Non-uniform flow state construction method for exhaust system

Abstract

The invention discloses a non-uniform flow state construction method for an exhaust system, which comprises the following steps: obtaining total temperature and total pressure in front of a turbine and at an outlet of the turbine through total performance calculation, obtaining flow field parameters of a rear section of the turbine through flow field simulation analysis of a turbine part, obtaining actual measurement temperature after the turbine, and obtaining a non-uniform flow state of the exhaust system. Then, the total temperature and the total pressure are calculated according to the overall performance, turbine flow field calculation is corrected according to the actually measured temperature behind a turbine, and finally the inlet condition of exhaust system flow field simulation is jointly constructed according to the velocity vector calculated through the flow field and the corrected temperature and pressure. The turbine flow field simulation pressure field is corrected by obtaining the actually measured temperature, the exhaust system flow field simulation boundary conditions are reflected more truly, the exhaust system flow field simulation precision is improved, and misleading caused by the fact that a designer carries out exhaust system design work is not likely to happen.

Description

Technical Field

[0001] The invention relates to a method for constructing a non-uniform flow state of an exhaust system, and belongs to the technical field of aeroengines. Background Art

[0002] Flow field simulation analysis is required when designing an exhaust system, and the accuracy of flow field simulation analysis is determined by factors such as models, grids, and boundary conditions. In the past, when conducting exhaust system flow field simulation analysis, the total temperature and pressure at the turbine outlet and the total temperature and pressure at the outer duct outlet calculated by the overall performance program were used as the inlet boundary conditions. The uneven temperature, velocity, and pressure distribution at the turbine outlet could not be considered. Even if the swirl angle can be set in the CFD simulation software, it can only give a single angle, and it is impossible to simulate the actual radial and circumferential velocity distribution, let alone accurately give the temperature and pressure distribution. However, the turbine outlet section parameters of actual aircraft engines are uneven, and a slight change in the inlet boundary conditions will affect the development of the subsequent flow field structure. This leads to the flow field results obtained by the exhaust system flow field simulation analysis carried out in the traditional way are far from the actual flow field results, which can easily mislead designers in carrying out exhaust system design work. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for constructing a non-uniform flow pattern in an exhaust system.

[0004] The present invention is achieved through the following technical solutions.

[0005] The present invention provides a method for constructing a non-uniform flow pattern of an exhaust system, comprising: obtaining the total temperature and total pressure before and at the turbine outlet through overall performance calculation, obtaining the flow field parameters of the turbine rear section through turbine component flow field simulation analysis, obtaining the actual temperature after the turbine, and then correcting the turbine flow field calculation to obtain the temperature and pressure through the overall performance calculation of the total temperature and total pressure and the actual temperature after the turbine, and finally constructing the inlet conditions of the exhaust system flow field simulation together with the velocity vector calculated by the flow field and the corrected temperature and pressure.

[0006] The modified turbine flow field calculation includes the following two steps:

[0007] a) According to the continuity equation, the measured temperature corrects the pressure field of the turbine flow field simulation, and the correction is made point by point according to the following formula:

[0008]

[0009] Where P 1i represents the total pressure at the i-th coordinate point of the turbine outlet section obtained from the turbine flow field simulation;

[0010] P 2iIt represents the total pressure at the i-th coordinate point of the turbine outlet section corrected according to the measured temperature after the turbine;

[0011] T 1i represents the total temperature at the i-th coordinate point of the turbine outlet section obtained from the turbine flow field simulation;

[0012] T 2i Represents the measured total temperature at the i-th coordinate point of the turbine outlet section.

[0013] b) To ensure consistency with the overall parameters, the temperature and pressure calculated based on the overall performance in the first step are corrected point by point according to the following formula:

[0014]

[0015] P3i=σ P ×P2i

[0016]

[0017] T3i=σ T ×T2i

[0018] In the formula, σ P Indicates the pressure correction factor;

[0019] σ T It represents the temperature correction factor;

[0020] P0 represents the average total pressure of the turbine rear outlet section obtained by overall performance simulation calculation;

[0021] T0 represents the average total temperature of the turbine rear outlet section obtained by overall performance simulation calculation;

[0022] n represents the total number of selected points in the turbine outlet cross section;

[0023] P3i represents the total pressure at the i-th coordinate point of the turbine outlet section obtained based on the correction of the overall performance parameters;

[0024] T3i represents the total temperature at the i-th coordinate point of the turbine outlet section obtained based on the correction of the overall performance parameters.

[0025] The beneficial effects of the present invention are as follows: the present application obtains the actual temperature to correct the turbine flow field simulation pressure field, more realistically reflects the exhaust system flow field simulation boundary conditions, improves the exhaust system flow field simulation accuracy, and is not likely to mislead designers in their exhaust system design work. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the temperature distribution of the rear section of the turbine of the present invention; DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0028] like Figure 1 shown.

[0029] The first step is to carry out overall performance calculation. The overall performance of an aircraft engine is a one-dimensional calculation. You can use gasturb or a self-written overall performance calculation program, select a specific operating point (such as the design point, high-altitude cruising point, maximum aerodynamic load point, etc.), and calculate the turbine inlet total temperature, turbine inlet total pressure, turbine outlet total temperature, and turbine outlet total pressure for subsequent flow field calculation and correction.

[0030] The second step is to carry out flow field simulation calculations of turbine components. The turbine component model has a great influence on the flow field behind the turbine. Therefore, the model for carrying out flow field simulation calculations of turbine components needs to include high-pressure turbine guide vanes, high-pressure turbine rotors, low-pressure turbine guide vanes, low-pressure turbine rotors and turbine bearings. In order to reduce the amount of calculations, the model can be reasonably adjusted according to the periodic situation (for example, when there are 7 turbine bearings, the model can be adjusted from full ring to 1 / 7). The input of the flow field simulation calculation of turbine components is the total temperature and total pressure of the turbine inlet calculated in the previous step of overall performance. The output of the flow field simulation of turbine components is the temperature field, pressure field and velocity field of the rear section of the turbine. The flow field simulation calculation of turbine components can be carried out through flow field simulation software (such as CFX).

[0031] The third step is to carry out rotating temperature measurement after the turbine. Use a rotating temperature measuring device to measure the temperature after the turbine. The rotating temperature measuring device needs to reasonably set the temperature measuring points. It is advisable to arrange 2 to 4 measuring probes circumferentially, and the measuring points on the probes should be evenly distributed in the radial direction. In this implementation case, there are 4 measuring probes in the circumference, and a measuring point is set at an interval of 20mm in the radial direction. The probes stay at 36 positions respectively, and each position is 5° circumferentially. The rotating temperature measuring device stays at each position for 10s. When the probe reaches the last position and stays there for 10s, the data collection ends. The measured temperature distribution is as follows: Figure 1 shown.

[0032] The fourth step is to carry out corrections based on test data and simulation data.

[0033] Since the turbine rear rotation temperature measurement test only obtains the temperature field, but cannot obtain the pressure field and velocity field, the simulated pressure field and velocity field must be used to construct the exhaust system inlet boundary conditions. However, if the simulated pressure field is directly referenced, the inlet flow field will be distorted (because temperature, pressure, and velocity together constitute the flow state, and a change in one parameter will inevitably cause changes in other parameters), so the pressure field needs to be corrected, which includes the following two steps:

[0034] a) According to the continuity equation, the pressure field of the turbine flow field simulation in the second step is corrected with the measured temperature in the third step, and the point-by-point correction is made according to the following formula:

[0035]

[0036] Where P 1i represents the total pressure at the i-th coordinate point of the turbine outlet section obtained from the turbine flow field simulation;

[0037] P 2i It represents the total pressure at the i-th coordinate point of the turbine outlet section corrected according to the measured temperature after the turbine;

[0038] T 1i represents the total temperature at the i-th coordinate point of the turbine outlet section obtained from the turbine flow field simulation;

[0039] T 2i Represents the measured total temperature at the i-th coordinate point of the turbine outlet section.

[0040] b) To ensure consistency with the overall parameters, the temperature and pressure calculated based on the overall performance in the first step are corrected point by point according to the following formula:

[0041]

[0042] P3i=σ P ×P2i (3)

[0043]

[0044] T3i=σ T ×T2i (5)

[0045] In the formula, σ P Indicates the pressure correction factor;

[0046] σ T It represents the temperature correction factor;

[0047] P0 represents the average total pressure of the turbine rear outlet section obtained by overall performance simulation calculation;

[0048] T0 represents the average total temperature of the turbine rear outlet section obtained by overall performance simulation calculation;

[0049] n represents the total number of selected points in the turbine outlet cross section;

[0050] P 3i It represents the total pressure at the i-th coordinate point of the turbine outlet section obtained by correction of the overall performance parameters;

[0051] T 3i represents the total temperature at the i-th coordinate point of the turbine outlet section obtained based on the correction of the overall performance parameters;

[0052] The fifth step is to construct the non-uniform boundary conditions at the inlet of the exhaust system. The pressure inlet is selected as the inlet boundary condition for the exhaust system flow field simulation. The parameters that need to be input include temperature, pressure, and velocity. The above-derived parameters are sorted according to the format required for flow field simulation, which must include the following parameters

[0053] (x i ,y i , z i , P 3i , T 3i , V xi , V yi , V zi )

[0054] Where xi represents the x-coordinate of the i-th coordinate point on the turbine outlet section;

[0055] yi represents the y coordinate of the i-th coordinate point on the turbine outlet section;

[0056] zi represents the z coordinate of the i-th coordinate point on the turbine outlet section;

[0057] Vxi represents the velocity in the x direction at the i-th coordinate point of the turbine outlet section obtained through turbine flow field simulation;

[0058] Vyi represents the velocity in the y direction at the i-th coordinate point of the turbine outlet section obtained through turbine flow field simulation;

[0059] Vzi represents the velocity in the z direction at the i-th coordinate point of the turbine outlet section obtained through turbine flow field simulation.

Claims

1. A method for constructing a non-uniform flow pattern in an exhaust system, characterized in that: include: The total temperature and total pressure before and at the turbine outlet are obtained through overall performance calculation. The flow field parameters of the turbine rear section and the measured temperature after the turbine are obtained through turbine component flow field simulation analysis. Then, the total temperature and total pressure are calculated through overall performance and the measured temperature after the turbine to correct the turbine flow field calculation to obtain the temperature and pressure. Finally, the velocity vector calculated in the flow field and the corrected temperature and pressure are used to jointly construct the inlet conditions for the exhaust system flow field simulation.

2. The method for constructing a non-uniform flow pattern in an exhaust system according to claim 1, characterized in that: The modified turbine flow field calculation includes the following two steps: a) According to the continuity equation, the measured temperature corrects the pressure field of the turbine flow field simulation, and the correction is made point by point according to the following formula: Where P 1i represents the total pressure at the i-th coordinate point of the turbine outlet section obtained from the turbine flow field simulation; P 2i It represents the total pressure at the i-th coordinate point of the turbine outlet section corrected according to the measured temperature after the turbine; T 1i represents the total temperature at the i-th coordinate point of the turbine outlet section obtained from the turbine flow field simulation; T 2i represents the measured total temperature at the i-th coordinate point of the turbine outlet section; b) To ensure consistency with the overall parameters, the temperature and pressure calculated based on the overall performance in the first step are corrected point by point according to the following formula: P3i=σ P ×P2i T3i=σ T ×T2i In the formula, σ P Indicates the pressure correction factor; σ T It represents the temperature correction factor; P0 represents the average total pressure of the turbine rear outlet section obtained by overall performance simulation calculation; T0 represents the average total temperature of the turbine rear outlet section obtained by overall performance simulation calculation; n represents the total number of selected points in the turbine outlet cross section; P3i represents the total pressure at the i-th coordinate point of the turbine outlet section obtained based on the correction of the overall performance parameters; T3i represents the total temperature at the i-th coordinate point of the turbine outlet section obtained based on the correction of the overall performance parameters.

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