Optimization method suitable for rotating blade pressure surface double-wall impact structure

Abstract

The invention discloses an optimization method suitable for a rotating blade pressure surface double-layer wall impact structure. The optimization method comprises the steps that a target surface heat exchange coefficient and a flow deflection mechanism are obtained; according to the target surface heat exchange coefficient and the flow deflection mechanism, the inclination angle of the impact hole is sampled, sampling points are substituted into a double-layer wall impact model for parametric modeling and are substituted into a solver for solving, and heat exchange results of the double-layer wall structure corresponding to different sampling points under the rotation condition are obtained; according to the heat exchange result, target surface heat exchange data are extracted, and a Kriging proxy model is constructed based on the target surface heat exchange data; the heat exchange result is input into the Kriging agent model, and an impact cooling result and an impact angle are obtained; and based on the impact cooling result and the impact angle, optimizing by utilizing a genetic algorithm to obtain an optimal heat exchange result and a corresponding impact hole inclination angle. The impingement cooling effect in the rotating state can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of gas turbine turbine blade cooling, and in particular relates to an optimization method for a double-wall impact structure of a rotating blade pressure surface. Background Art

[0002] As one of the most critical components of the core of an aircraft engine, the turbine blade is the component with the worst working conditions in the turbine engine, and it is also the most important rotating component. The turbine blade is subjected to the high-temperature gas scouring and temperature changes during the engine start-up and shutdown cycles. The rotor blade is subjected to the centrifugal force and temperature difference thermal stress at high speed. It is one of the key and difficult points in the cooling design of the hot end components of the gas turbine, and higher requirements are placed on the materials and cooling technology of the turbine blade. The double-wall structure is an efficient composite cooling method that combines the impingement cooling structure with the air film cooling structure. It is widely used in aircraft engine turbine blades because of its high local heat transfer coefficient of impingement cooling and the external air film insulation effect. For the pressure surface of the mid-chord area of ​​the turbine blade, the impact hole of the conventional double-wall structure currently uses a hole that is 90° perpendicular to the plane of the impingement plate. When the blade is stationary, the jet can reach the impact target surface vertically. The vertically impinging cooling fluid directly acts on the cooling surface, with high turbulent kinetic energy, and can more effectively destroy the thermal boundary layer on the surface, thereby achieving a good impact cooling effect. However, when rotating, the impact jet will be affected by the Coriolis force, centrifugal force, and buoyancy force, and the jet will deviate from the vertical position and tilt in the direction of the resultant force. When the impact is tilted, the momentum of the jet in the vertical direction will decrease, and part of the energy will be dispersed in the direction parallel to the surface. When reaching the target surface, the turbulent kinetic energy is also relatively low, resulting in reduced heat exchange efficiency. Therefore, the impact cooling effect of the impact target surface during rotation will be greatly reduced compared to when it is stationary, and the impact cooling occupies a dominant position in the overall cooling effect of the double-wall composite structure. The reduction in cooling effect means that the blade faces the risk of ablation during rotation. At present, there are many studies on the internal cooling structure of the blade in the static state, but there are fewer studies on the cooling of the blade in the rotating state, and the optimization of the impact cooling structure in the rotating state is even more scarce. Therefore, how to correct the double-wall impact jet under the rotating condition of the blade so that the double-wall impact structure can restore or even exceed the cooling effect in the static state in the rotating state is a problem that needs to be solved urgently in this field. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes an optimization method for the double-wall impact structure of the pressure surface of a rotating blade, which can improve the impact cooling effect under the rotating state and avoid the problem of decreased impact cooling performance caused by the deflection of the impact jet under rotating conditions, which in turn leads to local overheating and ablation of the outer part of the blade.

[0004] To achieve the above object, the present invention provides an optimization method for a double-wall impact structure of a rotating blade pressure surface, comprising:

[0005] Obtain target surface heat transfer coefficient and flow deflection mechanism;

[0006] The impact hole angle is sampled according to the target surface heat transfer coefficient and the flow deflection mechanism, the sampling point is brought into the double-wall impact model for parameterized modeling and brought into the solver for solving, and the heat transfer results of the double-wall structure corresponding to different sampling points under the rotating condition are obtained;

[0007] According to the heat exchange results, target surface heat exchange data is extracted, and based on the target surface heat exchange data, a Kriging proxy model is constructed;

[0008] Inputting the heat transfer result into the Kriging proxy model to obtain the impingement cooling result and the impingement angle;

[0009] Based on the impingement cooling result and the impingement angle, a genetic algorithm is used to find the optimal heat exchange result and its corresponding impingement hole angle.

[0010] Optionally, sampling the impact hole angle includes:

[0011] The impact hole angle is sampled using the LHS sampling method to obtain impact hole inclination angle sample points.

[0012] Optionally, based on the target surface heat transfer data, constructing a Kriging proxy model includes:

[0013] Based on the target surface heat transfer data, construct an initial proxy model;

[0014] The modeling points of the initial proxy model are dynamically refined to obtain the Kriging proxy model.

[0015] Optionally, the method of dynamically refining the modeling points of the initial proxy model is: using the LHS method to increase the number of sample points until the Kriging model accuracy is met.

[0016] Optionally, based on the impingement cooling result and the impingement angle, a genetic algorithm is used to find the optimal heat exchange result:

[0017] Using a genetic algorithm to optimize the impact cooling result and obtain an optimal solution;

[0018] The impact angle corresponding to the optimal solution, that is, the optimal heat exchange result, is extracted.

[0019] Optionally, using a genetic algorithm to optimize the impact cooling result to obtain the optimal solution includes:

[0020] Using the impact cooling result and the impact angle as initial solution data, and calculating the fitness value of the initial solution data according to a fitness function;

[0021] Selecting a preset number of fitness values ​​and obtaining genetic information of the fitness values;

[0022] Select the genetic information of two solution data to exchange and obtain new solution data;

[0023] The new solution data replaces part of the initial solution data until the maximum target surface relative Nusselt number is obtained.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] The present invention utilizes an optimization method based on a kriging proxy model for optimization, and adjusts the angle of the impact hole on the impact plate under a given rotation condition through the optimization method, thereby improving the impact cooling effect under a rotation state, and changing the jet deflection degree of the double-wall cooling structure under a given rotation condition, so that the impact jet in the rotation state can reach the impact target surface vertically as when stationary, thereby greatly reducing the weakening effect of the rotation on the impact cooling effect, which is beneficial to improving the impact cooling effect, thereby reducing the impact target surface temperature, and reducing the risk of high-temperature ablation of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 A flow chart of an optimization method for a double-wall impact structure on a pressure surface of a rotating blade suitable for use in an embodiment of the present invention;

[0028] Figure 2 A specific application geometry structure based on the optimization method according to an embodiment of the present invention;

[0029] Figure 3 The mid-section velocity cloud diagram of the double-wall structure in static and rotating states and the double-wall structure in rotating state with optimized impact holes in the embodiment of the present invention is compared;

[0030] Figure 4 The spanwise average Nusselt number distribution of the double-wall structure in the static and rotating states and the double-wall structure in the rotating state with impact hole optimization at different flow direction positions of the embodiment of the present invention;

[0031] Figure 5 Comparison diagram of average Nusselt number of impact target surface in embodiments of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0034] This embodiment provides an optimization method for a double-wall impact structure of a rotating blade pressure surface, as shown in 1, which specifically includes the following steps:

[0035] Set up simulation experiments and clarify the direction of jet deflection and the degree of heat transfer weakening based on the simulation experiment results;

[0036] Specifically, the internal flow and heat transfer characteristics of the model under given rotation conditions are studied using simulation software or experiments, and the direction of jet deflection and the degree of heat transfer weakening are determined based on the results;

[0037] The purpose of this part of the study is to understand the deflection direction and degree of the jet under given rotation conditions, and to understand the influence mechanism of the rotation-derived force on the jet, so as to give the parameter range when parametric modeling.

[0038] The simulation results were sampled, and parameterized modeling was performed based on the jet deflection direction and the degree of heat transfer weakening to obtain the heat transfer results of the double-wall structure corresponding to different sampling points under rotating conditions.

[0039] Specifically, a number of sample points are generated using the LHS sampling method, and are brought into the impact hole angle in the model for parametric modeling, and then returned to the solver for automatic solution to obtain the heat transfer results;

[0040] According to the heat transfer results, the target surface heat transfer data is extracted, and based on the target surface heat transfer data, the Kriging proxy model is constructed;

[0041] Specifically, the essence of the Kriging model is to perform a certain linear weighted combination of the information of a point within a certain range near the prediction point to infer the unknown part of the information of this point. It has the ability to fit nonlinear functions well and can provide error estimates to judge the degree of model fitting.

[0042] Input the heat transfer results into the Kriging proxy model to obtain the impingement cooling results;

[0043] Based on the impingement cooling results and the impingement angle, the genetic algorithm is used to find the optimal heat transfer result and its corresponding impingement hole angle.

[0044] Furthermore, sampling the simulation experiment results includes:

[0045] The LHS sampling method is used to sample the simulation experimental results and obtain the impact hole inclination angle sample points.

[0046] Specifically, the LHS method is a Latin hypercube design method, which is a type of DOE experimental design method. It has the advantages of flexible sample size and no restrictions on spatial design dimensions. It is more suitable for sampling in turbine blade structural parameter optimization. However, the DOE part of this method includes but is not limited to the use of this method.

[0047] Furthermore, based on the target surface heat transfer data, the Kriging proxy model is constructed including:

[0048] Based on the target surface heat transfer data, an initial proxy model is constructed;

[0049] Dynamically refine the modeling points of the initial proxy model to obtain the Kriging proxy model.

[0050] Furthermore, the method of dynamically refining the modeling points of the initial proxy model is: using the LHS method to increase the number of sample points until the Kriging model accuracy is met.

[0051] Furthermore, based on the impingement cooling results and impingement angle, the genetic algorithm is used to find the optimal heat transfer result:

[0052] Genetic algorithm is used to optimize the impact cooling results and obtain the optimal solution;

[0053] The impact angle corresponding to the optimal solution is extracted, which is the optimal heat transfer result.

[0054] Furthermore, the genetic algorithm is used to optimize the impact cooling results, and the optimal solution is obtained including:

[0055] The impact cooling result and the impact angle are used as initial solution data, and the fitness value of the initial solution data is calculated according to the fitness function;

[0056] Select a preset number of fitness values ​​and obtain genetic information of the fitness values;

[0057] Select the genetic information of two solution data to exchange and obtain new solution data;

[0058] The new solution data replaces part of the initial solution data until the maximum target surface relative Nusselt number is obtained.

[0059] The present invention also provides an application of an optimization method suitable for a double-wall impact structure on a rotating blade pressure surface, comprising: applying inclined impact holes corresponding to the optimal heat exchange result obtained by the optimization method to the double-wall structure.

[0060] Further, the double-wall structure comprises: an air film plate, an impact cavity, an impact plate and an air inlet cavity arranged in sequence;

[0061] Among them, a plurality of air film holes are arranged on the air film plate, and a plurality of impact holes are arranged on the impact plate.

[0062] like Figure 2 As shown in the figure, the double-wall impact structure of the blade pressure surface includes an air inlet cavity, an impact plate, an impact cavity and an air film plate, wherein a number of impact holes and air film holes with equal spacing are opened on the impact plate and the air film plate. One side of the air inlet cavity serves as the cold air inlet. After entering from the inlet, the cold air turns a certain angle and enters the impact hole. After reaching the impact target surface, it flows along the target surface. Subsequently, the wall jet formed by the impact cooling will converge to the air film hole due to pressure driving and flow out. The position at a certain distance from the cold air inlet is the rotation axis, and the direction is the same as that of the cold air inlet. Figure 2 The Y-axis of the impact jet is in the same direction. In the rotating state, the jet will be affected by the rotation-derived force and deflected. For the pressure surface position in the middle of the blade chord, the Coriolis force it is subjected to points in the direction of the high rotation radius, and the centrifugal force and the pressure gradient generated by the centrifugal force field cancel each other out. Due to the suction effect of the air film holes, the upstream influence of the cross flow generated by the impact cooling on the downstream influence is almost negligible. Therefore, the deflection of the impact jet in the rotating state is mainly dominated by the Coriolis force. The jet deflection will cause the momentum of the cold air to decrease when it reaches the target surface, thereby reducing the impact cooling effect. By adjusting the angle α along the flow direction of the impact hole, the deflection direction of the impact jet under rotating conditions can be changed, and a higher impact target surface heat exchange effect can be achieved, thereby reducing the overall temperature of the blade pressure surface substrate.

[0063] Furthermore, after the cooling air enters the air inlet cavity, it turns at a preset angle and enters the impact hole, and after the jet reaches the impact target surface through the impact hole, it flows out from the air film hole.

[0064] Furthermore, the impact hole is an inclined impact hole, and the inclination angle α of the inclined impact hole is the angle between the extension line of the vertex to the right and the line connecting the vertex and the center of the impact hole on one side of the air intake cavity, with the midpoint of the center of the impact hole on one side of the impact cavity as the vertex.

[0065] Furthermore, the ratio of the thickness of the impact plate to the diameter of the impact hole is 1, and the ratio of the distance from the impact plate to the impact target surface to the diameter of the impact hole is 1-3.

[0066] Specifically, the impact hole diameter is d0, and the air film hole diameter is 0.4d0.

[0067] Furthermore, the ratio of the spanwise hole spacing of the impact holes to the diameter of the impact holes is 3 to 4, and the ratio of the flowwise hole spacing of the impact holes to the diameter of the impact holes is 3 to 4;

[0068] The span and flow direction spacing of the air film holes should be consistent with the impact hole spacing, and an air film hole should be provided on the air film plate at the corresponding position in the middle of every four impact holes.

[0069] The spanwise and flowwise hole spacings of the air film holes should be consistent with the impact hole spacings, and an air film hole should be opened on the impact target surface at the corresponding position in the middle of every four impact holes.

[0070] A layer of zirconium oxide (ZrO2)-based thermal barrier coating material is sprayed on the outer surface of the air film plate, which is combined with the air film cooling to ensure that when the speed does not reach the established working conditions, there will be no ablation of the outer surface of the double-walled metal substrate due to the impact cooling efficiency not reaching the maximum.

[0071] In this embodiment, for a given rotation speed Ro j = 0.12 is used as a comparative example of flow field heat exchange of the double-wall square cavity structure on the pressure surface of the blade. According to the similarity principle, the real blade is modeled to analyze its flow mechanism. The aperture d0 of the impact hole 2 is 20mm, the aperture of the air film hole is 8mm, the thickness of the impact plate is 20mm, the thickness of the air film plate is 10mm, the relative impact distance h / d0 is 2, the impact hole spacing and the air film hole spacing p / d0, s / d0 are both 3.5, the rotation radius r0 is 20d0, the original double-wall structure impact hole inclination angle is the normal direction of the impact plate, that is, α = 90°, and the impact hole inclination angle of the double-wall structure after optimization calculation is α = 124°.

[0072] The working principle of this embodiment is as follows: in the rotating state, the cooling air flow from the internal channel of the turbine blade flows into the air supply cavity from the cold air inlet, and flows into the impact cavity through the optimized impact hole with an inclined angle. The impact jet is deflected in the impact cavity by the rotation-derived Coriolis force, and finally reaches the impact target surface at an angle as close to 90° as possible, thereby maximizing the impact cooling effect, reducing the overall temperature of the pressure surface and improving the cooling uniformity.

[0073] In order to verify the effectiveness of the present invention, the average Nusselt number of the double-wall impact target surface flow direction and the overall average Nusselt number of three different working conditions and structures in the static state, the rotating state and the rotating state with optimized inclined impact holes were calculated. The three structures only differed in the impact hole angle α and the rotation speed, and the number and size of the impact holes and air film holes, the cold air intake flow rate, and the impact target surface heating heat flux remained unchanged. The optimization method adopts the optimization method disclosed in the present invention, the calculation process uses UG modeling, ICEM generates structured grids, uses CFX solver to solve, and uses the optimization method based on the kriging proxy model to optimize, so as to obtain the optimal impact hole angle at a given rotation speed.

[0074] Figure 3The mid-section velocity cloud diagrams of the double-wall structure in the static and rotating states and the double-wall structure in the rotating state with impact hole optimization are compared. Figure 4 The spanwise average Nusselt number distributions at different flow direction positions of the double-wall structure of the embodiment in static and rotating states and the double-wall structure in rotating state with impact hole optimization are compared. Figure 5 The horizontal axis represents the distance in the flow direction, and the vertical axis represents the relative Nusselt number distribution.

[0075] Depend on Figure 3 From the velocity cloud diagram, it can be found that in the static state, the angle between the jet and the impact target surface is almost 90°. In the rotating state, the jet will deflect to the high radius side due to the Coriolis force, and some jets will deflect to a large extent and even fail to reach the impact target surface. After the impact hole optimization disclosed in the present invention, the impact hole inclination angle and the Coriolis force produce a coupling effect, so that the impact jet returns to a state of being almost perpendicular to the target surface when it reaches the target surface.

[0076] When studying heat transfer performance, the relative Nusselt number Nu / Nu0 is usually used for evaluation. The detailed formula is as follows:

[0077]

[0078] Nu0=0.023Re 0.8 Pr 0.4

[0079] The Nusselt number Nu is derived from the wall heat transfer coefficient h, where q w is the local wall heat flux, T w is the wall temperature. k is the thermal conductivity of air, which is taken as 0.025. Nu0 is the Nusselt number of the fully developed flow in the heated circular tube, which is derived from the Dittus-Boelter formula. The higher the relative Nusselt number Nu / Nu0, the better the heat transfer effect.

[0080] The Nu / Nu0 peak corresponds to the stagnation point position of the impact jet. It can be seen that for the unoptimized impact hole, the peak distribution of the static structure is relatively uniform, while the relative Nusselt number peak in the rotating state is deflected in the direction of the rotation-derived Coriolis force, and the peak value is reduced, and the heat exchange effect is reduced. For the optimized impact hole, its relative Nusselt number peak flow position basically moves back to the position of the static working condition, and the relative Nusselt number peak value rebounds and even partially exceeds the static state, indicating that after the impact hole is optimized, its impact cooling effect has been significantly improved in the rotating state, and the impact cooling effect of some impact hole positions even exceeds the impact cooling effect at rest. It fully demonstrates the effectiveness and superiority of this patent.

[0081] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for optimizing a double-wall impact structure of a rotating blade pressure surface, characterized in that: include: Obtain target surface heat transfer coefficient and flow deflection mechanism; The impact hole angle is sampled according to the target surface heat transfer coefficient and the flow deflection mechanism, the sampling point is brought into the double-wall impact model for parameterized modeling and brought into the solver for solving, and the heat transfer results of the double-wall structure corresponding to different sampling points under the rotating condition are obtained; According to the heat exchange results, target surface heat exchange data is extracted, and based on the target surface heat exchange data, a Kriging proxy model is constructed; Inputting the heat transfer result into the Kriging proxy model to obtain the impingement cooling result and the impingement angle; Based on the impingement cooling result and the impingement angle, a genetic algorithm is used to find the optimal heat exchange result and its corresponding impingement hole angle.

2. The optimization method of a double-wall impact structure of a rotating blade pressure surface according to claim 1, characterized in that: Sampling the impact hole angle includes: The impact hole angle is sampled using the LHS sampling method to obtain impact hole inclination angle sample points.

3. The optimization method of a double-wall impact structure of a rotating blade pressure surface according to claim 1, characterized in that: Based on the target surface heat transfer data, constructing the Kriging proxy model includes: Based on the target surface heat transfer data, construct an initial proxy model; The modeling points of the initial proxy model are dynamically refined to obtain the Kriging proxy model.

4. The optimization method of the double-wall impact structure of the pressure surface of a rotating blade according to claim 3, characterized in that: The method of dynamically refining the modeling points of the initial proxy model is: using the LHS method to increase the number of sample points until the Kriging model accuracy is met.

5. The optimization method of the double-wall impact structure of the pressure surface of a rotating blade according to claim 1, characterized in that: Based on the impingement cooling results and impingement angles, a genetic algorithm is used to find the optimal heat transfer result: Using a genetic algorithm to optimize the impact cooling result and obtain an optimal solution; The impact angle corresponding to the optimal solution, that is, the optimal heat exchange result, is extracted.

6. The optimization method of the double-wall impact structure of the pressure surface of a rotating blade according to claim 5, characterized in that: The genetic algorithm is used to optimize the impact cooling result to obtain the optimal solution, including: Using the impact cooling result and the impact angle as initial solution data, and calculating the fitness value of the initial solution data according to a fitness function; Selecting a preset number of fitness values ​​and obtaining genetic information of the fitness values; Select the genetic information of two initial solution data to exchange and obtain new solution data; The new solution data replaces part of the initial solution data until the maximum target surface relative Nusselt number is obtained.

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