CN115217775B - A Mixed Flow-Centrifugal Combined Centrifugal Compressor with Diffuser Reflux - Google Patents

Abstract

The invention discloses a mixed-flow-centrifugal combined centrifugal compressor with a diffuser reflux device, comprising a mixed-flow stage, a centrifugal stage and a motor, the outlet of the first-stage mixed-flow impeller and the inlet of the first-stage diffuser The outlet of the first-stage diffuser is connected to one end of the first-stage bend, the other end of the first-stage bend is connected to the inlet of the first-stage reflux device, and the outlet of the first-stage reflux device is connected to the second-stage The inlet of the impeller is connected, the outlet of the second stage impeller is connected to the inlet of the second diffuser, the outlet of the second diffuser is connected to one end of the second bend, the other end of the second bend is connected to the second gas connected to the inlet of the collector. The invention can solve the problems of excessive size, high cost and low efficiency of the compressor in the field of refrigeration and air conditioning using water as the refrigerant.

Description

A Mixed Flow-Centrifugal Combined Centrifugal Compressor with Diffuser Reflux

technical field

The patent relates to a coaxial multistage centrifugal compressor, in particular to a mixed-flow-centrifugal combined centrifugal compressor with a diffuser reflux device, which belongs to the technical field of centrifugal compressors.

Background technique

The coaxial multi-stage centrifugal compressor is used for gas transportation and pressure increase. In this compressor, the main components are the impeller and the diffuser and reflux device matched with it. In this compressor, the medium enters the next stage through the blades of the upper stage, diffusers, bends and reflux. At present, the impellers of each stage of the compressor are mostly centrifugal impellers, which leads to a relatively large radial dimension of the multi-stage centrifugal compressor, resulting in a large volume, heavy weight, high cost and a large footprint of the compressor. There are also problems with the use of centrifugal impellers, including that the flow capacity of the impeller is not as good as that of the mixed flow type, and the efficiency is not as good as that of the mixed flow type.

In the case of refrigeration with water as the working medium, the working medium of the compressor is water vapor at 7-12°C, and the gas density is 0.0077566-0.01067kg/m ³ . Since each stage of the machine adopts a centrifugal impeller, the radial dimension of the coaxial multi-stage centrifugal compressor for water vapor refrigeration will be very large. Taking the cooling capacity of 400kw as an example, the outer diameter of the compressor can reach 1400mm . In view of the above problems, the mixed-flow impeller is used in the first stage of the two-stage centrifugal compressor in the present invention, which can reduce the radial size, improve the flow capacity and improve the efficiency, so that it can meet the use occasions of large flow and small machine size.

After the air flow from the first-stage mixed-flow impeller passes through the diffuser and the bend, the flow rate of the gas is still relatively high, and the kinetic energy in it needs to be further converted into static pressure. The present invention proposes a reflux device with diffuser capability. The inlet flow area of the reflux device is smaller than the outlet flow area, so that the aerodynamic kinetic energy will be further converted into static pressure, so the radial size of the diffuser can be reduced.

Because the reflux device has a pressure-diffusing effect, if a traditional binary vane reflux device is used, the airflow will inevitably be separated and the flow loss will increase. The compressor of the present invention adopts arbitrarily distorted blades in three-dimensional space designed based on controlling the blade load of the reflux device, so that The radial size of the machine is further reduced on the basis of using the mixed-flow impeller to reduce the radial size.

Contents of the invention

The object of the present invention is to provide a mixed-flow-centrifugal combined centrifugal compressor with a diffuser reflux device and its application.

A mixed flow-centrifugal combined centrifugal compressor with a diffuser reflux device, characterized in that it includes a mixed flow stage, a centrifugal stage and a motor, the mixed flow stage is the first stage, and the centrifugal stage is the second stage; The mixed-flow stage includes the first-stage mixed-flow impeller, the first-stage diffuser, the first-stage bend, and the first-stage reflux device; the centrifugal stage includes the second-stage impeller, the second-stage diffuser, the second-stage bend, and the second-stage gas collection device;

The outlet of the first-stage mixed-flow impeller is connected to the inlet of the first-stage diffuser, the outlet of the first-stage diffuser is connected to one end of the first-stage bend, and the other end of the first-stage bend is connected to the first-stage bend. The inlet of the first-stage reflux is connected, the outlet of the first-stage reflux is connected to the inlet of the second-stage impeller, the outlet of the second-stage impeller is connected to the inlet of the second-stage diffuser, and the outlet of the second-stage diffuser is connected to the inlet of the second-stage diffuser. One end of the bend is connected, and the other end of the secondary bend is connected with the inlet of the secondary gas collector;

The first-stage mixed-flow impeller and the second-stage impeller are connected to the motor through a compressor main shaft;

Both the first-stage mixed-flow impeller and the second-stage impeller are open impellers with splitter blades, and the first-stage mixed-flow impeller and the second-stage impeller are coaxial and in the same direction as the inlet.

Further, the outlet area of the first-stage reflux device is larger than the inlet area, the outlet area of the second-stage gas collector is larger than the inlet area, and the vanes of the first-stage reflux device and the second-stage gas collector are both 3D Arbitrary Space Distortion Blades.

Further, the included angle between the solid wall on the outlet disk side of the first-stage mixed-flow impeller and the axis is 60-85°.

Further, the first-stage diffuser is inclined, the width of the inlet and outlet is consistent, and the included angle between the center line and the axis of the compressor is 60-85°.

Further, the entrance of the first-level curve is inclined, and the included angle with the axis is 5-30°, and the exit of the first-level curve is parallel to the axis.

Further, the outlet width of the first-stage mixed-flow impeller is b2, the outlet diameter of the first-stage mixed-flow impeller is D2, and b2/D2 is 0.08-0.1.

Further, the first-stage mixed-flow impeller adopts three-dimensional arbitrary space blades.

Further, the first-stage mixed-flow impeller is a splitter blade, the splitter blade on the disk side is located at 10%-20% of the total flow channel length, and the splitter vane at the cover side is located at 15%-25% of the total flow channel length.

Further, the rotor of the motor, the first-stage mixed-flow impeller, and the second-stage impeller together constitute the rotor of the compressor, the motor has no bearing, the support of the motor is a single cantilever support, and the support of the rotor of the compressor is Magnetic suspension bearings distributed at both ends and composite bearings with bidirectional thrust bearings.

The application of the above-mentioned mixed-flow-centrifugal combined centrifugal compressor with a diffuser reflux device in a refrigeration air conditioner using water as a refrigerant.

The working method of the centrifugal compressor of the present invention: the airflow first flows through the motor, taking away part of the heat generated by the motor, the rotor and the stator of the motor undergo anti-erosion treatment, then flows through the front bearing, takes away the heat generated by the front bearing, and enters the second stage. The first-stage mixed-flow impeller enters the inclined first-stage diffuser after being pressurized and accelerated in the first-stage mixed-flow impeller. Further deceleration and boosting in the device, and then sequentially enter the secondary impeller boosting boost, the secondary diffuser decelerating boosting, the secondary bend and the secondary gas collector. discharge.

Compared with prior art, the present invention can obtain following beneficial effect:

1. The compressor of the present invention can meet the demand of large flow with a small size. Taking water refrigeration as an example, when the cooling capacity is 400kw and the inlet of the compressor is 12°C, the capacity flow at this time is 909m ³ /min. The invention can meet the requirements with a very small machine size, that is, the diameter of the impeller is only 420mm, and the maximum outer diameter of the compressor is only 650mm. For the same flow rate, if a centrifugal impeller is used, when the ratio of the diffuser outlet diameter D4 to the impeller outer diameter D2 is the same, the maximum diameter of the compressor will be 1.15 times that of the compressor of the present invention.

2. The reflux device of the compressor of the present invention has a pressure-diffusing effect, and a part of the kinetic energy of the gas is converted into a static pressure rise in the reflux device, so the diameters of the impeller and the diffuser can be further reduced. If the reflux device does not have a pressure-diffusing effect , to obtain the same pressure, it is necessary to further increase the size of the machine. With the same design parameters, the size of the compressor will reach about 1.389 times the size of the machine of the present invention, and the weight and volume of the machine will increase accordingly, thereby increasing the cost of the machine. In construction The compressor cannot be installed and used in places where the load is heavy or the installation space is limited.

3. In the prior art, the airflow passes through the "S" bend after coming out of the diffuser, which will cause a large local resistance loss, so the "S" bend is canceled in the present invention. When the compressor is used in an air-conditioning system with water as the working fluid, the medium density is very small, and the primary inlet density is 0.0077566-0.01067kg/m ³ . At this time, due to the small Re number, the friction loss dominates the compressor loss. The efficiency of the compressor is already relatively low, and after passing through the "S" curve, the efficiency of the compressor will be further reduced, and the COP of the entire refrigeration system will be reduced accordingly. The COP of the refrigeration and air-conditioning system will be relatively small, and the centrifugal compressor with "S" bend is not suitable for this parameter.

4. The blades of the mixed-flow impeller and the blades of the reflux are unified in design, and the aerodynamic coupling between the two is considered to reduce the internal flow loss of the mixed-flow stage, including the flow loss of the impeller, the impact loss at the inlet of the reflux, and the separation loss inside the reflux.

5. Compressors with large flow coefficients sometimes use axial flow compressors, or combined axial flow and centrifugal compressors. Compared with centrifugal compressors, this type of compressor is complicated to manufacture and the cost is too high. For example, the number of first-stage moving blades is more than 30, and the number of stationary blades can reach more than 100. Compared with centrifugal compressors, the manufacturing cost rises sharply; compared with centrifugal compressors, the performance curve of axial flow compressors has a narrow flow range. , easy to stall, and the narrow flow range is not suitable for application scenarios of air conditioning systems.

Description of drawings

Fig. 1 is a structural diagram of a centrifugal compressor according to Embodiment 1 of the present invention.

Fig. 2 is a vane with a three-dimensional arbitrary space curved surface of a reflux device with a diffuser function according to Embodiment 1 of the present invention.

Fig. 3 is a diagram of the pressure distribution on the suction surface and the pressure surface of the middle part of the blade along the flow direction of the diffuser blade of the embodiment 1 of the present invention. (The upper curve in the figure is the pressure distribution line on the pressure surface, and the lower curve is the pressure distribution line on the suction surface).

Fig. 4a is a mixed flow impeller with three-dimensional arbitrary spatially twisted blades according to Embodiment 1 of the present invention.

Fig. 4b is a side view of the mixed flow impeller with three-dimensional arbitrary spatially twisted blades according to Embodiment 1 of the present invention.

Fig. 5 is the centrifugal compressor stage of Comparative Example 1 of the present invention (wherein Z is the axial length, R is the radial length).

Fig. 6 is a mixed-flow compressor stage of Embodiment 2 of the present invention (wherein Z is the axial length, R is the radial length).

FIG. 7 is a comparison chart of the centrifugal compressor stage efficiency of Example 2 of the present invention and that of Comparative Example 1. FIG.

Among them, 1 is the motor, 2 is the front bearing, 3 is the first stage mixed flow impeller, 4 is the first stage diffuser, 5 is the first stage bend, 6 is the first stage reflux device, 7 is the second stage impeller, 8 is the secondary diffuser, 9 is the secondary bend, 10 is the secondary gas collector, 11 is the composite bearing, 12 is the main shaft of the compressor, 13 is the rear bearing support, 14 is the front bearing support, 15 is the motor support .

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments, and the given examples are only used to explain the present invention, and are not intended to limit the scope of the present invention.

Example 1

A mixed flow-centrifugal combined centrifugal compressor with a diffuser reflux device, including a mixed flow stage, a centrifugal stage, a motor 1, a front bearing 2, a composite bearing 11, and a compressor main shaft 12, wherein the mixed flow stage is the first stage, The centrifugal stage is the second stage; the mixed-flow stage includes the first-stage mixed-flow impeller 3, the first-stage diffuser 4, the first-stage bend 5, and the first-stage reflux device 6; the centrifugal stage includes the second-stage impeller 7, the second-stage diffuser Compressor 8, secondary bend 9, secondary gas collector 10;

Wherein the motor 1 is provided with a motor support 15 outside, and the center is provided with a compressor main shaft 12 common to the compressor, the front bearing 2 is provided with a front bearing support 14, the composite bearing 11 at the rear end is provided with a rear bearing support 13, and the composite bearing 11 at the rear end In order to support and thrust the composite bearing, two left and right thrust surfaces are provided to balance the axial thrust of the compressor impeller. The front bearing 2 and the composite bearing 11 jointly support the compressor main shaft 12, the first-stage mixed-flow impeller 3 and the second-stage impeller 7 On the compressor shaft 12.

The outlet of the first-stage mixed-flow impeller is connected to the inlet of the first-stage diffuser, the outlet of the first-stage diffuser is connected to one end of the first-stage bend, and the other end of the first-stage bend is connected to the first-stage The inlet of the reflux is connected, the outlet of the first-stage reflux is connected to the inlet of the second-stage impeller, the outlet of the second-stage impeller is connected to the inlet of the second-stage diffuser, and the outlet of the second-stage diffuser is connected to the second-stage bend One end of the secondary bend is connected, and the other end of the secondary bend is connected with the inlet of the secondary gas collector;

Both the first-stage mixed-flow impeller and the second-stage impeller are open impellers with splitter blades, and the first-stage mixed-flow impeller and the second-stage impeller are coaxial and in the same direction as the inlet.

The outlet area of the first-stage reflux device is larger than the inlet area, the outlet area of the second-stage gas collector is larger than the inlet area, and the blades of the first-stage reflux device and the blades of the second-stage gas collector are all three-dimensional arbitrary space distortion blades.

The included angle between the side solid wall of the outlet disk of the first-stage mixed-flow impeller and the axis is 60-85°.

The first-stage diffuser is inclined, the width of its inlet and outlet is consistent, and the included angle between its center line and the axis of the compressor is 60-85°.

The entrance of the first-order bend is inclined, and the included angle with the axis is 5-30°, and the exit of the first-order bend is parallel to the axis.

The outlet width of the first-stage mixed-flow impeller is b2, the outlet diameter of the first-stage mixed-flow impeller is D2, and b2/D2 is 0.08-0.1.

The first-stage mixed-flow impeller adopts three-dimensional arbitrary space blades.

The first-stage mixed-flow impeller is a splitter blade, the splitter blade on the disk side is located at 10%-20% of the total flow path length, and the splitter blade on the cover side is located at 15%-25% of the total flow path length.

The rotor of the motor, the first-stage mixed-flow impeller and the second-stage impeller together constitute the rotor of the compressor. The motor has no bearings, and the support of the motor is a single cantilever support. Composite bearings for thrust bearings.

In the present invention, after the airflow comes out of the first-stage mixed-flow impeller, it passes through the inclined first-stage diffuser, and is no longer forced to turn radially, so that the flow loss can be reduced, and the radial dimension can be reduced.

Comparative example one

Compressor design parameters: the working medium is water vapor, the inlet temperature is 12°C, the inlet pressure is 1.402KPaA, the outlet static pressure is 3.033KPaA, the mass flow rate is 582kg/h, the inlet volume flow rate is 909m ³ /min, the design speed n=21600rpm, the impeller blades Outlet installation angle β _2A =65°. The centrifugal impeller of the prior art is adopted, and the reflux device has no diffusion effect. The design result is that the diameter of the impeller is D2=444mm. At this time, the maximum outer diameter _D42 of the compressor stage bend is 815mm, as shown in Figure 5.

Embodiment two

A mixed-flow-centrifugal combined centrifugal compressor with a diffuser reflux device in Embodiment 1 is applied to a refrigeration air conditioner using water as a refrigerant. This embodiment has the same aerodynamic design parameters as Comparative Example 1, the same design speed n=21600 rpm, and the same impeller blade outlet installation angle β _2A =65°. Using the compressor of Embodiment 1 of the present invention, as shown in Figure 1, the angle between the solid wall on the outlet plate side of the first-stage mixed-flow impeller and the axis of the compressor is 60 degrees, and the inlet end of the first-stage mixed-flow impeller maintains the characteristics of the centrifugal impeller , which shortens the axial dimension of the impeller. The air flow directly enters the first-stage reflux device from the first-stage bend, which shortens the passage distance to the maximum extent, reduces the friction loss along the process and the local resistance loss caused by multiple winding bends, which will cause the compressor to The field of refrigeration and air conditioning where water is the refrigerant fails. The air flow continues to expand in the first-stage reflux device, which undertakes part of the function of the diffuser. The static-static pressure ratio of the outlet of the first-stage reflux device relative to its inlet is 1.1. At this time, the compressor stage bends The maximum outer diameter D ₄₂ of the track is 590mm, as shown in Figure 6, compared with Comparative Example 1, the outer diameter is only about 72% of it, which greatly reduces the radial dimension of the compressor. The CFD calculation results show that the stage efficiency of the compressor (mixed-flow compressor) of the present invention is slightly higher than that of the compressor (centrifugal compressor) of Comparative Example 1, as shown in FIG. 7 .

The invention greatly reduces the radial dimension of the machine and improves the efficiency of the machine. In the field of refrigeration and air conditioning, when the refrigerant is pure water, the size of the compressor of the present invention is small, which can meet the requirements of reducing manufacturing costs; at the same time, the compressor of the present invention maintains high efficiency and ensures the COP of the entire refrigeration system .

The above description is only a preferred specific embodiment of the present invention, and any person familiar with the technical field utilizes the equivalent structural transformation made by the content of the present invention, or directly or indirectly uses the technical field attached to other related products, especially The field of air conditioning using water as refrigerant is also included in the scope of patent protection of the present invention.

Claims (5)

1. A mixed-flow-centrifugal combined centrifugal compressor with a diffuser effect reflux device, characterized in that: comprise a mixed-flow stage, a centrifugal stage and a motor, the mixed-flow stage is the first stage, and the centrifugal stage is the second stage; the mixed-flow stage includes the first-stage mixed-flow impeller, the first-stage diffuser, the first-stage bend and the first-stage reflux device; the centrifugal stage includes the second-stage impeller, the second-stage diffuser, the second-stage bend and the second-stage gas collector; The outlet of the first-stage mixed-flow impeller is connected to the inlet of the first-stage diffuser, the outlet of the first-stage diffuser is connected to one end of the first-stage bend, and the other end of the first-stage bend is connected to the first-stage bend. The inlet of the first-stage reflux is connected, the outlet of the first-stage reflux is connected to the inlet of the second-stage impeller, the outlet of the second-stage impeller is connected to the inlet of the second-stage diffuser, and the outlet of the second-stage diffuser is connected to the inlet of the second-stage diffuser. One end of the bend is connected, and the other end of the secondary bend is connected with the inlet of the secondary gas collector; The first-stage mixed-flow impeller and the second-stage impeller are connected to the motor through a compressor main shaft; Both the first-stage mixed-flow impeller and the second-stage impeller are open impellers containing splitter blades, and the first-stage mixed-flow impeller and the second-stage impeller are coaxial and in the same direction as the inlet; The included angle between the solid wall on the side of the outlet disk of the first-stage mixed-flow impeller and the axis is 60-85°; The first-stage diffuser is inclined, its inlet and outlet have the same width, and the included angle between its centerline and the axis of the compressor is 60-85°; The outlet width of the first-stage mixed-flow impeller is b2, the outlet diameter of the first-stage mixed-flow impeller is D2, and b2/D2 is 0.08-0.1; The rotor of the motor, the first-stage mixed-flow impeller, and the second-stage impeller together constitute the rotor of the compressor, the motor has no bearing, the support of the motor is a single cantilever support, and the support of the rotor of the compressor is distributed among the Magnetic suspension bearings at both ends and composite bearings with two-way thrust bearings; There is no S bend behind the diffuser of the compressor; The outlet area of the first-stage reflux device is larger than its inlet area, the outlet area of the second-stage gas collector is larger than its inlet area, and the blades of the first-stage reflux device and the blades of the second-stage gas collector are all three-dimensional arbitrary spaces Twist the blade. 2. A kind of mixed-flow-centrifugal combined centrifugal compressor with diffuser reflux device according to claim 1, characterized in that: the entrance of the first-stage bend is inclined, and the included angle with the axis is 5-30°, the exit of the first-stage bend is parallel to the axis. 3. A mixed flow-centrifugal combined centrifugal compressor with a diffuser reflux device according to claim 1, characterized in that: the first stage mixed flow impeller adopts three-dimensional arbitrary space blades. 4. A mixed flow-centrifugal combined centrifugal compressor with a diffuser reflux device according to claim 1, characterized in that: the first-stage mixed flow impeller is a splitter vane, and the splitter vane on the disk side is located in the overall At 10%-20% of the length of the flow channel, the splitter vane on the cover side is located at 15%-25% of the total flow channel length. 5. The application of a mixed-flow-centrifugal combined centrifugal compressor with a diffuser reflux device according to any one of claims 1-4 in a refrigeration air conditioner using water as a refrigerant.

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