JP2005264747A - Ejector, its operation method, and refrigerating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ejector and its operation method for minimizing reduction in efficiency of the ejector occurring when the total pressure of a secondary fluid is changed to alienate an operation point from a design point. <P>SOLUTION: In the ejector 10, the secondary fluid is sucked and/or pressurized by jet-stream of a primary fluid. An internal structure 5 is provided at the position opposing to a nozzle 2 discharging the primary fluid. The internal structure 5 has a conical tip directing to the nozzle, and a spindle or a nearly spindle shaped rear continuing from the conical shape. A mixing part 8a of the primary and the secondary fluids and a pressure-recovering part 8b of the mixture fluid are provided in the flow path between a diffuser 1 and the internal structure 5. The conical part of the tip end of the internal structure 5 is enclosed in a nozzle hole 2a of the nozzle 2, and the relative position of the nozzle 2 to the internal structure 5 is variable during the ejector operation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ejector used for vacuum generation, compression, boosting, and the like, an operating method thereof, and a refrigeration system using the ejector.

A conventional ejector includes a nozzle and a diffuser, and sucks a low-pressure secondary fluid by ejecting the primary fluid from the nozzle at a high speed. After the primary fluid and the secondary fluid are mixed, the pressure is increased by the diffuser and discharged. ing. When a refrigeration cycle is configured using such an ejector, an evaporator containing the secondary fluid in a liquid phase is connected to the ejector, and the secondary fluid is evaporated and sucked. The cold generated by the heat of vaporization (latent heat of vaporization) is utilized.
In general, an ejector is designed with components such as a nozzle and a diffuser based on the total pressure of the primary fluid and the secondary fluid and the diffuser outlet pressure.
However, it is assumed that the total pressure of the secondary fluid changes during actual operation. In this case, if the total pressure of the secondary fluid deviates from the design point, the efficiency of the ejector decreases rapidly. This is because the primary fluid is not completely expanded at the nozzle outlet position.

Therefore, for example, Patent Document 1 adopts a method in which the nozzle position is controllable with respect to the throat portion of the diffuser, and the nozzle position is made variable by the total pressure of the secondary fluid. However, this method does not change the cross-sectional area of the nozzle throat and outlet, so the expansion ratio of the primary fluid is the same, and the efficiency of the ejector decreases if the primary fluid stops being fully expanded at the nozzle outlet position. Will be inevitable.
For example, Patent Document 2 is known as another method for changing the expansion ratio of the primary fluid. In this method, a rod-shaped needle extending from the throat to the outlet is provided inside the nozzle, and the opening of the throat and the nozzle outlet are both made variable by adjusting the position of the needle. In other words, a diffuser having a function of mixing a primary fluid and a secondary fluid and recovering the pressure of the mixed fluid is usually designed in a shape suitable for a maximum total flow rate of the primary fluid and the secondary fluid. If the flow rate of the primary fluid is decreased by the opening of the throat as in 2, the total flow rate of the primary fluid and the secondary fluid is significantly reduced, and the passage cross-sectional area of the fluid becomes too large. As a result, vortices and backflows are formed in the diffuser, which increases entropy generation and leaves the ejector efficiency abruptly reduced.

  On the other hand, for example, the ejector disclosed in Patent Document 3 is a technique that suppresses entropy generation and improves ejector efficiency by using a phenomenon of reversible energy exchange between a primary fluid and a secondary fluid called pressure exchange. However, no measures are taken to avoid a decrease in ejector efficiency when the total pressure of the secondary fluid decreases and the operating point deviates from the design point.

JP 2002-130200 A JP 2004-44412 A US Pat. No. 6,138,456

  As described above, the method of controlling the flow rate by changing the cross-sectional area of the throat portion with the nozzle outlet while keeping the diffuser shape constant is accompanied by a significant decrease in the efficiency of the ejector. It is realistic to keep the cross-sectional area of the part constant and to cope with the change in the total pressure of the fluid on the secondary side.

  The present invention has been made from such a viewpoint, and an ejector that minimizes a decrease in ejector efficiency that occurs when the total pressure of the secondary fluid changes and the operating point deviates from the design point. It is intended to provide.

  An ejector according to the present invention is an ejector that sucks and / or pressurizes a secondary fluid by a jet of a primary fluid, and has a conical tip at a position facing a nozzle that ejects the primary fluid. An internal structure having a conical shape and a rear portion having a spindle shape or a shape similar thereto is provided, and the diffuser has a primary fluid / secondary fluid mixing portion and a mixed fluid in a flow path between the inner structure and the diffuser. And a pressure cone of the nozzle, the tip of the internal structure is included in the nozzle outlet, and the relative position between the nozzle and the internal structure is variable during operation. .

  By configuring in this way, the nozzle throat cross-sectional area remains constant and the nozzle outlet cross-sectional area can be controlled to the optimum value, so the total pressure of the secondary fluid changes and the operating point becomes the design point. Even when it deviates, it is possible to suppress a decrease in ejector efficiency and maintain high efficiency.

In the ejector of the present invention, a detector for measuring the pressure, temperature or flow rate of the secondary fluid is provided in the diffuser, and the relative position between the nozzle and the internal structure is variable based on the measured value of the detector. Control means for controlling the driving means is provided.
Since the primary fluid nozzle outlet pressure can be calculated approximately by knowing the total pressure of the primary fluid supply section, the cross-sectional area of the nozzle throat and the nozzle outlet cross-sectional area, the pressure, temperature, or flow rate of the secondary fluid can be measured. By doing so, the pressure of the primary fluid and the pressure of the secondary fluid can be controlled to be equal to each other at the nozzle outlet position.

Further, in the ejector according to the present invention, the tip cone portion of the internal structure may be a bladed rotating body.
The same effect as described above can be obtained even if the tip cone portion of the internal structure is a winged rotor.

According to an ejector operating method of the present invention, when the ejector according to any one of claims 1 to 3 is operated, the pressure of both the fluids when the primary fluid and the secondary fluid come into contact with each other at the nozzle outlet is equalized. And the relative position of the internal structure is controlled.
Even when operating conditions change during operation of the ejector, the ejector efficiency can be kept high by appropriately controlling the relative position between the nozzle and the internal structure.

  Therefore, by configuring the refrigeration cycle using the ejector according to any one of claims 1 to 3, it is possible to improve the efficiency (COP) as a refrigerator.

  As described above, the ejector of the present invention controls the relative position between the nozzle position and the internal structure, so that the primary fluid is always close to full expansion during operation. Ejector efficiency can be kept high. Furthermore, since the cross-sectional area of the nozzle throat is constant, the amount of decrease in the total flow rate of the primary fluid and the secondary fluid can be reduced compared to the method described in Patent Document 2 in which the flow rate of the primary fluid is reduced. Therefore, it is possible to suppress a decrease in ejector efficiency that may occur.

  Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an ejector according to the present invention. FIG. 2 is an enlarged cross-sectional view of the portion A in FIG. 1, that is, the nozzle moving mechanism.
The ejector 10 includes a diffuser 1, a nozzle 2 that is movably provided inside the diffuser 1, an internal structure 5 that is disposed at a position facing the nozzle 2, and that holds a rotating body 4 with blades 3; It is mainly composed of a nozzle guide 6 and a motor 7 for moving the nozzle 2.
The diffuser 1 has an introduction portion 11 on the upstream side, and the nozzle guide 6 is attached in the introduction portion 11. A primary fluid supply unit 12 serving as a primary fluid supply source is connected to the nozzle guide 6 via a primary fluid supply pipe 13. A secondary fluid supply unit 14 that is a supply source of the secondary fluid is connected to the introduction unit 11 of the diffuser 1 through a secondary fluid supply pipe 15. The diffuser 1 is connected to another process, a condenser, the atmosphere, or the like via a mixed fluid outlet pipe 16. The primary fluid supply unit 12 includes, for example, a boiler or a heater, and supplies steam or a primary fluid in a gas phase state to the nozzle 2. The secondary fluid supply unit 14 includes, for example, an evaporator or a vacuum device, and supplies the secondary fluid in a vapor or gas phase state to the diffuser 1.

  Next, an example of a mechanism for changing the relative position between the nozzle 2 and the internal structure 5 is shown in FIG. Here, the nozzle 2 that ejects the primary fluid is provided so as to move linearly with respect to the nozzle guide 6 without rotating. That is, in the configuration example shown in FIG. 2, the nozzle guide 6 is divided into two parts, a front part and a rear part, and a motor housing 20 that houses a motor 7 is attached inside the rear part of the divided nozzle guide 6. The moving means of the nozzle 2 is constituted by a screw mechanism 21 that is rotated by a motor 7 exemplified as a driving means. The screw mechanism 21 is a screw shaft attached to the motor shaft 22 via a coupling 23. 24 and a screw cylinder 26 attached to the nozzle 2 via a fixed stay 25, and the male screw part of the screw shaft 24 and the female screw part in the screw cylinder 26 are screwed together. Further, in order to prevent the nozzle 2 from rotating, a protrusion 27 provided on the nozzle 2 is engaged with a guide groove 28 provided on the inner surface of the divided front portion of the nozzle guide 6 in parallel with the ejector shaft. In FIG. 2, 29 is a seal member mounted between the front part of the divided nozzle guide 6 and the nozzle 2, 30 is a fixing stay of the motor housing 20, 31 is a fixing screw of the motor 7, and 32 is a motor. It is a cable. The fixed stays 25 and 30 are stream-like rod-shaped members that do not hinder the flow of the primary fluid, and are arranged in a plurality of radial directions.

The internal structure 5 described above has a conical rotator 4 on the upstream side, and the downstream portion has a spindle shape or a similar shape to the primary flow passage in the annular flow path between the diffuser 1 and the primary structure. A fluid and secondary fluid mixing portion 8a and a mixed fluid pressure recovery portion 8b are formed. The internal structure 5 is attached to the inside of the diffuser 1 by a plurality of fixed stays 33 made of a streamlined rod-like member.
The conical rotator 4 is rotatably supported by the main body portion of the internal structure 5 by a rotating shaft 34, and the distal end conical portion forming the rotator 4 has a divergent spout 2 a (nozzle outlet) of the nozzle 2. It is arranged so that it may be included. That is, the tip 4a of the conical portion is arranged at or near the nozzle outlet position. A plurality of blades 3 are attached to the rotating body 4 so as to freely rotate. Instead of the conical rotator 4, the tip of the internal structure 5 may be a simple conical portion that does not rotate as shown in FIG.
Furthermore, as shown in FIG. 4, the nozzle 2 may be moved forward or backward by attaching a driving means such as a motor 7 or a hydraulic cylinder to the outer wall surface of the introduction portion 11 of the diffuser 1. By installing the driving means for the nozzle 2 outside the diffuser 1, the nozzle moving mechanism can be easily configured.

  In addition, a pressure gauge 41 that measures the total pressure is attached to the primary fluid supply unit 12, and a pressure gauge 42 that measures the pressure of the secondary fluid is attached to the diffuser 1. The pressure measurement signals from these pressure gauges 41 and 42 are sent to a control means 43 for controlling the operation of the ejector 10, and the control means 43, as will be described later, the pressure of the primary fluid and the secondary fluid at the nozzle outlet position. The motor 7 is controlled so that the pressures are equal.

FIG. 3 is a block diagram showing an example of this control system. Since the Mach number at the nozzle outlet can be approximately calculated from the flow passage cross-sectional area of the nozzle throat 2b and the flow passage cross-sectional area of the nozzle outlet 2a, the pressure of the primary fluid at the nozzle outlet is determined by the Mach number at the nozzle outlet and the primary fluid supply unit 12. It can be calculated from the total pressure. The flow path cross-sectional area of the nozzle outlet can be changed depending on the relative position between the nozzle 2 and the internal structure 5 because the internal structure 5 is included in the nozzle 2, and the value is the tip of the internal structure. It is expressed as a function of the part shape and the nozzle position.
On the other hand, the pressure of the secondary fluid is measured by the pressure gauge 42 shown in FIG. The pressure gauge 42 is usually fixed at a certain point. When the nozzle position is variable, the measurement point does not always coincide with the nozzle outlet position, so the measured pressure value needs to be corrected to the value at the nozzle outlet position. The correction of the pressure at the pressure measurement point and the nozzle outlet position assumes that the flow between them is isentropic, the total pressure of the secondary fluid, the position of the nozzle and the inlet of the secondary fluid (here, the constriction of the diffuser 1) It can be corrected by calculation from the cross-sectional area of the secondary fluid obtained from the shape of the part 1a) and the specific heat ratio of the primary and secondary fluids. Alternatively, since the relative displacement between the nozzle outlet position and the pressure measurement point is usually small, there is no problem even if the pressure at the nozzle outlet position is approximated by the pressure measurement point.

  As shown in FIG. 3, a control signal is sent to the motor 7 so that the approximate calculated value of the pressure of the primary fluid at the nozzle outlet becomes the target value with the measured value of the pressure of the (corrected) secondary fluid as a target value. Perform feedback control to output and adjust nozzle position. Specifically, when the pressure of the secondary fluid (corrected) is higher than the nozzle outlet pressure obtained by calculation of the primary fluid, in order to reduce the expansion of the primary fluid in the nozzle, the nozzle 2 is connected to the internal structure. When the corrected pressure of the secondary fluid is lower than the nozzle outlet pressure obtained by the calculation of the primary fluid, the opposite is true and the nozzle 2 is moved away from the internal structure 5.

Next, the operation of the ejector 10 will be described. The primary fluid supplied from the primary fluid supply unit 12 into the nozzle guide 6 through the primary fluid supply pipe 13 passes through the annular flow path between the motor housing 20 and the nozzle guide 6, and further flows between the nozzle 2 and the screw cylinder 26. It passes through the path and jets at a higher speed than the jet outlet 2a at the tip of the nozzle 2. The secondary fluid is sucked into the diffuser 1 by the negative pressure due to the ejection of the primary fluid. The primary fluid and the secondary fluid are mixed in the mixing portion 8a between the diffuser 1 and the internal structure 5, and further, the velocity energy is converted into pressure energy and flows out while passing through the pressure recovery portion 8b.
At this time, if the operating point of the ejector 10 deviates from the design point due to a change in the total pressure of the secondary fluid, the ejector efficiency is remarkably lowered. Therefore, the nozzle moving mechanism is operated to adjust the nozzle outlet position. That is, in this nozzle moving mechanism, the nozzle 2 is a nozzle that engages with the guide groove 28 of the nozzle guide 6 and the groove 28 by rotating the screw shaft 24 attached via the coupling 23 by the rotation of the motor shaft 22. 2, the screw cylinder 26 screwed into the screw shaft 24 can be linearly advanced or retreated, whereby the nozzle 2 is made into the conical rotor 4 of the internal structure 5. It can be moved forward or backward.
Therefore, the flow passage cross-sectional area of the nozzle throat portion 2b remains constant, and the flow passage cross-sectional area of the primary fluid of the nozzle outlet 2a can be changed to an optimum value. It is possible to control so that the pressure is always equal.

  Therefore, according to the ejector 10, the relative position between the position of the nozzle 2 from which the primary fluid is ejected and the tip cone portion of the internal structure 5 disposed at a position facing the nozzle 2 is variable. Because the nozzle throat cross-sectional area remains constant and the flow path cross-sectional area of the nozzle outlet can be appropriately varied, the total operating pressure of the secondary fluid changes during operation of the ejector. Even in this case, it is possible to control so that the pressures of both the fluids at the time of contact between the primary fluid and the secondary fluid at the nozzle outlet are equal (complete expansion), so it is possible to easily suppress a decrease in ejector efficiency. High efficiency can always be maintained.

In the above description, a pressure gauge is assumed as the detector, but a thermometer may be used instead of the pressure gauge. Further, the flow rate of the secondary fluid may be measured without measuring the pressure and temperature, and control may be performed so that this value becomes maximum.
Furthermore, the nozzle 2 may be fixed and the internal structure 5 may be variable. In this case, since the detector can be installed on the nozzle outlet cross section, there is no need to correct the pressure of the secondary fluid.

FIG. 5 is a schematic diagram showing an example of an embodiment in which a refrigeration cycle is configured using the ejector of the present invention.
Here, the ejector 10, the nozzle moving mechanism, and the control device shown in FIGS. 1 to 3 are used. Further, the primary fluid supply unit includes a heater 51, and the heater 51 is connected to the nozzle guide 6 via the primary fluid supply pipe 13. The secondary fluid supply unit includes an evaporator 52, and the evaporator 52 is connected to the introduction unit 11 of the diffuser 1 through the secondary fluid supply pipe 15. The mixed fluid outlet pipe 16 is connected to the condenser 53. A pipe 54 connecting the heater 51 and the condenser 53 is provided with a primary fluid supply control device 55 such as a pump or an electromagnetic valve. The evaporator 52 and the condenser 53 are connected via a pressure reducing valve 56. The secondary fluid return pipe 57 is connected.
The mixture of the primary fluid and the secondary fluid flowing into the condenser 53 is cooled by a cooling water pipe 58 connected to the condenser 53 and condensed. The condensed liquid flows through the pipe 54 and is returned to the heater 51 by the primary fluid supply device 55, and at the same time returns to the evaporator 52 via the secondary fluid return pipe 57 and the pressure reducing valve 56.
A temperature drop, that is, refrigeration occurs due to vaporization heat (latent heat of evaporation) of the secondary fluid generated when the secondary fluid in the evaporator 52 is sucked by the ejector 10, and a cold load 59 connected to the evaporator 52. Cool down.

  By using the ejector 10 described above, even when the operating condition of the ejector 10 changes during the operation of the refrigerator, the relative position between the nozzle 2 and the internal structure 5 is optimally controlled without reducing the ejector efficiency. Since it can be kept highly efficient, the efficiency (COP) as a refrigerator is improved.

In addition, as a heat source of the heat exchanger 60 connected to the primary fluid heater 51, factory exhaust heat, exhaust gas heat, and the like are used in addition to power and fuel combustion. As the primary and secondary fluid refrigerant, water, chlorofluorocarbon, alcohol, ammonia, CO ₂ , hydrocarbon refrigerant, or a mixture thereof can be used.

The schematic diagram which shows the structural example of the ejector of this invention. The expanded sectional view of the A section of FIG. The block diagram which shows an example of a control system. The schematic diagram which shows another structural example of the ejector of this invention. The schematic diagram of the refrigerating system of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diffuser, 2 nozzle, 3 blades, 4 rotator, 5 internal structure, 6 nozzle guide, 7 motor, 8a mixing part, 8b pressure recovery part, 10 ejector, 11 introduction part, 12 primary fluid supply part, 13 primary fluid Supply piping, 14 Secondary fluid supply section, 15 Secondary fluid supply piping, 16 Mixed fluid outflow piping, 21 41, 42 Pressure gauge, 43 Control means, 51 Heater, 52 Evaporator, 53 Condenser

Claims (5)

In an ejector that sucks and / or pressurizes a secondary fluid by a jet of the primary fluid,
At the position facing the nozzle that ejects the primary fluid, the tip part facing the nozzle side has a conical shape, and an internal structure in which the rear part is formed in a spindle shape or a similar shape to the conical shape is provided.
The diffuser has a primary fluid and secondary fluid mixing portion and a mixed fluid pressure recovery portion in a flow path between the inner structure and the inner structure.
The tip cone of the internal structure is included in the nozzle outlet,
An ejector characterized in that the relative position between the nozzle and the internal structure is variable during operation.   A control for providing a detector for measuring the pressure, temperature or flow rate of the secondary fluid in the diffuser, and for controlling the driving means for changing the relative position between the nozzle and the internal structure based on the measured value of the detector. The ejector according to claim 1, further comprising means.   The ejector according to claim 1, wherein a tip cone portion of the internal structure is a rotating body with a blade.   When operating the ejector according to any one of claims 1 to 3, the relative position between the nozzle and the internal structure so that the pressures of both the fluids when the primary fluid and the secondary fluid are in contact with each other at the nozzle outlet are equalized. A method of operating an ejector, characterized in that control is performed. A refrigeration system comprising a refrigeration cycle using the ejector according to any one of claims 1 to 3.

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