General design method suitable for centrifugal compressor model stages with different flow coefficients

Abstract

The invention discloses a universal design method suitable for centrifugal compressor model stages with different flow coefficients, and belongs to the technical field of centrifugal compressor design. The method mainly relates to establishment of three-dimensional models of an impeller, a vaneless diffuser, a curve and a backflow device and comprises a rotor part and a stator part, and design parameters of the centrifugal compressor model stage are finally obtained according to a series of calculation results and given parameters. The method is a universal method suitable for centrifugal compressor model stages with different flow coefficients, and the design efficiency and the aerodynamic performance of the compressor are improved. According to the method, the structure compactness of the model stage is ensured, the performance is more potential, and the thermodynamic cycle efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of design of working components of centrifugal rotating machinery, and in particular to a universal design method for centrifugal compressor model stages suitable for different flow coefficients. Background Art

[0002] Centrifugal compressors are widely used in high-energy-consuming industries such as thermal power, steel, non-metallic mineral products, oil refining and coking, chemicals, non-ferrous metals, etc., and are important equipment in high-energy-consuming industries. As the working component of the centrifugal compressor, the design level of the centrifugal impeller directly affects the performance of the compressor unit. From the existing public data, as the compression ratio of the compressor increases, the efficiency and operating range of the compressor generally show a downward trend, but under a certain pressure ratio, due to different design methods, the performance of the designed compressor will also vary greatly. Therefore, building a reliable design method is of great significance to the design of high-performance compressors. At present, researchers generally take the minimum relative Mach number of the impeller inlet tip as one of the design principles. The compressor designed in accordance with the above principles is more compact in structure, but it also greatly reduces the selection range of the relative airflow angle of the impeller inlet tip. In the case of no pre-swirling air intake at the inlet, when the relative airflow angle of the impeller inlet tip is less than 55°, the corresponding Mach number of the impeller inlet tip has no practical significance. This makes the above method no longer applicable when faced with a selection range less than 55°. Secondly, among the design methods of centrifugal impellers, the whole stage matching problem is less considered. One situation is that when considering the whole stage structural size, the radial height of the diffuser must be limited. At this time, it is hoped that the outlet airflow angle of the rotor component is larger, thereby reducing the diffuser height. However, if the whole stage performance is considered, it is hoped that the outlet airflow angle of the rotor component is smaller, so that when matching the return flow component, the installation angle of the guide vane in the return flow device will not be too large, causing the airflow to separate and causing the whole stage performance to decrease. Therefore, the impeller design has a greater impact on the whole stage matching. Summary of the invention

[0003] The purpose of the present invention is to provide a universal modeling method for centrifugal compressor models with different flow coefficients to improve the design efficiency and the aerodynamic performance of the compressor in view of the shortcomings of the existing design methods.

[0004] The technical solution adopted to achieve the purpose of the present invention is: a general modeling method for centrifugal compressor model stages applicable to different flow coefficients, comprising the following steps:

[0005] (1) Given impeller design target parameters, impeller geometric constraint parameters and gas physical property parameters; the given impeller design target parameters include the inlet total temperature T t1 , total inlet pressure P t1 , isentropic efficiency , total pressure ratio and flow coefficient The given impeller geometric constraint parameters include the centrifugal impeller outlet diameter D2, the centrifugal impeller hub diameter D 1h , Centrifugal impeller outlet installation angle Number of blades , specific enthalpy ratio ; The given gas physical parameters include the gas constant and adiabatic index ;

[0006] (2) Set the angle of the centrifugal impeller inlet blade tip relative to the airflow and offset angle :

[0007] (3) Calculate the relative Mach number at the centrifugal impeller inlet tip , the calculation formula is:

[0008]

[0009] (4) Calculate the enthalpy rise coefficient , determine whether the enthalpy rise coefficient is less than 1. If it is not satisfied, return to step (2) and reset the inlet blade tip relative airflow angle and offset angle The calculation formula is:

[0010]

[0011] (5) Calculation of the export engine Mach number , ;

[0012] Among them, u2 is the impeller outlet circumferential speed, a tl is the inlet stagnation speed of sound.

[0013] (6) Calculate the outlet circumferential speed ratio , .

[0014] (7) Calculate the outlet radial velocity ratio , .

[0015] Determine whether the outlet radial velocity ratio is between If the range is not satisfied, return to step (2) and reset the inlet blade tip relative airflow angle and offset angle .

[0016] (8) Calculate the absolute airflow angle at the impeller outlet , , determine the absolute outlet airflow angle Is the calculated result greater than 60°? If less than 60°, return to step (2) and reset the inlet blade tip relative airflow angle. and offset angle .

[0017] (9) Calculate the centrifugal impeller inlet tip diameter Centrifugal impeller outlet diameter Ratio , the calculation formula is:

[0018]

[0019] (10) Calculate the centrifugal impeller outlet width Centrifugal impeller outlet diameter Ratio , the calculation formula is:

[0020]

[0021] (11) Calculate the axial length of the centrifugal impeller and L and the centrifugal impeller outlet diameter Ratio , the calculation formula is:

[0022] ,in, .

[0023] (12) Calculate the dimensioned geometric dimensions of the impeller inlet and outlet , and L.

[0024] (13) Combined with the ideal state equation of gas, , calculate the total import density, and then calculate the import density , the calculation formula is:

[0025]

[0026] (14) Calculate the relative axial airflow angle of the centrifugal impeller inlet hub using the following formula:

[0027]

[0028] (15) Calculate the diffusion degree DF, , determine whether the calculated result of the diffusion pressure is within the range of 0.6~0.8. If it exceeds the set range, return to step (2) and reset the relative airflow angle of the inlet blade tip. and offset angle ,

[0029] (16) According to the definition of flow coefficient, calculate the mass flow rate ,have to .

[0030] (17) Based on the one-dimensional design parameters of (1)-(16), a three-dimensional model of the rotor components was established in the NREC software.

[0031] (18) Adjust the meridian flow channel profile and blade profile, and analyze the load distribution in the blade-to-blade (B2B) direction , according to the definition , qualitative analysis ,control , The value makes the load factor satisfy that the maximum load area is located in the 50~60% part of the chord length, the load coefficients of the leading edge and trailing edge of the blade are small, and the maximum load factor does not exceed 0.7~0.8.

[0032] (19) Given the vaneless diffuser transition section height .

[0033] (20) Given the vaneless diffuser outlet width .

[0034] (21) Given the equivalent expansion angle of a bladeless diffuser ,according to calculate Get the vaneless diffuser diameter .

[0035] (22) Calculate the curve radius using the following formula:

[0036]

[0037] (23) The return flow device includes two-dimensional guide vanes. The guide vane leading edge installation angle is calculated as follows: is the installation angle of the leading edge of the return flow device blade, °; , are the inner and outer radius of the curve, m; is the diameter at the exit of the curve, m; is the tangential velocity component at the curve exit, m / s; is the volume flow rate at the bend outlet, m3 / s. The value is taken approximately from the volume flow rate at the bend inlet. The formula is:

[0038]

[0039] (24) The installation angle of the trailing edge of the return flow device blade is given as 0°.

[0040] (25) Design a three-dimensional model of the stator component based on the NREC platform and the one-dimensional design parameters (16)-(23).

[0041] The beneficial effects of the present invention are as follows: 1) Rotor part: given impeller design target parameters, impeller geometric constraint parameters and gas physical property parameters; given centrifugal impeller inlet blade tip relative airflow angle and offset angle; calculated centrifugal impeller inlet blade tip relative Mach number; calculated enthalpy rise coefficient, and judged whether it meets the design requirements; calculated outlet machine Mach number; calculated outlet circumferential velocity ratio; calculated outlet radial velocity ratio, and judged whether it meets the design requirements; calculated the ratio of centrifugal impeller outlet blade tip diameter to centrifugal impeller outlet diameter; calculated the ratio of centrifugal impeller outlet width to outlet diameter; given centrifugal impeller outlet diameter and calculated impeller axial length; calculated outlet circumferential velocity and judged whether it meets the design requirements; calculated diffusion pressure and judged whether it meets the design requirements; calculated impeller outlet static temperature; calculated impeller outlet absolute airflow angle and judged whether it meets the design requirements; calculated impeller outlet absolute Mach number and judged whether it meets the design requirements; calculated impeller inlet density; calculated flow coefficient and judged whether it meets the design requirements; implemented structure and load coupling calculation, adjusted the meridian flow channel profile and blade profile, and output rotor model.

[0042] 2) Stator part: calculate the transition section height of the bladeless diffuser; calculate the outlet width of the bladeless diffuser; calculate the diameter of the bladeless diffuser; calculate the curve profile; calculate the leading edge installation angle of the return flow two-element guide vane; give the trailing edge installation angle of the return flow two-element blade; output the stator part model.

[0043] The impeller designed by the method of the present invention guarantees the compactness of the structure to the maximum extent, and also widens the selection range of the relative airflow angle of the impeller inlet blade tip. At the same time, under the same relative airflow angle of the impeller inlet blade tip, a lower relative Mach number of the inlet blade tip is corresponding, which makes the airflow loss smaller and the designed model has more potential in performance. The design method can greatly shorten the design cycle and increase the probability of successful design. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a flow chart of the method.

[0045] Figure 2 It is a schematic diagram of some relevant parameters of impeller design.

[0046] Figure 3 It is a schematic diagram of parameters related to the impeller meridian flow channel and profile adjustment.

[0047] Figure 4 It is a schematic diagram of some relevant parameters of diffuser design.

[0048] Figure 5 It is a schematic diagram of some relevant parameters of curve design.

[0049] Figure 6 This is the meridian flow channel of the embodiment model.

[0050] Figure 7 1 is a side view of an embodiment model.

[0051] Figure 8 It is an axial view of the impeller of the embodiment model.

[0052] Fig. 9 is an axial view of the return flow device of the embodiment model.

[0053] Fig.10 is the efficiency curve of the embodiment model.

[0054] Fig.11 is the static pressure ratio curve of the embodiment model. DETAILED DESCRIPTION

[0055] Example: The design process of a centrifugal impeller with subsonic axial air intake in an industry is as follows:

[0056] (1) Given the centrifugal impeller design objectives: including the inlet total temperature T t1 =303K, total inlet pressure P t1 =101000Pa, isentropic efficiency , total pressure ratio , flow coefficient , speed n = 11600rpm; given centrifugal impeller geometric constraints: including centrifugal impeller outlet diameter D2 = 0.5m, centrifugal impeller hub diameter D 1h =0.2m, centrifugal impeller outlet installation angle , number of blades , specific enthalpy ratio ; Given medium characteristic parameters: including gas constant , adiabatic index ;

[0057] (2) Set the initial centrifugal impeller inlet tip relative airflow angle and offset angle ;

[0058] (3) Calculate the relative Mach number of the centrifugal impeller inlet cover. The result is: ;

[0059] (4) Calculate the enthalpy rise coefficient, and the iterative result is , it is judged that the enthalpy rise coefficient result is less than 1 and meets the set range;

[0060] (5) Calculate the machine Mach number and the result is ;

[0061] (6) Calculate the outlet circumferential velocity ratio, and the result is ;

[0062] (7) Calculate the outlet radial velocity ratio, and the result is: , determine the outlet radial velocity ratio between Range, meet the set range.

[0063] (8) Calculate the absolute airflow angle at the impeller outlet and the result is: ;

[0064] (9) Calculate the centrifugal impeller inlet tip diameter Centrifugal impeller outlet diameter Ratio ,turn out .

[0065] (10) Calculate the centrifugal impeller outlet width Centrifugal impeller outlet diameter Ratio: ,turn out .

[0066] (11) Calculate the axial length of the centrifugal impeller and L and the centrifugal impeller outlet diameter Ratio: ,turn out .

[0067] (12) Calculate the centrifugal impeller inlet cover diameter ,turn out ; Calculate the centrifugal impeller outlet width , ; Calculate the axial length of the centrifugal impeller ,turn out ;

[0068] (13) Calculate the inlet density ,turn out ;

[0069] (14) Calculate the relative axial flow angle of the centrifugal impeller inlet hub ,turn out .

[0070] (15) Calculation of diffusion degree ,turn out , satisfying the set range. .

[0071] (16) Calculate the design mass flow rate ,turn out , meeting the set range.

[0072] (17) Centrifugal impeller modeling based on the NREC platform.

[0073] (18) In the NREC platform, the meridian flow path profile and blade profile are adjusted so that the load factor satisfies the maximum load area located at 50% to 60% of the chord length, the load factors at the leading and trailing edges of the blades are small, and the maximum load factor does not exceed 0.7.

[0074] (19) Calculate the transition section height of the bladeless diffuser ,turn out .

[0075] (20) Calculate the outlet width of the vaneless diffuser ,turn out .

[0076] (21) Given the equivalent expansion angle of a bladeless diffuser ,turn out .

[0077] (22) Calculate the outlet diameter of the vaneless diffuser ,turn out .

[0078] (23) Calculate the curve radius (R, ), the result is R=0.0251m, .

[0079] (24) Calculate the leading edge installation angle of the return guide vane ,turn out =64.5082~65.5082°.

[0080] (25) The trailing edge installation angle of the return flow guide vane is given to be 0°.

[0081] (26) Based on the NREC platform, three-dimensional modeling of the stator is performed.

[0082] So far, the aerodynamic and geometric parameters required for the design of the centrifugal compressor have been calculated, and the model-level geometric model has been given.

[0083] The impeller designed by the method of the present invention ensures the compactness of the structure to the maximum extent, and also widens the selection range of the impeller inlet blade tip relative airflow angle. At the same time, under the same impeller inlet blade tip relative airflow angle, a lower inlet blade tip relative Mach number corresponds, which makes the airflow loss smaller and the designed model has more potential in performance.

[0084] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0085] The above contents are further detailed descriptions of the present invention in combination with specific preferred technical solutions, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A general design method for centrifugal compressor model stages suitable for different flow coefficients, characterized in that: The steps include: (1) Given impeller design target parameters, impeller geometric constraint parameters and gas physical property parameters; the impeller design target parameters include the inlet total temperature T t1 , total inlet pressure P t1 , isentropic efficiency , total pressure ratio and flow coefficient The impeller geometric constraint parameters include the centrifugal impeller outlet diameter D2, the centrifugal impeller hub diameter D 1h , Centrifugal impeller outlet installation angle Number of blades , specific enthalpy ratio ; The gas physical parameters include the gas constant and adiabatic index ; (2) Setting the relative airflow angle of the centrifugal impeller inlet tip and offset angle ; (3) Calculate the relative Mach number at the centrifugal impeller inlet tip , the calculation formula is as follows: ； (4) Calculation of enthalpy rise coefficient , the calculation formula is as follows: ； Determine whether the enthalpy rise coefficient is less than 1. If not, return to step (2) and reset the relative airflow angle of the inlet blade tip. and offset angle ; (5) Calculation of the machine Mach number : ； Among them, u2 is the impeller outlet circumferential speed, a tl is the inlet stagnation sound velocity; (6) Calculate the outlet circumferential speed ratio : ； (7) Calculate the outlet radial velocity ratio : ； Determine whether the outlet radial velocity ratio is between If the range is not satisfied, return to step (2) and reset the inlet blade tip relative airflow angle and offset angle ; (8) Calculate the absolute airflow angle at the impeller outlet : ； Determine the absolute outlet airflow angle Is the calculated result greater than 60°? If less than 60°, return to step (2) and reset the inlet blade tip relative airflow angle. and offset angle ; (9) Calculate the centrifugal impeller inlet tip diameter Centrifugal impeller outlet diameter Ratio , the calculation formula is: ； (10) Calculate the centrifugal impeller outlet width Centrifugal impeller outlet diameter Ratio , the calculation formula is: (11) Calculate the axial length of the centrifugal impeller, L, and the outlet diameter of the centrifugal impeller Ratio , the calculation formula is: ； in, ; (12) Calculate the dimensioned geometric dimensions of the impeller inlet and outlet , and L; (13) Combined with the ideal state equation of gas, , calculate the total import density, and then calculate the import density , the calculation formula is: ； (14) Calculate the relative axial airflow angle of the centrifugal impeller inlet hub , the calculation formula is: ； (15) Determine whether the calculated diffusion pressure is within the range of 0.6 to 0.

8. If it exceeds the set range, return to step (2) and reset the inlet blade tip relative airflow angle. and offset angle ; The formula for calculating the diffusion degree is as follows: ； (16) According to the definition of flow coefficient, calculate the mass flow rate , ; (17) Based on the one-dimensional design parameters of steps (1) to (16), a three-dimensional model of the rotor component is established in the NREC software; (18) Adjust the meridian flow channel profile and blade profile, and analyze the load distribution in the blade-to-blade B2B direction , ; Qualitative analysis ,control , The value makes the load factor satisfy the maximum load area located at 50-60% of the chord length, and the maximum load factor does not exceed 0.7-0.8; (19) Given the vaneless diffuser transition section height ; (20) Given the vaneless diffuser outlet width ; (21) Given the equivalent expansion angle of a bladeless diffuser ; according to calculate , and the vaneless diffuser diameter is obtained ; (22) Calculate the curve radius using the following formula: ； (23) The return flow device includes a two-dimensional guide vane. Calculate the installation angle of the guide vane leading edge. ； In the formula, Install angle for leading edge of return flow device blade; , are the inner and outer radii of the curve respectively; is the diameter at the exit of the curve; is the tangential velocity component at the curve exit; is the volume flow rate at the bend exit; (24) The installation angle of the trailing edge of the return flow device blade is given to be 0°; (25) Based on the one-dimensional design parameters in steps (16) to (23), a three-dimensional model of the stator component is established in the NREC software; Finally, the design parameters of the centrifugal compressor model stage are obtained according to the calculation results of the above steps and the given parameters.

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