Volute of small centrifugal refrigeration compressor with extremely low flow coefficient

Abstract

The invention relates to a small centrifugal refrigeration compressor volute with an extremely low flow coefficient. The small centrifugal refrigeration compressor volute comprises a compressor air inlet pipe, a compressor top cover, a split volute upper end cover and a split volute lower end cover. The compressor air inlet pipe is fixed to an air inlet of the compressor top cover, and the half-split volute upper end cover and the half-split volute lower end cover are both in a disc shape and matched with each other. The upper half volute end cover and the lower half volute end cover are installed in an aligned mode, spiral flow channel grooves are formed in the attached end faces of the upper half volute end cover and the lower half volute end cover respectively, and the spiral flow channel grooves of the upper half volute disc and the lower half volute disc are connected and spliced to form a spiral flow channel. The split volute upper end cover and the split volute lower end cover are installed in an aligned mode. According to the small centrifugal refrigeration compressor volute with the extremely low flow coefficient, the half-split volute design is adopted, the volute profile is adjusted, the width of the spiral flow channel is adjusted to be larger than the outlet width of the centrifugal impeller, and the volute diffusion efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of compressor technology, in particular to a kind of small centrifugal refrigeration compressor volute of extremely low flow coefficient. BACKGROUND

[0002] Figure 1 As shown in the prior art, the structure diagram of existing small centrifugal refrigeration compressor volute is shown in the figure, Figure 1 As shown, the existing small centrifugal refrigeration compressor of extremely low flow coefficient adopts radial vaneless diffuser 1 after spiral cross section volute 2 to collect the refrigerant gas behind the diffuser, and through the certain expansion form of volute cross section profile 3 and volute width b, the flow cross section gradually increases along the rotation direction of airflow, to realize the further speed reduction of refrigerant gas.

[0003] But the volute in prior art is usually integrally casted, and it is not easy to process the internal flow passage surface during processing, so that the surface roughness is high, and the flow field near the surface is affected, which affects the efficiency of centrifugal compressor.

[0004] Therefore, how to solve various problems caused by the miniaturization of centrifugal compressor, so that it can be applied to small and medium-sized refrigeration system to replace screw compressor, scroll compressor and even rolling rotor compressor, will make the energy efficiency of these refrigeration systems higher, and have a profound impact on refrigeration industry. SUMMARY

[0005] The purpose of the present application is to provide a kind of small centrifugal refrigeration compressor volute of extremely low flow coefficient to solve the problems of the prior art.

[0006] The small centrifugal refrigeration compressor volute of extremely low flow coefficient comprises: compressor inlet pipe, compressor top cover, half volute upper end cover, half volute lower end cover; the compressor inlet pipe is fixed with the inlet of the compressor top cover, the half volute upper end cover and the half volute lower end cover are both disc-shaped and matched with each other; the half volute upper end cover and the half volute lower end cover are installed in alignment, and the end surfaces of each other are provided with spiral flow channel groove, and the spiral flow channel grooves of the upper and lower half volute discs are connected and spliced to form a spiral flow channel. The type line of the cross section of the spiral flow channel in the half volute upper end cover and the half volute lower end cover is , wherein r4 is the outlet radius of vaneless diffuser, b4 is the outlet width, Q4 is the outlet flow, is the position angle, and the average flow velocity is

[0007] According to an embodiment of the volute of the present application, the half volute upper end cover and the half volute lower end cover are each provided with a positioning hole, and are installed on the outer wall of the compressor through the positioning hole.

[0008] According to an embodiment of the volute of the application, further comprising: a front impeller grate, a rear impeller grate, a rear impeller grate position slot, and a front impeller grate position slot; the front impeller grate position slot is arranged on the upper half volute cover, so that the upper half volute cover is positioned with the front impeller grate; the front impeller grate is a zigzag circular ring labyrinth seal, and is connected with the upper half volute cover by bolts; the rear impeller grate position slot is arranged on the lower half volute cover, so that the lower half volute cover is positioned with the rear impeller grate; the rear impeller grate is a zigzag circular ring labyrinth seal, and is connected with the lower half volute cover by bolts.

[0009] According to an embodiment of the volute of the application, further comprising: a vaneless diffuser, wherein the vaneless diffuser is composed of two symmetrical disc-shaped half cavities, and is arranged on the upper half volute cover and the lower half volute cover respectively; the vaneless diffuser surrounds the impeller.

[0010] According to an embodiment of the volute of the application, the width of the vaneless diffuser of the volute is equal to the width of the volute.

[0011] According to an embodiment of the volute of the application, the spiral flow channel of the volute is flat, so that the cross section is strip-shaped; the outlet flow channel is connected with the outlet of the spiral flow channel of the volute, and gradually transitions from the flat shape to a cylindrical shape.

[0012] According to an embodiment of the volute of the application, the width of the volute is 4 to 6 times the width of the outlet of the impeller.

[0013] According to an embodiment of the volute of the application, the axial width of the spiral flow channel is 4 to 6 times the axial width of the outlet of the impeller.

[0014] According to an embodiment of the volute of the application, the compressor inlet pipe is welded with the inlet of the compressor top cover.

[0015] According to an embodiment of the volute of the application, each of the upper and lower half volute discs is provided with a volute flow channel slot, and the volute flow channel slots are connected to form a spiral flow channel.

[0016] The half volute design of the volute of the small centrifugal refrigeration compressor with extremely low flow coefficient improves the diffuser efficiency of the volute by adjusting the volute profile and the width of the spiral flow channel. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Fig. 1 shows the structure of the existing small centrifugal refrigeration compressor volute; Figure 2 Fig. 2 shows the cross-sectional view of the small centrifugal refrigeration compressor volute with extremely low flow coefficient according to the application. Figure 3 The diagram shown is an internal structure diagram of the volute casing of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention. Figure 4 The diagram shown is an external schematic of the casing of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention. Figure 5 The diagram shown is a structural design of the volute casing of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention. Figure 6 The diagram shown illustrates the positional relationship of the vaneless diffuser in the volute of the ultra-low flow coefficient small centrifugal refrigeration compressor of this invention. Detailed Implementation

[0018] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0019] Figure 2 The image shown is a cross-sectional view of the casing of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention. Figure 3 The diagram shown is an internal structural diagram of the volute casing of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention. Figure 4 The diagram shown is an external schematic of the casing of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention. Figure 2 , Figure 3 as well as Figure 4 As shown, the volute of a small centrifugal refrigeration compressor with an extremely low flow coefficient according to the present invention includes: a compressor inlet pipe 13, a compressor top cover 14, a split volute upper end cover 15, a split volute lower end cover 4, an impeller front grate 5, an impeller rear grate 6, an impeller front grate position groove 7, a fixing screw hole 8, a positioning hole 9, a disassembly threaded hole 10, a volute exhaust port 12, and a bladeless diffuser 11.

[0020] like Figures 2 to 4 As shown, the compressor intake pipe 13 is welded to the intake port of the compressor top cover 14. Both the upper end cover 15 and the lower end cover 4 of the split volute are disc-shaped and match each other. The discs of the upper end cover 15 and the lower end cover 4 are aligned and installed. Each of the mating end faces has a spiral flow channel groove. The two volute flow channel grooves are joined together to form a spiral flow channel. This allows for surface finishing of the inner surface of the spiral flow channel and rounding of the corners during the separate fabrication of the upper and lower end covers, making the surface smoother and the internal flow field distribution more uniform, reducing flow losses caused by excessively rough flow channel surfaces. This improves the operating efficiency of the centrifugal compressor, facilitating its miniaturization.

[0021] like Figures 2 to 4As shown in the drawings, the upper half volute end cover 15 and the lower half volute end cover 4 are installed in the outer wall of the compressor through the positioning hole 9, so that the shape and opening of each part are very simple and regular, which makes the machining of each part very convenient, and also makes the inner wall of the flow passage fully exposed, so that the finishing operation of the surface of the flow passage is very convenient.

[0022] As shown in the drawings, Figures 2 to 4 As shown in the drawings, the impeller front gauze tooth position slot 7 is arranged on the upper half volute end cover 15, which serves to position the upper half volute end cover 15 and the impeller front gauze tooth 7. The impeller front gauze tooth 7 is a sawtooth-shaped circular ring labyrinth seal ring, which is connected to the upper half volute end cover 15 through bolts. The impeller rear gauze tooth position slot is arranged on the upper half volute end cover 15, which serves to position the lower half volute end cover 4 and the impeller rear gauze tooth 6. The impeller rear gauze tooth 6 is a sawtooth-shaped circular ring labyrinth seal ring, which is connected to the lower half volute end cover 4 through bolts.

[0023] Figure 5 As shown in the drawings, the structure design of the volute of the small centrifugal refrigeration compressor with very low flow coefficient according to the present application is shown in the drawings, as shown in the drawings, Figure 5 As shown in the drawings, the spiral flow passage 19 of the volute is flat, that is, the cross section of the flow passage is a long rectangular shape. The outlet flow passage 18 is connected to the outlet of the spiral flow passage 19 of the volute. In the direction of the flow of the gas, the outlet flow passage 18 gradually transitions from the flat spiral flow passage 19 to a cylindrical shape. The flat spiral flow passage 19 makes the volute flat, which is beneficial to reduce the axial size of the centrifugal compressor and realize the miniaturization of the compressor. More importantly, since the outlet flow passage 18 gradually transitions from the flat shape to the cylindrical shape, the gas flow from the thin, flat spiral flow passage 19 to the cylindrical, wider outlet flow passage 18 has a very good pressure recovery effect. Moreover, since the outlet flow passage gradually transitions from the flat shape to the cylindrical shape, the transition is very smooth, which reduces unnecessary resistance loss of the gas flow, effectively improves the pressure recovery efficiency of the volute, reduces the pressure recovery loss, and the cylindrical shape is also suitable for connecting to the downstream pipeline.

[0024] Figure 6 As shown in the drawings, the position relationship diagram of the bladeless diffuser of the volute of the small centrifugal refrigeration compressor with very low flow coefficient according to the present application is shown in the drawings, Figures 2 to 6 As shown in the drawings, the bladeless diffuser 11 is a two-disc-shaped half-cavity located between the impeller outlet and the volute. The impeller is installed in the impeller shaft hole 17 and rotates, which sucks the gas flow from the compressor inlet pipe, and then the gas flow is speeded up and pressurized in the bladeless diffuser 11, and finally the gas flow is discharged from the volute outlet after being collected and rectified by the volute.

[0025] For an embodiment, the width of the vaneless diffuser 11 is equal to the width of the volute.

[0026] Through repeated experiments, the inventor has confirmed that for the low-flow coefficient centrifugal compressor, the ratio of the axial width of the spiral flow passage to the outlet axial width b of the centrifugal impeller should be between 4 and 6 to achieve the optimal effect.

[0027] According to the advantages of the compressor structure and convenient manufacturing, the rectangular volute is used to directly collect the outlet airflow of the impeller, the direction of the outlet airflow of the volute is changed to the axial direction, and the square-to-round structure is further used for pressure expansion.

[0028] The average flow velocity Cm of each section in the volute is designed to generate the volute profile, and the profile is controlled according to where r4, b4 and Q4 are the outlet radius, outlet width and flow rate of the vaneless diffuser, and the position angle is in the range of 0-360°.

[0029] As shown in Table 1, the total pressure recovery coefficient from the outlet of the impeller to the outlet of the diffuser is 0.9771, the total pressure recovery coefficient from the outlet of the diffuser to the outlet of the volute is 0.9926, and the overall total pressure recovery coefficient is 0.9758.

[0030]

[0031] Table 1

[0032] After the inlet airflow of the volute enters the volute, the Ma is high (up to 0.9 Mach), the loss is high, and the centrifugal force is large, after the airflow leaves the volute, the centrifugal force cannot be eliminated and there is no more airflow to supplement the main flow, resulting in the formation of a high-speed zone outside the outlet of the volute and a low-speed zone inside the outlet of the volute, and the flow field is not uniform. To eliminate or at least alleviate the above adverse effects, the volute profile is adjusted, and the width of the spiral flow passage is greater than the outlet width b of the centrifugal impeller, so that the airflow entering the volute (the volute flow passage) is expanded and slowed down, the Mach number is reduced, the centrifugal effect is reduced, and finally the flow field uniformity of the outlet of the volute is significantly increased, the total pressure loss is reduced, and the volute expansion efficiency is improved. And the present application adopts a split volute design, which is a split structure, solves the problem that the surface roughness of the volute in the prior art is high, which affects the flow field near the surface of the flow passage and affects the efficiency of the centrifugal compressor.

[0033] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A volute casing for a small centrifugal refrigeration compressor with extremely low flow coefficient includes: Compressor intake pipe, compressor top cover, upper end cover of split volute, lower end cover of split volute; The compressor intake pipe is fixed to the intake port of the compressor top cover. The upper end cover and the lower end cover of the split volute are both disc-shaped and match each other. The upper and lower end covers of the split volute are aligned and installed, and each of the mating end faces has a spiral flow channel groove. The spiral flow channel grooves of the upper and lower volute discs are joined together to form a spiral flow channel. The upper and lower end covers of the split-spindle casing are aligned and installed, and the profile of the spiral flow channel cross-section in the casing is as follows: Where r4 is the outlet radius of the bladeless diffuser, It is the width of the outlet. It is the export flow. The position angle is and the average flow velocity is . .

2. The volute as described in claim 1, characterized in that, The upper and lower end covers of the split volute each have positioning holes, which are then installed on the outer wall of the compressor.

3. The volute as described in claim 1, characterized in that, It also includes: impeller front grate teeth, impeller rear grate teeth, impeller rear grate tooth position groove and impeller front grate tooth position groove; The impeller front grate tooth positioning groove is formed in the upper end cover of the split volute to allow the upper end cover of the split volute to mate and position with the impeller front grate tooth; the impeller front grate tooth is a sawtooth-shaped circular labyrinth seal ring, which is connected to the upper end cover of the split volute by bolts; The impeller rear grate tooth positioning groove is opened in the lower end cover of the split volute so that the lower end cover of the split volute and the impeller rear grate tooth can be matched and positioned; the impeller rear grate tooth is a sawtooth-shaped circular labyrinth seal ring, which is connected to the lower end cover of the split volute by bolts.

4. The volute as described in claim 1, characterized in that, Also includes: The bladeless diffuser consists of two symmetrical disc-shaped half-cavities, located on the upper end cover and lower end cover of the half-volute respectively; the bladeless diffuser surrounds the impeller.

5. The volute as described in claim 4, characterized in that, The width of the bladeless diffuser of the volute is equal to the width of the volute.

6. The volute as described in claim 1, characterized in that, The spiral flow channel of the volute is flat, making the cross-section strip-shaped; the outlet flow channel is connected to the outlet of the spiral flow channel of the volute, and the outlet flow channel gradually transitions from a flat shape adapted to the spiral flow channel to a cylindrical shape.

7. The volute as described in claim 1, characterized in that, The width of the volute is 4 to 6 times the width of the impeller outlet.

8. The volute as described in claim 1, characterized in that, The axial width of the spiral flow channel is 4 to 6 times the axial width of the impeller outlet.

9. The volute as described in claim 1, characterized in that, The compressor intake pipe is welded to the intake port of the compressor top cover.

10. The volute as claimed in claim 1, characterized in that, Each of the upper and lower halves of the volute disc has a volute-shaped flow channel groove, which are joined together to form a spiral flow channel.

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