow cross-section A eq of the equalization passage 32.
- the flow cross-section A pci of the chamber inlet 36 may be at least 5 times, especially at least 10 times, the flow cross-section A eq of the equalization passage 32.
- the flow cross-section A pci of the chamber inlet 36 is the sum of the cross-sectional areas of the bores constituting the chamber inlet 36, which are formed in the cylinder insert 77.
- the fluid pressure in the first cylinder chamber 37 at least substantially corresponds to the primary pressure at the primary inlet 2.
- the fluid pressure in the first cylinder chamber 37 forces the piston 31 (along the longitudinal direction L) towards the top cover 76 and hence the needle 20 towards its opened position, against a resilient force provided by a resilient member 33.
- the resilient member 33 is a coil spring.
- fluid is supplied at the secondary inlet 7 with a secondary pressure.
- the secondary pressure is less than the primary pressure at the primary inlet 2 but higher than an outlet pressure at the fluid outlet 12. In other words, there is a pressure drop from the primary pressure to the secondary pressure.
- This pressure drop is used for jetting the fluid from the primary inlet chamber 3 through the nozzle 5 into the convergent mixing portion 6 when the needle 20 is in its opened position.
- the fluid jetted out of the nozzle 5 has a high velocity.
- the ejection through the nozzle 5 results in a pressure drop from the primary inlet chamber 3 to the convergent mixing portion 6.
- fluid provided at the secondary inlet 7 is sucked from the secondary inlet chamber 8 through a secondary fluid passageway 9 into the convergent mixing portion 6.
- the fluid from the primary inlet 2, which is ejected by the nozzle 5, and the fluid sucked from the secondary inlet chamber 8 mix in the convergent mixing portion 6 and the cylindrical mixing portion 10.
- the pilot valve 50 is in its open state at the beginning.
- a small fluid flow from the first cylinder chamber 37 to the second cylinder chamber 38 via the equalization passage 32 occurs.
- the pressure drop is sufficiently high for holding the piston 31 in abutment with the top cover 76 against the restoring force of the resilient element 33.
- the flow cross-section A eq of the equalization passage 32 is comparatively small. It may be less than 10 mm 2 , e.g. in the range from 0,5 mm 2 to 4 mm 2 . Additionally or alternatively, a value corresponding to the square of a length L eq of the equalization passage 32 (along a flow direction therethrough) may be at least 15 times, for example at least 25 times, the flow cross-section A eq of the equalization passage 32 (L eq 2 ⁇ 15*A eq ). The equalization passage 32 exhibits considerable flow resistance.
- equalization passage 32 has a cylindrical shape, its flow cross-section A eq is ⁇ *(D eq /2) 2 , wherein D eq is a diameter of the equalization passage 32.
- the flow cross-section A eq of the equalization passage 32 can be larger or the same as a (minimum) flow cross-section A dp of the drain passage (when the pilot valve 50 is in its open state).
- an intermediate pressure occurs in the second cylinder chamber 38.
- the intermediate pressure is lower than the pressure in the first cylinder chamber 37 (which may at least substantially correspond to the primary pressure).
- the intermediate pressure is larger than the secondary pressure.
- the exact value of the intermediate pressure depends, inter alia, on the flow resistance and hence on the flow cross-section A eq of the equalization passage 32 as well as on a flow resistance and hence on the flow cross-section A dp of the drain passage and on a ratio A eq /A dp .
- the flow resistance of the drain passage is considerably smaller than the flow resistance of the equalization passage 32.
- the flow cross-section A eq of the equalization passage 32 may be larger than the flow cross-section A dp of the drain passage (A eq /A dp > 1). Especially, the flow cross-section A eq of the equalization passage 32 may be in the range from 1,2 to 2,5 times the flow cross-section A dp of the drain passage (1,2* A dp ⁇ A eq ⁇ 2,5* A dp ). The flow resistance of the equalization passage 32 is smaller than the flow resistance of the drain passage. However, the pressure-drop from first cylinder chamber 37 to the second cylinder chamber 38 is smaller in that case.
- the intermediate pressure in the second cylinder chamber 38 is less than pressure in the first cylinder chamber 37 when the pilot valve 50 is in its open state. In other words, there is nevertheless the small pressure drop.
- the small pressure drop remains due to the flow resistance exhibited by the equalization passage 32 and due to ongoing discharge of fluid out of the second cylinder chamber 38.
- the ejector 1 may be configured such that a pressure drop from the first cylinder chamber 37 to the second cylinder chamber 38 (i.e. a pressure drop along the equalization passage 32) is less than 10 bar, especially less than 3 bar, in normal operation if the pilot valve 50 after the pilot valve 50 is open for at least 0,2 s.
- the ejector 1 may be configured such that an opening time of the needle 20 is at least 0,5 s in normal operation, especially at least 1 s.
- the opening time may be a time needed for the movement of the needle 20 from its closed position to its opened position in normal operation.
- the (minimum) flow cross-section A dp of the drain passage may correspond to a flow cross-section A pv of the pilot valve 50 when the pilot valve 50 is in its open state.
- the intermediate pressure is less than the pressure in the first cylinder chamber 37.
- the needle 20 is kept in its opened position while the pilot valve 50 remains open.
- the ejector 1 is configured such that, in this situation, the force on the piston 31 resulting from the pressure difference between the intermediate pressure in the second cylinder chamber 38 and the pressure in the first cylinder chamber 37 is sufficient to (at least substantially) overcome the resilient force of the spring 33.
- the pilot valve 50 is closed in this situation. No more fluid can be drained from the second cylinder chamber 38 to the secondary inlet chamber 8.
- the pressure in the second cylinder chamber 38 increases towards the pressure in the first cylinder chamber 37 (which may at least substantially correspond to the primary pressure).
- the resilient member 33 urges the piston 31 away from the top cover 76.
- the piston 31 start to move along the longitudinal direction L towards the needle seat 26.
- the needle 20 starts to move along the longitudinal direction L towards the needle seat 26 (i.e. towards its closed position).
- the flow cross-section A eq of the equalization passage 32 is small compared to a piston area A P of the piston 31.
- the piston area A P may correspond to at least 1000 times, e.g. to at least 1600 times, especially to at least 2100 times, the flow cross-section A eq of the equalization passage 32. This limits a movement speed of the piston 31.
- the ejector 1 may be configured such that a closing time of the needle 20 is at least 1 s in normal operation, especially at least 2 s.
- the closing time may be a time needed for the movement of the needle 20 from its opened position to its closed position in normal operation.
- the piston area A P can be in the range from 2000 mm 2 to 10000 mm 2 .
- piston 31 has a rotationally symmetric basic shape, its flow cross-section A p is ⁇ *(D p/2 ) 2 , wherein D p is a diameter of the piston 31.
- the needle 20 abuts the needle seat 26.
- the fluid connection from the primary inlet chamber 3 to the nozzle 5 (and hence from the primary inlet 2 to the nozzle 5) is blocked. No more fluid is ejected by the nozzle 5. Accordingly, no further fluid is sucked from the secondary inlet 7 into the convergent mixing portion 6.
- the pilot valve 50 is opened again. Fluid is discharged from the second cylinder chamber 38 to the secondary inlet chamber 8 and the pressure in the second cylinder chamber 38 decreases towards the intermediate pressure mentioned above. Due to the pressure drop from the first cylinder chamber 37 and the second cylinder chamber 38, the piston 31 starts to move along the longitudinal direction L such that the needle 20 is retracted from the needle seat 26 towards the opened position.
- a cross-sectional area A nsz of the needle seat 26 (a needle seat area A ns ) is only a bit larger than a (minimum) flow-cross section A noz of the nozzle 5.
- the needle seat area A nsz may be in the range from 1,005 to 1,4 times the flow-cross section A noz of the nozzle 5. This allows for the needle 20 having a small diameter.
- a flow resistance for fluid flowing from the primary inlet 2 to the nozzle 5 if the needle 20 is in its opened position is particularly low.
- the comparatively small needle seat area A nsz ensures smooth and precise beginning of the transition from the closed position of the needle 20 to its opened position.
- an increased initial force is required for starting the transition from the closed position to the opening position (i.e. from retracting the needle 20 from the closed position, particularly from abutment with the needle seat 26).
- the force needed for further retraction of the needle 20 may decline.
- the initial force depends, inter alia, on a size of a contact area between the needle 20 and the needle seat 26.
- the initial force must be provided by the actuating mechanism 30. It is beneficial that the needle seat area A nsz is as close as possible to the flow-cross section A noz of the nozzle 5. This reduces the required initial force. As a consequence, a smaller and less expensive actuating mechanism 30 can be used.
- the small needle seat area A ns reduces the risk of unintentional lift-off of the needle 20 from the needle seat 26 in the case of pressure peaks applied from the secondary inlet 7 and our the outlet 12.
- the needle seat 26 has a circle-shape, the needle seat area A nsz is the area encircled by the needle seat 26 and corresponds to ⁇ *(D ns /2) 2 , wherein D ns is a diameter of the needle seat 26.
- the flow cross-section A noz can be at least 50 mm 2 . This corresponds to a diameter of 8,0 mm if the nozzle 5 is formed rotationally symmetric.
- the flow cross-section A noz of the nozzle 5 can be in the range from 70 mm 2 to 150 mm 2 .
- an end portion of the needle 20 at the side of the needle seat 26 includes, seen along the longitudinal direction L, a needle tip 21, a first conical needle portion 22, and a second conical needle portion 24.
- a taper angle of the first conical needle portion 22 is larger than a taper angle of the second conical needle portion 24.
- an annular edge 23 is formed at the border between the first conical needle portion 22 to the second conical needle portion 24. (Only) the annular edge 23 abuts onto the needle seat 26 when the needle 20 is in its closed position.
- the needle 20 can be made of Aluminum or an aluminum alloy.
- the flow resistance of the drain passage is larger than the flow resistance of the equalization passage 32. This helps to ensure slow and controlled opening of the ejector 1.
- the flow cross-section A pv of the pilot valve 50 may be smaller than the flow cross-section A eq of the equalization passage 32. Additionally or alternatively, the flow cross-section A pv of the pilot valve 50 (in its open state) may be less than 1,8 mm 2 .
- the piston area A P of the piston 31 may be larger than a squared value of a stroke of the piston rod.
- the stroke of the piston rod is the same as the stroke S of the needle 20.
- the piston area A P may correspond to at least 8 times, especially at least 11 times, the squared value of the stroke S (A P ⁇ 8*S 2 , especially A P ⁇ 11*S 2 ).
- the axial displacement of the piston 31 by the stroke S corresponds to a large change of the volumes of the first cylinder chamber 37 and the second cylinder chamber 38. This helps to ensure slow movement of the piston 31 and hence the needle 20 during transitions between the opened position and the closed position.
- a pronounced synergistic effect can be obtained by combining this aspect with the aspect explained above, according to which the flow cross-section A eq of the equalization passage 32 may be small compared to the piston area A P of the piston 31.
- the piston area A P of the piston 31 may be large compared to the needle seat area A ns . This reduces the influence of the additional lifting force on the opening and results in smoother opening.
- the nozzle 5 is formed directly downstream of a nozzle inlet 4.
- the nozzle inlet 4 extends the longitudinal direction L and tapers towards the nozzle 5. In more detail, it may extend along the central axis C as in the figures.
- the nozzle inlet 4 is configured to guide the fluid supplied at the primary inlet 2 into the nozzle 5. More precisely, it guides the fluid supplied at the primary inlet 2 from the primary inlet chamber 3 into the nozzle 5 (when the needle 20 is in its opened position).
- the nozzle inlet 4 can be a conical nozzle inlet.
- a taper angle of the nozzle inlet 4 is smaller than the taper angle of the first conical needle portion 22 but larger than the taper angle of the second conical needle portion 24 (e.g., see Fig. 4 ).
- the needle seat 26 and the nozzle 5 are formed in the same component, namely in a nozzle insert 27.
- the nozzle insert 27 is a one-piece component. It is mounted in the insert assembly holder 78.
- the nozzle insert 27 includes the upstream nozzle inlet 4 and the nozzle 5.
- the nozzle insert 27 can be made of a material having a higher hardness than a material of the needle 20.
- the nozzle insert 27 can be made of iron.
- a length W of the nozzle inlet 4 is larger than the stroke S.
- the length of the nozzle inlet 4 may correspond to at least 1,8 times the stroke S. This ensures that the end portion of the needle 20 still protrudes into the nozzle inlet 4 even if the needle 20 is in its opened position. Accordingly, the needle 20 helps, in its opened position, to guide the fluid from the primary inlet chamber 3 smoothly into the nozzle inlet 4 and further into the nozzle 5 and to reduce turbulences.
- a distance Z between the nozzle 5 and the needle seat 26 along the longitudinal direction L (and according to a local flow direction) is small. It may be less than 0,8*(A noz / ⁇ ) 0,5 . In other words, the needle seat 26 may be formed directly upstream of the nozzle 5. This facilitates to keep the needle seat area A nsz small and to reduce the flow resistance.
- the stroke S may correspond to at least 2*(A noz / ⁇ ) 0,5 , which corresponds to the D noz if the nozzle is of rotationally symmetric shape.
- the stroke S may correspond to at least 2,8*(A noz / ⁇ ) 0,5 .
- the ejector 1 may be configured such that the flow cross-section A noz of the nozzle 5 constitutes a minimum flow cross-section between the primary inlet 2 and the convergent mixing portion 6 when the needle 20 is in its opened position.
- the needle 20 never protrudes downstream of the nozzle 5. In other words, the needle 20 never protrudes into the convergent mixing portion 6.
- the depicted embodiment of the ejector 1 provides a check valve functionality for preventing fluid flow from the outlet 12 to the secondary inlet 7.
- the ejector 1 provides a check member 80 for closing a fluid connection between the mixing portion (in more detail, the convergent mixing portion 6) and the secondary inlet chamber 8. If the ejector 1 is in its closed state, the check member 80 abuts on a check valve seat 79 and blocks fluid flow from the outlet 12 to the secondary inlet 7. If the ejector 1 is in its open state, fluid is sucked from the secondary inlet 7 through the secondary inlet chamber 3 and the secondary fluid passageway 9 into the convergent mixing portion 6. Thereby, the check member 80 is displaced along the longitudinal direction L and lifts off from the check valve seat 79.
- An annular end face of the cylinder insert 77 and a corresponding abutment area on the top cover 76 are grounded flat.
- An elastic member 90 (which is a coil spring in this embodiment) biases the cylinder insert 77 against the top cover. Hence, no significant fluid leakage or pressure propagation can occur directly from the primary inlet chamber 3 to the second cylinder chamber 38.
- the elastic member 90 is arranged in the primary inlet chamber 3 and coaxially to the needle 20. It is squeezed between the top cover 76 and the insert assembly holder 78.
- a filter 91 is provided between the primary inlet 2 and the nozzle inlet 4.
- the filter 91 is provided in the primary inlet chamber 3 around the elastic member 90, wherein the elastic member supports (backs up) the filter 91.
- the top cover 76 is removably fixed to the main sleeve 71 by screws. If the top cover 76 is detached, the cylinder insert 76 can be taken out of the main sleeve 71 for maintenance.
- the depicted embodiment is only an exemplary one and the elements can be implemented in other manners and geometries.
- the end portion of the needle 20 may be formed with another shape (e.g. convexly tapered), the needle seat 26 and the nozzle 5 can be formed two by separate elements, and the like.
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Abstract
Description
- The present invention relates to an ejector, e.g. for a refrigeration circuit with circulated refrigerant, with a primary (fluid) inlet, a secondary (fluid) inlet, a (fluid) outlet, a nozzle, and a mixing portion for mixing fluid supplied with a high pressure at the primary inlet and fluid sucked from the secondary inlet. The invention further relates to an ejector assembly with at least two ejectors.
- Typically, fluid is supplied by the refrigeration circuit with the high pressure to the primary inlet. Further, the refrigeration circuit supplies fluid to the secondary inlet with a secondary pressure that is less than the high pressure. The nozzle jets the fluid received at the primary inlet into the mixing portion. Thereby, a flow velocity is increased. Fluid received at the secondary inlet is additionally sucked into the mixing portion. As a result, the fluid received at the primary inlet mixes with the fluid received at the secondary inlet in the mixing portion. Thereafter, the combined fluid flow leaves the ejector through the outlet. A diffuser is arranged between the mixing portion and the outlet. In some applications, a flow of fluid through the nozzle can be prevented. By this, the ejector is closed.
- Examples of ejectors are known from
WO 2018/159320 A1 ,US 7,841,193 B2 ,JP 4 134 918 B2 EP 1 923 575 A2 . - Fast opening or closing of an ejector can cause fast pressure variations in the refrigeration circuit employing the ejector, e.g. pressure peaks. This can lead to damages of components of the refrigeration circuit. Furthermore, this can lead to instability in the controlling of the refrigeration system.
- One approach is to control opening and closing of the ejector with a stepper motor. However, stepper motors are particularly expensive and not perfectly suitable for all applications.
- Hence, it is an object of the invention to ensure smooth opening and closing of an ejector in a cost-effective and reliable manner.
- The problem mentioned above is solved by an ejector, e.g. for a refrigeration circuit with circulated refrigerant, according to
claim 1. - The ejector comprises:
- a primary (fluid) inlet; a secondary (fluid) inlet; and a (fluid) outlet;
- a nozzle for jetting fluid supplied at the primary inlet into a mixing portion for sucking fluid supplied at the secondary inlet into the mixing portion;
- a needle and a needle seat, wherein the needle seat is arranged downstream of the primary inlet and upstream of the nozzle (and the outlet); and
- an actuating mechanism for moving the needle between an opened position, in which the needle is lifted from the needle seat for allowing fluid flow past the needle seat, and a closed position, in which the needle abuts the needle seat and blocks fluid flow past the needle seat, wherein the actuating mechanism comprises:
- a cylinder with a piston connected to the needle, wherein a first cylinder chamber is maximized when the needle is in its opened position and a second cylinder chamber is maximized when the needle is in its closed position, wherein the first cylinder chamber is in fluid communication with the primary inlet via a chamber inlet, and wherein the second cylinder chamber is in fluid communication with the first cylinder chamber via an equalization passage, and
- a drain passage with a pilot valve, wherein the second cylinder chamber is in fluid communication with the secondary inlet and/or the outlet via the drain passage when the pilot valve is in an open state.
- The present invention ensures smooth opening and closing of the ejector. Pressure peaks due to fast opening and/or closing are reliably avoided. The implementation is cost-effective. For example, no expensive stepper motor is needed in order to ensure smooth opening and closing.
- In addition, as the needle is connected to the piston, the risk is reduced that the needle moves with excessive speed and/or flutters due to external pressure fluctuations, e.g. to fluctuations of a primary pressure applied to the primary inlet by an external refrigeration circuit.
- Fluid from the primary inlet can enter the first cylinder chamber via the chamber inlet. This allows filling up the first cylinder chamber while the (volume of) the first cylinder chamber increases.
- The drain passage is configured for discharging fluid from the second cylinder chamber when the pilot valve is open. This allows decreasing the (volume of) the second cylinder chamber (by displacement of the piston in the cylinder).
- The equalization passage allows that fluid flows from the first cylinder chamber to the second cylinder chamber. In order to bring the needle from the opened position to the closed position, the pilot valve is closed. When the pilot valve is closed, no fluid is discharged from the second cylinder chamber. The piston is displaced in order to maximize (the volume of) the second cylinder chamber. In more detail, the second cylinder chamber is filled up by the fluid from the first cylinder chamber entering the second cylinder chamber through the equalization passage while the (volume of) the second cylinder chamber increases. At the same time, the (volume) of the first cylinder chamber is decreased.
- As noted above, if the needle is in the opened position, this allows fluid flow past the needle seat. In more details, this allows that fluid flows from the primary inlet into the nozzle and further into the mixing portion. Fluid flow from the primary inlet into the nozzle is prevented when the needle is in its closed position. Correspondingly, no fluid is sucked from the secondary inlet into the mixing portion. Accordingly, the ejector is in a closed state then.
- According to one aspect, the drain passage is blocked (closed) when the solenoid valve is in a closed state.
- The chamber inlet, the equalization passage, and the drain passage may be completely integrated in the ejector. They are not constituted by fluid connections provided by an environment or any outer element. In particular, they are not constituted by any fluid connections of a refrigeration circuit employing the ejector that are not part of the ejector as such.
- According to an aspect, the actuating mechanism is for moving the needle along a longitudinal direction between the opened position and the closed position. The cylinder may extend parallel to the longitudinal axis and the piston may be configured to reciprocate parallel to the longitudinal axis in the cylinder for either maximizing (the volume of) the first cylinder chamber (such that the needle is in the opened position) or maximizing (the volume of) the second cylinder chamber (such that the needle is in the closed position).
- The longitudinal direction may be parallel to a central axis. The cylinder, the piston, the needle, the needle seat, the nozzle, and/or the mixing portion may extend at least substantially along the central axis. A diffuser portion may be formed downstream of the mixing portion. The diffuser portion may extend along the central axis. In one embodiment, the (whole) ejector extends substantially along the central axis.
- A piston area is a cross-section area of the piston. The piston area may be defined within a plane perpendicular to the longitudinal direction.
- In one embodiment, the piston area is at least 1000 times a flow cross-section of the equalization passage. Especially, the piston area may be at least 1600 times the flow cross-section of the equalization passage.
- If the piston area is increased, a displacement of the piston by a certain distance corresponds to larger volume change of the second cylinder chamber. This helps to limit the piston's velocity.
- During the transition from the opened position to the closed position of the needle, fluid flows from the first cylinder chamber through the equalization passage to the second cylinder chamber. For given circumstances, the flow cross-section of the equalization passage limits, by its flow resistance, a flow rate (e.g. measured in ml/s) between the first cylinder chamber to the second cylinder chamber. The total volume change of the second cylinder chamber during opening increases with increasing piston diameter. By increasing the piston area while the flow cross-section of the equalization passage and the stroke of the piston remain the same, a closing time is extended. The piston's velocity during opening is slower. In more detail, the piston's velocity reaches a substantially constant value shortly after transition from the opened position to the closed position has started. This value may be related to the flow rate divided by the piston area.
- Additionally or alternatively, the piston area may be at least 1200 times a flow cross-section of the drain passage, especially at least 1920 times.
- For given circumstances, the flow cross-section of the drain passage limits a fluid discharge rate (e.g. measured in ml/s), with which fluid can be discharged from the second cylinder chamber via the drain passage when the pilot valve is open. During transition from the closed position to the opened position, a net flow rate for the second cylinder chamber may be (at least substantially) determined by the fluid discharge rate and the flow rate of fluid entering through the equalization passage. The piston's velocity may reach a substantially constant value shortly after transition from the closed position to the second position has started. This value may be related to the net flow rate divided by the piston area. If the piston area and hence the total volume change of the second cylinder chamber required for opening are increased, the opening time is extended.
- Naturally, if the piston area increases with respect to the flow cross-section of the equalization passage while the flow cross-section of the drain passage remains the same, the piston area increases with respect to the drain passage as well. Vice versa, if the piston area increases with respect to the flow cross-section of the drain passage while the flow cross-section of the equalization passage remains the same, the piston area increases with respect to the equalization passage as well.
- According to one aspect, a needle seat area, which is a cross-section area of the needle seat where the needle engages the needle seat in the closed position, is in the range from 1,005 to 1,4 times a flow cross-section of the nozzle. The cross-section area of the needle seat is particularly small. Accordingly, the effects of pressure changes at a needle tip when then the needle is arriving at the needle seat and starting to lift off from the needle seat are minimized. This facilitates smooth and controlled opening and closing of the ejector.
- According to a further aspect, the ejector may comprise a housing. This ensures protection of the components inside the housing.
- The housing may include a main sleeve. An interior of the main sleeve may extend along the central axis. The housing may further include a top cover. The top cover can be fixed to an end of the main sleeve in the longitudinal direction at a side opposite to the outlet. The top cover may be removably fixed to the main sleeve. This facilitates maintenance.
- According to another aspect, the pilot valve is a solenoid valve. Solenoid valves are particularly inexpensive, reliable, and easy to control. It is not necessary to control an exact opening degree of the pilot valve. The present invention ensures smooth opening and closing also in the case that the pilot valve can be switched only between an open state and a closed state. No additional intermediate states of the pilot valve are needed in order to keep the movement speed of the needle below a pre-determined threshold.
- In one embodiment, the piston area corresponds to at least 20 times the needle seat area. Hence, the effects of pressure changes when then the needle is arriving at the needle seat and starting to lift off from the needle seat can be at least substantially neglected compared to the effects of the fluid flows into and out of the first cylinder chamber and the second cylinder chamber.
- According to one aspect, a stroke of the needle between the closed position and the opened position correspond to at least 2*(Anoz/π)0,5, where Anoz is the flow cross-section of the nozzle. When the needle is in its opened position, it is sufficiently retracted to ensure low flow resistance against fluid flow from the primary inlet to the nozzle. This is beneficial for efficiency.
- According to another aspect, the ejector comprises a check valve function for preventing fluid flow from the outlet to the secondary inlet. Hence, elements of a refrigeration circuit employing the ejector cannot be damaged by such a back flow.
- The first cylinder chamber may be a piston-rod side cylinder chamber. The second cylinder chamber me be the cylinder chamber in the same cylinder at the other side of the piston.
- According to one aspect, the needle may be formed integrally with the piston. The needle may be a piston rod at the same time. This is a particularly reliable, cost-effective, and lightweight implementation. It may include at least one hole extending thorough the piston.
- In one embodiment, the equalization passage is formed (completely) in the piston. This allows fast and cost-efficient production.
- According to another aspect, the flow cross-section of the equalization passage may be in the range from 1,2 to 2,5 times the flow cross-section of the drain passage when the pilot valve is in its open state. This ensure that a flow resistance of the drain passage is higher than a flow resistance of the equalization passage. Only a slight pressure drop from the first cylinder chamber to the second cylinder portion occurs even during the needle's transition from the closed position to the opened position. The movement velocity of the piston and the needle can be precisely controlled and kept low. This further facilitates smooth opening of the ejector.
- The flow cross-section of the drain passage can be determined by the flow cross-section of the pilot valve. The pilot valve can be designed to be as small as possible. This reduces the costs. Accordingly, the flow cross-section of the equalization passage may be in the range from 1,2 to 2,5 times a flow cross-section of the pilot valve when the pilot valve is in its open state.
- In one embodiment, a flow cross-section of the chamber inlet is larger than the flow cross-section of the equalization passage. For example, the flow cross-section of the chamber inlet may be at least 5 times, especially at least 10 times, the flow cross-section of the equalization passage. The amount of fluid leaving the first cylinder chamber through the equalization passage, especially if the pilot valve is open, can be easily replaced. This ensures that the pressure in first cylinder chamber is at least substantially maintained when the pilot valve is open and even during the transition from the closed state to the open state, i.e. while the (volume of) the first cylinder chamber is increasing.
- According to one aspect, the needle seat is at least axially fixed with respect to the housing. This facilitates precise opening and closing of the ejector.
- The nozzle may be arranged in an interior of the housing. It may be at least axially fixed with respect to the housing. The nozzle may comprise a throat portion and a divergent nozzle portion. The throat portion may define the flow cross-section of the nozzle. The divergent nozzle portion may be arranged downstream of the throat portion. It may be of a conical shape, wherein an inner diameter increases towards a downstream end of the nozzle. The downstream end of the nozzle may protrude towards the mixing portion.
- In one embodiment, a nozzle inlet is formed directly upstream of the nozzle, wherein the nozzle inlet tapers toward the nozzle, wherein the needle seat is located in the nozzle inlet, and wherein a length of the nozzle inlet may correspond to at least 1,8 times the stroke of the needle between the closed position and the opened position. This ensures proper flow from the fluid supplied at the primary inlet into the nozzle and hence low flow resistance when the ejector is in the open state.
- The nozzle inlet and the nozzle can be formed in a one-piece component, e.g. in a nozzle insert. The nozzle insert may be mounted to an insert assembly holder that is mounted in the housing, e.g. in an interior of the main sleeve. The nozzle insert may be fixed to the housing. However, it may be removably fixed to the housing in order to facilitate maintenance.
- According to one aspect, the ejector can comprise a resilient member acting against minimizing (the volume of) the second cylinder chamber by the piston. For example, the resilient member urges the piston towards maximizing (the volume of) the second cylinder chamber. In other words, the resilient member may urge the needle towards its closed position. The resilient member may engage directly with the piston and/or directly with the needle. For example, the resilient member may be provided between an end wall of the cylinder at the side of the second cylinder chamber and the piston. The resilient member facilitates the transition of the needle from its opened position to its closed position. The resilient member may include a coil spring.
- In one embodiment, the ejector is configured such that the opening time of the needle is at least 0,5 s, e.g. at least 1 s. The long opening time prevents fast pressure variations and hence reduces a risk of damages in a refrigeration circuit employing the ejector.
- Additionally or alternatively, the ejector is configured such that the closing time of the needle is at least 1 s, e.g. at least 2 s. The long closing time prevents fast pressure variations and hence reduces a risk of damages in a refrigeration circuit employing the ejector.
- In one embodiment, the ejector is configured such that the needle moves, during the transition from its closed position to its opened position (in normal operation), with a substantially constant velocity over a displacement length corresponding to at least 70 % of the stroke. This ensures controlled and smooth opening and reduces the risk of damages in any refrigeration circuit employing the ejector.
- Additionally or alternatively, the ejector is configured such that the needle moves, during the transition from its opened position to its closed position (in normal operation), with a substantially constant velocity over a displacement length corresponding to at least 70 % of the stroke. This ensures controlled and smooth closing and reduces the risk of damages in any refrigeration circuit employing the ejector.
- Substantially constant velocity may mean that the velocity changes by 15 % at the maximum during the respective movement phase.
- According to another aspect, the flow cross-section of the nozzle is at least 50 mm2. Hence, the ejector exhibits a high capacity.
- In one embodiment, the cylinder is formed by a cylinder insert and the top cover. The cylinder insert may be inserted in an interior of the main sleeve. The cylinder insert may be removably mounted in the main sleeve. This facilitates maintenance.
- According to another aspect, the ejector may comprise an elastic member, for example a spring, especially a coil spring.
- The elastic member may bias the cylinder insert against the top cover. The second cylinder chamber may be arranged at the side of the top cover. This ensures proper sealing between those elements. This ensures that the pressure propagation to the second cylinder chamber is determined by the pressure propagation from the first cylinder chamber to the second cylinder chamber via the equalization passage. A risk of substantial leakage and pressure propagation from the primary inlet to the second cylinder chamber that bypasses the equalization passage is reduced. An annular end face of the cylinder insert for abutting on the top cover may be ground flat.
- The elastic member may be squeezed between the cylinder insert and a member that is at least axially fixed with respect to the housing. For example, the elastic member may be squeezed between the cylinder insert and the insert assembly holder.
- In one embodiment, the ejector comprises a filter between the primary fluid inlet and the needle seat. The filter may be arranged circumferentially about the needle and the needle seat. It may be supported by the elastic member.
- According to another aspect, the needle is made of a first material and the needle seat is made of a second material, wherein a hardness of the second material is higher than a hardness of the first material. For example, the hardness of the second material may correspond to at least 1,4 times the hardness of the second material. In one embodiment, the nozzle insert (which includes the needle seat) is made of the second material.
- The problem mentioned above is further solved by an ejector assembly comprising at least two ejectors according to any one of the described embodiments and modifications.
- The ejectors may be arranged in parallel.
- In one embodiment, a flow cross-section of a second one of the at least two ejectors is different from a flow cross-section of a first one of the at least two ejectors. For example, the flow cross-section of the second one can be at least 1,2 times the flow cross-section of the first one. By closing both the first one and the second one, opening only the first one, opening only the second one, or opening both the first one and the second one, four different flow rates can be set.
- If it is referred to a flow cross-section of an element (like a passage, a channel, or the like, e.g. the nozzle), this may mean a minimum cross-section of the respective element along an intended flow direction through the element.
- Additional features, advantages and possible applications of the invention result from the following description of exemplary embodiments and the drawings. All the features described and/or illustrated graphically here form the subject matter of the invention, either alone or in any desired combination, regardless of how they are combined in the claims or in their references back to preceding claims.
- Fig. 1
- shows an embodiment of an ejector according to the present invention in an open state in a cross-sectional view on a plane extending along a central axis of the ejector;
- Fig. 2
- is an enlarged upper section of
Fig. 1 ; - Fig. 3
- shows the upper part of the ejector of
Fig. 2 in a cross-sectional view on a plane, which extends along the central axis of the ejector as well but is perpendicular to the plane shown inFig. 1 andFig. 2 ; and - Fig. 4
- shows an enlarged section of
Fig. 1 around a needle seat and a nozzle. - An embodiment of an
ejector 1 according to the present invention is shown inFig. 1 . Theejector 1 comprises a primary (fluid)inlet 2, a secondary (fluid)inlet 7, and an (fluid)outlet 12. Theprimary inlet 2 may be also referred to ashigh pressure inlet 2. Theejector 1 extends along a central axis C. A longitudinal direction L is parallel to the central axis C. - If the
ejector 1 is in an open state as shown inFigs. 1 to 4 , fluid can flow from thefirst inlet 2 through anozzle 5, a mixing portion (which includes aconvergent mixing portion 6 and a cylindrical mixing portion 10), and adiffuser portion 11 to thefluid outlet 12. In addition, fluid is drawn from thesecondary inlet 7 into the mixingportion 6. In other words, the fluid drawn from thesecondary inlet 7 joins the fluid from theprimary inlet 2 in theconvergent mixing portion 6. This results in mixing of the fluid from theprimary inlet 2 and the fluid drawn from thesecondary inlet 7 in theconvergent mixing portion 6 and thecylindrical mixing portion 10 that follows downstream of theconvergent mixing portion 6. - The
ejector 1 includes a needle valve mechanism with aneedle 20 and aneedle seat 26. - If the
needle 20 is in a closed position (not shown), it abuts theneedle seat 26 and blocks the fluid connection between theprimary inlet 1 and thenozzle 5. This prevents that fluid from theprimary inlet 1 can enter into thenozzle 5 and flow further into theconvergent mixing portion 6. This corresponds to a closed state ofejector 1. - If the
needle 20 is in an opened position as shown inFigs. 1 to 4 , theneedle 20 is lifted from theneedle seat 26 by a needle stroke S (seeFig. 4 ). This allows fluid flow from theprimary inlet 2 into thenozzle 5. The stroke S is the displacement of theneedle 20 along the longitudinal direction L between its opened position and its closed position. The stroke S may be at least 10 mm, for example in the range from 12 mm to 30 mm. - In this exemplary embodiment, a
housing 70 of theejector 1 includes amain sleeve 71, an upstream-side top cover 76, afirst diffuser tube 74, and asecond diffuser tube 75. Thefirst diffuser tube 74 and thesecond diffuser tube 75 form at least a downstream part of thediffuser portion 11. Thehousing 70 further includes a primary (fluid)inlet connector 72, which is fixed to themain sleeve 71 and forms theprimary inlet 2, and a secondary (fluid)inlet connector 73, which is fixed to themain sleeve 71 and forms thesecondary inlet 7. - The
ejector 1 further comprises anactuating mechanism 30 for moving theneedle 20 along the longitudinal direction L between the opened position and the closed position. - The
actuating mechanism 30 comprises apilot valve 50 and apiston 31. Thepiston 31 is arranged in acylinder 35 and can be axially displaced within the cylinder 35 (i.e. along the central axis C). Theneedle 20 is mechanically connected to thepiston 31 such that the axial movement of thepiston 31 in thecylinder 35 is transferred to movement of theneedle 20 along the longitudinal direction L. Accordingly, theneedle 20 can be moved from its opened position to its closed position and vice versa by corresponding axial movements of thepiston 31. In this embodiment, theneedle 20, thepiston 31, and thecylinder 35 are all arranged coaxially along the central axis C and theneedle 20 is at least axially fixed to thepiston 31. In more detail, theneedle 20 and thepiston 31 can be formed integrally (in one piece) as shown inFigs. 1 to 3 . In other words, the needle 20 (in particular a needle stem 25) also constitutes a piston rod for thepiston 31. - The
cylinder 35 can be formed by acylinder insert 77 and thetop cover 76 as shown inFigs. 1 to 3 . Thecylinder insert 77 is arranged in an interior of themain sleeve 71 and directly abuts thetop cover 76. Thecylinder insert 77 guides thepiston 31 and its piston rod (which is theneedle 20 in this embodiment). - The
piston 31 is configured to form afirst cylinder chamber 37 and asecond cylinder chamber 38 within thecylinder 35. It can divide an interior of thecylinder 35 into thefirst cylinder chamber 37 and the second cylinder chamber 38 (along the longitudinal direction L). - A volume of the
first cylinder chamber 37 is maximized (maximal) when theneedle 20 is in its opened position. It is minimized when theneedle 20 is in its closed position. It may decrease (at least substantially) to a minimum volume (small residual volume) when theneedle 20 is in its closed position (not shown, corresponds to a lowermost possible position of thepiston 31 inFigs. 1 to 3 ). - A volume of the
second cylinder chamber 38 is maximized (maximal) if theneedle 20 is in its closed position. It is minimized when theneedle 20 is in its opened position (correspond to an uppermost possible position of thepiston 31 as shown inFigs. 1 to 3 ). It may decrease (at least substantially) to zero when theneedle 20 is in its opened position. However, in the exemplary embodiment, anannular end wall 40, which is provided on a surface of thepiston 31 facing thesecond cylinder chamber 38, causes that a residual volume of thesecond cylinder chamber 38 remains even if theneedle 20 is in its opened position. This ensures that theequalization passage 32 is not closed when theneedle 20 is in the opened position. - At a side of the
cylinder insert 77 in the longitudinal direction L that faces away from thetop cover 76, a primary (fluid)inlet chamber 3 is formed. Theprimary inlet connector 72 opens into theprimary inlet chamber 3. - The
first cylinder chamber 37 is in fluid communication with theprimary inlet 2 via achamber inlet 36. In this embodiment, thechamber inlet 36 is a fluid connection provided between theprimary inlet chamber 3 and an end of thecylinder 35 in the longitudinal direction L at the side of the needle 20 (an end of thecylinder 35 at the side of thefirst cylinder chamber 37, i.e. a lower end of thecylinder 35 inFigs. 1 to 3 ). Thechamber inlet 36 may be formed in thecylinder insert 77, for example as at least one bore extending along the longitudinal direction L. In the embodiment shown inFigs. 1 and2 , four or six of such bores are formed in thecylinder insert 77. Two of them can be seen inFigs. 1 and2 . - Further, the other end of the
cylinder 35 in the longitudinal direction L (an end of thecylinder 35 at the side of thesecond cylinder chamber 38, i.e. an upper end of thecylinder 35 inFigs. 1 to 3 ) is in fluid communication with thesecondary inlet 7 via a drain passage. Thepilot valve 50 is arranged in the drain passage. When thepilot valve 50 is in its closed state, it blocks (closes) the drain passage. When thepilot valve 50 is in its open state, the drain passage is open and thesecond cylinder chamber 38 is in fluid communication with thesecondary inlet 7. In other words, the drain passage is formed between thesecond cylinder chamber 38 on the one hand and, on the other hand, thesecondary inlet 7 and/or a space that is in (direct) fluid communication with thesecondary inlet 7. In this embodiment, the drain passage is formed between thesecond cylinder chamber 38 and a secondary (fluid)inlet chamber 8, which is in direct fluid communication with thesecondary inlet 7. - In a modification (not shown), the
second cylinder chamber 38 is in fluid communication with theoutlet 12 via the drain passage when thepilot valve 50 is in an open state. In other words, the drain passage with thesolenoid valve 50 is formed between thesecond cylinder chamber 38 and thefluid outlet 12 and/or a space that is in fluid communication with thefluid outlet 12 in this case. Of course, it is also possible to provide a drain passage with two branches, one branch for fluid communication of thesecond cylinder chamber 38 with thesecondary inlet 7 and another branch for fluid communication of thesecond cylinder chamber 38 with thefluid outlet 12. A blocking means, e.g. a check valve, can be employed to prevent fluid flow from thesecondary inlet 7 to thefluid outlet 12 via the drain passage. - As shown in
Fig. 1 , the drain passage may be formed completely within theejector 1. It is integrated in theejector 1 as such. - Turning now to
Fig. 3 , the drain passage includes afluid connection 39 between the upper end of the cylinder 35 (the second cylinder chamber 38) and an upstream side of thepilot valve 50. Saidfluid connection 39 may be also referred to as thechamber outlet 39. As can be seen inFig. 3 , thechamber outlet 39 may be formed by at least one channel, for example two channels, within thetop cover 76. - Further, a downstream side of the
pilot valve 50 is in fluid communication with thesecondary inlet 7. This can be seen inFigs. 1 and2 , where the plane of the depicted cross-section is perpendicular to the one shown inFig. 3 . In the present embodiment, the drain passage includes afirst fluid passage 54 formed in thetop cover 76, asecond fluid passage 55 that is also formed in thetop cover 76, afluid passage 56 formed in themain sleeve 71, and afluid passage 57 formed between themain sleeve 71 and aninsert assembly holder 78. Thefluid passage 57 is a substantially annular gap between themain sleeve 71 and theinsert assembly holder 78. The drain passage opens into thesecondary inlet chamber 8. Thesecondary inlet connector 73 also opens into thesecondary inlet chamber 8. Hence, the downstream side of thepilot valve 50 is in fluid communication with thesecondary inlet 7, and thesecond cylinder chamber 38 is in fluid communication with thesecondary inlet 7 when thepilot valve 50 is in its open state. - In addition, the
second cylinder chamber 38 is in fluid communication with thefirst cylinder chamber 37. The fluid communication is provided by anequalization passage 32. In this embodiment, theequalization passage 32 includes longitudinal bore through thepiston 31. Theequalization passage 32 may be formed completely within theejector 1. It is integrated in theejector 1 as such. - The
pilot valve 50 includes avalve seat 51, avalve member 52, and an actuator 53. The actuator 53 is configured to switch thepilot valve 50 between an open state and a closed state thereof. In this embodiment, thepilot valve 50 is a solenoid valve. Hence, the actuator 53 is a solenoid actuator. Thepilot valve 50 is a part of theejector 1. In particular, thevalve seat 51 may be integrally formed with thehousing 70 or an insert fixed to the housing. In the exemplary embodiment, thevalve seat 51 is mounted within thetop cover 76. - In the following, the operation will be described. It is assumed that the
needle 20 is in its opened position and that thepilot valve 50 is in its open state at the beginning. In other words, theejector 1 is in its open state at the beginning. - In normal operation, fluid is supplied at the
primary inlet 2 with a high primary pressure. Consequently, high-pressure fluid from theprimary inlet 2 flows through thechamber inlet 36 into thefirst cylinder chamber 37. A (minimum) flow cross-section Apci of thechamber inlet 36 is larger than a (minimum) flow cross-section Aeq of theequalization passage 32. For example, the flow cross-section Apci of thechamber inlet 36 may be at least 5 times, especially at least 10 times, the flow cross-section Aeq of theequalization passage 32. In the exemplary embodiment shown inFig. 1 , the flow cross-section Apci of thechamber inlet 36 is the sum of the cross-sectional areas of the bores constituting thechamber inlet 36, which are formed in thecylinder insert 77. - Due to the
chamber inlet 36, the fluid pressure in thefirst cylinder chamber 37 at least substantially corresponds to the primary pressure at theprimary inlet 2. The fluid pressure in thefirst cylinder chamber 37 forces the piston 31 (along the longitudinal direction L) towards thetop cover 76 and hence theneedle 20 towards its opened position, against a resilient force provided by aresilient member 33. In the depicted embodiment, theresilient member 33 is a coil spring. - In normal operation, fluid is supplied at the
secondary inlet 7 with a secondary pressure. The secondary pressure is less than the primary pressure at theprimary inlet 2 but higher than an outlet pressure at thefluid outlet 12. In other words, there is a pressure drop from the primary pressure to the secondary pressure. - This pressure drop is used for jetting the fluid from the
primary inlet chamber 3 through thenozzle 5 into theconvergent mixing portion 6 when theneedle 20 is in its opened position. The fluid jetted out of thenozzle 5 has a high velocity. The ejection through thenozzle 5 results in a pressure drop from theprimary inlet chamber 3 to theconvergent mixing portion 6. Further, when theneedle 20 is in its opened position such that fluid from provided at theprimary inlet 2 is jetted out of thenozzle 5, fluid provided at thesecondary inlet 7 is sucked from thesecondary inlet chamber 8 through a secondary fluid passageway 9 into theconvergent mixing portion 6. The fluid from theprimary inlet 2, which is ejected by thenozzle 5, and the fluid sucked from thesecondary inlet chamber 8 mix in theconvergent mixing portion 6 and thecylindrical mixing portion 10. - As noted above, it is assumed that the
pilot valve 50 is in its open state at the beginning. A small fluid flow from thefirst cylinder chamber 37 to thesecond cylinder chamber 38 via theequalization passage 32 occurs. Furthermore, fluid flows from thesecond cylinder chamber 38 to thesecondary inlet chamber 8 via the drain passage because thepilot valve 50 is in its open state. Hence, there is a small pressure drop from thefirst cylinder chamber 37 to thesecond cylinder chamber 38 which is sufficient for keeping theneedle 20 in the opened position. The pressure drop is sufficiently high for holding thepiston 31 in abutment with thetop cover 76 against the restoring force of theresilient element 33. - The flow cross-section Aeq of the
equalization passage 32 is comparatively small. It may be less than 10 mm2, e.g. in the range from 0,5 mm2 to 4 mm2. Additionally or alternatively, a value corresponding to the square of a length Leq of the equalization passage 32 (along a flow direction therethrough) may be at least 15 times, for example at least 25 times, the flow cross-section Aeq of the equalization passage 32 (Leq 2 ≥ 15*Aeq). Theequalization passage 32 exhibits considerable flow resistance. - If the
equalization passage 32 has a cylindrical shape, its flow cross-section Aeq is π*(Deq/2)2, wherein Deq is a diameter of theequalization passage 32. - In general, the flow cross-section Aeq of the
equalization passage 32 can be larger or the same as a (minimum) flow cross-section Adp of the drain passage (when thepilot valve 50 is in its open state). - When the
ejector 1 is in the open state, an intermediate pressure occurs in thesecond cylinder chamber 38. The intermediate pressure is lower than the pressure in the first cylinder chamber 37 (which may at least substantially correspond to the primary pressure). The intermediate pressure is larger than the secondary pressure. The exact value of the intermediate pressure depends, inter alia, on the flow resistance and hence on the flow cross-section Aeq of theequalization passage 32 as well as on a flow resistance and hence on the flow cross-section Adp of the drain passage and on a ratio Aeq/Adp. - If the flow cross-section Aeq of the
equalization passage 32 is considerably smaller than the flow cross-section Adp of the drain passage (Aeq/Adp << 1), the flow resistance of the drain passage is considerably smaller than the flow resistance of theequalization passage 32. When thepilot valve 50 is open, fluid can be discharged from thesecond cylinder chamber 38 into thesecondary inlet chamber 8 through the drain passage in an almost unobstructed manner. The intermediate pressure in thesecond cylinder chamber 38 will become almost as low as the secondary pressure if thepilot valve 50 is in its open state. - However, according to one aspect of the present disclosure, the flow cross-section Aeq of the
equalization passage 32 may be larger than the flow cross-section Adp of the drain passage (Aeq/Adp > 1). Especially, the flow cross-section Aeq of theequalization passage 32 may be in the range from 1,2 to 2,5 times the flow cross-section Adp of the drain passage (1,2* Adp ≤ Aeq ≤ 2,5* Adp). The flow resistance of theequalization passage 32 is smaller than the flow resistance of the drain passage. However, the pressure-drop fromfirst cylinder chamber 37 to thesecond cylinder chamber 38 is smaller in that case. Nevertheless, the intermediate pressure in thesecond cylinder chamber 38 is less than pressure in thefirst cylinder chamber 37 when thepilot valve 50 is in its open state. In other words, there is nevertheless the small pressure drop. The small pressure drop remains due to the flow resistance exhibited by theequalization passage 32 and due to ongoing discharge of fluid out of thesecond cylinder chamber 38. For example, theejector 1 may be configured such that a pressure drop from thefirst cylinder chamber 37 to the second cylinder chamber 38 (i.e. a pressure drop along the equalization passage 32) is less than 10 bar, especially less than 3 bar, in normal operation if thepilot valve 50 after thepilot valve 50 is open for at least 0,2 s. This ensures a smooth transition from the closed position of theneedle 20 to its opened position (and hence a smooth transition from the closed state of theejector 1 to the open state of the ejector 1) even if the actuating mechanism is controlled by a solenoid valve. - Accordingly, the
ejector 1 may be configured such that an opening time of theneedle 20 is at least 0,5 s in normal operation, especially at least 1 s. The opening time may be a time needed for the movement of theneedle 20 from its closed position to its opened position in normal operation. - The (minimum) flow cross-section Adp of the drain passage may correspond to a flow cross-section Apv of the
pilot valve 50 when thepilot valve 50 is in its open state. - Starting from the situation that the
needle 20 is in its opened position and that thepilot valve 50 is open, as long as thepilot valve 50 remains opened, the intermediate pressure is less than the pressure in thefirst cylinder chamber 37. Theneedle 20 is kept in its opened position while thepilot valve 50 remains open. Theejector 1 is configured such that, in this situation, the force on thepiston 31 resulting from the pressure difference between the intermediate pressure in thesecond cylinder chamber 38 and the pressure in thefirst cylinder chamber 37 is sufficient to (at least substantially) overcome the resilient force of thespring 33. - Now it is assumed that the
pilot valve 50 is closed in this situation. No more fluid can be drained from thesecond cylinder chamber 38 to thesecondary inlet chamber 8. As theequalization passage 32 remains open, the pressure in thesecond cylinder chamber 38 increases towards the pressure in the first cylinder chamber 37 (which may at least substantially correspond to the primary pressure). In addition, theresilient member 33 urges thepiston 31 away from thetop cover 76. Thepiston 31 start to move along the longitudinal direction L towards theneedle seat 26. Accordingly, theneedle 20 starts to move along the longitudinal direction L towards the needle seat 26 (i.e. towards its closed position). - The flow cross-section Aeq of the
equalization passage 32 is small compared to a piston area AP of thepiston 31. The piston area AP may correspond to at least 1000 times, e.g. to at least 1600 times, especially to at least 2100 times, the flow cross-section Aeq of theequalization passage 32. This limits a movement speed of thepiston 31. - This ensures a smooth transition from the opened position of the
needle 20 to its closed position (and hence a smooth transition from the open state of theejector 1 to the closed state of the ejector 1) even if the actuating mechanism is controlled by a solenoid valve that can only be switched between the open state and the close state and does not provide a possibility to adjust any opening degree in-between. - The
ejector 1 may be configured such that a closing time of theneedle 20 is at least 1 s in normal operation, especially at least 2 s. The closing time may be a time needed for the movement of theneedle 20 from its opened position to its closed position in normal operation. - For example, the piston area AP can be in the range from 2000 mm2 to 10000 mm2.
- If the
piston 31 has a rotationally symmetric basic shape, its flow cross-section Ap is π*(Dp/2)2, wherein Dp is a diameter of thepiston 31. - At the end of the transition from the open state of the
ejector 1 to its closed state, theneedle 20 abuts theneedle seat 26. The fluid connection from theprimary inlet chamber 3 to the nozzle 5 (and hence from theprimary inlet 2 to the nozzle 5) is blocked. No more fluid is ejected by thenozzle 5. Accordingly, no further fluid is sucked from thesecondary inlet 7 into theconvergent mixing portion 6. - In order to bring the
ejector 1 from its closed state to its open state again, thepilot valve 50 is opened again. Fluid is discharged from thesecond cylinder chamber 38 to thesecondary inlet chamber 8 and the pressure in thesecond cylinder chamber 38 decreases towards the intermediate pressure mentioned above. Due to the pressure drop from thefirst cylinder chamber 37 and thesecond cylinder chamber 38, thepiston 31 starts to move along the longitudinal direction L such that theneedle 20 is retracted from theneedle seat 26 towards the opened position. - A cross-sectional area Ansz of the needle seat 26 (a needle seat area Ans) is only a bit larger than a (minimum) flow-cross section Anoz of the
nozzle 5. In particular, the needle seat area Ansz may be in the range from 1,005 to 1,4 times the flow-cross section Anoz of thenozzle 5. This allows for theneedle 20 having a small diameter. Hence, a flow resistance for fluid flowing from theprimary inlet 2 to thenozzle 5 if theneedle 20 is in its opened position is particularly low. Furthermore, the comparatively small needle seat area Ansz ensures smooth and precise beginning of the transition from the closed position of theneedle 20 to its opened position. - Typically, an increased initial force is required for starting the transition from the closed position to the opening position (i.e. from retracting the
needle 20 from the closed position, particularly from abutment with the needle seat 26). The force needed for further retraction of theneedle 20 may decline. The initial force depends, inter alia, on a size of a contact area between theneedle 20 and theneedle seat 26. The initial force must be provided by theactuating mechanism 30. It is beneficial that the needle seat area Ansz is as close as possible to the flow-cross section Anoz of thenozzle 5. This reduces the required initial force. As a consequence, a smaller and lessexpensive actuating mechanism 30 can be used. - Furthermore, the small needle seat area Ans reduces the risk of unintentional lift-off of the
needle 20 from theneedle seat 26 in the case of pressure peaks applied from thesecondary inlet 7 and our theoutlet 12. - If the
nozzle 5 is formed rotationally symmetric, its flow cross-section Anoz is π*(Dnoz/2)2, wherein Dnoz is a minimum inner diameter of thenozzle 5. If theneedle seat 26 has a circle-shape, the needle seat area Ansz is the area encircled by theneedle seat 26 and corresponds to π*(Dns/2)2, wherein Dns is a diameter of theneedle seat 26. - The flow cross-section Anoz can be at least 50 mm2. This corresponds to a diameter of 8,0 mm if the
nozzle 5 is formed rotationally symmetric. For example, the flow cross-section Anoz of thenozzle 5 can be in the range from 70 mm2 to 150 mm2. -
Fig. 4 shows that, in this exemplary embodiment, an end portion of theneedle 20 at the side of theneedle seat 26 includes, seen along the longitudinal direction L, aneedle tip 21, a firstconical needle portion 22, and a secondconical needle portion 24. A taper angle of the firstconical needle portion 22 is larger than a taper angle of the secondconical needle portion 24. Hence, an annular edge 23 is formed at the border between the firstconical needle portion 22 to the secondconical needle portion 24. (Only) the annular edge 23 abuts onto theneedle seat 26 when theneedle 20 is in its closed position. - The
needle 20 can be made of Aluminum or an aluminum alloy. - In the depicted embodiment, the flow resistance of the drain passage is larger than the flow resistance of the
equalization passage 32. This helps to ensure slow and controlled opening of theejector 1. Especially, the flow cross-section Apv of thepilot valve 50 may be smaller than the flow cross-section Aeq of theequalization passage 32. Additionally or alternatively, the flow cross-section Apv of the pilot valve 50 (in its open state) may be less than 1,8 mm2. - The piston area AP of the
piston 31 may be larger than a squared value of a stroke of the piston rod. In this example, the stroke of the piston rod is the same as the stroke S of theneedle 20. For example, the piston area AP may correspond to at least 8 times, especially at least 11 times, the squared value of the stroke S (AP ≥ 8*S2, especially AP ≥ 11*S2). Hence, the axial displacement of thepiston 31 by the stroke S corresponds to a large change of the volumes of thefirst cylinder chamber 37 and thesecond cylinder chamber 38. This helps to ensure slow movement of thepiston 31 and hence theneedle 20 during transitions between the opened position and the closed position. Moreover, a pronounced synergistic effect can be obtained by combining this aspect with the aspect explained above, according to which the flow cross-section Aeq of theequalization passage 32 may be small compared to the piston area AP of thepiston 31. - Additionally or alternatively, the piston area AP of the
piston 31 may be large compared to the needle seat area Ans. This reduces the influence of the additional lifting force on the opening and results in smoother opening. - The
nozzle 5 is formed directly downstream of anozzle inlet 4. Thenozzle inlet 4 extends the longitudinal direction L and tapers towards thenozzle 5. In more detail, it may extend along the central axis C as in the figures. - An annular, line-shaped portion of the
nozzle inlet 4, onto which the annular edge 23 abuts when theneedle 20 is in its closed position, constitutes theneedle seat 26. - The
nozzle inlet 4 is configured to guide the fluid supplied at theprimary inlet 2 into thenozzle 5. More precisely, it guides the fluid supplied at theprimary inlet 2 from theprimary inlet chamber 3 into the nozzle 5 (when theneedle 20 is in its opened position). - The
nozzle inlet 4 can be a conical nozzle inlet. A taper angle of thenozzle inlet 4 is smaller than the taper angle of the firstconical needle portion 22 but larger than the taper angle of the second conical needle portion 24 (e.g., seeFig. 4 ). - In this exemplary embodiment, the
needle seat 26 and thenozzle 5 are formed in the same component, namely in anozzle insert 27. Thenozzle insert 27 is a one-piece component. It is mounted in theinsert assembly holder 78. Thenozzle insert 27 includes theupstream nozzle inlet 4 and thenozzle 5. Thenozzle insert 27 can be made of a material having a higher hardness than a material of theneedle 20. - For example, the
nozzle insert 27 can be made of iron. - According to another aspect, a length W of the
nozzle inlet 4 is larger than the stroke S. For example, the length of thenozzle inlet 4 may correspond to at least 1,8 times the stroke S. This ensures that the end portion of theneedle 20 still protrudes into thenozzle inlet 4 even if theneedle 20 is in its opened position. Accordingly, theneedle 20 helps, in its opened position, to guide the fluid from theprimary inlet chamber 3 smoothly into thenozzle inlet 4 and further into thenozzle 5 and to reduce turbulences. - A distance Z between the
nozzle 5 and theneedle seat 26 along the longitudinal direction L (and according to a local flow direction) is small. It may be less than 0,8*(Anoz/π)0,5. In other words, theneedle seat 26 may be formed directly upstream of thenozzle 5. This facilitates to keep the needle seat area Ansz small and to reduce the flow resistance. - Additionally or alternatively, the stroke S may correspond to at least 2*(Anoz/π)0,5, which corresponds to the Dnoz if the nozzle is of rotationally symmetric shape. Especially, the stroke S may correspond to at least 2,8*(Anoz/π)0,5. As a consequence, the end portion of the
needle 20 does not impair fluid flow through thenozzle 5 or theneedle seat 20 in its opened position. - The
ejector 1 may be configured such that the flow cross-section Anoz of thenozzle 5 constitutes a minimum flow cross-section between theprimary inlet 2 and theconvergent mixing portion 6 when theneedle 20 is in its opened position. - In the exemplary embodiment, the
needle 20 never protrudes downstream of thenozzle 5. In other words, theneedle 20 never protrudes into theconvergent mixing portion 6. - As an additional feature, the depicted embodiment of the
ejector 1 provides a check valve functionality for preventing fluid flow from theoutlet 12 to thesecondary inlet 7. Theejector 1 provides a check member 80 for closing a fluid connection between the mixing portion (in more detail, the convergent mixing portion 6) and thesecondary inlet chamber 8. If theejector 1 is in its closed state, the check member 80 abuts on acheck valve seat 79 and blocks fluid flow from theoutlet 12 to thesecondary inlet 7. If theejector 1 is in its open state, fluid is sucked from thesecondary inlet 7 through thesecondary inlet chamber 3 and the secondary fluid passageway 9 into theconvergent mixing portion 6. Thereby, the check member 80 is displaced along the longitudinal direction L and lifts off from thecheck valve seat 79. - An annular end face of the
cylinder insert 77 and a corresponding abutment area on thetop cover 76 are grounded flat. An elastic member 90 (which is a coil spring in this embodiment) biases thecylinder insert 77 against the top cover. Hence, no significant fluid leakage or pressure propagation can occur directly from theprimary inlet chamber 3 to thesecond cylinder chamber 38. Theelastic member 90 is arranged in theprimary inlet chamber 3 and coaxially to theneedle 20. It is squeezed between thetop cover 76 and theinsert assembly holder 78. - Optionally, a
filter 91 is provided between theprimary inlet 2 and thenozzle inlet 4. In the exemplary embodiment, thefilter 91 is provided in theprimary inlet chamber 3 around theelastic member 90, wherein the elastic member supports (backs up) thefilter 91. - The
top cover 76 is removably fixed to themain sleeve 71 by screws. If thetop cover 76 is detached, thecylinder insert 76 can be taken out of themain sleeve 71 for maintenance. - Naturally, the depicted embodiment is only an exemplary one and the elements can be implemented in other manners and geometries. For example, the end portion of the
needle 20 may be formed with another shape (e.g. convexly tapered), theneedle seat 26 and thenozzle 5 can be formed two by separate elements, and the like. -
- 1
- ejector
- 2
- primary inlet
- 3
- primary inlet chamber
- 4
- nozzle inlet
- 5
- nozzle
- 6
- (convergent) mixing portion
- 7
- secondary inlet
- 8
- secondary inlet chamber
- 9
- secondary fluid passageway
- 10
- (cylindrical) mixing portion
- 11
- diffuser portion
- 12
- outlet
- 20
- needle
- 21
- needle tip
- 22
- first conical needle portion
- 23
- annular edge
- 24
- second conical needle portion
- 25
- needle stem
- 26
- needle seat
- 27
- nozzle insert
- 30
- actuating mechanism
- 31
- piston
- 32
- equalization passage
- 33
- resilient member
- 35
- cylinder
- 36
- chamber inlet
- 37
- first cylinder chamber
- 38
- second cylinder chamber
- 39
- fluid connection (chamber outlet, part of drain passage)
- 40
- annular end wall
- 50
- pilot valve
- 51
- valve seat
- 52
- valve member
- 53
- actuator
- 54
- first fluid passage (part of drain passage)
- 55
- second fluid passage (part of drain passage)
- 56, 57
- fluid passage (part of drain passage)
- 70
- housing
- 71
- main sleeve
- 72
- primary inlet connector
- 73
- secondary inlet connector
- 74
- first diffuser tube
- 75
- second diffuser tube76
- 76
- top cover
- 77
- cylinder insert
- 78
- insert assembly holder
- 79
- check valve seat
- 80
- check member
- 90
- elastic member
- 91
- filter
- C
- central axis
- Dnoz
- diameter (of the nozzle 5)
- Dns
- diameter (of the needle seat 26)
- Dp
- diameter (of the piston 31)
- L
- longitudinal direction
Claims (15)
- Ejector (1) comprisinga primary inlet (2); a secondary inlet (7); and an outlet (12);a nozzle (5) for jetting fluid supplied at the primary inlet (2) into a mixing portion (6, 10) for sucking fluid supplied at the secondary inlet (7) into the mixing portion (6, 10);a needle (20) and a needle seat (26), wherein the needle seat (26) is arranged downstream of the primary inlet (2) and upstream of the nozzle (5); andan actuating mechanism (30) for moving the needle (20) between an opened position, in which the needle (20) is lifted from the needle seat (26) for allowing fluid flow past the needle seat (26), and a closed position, in which the needle (20) abuts the needle seat (26) and blocks fluid flow past the needle seat (26), wherein the actuating mechanism (30) comprises:a cylinder (35) with a piston (31) connected to the needle (20), wherein a first cylinder chamber (37) is maximized when the needle (20) is in its opened position and a second cylinder chamber (38) is maximized when the needle (20) is in its closed position, wherein the first cylinder chamber (37) is in fluid communication with the primary inlet (2) via a chamber inlet (36), and wherein the second cylinder chamber (38) is in fluid communication with the first cylinder chamber (37) via an equalization passage (32), anda drain passage (39, 53, 54, 55, 56, 57) with a pilot valve (50), wherein the second cylinder chamber (38) is in fluid communication with the secondary inlet (7) and/orthe outlet (12) via the drain passage (39, 53, 54, 55, 56, 57) when the pilot valve (50) is in an open state.
- Ejector (1) according to claim 1, characterized in that a piston area, which is a cross-section area of the piston, is at least 1000 times a flow cross-section of the equalization passage (32).
- Ejector (1) according to any one of the preceding claims, characterized in that a needle seat area, which is a cross-section area of the needle seat (26) where the needle (20) engages the needle seat (26) in the closed position, is in the range from 1,005 to 1,4 times a flow cross-section of the nozzle (26).
- Ejector (1) according to any one of the preceding claims, characterized in that the pilot valve (50) is a solenoid valve.
- Ejector (1) according to any one of the preceding claims, characterized in that the piston area corresponds to at least 20 times the needle seat area.
- Ejector (1) according to any one of the preceding claims, characterized in that a stroke (S) of the needle (20) between the closed position and the opened position correspond to at least 2*(Anoz/π)0,5, where Anoz is the flow cross-section of the nozzle (5).
- Ejector (1) according to any one of the preceding claims, characterized in that the ejector (1) includes a check valve (79, 80) for preventing fluid flow from the outlet (12) to the secondary inlet (7).
- Ejector (1) according to any one of the preceding claims, characterized in that the equalization passage (32) is formed in the piston (31).
- Ejector (1) according to any one of the preceding claims, characterized in that the flow cross-section of the equalization passage (32) is in the range from 1,2 to 2,5 times a flow cross-section of the drain passage when the pilot valve (50) is in an open state.
- Ejector (1) according to any one of the preceding claims, characterized in that a nozzle inlet (4) is formed directly upstream of the nozzle (5), wherein the nozzle inlet (4) tapers toward the nozzle (5), wherein the needle seat (26) is located in the nozzle inlet (4), and wherein a length (W) of the nozzle inlet (4) corresponds to at least 1,8 times the stroke (S) of the needle (20) between the closed position and the opened position.
- Ejector (1) according to any one of the preceding claims, characterized in that the ejector (1) comprises a resilient member (33) acting against minimizing the second cylinder chamber (38) by the piston (31).
- Ejector (1) according to any one of the preceding claims, characterized in that the ejector (1) is configured such that an opening time of the needle (20) is at least 0,5 s and/or that a closing time of the needle (20) is at least 1 s.
- Ejector (1) according to any one of the preceding claims, characterized in that the flow cross-section of the nozzle (5) is at least 50 mm2.
- Ejector (1) according to any one of the preceding claims, characterized in that the cylinder (35) is formed by a cylinder insert (77) and a top cover (76), wherein an elastic member (81) biases the cylinder insert (77) in abutment against the top cover (76).
- Ejector assembly comprising at least two ejectors (1) according to any one of the claims 1 to 14.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP22190394.1A EP4325142A1 (en) | 2022-08-15 | 2022-08-15 | Ejector having an actuation mechanism with a pilot valve and an equalization passage between two cylinder chambers |
PCT/EP2023/072386 WO2024038014A1 (en) | 2022-08-15 | 2023-08-14 | Ejector having an actuation mechanism with a pilot valve and an equalization passage between two cylinder chambers |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP22190394.1A EP4325142A1 (en) | 2022-08-15 | 2022-08-15 | Ejector having an actuation mechanism with a pilot valve and an equalization passage between two cylinder chambers |
Publications (1)
Publication Number | Publication Date |
---|---|
EP4325142A1 true EP4325142A1 (en) | 2024-02-21 |
Family
ID=82940010
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP22190394.1A Pending EP4325142A1 (en) | 2022-08-15 | 2022-08-15 | Ejector having an actuation mechanism with a pilot valve and an equalization passage between two cylinder chambers |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP4325142A1 (en) |
WO (1) | WO2024038014A1 (en) |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1421843A (en) * | 1914-09-14 | 1922-07-04 | Westinghouse Electric & Mfg Co | Fluid-translating device |
US20040040340A1 (en) * | 2002-08-29 | 2004-03-04 | Masayuki Takeuchi | Refrigerant cycle with ejector having throttle changeable nozzle |
EP1722107A1 (en) * | 2004-03-01 | 2006-11-15 | Toyota Jidosha Kabushiki Kaisha | Ejector and fuel cell system with the same |
EP1923575A2 (en) | 2006-11-16 | 2008-05-21 | Honeywell International Inc. | Servo-controlled variable geometry ejector pump |
JP4134918B2 (en) | 2004-02-18 | 2008-08-20 | 株式会社デンソー | Ejector |
US7841193B2 (en) | 2006-02-16 | 2010-11-30 | Denso Corporation | Refrigerant flow-amount controlling device and ejector refrigerant cycle system using the same |
WO2012012501A2 (en) * | 2010-07-23 | 2012-01-26 | Carrier Corporation | High efficiency ejector cycle |
DE112015003818T5 (en) * | 2014-08-21 | 2017-05-04 | Denso Corporation | Ejector and ejector refrigeration cycle |
WO2018159320A1 (en) | 2017-03-02 | 2018-09-07 | 株式会社デンソー | Ejector module |
-
2022
- 2022-08-15 EP EP22190394.1A patent/EP4325142A1/en active Pending
-
2023
- 2023-08-14 WO PCT/EP2023/072386 patent/WO2024038014A1/en unknown
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1421843A (en) * | 1914-09-14 | 1922-07-04 | Westinghouse Electric & Mfg Co | Fluid-translating device |
US20040040340A1 (en) * | 2002-08-29 | 2004-03-04 | Masayuki Takeuchi | Refrigerant cycle with ejector having throttle changeable nozzle |
JP4134918B2 (en) | 2004-02-18 | 2008-08-20 | 株式会社デンソー | Ejector |
EP1722107A1 (en) * | 2004-03-01 | 2006-11-15 | Toyota Jidosha Kabushiki Kaisha | Ejector and fuel cell system with the same |
US7841193B2 (en) | 2006-02-16 | 2010-11-30 | Denso Corporation | Refrigerant flow-amount controlling device and ejector refrigerant cycle system using the same |
EP1923575A2 (en) | 2006-11-16 | 2008-05-21 | Honeywell International Inc. | Servo-controlled variable geometry ejector pump |
WO2012012501A2 (en) * | 2010-07-23 | 2012-01-26 | Carrier Corporation | High efficiency ejector cycle |
DE112015003818T5 (en) * | 2014-08-21 | 2017-05-04 | Denso Corporation | Ejector and ejector refrigeration cycle |
WO2018159320A1 (en) | 2017-03-02 | 2018-09-07 | 株式会社デンソー | Ejector module |
Also Published As
Publication number | Publication date |
---|---|
WO2024038014A1 (en) | 2024-02-22 |
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