Pneumatic design method for high-load turbine rear rectification blade cascade

Abstract

The invention provides a pneumatic design method for a high-load turbine rear rectification blade grid. The pneumatic design method comprises the steps of pneumatic design of a rectification supporting plate and pneumatic design of a meridian flow channel. The rectification supporting plates are high in load, the meridian flow channels are designed by being matched with blade-shaped channels of the rectification supporting plates under a certain number of rectification supporting plates, and the problem of large-scale separation flow caused by high load is solved from the aspect of meridian flow channel molded line design; the structure is compact, the total pressure loss is low, the weight of the whole machine can be reduced to a certain extent, and the manufacturability is improved; the method can be applied to the pneumatic design of the high thrust-weight ratio aero-engine turbine rear rectification cascade and the pneumatic design of the gas turbine engine core engine test turbine rear rectification cascade.

Description

Technical Field

[0001] This invention relates to an aerodynamic design method for a high-load turbine rear rectifier cascade, belonging to the field of aero-engine axial turbine technology. Background Technology

[0002] The function of an aero-engine axial turbine is to convert the high-temperature, high-pressure combustion gas energy in the combustion chamber into mechanical energy to drive the rotation of the compressor or fan components. The exhaust gas from the last-stage turbine rotor deviates from the axial direction by a certain angle and needs to be rectified to the axial direction by the turbine rear rectifier vanes before being discharged into the atmosphere through the exhaust structure. The greater the angle at which the incoming airflow (i.e., the exhaust gas from the last-stage turbine rotor) deviates from the axial direction, the greater its airflow deflection angle and the higher the load. Generally, a high pre-swirl in the incoming airflow, i.e., an airflow deviation from the axial direction of 30° or more, is considered a high-load turbine rear rectifier vane.

[0003] Modern aero engines, in pursuit of higher thrust-to-weight ratios and high performance, require turbine components with high efficiency and fewer stages. Therefore, to reduce weight and improve stage efficiency, the final-stage low-pressure turbine typically employs a high-load design and a large turning angle, with its outlet airflow angle often deviating from the axial direction by 30° or even more, resulting in a high load on the turbine's rear rectifier blade cascade. The rectifier support channel is in an expanded state, with the degree of expansion increasing with aerodynamic load. When airflow passes through, the adverse pressure gradient near the suction surface of the support intensifies, generating large-scale flow separation and causing rectification failure. To solve this flow separation problem, the commonly used aerodynamic design method is to use a large and small rectifier support design: the small support is arranged within the channel of the large support, with the trailing edges of both supports axially aligned. The airflow entering the small support is rectified in a portion of the leading edge region of the large support, reducing its axial deviation. The small support has a relatively low load and strong anti-separation capability. Simultaneously, the rectification by the small support reduces the adverse pressure gradient in the rear section of the large support, thereby suppressing flow separation. The disadvantages of this design scheme are that there are many types of support plates, poor structural manufacturability, and a large number of support plates, which increases the weight of the engine and is not conducive to high thrust-to-weight ratio design.

[0004] In addition, during the core engine test of the aero-engine, the high-pressure turbine rear rectifier cascade also faces the problem of high load. How to achieve a rectifier aerodynamic design with low total pressure loss becomes the key, which is of great significance for reducing costs and improving economic efficiency. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides an aerodynamic design method for a high-load turbine rear rectifier cascade, which avoids the large-scale separation flow problem of the turbine rear rectifier cascade caused by high load.

[0006] The present invention is achieved through the following technical solutions.

[0007] This invention provides an aerodynamic design method for a high-load turbine rear rectifier cascade, comprising:

[0008] Aerodynamic design of the rectifier support plate: Based on the engine axis, under the condition of high pre-swirl inflow with the intake deviating from the axis by 30° or more, the rectifier support plate is shaped so that the inlet geometric angle of each section of the rectifier support plate is equal to the intake airflow angle of that section, the outlet geometric angle deviates from the axis by no more than 5°, and the installation angle is set to 1 / 2 of the difference between the inlet geometric angle and the outlet geometric angle.

[0009] Meridian flow channel aerodynamic design: Extract the axial distribution data of the airfoil channel width of the middle section of the rectifier support plate, and design the meridian flow channel profile based on the distribution data, so that the upper and lower walls of the meridian flow channel expand at the minimum airfoil channel width position and contract at the maximum airfoil channel width position, forming an expansion-contraction channel structure.

[0010] The mounting angles of each section of the rectifier support plate satisfy the following relationship:

[0011]

[0012] The expansion endpoint of the meridional channel at the minimum airfoil channel width is located at the axial position corresponding to that width, and the contraction endpoint at the maximum airfoil channel width is located at the tail edge of the rectifier support plate or a predetermined downstream position.

[0013] The deviation angle of the outlet geometry from the axial direction is controlled to be between 0° and 5°.

[0014] The expansion-reception channel structure is configured as follows:

[0015] In the range from the leading edge of the rectifier support plate to the minimum airfoil channel width, the distance between the upper and lower walls of the meridional channel actively expands to offset the reduction in flow area caused by the contraction of the airfoil channel width in this range.

[0016] Between the minimum and maximum airfoil channel widths, the distance between the upper and lower walls of the meridional channel actively contracts to offset the increase in flow area caused by the expansion of the airfoil channel width within this range.

[0017] The beneficial effects of this invention are as follows: the rectifier support plate has a high load, and under a certain number of rectifier support plates, the meridional flow channel is designed by matching the rectifier support plate airfoil channel, thus solving the problem of large-scale separation flow caused by high load from the perspective of meridional flow channel profile design; it has the characteristics of compact structure and low total pressure loss, which can reduce the weight of the whole machine and improve manufacturability to a certain extent; it can be applied to the aerodynamic design of the turbine rear rectifier cascade of high thrust-to-weight ratio aero-engine and the aerodynamic design of the turbine rear rectifier cascade of gas turbine engine core test turbine. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the rectifier support blade air profile parameters and air profile channel width;

[0019] Figure 2 This is a schematic diagram showing the relationship between the meridional flow profile and the width distribution of the airfoil channel;

[0020] Figure 3 It is the streamline distribution of the rectifier support plate cross section;

[0021] In the diagram: 1-Inlet geometry angle, 2-Outlet geometry angle, 3-Installation angle, 4, 5-Engine axial direction, 6-Airfoil passage width, 7-Ratio of airfoil passage width to maximum airfoil passage width, 8-Ratio of axial distance from the leading edge to the axial chord length of the airfoil, 9-Leading edge of the rectifier strut, 10-Tail edge of the rectifier strut, 11-Upper and lower walls of the meridional passage, 12-Expansion endpoint at the minimum airfoil passage width, 13-Contraction endpoint at the maximum airfoil passage width, 14-Streamline at 10% airfoil height of the rectifier strut, 15-Streamline at 50% airfoil height of the rectifier strut, 16-Streamline at 90% airfoil height of the rectifier strut. Detailed Implementation

[0022] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0023] like Figure 1 and Figure 2 As shown, the design of the afterflow cascade for the test turbine of a medium-thrust engine core engine is as follows:

[0024] The rectifier support plate is designed based on the engine axis (the angle is defined as the angle between the airflow direction and the engine axis, with counterclockwise being positive and clockwise being negative). Under the condition of high pre-swirl inflow with the airflow deviating from the axis by more than 30°, the inlet geometric angle of each section of the rectifier support plate is made equal to the size of the airflow angle, the outlet geometric angle deviates from the axis by no more than 5°, and the installation angle is controlled to be close to half the difference between the inlet geometric angle and the outlet geometric angle.

[0025] For example:

[0026] The number of rectifier support plates and the axial chord length have been limited by the overall structure to 47 plates and 53 mm, respectively. The rectifier support plates are straight support plates with uniform cross-section. The design takes an inlet geometry angle of 35°, an outlet geometry angle of 5°, and an installation angle of 15°.

[0027] Meridian flow channel aerodynamic design: Extract the airfoil channel width distribution along the axial direction of the middle section of the rectifier support plate, and design the meridional flow channel in combination with the airfoil channel width matching, so that the meridional flow channel expands at the minimum airfoil channel width and contracts at the maximum airfoil channel width, which is an expansion-contraction type. The amount of expansion or contraction and the specific position of termination can be determined according to specific needs.

[0028] Specifically, the meridional channel is an expansion-contraction type channel, which effectively compensates for the channel contraction from the leading edge of the rectifier blade to the minimum airfoil channel width and the channel expansion from the minimum airfoil channel width to the maximum airfoil channel width. This reduces the axial gradient of the rectifier blade cascade flow area, weakens the adverse pressure gradient generated when the airflow passes through the rectifier blade, and thus suppresses or eliminates large-scale flow separation, such as... Figure 3 As shown.

[0029] In summary, this invention can be used for the aerodynamic design of the turbine rear rectifier cascade in core engine testing of high thrust-to-weight ratio aero engines and gas turbine engines.

Claims

1. An aerodynamic design method for a high-load turbine rear rectifier cascade, characterized in that: include: Aerodynamic design of the rectifier support plate: Based on the engine axis (4, 5), under the condition of high pre-swirl inlet flow with the intake deviating from the axis by 30° or more, the rectifier support plate is shaped so that the inlet geometric angle (1) of each section of the rectifier support plate is equal to the inlet airflow angle of that section, the outlet geometric angle (2) deviates from the axis by no more than 5°, and the installation angle (3) is set to 1 / 2 of the difference between the inlet geometric angle (1) and the outlet geometric angle (2); Meridian flow channel aerodynamic design: Extract the axial distribution data of the airfoil channel width (6) of the middle section of the rectifier support plate, and design the meridian flow channel profile based on the distribution data, so that the upper and lower walls (11) of the meridian flow channel expand at the minimum airfoil channel width position and contract at the maximum airfoil channel width position, forming an expansion-contraction channel structure.

2. The aerodynamic design method for high-load turbine rear rectifier cascade as described in claim 1, characterized in that: The installation angles (3) of each section of the rectifier support plate satisfy the following relationship:

3. The aerodynamic design method for high-load turbine rear rectifier cascade as described in claim 1, characterized in that: The expansion endpoint (12) of the meridional channel at the minimum airfoil channel width is located at the axial position corresponding to that width, and the contraction endpoint (13) at the maximum airfoil channel width is located at the tail edge (10) of the rectifier branch plate or at a predetermined downstream position.

4. The aerodynamic design method for high-load turbine rear rectifier cascade as described in claim 1, characterized in that: The deviation angle of the outlet geometry angle (2) from the axial direction is controlled to be 0° to 5°.

5. The aerodynamic design method for high-load turbine rear rectifier cascade as described in any one of claims 1 to 3, characterized in that: The expansion-reception channel structure is configured as follows: In the range from the leading edge (9) of the rectifier support plate to the position of the minimum airfoil channel width, the distance between the upper and lower walls (11) of the meridional channel actively expands to offset the reduction in flow area caused by the contraction of the airfoil channel width in this range; In the interval from the minimum airfoil channel width to the maximum airfoil channel width, the distance between the upper and lower walls (11) of the meridional channel actively shrinks to offset the increase in flow area caused by the expansion of the airfoil channel width in this interval.

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