A method of aerodynamic design of a variable geometry two-stage low pressure turbine

Abstract

The application belongs to the field of aero-engine design, and particularly relates to a variable-geometry two-stage low-pressure turbine aerodynamic design method, a flow maximum and a flow minimum typical state point are respectively selected to perform through-flow design and turbine one-dimensional aerodynamic design, and one-dimensional design results are obtained; turbine base element blade profiles are determined according to the one-dimensional design results, and three-dimensional modeling is respectively performed to establish adjustable blade configurations of each stage of turbine; three-dimensional models of each stage of turbine are established and run, turbine working parameters of each stage of turbine at the flow maximum and flow minimum typical state points are collected, turbine characteristic calculation of the turbine under different rotating speeds with changes in expansion ratio is performed, and turbine working parameters of each stage of turbine are obtained. The efficiency of the turbine is improved under limited geometric dimensions, compared with a single-stage variable-geometry turbine, the turbine efficiency at the flow minimum typical state point is improved by 3-4%, wide flow regulation range and high-efficiency variable-geometry low-pressure turbine design are achieved, and the overall performance of the engine is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of aero-engine design, and particularly relates to a variable-geometry two-stage low-pressure turbine aerodynamic design method. BACKGROUND

[0002] The variable-geometry low-pressure turbine adjusts the engine bypass ratio by changing the turbine guide vane area, realizes the optimization of engine thrust and specific fuel consumption, and realizes higher working efficiency in a limited size range for the same turbine working state, thereby realizing lower specific fuel consumption of the engine.

[0003] The existing technology has the following disadvantages: the current variable-geometry low-pressure turbine design is one-dimensional aerodynamic design, and the full three-dimensional design method is not designed. Meanwhile, the design method of the expansion ratio distribution of the two-stage variable-geometry low-pressure turbine is not given, and the influence of the guide vane gap change of the variable-geometry turbine at different states on the turbine performance is not checked and evaluated.

[0004] Therefore, how to realize the design of the two-stage variable-geometry low-pressure turbine is a problem to be solved. SUMMARY

[0005] In order to solve the above problems, the application provides a variable-geometry two-stage low-pressure turbine aerodynamic design method to solve the problem that the two-stage variable-geometry low-pressure turbine design is not realized in the prior art.

[0006] The technical scheme of the application is: a variable-geometry two-stage low-pressure turbine aerodynamic design method, comprising:

[0007] determining turbine working parameters of a typical state point of the engine one-stage guide vane variable-geometry low-pressure turbine;

[0008] selecting a typical state point with maximum flow and a typical state point with minimum flow respectively, performing through-flow design based on the turbine working parameters of the typical state point with maximum flow, performing one-dimensional aerodynamic design of the turbine based on the turbine working parameters of the typical state point with minimum flow, and obtaining one-dimensional design results;

[0009] determining a turbine base element blade profile according to the one-dimensional design results, and establishing a variable blade configuration of each stage turbine through three-dimensional modeling, including a variable guide vane configuration of each stage turbine and a rotor blade configuration;

[0010] collecting performance parameters of the typical state point with maximum flow and the typical state point with minimum flow based on the variable blade configuration of each stage turbine, performing quasi-three-dimensional calculation, and judging whether the first design requirement is met, if yes, the next step is executed;

[0011] Based on the trend of the turbine adjustable guide vane gap with the guide vane adjustment angle, three-dimensional models of the turbine are established; the turbine working parameters of the three-dimensional models of the turbine are collected at the typical state points of the maximum flow and the minimum flow, and whether the second design requirement is met is judged, if yes, the next step is executed;

[0012] The turbine characteristics calculation of the turbine at different turbine guide vane adjustment angles with the expansion ratio is carried out at different rotating speeds, the turbine working parameters of the turbine are obtained, and whether the third design requirement is met is judged after the full state calculation, if yes, the aerodynamic design is completed.

[0013] Preferably, when the turbine one-dimensional aerodynamic design is carried out, the turbine power distribution is determined by the given low-pressure turbine expansion ratio, the load coefficient of the low-pressure turbine is obtained, and the flow coefficient of the turbine is determined according to the iteration of the reaction degree of the turbine, and the one-dimensional design result is obtained.

[0014] Preferably, when the turbine power distribution is determined by the given low-pressure turbine expansion ratio, the total pressure of the first stage turbine inlet of the turbine at the typical state point of the minimum flow is defined as , the outlet pressure of the first stage turbine is , the outlet pressure of the second stage turbine is , the total turbine expansion ratio is defined as , the formula is = ; wherein the first stage turbine expansion ratio is = , the value is ; the second stage turbine expansion ratio is = , the value is ;

[0015] The total pressure of the first stage turbine inlet of the turbine at the typical state point of the maximum flow is defined as , the outlet pressure of the first stage turbine is , the outlet pressure of the second stage turbine is , the total turbine expansion ratio is defined as , the formula is = , wherein the first stage turbine expansion ratio is = , the second stage turbine expansion ratio is = , by increasing the first stage turbine guide vane area, the turbine works at the typical state point is 0.952 , is 1.05 .

[0016] Preferably, the specific method of quasi-three-dimensional calculation is as follows:

[0017] The turbine blades at each stage are divided into a plurality of element stages along the radial direction, each element stage corresponding to a radial position, the inlet and outlet velocities of each element stage are calculated according to the one-dimensional design result, the flow loss of each element stage is estimated in combination with a semi-empirical loss model, the turbine efficiency, expansion ratio and flow rate are calculated based on the flow loss of each element stage, and the corresponding parameters of the first design requirement are compared to determine whether the first design requirement is met.

[0018] Preferably, the position of the rotating shaft is determined according to the configuration of the turbine adjustable guide vane, and then the change range and change of the turbine adjustable guide vane gap with the change of the angle of the turbine guide vane adjustment are estimated.

[0019] The first stage turbine guide vane angle of the typical state point with the minimum flow rate is defined as 0°, and the three-dimensional model of each stage of the turbine is established according to the change range and change of the turbine adjustable guide vane gap with the change of the angle of the turbine guide vane adjustment.

[0020] Preferably, the turbine working parameters of the typical state point of the low-pressure turbine include turbine rotating speed, flow rate, expansion ratio, inlet aerodynamic parameter, outer expansion size limit and turbine efficiency.

[0021] The aerodynamic design method of the variable geometry two-stage low-pressure turbine of the present application has the following advantages:

[0022] The efficiency of the turbine is improved under limited geometric size, and the efficiency of the turbine at the typical state point with the minimum flow rate is improved by 3-4% compared with the single-stage variable geometry turbine, realizing the design of the variable geometry low-pressure turbine with wide flow rate adjustment range and high efficiency, greatly improving the matching cycle benefit of the engine and the overall performance of the engine.

[0023] The equal distribution variable geometry two-stage low-pressure turbine stage expansion ratio distribution method can effectively ensure that the variable geometry two-stage turbine works in the high efficiency region at two typical state points (flow rate adjustable boundary points).

[0024] The influence of the guide vane gap loss at different positions under different states can be effectively identified, and the problem of insufficient variable geometry turbine efficiency margin caused by insufficient consideration of the turbine guide vane gap during design can be effectively avoided. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is a schematic diagram of the overall process of the present application;

[0026] Figure 2 The figure is a schematic diagram of the position selection of the rotating shaft at the root section and the tip section and the gap position of the guide vane;

[0027] Figure 3This shows how the clearances of the guide vanes in this application change with the rotation angle of the turbine's adjustable guide vanes. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0029] The first aspect of this application provides a variable geometry two-stage low-pressure turbine aerodynamic design method, such as... Figure 1 As shown, it includes the following steps:

[0030] Step S100, Turbine operating parameters at typical engine operating points:

[0031] Determine the turbine operating parameters for typical state points of the low-pressure turbine with variable geometry of the engine's first-stage guide vanes, including but not limited to turbine speed, flow rate, expansion ratio, inlet aerodynamic parameters, external expansion size limitations, and turbine efficiency.

[0032] Step S200: Complete the flow path design based on the variable geometry profile requirements of the first-stage guide vane.

[0033] Select the turbine operating parameters at the typical state point of maximum flow rate for flow path design.

[0034] Specifically, flow design can be carried out by combining equal density flow design with three-dimensional CFD simulation.

[0035] Step S300: Turbine stage expansion ratio, reaction force iteration, and one-dimensional turbine aerodynamic design:

[0036] By selecting the turbine operating parameters at the typical state point with the minimum flow rate, a one-dimensional aerodynamic design of the turbine is performed, yielding the one-dimensional design results. These results include parameters such as the number of blades in each stage, stage power, flow coefficient, and load coefficient.

[0037] When performing one-dimensional aerodynamic design of a turbine, the turbine power distribution is determined by giving the expansion ratio of each stage of the low-pressure turbine, and the load coefficient of each stage of the low-pressure turbine is obtained. At the same time, the flow coefficient of each stage of the turbine is determined by iterative method of the reaction force of each stage of the turbine, and the one-dimensional design result is obtained, ensuring that each stage of the turbine operates in the high-efficiency region.

[0038] In the embodiment, the turbine expansion ratio of each stage of the variable-geometry two-stage low-pressure turbine is allocated in the equal distribution of the total expansion ratio when the typical state point of minimum flow is designed.

[0039] Specifically,

[0040] First, the total pressure of the turbine first stage inlet of the typical state point of minimum flow is defined as , the first stage turbine outlet pressure is , the second stage turbine outlet pressure is , the total turbine expansion ratio is defined as , and the formula is = ; wherein the first stage turbine expansion ratio is = , and the value is ; the second stage turbine expansion ratio is = , and the value is ;

[0041] Then, the total pressure of the turbine first stage inlet of the typical state point of maximum flow is defined as , the first stage turbine outlet pressure is , the second stage turbine outlet pressure is , the total turbine expansion ratio is defined as , and the formula is = , wherein the first stage turbine expansion ratio is = , the second stage turbine expansion ratio is = , by increasing the first stage turbine guide vane area, the turbine works at the typical state point is 0.952 , is 1.05 .

[0042] The expansion ratio of each stage in the case is a compromise selected value based on the first stage turbine load of two typical working points and the adjustable flow range of the turbine first stage guide vane, which can maintain the high efficient work of the turbine at the two typical state points.

[0043] Step S400, turbine blade profile design:

[0044] According to the one-dimensional design result, the turbine element blade profile is determined, and the adjustable blade configuration of each stage of turbine is established through three-dimensional modeling, including the adjustable guide vane configuration and the rotor blade configuration of each stage of turbine.

[0045] Step S500, quasi-three-dimensional calculation check:

[0046] Based on the adjustable blade configuration of each stage of turbine, the performance parameters of the typical state points of maximum flow and minimum flow are collected, and quasi-three-dimensional calculation is performed to determine whether the first design requirement is met. If yes, the next step is performed; if not, steps S300 and S400 are repeated until the first design requirement is met.

[0047] Preferably, the specific method of quasi-three-dimensional calculation is as follows:

[0048] Each stage of turbine blade is divided into multiple element stages along the radial direction, each element stage corresponding to a radial position. The inlet and outlet velocities of each element stage are calculated according to the one-dimensional design results, and the flow loss of the element stage is estimated by combining a semi-empirical loss model. The turbine efficiency, expansion ratio and flow are calculated based on the flow loss of each element stage, and compared with the corresponding parameters of the first design requirement to determine whether the first design requirement is met.

[0049] Step S600, estimate the trend of turbine adjustable guide vane gap with guide vane adjustment angle;

[0050] According to the turbine adjustable guide vane configuration, the position of the rotating shaft is determined, and then the range of the turbine guide vane adjustment angle is determined according to the turbine guide vane adjustment angle determined in step S500. The trend of the turbine adjustable guide vane gap with the turbine guide vane adjustment angle is estimated, including the range of the angle change and the change situation.

[0051] Figure 2 The position selection of the rotating shaft at the root section and the tip section and the gap position diagram of each part of the guide vane are given, wherein A1 is the guide vane tip close to the leading edge gap, A2 is the guide vane tip close to the trailing edge gap, B1 is the guide vane root close to the leading edge gap, and B2 is the guide vane root close to the trailing edge gap.

[0052] Step S700, three-dimensional calculation check:

[0053] A three-dimensional model of each stage of turbine is established; the turbine working parameters of each stage of turbine at the typical state points of maximum flow and minimum flow are collected by running the three-dimensional model of each stage of turbine, and it is determined whether the second design requirement is met. If yes, the next step is performed; if not, steps S400-S600 are repeated.

[0054] Preferably, the first stage turbine guide vane angle of the typical state point of minimum flow is defined as 0°, and the range of the turbine adjustable guide vane gap with the turbine guide vane adjustment angle and the change situation are as follows: Figure 3 A three-dimensional model of each stage of turbine is established.

[0055] Step S800, turbine characteristic calculation:

[0056] Turbine characteristic calculation is carried out at different turbine guide vane adjustment angles under different turbine speeds with different expansion ratios to obtain the turbine working parameters of each stage of turbine.

[0057] Specifically, parametric simulations can be performed to obtain turbine flow-expansion ratio characteristics and efficiency-expansion ratio characteristics under different wheel guide angles, turbine speeds, and expansion ratios, and output concise characteristic curves / tables to obtain turbine operating parameters for each stage of the turbine.

[0058] If needed, we can provide overall professional services for engine matching and optimization design.

[0059] Step S900: Perform full-state calculation of turbine operating parameters. After performing the full-state calculation (if the overall parameters are updated to optimize the design parameters, then perform the full-state calculation with the updated parameters), determine whether the operating parameters of each stage of the turbine meet the third design requirements. If so, the aerodynamic design is completed.

[0060] The first to third design requirements are all given according to specific design objectives.

[0061] In summary, this application has the following advantages:

[0062] It achieves improved turbine efficiency within limited geometry, increasing turbine efficiency by 3-4% at the typical point of minimum flow compared to a single-stage variable geometry turbine. It realizes a wide flow adjustment range and a highly efficient variable geometry low-pressure turbine design, greatly improving engine matching cycle benefits and enhancing overall engine performance.

[0063] By adopting the method of evenly distributing the expansion ratio of the variable geometry two-stage low-pressure turbine, it is possible to effectively ensure that the variable geometry two-stage turbine maintains high-efficiency operation at two typical state points (the flow adjustable boundary point).

[0064] It can effectively identify the impact of guide vane clearance loss in different states and positions, and effectively avoid the problem of insufficient efficiency margin of variable geometry turbine caused by insufficient consideration of turbine guide vane clearance during the design.

[0065] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A variable geometry two-stage low-pressure turbine aerodynamic design method, characterized in that, include: Determine the turbine operating parameters at typical state points of the low-pressure turbine with variable geometry of the engine's first-stage guide vanes; We select two typical state points with maximum and minimum flow rates respectively. Based on the turbine operating parameters of the typical design point with maximum flow rate, we perform flow path design. Based on the turbine operating parameters of the typical design point with minimum flow rate, we perform one-dimensional turbine aerodynamic design to obtain the one-dimensional design results. The turbine blade profile is determined based on the one-dimensional design results. The adjustable blade configurations of each turbine stage are established through three-dimensional modeling, including the adjustable guide vane configurations and rotor blade configurations of each turbine stage. Based on the adjustable blade configuration of each turbine, the performance parameters of typical state points with maximum and minimum flow are collected, quasi-three-dimensional calculations are performed, and it is determined whether the first design requirements are met. If so, the next step is executed. Based on the adjustable blade configuration of each turbine stage, the trend of the adjustable guide vane clearance of the turbine as the guide vane adjustment angle is estimated, and a three-dimensional model of each turbine stage is established. The three-dimensional model of each turbine stage is run, and the turbine operating parameters of each turbine stage at typical state points of maximum and minimum flow are collected to determine whether the second design requirements are met. If so, the next step is executed. By adjusting the turbine guide angles to different speeds, turbine characteristic calculations are performed to show the turbine characteristics as the expansion ratio changes. The turbine operating parameters of each stage of the turbine are obtained. After performing full-state calculations, it is determined whether the operating parameters of each stage of the turbine meet the third design requirements. If so, the aerodynamic design is completed.

2. The variable geometry two-stage low-pressure turbine aerodynamic design method as described in claim 1, characterized in that, When performing one-dimensional aerodynamic design of a turbine, the turbine power distribution is determined by giving the expansion ratio of each stage of the low-pressure turbine, and the load coefficient of each stage of the low-pressure turbine is obtained. At the same time, the flow coefficient of each stage of the turbine is determined by iterative method of the reaction force of each stage of the turbine, and the one-dimensional design result is obtained.

3. The variable geometry two-stage low-pressure turbine aerodynamic design method as described in claim 2, characterized in that, When determining turbine power distribution given the expansion ratios of each stage of a low-pressure turbine, the total inlet pressure of the first stage turbine at the typical state point with minimum flow is first defined as follows: The first-stage turbine outlet pressure is The outlet pressure of the second-stage turbine is The total turbine expansion ratio is defined as Its formula is = The first-stage turbine expansion ratio is... = Its value is The expansion ratio of the second-stage turbine is... = Its value is ; The total inlet pressure of the first-stage turbine is then defined as the typical state point where the flow rate is maximized. The first-stage turbine outlet pressure is The outlet pressure of the second-stage turbine is The total turbine expansion ratio is defined as Its formula is = The first-stage turbine expansion ratio is = The expansion ratio of the second-stage turbine is = By increasing the area of ​​the first-stage turbine guide vane, the turbine can operate at its typical operating point. It is 0.952 , It is 1.05 .

4. The variable geometry two-stage low-pressure turbine aerodynamic design method as described in claim 1, characterized in that, The specific method for performing quasi-3D calculations is as follows: The turbine blades are divided into multiple elementary stages along the radial direction, with each elementary stage corresponding to a radial position. The inlet and outlet velocities of each elementary stage are calculated based on the one-dimensional design results, and the flow loss of the elementary stage is estimated by combining a semi-empirical loss model. Based on the flow loss of each elementary stage, the turbine efficiency, expansion ratio, and flow rate are calculated and compared with the corresponding parameters of the first design requirements to determine whether the first design requirements are met.

5. The variable geometry two-stage low-pressure turbine aerodynamic design method as described in claim 4, characterized in that, The position of the rotating shaft is determined based on the configuration of the turbine adjustable guide vanes. Then, based on the range of change of the turbine guide vane adjustment angle, the range and change of the turbine adjustable guide vane clearance with the adjustment angle of the turbine guide vane are estimated. The angle of the first-stage turbine guide vane at the typical state point with the minimum flow rate is defined as 0°. Based on the range and variation of the turbine adjustable guide vane clearance with the angle adjustment of the turbine guide vane, a three-dimensional model of each stage of the turbine is established.

6. The variable geometry two-stage low-pressure turbine aerodynamic design method as described in claim 1, characterized in that, The turbine operating parameters at typical low-pressure turbine operating points include turbine speed, flow rate, expansion ratio, inlet aerodynamic parameters, external expansion size limit, and turbine efficiency.

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