One-dimensional inverse problem high-reliability aerodynamic design method for axial turbine

Abstract

The application provides a high-reliability one-dimensional inverse problem aerodynamic design method of an axial turbine, which is used for providing a better design method for the turbine in a one-dimensional inverse problem design link. The technical scheme is as follows: on the basis of the original, non-simplified processing is performed on core design parameters in turbine dimensionless parameters, such as inverse force degree, load coefficient, flow coefficient and the like, new inverse problem design calculation is performed on the processing, and a new inverse problem calculation process is reconstructed according to new definition formula.

Description

Technical Field

[0001] This invention relates to a highly reliable aerodynamic design method for a one-dimensional inverse problem of axial turbines, belonging to the field of turbine technology. Background Technology

[0002] The turbine is an essential core component of an engine, and its aerodynamic design is a step-by-step process of design and optimization from low to high dimensions. The results of the low-dimensional design serve as the initial values ​​and foundation for the high-dimensional design. Aerodynamic design can significantly affect the turbine design performance of the engine. Conventional turbine stage velocity triangle design is one of the important design methods, which evaluates the turbine's aerodynamic performance by using several key parameters of the velocity triangle and the turbine's aerodynamic performance parameters.

[0003] For existing one-dimensional axial turbine design techniques, simplified one-dimensional dimensionless design parameters are typically used to calculate turbine speed triangles for one-dimensional turbine design, and a simple efficiency formula is used to predict turbine one-dimensional performance.

[0004] The biggest problem with this method is that it oversimplifies the definition of dimensionless parameters, including:

[0005] The inlet and outlet circumferential velocities of the turbine blades are the same: U1 = U2

[0006] The axial velocities of the turbine blade inlet and outlet are the same: C 1a =C 2a

[0007] The turbine guide vane inlet velocity is the same as the moving blade outlet velocity: C0 = C2

[0008] According to the manual (Editorial Committee of "Aircraft Engine Design Manual", Huang Qingnan et al., Aircraft Engine Design Manual, Volume 10, Turbine [M]. Beijing: Aviation Industry Press, 2001.), the rim work is defined as follows:

[0009] L u =U(C 1u +C 2u )

[0010] Reaction force of movement:

[0011]

[0012] Flow coefficient:

[0013]

[0014] Efficiency formula:

[0015]

[0016] The advantage of this simplification is that it makes calculations easier for one-dimensional designs. However, the problem is obvious: when the design of a turbine does not meet this requirement, the design error is very large, making it difficult to meet the turbine design requirements of today's era. Summary of the Invention

[0017] The present invention aims to provide a highly reliable aerodynamic design method for one-dimensional inverse problems of axial turbines, which can provide a better design method for turbines in the one-dimensional inverse problem design stage.

[0018] The technical solution is as follows: Based on the existing foundation, the core design parameters such as reaction force, load coefficient, and flow coefficient in the dimensionless parameters of the turbine are processed in a non-simplified manner, and a brand-new inverse problem design calculation is performed on this processing. A new inverse problem calculation process is then reconstructed based on the new definition.

[0019] Specific technical solutions:

[0020] The following parameters are explained as follows:

[0021] L u Wheel of Fate Kung Fu Flow coefficient subscript 0 turbine inlet

[0022] C: Absolute speed; D2 inlet / outlet diameter ratio; subscript 1: turbine stage moving blade inlet.

[0023] U: Circumferential velocity μ, load coefficient, subscript 2, turbine stage blade outlet.

[0024] W: Relative velocity α, Absolute airflow angle, subscript a, axial component

[0025] η: Turbine stage efficiency β relative to airflow angle subscript u axial component

[0026] Ω counterforce P pressure superscript * total parameters

[0027] Energy counterforce Mach number

[0028] K a Axial speed ratio coefficient T temperature

[0029] G flow rate N rotation speed

[0030] R gas constant Guide vane velocity loss coefficient

[0031] ψ Blade velocity loss coefficient ε Work distribution coefficient

[0032] For inverse problem design calculations, the required total turbine parameters and dimensionless design parameters include:

[0033] Turbine total parameters: Turbine inlet total temperature Turbine inlet total pressure Flow rate G, gas constant R, rotational speed N, turbine inlet airflow angle α, inlet Mach number Ma, and rim work L u Efficiency η;

[0034] Dimensionless design parameters for turbine stage: load factor μ, flow factor Original counterforce / energy counterforce Ω and Axial speed ratio coefficient Ka, inlet and outlet mean diameter ratio D2.

[0035] First, the concept of "rimwork" is based on its original definition but modified:

[0036]

[0037] Then we can reconstruct an expression for the inverse force composed of a velocity triangle:

[0038] Original counterforce:

[0039] Energy counterforce:

[0040] Where the circumferential velocity is taken as the average of the inlet and outlet velocities, the new load factor formula is as follows:

[0041]

[0042] To ensure the reasonableness of the flow coefficient, the following formula is used for calculation.

[0043]

[0044] Processing the new formula, we get:

[0045] Original counterforce:

[0046] Energy counterforce:

[0047] Load factor:

[0048] in:

[0049]

[0050] By combining the expressions for the reaction force and the load coefficient, the parameters can be solved, and the efficiency of this stage can be expressed as follows:

[0051]

[0052] The specific steps for designing a one-dimensional inverse problem for an axial turbine are as follows:

[0053] (1) Obtain the conditions required for one-dimensional turbine design, including the total turbine parameters and the dimensionless design parameters of each turbine stage;

[0054] (2) Calculate the turbine isentropic work L based on the expansion ratio * ;

[0055] (3) Initialize actual power:

[0056] L=ηL ad

[0057] Here, a default value is given as the initial efficiency parameter; it is generally 0.9.

[0058] (4) Obtain the initial flange work L for each stage based on the work distribution coefficient. u :

[0059] L u =εL

[0060] (5) Calculate the turbine inlet parameters to obtain the total static pressure and absolute inlet velocity of the turbine inlet section;

[0061] (6) Preprocess the data to obtain the velocity triangle of the moving blade;

[0062] (7) Calculate the parameters of each section of the turbine according to the known conditions;

[0063] (8) Calculate the new actual work L′ based on the calculated total outlet temperature;

[0064] (9) Compare L and L′. If they are the same, the design is complete. If they are different, let L = L′ and recalculate from step (3) until the iteration is satisfied.

[0065] The specific technical effects of this invention are as follows: The new dimensionless definition method and design method have higher reliability for the one-dimensional inverse problem aerodynamic design of axial turbines compared with the original design method, and are beneficial to the low-dimensional design of turbines in actual design. Attached Figure Description

[0066] Figure 1 This is a flowchart of the present invention;

[0067] Figure 2a This is a comparison chart of the efficiency levels of our method and the enthalpy difference method;

[0068] Figure 2b This is a comparison chart of the absolute error of efficiency between our method and the enthalpy difference method. Detailed Implementation

[0069] The technical solution process of this invention is as follows: Figure 1As shown, to verify the improved reliability of this invention, three different types of turbine channels were designed using a one-dimensional inverse problem design method: two two-stage axial flow turbines and one three-stage axial flow turbine. The two two-stage axial flow turbines were designed with equal mean diameter and equal inner diameter, respectively, while the three-stage axial flow turbine was designed with equal mean diameter. The stage efficiency of each turbine was compared using this method and the enthalpy difference method, as shown in the comparison... Figure 2a and Figure 2b As shown, the efficiency error between the approximate method and the actual enthalpy difference calculation method is only about 0.2%, which is negligible when used for one-dimensional design evaluation of turbine performance.

Claims

1. A high-reliability aerodynamic design method for a one-dimensional inverse problem of axial turbines, characterized in that, The core design parameters in the dimensionless parameters of the turbine are processed in a non-simplified manner, and a new inverse problem design calculation is performed on this processing. A new inverse problem calculation process is reconstructed based on the new definition. The specific steps for designing a one-dimensional inverse problem for an axial turbine are as follows: (1) Obtain the conditions required for one-dimensional turbine design, including the total turbine parameters and the dimensionless design parameters of each turbine stage; (2) Calculate the isentropic work of the turbine based on the expansion ratio. ; (3) Initialize actual work: ， in, Default values ​​are given as initial parameters for efficiency; (4) Obtain the initial rim work of each stage based on the work distribution coefficient. : ， ε is the work distribution coefficient; (5) Calculate the turbine inlet parameters to obtain the total static pressure and absolute inlet velocity at the turbine inlet section; (6) Preprocess the data to obtain the velocity triangle of the moving blade; First, the concept of "rimwork" is based on its original definition but modified: ， For rim work; U is circumferential velocity, W is relative velocity, C is absolute velocity, subscript 1 is turbine stage blade inlet, subscript 2 is turbine stage blade outlet, subscript u is circumferential component; Then, a new expression for the inverse force, composed of a velocity triangle, is constructed: ， Ω represents the counterforce. For energy counterforce, The velocity loss coefficient of the moving blade. The guide vane velocity loss coefficient is given by P, where P is the pressure; subscript 0 is the turbine inlet, subscript 1 is the turbine stage blade inlet, subscript 2 is the turbine stage blade outlet, subscript u is the circumferential component, and superscript * is the total parameter. The circumferential velocity is taken as the average of the inlet and outlet velocities. The new load factor formula is as follows. ， μ is the load factor; To ensure the reasonableness of the flow coefficient, the following formula is used for calculation. ， Flow coefficient, C is the absolute velocity, subscript 1 is the turbine stage blade inlet, subscript 2 is the turbine stage blade outlet, and subscript a is the axial component; The new formula is processed to obtain... Original counterforce: , Energy counterforce: , Load factor: , in: , K a D1 is the axial speed ratio coefficient, and D2 is the inlet / outlet pitch diameter ratio. By combining the expressions for the reaction force and the load coefficient, the parameters can be solved. Therefore, the efficiency of this stage can be expressed as follows: ， For turbine-level efficiency; (7) Calculate the parameters of each section of the turbine according to the known conditions; (8) Calculate the new actual work based on the calculated total outlet temperature; (9) Comparison and If they are the same, the design is complete; if they are different, then... Recalculate from step (3) until the iteration is satisfied.

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