JP2019127827A - Turbo compressor - Google Patents

Abstract

To eliminate a disadvantage at a turbo compressor that a surging cannot be detected when a high-low pressure difference in a refrigeration cycle is low.SOLUTION: This invention relates to a turbo compressor comprising an impeller 7 for use in compressing working fluid; a rotor 5 having a revolving shaft 6 rotated in integration with said impeller; a casing 9 having a casing wall surface 9a oppositely facing against a back surface of said impeller 7 constituted to form a first space 18a between said casing wall surface 9a and the back surface of said impeller 7; a first pressure sensor 14 for use in detecting a pressure at said first space 18a; and a control unit 15 for use in judging occurrence of surging on the basis of a detected value of said first pressure sensor 14.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a turbomachine.

  In the heat pump cycle and the refrigeration cycle apparatus, a turbo compressor that increases the pressure of the refrigerant by the rotational kinetic energy is used. The turbo compressor has a restriction on the relationship between the flow rate and the pressure ratio. When the rotation speed is constant, the pressure ratio increases when the flow rate is reduced by restricting the discharge valve. A phenomenon or surging occurs. When surging occurs, the rotating shaft may vibrate abnormally and the bearings may be damaged. Generally, the surging generation limit flow rate has a characteristic of increasing with the rotational speed, and the turbo compressor is usually operated so as to avoid a surging generation region on the flow rate side smaller than the surging generation limit flow rate.

  However, in actual operation, it is assumed that surging will occur unintentionally. For this reason, the controller of the turbo compressor has a surging detection device, and when detecting the occurrence of surging, there has been a technique for changing the operating condition in a direction away from the surging occurrence region such as a decrease in the rotational speed.

  FIG. 4 shows a surging detection device described in Patent Document 1. The pressure detector 101 detects a pressure drop in the discharge pipe 102, the surging determining circuit 103 determines surging, and the prevention device 104 is activated. FIG. 5 shows the judgment principle of surging described in Patent Document 1. In FIG. The curve c is an example in which surging occurs. In this case, since the rapid pressure drop Δp occurs at least twice within a preset time ΔT1, the surging determination circuit 103 in FIG. It is determined that the automatic escape signal is output from surging and the prevention device 104 is activated.

Japanese Patent Publication No. 58-15639

  However, in the technology described in Patent Document 1, when the high / low pressure difference in the refrigeration cycle is small, such as low outside air temperature cooling operation or operating conditions with low operating pressure due to refrigerant type, high pressure side when refrigerant flows back from high pressure side at surging occurrence The liquid refrigerant accumulated in the refrigerant evaporates and changes its phase, but the heat capacity on the high pressure side is large, so the temperature change on the high pressure side is small, and the ambient pressure change on the high pressure side pressure sensor is too small to detect surging There was a problem.

  The present disclosure is a new method capable of highly accurately determining the occurrence of surging in a turbo compressor even when the high / low pressure difference in the refrigeration cycle is small, such as a low outside air temperature cooling operation or an operating condition with low operating pressure due to refrigerant types. Provide technology.

The first aspect of the present disclosure is:
An impeller for compressing the working fluid;
A rotating body having a rotating shaft that rotates integrally with the impeller;
A casing having a casing wall surface facing the back surface of the impeller, and a casing configured to form a first space between the casing wall surface and the back surface of the impeller;
A first pressure detector for detecting the pressure in the first space;
A controller that determines the occurrence of surging based on a detection value of the first pressure detector;
A turbo compressor including the above is provided.

The second aspect of the present disclosure is:
An impeller for compressing the working fluid;
A rotating body having a rotating shaft that rotates integrally with the impeller;
A casing wall surface facing the back surface of the impeller, a first space formed between the casing wall surface and the back surface of the impeller, and in communication with the first space via a region through which the rotating body penetrates; A casing configured to form two spaces;
A second pressure detector for detecting the pressure in the second space;
A controller that determines the occurrence of surging based on the detection value of the second pressure detector;
A turbo compressor including the above is provided.

  Even when the difference between the high and low pressures of the refrigeration cycle is small, such as the low outside temperature cooling operation or the operation condition where the operating pressure is low depending on the type of refrigerant, it is possible to accurately determine whether surging has occurred in the turbo compressor.

1 is a configuration diagram of a refrigeration cycle apparatus according to Embodiment 1. FIG. 1 is a cross-sectional view of a turbo compressor according to Embodiment 1. FIG. It is a comparison chart of pressure time series data in surging. It is a block diagram of the surging detection apparatus of patent document 1. FIG. It is explanatory drawing about the judgment principle of the surging detection apparatus of patent document 1. FIG.

<Knowledge based on studies by the present inventors>
It is conceivable to use a turbocompressor to increase the pressure of the working fluid by means of the kinetic energy of rotation in large heat pump cycles and refrigeration cycle units. In order to operate the turbo compressor properly, the relationship between the flow rate of the working fluid and the pressure ratio in the turbo compressor has certain limitations.

  When the rotation speed of the impeller is constant in the turbo compressor, the pressure ratio increases when the flow rate of the working fluid is reduced by restricting the valve (discharge valve) for adjusting the flow rate of the working fluid in the discharge flow path. In this case, when the flow rate of the working fluid is less than a predetermined value, a periodic backflow phenomenon of the working fluid, that is, surging occurs. If surging occurs in the turbo compressor, the rotating shaft may vibrate abnormally and the bearing may be damaged. In addition, since a part of the hot gas in the discharge side space in the turbo compressor flows into the suction side space, the temperature of the working fluid sucked into the impeller rises.

  The critical value of the working fluid flow rate at which surging occurs increases as the rotational speed of the impeller increases. Therefore, the turbo compressor is typically operated so that the flow rate of the working fluid does not fall below the critical value of the working fluid flow rate at which surging occurs. However, in the actual operation of the turbo compressor, surging may occur unintentionally. For this reason, as in the technology described in Patent Document 1, incorporating a surging detection device into the turbo compressor and changing the operating conditions of the turbo compressor so that the surging is eliminated when the occurrence of the surging is detected. Is considered.

  However, depending on the conditions, pressure fluctuation or temperature fluctuation of the working fluid when surging occurs may be small. For example, if the working fluid has a saturated vapor pressure that is lower than the atmospheric pressure at normal temperature (20 ° C. ± 15 ° C .: Japanese Industrial Standard JIS Z 8703), or if mild surging occurs, surging has occurred. Sometimes the pressure fluctuation or temperature fluctuation of the working fluid tends to be small. In this case, it may be possible to set the working fluid pressure threshold low to determine whether surging has occurred, but it may exceed that threshold even in normal operation where surging has not occurred. Will be detected incorrectly. Further, if the threshold value of the working fluid pressure for determining whether surging has occurred or not is set high, surging may not be detected even if surging actually occurs. In this case, the operation of the turbo compressor is continued in the state where the surging has occurred, and there is a possibility that the rotating shaft abnormally vibrates to damage the bearing.

  Therefore, the present inventors have attempted to develop a technology capable of determining the presence or absence of surging with high accuracy even when the pressure fluctuation of the working fluid when surging occurs is small in the turbo compressor. Specifically, the present inventors made a prototype of a turbo compressor using a working fluid having a saturated vapor pressure lower than the atmospheric pressure at an ordinary pressure at normal temperature. In addition, the present inventors have conducted day and night studies on a technology capable of operating the turbo compressor under conditions where surging occurs and determining the presence or absence of surging with high accuracy. As a result of the study, the present inventors have newly found that a change in pressure of the refrigerant flowing into the impeller back space is largely detected when surging occurs. Based on such new findings, the present inventors have devised the turbo compressor of the present disclosure. In addition, said knowledge is knowledge based on examination of the present inventors, and does not admit as prior art.

The first aspect of the present disclosure is:
An impeller for compressing the working fluid;
A rotating body having a rotating shaft that rotates integrally with the impeller;
A casing having a casing wall surface facing the back surface of the impeller, and a casing configured to form a first space between the casing wall surface and the back surface of the impeller;
A first pressure detector for detecting the pressure in the first space;
A controller that determines the occurrence of surging based on a detection value of the first pressure detector;
A turbo compressor including the above is provided.

The second aspect of the present disclosure is:
An impeller for compressing the working fluid;
A rotating body having a rotating shaft that rotates integrally with the impeller;
A casing wall surface facing the back surface of the impeller, a first space is formed between the casing wall surface and the back surface of the impeller, and the first space communicates with the first space through a region through which the rotating body passes. A casing configured to form two spaces;
A second pressure detector for detecting the pressure in the second space;
A controller that determines the occurrence of surging based on the detection value of the second pressure detector;
A turbo compressor including the above is provided.

  According to the present disclosure, when a constant refrigerant flows back from the high pressure side at the time of surging occurrence, the refrigerant flowing into the impeller rear space does not undergo a phase change, so that a pressure change around the pressure detector is largely detected. Therefore, even when the difference between the high and low pressures of the refrigeration cycle is small, such as the low outside air temperature cooling operation or the operation condition where the operating pressure is low depending on the refrigerant type, the presence or absence of surging can be determined with high accuracy.

  Hereinafter, embodiments of the present disclosure will be described with reference to FIGS. 1 to 3. The following embodiments are merely examples of the present invention, and the present invention is not limited thereto.

<Embodiment 1>
FIG. 1 shows a configuration diagram of a refrigeration cycle apparatus according to a first embodiment.

  The refrigeration cycle apparatus 1 includes an evaporator 3, a turbo compressor 2, and a condenser 4. The refrigeration cycle apparatus 1 constitutes, for example, an air conditioner dedicated to cooling. The working fluid (refrigerant) used in the refrigeration cycle apparatus 1 is not particularly limited, and is, for example, a fluid containing water, alcohol, or ether as a main component.

  The turbo compressor 2 increases the pressure of the refrigerant by applying energy to the refrigerant by the rotation of the impeller (impeller).

  The evaporator 3 includes, for example, a container having heat insulation and pressure resistance. The evaporator 3 stores the refrigerant liquid and evaporates the refrigerant inside the container by exchanging heat with the outside. The temperature of the refrigerant liquid stored in the evaporator 3 and the temperature of the refrigerant vapor generated in the evaporator 3 are 5 ° C., for example. The evaporator 3 may be an indirect heat exchanger in which the refrigerant liquid and other heat medium indirectly exchange heat, such as a shell tube heat exchanger, or a spray type or a filler type. Such a direct contact type heat exchanger may be used.

  The condenser 4 includes, for example, a container having heat insulating properties and pressure resistance. The condenser 4 stores the refrigerant liquid and condenses the refrigerant vapor inside by exchanging heat with the outside. The temperature of the refrigerant vapor introduced into the condenser 4 is 100 ° C. to 150 ° C., and the temperature of the refrigerant liquid condensed in the condenser 4 is, for example, 35 ° C. Further, the condenser 4 may be an indirect heat exchanger in which the refrigerant and other heat medium indirectly exchange heat, such as a shell tube heat exchanger, or a spray type or a filler type. It may be a direct contact type heat exchanger.

  FIG. 2 shows a cross-sectional view of the turbo compressor 2 according to the first embodiment.

  The turbo compressor 2 includes a rotating body 5, a volute 8, a casing 9, a bearing device 10, a motor 11, an in-compressor suction space 16, an in-compressor discharge space 17, and an impeller back space 18.

  The rotating body 5 is composed of a rotating shaft 6 and an impeller 7.

  The rotation shaft 6 is, for example, a cylindrical member extending horizontally. The rotating shaft 6 rotates the impeller 7 by rotating at a high speed. The rotation speed of the rotating shaft 6 is, for example, 5000 rpm to 100000 rpm. The rotating shaft 6 is made of a high strength iron-based material such as S45CH.

  The impeller 7 is connected to the rotating shaft 6 and rotates at high speed. The rotation speed of the impeller 7 is, for example, 5000 rpm to 100 000 rpm. The impeller 7 is made of, for example, aluminum, duralumin, iron, ceramic or the like, and gives the refrigerant vapor a rotational speed.

  The volute 8 is a part that forms a discharge space 17 for collecting refrigerant vapor discharged from the impeller 7. The discharge space 17 is configured such that the flow velocity and the angular momentum become constant by the cross-sectional area expanding in the circumferential direction. The volute 8 is made of an iron-based material such as FC250, FCD400, or SS400, or an aluminum-based material such as ACD12.

  The casing 9 is a member that acts as a casing of the compressor, or a member that constitutes a flow path of the vaneless diffuser. The casing 9 is made of an iron-based material such as FC 250 or FCD 400 or SS 400 or an aluminum-based material such as ACD 12.

  The bearing device 10 is a fluid-lubricated bearing that supports at least the radial load of the rotating shaft 6. As the lubricant, a fluid containing the same main component as the main component of the refrigerant is used.

  The motor 11 includes a rotor 12 and a stator 13. The rotor 12 is a cylindrical member and is shrink-fit to the rotating shaft 6. The stator 13 is installed on the outer peripheral side of the rotor 12 with a certain clearance, and the outer peripheral side is fixed by the casing 9. The casing 9 is fixed to the volute 8.

  The compressor intake space 16 is a steam flow path for supplying the refrigerant vapor sucked by the compressor 2 to the impeller 7.

  The discharge space 17 in the compressor is a steam flow path for discharging the discharged refrigerant vapor from the outlet of the compressor 2.

  The impeller back surface space 18 sandwiches the impeller back surface 7a among the first space 18a formed between the impeller back surface 7a and the casing wall surface 9a facing the impeller back surface 7a, and the space communicating with the first space 18a. It is comprised by the 2nd space 18b formed in the opposite side to the suction space 16 in a compressor. The second space 18b is, for example, a space that communicates with the first space 18a via a region 19 (shaft penetrating portion) through which the rotating shaft 6 passes. The second space 18b may be a space in which the electric motor 11 is accommodated. The impeller back space 18 may be a closed space. The first space 18 a of the impeller back space 18 may have a narrowed portion narrower than the orifice or gap. The aperture or clearance of the throttle portion is, for example, 10% to 60% of the gap between the impeller back surface 7a and the casing wall surface 9a facing the impeller back surface 7a.

  The surging detection device includes a pressure detector 14 that detects the pressure in the impeller back space 18 and a controller 15 that calculates the output signal of the pressure detector 14 and determines surging.

  The pressure detector 14 is installed in the casing 9 and electrically connected to the controller 15. The pressure detector 14 includes a first pressure detector 14a that detects the pressure in the first space 18a and / or a second pressure detector 18b (not shown) that detects the pressure in the second space 18b.

  The following operations and effects of the refrigeration cycle apparatus 1, the turbo compressor 2, and the surging detection apparatus configured as described above will be described.

  The inside of the refrigeration cycle apparatus 1 is equalized and pressure-equalized to approximately room temperature when it is left for a fixed period (for example, at night). First, when the turbo compressor 2 is started, the pressure of the refrigerant vapor in the evaporator 3 is reduced, and the refrigerant vapor is generated by absorbing heat from the outside air. The refrigerant vapor generated in the evaporator 3 is sucked, compressed, and discharged into the turbo compressor 2. The high-pressure refrigerant vapor discharged from the turbo compressor 2 is introduced into the condenser 4 and is condensed by radiating heat to the outside air to become a refrigerant liquid. The refrigerant liquid generated in the condenser 4 is returned to the evaporator 3 through a pipe line.

  As described above, the refrigeration cycle apparatus 1 realizes, for example, an air conditioner dedicated to cooling by a series of operations of the evaporator 3, the turbo compressor 2, and the condenser 4.

  In the turbo compressor 2, the rotary shaft 6 and the impeller 7 rotate by the operation of the motor 11. Thus, the refrigerant vapor flows into the compressor suction space 16 and is introduced into the impeller 7. The impeller 7 introduces refrigerant vapor from the compressor intake space 16 by the rotation of the rotating shaft 6 and compresses the refrigerant vapor. The compressed refrigerant vapor is discharged to the condenser 4 through the discharge space 17 in the compressor.

  When surging occurs, gas flows into the impeller back space 18 from the flow path between the back surface of the impeller and the wall surface of the casing.

  The surging detection device includes the pressure detector 14, and determines that the surging occurs when the rate of change of the impeller back space pressure exceeds a reference value (for example, 0.15 to 0.6 kPa / sec). In order to perform the surging avoidance operation, the controller 15 reduces the frequency of the rotating magnetic field applied to the stator 12 and decreases the rotating frequency of the rotating body 5. However, the means for the surging avoidance operation is selected not only according to the decrease in the rotational speed, but also according to the control means provided in the turbo compressor, such as an inlet guide valve and a discharge valve (bypass valve).

  If surging is not detected again within a certain time (for example, 1 min) after the avoidance operation is started, the avoidance operation is terminated and the normal operation is resumed. If surging is detected again during avoidance operation, the operation condition is changed in a direction away from the surging occurrence area and avoidance operation is continued, and if surging is not detected again within a predetermined time (for example, 1 min), avoidance operation is ended and normal Return to driving.

  FIG. 3 is an example of pressure time-series data in surging.

  When surging occurs, steam flows back from the high pressure side and the pressure on the high pressure side decreases, but the heat capacity on the high pressure side is large and the liquid accumulated in the condenser 4 evaporates, so the pressure change around the pressure detector is small (For example, change rate 0.09 kPa / sec).

  When surging occurs, steam flows back from the high pressure side, and the pressure on the low pressure side rises, but the heat capacity on the low pressure side is large, and the vapor that has flowed back flows condenses in the evaporator 3, so the pressure change around the pressure detector is small ( For example, the rate of change is 0.03 kPa / sec).

  Under normal conditions, the impeller back space pressure is lower than the pressure on the high pressure side because it is equal to the static pressure due to the centrifugal force action and the diffuser action of the impeller 7. When surging occurs, a certain amount of steam flows back from the high pressure side to increase the pressure in the impeller rear space. The impeller back space is closed or the flow is stopped by the throttle. In addition, since the heat capacity is small and the inflowing gas is not condensed, a large pressure change around the pressure detector is detected (for example, a change rate of 0.23 kPa / sec).

  As described above, in the present embodiment, surging can be detected even when the high / low pressure difference in the refrigeration cycle is small and can not be detected by the high pressure side discharge pipe, such as a low outside air temperature cooling operation or an operating condition with low operating pressure due to refrigerant types. .

  The turbo compressor of the present disclosure is useful for a heat pump, a refrigerator and an air conditioner.

Reference Signs List 1 refrigeration cycle apparatus 2 turbo compressor 3 evaporator 4 condenser 5 rotating body 6 rotating shaft 7 impeller 7a impeller back 8 volute 9 casing 9 a wall surface facing the impeller back 10 bearing device 11 electric motor 12 rotor 13 stator 14 pressure detection Unit 15 Controller 16 Compressor internal suction space 17 Compressor internal discharge space 18 Impeller rear space

Claims (3)

An impeller for compressing the working fluid;
A rotating body having a rotating shaft that rotates integrally with the impeller;
A casing having a casing wall surface facing the back surface of the impeller, the casing being configured to form a first space between the casing wall surface and the back surface of the impeller;
A first pressure detector for detecting the pressure in the first space;
A controller that determines the occurrence of surging based on a detection value of the first pressure detector;
Equipped with a turbo compressor. An impeller for compressing the working fluid;
A rotating body having a rotating shaft that rotates integrally with the impeller;
A casing wall surface facing the back surface of the impeller, a first space is formed between the casing wall surface and the back surface of the impeller, and the first space communicates with the first space through a region through which the rotating body passes. A casing configured to form two spaces;
A second pressure detector for detecting the pressure in the second space;
A controller that determines the occurrence of surging based on the detection value of the second pressure detector;
Equipped with a turbo compressor.   The turbo compressor according to claim 1 or 2, wherein an evaporator which evaporates a refrigerant liquid to generate refrigerant vapor, and suctions, compresses and discharges the refrigerant vapor generated by the evaporator, and the turbo compressor And a condenser for introducing the refrigerant vapor and generating a refrigerant liquid.