Gas turbine engine airflow total temperature test probe design method

Abstract

The invention discloses a gas turbine engine airflow total temperature test probe design method. The method comprises the steps that S1, gas turbine engine main runner airflow and related parameters of a total temperature test probe are collected; s2, calculating a total temperature measurement speed error, a radiation error and a heat conduction error according to the collected related parameters of the total temperature test probe; s3, calculating a total error of total temperature measurement; s4, solving the partial derivative function of the stagnation velocity of the internal airflow of the stagnation chamber according to the total error of the total temperature measurement, and obtaining the optimal stagnation velocity of the internal airflow of the stagnation chamber and the corresponding stagnation airflow Mach number; s5, calculating a total temperature measurement heat conduction error in the step S2 by using the obtained optimal air flow stagnation speed in the stagnation chamber; s6, whether the heat conduction error under the current length-diameter ratio can be ignored or not is judged, if yes, the step S7 is executed, and if not, the step S8 is executed; s7, calculating the exhaust hole size of the stagnation chamber of the total temperature probe based on a gas continuity equation; and S8, continuously increasing the length-diameter ratio of the thermo wire immersed in the detected airflow, so that the heat conduction error meets the negligible condition.

Description

Technical Field

[0001] This invention belongs to the field of mainstream flow field testing technology for gas turbine engines, specifically, it relates to a design method for a gas turbine engine airflow total temperature testing probe. Background Technology

[0002] The total temperature parameter of the airflow at various performance evaluation test sections within the internal flow channels of a gas turbine engine is a crucial parameter for assessing the overall performance of the engine and its components. Accurately obtaining the steady-state total temperature of the airflow at each test section is essential for calculating overall engine performance, matching between components, and safety monitoring. Inside a gas turbine engine, the airflow temperature varies widely, and the temperature gradient within the same test section is also significant. During engine or component testing, a fixed multi-point total temperature probe is used to measure the average total temperature of the airflow at a given test section. The gas turbine engine's multi-point total temperature probe is arranged radially along the engine, with thermocouples mounted inside a stagnation chamber. This stagnation chamber not only reduces the velocity of the measured airflow but also shields the thermocouples from other radiation sources, ensuring that the thermocouple readings are as close as possible to the measured total temperature of the airflow. Therefore, the key technology in the design of the total temperature probe is to rationally design its structure to minimize the sum of thermocouple velocity error, thermal conductivity error, and radiation error.

[0003] The total temperature test error of gas turbine engine airflow is a combination of various errors mentioned above. The magnitude and proportion of each error in the total error vary depending on the airflow conditions and test environment. For example, in the total temperature test error of compressor airflow with high Mach number and low temperature, velocity error dominates; while in the total temperature test error of combustion chamber outlet airflow with low Mach number and high temperature, radiation error accounts for a higher proportion of the total error. Currently, there is no standardized system for the design of multi-point total temperature probe structures. Designers mostly design the total temperature probe based on the specific test environment, focusing solely on avoiding or reducing a single, relatively large test error. While this can reduce the overall test error to some extent, it is difficult to design a total temperature probe structure with optimal performance. Summary of the Invention

[0004] To address the problem that existing gas turbine engine airflow total temperature test probe design methods cannot design the optimal structure of the total temperature probe based on the aerodynamic state of the measured airflow, this invention provides a gas turbine engine airflow total temperature test probe design method.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for designing a gas turbine engine airflow total temperature test probe, comprising the following steps: S1. Collect relevant parameters from the gas turbine engine's main flow airflow and total temperature test probe; S2. Calculate the total temperature measurement speed error, radiation error, and thermal conductivity error based on the relevant parameters collected from the total temperature test probe. S3. Structurally ensure the aspect ratio of the thermocouple wires in the immersion airflow in the stagnation chamber, ignore thermal conductivity error, and calculate the total error of the total temperature measurement. S4. Calculate the partial derivative of the total error of the total temperature measurement with respect to the stagnation velocity of the airflow inside the stagnation chamber, and obtain the optimal stagnation velocity of the airflow inside the stagnation chamber and the corresponding Mach number of the stagnation airflow. S5. Recalculate the total temperature measurement thermal conductivity error in step S2 using the optimal airflow stagnation velocity inside the stagnation chamber obtained in step S4. S6. Determine whether the thermal conductivity error under the current aspect ratio is negligible. If yes, proceed to step S7; otherwise, proceed to step S8. S7. Calculate and determine the exhaust port size of the stagnation chamber of the total temperature probe based on the gas continuity equation; S8. Continue to increase the aspect ratio of the filaments immersed in the measured airflow to make it meet the condition that the thermal conductivity error is negligible.

[0006] Furthermore, the total temperature test probe includes a stagnation chamber, thermocouple wires, and an insulator; The relevant parameters of the total temperature test probe include the stagnation chamber inlet size. D in Regulation chamber outlet size D out Effective length of stagnation chamber L Thermocouple wire diameter d Diameter of the hot junction of the even wire D Length of thermocouple wire immersed in airflow l Distance from the hot junction of the even wire to the entrance of the stagnation chamber S， Total temperature of the main airflow under test T t Mach number of free flow in the mainstream channel M ∞ Mach number of stagnant airflow inside the stagnant room M j (Convert airflow velocity) u j Stabilizing indoor wall temperature T w Total temperature probe thermocouple cold junction temperature T b .

[0007] Furthermore, the formula for calculating the total temperature measurement speed error is as follows: in, uj To stagnate the airflow velocity inside the room r 裸 The root is the thermal coefficient of the thermocouple wire junction, which is generally taken as 0.86±0.09 when the wire and the airflow are parallel. c p The isobaric specific heat of the airflow is determined based on the static temperature of the airflow. T Sure; The formula for calculating radiation error is: in, T j The total temperature of the airflow being measured. ε The emissivity of the thermocouple measuring end is determined by the thermocouple wire material; c 0 represents the absolute blackbody radiation coefficient, taken as 5.699 W / (m²). 2. K 4 ); B For coefficients, m As an exponent, when the thermocouple wire and the airflow are parallel. B =0.0845, m =0.674; D For qualitative dimensions, the diameter of the hot junction of the ferrite wire is taken; the airflow thermal conductivity is also considered. λ f and kinematic viscosity coefficient ν Determined based on the total temperature of the measured airflow in the criterion equation; T w The temperature of the stagnation chamber wall can be approximated as ( ). T j + T ) / 2, T For airflow static temperature; The formula for calculating thermal conductivity error is: in, T b The temperature of the cold junction of the thermocouple on the total temperature probe (distance from the hot junction) l (temperature at the location) l / d The aspect ratio of the thermocouple wire immersed in the airflow. λ m and α l These are the thermal conductivity and surface heat transfer coefficient of the thermocouple, respectively, both of which are determined by the thermocouple material.

[0008] Furthermore, in step S3, the aspect ratio of the thermocouple wire in the immersion airflow in the stagnation chamber is l / d≮10, and the thermal conductivity error ΔTc≤e, where e is a constant; Formula for calculating the total error of total temperature measurement: Δ T =Δ Tv + Δ T r ,Right now: .

[0009] Furthermore, in step S4, let ∂(ΔT) / ∂(u) j With )=0, the formula for calculating the optimal stagnation velocity of airflow inside the stagnation chamber can be obtained: , The formulas for calculating the optimal stagnation velocity and the corresponding Mach number of the stagnation airflow inside the stagnation chamber are as follows: Where k is the adiabatic index of air, taken as 1.4; and R is the gas constant of air, taken as 287.06 J / (kg·K).

[0010] Furthermore, in step S8, the length of the stagnation chamber needs to be determined based on the length of the ferrule and the requirement that the distance between the ferrule hot junction and the stagnation chamber inlet should be greater than the diameter of the ferrule hot junction.

[0011] Furthermore, the formula for calculating the gas continuity equation is as follows: in, F in and F out These are the inlet and outlet areas of the stagnation chamber, respectively. q ( λ ∞ )and q ( λ j佳 The free-flow Mach numbers of the main channel airflow are respectively... M ∞ Optimal Mach number for stagnant airflow inside the stagnant chamber M j佳 The corresponding aerodynamic function; Formula for calculating the exhaust port size of the total temperature probe stagnation chamber: in, n The number of exhaust vents in the stagnation chamber is generally 2 to 4.

[0012] Compared with the prior art, the present invention has the following advantages: Based on the aerodynamic parameters of the specific test environment of the total temperature probe, and with the goal of minimizing the comprehensive test error of the airflow total temperature, the detailed structural parameters of the total temperature probe are precisely designed, which greatly improves the design efficiency and test performance of the total temperature probe.

[0013] This addresses the technical deficiency of existing gas turbine engine testing probes that cannot be designed with the optimal structure based on the aerodynamic state of the measured airflow to minimize the overall airflow temperature measurement error. Attached Figure Description

[0014] Figure 1 This is an overall flowchart of a gas turbine engine airflow total temperature test probe design method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the multi-point total temperature probe structure in an embodiment of the present invention; Figure 3 This is a schematic diagram of the total temperature probe structure in an embodiment of the present invention; Figure 4 This is a schematic diagram of the airflow parameters inside the total temperature probe in an embodiment of the present invention. Detailed Implementation

[0015] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0016] like Figure 1 As shown, this embodiment provides a design method for a gas turbine engine airflow total temperature test probe, including the following steps: S1. Collect relevant parameters from the gas turbine engine's main flow airflow and total temperature test probe; S2. Calculate the total temperature measurement speed error, radiation error, and thermal conductivity error based on the relevant parameters collected from the total temperature test probe. S3. Structurally ensure the aspect ratio of the thermocouple wires in the immersion airflow in the stagnation chamber, ignore thermal conductivity error, and calculate the total error of the total temperature measurement. S4. Calculate the partial derivative of the total error of the total temperature measurement with respect to the stagnation velocity of the airflow inside the stagnation chamber, and obtain the optimal stagnation velocity of the airflow inside the stagnation chamber and the corresponding Mach number of the stagnation airflow. S5. Recalculate the total temperature measurement thermal conductivity error in step S2 using the optimal airflow stagnation velocity inside the stagnation chamber obtained in step S4. S6. Determine whether the thermal conductivity error under the current aspect ratio is negligible. If yes, proceed to step S7; otherwise, proceed to step S8. S7. Calculate and determine the exhaust port size of the stagnation chamber of the total temperature probe based on the gas continuity equation; S8. Continue to increase the aspect ratio of the filaments immersed in the measured airflow to make it meet the condition that the thermal conductivity error is negligible.

[0017] like Figure 2 , 3As shown in Figure 4, the multi-point total temperature test probe for the main flow of the turbine engine is mainly composed of a total temperature probe support and multiple total temperature test probes. The total temperature test probes include a stagnation chamber, thermocouple wires, and insulators.

[0018] The relevant parameters of the total temperature test probe include the stagnation chamber inlet size. D in Regulation chamber outlet size D out Effective length of stagnation chamber L Thermocouple wire diameter d Diameter of the hot junction of the even wire D Length of thermocouple wire immersed in airflow l Distance from the hot junction of the even wire to the entrance of the stagnation chamber S， Total temperature of the main airflow under test T t Mach number of free flow in the mainstream channel M ∞ Mach number of stagnant airflow inside the stagnant room M j (Convert airflow velocity) u j Stabilizing indoor wall temperature T w Total temperature probe thermocouple cold junction temperature T b .

[0019] The formula for calculating the total temperature measurement speed error is: in, u j To stagnate the airflow velocity inside the room r 裸 The root is the thermal coefficient of the thermocouple wire junction, which is generally taken as 0.86±0.09 when the wire and the airflow are parallel. c p The isobaric specific heat of the airflow is determined based on the static temperature of the airflow. T Sure; The formula for calculating radiation error is: in, T j The total temperature of the airflow being measured. ε The emissivity of the thermocouple measuring end is determined by the thermocouple wire material; c 0 represents the absolute blackbody radiation coefficient, taken as 5.699 W / (m²). 2. K 4 ); B For coefficients, m As an exponent, when the thermocouple wire and the airflow are parallel.B =0.0845, m =0.674; D For qualitative dimensions, the diameter of the hot junction of the ferrite wire is taken; the airflow thermal conductivity is also considered. λ f and kinematic viscosity coefficient ν Determined based on the total temperature of the measured airflow in the criterion equation; T w The temperature of the stagnation chamber wall can be approximated as ( ). T j + T ) / 2, T For airflow static temperature; The formula for calculating thermal conductivity error is: in, T b The temperature of the cold junction of the thermocouple on the total temperature probe (distance from the hot junction) l (temperature at the location) l / d The aspect ratio of the thermocouple wire immersed in the airflow. λ m and α l These are the thermal conductivity and surface heat transfer coefficient of the thermocouple, respectively, both of which are determined by the thermocouple material.

[0020] In step S3, the aspect ratio of the thermocouple wire in the immersion airflow in the stagnation chamber is l / d≮10, and the thermal conductivity error ΔTc≤e, where e is a constant; Formula for calculating the total error of total temperature measurement: Δ T =Δ T v + Δ T r ,Right now: .

[0021] In step S4, let ∂(ΔT) / ∂(u) j With )=0, the formula for calculating the optimal stagnation velocity of airflow inside the stagnation chamber can be obtained: , The formulas for calculating the optimal stagnation velocity and the corresponding Mach number of the stagnation airflow inside the stagnation chamber are as follows: Where k is the adiabatic index of air, taken as 1.4; and R is the gas constant of air, taken as 287.06 J / (kg·K).

[0022] Step S8 also requires determining the length of the stagnation chamber based on the length of the ferrule and the requirement that the distance between the ferrule's hot junction and the stagnation chamber inlet should be greater than the diameter of the ferrule's hot junction.

[0023] Formula for calculating the gas continuity equation: in, F in and F out These are the inlet and outlet areas of the stagnation chamber, respectively. q ( ​ ∞ )and q ( ​ j佳 The free-flow Mach numbers of the main channel airflow are respectively... M ∞ Optimal Mach number for stagnant airflow inside the stagnant chamber M j佳 The corresponding aerodynamic function; Formula for calculating the exhaust port size of the total temperature probe stagnation chamber: in, n This refers to the number of exhaust vents in the stagnation chamber. Generally, 2 to 4 are used.

[0024] Compared with the prior art, the present invention has the following advantages: Based on the aerodynamic parameters of the specific test environment of the total temperature probe, and with the goal of minimizing the comprehensive test error of the airflow total temperature, the detailed structural parameters of the total temperature probe are precisely designed, which greatly improves the design efficiency and test performance of the total temperature probe.

[0025] This addresses the technical deficiency of existing gas turbine engine testing probes that cannot be designed with the optimal structure based on the aerodynamic state of the measured airflow to minimize the overall airflow temperature measurement error.

[0026] The foregoing has provided a detailed description of the design method for a gas turbine engine airflow total temperature test probe provided in this application. The specific embodiments described are merely for the purpose of helping to understand the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A design method for a gas turbine engine airflow total temperature test probe, characterized in that, Including the following steps: S1. Collect relevant parameters from the gas turbine engine's main flow airflow and total temperature test probe; S2. Calculate the total temperature measurement speed error, radiation error, and thermal conductivity error based on the relevant parameters collected from the total temperature test probe. S3. Structurally ensure the aspect ratio of the thermocouple wires in the immersion airflow in the stagnation chamber, ignore thermal conductivity error, and calculate the total error of the total temperature measurement. S4. Calculate the partial derivative of the total error of the total temperature measurement with respect to the stagnation velocity of the airflow inside the stagnation chamber, and obtain the optimal stagnation velocity of the airflow inside the stagnation chamber and the corresponding Mach number of the stagnation airflow. S5. Recalculate the total temperature measurement thermal conductivity error in step S2 using the optimal airflow stagnation velocity inside the stagnation chamber obtained in step S4. S6. Determine whether the thermal conductivity error under the current aspect ratio is negligible. If yes, proceed to step S7; otherwise, proceed to step S8. S7. Calculate and determine the exhaust port size of the stagnation chamber of the total temperature probe based on the gas continuity equation; S8. Continue to increase the aspect ratio of the filaments immersed in the measured airflow to make the thermal conductivity error negligible.

2. The design method for a gas turbine engine airflow total temperature test probe according to claim 1, characterized in that, The total temperature test probe consists of a stagnation chamber, thermocouple wires, and an insulator; The relevant parameters of the total temperature test probe include the stagnation chamber inlet size. D in stagnation chamber outlet size D out Effective length of stagnation chamber L Thermocouple wire diameter d Diameter of the hot junction of the even wire D Length of thermocouple wire immersed in airflow l Distance from the hot junction of the even wire to the entrance of the stagnation chamber S， Total temperature of the main airflow under test T t Mach number of free flow in the mainstream channel M ∞ Mach number of stagnant airflow inside the stagnant room M j Stagnant indoor wall temperature T w Total temperature probe thermocouple cold junction temperature T b .

3. The design method for a gas turbine engine airflow total temperature test probe according to claim 2, characterized in that, The formula for calculating the total temperature measurement speed error is: ， in, u j To slow down the airflow velocity inside the room, r 裸 The root is the thermal compressibility coefficient of the thermocouple wire junction. c p The specific heat at constant pressure of the airflow; The formula for calculating radiation error is: ， in, T j The total temperature of the airflow being measured. ε For thermocouple junction emissivity measurement, c 0 represents the absolute blackbody radiation coefficient. B For coefficients, m For the index, D The diameter of the hot junction of the even wire; λ f airflow thermal conductivity ,ν kinematic viscosity coefficient T w The temperature of the stagnation chamber wall; The formula for calculating thermal conductivity error is: ， in, T b This refers to the cold junction temperature of the thermocouple on the total temperature probe. l / d The aspect ratio of the thermocouple wire immersed in the airflow. λ m and α l These are the thermal conductivity and surface heat transfer coefficient of the thermocouple, respectively.

4. The design method for a gas turbine engine airflow total temperature test probe according to claim 3, characterized in that, In step S3, the aspect ratio of the thermocouple wire in the immersion airflow in the stagnation chamber is l / d≮10, and the thermal conductivity error ΔTc≤e, where e is a constant; Formula for calculating the total error of total temperature measurement: Δ T =Δ T v + Δ T r ,Right now: 。 5. The design method for a gas turbine engine airflow total temperature test probe according to claim 4, characterized in that, In step S4, let ∂(ΔT) / ∂(u) j With )=0, the formula for calculating the optimal stagnation velocity of airflow inside the stagnation chamber can be obtained: ， The formulas for calculating the optimal stagnation velocity and the corresponding Mach number of the stagnation airflow inside the stagnation chamber are as follows: ， Where k is the adiabatic index of air, and R is the gas constant of air. T It is a static temperature for airflow.

6. The design method for a gas turbine engine airflow total temperature test probe according to claim 5, characterized in that, Step S8 also requires determining the length of the stagnation chamber based on the length of the ferrule and the requirement that the distance between the ferrule's hot junction and the stagnation chamber inlet should be greater than the diameter of the ferrule's hot junction.

7. The design method for a gas turbine engine airflow total temperature test probe according to claim 6, characterized in that, Formula for calculating the gas continuity equation: ， in, F in and F out These are the inlet and outlet areas of the stagnation chamber, respectively. q ( λ ∞ )and q ( λ j佳 The free-flow Mach numbers of the main channel airflow are respectively... M ∞ Optimal Mach number for stagnant airflow inside the stagnant chamber M j佳 The corresponding aerodynamic function; Formula for calculating the exhaust port size of the total temperature probe stagnation chamber: ， in, n This represents the number of exhaust vents in the stagnation chamber.

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