A centrifugal compressor diffuser and a centrifugal compressor

Abstract

This invention provides a centrifugal compressor diffuser and a centrifugal compressor. The centrifugal compressor diffuser includes a housing and blades. The blades are disposed on the inner wall of the housing. An xy-axis coordinate system is established with a single blade as a reference, the flow direction of the airflow in the housing as the x-axis, the leading edge of the blade as point O, and the direction perpendicular to the x-axis as the y-axis. A blade mid-arc installation angle β is defined between the tangent at each position on the mid-arc line and the y-axis. The distribution of the blade mid-arc installation angle along the flow direction follows a cubic function: β = A1 + B1x1 + C1x1 2 +D1x1 3 Where x1 is the x-value at any position on the middle arc divided by the projected length of the total length of the middle arc on the x-axis, 0≤x1≤1. According to the present invention, the air at the suction surface does not separate during the downstream flow, no low Mach number region is generated at the suction surface, the backflow at the hub position of the diffuser suction surface is eliminated, and the airflow impact loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, specifically to a centrifugal compressor diffuser and a centrifugal compressor. Background Technology

[0002] As a key component of the air circulator and an upstream component of the turbine, the compressor decelerates and pressurizes incoming low-pressure air, driving high-pressure air further into the turbine to complete the expansion and work process. Therefore, the compressor's pressurization capacity directly affects the turbine's work capacity, and consequently, the air circulator's system performance. The compressor impeller directly influences the total gas pressure rise within the compressor. The diffuser downstream of the impeller acts as a decelerator and diffuser, and it must work well with the compressor impeller to ensure high efficiency and pressure ratio under redesign conditions.

[0003] Because existing technologies suffer from backflow at the hub position of the diffuser suction surface, resulting in significant airflow impact loss and entropy increase, this invention researches and designs a centrifugal compressor diffuser and a centrifugal compressor. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of backflow at the hub position of the diffuser suction surface in the prior art, thereby providing a centrifugal compressor diffuser and a centrifugal compressor.

[0005] To address the above problems, the present invention provides a centrifugal compressor diffuser, comprising:

[0006] The shell and the blades, the blades are disposed on the inner wall of the shell, and an xy-axis coordinate system is established with a single blade as the reference, the flow direction of the airflow in the shell as the x-axis, the leading edge of the blade as point O, and the direction perpendicular to the x-axis as the y-axis;

[0007] The blade also includes a trailing edge, a pressure surface, and a suction surface. The mid-arc line of the blade is an arc segment connecting the leading edge and the trailing edge of the blade. The minimum distance from each point on the mid-arc line to the pressure surface and the suction surface is equal.

[0008] Furthermore, the angle between the tangent at each position on the mid-arc line and the y-axis is the blade mid-arc installation angle β, and the distribution of the blade mid-arc installation angle along the flow direction follows a cubic function: β=A1+B1x1+C1x1 2 +D1x1 3 , where x1 is the x value at any position on the middle arc divided by the projection length of the total length of the middle arc on the x-axis, 0≤x1≤1, and β is the blade middle arc installation angle corresponding to that position.

[0009] In some implementations, A1 = 76.288 ± 0.006, B1 = -59.586 ± 0.058, C1 = 113.578 ± 0.137, and D1 = -65.873 ± 0.091.

[0010] In some embodiments, the blade chord length is a straight line segment connecting the leading edge and trailing edge of the blade, denoted by C, and the blade thickness h is the distance between the pressure surface and the suction surface at any position on the blade along the vertical direction of the blade chord length.

[0011] The distribution pattern of blade thickness follows a cubic function: h = A² + B²x¹ + C²x¹ 2 +D2x1 3 , where x1 is the x value at any position on the middle arc divided by the projection length of the total length of the middle arc on the x-axis, 0≤x1≤1, and h is the blade thickness corresponding to that position.

[0012] In some implementations, A2 = 0.389 ± 0.004, B2 = 8.688 ± 0.003, C2 = 1.743 ± 0.007, and D2 = -10.298 ± 0.004.

[0013] In some embodiments, the throat is defined as the minimum distance between two adjacent blades at any given location; this distance is the throat distance at that location, and the throat area S is the throat distance multiplied by the blade height; and:

[0014] The throat area S is distributed along the flow direction according to a quintic function: S = A³ + B³x¹ + C³x¹ 2 +D3x1 3 +E3x1 4 +F3x1 5 , where x1 is the x-value at any position on the middle arc divided by the projection length of the total length of the middle arc onto the x-axis, 0≤x1≤1, and S is the throat area corresponding to that position.

[0015] In some implementations, A3 = 37.426 ± 0.377, B3 = -301.008 ± 4.455, C3 = 1154.700 ± 20.081, D3 = -2052.157 ± 43.322, E3 = 1679.370 ± 44.920, and F3 = -478.755 ± 17.983.

[0016] In some implementations, the distance between the trailing edges of two adjacent blades along the y-axis is the pitch L, and the blade consistency δ = C / L.

[0017] In some embodiments, the number of blades is 13, and the diffuser outlet total pressure / inlet total pressure

[0018] =0.985±0.02.

[0019] The present invention also provides a centrifugal compressor, which includes the aforementioned centrifugal compressor diffuser.

[0020] The centrifugal compressor diffuser and centrifugal compressor provided by this invention have the following beneficial effects:

[0021] This invention sets the installation angle of the arc line in the blade to follow a cubic function along the flow direction: β = A1 + B1x1 + C1x1 2 +D1x1 3 Especially A1 = 76.288 ± 0.006, B1 = -59.586 ± 0.058,

[0022] C1 = 113.578 ± 0.137, D1 = -65.873 ± 0.091, which ensures that in the optimized diffuser channel, the airflow at the diffuser inlet adheres to the blades as it enters the channel. Airflow on the suction surface does not separate during downstream flow, and no low Mach number region is generated on the suction surface. This effectively eliminates backflow at the hub position of the original diffuser suction surface, thereby reducing airflow impact losses. Furthermore, this invention ensures that the blade thickness distribution follows a cubic function: h = A² + B²x¹ + C²x¹ 2 +D2x1 3 Especially A2 = 0.389 ± 0.004, B2 = 8.688 ± 0.003,

[0023] C2 = 1.743 ± 0.007, D2 = -10.298 ± 0.004, and the throat area S along the flow direction follows a quintic function: S = A3 + B3x1 + C3x1 2 +D3x1 3 +E3x1 4 +F3x1 5 Especially A3 = 37.426 ± 0.377,

[0024] With B3 = -301.008 ± 4.455, C3 = 1154.700 ± 20.081, D3 = -2052.157 ± 43.322, E3 = 1679.370 ± 44.920, and F3 = -478.755 ± 17.983, the optimized diffuser channel entropy is significantly lower than the initial design. There is no high-entropy region within the channel, with relatively high entropy values ​​only occurring on the blade surface and in the wake region. Therefore, this diffuser ensures that the incoming air adheres to the blade surface as it enters the channel and does not experience suction separation during downstream flow. It also suppresses unnecessary losses within the channel, controlling entropy increase within the blade surface boundary layer, with no significant losses within the channel. Attached Figure Description

[0025] Figure 1 This is a structural diagram of the centrifugal compressor diffuser of the present invention;

[0026] Figure 2 This is an assembly structure diagram of the centrifugal compressor diffuser and volute of the present invention;

[0027] Figure 3 This is a schematic diagram of the blade structure of the centrifugal compressor diffuser of the present invention;

[0028] Figure 4 This is a distribution curve of the blade mounting angle along the flow direction of the present invention;

[0029] Figure 5 This is a graph showing the distribution of blade thickness along the flow direction according to the present invention;

[0030] Figure 6 This is a distribution curve of the throat area of ​​the diffuser of the present invention along the flow direction;

[0031] Figure 7 This is a Mach number distribution diagram in the diffuser channel optimized by the present invention (compared with existing solutions);

[0032] Figure 8 This is an entropy distribution diagram within the diffuser channel optimized by the present invention (compared with existing solutions).

[0033] The reference numerals in the attached figures are as follows:

[0034] 1. Shell; 2. Blade; 21. Leading edge; 22. Trailing edge; 23. Pressure surface; 24. Suction surface; 25. Mid-curve; 3. Throat; 4. Volute. Detailed Implementation

[0035] like Figure 1-8 As shown, the present invention provides a centrifugal compressor diffuser, which includes:

[0036] A housing 1 and a blade 2 are provided. The blade 2 is disposed on the inner wall of the housing 1. A coordinate system is established with a single blade 2 as a reference, the flow direction of the airflow in the housing 1 as the x-axis, the leading edge 21 of the blade 2 as point O, and the direction perpendicular to the x-axis as the y-axis.

[0037] The blade 2 also includes a trailing edge 22, a pressure surface 23, and a suction surface 24. The middle arc 25 of the blade is an arc segment connecting the leading edge 21 and the trailing edge 22 of the blade 2. The minimum distance from each point on the middle arc 25 to the pressure surface 23 and the suction surface 24 is equal.

[0038] Furthermore, the angle between the tangent at each position on the mid-arc line 25 and the y-axis is the blade mid-arc installation angle β, and the distribution of the blade mid-arc installation angle along the flow direction follows a cubic function: β=A1+B1x1+C1x1 2 +D1x1 3 , where x1 is the x value at any position on the middle arc divided by the projection length of the total length of the middle arc on the x-axis, 0≤x1≤1, and β is the blade middle arc installation angle corresponding to that position.

[0039] This invention sets the installation angle of the arc line in the blade to follow a cubic function along the flow direction: β = A1 + B1x1 + C1x1 2 +D1x1 3 Especially A1 = 76.288 ± 0.006, B1 = -59.586 ± 0.058,

[0040] With C1 = 113.578 ± 0.137 and D1 = -65.873 ± 0.091, the optimized diffuser channel allows the airflow at the diffuser inlet to enter the channel in close contact with the blades. The air on the suction surface does not separate during its downstream flow, and no low Mach number region is generated on the suction surface. This effectively eliminates the backflow at the hub position of the original diffuser suction surface, thereby reducing airflow impact losses.

[0041] This invention solves the following technical problems:

[0042] 1. This invention eliminates the backflow at the hub position of the original diffuser suction surface (because the air on the suction surface does not separate during the downstream flow, there is no low Mach number region on the suction surface);

[0043] 2. The airflow at the diffuser inlet conforms to the blades as it enters the flow channel, reducing airflow impact losses;

[0044] 3. This invention controls entropy increase within the blade surface boundary layer, with no significant loss within the flow channel.

[0045] In some implementations, A1 = 76.288 ± 0.006, B1 = -59.586 ± 0.058, C1 = 113.578 ± 0.137, and D1 = -65.873 ± 0.091.

[0046] Figure 3 This is a schematic diagram of some geometric design parameters of the diffuser blades, including the diffuser's installation angle, pitch, arc length, and flow direction. These geometric parameters can be determined using the following design methods.

[0047] Diffuser inlet design:

[0048] 1. Determine the total parameters of the diffuser inlet gas state, such as total temperature and total pressure;

[0049] 2. Given the diffuser inlet radius, calculate the tangential velocity at the diffuser inlet using the law of conservation of angular momentum;

[0050] 3. The airflow angle at the diffuser inlet can be calculated using the flow function, thereby determining the blade inlet installation angle β;

[0051] 4. After completing the above calculations, the flow velocity component at the diffuser inlet can be determined, and the static parameters of the gas state at the inlet can then be obtained.

[0052] Diffuser outlet design:

[0053] 5. Given the outlet installation angle of the diffuser blades;

[0054] 6. Give the ratio of the diffuser outlet radius to the inlet radius;

[0055] 7. Calculate the diffuser blade arc length, equivalent expansion angle, consistency, etc., and determine whether the equivalent expansion angle and consistency are within a reasonable range. If the requirements are met, the design process can be completed. If not, it is necessary to return to step 5 for a new round of iterative design.

[0056] After determining the aforementioned geometric parameters, the three-dimensional design of the blade can then be developed, including determining the blade's installation angle and thickness distribution along the flow direction. For example... Figure 4 As shown, the distribution of the arc installation angle of the diffuser blades along the flow direction follows a cubic function: β=A1+B1x1+C1x1 2 +D1x1 3 The coefficient values ​​are shown in Table 1 (x1 is the relative position along the flow direction 0≤x1≤1, β is the blade installation angle of the corresponding relative position along the flow direction). Thus, the distribution of the blade installation angle along the flow direction can be determined.

[0057] Table 1. Flow-direction distribution function coefficients of the mid-arc installation angle of diffuser blades.

[0058] coefficient value <![CDATA[A1]]> 76.288±0.006 <![CDATA[B1]]> -59.586±0.058 <![CDATA[C1]]> 113.578±0.137 <![CDATA[D1]]> -65.873±0.091

[0059] In some embodiments, the blade chord length is the straight line segment connecting the leading edge 21 and trailing edge 22 of the blade 2, denoted by C (i.e., the blade chord length is C), the blade thickness h is the distance between the pressure surface 23 and the suction surface 24 at any position on the blade along the vertical direction of the blade chord length.

[0060] The distribution pattern of blade thickness follows a cubic function: h = A² + B²x¹ + C²x¹ 2 +D2x1 3 , where x1 is the x value at any position on the middle arc divided by the projection length of the total length of the middle arc on the x-axis, 0≤x1≤1, and h is the blade thickness corresponding to that position.

[0061] This invention determines the distribution pattern of blade thickness according to a cubic function: h = A² + B²x¹ + C²x¹ 2 +D2x1 3 In particular, A2 = 0.389 ± 0.004, B2 = 8.688 ± 0.003, C2 = 1.743 ± 0.007, D2 = -10.298 ± 0.004, and the throat area S along the flow direction follows a quintic function: S = A3 + B3x1 + C3x1 2 +D3x1 3 +E3x1 4 +F3x1 5 In particular, A3 = 37.426 ± 0.377, B3 = -301.008 ± 4.455, C3 = 1154.700 ± 20.081, D3 = -2052.157 ± 43.322, E3 = 1679.370 ± 44.920, and F3 = -478.755 ± 17.983, which makes the entropy value inside the optimized diffuser channel significantly lower than that of the initial design. There is no high-entropy region in the channel, and relatively high entropy values ​​are only generated on the blade surface and the wake region. Therefore, the diffuser can ensure that the incoming air adheres to the blade surface when entering the channel and does not produce suction surface separation during the downstream flow. At the same time, it suppresses unnecessary losses in the channel, controls the entropy increase within the blade surface boundary layer, and has no significant losses in the channel.

[0062] In some implementations, A2 = 0.389 ± 0.004, B2 = 8.688 ± 0.003, C2 = 1.743 ± 0.007, and D2 = -10.298 ± 0.004.

[0063] The blade thickness varies along the flow direction from Figure 5 The thickness distribution follows a cubic function: h = A² + B²x¹ + C²x¹ 2 +D2x1 3 The coefficient values ​​are shown in Table 2 (x1 represents the relative position along the flow direction, 0 ≤ x1 ≤ 1, and h represents the blade thickness at the corresponding relative position along the flow direction). Furthermore, the blade thickness is symmetrically distributed on both sides of the mid-arc line, with the mid-arc line as the reference. Therefore, the blade thickness is determined.

[0064] Table 2. Values ​​of the blade thickness distribution function along the flow direction.

[0065] coefficient value <![CDATA[A2]]> 0.389±0.004 <![CDATA[B2]]> 8.688±0.003 <![CDATA[C2]]> 1.743±0.007 <![CDATA[D2]]> -10.298±0.004

[0066] In some embodiments, the throat 3 is defined as the minimum distance between two adjacent blades at any given location. This distance is the throat distance at that location, and the throat area S is the throat distance multiplied by the blade height (the blade is an extended body, and the blade height is its length in the extended direction, i.e., as shown in the figure). Figure 3The blade length perpendicular to the paper plane is shown (the blade height); and we have:

[0067] The throat area S is distributed along the flow direction according to a quintic function: S = A³ + B³x¹ + C³x¹ 2 +D3x1 3 +E3x1 4 +F3x1 5 , where x1 is the x-value at any position on the middle arc divided by the projection length of the total length of the middle arc onto the x-axis, 0≤x1≤1, and S is the throat area corresponding to that position.

[0068] In some implementations, A3 = 37.426 ± 0.377, B3 = -301.008 ± 4.455, C3 = 1154.700 ± 20.081, D3 = -2052.157 ± 43.322, E3 = 1679.370 ± 44.920, and F3 = -478.755 ± 17.983.

[0069] In summary, it can be further determined that the distribution pattern of its throat area along the flow direction follows a quintic function: S = A³ + B³x¹ + C³x¹ 2 +D3x1 3 +E3x1 4 +F3x1 5 The coefficient values ​​are shown in Table 3 (x1 is the relative position along the flow direction, 0.2≤x1≤0.8, and S is the flow area of ​​the diffuser throat at the corresponding relative position along the flow direction).

[0070] Table 3. Coefficients of the throat area distribution function along the flow direction.

[0071] coefficient value <![CDATA[A3]]> 37.426±0.377 <![CDATA[B3]]> -301.008±4.455 <![CDATA[C3]]> 1154.700±20.081 <![CDATA[D3]]> -2052.157±43.322 <![CDATA[E3]]> 1679.370±44.920 <![CDATA[F3]]> -478.755±17.983

[0072] In some embodiments, the distance between the trailing edges of two adjacent blades 2 along the y-axis is the pitch L, and the blade consistency δ = C / L.

[0073] Figure 7 To ensure the Mach number distribution within the diffuser channel of the centrifugal compressor under the design conditions of this invention, the initial design and the optimized design maintained a good flow state at the inlet. Furthermore, within the optimized diffuser channel, the air on the suction surface did not separate during downstream flow, and no low Mach number region was generated on the suction surface.

[0074] Figure 8The optimized diffuser channel exhibits significantly lower entropy than the initial design under the specified operating conditions. Furthermore, the optimized design only generates relatively high entropy values ​​on the blade surface and in the wake region, losses that are unavoidable. Moreover, the optimized channel lacks high-entropy regions. Therefore, this diffuser ensures that incoming air adheres to the blade surface upon entering the channel and does not experience suction separation during downstream flow, while simultaneously suppressing unnecessary losses within the channel.

[0075] In some embodiments, the number of blades 2 is 13, and the diffuser outlet total pressure / inlet total pressure = 0.985 ± 0.02. See Table 4 below:

[0076] Table 4 Comparison of Initial and Optimized Schemes

[0077]

[0078] Table 4 shows a comparison between the optimized scheme of the present invention and the initial scheme before optimization. The optimized scheme greatly reduces the number of blades and significantly reduces the losses caused by air flowing in the diffuser.

[0079] The present invention also provides a centrifugal compressor, which includes the aforementioned centrifugal compressor diffuser.

[0080] This invention proposes a centrifugal compressor diffuser and a design concept for a low-consistency diffuser suitable for low-pressure ratio centrifugal compressors. This approach enables the identification of a suitable low-consistency diffuser type for most low-pressure compressors. Furthermore, this design concept can suppress the generation of separation vortices on the diffuser's suction surface, eliminating the resulting losses and improving the diffuser's aerodynamic performance. The centrifugal compressor diffuser proposed using this method has the following advantages: the rotor inlet flow can be perfectly matched with the blade geometry, effectively suppressing impact losses caused by the angle of attack. While meeting performance requirements, the diffuser's mass can be reduced by decreasing the number of blades, thus lowering the machining difficulty.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A centrifugal compressor diffuser, characterized in that: include: A housing (1) and a blade (2), wherein the blade (2) is disposed on the inner wall of the housing (1). A coordinate system is established with a single blade (2) as a reference, the flow direction of the airflow in the housing (1) as the x-axis, the leading edge (21) of the blade (2) as point O, and the direction perpendicular to the x-axis as the y-axis. The blade (2) also includes a trailing edge (22), a pressure surface (23) and a suction surface (24). The middle arc (25) of the blade is an arc segment connecting the leading edge (21) and the trailing edge (22) of the blade (2). The minimum distance from each point on the middle arc (25) to the pressure surface (23) and the suction surface (24) is equal. Furthermore, the angle between the tangent at each position on the mid-arc line (25) and the y-axis is the blade mid-arc installation angle β, and the distribution law of the blade mid-arc installation angle along the flow direction follows a cubic function: β=A1+B1x1+C1x1 2 +D1x1 3 , where x1 is the x value at any position on the middle arc divided by the projection length of the total length of the middle arc on the x-axis, 0≤x1≤1, and β is the blade middle arc installation angle corresponding to that position; A1=76.288±0.006, B1=-59.586±0.058, C1=113.578±0.137, D1=-65.873±0.

091.

2. The centrifugal compressor diffuser according to claim 1, characterized in that: The blade chord length is the straight line segment connecting the leading edge (21) and trailing edge (22) of the blade (2), denoted by C. The blade thickness h is the distance between the pressure surface (23) and the suction surface (24) at any position on the blade along the vertical direction of the blade chord length. The distribution pattern of blade thickness follows a cubic function: h = A² + B²x¹ + C²x¹ 2 +D2x1 3 , where x1 is the x value at any position on the middle arc divided by the projection length of the total length of the middle arc on the x-axis, 0≤x1≤1, and h is the blade thickness corresponding to that position.

3. The centrifugal compressor diffuser according to claim 2, characterized in that: A2=0.389±0.004, B2=8.688±0.003, C2=1.743±0.007, D2=-10.298±0.

004.

4. The centrifugal compressor diffuser according to any one of claims 1-3, characterized in that: The throat (3) is the minimum distance between two adjacent blades at any position. This distance is the throat distance at that position, and the throat area S is the throat distance multiplied by the blade height. And there are: The throat area S is distributed along the flow direction according to a quintic function: S = A³ + B³x¹ + C³x¹ 2 +D3x1 3 +E3x1 4 +F3x1 5 , where x1 is the x-value at any position on the middle arc divided by the projection length of the total length of the middle arc onto the x-axis, 0≤x1≤1, and S is the throat area corresponding to that position.

5. The centrifugal compressor diffuser according to any one of claims 1-3, characterized in that: A3=37.426±0.377, B3=-301.008±4.455, C3=1154.700±20.081, D3=-2052.157±43.322, E3=1679.370±44.920, F3=-478.755±17.

983.

6. The centrifugal compressor diffuser according to claim 2, characterized in that: The distance between the trailing edges of two adjacent blades (2) along the y-axis is the pitch L, and the blade density δ = C / L.

7. The centrifugal compressor diffuser according to claim 2, characterized in that: The number of blades (2) is 13, and the total pressure at the diffuser outlet / the total pressure at the inlet is 0.985 ± 0.

02.

8. A centrifugal compressor, characterized in that: Includes the centrifugal compressor diffuser according to any one of claims 1-7.

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