US20130216407A1 - Centrifugal pump - Google Patents
Centrifugal pump Download PDFInfo
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- US20130216407A1 US20130216407A1 US13/818,166 US201113818166A US2013216407A1 US 20130216407 A1 US20130216407 A1 US 20130216407A1 US 201113818166 A US201113818166 A US 201113818166A US 2013216407 A1 US2013216407 A1 US 2013216407A1
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- centrifugal pump
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- 230000003247 decreasing effect Effects 0.000 claims description 13
- 230000001360 synchronised effect Effects 0.000 claims description 13
- 238000005265 energy consumption Methods 0.000 abstract description 9
- 230000006870 function Effects 0.000 description 16
- 238000001595 flow curve Methods 0.000 description 11
- 238000004804 winding Methods 0.000 description 5
- 239000012530 fluid Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 230000005415 magnetization Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000004378 air conditioning Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D13/00—Pumping installations or systems
- F04D13/02—Units comprising pumps and their driving means
- F04D13/06—Units comprising pumps and their driving means the pump being electrically driven
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
- F04D15/0027—Varying behaviour or the very pump
- F04D15/0033—By-passing by increasing clearance between impeller and its casing
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D25/00—Pumping installations or systems
- F04D25/02—Units comprising pumps and their driving means
- F04D25/06—Units comprising pumps and their driving means the pump being electrically driven
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/18—Rotors
- F04D29/22—Rotors specially for centrifugal pumps
- F04D29/2261—Rotors specially for centrifugal pumps with special measures
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/18—Rotors
- F04D29/22—Rotors specially for centrifugal pumps
- F04D29/24—Vanes
- F04D29/242—Geometry, shape
- F04D29/245—Geometry, shape for special effects
Definitions
- Embodiments of the present invention generally relate to a single speed circulator pump. Embodiments of the invention more particularly relate to a circulator pump having a low energy consumption rate in the typical mode of operation.
- the centrifugal pump includes at least one impeller, a pump housing and an electrical motor.
- the pump has a Q-H pump curve with a head H 0 at zero flow and a head H ref corresponding to the highest hydraulic power, where H ref is greater than H 0 . Therefore, the pump has low energy consumption rate, especially at low flow corresponding to the conditions in which the pump is operated most of the time.
- the pump according to the invention is less energy consuming than the prior art centrifugal pumps.
- the at least one impeller includes impeller blades that are shaped in a manner so that that H ref is greater than H 0 . If the impeller blades are forward swept, for example, H ref would be greater than H 0 in the Q-H pump curve (where the head at zero flow is denoted H 0 and where the head corresponding to the highest hydraulic power is denoted H ref ).
- the forward swept blades are swept or curved from the radial inner side to the radial outer side in rotational direction.
- the first part of the Q-H curve for the pump is an increasing function of the flow.
- the pump can be achieved to have a Q-H curve where H ref is greater than H 0 and more specifically a pump having a low energy consumption rate at low flow.
- the last part of the Q-H curve is a decreasing function of the flow.
- a pump has a decreasing power consumption rate that so that overload of the motor can be avoided.
- the last part of the Q-H curve is a decreasing function. This may, for example, be achieved by choosing a pump housing geometry that restricts the flow rate at high head.
- the pump housing may be designed in such way that the cross sectional area of the volute is reduced or can be reduced as a function of the head. This will cause a restricted flow at high head.
- the special design of the impeller to achieve a restricted flow at high head.
- the impeller may be configured so that the distance between the front plate and the back plate can be altered as a function of the head.
- the pump housing and/or the impeller is configured to introduce flow restriction such that the end part of the Q-H curve as a function of the flow is decreasing.
- flow restriction is means an object or device that restricts the flow.
- Flow restriction devices may, for example, be an impeller or a pump housing having a specific geometry.
- the impeller has forward swept blades.
- Forward swept impeller blades may contribute to an increasing Q-H curve.
- the size of the impeller may be minimized because an impeller with forward swept impeller blades is capable of creating a higher flow than an impeller with backward swept impeller blades given the same conditions.
- the impeller may be constructed in a various ways even though the impeller has forward swept impeller blades.
- the pump has a synchronous motor. This may be an advantage due to the relative high efficiency of synchronous motors especially at low flow.
- the synchronous motor operates synchronously with line frequency.
- the rotational speed is determined by the number of pairs of poles and the line frequency.
- a synchronous motor is highly efficient and thus by using a synchronous motor it is possible to achieve a pump with a low energy consumption rate.
- the motor is working with constant speed during operation. This can be achieved by using a synchronous motor.
- the pump is a circulator pump.
- the circulator pump may be a glandless (wet-runner) pump. This pump may be used for heating, domestic hot water and air-conditioning applications, for example.
- the motor is a line start permanent magnet motor.
- a line star permanent magnet motor is basically a combination of an asynchronous motor and a synchronous motor with fixed magnetization. In a line start permanent magnet motor there is no field winding, instead permanent magnets are used in order to provide the necessary excitation flux.
- a synchronous motor without a rotor winding has no net torque at the speeds different from the synchronous.
- some kind of start winding in the rotor has to be used.
- currents are induced in the rotor winding. These currents interact with the stator flux field to produce an asynchronous torque that accelerates the rotor.
- the rotor speed is sufficiently close to synchronous speed, and on condition that load torque and inertia are not too high, the rotor will be pulled into synchronism.
- the asynchronous torque vanishes and the motor acts as a synchronous motor except that the rotor magnetization is supplied by permanent magnets and not by a DC-current in a field winding.
- the impeller blades are arced and distributed symmetrically along the periphery of the impeller plate.
- the first part of the Q-H curve is an increasing function of the flow
- H ref is greater than H 0 (where H ref is the head corresponding to the highest hydraulic power and H 0 is the head at zero flow).
- the impeller includes a first set of impeller blades and a second set of blades, wherein the first set of impeller blades are longer than the second set of impeller blades and where the first set of impeller blades and the second set of impeller blades are distributed alternately along the periphery of the impeller plate.
- a Q-H curve having the desired properties can be achieved.
- FIG. 1 shows a Q-H curve of one embodiment according to the invention
- FIG. 2 is a prior art Q-H curve
- FIG. 3 a illustrates the prior art Q-H curve shown in FIG. 2 ;
- FIG. 3 b shows the power-flow curve for a pump having the Q-H curve illustrated in FIG. 3 a;
- FIG. 4 a illustrates the Q-H curve shown in FIG. 1 ;
- FIG. 4 b shows the power-flow curve for a pump having the Q-H curve illustrated in FIG. 4 a;
- FIG. 5 is a comparison of the power-flow curves illustrated in FIG. 3 a and FIG. 4 a
- FIG. 6 a shows the Q-H curve according to another embodiment of the invention.
- FIG. 6 b shows the Q-H curve according to a third embodiment of the invention.
- FIG. 7 a illustrates a schematically view of Q-H curves for different impeller blade angles
- FIG. 7 b illustrates a schematically view of three different impeller types
- FIG. 8 illustrates an impeller according to one embodiment of the invention
- FIG. 9 illustrates an impeller according to one embodiment of the invention.
- FIG. 10 illustrates an impeller according to one embodiment of the invention.
- the pumping performance of a centrifugal pump is frequently expressed in the form of a Q-H curve, depicting the head H (normally measured in m) as a function of the flow Q (for instance measured in m 3 /h) of the pump.
- the slope of the Q-H curve is determined by the pump construction and particularly by the design of the impeller.
- H is the head
- g is gravity
- ⁇ is the density of the fluid
- Q is the flow.
- ⁇ control is the efficiency of the control and ⁇ motor motor is the efficiency of the motor.
- the flow where the pump has the highest efficiency is referred to as the best point.
- Speed regulated pumps are used to adjust the generated pressure according to the actual demand. Speed regulation requires a regulation of the motor. In many pumps a frequency converter is used to regulate the speed of the motor, however; such solution is expensive and technically demanding. On the other hand, many unregulated motors have a low efficiency. A high efficiency, especially at low loads, can be achieved by using a line start permanent magnet motor.
- a line start permanent magnet motor has typically a significant position dependent difference in the inductance (difference in the D- and Q-axis inductance). This difference gives a reluctance torque, so that the total torque production from the motor is given by the combination of the alignment torque and the reluctance torque.
- the reluctance torque can be used to increase the efficiency of the motor at lower load (at a slightly reduced efficiency at maximum load). Hereby the energy consumption can be lowered.
- Combining a line start motor and a pump having a Q-H pump curve where H ref is greater than H 0 may eliminate the use of a frequency converter.
- a pump with a high efficiency may be achieved by combining a line start motor and a pump having a Q-H pump curve where H ref is greater than H 0 . Therefore, the present invention may make it possible to make a high efficiency that is cheaper than the prior art high efficiency pump.
- unregulated pumps are equipped with manual speed change-over devices e.g., a rotary knob that may be set in three different speeds.
- Most pump manufacturers have focused on producing pumps having different regulation curves.
- Line start motors are generally used for applications in which an exact and constant speed is required.
- One example of such application is a conveyor belt.
- a pump is provided with a line start motor there is no speed regulation option. Therefore, pump manufactures use other types of motors for their pumps.
- the pump is equipped with a line start motor.
- the efficiency is increased compared with traditional asynchronous motors, especially at the lower loads. Therefore, the line start motor makes it possible to save energy.
- FIG. 1 a Q-H curve 4 according to a preferred embodiment of the present invention is illustrated in FIG. 1 .
- the Q-H curve 4 illustrates the hydraulic head (H) 2 (hereinafter referred to as “head”) as a function of the flow (Q) 6 .
- head hydraulic head
- the first part 8 approximately the first two thirds
- the last part 10 approximately the last third of the Q-H curve 4 has a negative slope.
- the last part 10 of the Q-H curve 4 is decreasing. It can be seen that H ref 30 is greater than H 0 28 (where H ref is the head corresponding to the highest hydraulic power and H 0 is the head at zero flow). Moreover, the global maximum 24 of the Q-H curve 4 is indicated and it can be seen that (QH) ref is offset slightly to the right side of the global maximum 24 of the Q-H curve 4.
- FIG. 2 shows a prior art Q-H curve 4 (the head 2 as function of the flow 6 ). It can be seen that the head (H) 2 is a decreasing function of the flow (Q) 6 .
- This Q-H curve 4 corresponds to the Q-H curve of a typical centrifugal type circulator pump. It can be seen that H 0 28 is greater than H ref 30 (where H ref is the head corresponding to the highest hydraulic power and H 0 is the head at zero flow).
- FIG. 3 a illustrates the Q-H curve 4 shown in FIG. 2 and FIG. 3 b illustrates the corresponding power-flow curve 12 (the power (P) 14 as function of the flow (Q) 6 ) for a prior art pump having the Q-H curve 4 illustrated in FIG. 3 a .
- FIG. 3 b it can be seen that the maximal flow Q 100 % 22 , the flow Q 25 % 16 corresponding to 25% of the maximal flow Q 100 % 22 , the flow Q 50 % 18 corresponding to 50% of the maximal flow Q 100 % 22 and the flow Q75% 20 corresponding to 75% of the maximal flow Q 100 % 22 are lying relatively high (the indicated power values 16 , 18 , 20 and 22 ) on the power-flow curve 12 .
- FIG. 4 a illustrates the Q-H curve 4 shown in FIG. 1
- FIG. 4 b illustrates the power-flow curve 12 (the power (P) 14 as function of the flow (Q) 6 ) for a pump having the Q-H curve 4 illustrated in FIG. 4 a
- the flow Q25% 16 corresponding to 25% of the maximal flow Q 100 % 22
- the flow Q 50 % 18 corresponding to 50% of the maximal flow Q 100 % 22
- the flow Q 75 % 20 corresponding to 75% of the maximal flow Q 100 % 22 are associated with lower power values 16 , 18 , 20 than in the prior art pump curve 4 illustrated in FIG. 3 b.
- FIG. 5 shows a comparison of the power-flow curves illustrated in FIG. 3 a and FIG. 4 a . It can be seen from FIG. 5 that the maximal flow Q 100 % 22 ′, 22 ′′ of both the prior art power-flow curve 38 and for the power-flow curve 40 corresponding to a pump having the Q-H curve 4 according to the invention (illustrated in FIG. 4 a ) are almost coinciding. If we look at the power-flow curve 40 corresponding to the invention is can be seen that the power value at the flow Q 25 % 16 ′′ corresponding to 25% of the maximal flow Q 100 % is significantly lower than the prior art power value at the flow Q 25 % 16 ′.
- the power value at the flow Q 50 % 18 ′′ corresponding to 50% of the maximal flow Q 100 % is significantly lower than the prior art power value at the flow Q 50 % 18 ′.
- the power value at the flow Q 75 % 20 ′′ corresponding to 75% of the maximal flow Q 100 % is significantly lower than the prior art power value at the flow Q 75 % 20 ′. Accordingly, the pump according to the present invention will have a low energy consumption rate.
- FIG. 6 a illustrates the Q-H curve 4 according to an embodiment of the invention.
- the head (H) 2 is plotted against the flow (Q) 6 .
- Approximately the first two thirds 8 of the Q-H curve 4 has a positive slope and thus the first part 8 of the Q-H curve 4 is increasing.
- Approximately the last third 10 of the Q-H curve 4 has a negative slope and therefore, the last part 10 of the Q-H curve 4 is decreasing.
- H ref 30 is greater than H 0 28 (where H ref is the head corresponding to the highest hydraulic power and H 0 is the head at zero flow).
- the global maximum 24 of the Q-H curve 4 is and (QH) ref 26 are almost coinciding.
- FIG. 6 b illustrates a Q-H curve 4 according to another embodiment of the invention.
- This Q-H curve 4 is almost similar to the Q-H curve 4 shown in FIG. 6 a , however; the global maximum 24 of the Q-H curve 4 is and (QH) ref 26 are displaced relative to one another. (QH) ref 26 is located to the right for the global maximum 24 of the Q-H curve 4 .
- FIG. 7 a illustrates a schematic view of theoretical Q-H curves 42 , 44 , 46 for different impeller blade angels.
- the blade angle ⁇ is indicated in FIG. 7 b and represents the angle between the outer periphery of the impeller and the outer side of the impeller blade.
- FIG. 7 a shows that backward swept impellers have a decreasing theoretical Q-H curve 46 .
- FIG. 7 a also shows that forward swept impellers have an increasing theoretical Q-H curve 46 .
- the theoretical Q-H curve 44 of a neutral impeller construction where the blade angle ⁇ between the outer periphery of the impeller and the outer side of the impeller blade is 90 degrees is flat (horizontal).
- forward swept blades means that the angle ⁇ is greater than 90°, where ⁇ is defined as the angle between the outer periphery of the impeller 32 and the outer side of the impeller blade 34 .
- backwards swept blades means that the angle ⁇ is less than 90°.
- neutral swept blades means that the angle ⁇ is equal to 90°.
- FIG. 7 b illustrates a schematic view of three different impeller 32 types where the blade angle ⁇ is under 90 degrees, equal to 90 degrees and more than 90 degrees respectively.
- the blades 34 as well as the rotational direction of the impeller 36 are indicated in the figure.
- FIG. 8 shows an impeller 32 according to one embodiment of the invention.
- the impeller 32 includes a first set of impeller blades 34 and a second set of blades 35 , where the first set of impeller blades 34 are longer than the second set of impeller blades 35 and where the first set of impeller blades 34 and the second set of impeller blades 35 are distributed alternately along the periphery of the impeller plate 48 .
- the first set of impeller blades 34 includes ten blades and the second set of impeller blades 35 also includes ten blades.
- both the first set of impeller blades 34 and the second set of blades 35 are forward swept because the angle between the outer periphery of the impeller 32 and the outer side of the impeller blades 34 , 35 is greater than 90°.
- FIG. 9 illustrates a typical impeller 32 having a number of backwards swept impeller blades 34 , i.e., the impeller blades are swept or curved against the rotational direction 36 . It is indicated that the rotational direction 36 is counter clockwise—the rotational speed is denoted ⁇ and the radius r of the impeller 32 is also indicated.
- the absolute velocity C of the fluid is given by the sum of the tangential velocity U of the impeller 32 and the relative velocity W relative to the impeller 32 . Theses velocities C, U and W are indicated with arrows.
- the magnitude of the tangential velocity U of the impeller 32 is given by the product of the radius r and the rotational speed ⁇ :
- the blade angle ⁇ is less than 90 degrees.
- FIG. 10 illustrates an impeller 32 with a forward swept impeller blade 34 , i.e., the blades are swept in rotational direction 36 . It is indicated that the rotational direction 36 is counter clockwise like in FIG. 9 .
- the projection C U of C in the tangential plane is indicated and it can be seen that this forward swept impeller has the following characteristic:
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Abstract
A centrifugal pump has at least one impeller, a pump housing and an electrical motor. The pump has a Q-H pump curve having a head H0 at zero flow and a head Href corresponding to the highest hydraulic power, and that Href is greater than H0. The pump has low energy consumption rate, especially at low flow corresponding to the conditions in which the pump is operated most of the time. Thus, the pump according to the invention is less energy consuming than the prior art centrifugal pumps.
Description
- This application is a Section 371 of International Application No. PCT/EP2011/061741, filed Jul. 11, 2011, which was published in the English language on Mar. 1, 2012, under International Publication No. WO 2012/025289 A1 and the disclosure of which is incorporated herein by reference.
- Embodiments of the present invention generally relate to a single speed circulator pump. Embodiments of the invention more particularly relate to a circulator pump having a low energy consumption rate in the typical mode of operation.
- It is known to reduce the energy consumption rate of a pump by regulating the speed of the pump. This may, for example, be done by using a frequency converter in a pump. This solution is however relatively technically demanding and expensive. Therefore, it is desirable to have a cheaper alternative to this solution.
- When the speed of the pump can be changed during operation it is possible to fit the pump speed to the actual pressure and flow demand, however when a single speed pump is operated, a lot of energy is used to build up a higher pressure than required. Therefore, unregulated pumps normally are energy consuming. Normally a pump is only required to perform to its maximum about 5-10% of the time and hence a lot of energy can be saved by adjusting the pump to actual demand.
- It is possible to regulate a pump by using various regulation methods such as proportional pressure and constant pressure regulation. Speed regulation of pumps, however, requires regulation components such as a frequency converter that is an expensive additional feature to the pump.
- Accordingly, it is desirable to provide a less expensive pump that has a reduced energy consumption rate.
- Preferred embodiments, benefits and further scope of applicability of the present invention will become apparent from the claims and the description given hereinafter.
- The centrifugal pump according to embodiments of the invention includes at least one impeller, a pump housing and an electrical motor. The pump has a Q-H pump curve with a head H0 at zero flow and a head Href corresponding to the highest hydraulic power, where Href is greater than H0. Therefore, the pump has low energy consumption rate, especially at low flow corresponding to the conditions in which the pump is operated most of the time. Thus, the pump according to the invention is less energy consuming than the prior art centrifugal pumps.
- In one embodiment of the invention the at least one impeller includes impeller blades that are shaped in a manner so that that Href is greater than H0. If the impeller blades are forward swept, for example, Href would be greater than H0 in the Q-H pump curve (where the head at zero flow is denoted H0 and where the head corresponding to the highest hydraulic power is denoted Href).
- The forward swept blades are swept or curved from the radial inner side to the radial outer side in rotational direction.
- In one embodiment of the invention the first part of the Q-H curve for the pump is an increasing function of the flow. Hereby the pump can be achieved to have a Q-H curve where Href is greater than H0 and more specifically a pump having a low energy consumption rate at low flow.
- It is also possible to have a pump where the entire Q-H curve is an increasing function of the flow.
- In another embodiment of the invention, the last part of the Q-H curve is a decreasing function of the flow. Hereby it can be achieved that a pump has a decreasing power consumption rate that so that overload of the motor can be avoided. There may be several ways of achieving that the last part of the Q-H curve is a decreasing function. This may, for example, be achieved by choosing a pump housing geometry that restricts the flow rate at high head. For example the pump housing may be designed in such way that the cross sectional area of the volute is reduced or can be reduced as a function of the head. This will cause a restricted flow at high head. Further, it may for example be also possible to use the special design of the impeller to achieve a restricted flow at high head. For example the impeller may be configured so that the distance between the front plate and the back plate can be altered as a function of the head.
- In one embodiment of the invention the pump housing and/or the impeller is configured to introduce flow restriction such that the end part of the Q-H curve as a function of the flow is decreasing. The term “flow restriction” is means an object or device that restricts the flow. Flow restriction devices may, for example, be an impeller or a pump housing having a specific geometry.
- In another embodiment of the invention the impeller has forward swept blades. Forward swept impeller blades may contribute to an increasing Q-H curve. Moreover, the size of the impeller may be minimized because an impeller with forward swept impeller blades is capable of creating a higher flow than an impeller with backward swept impeller blades given the same conditions. The impeller may be constructed in a various ways even though the impeller has forward swept impeller blades.
- In another embodiment of the invention the pump has a synchronous motor. This may be an advantage due to the relative high efficiency of synchronous motors especially at low flow.
- The synchronous motor operates synchronously with line frequency. The rotational speed is determined by the number of pairs of poles and the line frequency. A synchronous motor is highly efficient and thus by using a synchronous motor it is possible to achieve a pump with a low energy consumption rate.
- In one embodiment according to the invention the motor is working with constant speed during operation. This can be achieved by using a synchronous motor.
- In one embodiment according to the invention the pump is a circulator pump. The circulator pump may be a glandless (wet-runner) pump. This pump may be used for heating, domestic hot water and air-conditioning applications, for example.
- In another embodiment according to the invention the motor is a line start permanent magnet motor. A line star permanent magnet motor is basically a combination of an asynchronous motor and a synchronous motor with fixed magnetization. In a line start permanent magnet motor there is no field winding, instead permanent magnets are used in order to provide the necessary excitation flux.
- A synchronous motor without a rotor winding has no net torque at the speeds different from the synchronous. In order to start the motor from a constant frequency supply (such as the mains) some kind of start winding in the rotor has to be used. During the start, currents are induced in the rotor winding. These currents interact with the stator flux field to produce an asynchronous torque that accelerates the rotor. When the rotor speed is sufficiently close to synchronous speed, and on condition that load torque and inertia are not too high, the rotor will be pulled into synchronism. After the rotor has been synchronised the asynchronous torque vanishes and the motor acts as a synchronous motor except that the rotor magnetization is supplied by permanent magnets and not by a DC-current in a field winding.
- In one embodiment according to the invention the impeller blades are arced and distributed symmetrically along the periphery of the impeller plate. By this impeller construction it is possible to generate a great flow and achieve the desired Q-H pump curve where
- the first part of the Q-H curve is an increasing function of the flow;
- that last part of the Q-H curve is a decreasing function of the flow and
- Href is greater than H0 (where Href is the head corresponding to the highest hydraulic power and H0 is the head at zero flow).
- In another embodiment according to the invention the impeller includes a first set of impeller blades and a second set of blades, wherein the first set of impeller blades are longer than the second set of impeller blades and where the first set of impeller blades and the second set of impeller blades are distributed alternately along the periphery of the impeller plate. Hereby a Q-H curve having the desired properties can be achieved.
- In one embodiment according to the invention (⅔)·Href≧H0. A pump having a Q-H curve with these properties will be significantly less energy consuming than the prior art centrifugal pumps.
- It would also be possible to have a pump according to the invention where (3/5)Href≧H0. A pump with such a Q-H curve would also be significantly less energy consuming than the prior art centrifugal pumps.
- The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.
- In the drawings:
-
FIG. 1 shows a Q-H curve of one embodiment according to the invention; -
FIG. 2 is a prior art Q-H curve; -
FIG. 3 a illustrates the prior art Q-H curve shown inFIG. 2 ; -
FIG. 3 b shows the power-flow curve for a pump having the Q-H curve illustrated inFIG. 3 a; -
FIG. 4 a illustrates the Q-H curve shown inFIG. 1 ; -
FIG. 4 b shows the power-flow curve for a pump having the Q-H curve illustrated inFIG. 4 a; -
FIG. 5 is a comparison of the power-flow curves illustrated inFIG. 3 a andFIG. 4 a -
FIG. 6 a shows the Q-H curve according to another embodiment of the invention; -
FIG. 6 b shows the Q-H curve according to a third embodiment of the invention; -
FIG. 7 a illustrates a schematically view of Q-H curves for different impeller blade angles; -
FIG. 7 b illustrates a schematically view of three different impeller types; -
FIG. 8 illustrates an impeller according to one embodiment of the invention; -
FIG. 9 illustrates an impeller according to one embodiment of the invention; and -
FIG. 10 illustrates an impeller according to one embodiment of the invention. - Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention defined by the claims will become apparent to those skilled in the art from this detailed description.
- The pumping performance of a centrifugal pump is frequently expressed in the form of a Q-H curve, depicting the head H (normally measured in m) as a function of the flow Q (for instance measured in m3/h) of the pump. The slope of the Q-H curve is determined by the pump construction and particularly by the design of the impeller.
- The majority of circulator pumps are provided with impellers having backwards swept impeller blades. These types of impellers generate a Q-H curve where the head is decreasing with increasing flow (see
FIG. 2 ). - The hydraulic power Ph is given by the following equation (1)
-
P h =H·g·ρ·Q (1) - where H is the head, g is gravity, ρ is the density of the fluid and Q is the flow.
- In order to calculate the hydraulic efficiency ηh of the hydraulic part of the pump (the pump housing and the impeller) one needs to know the power Pn supplied to the hydraulic part of the pump as well as the power Ph that the pump transfers to the fluid. This is given by the following equation (2)
-
- In order to calculate the total efficiency ηt of the pump one has to know the total power Pt supplied to the control (if any) and the motor as well as the power Ph that the pump transfers to the fluid. This is given by the following equation (3)
-
- The total efficiency ηt of the pump is given by the following equation (4)
-
ηt=ηcontrol·ηmotor·ηh (4) - where ηcontrol is the efficiency of the control and ηmotor motor is the efficiency of the motor.
- The flow where the pump has the highest efficiency is referred to as the best point.
- When working with the Q-H curve, one often focuses on the head H0 at zero flow and the head Href corresponding to the highest hydraulic power Ph, max. These points are characteristics of the pump. In the Q-H curves of the prior art centrifugal pumps H0 is greater than Href and the H curve is normally a decreasing function of Q. If we look at the power-flow curve for the prior art centrifugal pumps, the power consumption is relatively high, especially at low flow. The pumps are operated in the low flow area the majority of the time. Therefore, it would be advantageous to have a pump that is less energy consuming, especially in the low flow area.
- Speed regulated pumps are used to adjust the generated pressure according to the actual demand. Speed regulation requires a regulation of the motor. In many pumps a frequency converter is used to regulate the speed of the motor, however; such solution is expensive and technically demanding. On the other hand, many unregulated motors have a low efficiency. A high efficiency, especially at low loads, can be achieved by using a line start permanent magnet motor. A line start permanent magnet motor has typically a significant position dependent difference in the inductance (difference in the D- and Q-axis inductance). This difference gives a reluctance torque, so that the total torque production from the motor is given by the combination of the alignment torque and the reluctance torque. By tailoring the geometry to the hydraulic load and the specific application the reluctance torque can be used to increase the efficiency of the motor at lower load (at a slightly reduced efficiency at maximum load). Hereby the energy consumption can be lowered.
- Combining a line start motor and a pump having a Q-H pump curve where Href is greater than H0 may eliminate the use of a frequency converter. A pump with a high efficiency may be achieved by combining a line start motor and a pump having a Q-H pump curve where Href is greater than H0. Therefore, the present invention may make it possible to make a high efficiency that is cheaper than the prior art high efficiency pump.
- Traditionally, unregulated pumps are equipped with manual speed change-over devices e.g., a rotary knob that may be set in three different speeds. Most pump manufacturers have focused on producing pumps having different regulation curves. Line start motors are generally used for applications in which an exact and constant speed is required. One example of such application is a conveyor belt.
- If a pump is provided with a line start motor there is no speed regulation option. Therefore, pump manufactures use other types of motors for their pumps. In embodiments of the present invention, however, the pump is equipped with a line start motor. Hereby it is achieved that the efficiency is increased compared with traditional asynchronous motors, especially at the lower loads. Therefore, the line start motor makes it possible to save energy.
- Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a
Q-H curve 4 according to a preferred embodiment of the present invention is illustrated inFIG. 1 . TheQ-H curve 4 illustrates the hydraulic head (H) 2 (hereinafter referred to as “head”) as a function of the flow (Q) 6. It can be seen fromFIG. 1 that the first part 8 (approximately the first two thirds) of theQ-H curve 4 has a positive slope. This means that thefirst part 8 of theQ-H curve 4 is increasing. Moreover, it can bee seen that the last part 10 (approximately the last third) of theQ-H curve 4 has a negative slope. Accordingly, thelast part 10 of theQ-H curve 4 is decreasing. It can be seen thatH ref 30 is greater than H0 28 (where Href is the head corresponding to the highest hydraulic power and H0 is the head at zero flow). Moreover, theglobal maximum 24 of theQ-H curve 4 is indicated and it can be seen that (QH)ref is offset slightly to the right side of theglobal maximum 24 of theQ-H curve 4. -
FIG. 2 shows a prior art Q-H curve 4 (thehead 2 as function of the flow 6). It can be seen that the head (H) 2 is a decreasing function of the flow (Q) 6. ThisQ-H curve 4 corresponds to the Q-H curve of a typical centrifugal type circulator pump. It can be seen thatH 0 28 is greater than Href 30 (where Href is the head corresponding to the highest hydraulic power and H0 is the head at zero flow). -
FIG. 3 a illustrates theQ-H curve 4 shown inFIG. 2 andFIG. 3 b illustrates the corresponding power-flow curve 12 (the power (P) 14 as function of the flow (Q) 6) for a prior art pump having theQ-H curve 4 illustrated inFIG. 3 a. InFIG. 3 b it can be seen that the maximal flow Q100% 22, the flow Q25% 16 corresponding to 25% of the maximal flow Q100% 22, the flow Q50% 18 corresponding to 50% of the maximal flow Q100% 22 and theflow Q75% 20 corresponding to 75% of the maximal flow Q100% 22 are lying relatively high (the indicatedpower values flow curve 12. -
FIG. 4 a illustrates theQ-H curve 4 shown inFIG. 1 andFIG. 4 b illustrates the power-flow curve 12 (the power (P) 14 as function of the flow (Q) 6) for a pump having theQ-H curve 4 illustrated inFIG. 4 a. InFIG. 4 b it can be seen that theflow Q25% 16 corresponding to 25% of the maximal flow Q100% 22, the flow Q50% 18 corresponding to 50% of the maximal flow Q100% 22 and the flow Q75% 20 corresponding to 75% of the maximal flow Q100% 22 are associated with lower power values 16, 18, 20 than in the priorart pump curve 4 illustrated inFIG. 3 b. -
FIG. 5 shows a comparison of the power-flow curves illustrated inFIG. 3 a andFIG. 4 a. It can be seen fromFIG. 5 that the maximal flow Q100% 22′, 22″ of both the prior art power-flow curve 38 and for the power-flow curve 40 corresponding to a pump having theQ-H curve 4 according to the invention (illustrated inFIG. 4 a) are almost coinciding. If we look at the power-flow curve 40 corresponding to the invention is can be seen that the power value at the flow Q25% 16″ corresponding to 25% of the maximal flow Q100% is significantly lower than the prior art power value at the flow Q25% 16′. It can also be seen that the power value at the flow Q50% 18″ corresponding to 50% of the maximal flow Q100% is significantly lower than the prior art power value at the flow Q50% 18′. Besides, the power value at the flow Q75% 20″ corresponding to 75% of the maximal flow Q100% is significantly lower than the prior art power value at the flow Q75% 20′. Accordingly, the pump according to the present invention will have a low energy consumption rate. -
FIG. 6 a illustrates theQ-H curve 4 according to an embodiment of the invention. In theQ-H curve 4 the head (H) 2 is plotted against the flow (Q) 6. Approximately the first twothirds 8 of theQ-H curve 4 has a positive slope and thus thefirst part 8 of theQ-H curve 4 is increasing. Approximately the last third 10 of theQ-H curve 4 has a negative slope and therefore, thelast part 10 of theQ-H curve 4 is decreasing.H ref 30 is greater than H0 28 (where Href is the head corresponding to the highest hydraulic power and H0 is the head at zero flow). Besides, theglobal maximum 24 of theQ-H curve 4 is and (QH)ref 26 are almost coinciding. -
FIG. 6 b illustrates aQ-H curve 4 according to another embodiment of the invention. ThisQ-H curve 4 is almost similar to theQ-H curve 4 shown inFIG. 6 a, however; theglobal maximum 24 of theQ-H curve 4 is and (QH)ref 26 are displaced relative to one another. (QH)ref 26 is located to the right for theglobal maximum 24 of theQ-H curve 4. -
FIG. 7 a illustrates a schematic view of theoretical Q-H curves 42, 44, 46 for different impeller blade angels. In thesecurves height 2 is plotted against theflow 6. The blade angle β is indicated inFIG. 7 b and represents the angle between the outer periphery of the impeller and the outer side of the impeller blade.FIG. 7 a shows that backward swept impellers have a decreasingtheoretical Q-H curve 46.FIG. 7 a also shows that forward swept impellers have an increasingtheoretical Q-H curve 46. It can also be seen that thetheoretical Q-H curve 44 of a neutral impeller construction where the blade angle β between the outer periphery of the impeller and the outer side of the impeller blade is 90 degrees is flat (horizontal). - The term “forward swept blades” means that the angle β is greater than 90°, where β is defined as the angle between the outer periphery of the
impeller 32 and the outer side of theimpeller blade 34. The term “backwards swept blades” means that the angle β is less than 90°. The term “neutral swept blades” 34 means that the angle β is equal to 90°. -
FIG. 7 b illustrates a schematic view of threedifferent impeller 32 types where the blade angle β is under 90 degrees, equal to 90 degrees and more than 90 degrees respectively. Theblades 34 as well as the rotational direction of theimpeller 36 are indicated in the figure. -
FIG. 8 shows animpeller 32 according to one embodiment of the invention. Theimpeller 32 includes a first set ofimpeller blades 34 and a second set ofblades 35, where the first set ofimpeller blades 34 are longer than the second set ofimpeller blades 35 and where the first set ofimpeller blades 34 and the second set ofimpeller blades 35 are distributed alternately along the periphery of theimpeller plate 48. The first set ofimpeller blades 34 includes ten blades and the second set ofimpeller blades 35 also includes ten blades. When one examines therotational direction 36 of theimpeller 32, it can be seen that both the first set ofimpeller blades 34 and the second set ofblades 35 are forward swept because the angle between the outer periphery of theimpeller 32 and the outer side of theimpeller blades -
FIG. 9 illustrates atypical impeller 32 having a number of backwards sweptimpeller blades 34, i.e., the impeller blades are swept or curved against therotational direction 36. It is indicated that therotational direction 36 is counter clockwise—the rotational speed is denoted ω and the radius r of theimpeller 32 is also indicated. The absolute velocity C of the fluid is given by the sum of the tangential velocity U of theimpeller 32 and the relative velocity W relative to theimpeller 32. Theses velocities C, U and W are indicated with arrows. The magnitude of the tangential velocity U of theimpeller 32 is given by the product of the radius r and the rotational speed ω: -
|U|=r·ω (5) - The blade angle β is less than 90 degrees.
-
FIG. 10 illustrates animpeller 32 with a forward sweptimpeller blade 34, i.e., the blades are swept inrotational direction 36. It is indicated that therotational direction 36 is counter clockwise like inFIG. 9 . The projection CU of C in the tangential plane is indicated and it can be seen that this forward swept impeller has the following characteristic: -
CU>U (6) - It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
Claims (14)
1.-12. (canceled)
13. A centrifugal type circulator pump comprising at least one impeller (32), a pump housing and an electrical motor, where the pump has a Q-H pump curve (4) having a head n0 (28) at zero flow and a head, Href (30), corresponding to the highest hydraulic power, wherein Href (30) is greater than H0 (28).
14. The centrifugal pump according to claim 13 , wherein the at least one impeller (32) comprises impeller blades (34) that are shaped in a manner so that that Href (30) is greater than H0 (28).
15. The centrifugal pump according to claim 13 , wherein a first part (8) of the Q-H curve (4) is an increasing function of a flow (6).
16. The centrifugal pump according to claim 13 wherein a last part (10) of the Q-H curve (4) is a decreasing function of a flow (6).
17. The centrifugal pump according to claim 13 wherein the pump housing and/or the impeller (32) is configured to introduce a flow restriction that causes an end part (10) of the Q-H curve (4 ) to be a decreasing function of a flow (6).
18. The centrifugal pump according to claim 13 , wherein the impeller (32) has forward swept blades (34).
19. The centrifugal pump according to claim 13 , wherein the motor is a synchronous motor.
20. The centrifugal pump according to claim 13 , wherein the centrifugal pump is a wet-runner type pump.
21. The centrifugal pump according to claim 13 , wherein the motor is a line start permanent magnet motor.
22. The centrifugal pump according to claim 14 , wherein the impeller blades (34) are arced and distributed symmetrically along a periphery of an impeller plate (48).
23. The centrifugal pump according to claim 13 , wherein the impeller (32) comprises a first set of impeller blades (34) and a second set of impeller blades (35), where the first set of impeller blades (34) are longer than the second set of impeller blades (35) and where the first set of impeller blades (34) and the second set of impeller blades (35) are distributed alternately along a periphery of an impeller plate (48).
24. The centrifugal pump according to claim 13 wherein (⅔)·Href≧H0.
25. The centrifugal pump according to claim 13 , wherein (⅗) Href≧H0.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP10008738.6A EP2420678B2 (en) | 2010-08-21 | 2010-08-21 | Centrifugal pump |
EP10008738.6 | 2010-08-21 | ||
PCT/EP2011/061741 WO2012025289A1 (en) | 2010-08-21 | 2011-07-11 | Centrifugal pump |
Publications (1)
Publication Number | Publication Date |
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US20130216407A1 true US20130216407A1 (en) | 2013-08-22 |
Family
ID=43385615
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US13/818,166 Abandoned US20130216407A1 (en) | 2010-08-21 | 2011-07-11 | Centrifugal pump |
Country Status (5)
Country | Link |
---|---|
US (1) | US20130216407A1 (en) |
EP (1) | EP2420678B2 (en) |
CN (1) | CN103069171B (en) |
RU (1) | RU2556153C2 (en) |
WO (1) | WO2012025289A1 (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20130204546A1 (en) * | 2012-02-02 | 2013-08-08 | Ghd Pty Ltd. | On-line pump efficiency determining system and related method for determining pump efficiency |
US20140209275A1 (en) * | 2013-01-28 | 2014-07-31 | Ebm-Papst Mulfingen Gmbh & Co. Kg | Ventilation Device, In Particular For Heating, Cooling, and/or Humidifying Air In Residential Buildings |
US20150240801A1 (en) * | 2014-02-25 | 2015-08-27 | Askoll Holding S.r.I. a socio unico | Enhanced method for controlling a pumping station within a fluid circulation system, related circulation system and pumping station for realizing said method |
EP3382888A1 (en) * | 2017-03-31 | 2018-10-03 | Grundfos Holding A/S | Pump assembly and controlling method |
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JPH08275600A (en) | 1992-01-09 | 1996-10-18 | Tomiko Kikukawa | Ac communication information system (ac is an abbreviation for alive computer and refers to the force of a computer which is alive,glows and evolves.this force contributes to the implementation of a computer system which is fully automatic,has mind and life,is alive,thinks and moves in theworld of soft media.ac communication system is the system constructed by means of the force.) |
ES2080968T3 (en) | 1992-01-17 | 1996-02-16 | Siemens Ag | WET ROTOR PUMP. |
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2010
- 2010-08-21 EP EP10008738.6A patent/EP2420678B2/en not_active Not-in-force
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2011
- 2011-07-11 US US13/818,166 patent/US20130216407A1/en not_active Abandoned
- 2011-07-11 WO PCT/EP2011/061741 patent/WO2012025289A1/en active Application Filing
- 2011-07-11 CN CN201180040484.7A patent/CN103069171B/en not_active Expired - Fee Related
- 2011-07-11 RU RU2013112610/06A patent/RU2556153C2/en active
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US5127800A (en) * | 1984-03-20 | 1992-07-07 | Baker Hughes Incorporated | Flow-stabilizing volute pump and liner |
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Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20130204546A1 (en) * | 2012-02-02 | 2013-08-08 | Ghd Pty Ltd. | On-line pump efficiency determining system and related method for determining pump efficiency |
US20140209275A1 (en) * | 2013-01-28 | 2014-07-31 | Ebm-Papst Mulfingen Gmbh & Co. Kg | Ventilation Device, In Particular For Heating, Cooling, and/or Humidifying Air In Residential Buildings |
US9932990B2 (en) * | 2013-01-28 | 2018-04-03 | Ebm-Papst Mulfingen Gmbh & Co. Kg | Ventilation device, in particular for heating, cooling, and/or humidifying air in residential buildings |
US20150240801A1 (en) * | 2014-02-25 | 2015-08-27 | Askoll Holding S.r.I. a socio unico | Enhanced method for controlling a pumping station within a fluid circulation system, related circulation system and pumping station for realizing said method |
US9970433B2 (en) * | 2014-02-25 | 2018-05-15 | Taco Italia S.R.L. | Enhanced method for controlling a pumping station within a fluid circulation system, related circulation system and pumping station for realizing said method |
EP3382888A1 (en) * | 2017-03-31 | 2018-10-03 | Grundfos Holding A/S | Pump assembly and controlling method |
US10367439B2 (en) | 2017-03-31 | 2019-07-30 | Grundfos Holding A/S | Pump assembly and controlling method |
Also Published As
Publication number | Publication date |
---|---|
EP2420678B1 (en) | 2015-02-25 |
WO2012025289A1 (en) | 2012-03-01 |
CN103069171B (en) | 2016-08-03 |
EP2420678B2 (en) | 2018-08-15 |
CN103069171A (en) | 2013-04-24 |
RU2556153C2 (en) | 2015-07-10 |
EP2420678A1 (en) | 2012-02-22 |
RU2013112610A (en) | 2014-09-27 |
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