A composite blade and a compressor blade diffuser

Abstract

This invention proposes a composite blade and a compressor blade diffuser, featuring a unique blade shape and uniform circumferential arrangement. The blade is a two-section airfoil-shaped blade: a half-height front section and a full-height rear section. The front and rear sections meet after the throat of the diffuser duct, and the rear section features a completely new airfoil design at the head. This blade shape improves the design of the number of blades required for a diffuser and the problem of excessive flow blockage. This design combines the advantages of a half-height diffuser with the wide stable operating range and the manufacturing advantages of a two-blade diffuser. The blades remain two-piece, effectively reducing the difficulty of processing and installation.

Description

Technical Field

[0001] The invention relates to a diffuser structure, in particular to a centrifugal compressor blade diffuser. Background Art

[0002] In a centrifugal compressor, the main function of the diffuser is to increase the gas pressure by reducing the air flow velocity at the impeller outlet. The energy loss of the air flow in the diffuser accounts for most of the loss of the static components of the centrifugal compressor, and has a great impact on the overall structure and aerodynamic performance of the compressor.

[0003] Common diffusers are divided into bladeless diffusers, vane diffusers, and straight-wall diffusers. The structural design and manufacturing of bladeless diffusers are simple, and the airflow direction angle α remains basically unchanged, but the airflow flow path is long, the flow loss is large, and the diffusion efficiency is low. The shape and installation of the blades in the vane diffuser cause the gas flow direction angle α to gradually increase, and the airflow flow path length is controlled, thereby reducing flow losses and improving diffusion efficiency. However, due to the influence of the blade thickness of the vane diffuser, the airflow is blocked at the throat position of the diffusion channel formed by adjacent blades, and the pressure and efficiency drop sharply in the large flow area of ​​the compressor. In order to expand the application range of airfoil-shaped vane diffusers, research is conducted on the airfoil profile and layout form. The straight-wall diffuser is close to a straight line after the throat of the diffusion channel, and the airflow velocity and pressure distribution are relatively uniform. It is suitable for the high-energy head stage of centrifugal compressors, but has fewer applications. Summary of the Invention

[0004] In view of the defects or deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a composite blade and a new blade diffuser to solve the problems of large airflow impact loss and severe flow separation in the current blade diffuser, which leads to unstable working conditions.

[0005] To this end, the present invention adopts the following technical solutions:

[0006] A composite blade for a compressor blade diffuser, comprising a front blade and a rear blade smoothly transitioned to the front blade; the front blade is a half-height blade, and the rear blade is a full-height blade; the height ratio of the front blade to the rear blade is 0.3-0.7.

[0007] As a further improvement of the present invention, the ratio of the diameter of the connection between the front blade and the rear blade to the outlet diameter of the blade diffuser is 0.3-0.65.

[0008] As a further improvement of the present invention, the thickness of the head suction surface of the front blade is less than 1 / 2 of the thickness of the front blade, and the thickness of the head suction surface of the rear blade is less than 1 / 2 of the thickness of the rear blade.

[0009] As a further improvement of the present invention, the front blades and the rear blades are both airfoil-shaped blades.

[0010] As a further improvement of the present invention, the blades above the half-height position and the blades below the half-height position of the rear section blades adopt different wing shapes, and have a smooth transition at the half-height position.

[0011] As a further improvement of the present invention, the blade profile above the half-height position of the rear blade is flush with the blade profile wall below the half-height position or is consistent with the blade profile centerline below the half-height position.

[0012] The present invention also provides a compressor blade diffuser, comprising a diffuser body and composite blades evenly distributed along the circumference of the diffuser body, wherein the front blades and the rear blades of the composite blades smoothly transition at the throat position of the blade diffuser channel.

[0013] As a further improvement of the present invention, the number of blades of the composite blade is not greater than the number of impeller blades, and the difference between the number of blades and the number of impeller blades is an odd number. The half-height section of the front blade is located on the disk side or the shroud side of the compressor impeller.

[0014] As a further improvement of the present invention, the included angle between the front blade inlet geometric angle and the airflow is -3° to +5°.

[0015] As a further improvement of the present invention, the blade diffuser inlet Mach number is less than 0.85, the blade diffuser inlet width is not less than the impeller outlet width, the diffuser blade cascade density is 2-2.5, and the diffuser pressure reduction is 2-6.

[0016] The present invention has the following beneficial effects:

[0017] 1. The two-stage composite airfoil-blade diffuser proposed in the present invention will improve the flow loss at the diffuser inlet, reduce the airflow blockage at the diffuser inlet when the flow rate is large, and improve the performance and application range of the airfoil-blade diffuser.

[0018] 2. The two-stage composite airfoil-blade diffuser proposed in the present invention combines the advantages of a half-height wing diffuser and a full-height wing diffuser, increases the number of airfoil-blade diffusers arranged, and improves the flow conditions in the diffuser section.

[0019] 3. The two-stage composite airfoil-shaped blade diffuser proposed in the present invention further highlights its convenience and simplicity while ensuring practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the two-stage composite airfoil-shaped blade diffuser of the present invention.

[0021] In the figure, 1 is the front blade, 2 is the rear blade, 3 is the throat position, and 4 is the diffuser body. DETAILED DESCRIPTION

[0022] A half-height blade is equivalent to a diffuser blade whose height is partially cut, and the height of the blade is half the width of the diffuser channel. A full-height blade means that the height of the blade is usually equal to the width of the diffuser channel.

[0023] The throat area of ​​the blade is the minimum channel area between adjacent blades, and the position of this channel is the throat position.

[0024] The blade head is at the blade inlet edge, and its radius should usually be adapted to half the blade thickness in order to achieve a smooth transition.

[0025] Airfoil-shaped blades are one of the conventional surface choices for diffuser blade design. If the diffuser blade is airfoil-shaped, the center line of the airfoil-shaped blade is bent into the required shape, and a C-4 airfoil is often used.

[0026] The blade inlet and outlet geometric angles described in the present invention are the angles between the tangent direction of the blade bone line and the direction opposite to the direction of the circumferential speed of rotation.

[0027] The density of the blades is the density of the same blades arranged in a certain pattern.

[0028] The above descriptions and other parameters of the blade diffuser described below are all commonly understood in the art.

[0029] In addition, the "front section" and "rear section" mentioned in the present invention are defined relative to the flow direction of the fluid in the diffuser. The front section is from the air flow inlet to the throat position, and the "rear section" is after the throat position.

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Example 1:

[0032] like Figure 1 As shown, the present invention provides a blade diffuser, which is composed of two sections of airfoil-shaped composite blades, which are evenly distributed circumferentially in the flow channel of the diffuser body 4 to form a two-section composite airfoil-shaped blade diffuser.

[0033] Furthermore, the blade as a whole is a two-section aerofoil blade, a composite aerofoil blade in which the front section blade 1 is a half-height blade and the rear section blade 2 is a full-height blade. The front and rear sections are joined after the throat position 3 of the diffuser channel. The head of the rear half aerofoil blade adopts a brand-new aerofoil design, which solves the limitation that the number of blade airfoils is difficult to arrange reasonably, and has the advantages of high efficiency and low cost.

[0034] Furthermore, the half-height section of the blade head of the composite airfoil diffuser can be installed on the disk side or the shroud side of the compressor impeller.

[0035] Furthermore, the aerofoil-shaped blade head adopts a new optimized airfoil design method and smoothly transitions with the half-height blade wall.

[0036] Furthermore, in the two-stage composite airfoil blade diffuser, the diffuser inlet Mach number is less than 0.85, the diffuser inlet width b3 is not less than the impeller outlet width, the half-height blade diffuser inlet geometric angle and the airflow angle are -3 degrees to +5 degrees; the number of blades is not greater than the number of impeller blades, and there are an odd number of blades less than the impeller blades, the diffuser pressure degree is 2-6. The ratio of the half-height blade height to the full-height blade height is 0.3-0.7, D 32 / D4 is 0.3-0.65, which solves the problem of small high-efficiency flow range of existing airfoil-shaped blade diffusers.

[0037] The two-stage composite aerofoil diffuser structure combines the advantages of both vaned and vaneless diffusers. Half-height aerofoil blades are used in the front section of the diffuser, from the airflow inlet to the throat, while full-height blades are used behind the diffuser. Furthermore, the blades below and above the half-height position have different airfoil shapes, and the diffuser blade wall has a smooth transition. This technology increases the number of aerofoil blades, reduces airflow obstruction at the diffuser throat, and minimizes pressure loss in the high-flow area.

[0038] The blade as a whole is formed by a composite of two sections of airfoil-shaped blades, the front half of which is a half-height blade and the rear half of which is a full-height blade. The front and rear sections are connected after the throat of the diffuser channel, and the head of the airfoil-shaped blade is optimized to reduce airflow impact loss.

[0039] The number of blades is not greater than the number of impeller blades, and is an odd number less than the number of impeller blades. The diffuser pressure reduction is 2-6. The ratio of the half-height blade height to the full-height blade height is 0.3-0.7. The ratio of the blade airfoil junction diameter to the diffuser outlet diameter D32 / D4 is 0.3-0.65.

[0040] As a further improvement of the present invention, the thickness of the full-height blade diffuser in the rear half of the composite airfoil diffuser can be consistent with the profile of the lower blade, and various optimized deformation treatments are performed on the head.

[0041] As a further improvement of the present invention, the upper half profile of the rear half full-height blade diffuser of the composite airfoil diffuser can be flush with the wall surface of the lower blade profile, or can be consistent with the blade centerline, and various optimized deformation treatments are performed on the head.

[0042] As a further improvement of the present invention, the half-height blade airfoil and the full-height blade airfoil head should reduce the impact loss by reducing the thickness of the suction surface head.

[0043] Specific as Figure 1 As shown, the two-stage composite airfoil-shaped blade diffuser of the present invention can be arranged on the shroud side partition or the disk side partition. The blades are evenly distributed along the circumferential direction on the partition. The composite airfoil-shaped blades are two-dimensional blades. The airfoil of the half-height blade can be consistent with the airfoil of the full-height upper half, or it can be inconsistent. However, the transition between the blade profiles must be smooth. A diffusion channel is formed between two adjacent blades, and fluid can flow freely through it.

[0044] The design parameters of the two-stage composite airfoil blade diffuser of the present invention are designed according to certain rules. The design method is as follows: the geometric parameters that determine the shape of the two-stage composite airfoil blade diffuser include: diffuser inlet width b3, half-height blade diffuser height b 31 , diffuser outlet width b4, diffuser inlet diameter D3, half-height blade diffuser inlet diameter D 31 , full height section blade diffuser inlet diameter inlet diameter D 32 , full height diffuser outlet diameter D4, full height section blade diffuser height b 32 , half-height blade diffuser inlet geometric angle α 3A , blade outlet geometric angle α 4A , diffuser inlet geometric angle α of the upper half of the full-height blade 31A .

[0045] Among the above parameters, the present invention has made the following improvements in particular: the Mach number at the diffuser inlet is less than 0.85, the diffuser inlet width b3 is not less than the impeller outlet width, and the diffuser blade inlet installation angle is selected according to the impeller outlet airflow angle and the appropriate airflow angle; the diffuser inlet installation geometric angle of the half-height blade is -1 degree to +5 degrees with the airflow angle; the diffuser inlet geometric angle of the upper half of the full-height blade is less than 10 degrees with the airflow angle. The number of blades of the diffuser is 16-22, not more than the number of impeller blades, and an odd number of blades less than the impeller blades. The optimal density of the diffuser blade grid is 2-2.5. The ratio of the half-height height to the full height of the composite blade is 0.3 to 0.7, D 32 / D4 is 0.3-0.65; the diffuser inlet width should not be less than the impeller outlet width.

Claims

1. A compressor blade diffuser, comprising a diffuser body, characterized in that: The diffuser further comprises composite blades evenly distributed along the circumference of the diffuser body, the composite blades comprising a front blade section and a rear blade section smoothly transitioned to the front blade section; The front blade and the rear blade of the composite blade are smoothly transitioned at the throat of the blade diffuser channel; The front blades are half-height blades, and the rear blades are full-height blades; the ratio of the height of the front blades to the height of the rear blades is 0.3-0.7; The blade diffuser inlet Mach number is less than 0.85, the blade diffuser inlet width is not less than the impeller outlet width, the diffuser cascade density is 2-2.5, and the diffuser pressure reduction is 2-6; The ratio of the diameter of the connection between the front blade and the rear blade to the diameter of the blade diffuser outlet is 0.3-0.65; The front blade and the rear blade are both airfoil-shaped blades.

2. The compressor blade diffuser according to claim 1, wherein: The blade profile above the half-height position of the rear blade is flush with the blade profile wall below the half-height position or is consistent with the blade profile center line below the half-height position.

3. The compressor blade diffuser according to claim 1, wherein: The blades above the half-height position of the rear section blades and the blades below the half-height position adopt different wing shapes, and the blades transition smoothly at the half-height position.

4. The compressor blade diffuser according to claim 1, wherein: The number of the composite blades is not greater than the number of the impeller blades, and the difference between the number of the composite blades and the number of the impeller blades is an odd number. The half-height section of the front blade is located on the wheel disc side or the wheel cover side of the compressor impeller.

5. The compressor blade diffuser according to claim 1, wherein: The included angle between the front blade inlet geometry angle and the airflow is -3° to +5°.

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