GAS SUCTION PIPE OF CENTRIFUGAL COMPRESSOR

Description

TECHNICAL FIELD

The present application relates to a gas suction pipe of a centrifugal compressor, in particular to a gas suction pipe of a refrigeration centrifugal compressor mainly applied to large water chilling units.

BACKGROUND ART

The refrigeration centrifugal compressor used in large water chilling units allows refrigerant gas coming out of an evaporator to undergo high-speed rotation of an impeller in the centrifugal compressor, such that the refrigerant gas acquires a high speed and is then transported to a condenser to subject the refrigerant to a refrigeration cycle. The elbow-shaped gas suction pipe of the centrifugal compressor connects the evaporator to an impeller of the centrifugal compressor, such that the refrigerant gas coming out of the evaporator enters the evaporator through the gas suction pipe. Since the gas suction pipe is elbow-shaped, a flow direction of the refrigerant gas in the process of entering the gas suction pipe from the evaporator and reaching the impeller of the centrifugal compressor is deflected. There is a pressure loss in the gas suction pipe of the centrifugal compressor in the prior art, thereby affecting the performance of the compressor.

SUMMARY OF THE UTILITY MODEL

According to a first aspect of the present application, the present application provides a gas suction pipe of a centrifugal compressor, the centrifugal compressor is provided with a gas suction port, the gas suction port has a central axis, the gas suction pipe introduces a fluid from an upstream component into the centrifugal compressor, and the fluid enters the gas suction pipe in a direction substantially perpendicular to the central axis of the gas suction port. The gas suction pipe comprises an imaginary middle cross-section, a downstream interface connected to the centrifugal compressor, and an upstream interface connected to the upstream component. The central axis of the gas suction port of the centrifugal compressor is located on the middle cross-section, and the gas suction pipe has a shape of being symmetrical with respect to the middle cross-section. An inner contour of the downstream interface is circular, and the downstream interface is connected to the gas suction port. An inner contour of the upstream interface comprises a first direction maximum spanning size D₁ located on the middle cross-section, and comprises a second direction maximum spanning size D₂ perpendicular to the middle cross-section, wherein the first direction maximum spanning size D₁ is greater than the second direction maximum spanning size D₂.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, the upstream component is cylindrical with an axis parallel to the central axis of the gas suction port, and has a diameter D₀. The first direction maximum spanning size D₁ and the second direction maximum spanning size D₂ of the inner contour of the upstream interface satisfy: 0.55<D₁/D₀<0.7, D₂<0.5×D₁. A radius R₆ of the inner contour of the downstream interface satisfies: 0.43<R_6max/D₁<0.57.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, the gas suction pipe has a centerline located on the middle cross-section. The centerline is a spline, and the centerline satisfies the following formula:

Y = V 1 - V 2 1 + exp ⁢ ( X - V 3 V 4 ) + V 2 ,

wherein V₁, V₂, V₃, V₄ satisfy the following relationship: −7e7<V₁<−6e7, 1100<V₂<1300, −2950<V₃<−2750, 250<V₄<270.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, the gas suction pipe comprises an inlet section, an outlet section and a transition section. The upstream interface is an end face of the inlet section, the inlet section comprises a connection part and a guide part, the connection part connects the gas suction pipe to the upstream component, a connection line of an inner contour of the guide part and an inner contour of the connection part intersects with the middle cross-section at an inner intersection point and an outer intersection point. The downstream interface is an end face of the outlet section. The transition section connects the inlet section to the outlet section. The gas suction pipe comprises a first cross-section, and the first cross-section passes through the inner intersection point and the outer intersection point and is perpendicular to the middle cross-section. Between the first cross-section and the downstream interface, cross-sections of inner contours of the gas suction pipe at least on the inlet section and the transition section are elliptical with major axes located on the middle cross-section.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, between the first cross-section and the downstream interface, cross-sections of inner contours of the inlet section and the outlet section of the gas suction pipe gradually decrease in a direction toward the downstream interface.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, the cross-section of the inner contour of the gas suction pipe on the transition section first gradually increases and then gradually decreases in the direction toward the downstream interface.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, four cross-sections that divide a portion of the gas suction pipe located between the first cross-section and the downstream interface into five equal parts along the centerline are a second cross-section, a third cross-section, a fourth cross-section and a fifth cross-section, respectively, wherein the fourth cross-section is the largest cross-section of the transition section. An included angle α₆ between the downstream interface and the first cross-section satisfies: 80°≤α₆≤90°. A major axis radius R_1max and a minor axis radius R_1min of the first cross-section respectively satisfy: R_1max=0.5×D₁, 0.9<R_1min/R_1max<0.95. An included angle α₂ between the second cross-section and the first cross-section and a major axis radius R_2max and a minor axis radius R_2min of the second cross-section respectively satisfy: 0.1<α₂/α₆<0.15, 0.68<R_2max/D₁<0.78, 0.92<R_2min/R_2max<0.98. An included angle α₃ between the third cross-section and the first cross-section and a major axis radius R_3max and a minor axis radius R_3min of the third cross-section respectively satisfy: 0.25<α₃/α₆<0.38, 0.6<R_3max/D₁<0.76, 0.8<R_3min/R_3max<0.9. An included angle α₄ between the fourth cross-section and the first cross-section and a major axis radius R_4max and a minor axis radius R_4min of the fourth cross-section respectively satisfy: 0.45<α₄/α₆<0.6, 0.6<R_4max/D₁<0.74, 0.84<R_4min/R_4max<0.92. An included angle as between the fifth cross-section and the first cross-section and a major axis radius R_5max and a minor axis radius R_5min of the fifth cross-section respectively satisfy: 0.7<α₅/α₆<0.8, 0.45<R_5max/D₁<0.6, 0.98<R_5min/R_5max<1.05.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, the cross-section of the gas suction pipe on the transition section gradually decreases in the direction toward the downstream interface.

According to the gas suction pipe of the centrifugal compressor of the above-mentioned first aspect, four cross-sections that divide a portion of the gas suction pipe located between the first cross-section and the downstream interface into five equal parts along the centerline are a second cross-section, a third cross-section, a fourth cross-section and a fifth cross-section, respectively, wherein the fourth cross-section is the largest cross-section of the transition section. An included angle α₁₆ between the downstream interface and the first cross-section satisfies: 80°≤α₁₆≤90°. The major axis radius R_11min and the minor axis radius R_12min of the first cross-section respectively satisfy: R11max=0.5×D₁₁, 0.9<R11min/R11max<0.95. An included angle α₁₂ between the second cross-section and the first cross-section and a major axis radius R12max and a minor axis radius R12min of the second cross-section respectively satisfy: 0.1<α₁₂/α₁₆<0.15, 0.68<R12max/D11<0.78, 0.92<R12min/R12max<0.98. An included angle α₁₃ between the third cross-section and the first cross-section and a major axis radius R13max and a minor axis radius R13min of the third cross-section respectively satisfy: 0.25<α₁₃/α₁₆<0.38, 0.55<R13max/D11<0.7, 0.8<R13min/R13max<0.9. An included angle α14 between the fourth cross-section and the first cross-section and a major axis radius R14max and a minor axis radius R14min of the fourth cross-section respectively satisfy: 0.45<α₁₄/α₁₆<0.6, 0.5<R14max/D11<0.6, 0.9<R14min/R14max<0.95. An included angle α₁₅ between the fifth cross-section and the first cross-section and a major axis radius R15max and a minor axis radius R15min of the fifth cross-section respectively satisfy: 0.7<α₁₅/α₁₆<0.8, 0.45<R_15max/D₁₁<0.6, 0.98<R_15min/R_15max<1.05.

According to a second aspect of the present application, the present application provides a centrifugal compressor, wherein the centrifugal compressor comprises the gas suction pipe according to the above-mentioned first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a water chilling unit using a gas suction pipe of a centrifugal compressor of the present application;

FIG. 1B is a simplified left schematic view of the water chilling unit shown in FIG. 1A;

FIG. 2A is a front perspective view of a first embodiment of the gas suction pipe of the centrifugal compressor of the present application;

FIG. 2B is a rear perspective view of the gas suction pipe of the centrifugal compressor shown in FIG. 2A;

FIG. 2C is a front view of an inner contour of the gas suction pipe of the centrifugal compressor shown in FIG. 2A;

FIG. 2D is a left view of the inner contour of the gas suction pipe of the centrifugal compressor shown in FIG. 2A;

FIG. 2E is a schematic diagram of a first cross-section in FIG. 2D;

FIG. 2F is a schematic diagram of a second cross-section in FIG. 2D;

FIG. 2G is a schematic diagram of a third cross-section in FIG. 2D;

FIG. 2H is a schematic diagram of a fourth cross-section in FIG. 2D;

FIG. 2I is a schematic diagram of a fifth cross-section in FIG. 2D;

FIG. 2J is a schematic diagram of an inner contour of a downstream interface of the gas suction pipe used for the centrifugal compressor shown in FIG. 2A;

FIG. 3A is a schematic diagram showing a fluid flow state of a gas suction pipe in one comparative example when in use;

FIG. 3B is a schematic diagram showing a fluid flow state in the first embodiment of the gas suction pipe used for the centrifugal compressor of the present application when in use;

FIG. 3C shows a velocity vector diagram in the gas suction pipe obtained by adopting a CFD method for the gas suction pipe in the comparative example shown in FIG. 3A;

FIG. 3D shows the velocity vector diagram in the gas suction pipe obtained by adopting the CFD method for the gas suction pipe of the present application shown in FIG. 3B;

FIG. 3E shows a velocity vector diagram at the downstream interface of the gas suction pipe obtained by adopting the CFD method for the gas suction pipe in the comparative example shown in FIG. 3A;

FIG. 3F shows the velocity vector diagram at the downstream interface of the gas suction pipe obtained by adopting the CFD method for the gas suction pipe of the present application shown in FIG. 3B;

FIG. 3G shows a vortex intensity diagram at the downstream interface of the gas suction pipe obtained by adopting the CFD method for the gas suction pipe in the comparative example shown in FIG. 3A;

FIG. 3H shows the vortex intensity diagram at the downstream interface of the gas suction pipe obtained by adopting the CFD method for the gas suction pipe of the present application shown in FIG. 3B;

FIG. 4A is a front perspective view of a second embodiment of the gas suction pipe of the centrifugal compressor of the present application;

FIG. 4B is a rear perspective view of the second embodiment of the gas suction pipe of the centrifugal compressor of the present application;

FIG. 4C is a front view of an inner contour of the second embodiment of the gas suction pipe of the centrifugal compressor of the present application;

FIG. 4D is a left view of the inner contour of the second embodiment of the gas suction pipe of the centrifugal compressor of the present application;

FIG. 4E is a schematic diagram of a first cross-section in FIG. 4D;

FIG. 4F is a schematic diagram of a second cross-section in FIG. 4D;

FIG. 4G is a schematic diagram of a third cross-section in FIG. 4D;

FIG. 4H is a schematic diagram of a fourth cross-section in FIG. 4D;

FIG. 4I is a schematic diagram of a fifth cross-section in FIG. 4D; and

FIG. 4J is a schematic diagram of an inner contour of a downstream interface of the gas suction pipe of the centrifugal compressor shown in FIG. 4A.

DETAILED DESCRIPTION OF EMBODIMENTS

Various specific embodiments of the present application will be described below with reference to the accompanying drawings, which constitute a part of the specification. It should be understood that although terms, such as “front”, “rear”, “upper”, “lower”, “left”, “right”, etc., that represent directions are used in the present application to describe various example structural parts and elements of the present application, these terms used herein are determined based on example orientations shown in the accompanying drawings for ease of illustration only. Since the embodiments disclosed in the present application may be disposed in different directions, these terms that represent directions are for illustration only and should not be regarded as limiting.

The present application provides an improved gas suction pipe of a centrifugal compressor, which reduces the pressure loss of fluid in the gas suction pipe by changing a shape of the gas suction pipe.

FIGS. 1A and 1B show an overall structure of a water chilling unit 100 using the gas suction pipe of the centrifugal compressor of the present application, wherein FIG. TA is a perspective view of the water chilling unit 100, and FIG. 1B is a simplified left schematic view of the water chilling unit 100. As shown in FIGS. 1A and 1B, the water chilling unit 100 comprises an evaporator 110, a centrifugal compressor 120, a condenser 130 and a throttling device (not shown in the figure) which form a refrigeration cycle. The centrifugal compressor 120 is provided with a gas suction port 125, and the gas suction port 125 has a central axis X1. The evaporator 110 comprises a cylinder which is substantially cylindrical, an axis X2 of which is mutually parallel to the central axis X1 of the gas suction port 125 of the centrifugal compressor 120, and the diameter of which is D₀. The water chilling unit 100 further comprises a gas suction pipe 150 connecting the evaporator 110 to the centrifugal compressor 120. The evaporator 110 is an upstream component of the centrifugal compressor 120.

The refrigeration cycle of the water chilling unit 100 comprises four processes: a compression process, a condensation process, a throttling process and an evaporation process. During the compression process, the refrigerant gas coming out of the evaporator 110 first obtains a high speed through the high-speed rotation of an impeller of the centrifugal compressor 120, and then becomes high-temperature and high-pressure refrigerant gas through the diffusion and deceleration of a diffuser and a volute. During the condensation process, the high-temperature and high-pressure refrigerant gas coming out of the centrifugal compressor 120 enters the condenser 130 for condensation, and a high-temperature and high-pressure refrigerant exchanges heat with relatively low-temperature cooling water flowing through the condenser 130 and is then condensed into a liquid state. During the throttling process, a high-pressure and normal-temperature refrigerant liquid coming out of the condenser 130 passes through a throttling device (such as a throttling orifice plate) and becomes a low-temperature and low-pressure refrigerant liquid. During the evaporation process, a low-temperature and low-pressure refrigerant liquid coming out of the throttling device enters the evaporator 110 and exchanges heat with the cooling water in the evaporator 110, such that the low-temperature and low-pressure refrigerant liquid evaporates into normal-temperature and normal-pressure refrigerant gas. The gas suction pipe 150 introduces the refrigerant gas coming out of the evaporator 110 into the centrifugal compressor 120. During this process, since axes of the evaporator 110 and the centrifugal compressor 120 are parallel to each other, a flow direction of the refrigerant gas needs to be changed through the gas suction pipe 150, so the gas suction pipe 150 is generally elbow-shaped. More specifically, the refrigerant gas coming out of the evaporator 110 generally enters the gas suction pipe 150 along a direction that is substantially perpendicular to the axis of the compressor 120, and the refrigerant gas coming out of the gas suction pipe 150 needs to enter the compressor along an axis direction of the compressor 120. Therefore, the gas suction pipe 150 deflects the flow direction of gas flow by about 90°.

FIGS. 2A-2J show the gas suction pipe 150 of the centrifugal compressor according to the first embodiment of the present application, wherein FIG. 2A is a front perspective view of the gas suction pipe 150, FIG. 2B is a rear perspective view of the gas suction pipe 150, FIG. 2C is a front view of an inner contour of the gas suction pipe 150, FIG. 2D is a left view of the inner contour of the gas suction pipe 150, FIGS. 2E-2I are schematic diagrams of the first to fifth cross-sections in FIG. 2D, and FIG. 2J is a schematic diagram of an inner contour of a downstream interface of the gas suction pipe 150. As shown in FIGS. 2A-2C, the gas suction pipe 150 has an imaginary middle cross-section 250, and the middle cross-section 250 is coplanar with an axis of the centrifugal compressor, that is, the axis of the centrifugal compressor is located on the middle cross-section 250. The gas suction pipe 150 is a tubular structure that is symmetrical left and right with respect to the middle cross-section 250.

As still shown in FIGS. 2A-2C, the gas suction pipe 150 generally comprises three parts connected in sequence, including an inlet section 211, a transition section 212 and an outlet section 213. The inlet section 211 connects the gas suction pipe 150 to the evaporator 110, the outlet section 213 connects the gas suction pipe 150 to the compressor 120, and the transition section 212 connects the inlet section 211 to the outlet section 213. The refrigerant gas coming out of the evaporator 110 enters the inlet section 211 in a direction substantially perpendicular to the central axis X1 of the gas suction port 125 of the compressor 120, and enters the compressor 120 from the outlet section 213 in a direction generally along the central axis X1 of the gas suction port 125 of the compressor 120. Therefore, the flow direction of the refrigerant gas in the gas suction pipe 150 is generally deflected by 90°. Although the flow direction of the refrigerant gas is also slightly deflected in the inlet section 211 and the outlet section 213, the deflection of the flow direction mainly occurs to the transition section 212. The end face of the outlet section 213 connected to the gas suction port 125 of the compressor 120 is a downstream interface 226, which is generally annular and matches the gas suction port 125 of the compressor 120 in shape. Therefore, the inner contour of the downstream interface 226 is circular. The end face of the inlet section 211 connected to the evaporator 110 is an upstream interface 228.

The inlet section 211 comprises a connection part 241 and a guide part 242 which are connected to each other. The guide part 242 is located downstream of the connection part 241. The connection part 241 is used for achieving a mechanical connection between the gas suction pipe 150 and the evaporator 110. The upstream interface 228 is formed by the connection part 241, which forms a starting position of a fluid guide channel. As can be seen from FIGS. 2A-2D, an upstream portion of the inlet section 211 (including the connection part 241 and a portion of the guide part 242) is in the shape of protruding lugs located on two opposite sides of the middle cross-section 250 to match a top part of the cylindrical evaporator 110. Therefore, the upstream interface 228 is in the shape of an undulating wave.

Specifically, an inner contour of the upstream interface 228 comprises an upstream inside endpoint 231, an upstream outside endpoint 232, an upstream left-side endpoint 233 and an upstream right-side endpoint 234. The upstream inside endpoint 231 and the upstream outside endpoint 232 are located on the middle cross-section 250, and the upstream left-side endpoint 233 and the upstream right-side endpoint 234 are respectively located on two opposite sides of the middle cross-section 250. In the direction perpendicular to the axis X2 of the evaporator 110, the upstream inside endpoint 231 and the upstream outside endpoint 232 are located above the upstream left-side endpoint 233 and the upstream right-side endpoint 234. The upstream inside endpoint 231 and the upstream outside endpoint 232 are to be in contact with the top end of the cylindrical evaporator 110, and the upstream left-side endpoint 233 and the upstream right-side endpoint 234 are to be connected with the two opposite sides of the uppermost end of the cylindrical evaporator 110.

On the inner contour of the gas suction pipe 150, a connection line of the guide part 242 and the connection part 241 has a shape parallel to the upstream interface 228. The connection line of the guide part 242 and the connection part 241 intersects the middle cross-section 250 at an inner intersection point 245 and an outer intersection point 246.

A distance between the upstream inside endpoint 231 and the upstream outside endpoint 232 is D₁, and a distance between the upstream left-side endpoint 233 and the upstream right-side endpoint 234 is D₂. The distance D₁ between the upstream inside endpoint 231 and the upstream outside endpoint 232 is a first direction maximum spanning size of the inner contour of the upstream interface 228 located on the middle cross-section 250, and is also a maximum spanning size of the inner contour of the upstream interface 228 in the direction along the axis X2 of the evaporator 110. The distance D₂ between the upstream left-side endpoint 233 and the upstream right-side endpoint 234 is a second direction maximum spanning size of the inner contour of the upstream interface 228 in the direction perpendicular to the middle cross-section 250, and is also a maximum spanning size of the inner contour of the upstream interface 228 in the direction perpendicular to the axis X2 of the evaporator 110. The area of the upstream interface 228 determines a local loss ΔP1 of pressure when the refrigerant gas enters the gas suction pipe 150 from the evaporator 110.

Specifically, when the fluid enters the gas suction pipe 150 from the evaporator 110, there is a sudden shrinkage change in the fluid flow area from large to small at a fluid interface between a cylinder of the evaporator 110 and the gas suction pipe 150. Therefore, there is a loss of fluid pressure, that is, the local loss ΔP1, at the interface between the gas suction pipe 150 and the evaporator 110, and the size of a projected area A1 of the interface (i.e., the upstream interface 228) between the gas suction pipe 150 and the evaporator 110 on a projection plane 265 perpendicular to the middle cross-section 250 and parallel to the central axis X1 of the gas suction port 125 of the centrifugal compressor 120 directly determines the amount of the local loss ΔP1. More specifically, the local loss ΔP1 in the gas suction pipe is:

Δ ⁢ P ⁢ 1 = 0.5 * ( 1 - A 1 A 0 ) * V 1 2 2 * g ,

wherein A₁ is the projected area of the interface (i.e., the upstream interface 228) between the gas suction pipe 150 and the evaporator 110 on the projection plane 265, A₀ is the axial cross-sectional area of the evaporator 110, V₁ is the average flow velocity in the gas suction pipe 150, and g is the gravity acceleration.

To make the local loss ΔP1 decreased, the larger the area A₁ of the interface (i.e., the upstream interface 228) between the gas suction pipe 150 and the evaporator 110, the better. However, due to the limitation of the diameter of the cylinder of the evaporator, the distance D₂ (i.e., the maximum spanning size of the upstream interface 228 in the direction perpendicular to the axis of the evaporator 110) between the upstream left-side endpoint 233 and the upstream right-side endpoint 234 must satisfy: D₂<0.5×D₁ in order to achieve the requirements for the cylinder strength of the evaporator 110.

To this end, in the gas suction pipe according to the present application, the upstream interface 228 is set such that the distance D1 (i.e., the first direction maximum spanning size of the inner contour of the upstream interface 228 located on the middle cross-section 250) between the upstream inside endpoint 231 and the upstream outside endpoint 232 is greater than the distance D₂ (i.e., the second direction maximum spanning size of the inner contour of the upstream interface 228 in the direction perpendicular to the middle cross-section 250) between the upstream left-side endpoint 233 and the upstream right-side endpoint 234. Therefore, on the projection plane 265, the projection of the inner contour of the upstream interface 228 is elliptical, and the projected area A₁ is: A₁=pi×D₁×D₂, wherein pi is π.

By making the above settings for the upstream interface 228, in the present application, the local loss ΔP1 can be minimized to the greatest extent while the requirements for the cylinder strength of the evaporator 110 can be met, because by increasing the maximum spanning size D₁ of the upstream interface 228 in the direction along the axis X2 of the evaporator 110, the area A1 of the upstream interface 228 can be increased, thereby effectively reducing the local loss ΔP1.

According to some embodiments of the present application, the distance D₁ (the first direction maximum spanning size) between the upstream inside endpoint 231 and the upstream outside endpoint 232 and the distance D₂ (the second direction maximum spanning size) between the upstream left-side endpoint 233 and the upstream right-side endpoint 234 satisfy: 0.55<D₁/D₀<0.7, D₂<0.5×D₁. A radius R₆ of the inner contour of the downstream interface 226 satisfies: 0.43<R₆/D₁<0.57.

Since the projection of the inner contour of the upstream interface 228 on the projection plane 265 is elliptical, and the inner contour of the downstream interface 226 is circular, the cross-section of the portion of the gas suction pipe 150 between the upstream interface 228 and the downstream interface 226 gradually changes from being elliptical to being circular.

The gas suction pipe 150 has a centerline 270 located on the middle cross-section 250, and the centers of the cross-sections of the gas suction pipe 150 are all located on the centerline 270. The centerline 270 is a spline curve that satisfies the following formula:

Y = V 1 - V 2 1 + exp ⁢ ( X - V 3 V 4 ) + V 2 ,

wherein V₁, V₂, V₃, and V₄ satisfy the following relationship:

- 7 ⁢ e ⁢ 7 < V 1 < - 6 ⁢ e ⁢ 7 , 1 ⁢ 1 ⁢ 0 ⁢ 0 < V 2 < 1 ⁢ 3 ⁢ 00 , 
 - 2950 < V 3 < - 2 ⁢ 7 ⁢ 5 ⁢ 0 , 2 ⁢ 5 ⁢ 0 < V 4 < 2 ⁢ 7 ⁢ 0 .

The coordinate system involved in the above-mentioned formula takes the bottommost end (i.e., the intersection point of the centerline 270 and the projection plane 265) O₀ of the centerline 270 as the origin of the coordinate system, takes the direction parallel to the central axis X1 of the gas suction port 125 of the centrifugal compressor 120 as the X-axis direction, and takes the direction perpendicular to the central axis X1 of the gas suction port 125 of the centrifugal compressor 120 as the Y-axis direction, as shown in FIG. 2D.

As shown in FIG. 2D, the gas suction pipe 150 has a first cross-section 251, the first cross-section 251 passes through the inner intersection point 245 and the outer intersection point 246 and is perpendicular to the middle cross-section 250, and its center O₁ is located on the centerline 270. That is, the first cross-section 251 is parallel to the projection plane 265. Between the first cross-section 251 and the downstream interface 226 of the gas suction pipe 150, cross-sections of inner contours of the gas suction pipe 150 at least on the inlet section 211 and the transition section 212 are elliptical with major axes located on the middle cross-section 250, cross-sections of inner contours of the inlet section 211 and the outlet section 213 gradually decrease in the direction toward the downstream interface 226, and the cross-section of the inner contour of the transition section 212 first gradually increases and then decreases in the direction toward the downstream interface 226. That is, the gas suction pipe 150 forms a bulge-like shape on the transition section 212.

As one example, the above-mentioned gas suction pipe 150 is described using the sizes of a plurality of discrete cross-sections. As shown in FIG. 2D, the four cross-sections, which divide the portion of the gas suction pipe 150 located between the first cross-section 251 and the downstream interface 226 into five equal parts along the centerline 270, are a second cross-section 252, a third cross-section 253, a fourth cross-section 254 and a fifth cross-section 255, respectively. The centers of these cross-sections are all on the centerline 270, which are O₂, O₃, O₄ and O₅, respectively. The fourth cross-section 254 is the largest cross-section of the transition section 212. The first cross-section 251 and the downstream interface 226, as well as the size characteristics of each of the above cross-sections are as follows.

The included angle α₆ between the downstream interface 226 and the first cross-section 251 and the radius R₆ of the downstream interface 226 satisfy:

80 ⁢ ° ≤ α 6 ≤ 90 ⁢ ° , 0.43 < R 6 / D 1 < 0 . 5 ⁢ 7 .

The major axis radius R1max and the minor axis radius R1min of the first cross-section 251 respectively satisfy: R_1max=0.5×D₁, 0.9<R_1min/R_1max<0.95.

The included angle α₂ between the second cross-section 252 and the first cross-section 251 and the major axis radius R_2max and the minor axis radius R_2min of the second cross-section 252 respectively satisfy: 0.1<α₂/α₆<0.15, 0.68<R_2max/D₁<0.78, 0.92<R_2min/R_2max<0.98.

The included angle α₃ between the third cross-section 253 and the first cross-section 251 and the major axis radius R_3max and the minor axis radius R_3min of the third cross-section 253 respectively satisfy: 0.25<α₃/α₆<0.38, 0.6<R_3max/D₁<0.76, 0.8<R_3min/R_3max<0.9.

The included angle α₄ between the fourth cross-section 254 and the first cross-section 251 and the major axis radius R_4max and the minor axis radius R_4min of the fourth cross-section 254 respectively satisfy: 0.45<α₄/α₆<0.6, 0.6<R_4max/D₁<0.74, 0.84<R_4min/R_4max<0.92.

The included angle as between the fifth cross-section 255 and the first cross-section 251 and the major axis radius R_5max and the minor axis radius R_5min of the fifth cross-section 255 respectively satisfy: 0.7<α₅/α₆<0.8, 0.45<R_5max/D₁<0.6, 0.98<R_5min/R_5max<1.05.

It can be seen that the first to fourth cross-sections are all elliptical with the major axes located on the middle cross-section 250, and the minor axis of the fifth cross-section 255 can be longer than the major axis, can be equal to the major axis, or can be shorter than the major axis. Therefore, the fifth cross-section 255 can be circular.

By forming the above cross-sections, the upstream interface 228, the downstream interface 226 and the centerline 270, the inner contour of the gas suction pipe 150 can be formed, and then the gas suction pipe 150 can be formed by adding a wall with a specific thickness.

FIG. 3A is a schematic diagram showing a fluid flow state of a gas suction pipe 310 in one comparative example when in use, and FIG. 3B is a schematic diagram showing a fluid flow state of the gas suction pipe 150 according to the first embodiment of the present application when in use. As shown in FIG. 3A, in one comparative example, the gas suction pipe 310 is in a circular tube shape as a whole, and the inlet section 311 of the gas suction pipe 310 is a straight pipe section perpendicular to the evaporator 320. Due to the sudden change in the interface area between the evaporator 320 and the gas suction pipe 310, there is the local pressure loss ΔP₁ in the process of the refrigerant gas entering the gas suction pipe 310 from the evaporator 320. In addition, the refrigerant gas may produce a pressure loss ΔP₂ in the inlet section 311 which is in a straight tube shape, because when the fluid enters the gas suction pipe 310 from the evaporator 320, the flow direction is greatly deflected, and the fluid may produce flow separation and vortexes at the place where the flow deflection is large. In addition, the refrigerant gas has a pressure loss ΔP₃ in the transition section 312 of the gas suction pipe 310. This is due to the large deflection of fluid steering in the transition section 312. The deflection of the fluid steering causes uneven distribution of velocity in the transition section 312 of the gas suction pipe, which intensifies the internal friction in the mainstream, causes the front and rear impact of fluid microclusters, and increases the turbulence in the mainstream, thereby causing a loss of pressure and energy. The refrigerant gas also has a pressure loss ΔP₄ in the outlet section 313 of the gas suction pipe 310. This is due to the existence of a local high-speed zone near the inside of the gas suction pipe, which increases the internal friction of the fluid and causes the pressure loss.

As shown in FIG. 3B, the gas suction pipe 150 according to the first embodiment of the present application is capable of greatly reducing the pressure loss ΔP₁, ΔP₂, ΔP₃ and ΔP₄ existing in the above-mentioned comparative example. The reason for reducing the local pressure loss ΔP₁ has been detailed before and will not be repeated here. The gas suction pipe 150 of the present application can also reduce the pressure loss ΔP₂ of the inlet section, because the cross-section of the inlet section 211 of the gas suction pipe 150 of the present application gradually decreases, thus decreasing the amplitude of the flow direction deflection when the fluid enters the gas suction pipe 310 from the evaporator 320. The gas suction pipe 150 of the present application can also reduce the pressure loss ΔP₃ of the transition section, because the cross-section of the transition section 212 first increases and then decreases, which is capable of decreasing the uneven distribution of velocity caused by the deflection of the steering. The gas suction pipe 150 of the present application can also reduce the pressure loss ΔP₄ of the outlet section, because the process of first increasing and then decreasing the cross-section of the transition section 212 decreases the flow rate in the outlet section 313 at the local high-speed zone on the inside of the gas suction pipe.

FIGS. 3C and 3D respectively show velocity vector diagrams in the gas suction pipe obtained by adopting a CFD (computational fluid dynamics) method for the gas suction pipe 310 of the comparative example shown in FIG. 3A and the gas suction pipe 150 of the present application shown in FIG. 3B. It can be seen from the CFD simulation results that the gas suction pipe 310 of the comparative example shown in FIG. 3A has two turbulent vortex areas (the darker areas in the figure) on the left and right sides of the bottom of the gas suction pipe, while turbulent vortexes have basically eliminated on the left and right sides of the bottom of the gas suction pipe 150 of the present application shown in FIG. 3B, which can effectively reduce the pressure loss. As shown in Table 1 below, the pressure loss of the gas suction pipe 150 of the present application shown in FIG. 3B is reduced by 17% compared to the gas suction pipe 310 of the comparative example shown in FIG. 3A.

FIGS. 3E and 3F respectively show velocity vector diagrams at the downstream interface of the gas suction pipe (i.e., at the compressor inlet) obtained by adopting the CFD (computational fluid dynamics) method for the gas suction pipe 310 of the comparative example shown in FIG. 3A and the gas suction pipe 150 of the present application shown in FIG. 3B; FIGS. 3G and 3H respectively show vortex intensity diagrams at the downstream interface of the gas suction pipe (i.e., the compressor inlet) obtained by adopting the CFD (computational fluid dynamics) method for the gas suction pipe 310 of the comparative example shown in FIG. 3A and the gas suction pipe 150 of the present application shown in FIG. 3B. The velocity distribution status at the downstream interface of the gas suction pipe (i.e., at the compressor inlet) has a great impact on the performance of the compressor. The more even the velocity distribution at the compressor inlet, the higher the efficiency of the compressor. The impact of the gas suction pipe on the performance of the compressor can be judged by the vortex intensity at the interface end face of the gas suction pipe and the compressor. Generally speaking, the smaller the vortex intensity, the better the efficiency of the compressor. As can be seen from FIGS. 3E-3H, the velocity distribution of the gas suction pipe 150 of the present application at the downstream interface of the gas suction pipe (i.e., at the compressor inlet) is more even, and the vortex intensity is significantly decreased (the darker the color, the higher the flow rate and the greater the vortex intensity). In addition, it can be seen from Table 1 that the vortex intensity of the gas suction pipe 150 of the present application is reduced by 74% compared to the existing gas suction pipe, which can greatly improve the inlet conditions of the compressor and enhance the performance of the compressor.

FIGS. 4A-4D show the gas suction pipe 450 of the centrifugal compressor according to the second embodiment of the present application, wherein FIG. 4A is a front perspective view of the gas suction pipe 450, FIG. 4B is a rear perspective view of the gas suction pipe 450, FIG. 4C is a front view of the inner contour of the gas suction pipe 450, FIG. 4D is a left view of the inner contour of the gas suction pipe 450, FIGS. 4E-4I are schematic diagrams of the first to fifth cross-sections in FIG. 4D, and FIG. 4J is a schematic diagram of the inner contour of the downstream interface of the gas suction pipe 450. The main difference between the gas suction pipe 450 of the second embodiment shown in FIGS. 4A-4J and the gas suction pipe 150 of the first embodiment shown in FIGS. 2A-2J is that the cross-section of the inner contour of the transition section 612 of the gas suction pipe 150 of the first embodiment first gradually increases and then gradually decreases, while the cross-section of the inner contour of the transition section 612 of the gas suction pipe 450 of the second embodiment does not have an increasing portion, but gradually decreases in the direction toward the downstream interface 626. That is, the cross-section of the inner contour of the gas suction pipe 450 of the second embodiment gradually decreases in the direction from the first cross-section 651 (with the center being O₁₁) to the downstream interface 626. As shown in Table 1 below, the gas suction pipe 450 of the second embodiment, like the gas suction pipe 150 of the first embodiment, can decrease the static pressure loss in the pressure loss gas suction pipe and the vortex intensity at the downstream interface of the gas suction pipe.

Same as the first embodiment, the distance (first direction maximum spanning size) D₁₁ between the upstream inside endpoint 631 and the upstream outside endpoint 632 of the gas suction pipe 450 of the second embodiment and the distance (second direction maximum spanning size) D₁₂ between the upstream left-side endpoint 633 and the upstream right-side endpoint 634 satisfy: 0.55<D₁₁/D₀<0.7, D₁₂<0.5×D₁₁. The radius R₁₆ of the inner contour of the downstream interface 626 satisfies: 0.43<R₁₆/D₁₁<0.57, wherein Do is the diameter of the upstream component, that is, evaporator.

As one example, the above-mentioned gas suction pipe 450 is described using the sizes of a plurality of discrete cross-sections. As shown in FIG. 2D, the four cross-sections, which divide the portion of the gas suction pipe 450 located between the first cross-section 651 and the downstream interface 626 into five equal parts along the centerline 670, are a second cross-section 652, a third cross-section 653, a fourth cross-section 654 and a fifth cross-section 655, respectively. The centers of these cross-sections are all on the centerline 670, which are O₁₂, O₁₃, O₁₄ and O₁₅, respectively. The fourth cross-section 654 is the largest cross-section of the transition section 612. The first cross-section 651 and the downstream interface 626, as well as the size characteristics of each of the above cross-sections are as follows.

The included angle α₁₆ between the downstream interface 626 and the first cross-section 651 and the radius R₁₆ of the downstream interface 626 satisfy:

80 ⁢ ° ≤ α 1 ⁢ 6 ≤ 90 ⁢ ° , 0.43 < R 1 ⁢ 6 / D 1 ⁢ 1 < 0 . 5 ⁢ 7 .

The major axis radius R_11max and the minor axis radius R_12min of the first cross-section 651 respectively satisfy: R_11max=0.5×D₁₁, 0.9<R_11min/R_11max<0.95.

The included angle α₁₂ between the second cross-section 652 and the first cross-section 651 and the major axis radius R_12max and the minor axis radius R_12min of the second cross-section 652 respectively satisfy: 0.1<α₁₂/α₁₆<0.15, 0.68<R_12max/D₁₁<0.78, 0.92<R_12min/R_12max<0.98.

The included angle α₁₃ between the third cross-section 653 and the first cross-section 651 and the major axis radius R_13max and the minor axis radius R_13min of the third cross-section 653 respectively satisfy: 0.25<α₁₃/α₁₆<0.38, 0.55<R_13max/D₁₁<0.7, 0.8<R_13min/R_13max<0.9.

The included angle α₁₄ between the fourth cross-section 654 and the first cross-section 651 and the major axis radius R_14max and the minor axis radius R_14min of the fourth cross-section 654 respectively satisfy: 0.45<α₁₄/α₁₆<0.6, 0.5<R_14max/D₁₁<0.6, 0.9<R_14min/R_14max<0.95.

The included angle α₁₅ between the fifth cross-section 655 and the first cross-section 651 and the major axis radius R_15max and the minor axis radius R_15min of the fifth cross-section 655 respectively satisfy: 0.7<α₁₅/α₁₆<0.8, 0.45<R_15max/D₁₁<0.6, 0.98<R_15min/R_15max<1.05.

The following Table 1 shows a performance comparison table of the gas suction pipes of the two embodiments of the present application and the gas suction pipe of the comparative example in terms of static pressure loss and vortex intensity.

Although the present disclosure has been described in conjunction with the examples of embodiments outlined above, various alternatives, modifications, variations, improvements and/or substantial equivalents, whether known or foreseeable now or soon, may become apparent to those of ordinary skill in the art. In addition, the technical effects and/or technical problems described in this specification are exemplary rather than restrictive. Therefore, the disclosure in this specification may be used for solving other technical problems and have other technical effects. Accordingly, the examples of embodiments of the present disclosure set forth above are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit or scope of the present disclosure. Accordingly, the present disclosure is intended to embrace all known or earlier developed alternatives, modifications, variations, improvements and/or substantial equivalents.