A method for determining the starter disengagement conditions of a turboshaft engine

Abstract

The present invention discloses a method for determining the disengagement condition of a turboshaft engine starter, which belongs to the technical field of aeroengines. The method comprises the following steps: S1, determining the rotor acceleration rate after the starter is disengaged; S2, establishing a mathematical model after the starter is disengaged; S3, preliminarily determining the gas generator speed range (n min ,n max ); S4, determine the gas temperature according to the mathematical model of the starting process established in step S2; S5, preliminarily determine the starter disengagement condition according to the result of step S4; S6, correct the gas temperature according to the engine starting test verification; S7, determine whether to adjust the gas generator speed range (n min ,n max ) is adjusted, if adjusted, then steps S4 to S6 are repeated; S8, finally determining the starter disengagement condition. The present invention introduces two control factors, the gas generator speed and the gas temperature, which can improve the start success rate and extend the service life of the starter.

Description

Technical Field

[0001] The present invention relates to the technical field of aeroengines, and in particular to a method for determining a disengagement condition of a turboshaft engine starter. Background Art

[0002] The turboshaft engine starting process usually includes three stages (see Appendix Figure 1 As shown, attached Figure 1 Where M represents torque, n represents the engine gas generator speed, M st is the starter torque, M t is the engine turbine torque, M c is the torque required by the compressor and friction. n1 is the speed of the gas generator when the combustion chamber is ignited, n2 is the speed of the gas generator when the starter is disengaged, n idle is the gas generator speed in the slow-running state, n1' represents the gas generator speed when the turbine torque is equal to the compressor and friction demand torque): In the I stage, the starter drives the engine alone to overcome the compressor demand torque and friction torque, and the state increases; In the II stage, fuel is supplied, the combustion chamber is ignited, the turbine starts to work, and drives the engine together with the starter, and the state continues to increase; In the III stage, the starter is disengaged, and the engine is driven by the turbine alone to continue to accelerate to the slow-running state.

[0003] From the instruction manual Figure 1 It can be seen that when the starter is disengaged, the engine turbine torque M t Greater than the compressor and friction torque M c , the engine can accelerate to the slow state. If the gas generator speed is too low when the starter is disengaged, that is, M t -M c Small, which may lead to long starting time, M t -M c If it is less than or equal to 0, it is easy to cause "cold suspension" (i.e. the engine speed does not increase at low gas turbine temperature) or start failure; if the gas generator speed is too high when the starter is disengaged, it is not conducive to the life of the starter, and the starter's ability to carry the engine is also reduced as the speed increases (such as Figure 1 Medium st curve), the torque it can provide is also limited. Therefore, when the starter is disengaged is critical.

[0004] As for the starter disengagement conditions, existing schemes generally have fixed belt rotation time or fixed belt rotation speed or a combination of the two, such as "starter disengagement when the belt rotates for 30 seconds", "starter disengagement when the gas generator speed reaches 50%, "starter disengagement when either the belt rotates for 30 seconds or the gas generator speed reaches 50%, the specific time or speed is determined through experimental verification in the development stage.

[0005] The prior art has the following disadvantages:

[0006] (1) A fixed spin-up time or spin-up speed may not necessarily ensure that the engine turbine torque M t Greater than the compressor and friction torque M c , and there is a certain difference, such as reduced starter rotation capacity, combustion chamber ignition delay, etc. If the time is fixed, it will cause the gas generator speed to be lower when the starter is disengaged, M t -M c The smaller the engine speed, the longer the start time or even the failure to start. If the gas temperature is low, the engine turbine torque will decrease according to the principle of aircraft engines, which will also cause the M t -M c Smaller;

[0007] (2) If the gas generator speed is too high when the fixed starter is disengaged, it will be detrimental to the life of the starter. As the speed increases, the starter's ability to carry the engine will also decrease, and the torque it can provide will also be limited, wasting the life of the starter. Summary of the invention

[0008] The object of the present invention is to provide a method for determining the disengagement condition of a turboshaft engine starter in view of the above problems. t The size of is mainly related to the gas generator speed and gas temperature. Therefore, the technical solution of the present invention mainly introduces two control factors, namely, the gas generator speed and gas temperature. When the gas generator speed and gas temperature meet the given conditions at the same time, the starter is disengaged to ensure that the engine turbine torque M t Greater than the compressor and friction torque M c , and have a certain difference, so that the engine can start smoothly.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is: a method for determining the disengagement condition of a turboshaft engine starter, comprising the following steps:

[0010] S1. Determine the rotor acceleration rate after the starter is disengaged, including the acceleration rate of the gas generator rotor and the power turbine rotor;

[0011] S2. Establishing a mathematical model after the starter is disengaged: Based on the acceleration rates of the gas generator rotor and the power turbine rotor after the starter is disengaged determined in step S1, combined with the flow balance of the inlet and outlet sections of the engine combustion chamber, the gas turbine and the power turbine and the dynamic balance of the two rotors, a mathematical model of the engine working together is established to determine the performance parameters of the engine after the starter is disengaged;

[0012] S3. Preliminary determination of the gas generator speed range (n min ,n max );

[0013] S4, according to the mathematical model of the starting process established in step S2, determine the starter disengagement speed range (n min ,n max ), the gas temperature after the starter is disconnected at different gas generator speeds;

[0014] S5. According to the result of step S4, the starter disengagement condition is preliminarily determined, that is, when the gas generator speed is (n min ,n max ) range and the gas temperature reaches the value determined in step S4, the starter is disengaged, or the gas generator speed reaches n max The starter is disengaged.

[0015] Furthermore, the method for determining the turboshaft engine starter disengagement condition also includes:

[0016] S6. Based on the engine starting test verification, the gas temperature after the starter is disengaged at different gas generator speeds is corrected;

[0017] S7. According to the engine starting test verification results, determine whether to disconnect the starter speed range, that is, the gas generator speed range (n min ,n max ) is adjusted, if adjusted, repeating steps S4 to S6;

[0018] S8, finally determine the starter disengagement condition, that is, when the gas generator speed is (n min ,n max ) range, and the gas temperature reaches the value corrected in step S6, the starter is disengaged; or the gas generator speed reaches n max , the starter is disengaged.

[0019] Furthermore, in step S1, the gas generator rotor acceleration rate and the power turbine rotor acceleration rate are determined according to the gas generator rotor speed at ground idle state of the engine, the power turbine rotor speed at ground idle state of the engine and the starting time requirement, using the average acceleration rate of the starting process.

[0020] Furthermore, the calculation formulas for the gas generator rotor acceleration rate and the power turbine rotor acceleration rate are shown in Formula 1 and Formula 2 respectively:

[0021]

[0022] Where n0 is the gas generator rotor speed at ground idle state, and t0 is the required starting time of the engine.

[0023]

[0024] Where np0 is the power turbine rotor speed of the engine at ground idle state.

[0025] Furthermore, the mathematical model after the starter is disengaged in step S2 is based on the compressor, gas turbine and power turbine working together, and according to the common working conditions of the aircraft engine, the following five working equations are obtained to calculate the performance parameters of the engine after the starter is disengaged:

[0026] a) Gas flow balance equation for the combustion chamber outlet section and the gas turbine inlet section:

[0027] Wa4 / Wa41-1=0 (3)

[0028] Where Wa4 is the flow rate at the combustion chamber outlet, and Wa41 is the flow rate at the gas turbine inlet;

[0029] b) Gas flow balance equation for gas turbine outlet section and power turbine inlet section:

[0030] Wa44 / Wa45-1=0 (4)

[0031] Where Wa44 is the gas turbine outlet cross-sectional flow rate, Wa45 is the power turbine inlet cross-sectional flow rate;

[0032] c) Gas flow balance equation for power turbine outlet section and tail nozzle outlet section:

[0033] Wa5 / Wa8-1=0 (5)

[0034] Where Wa5 is the flow rate at the power turbine outlet, and Wa8 is the flow rate at the tail nozzle outlet;

[0035] d) Gas generator rotor dynamics equation:

[0036]

[0037] Where N is the power generated by the gas turbine, η is the mechanical efficiency of the gas generator rotor, and N cp is the power consumed by the compressor, N ex is the power extracted from the accessory, J is the moment of inertia of the gas generator rotor, and n is the speed of the gas generator;

[0038] e) Power turbine rotor dynamics equation:

[0039]

[0040] Where Np is the power output of the power turbine, ηp is the mechanical efficiency of the power rotor, and N rex is the power consumed by the load, J p is the moment of inertia of the power turbine rotor, n p is the power turbine speed.

[0041] Furthermore, according to the working principle of the aircraft engine, the compressor operating point is determined by the gas generator speed n and the compressor pressure ratio πcp, the gas turbine operating point is determined by the gas generator speed n and the gas turbine pressure drop ratio πgt, and the power turbine operating point is determined by the power turbine speed n p and the power turbine pressure drop ratio πpt; then, according to formula 1 and formula 2, the gas generator rotor acceleration rate and the power turbine rotor acceleration rate after the starter is disengaged are calculated, and they are substituted into formula 6 and formula 7 respectively, and then the engine common working equation formula 3 to formula 7 form a joint equation group, and the gas generator speed n and the power turbine speed n are solved by the joint equation group. p , compressor pressure ratio πcp, gas turbine pressure drop ratio πgt and power turbine pressure drop ratio πpt, and then determine the compressor operating point, gas turbine operating point and power turbine operating point, and then calculate the temperature and pressure values ​​of each section from the engine inlet to the outlet, and then determine the gas temperature.

[0042] Furthermore, the specific calculation process of the temperature and pressure values ​​of each cross section and the gas temperature is as follows:

[0043] e) Calculation of compressor inlet parameters

[0044]

[0045] Where, T2 is the total temperature at the compressor inlet, T0 is the atmospheric temperature; k1 is the adiabatic index, M is the flight Mach number, P2 is the total pressure at the compressor inlet, P0 is the atmospheric pressure, and σ is the total pressure recovery coefficient of the inlet duct, which is obtained from the inlet duct characteristic diagram;

[0046] f) Compressor outlet air flow parameters

[0047] P3=P2*πcp (10)

[0048]

[0049] Where, T3 is the total temperature at the compressor outlet, P3 is the total pressure at the compressor outlet, k2 is the air specific heat ratio; ηc is the compressor efficiency, which is obtained from the compressor characteristic diagram;

[0050] g) Combustion chamber outlet air flow parameters

[0051] P4=P3*σB (12)

[0052]

[0053] Where T4 is the total temperature at the combustion chamber outlet, P4 is the total pressure at the combustion chamber outlet; and σ B is the total pressure recovery coefficient of the combustion chamber, Wf is the fuel flow rate, ηb is the combustion efficiency, Hu is the lower heating value of the fuel, Cp is the heat capacity of the air, Cpg is the heat capacity of the gas, and W3a is the combustion chamber inlet air flow rate, which can be obtained through the compressor characteristic diagram;

[0054] h) Gas temperature calculation

[0055]

[0056] Where T45 is the gas temperature, kg is the gas specific heat ratio; ηt is the gas turbine efficiency, which is obtained from the gas turbine characteristic diagram.

[0057] Furthermore, the empirical value of the gas generator speed range in which the turboshaft engine starter is disengaged in step S3 is determined to be (40%, 60%) of the design speed.

[0058] Furthermore, in step S4, the gas temperature under the conditions of different intake pressures, intake temperatures and gas generator speed ranges at (40%, 60%) of the design speed is determined.

[0059] Furthermore, the starter disengagement condition preliminarily determined in step S5 is that the starter is disengaged when the gas generator speed is within the range of (40%, 60%) of the design speed and the gas temperature reaches the value determined in step S4, or the starter is disengaged when the gas generator speed reaches 60% of the design speed.

[0060] Furthermore, in step S6, according to the engine starting test verification, the calculation results of the gas temperature under different engine inlet pressures, inlet temperatures and gas generator speed ranges at (40%, 60%) of the design speed are corrected.

[0061] Beneficial effects of the present invention:

[0062] 1. The present invention introduces two control factors, namely, the gas generator speed and the gas temperature. When the gas generator speed and the gas temperature meet the given conditions at the same time (i.e., when the gas generator speed is within (n min ,n max ) range, and the gas temperature reaches the value determined in step S4; or the gas generator speed reaches n max), the starter is disengaged. This ensures that the engine turbine torque Mt is greater than the compressor and friction torque Mc, and has a certain difference, ensuring the engine start success rate and avoiding long start time, cold suspension, and even start failure due to reduced starter rotation capacity, combustion chamber ignition delay, and low gas temperature.

[0063] 2. The method of the present invention can correct the gas temperature after the starter is disengaged at different gas generator speeds, and can also adjust the starter disengagement speed range (i.e., the gas generator speed range) according to the test conditions. min ,n max ) is adjusted to achieve continuous correction and adjustment of the two parameters of gas temperature and gas generator speed, ultimately ensuring that the starter is disengaged in time under the conditions of acceptable acceleration rate of the gas generator rotor after the starter is disengaged, without wasting the starter life.

[0064] Of course, it is not necessary to achieve all the advantages described above at the same time for any product of the present invention to be implemented. In addition to the purposes, features and advantages described above, the present invention also has other purposes, features and advantages. The present invention will be further described in detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0066] Figure 1 is a schematic diagram of the three stages of the existing turboshaft engine starting process;

[0067] Figure 2 It is a method flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The following is combined with Figure 2 While the embodiments of the present invention have been described in detail, the present invention can be implemented in many different ways as defined and covered below.

[0069] A method for determining a turboshaft engine starter disengagement condition comprises the following steps:

[0070] S1. Determine the rotor acceleration rate after the starter is disengaged, including the acceleration rate of the gas generator rotor and the power turbine rotor;

[0071] S2. Establishing a mathematical model after the starter is disengaged: Based on the acceleration rates of the gas generator rotor and the power turbine rotor after the starter is disengaged determined in step S1, combined with the flow balance of the inlet and outlet sections of the engine combustion chamber, the gas turbine and the power turbine and the dynamic balance of the two rotors, a mathematical model of the engine working together is established to determine the performance parameters of the engine after the starter is disengaged;

[0072] S3. Preliminary determination of the gas generator speed range (n min ,n max );

[0073] S4, according to the mathematical model of the starting process established in step S2, determine the starter disengagement speed range (n min ,n max ), the gas temperature after the starter is disconnected at different gas generator speeds;

[0074] S5. According to the result of step S4, the starter disengagement condition is preliminarily determined, that is, when the gas generator speed is (n min ,n max ) range and the gas temperature reaches the value determined in step S4, the starter is disengaged, or the gas generator speed reaches n max The starter is disengaged.

[0075] Optionally, the method for determining a turboshaft engine starter disengagement condition further comprises:

[0076] S6. Based on the engine starting test verification, the gas temperature after the starter is disengaged at different gas generator speeds is corrected;

[0077] S7. According to the engine starting test verification results, determine whether to disconnect the starter speed range, that is, the gas generator speed range (n min ,n max ) is adjusted, if adjusted, repeating steps S4 to S6;

[0078] S8, finally determine the starter disengagement condition, that is, when the gas generator speed is (n min ,n max ) range, and the gas temperature reaches the value corrected in step S6, the starter is disengaged; or the gas generator speed reaches n max , the starter is disengaged.

[0079] It can be understood that by introducing the two control factors of gas generator speed and gas temperature, when the gas generator speed and gas temperature meet the given conditions at the same time (that is, when the gas generator speed is within (n min ,n max) range, and the gas temperature reaches the value determined in step S4; or the gas generator speed reaches n max ), the starter is disengaged. This ensures that the engine turbine torque Mt is greater than the compressor and friction torque Mc, and has a certain difference, ensuring the engine start success rate and avoiding long start time, cold suspension, and even start failure due to reduced starter rotation capacity, combustion chamber ignition delay, and low gas temperature.

[0080] At the same time, the present invention can correct the gas temperature after the starter is disengaged at different gas generator speeds, and can adjust the starter disengagement speed range, that is, the gas generator speed range (n min ,n max ) is adjusted to achieve continuous correction and adjustment of the two parameters of gas temperature and gas generator speed, ultimately ensuring that the starter is disengaged in time under the conditions of acceptable acceleration rate of the gas generator rotor after the starter is disengaged, without wasting the starter life.

[0081] Preferably, in step S1, the gas generator rotor acceleration rate and the power turbine rotor acceleration rate are determined according to the gas generator rotor speed in the engine ground slow state, the power turbine rotor speed in the engine ground slow state and the starting time requirement, using the average acceleration rate of the starting process.

[0082] It should be noted that the average acceleration rate of the starting process is used to determine the gas generator rotor acceleration rate and the power turbine rotor acceleration rate. It is the average value verified by multiple actual tests and belongs to the category of empirical values. It can meet the gas generator rotor speed, power turbine rotor speed and starting time requirements in the engine's ground idle state.

[0083] Specifically, the calculation formulas for the gas generator rotor acceleration rate and the power turbine rotor acceleration rate are shown in Formula 1 and Formula 2, respectively:

[0084]

[0085] Where n0 is the gas generator rotor speed at ground idle state, and t0 is the required starting time of the engine.

[0086]

[0087] Where np0 is the power turbine rotor speed of the engine at ground idle state.

[0088] Preferably, the mathematical model after the starter is disengaged in step S2 is based on the compressor, gas turbine and power turbine working together, and the following five working equations are obtained according to the common working conditions of the aircraft engine to calculate the performance parameters of the engine after the starter is disengaged:

[0089] a) Gas flow balance equation for the combustion chamber outlet section and the gas turbine inlet section:

[0090] Wa4 / Wa41-1=0 (3)

[0091] Where Wa4 is the flow rate at the combustion chamber outlet, and Wa41 is the flow rate at the gas turbine inlet;

[0092] b) Gas flow balance equation for gas turbine outlet section and power turbine inlet section:

[0093] Wa44 / Wa45-1=0 (4)

[0094] Where Wa44 is the gas turbine outlet cross-sectional flow rate, Wa45 is the power turbine inlet cross-sectional flow rate;

[0095] c) Gas flow balance equation for power turbine outlet section and tail nozzle outlet section:

[0096] Wa5 / Wa8-1=0 (5)

[0097] Where Wa5 is the flow rate at the power turbine outlet, and Wa8 is the flow rate at the tail nozzle outlet;

[0098] d) Gas generator rotor dynamics equation:

[0099]

[0100] Where N is the power generated by the gas turbine, η is the mechanical efficiency of the gas generator rotor, and N cp is the power consumed by the compressor, N ex is the power extracted from the accessory, J is the moment of inertia of the gas generator rotor, and n is the speed of the gas generator;

[0101] e) Power turbine rotor dynamics equation:

[0102]

[0103] Where Np is the power output of the power turbine, ηp is the mechanical efficiency of the power rotor, and N rex is the power consumed by the load, J p is the moment of inertia of the power turbine rotor, n p is the power turbine speed.

[0104] In this preferred embodiment, after the equation group of the mathematical model after the starter is disengaged is established, according to the working principle of the aircraft engine, the compressor operating point is determined by the gas generator speed n and the compressor pressure ratio πcp, the gas turbine operating point is determined by the gas generator speed n and the gas turbine pressure drop ratio πgt, and the power turbine operating point is determined by the power turbine speed n p and the power turbine pressure drop ratio πpt; then, according to formula 1 and formula 2, the gas generator rotor acceleration rate and the power turbine rotor acceleration rate after the starter is disengaged are calculated, and they are substituted into formula 6 and formula 7 respectively, and then the engine common working equation formula 3 to formula 7 form a joint equation group, and the gas generator speed n and the power turbine speed n are solved by the joint equation group. p , compressor pressure ratio πcp, gas turbine pressure drop ratio πgt and power turbine pressure drop ratio πpt, and then determine the compressor operating point, gas turbine operating point and power turbine operating point, and then calculate the temperature and pressure values ​​of each section from the engine inlet to the outlet, and then determine the gas temperature.

[0105] It can be understood that, according to the prior art, the compressor pressure ratio πcp can be calculated by the gas generator speed n, the gas turbine pressure drop ratio πgt can also be calculated by the gas generator speed n, and the power turbine pressure drop ratio πpt can be calculated by the power turbine speed n p By calculating the equations of the mathematical model after the starter is disconnected, the gas generator speed n and the power turbine speed n can be calculated first. p , and then according to the existing technical formula, the compressor pressure ratio πcp, the gas turbine pressure drop ratio πgt and the power turbine pressure drop ratio πpt are calculated. Then, after the compressor operating point, gas turbine operating point and power turbine operating point are determined, the gas temperature can be determined through the temperature and pressure values ​​of each section.

[0106] Specifically, the specific calculation process of the temperature and pressure values ​​of each section and the gas temperature is as follows:

[0107] i) Calculation of compressor inlet parameters

[0108]

[0109] Where, T2 is the total temperature at the compressor inlet, T0 is the atmospheric temperature; k1 is the adiabatic index, M is the flight Mach number, P2 is the total pressure at the compressor inlet, P0 is the atmospheric pressure, and σ is the total pressure recovery coefficient of the inlet duct, which is obtained from the inlet duct characteristic diagram;

[0110] j) Compressor outlet air flow parameters

[0111] P3=P2*πcp (10)

[0112]

[0113] Where, T3 is the total temperature at the compressor outlet, P3 is the total pressure at the compressor outlet, k2 is the air specific heat ratio; ηc is the compressor efficiency, which is obtained from the compressor characteristic diagram;

[0114] k) Combustion chamber outlet air flow parameters

[0115] P4=P3*σ B (12)

[0116]

[0117] Where T4 is the total temperature at the combustion chamber outlet, P4 is the total pressure at the combustion chamber outlet; and σ B is the total pressure recovery coefficient of the combustion chamber, Wf is the fuel flow rate, ηb is the combustion efficiency, Hu is the lower heating value of the fuel, Cp is the heat capacity of the air, Cpg is the heat capacity of the gas, and W3a is the combustion chamber inlet air flow rate, which can be obtained through the compressor characteristic diagram;

[0118] l) Gas temperature calculation

[0119]

[0120] Where T45 is the gas temperature, kg is the gas specific heat ratio; ηt is the gas turbine efficiency, which is obtained from the gas turbine characteristic diagram.

[0121] Preferably, the empirical value of the gas generator speed range in which the turboshaft engine starter is disengaged in step S3 is determined to be (40%, 60%) of the design speed.

[0122] It should be noted that the design speed (40%, 60%) is a relatively wide empirical value, and will be gradually adjusted to a more accurate range value according to the test verification results to improve the validity of the data.

[0123] In the preferred embodiment, the step S4 determines the gas temperature under the conditions of different intake pressures, intake temperatures and gas generator speed ranges within (40%, 60%) of the design speed.

[0124] It should be noted that the gas generator speed range for turboshaft engine starter disengagement is first determined based on empirical values, and the starter disengagement conditions are preliminarily determined in combination with the calculated gas temperature. Finally, based on the engine starting test verification results, the gas generator speed range is adjusted, and the gas temperature is repeatedly calculated to correct it, ultimately obtaining more accurate starter disengagement conditions.

[0125] In this preferred embodiment, the starter disengagement condition preliminarily determined in step S5 is that the starter is disengaged when the gas generator speed is within the range of (40%, 60%) of the design speed and the gas temperature reaches the value determined in step S4, or the starter is disengaged when the gas generator speed reaches 60% of the design speed.

[0126] In this preferred embodiment, in step S6, the calculation results of the gas temperature under different engine inlet pressures, inlet temperatures and gas generator speed ranges at the design speed (40%, 60%) are corrected according to the engine starting test verification results.

[0127] It should be noted that, since the starter disengagement needs to simultaneously meet the restriction conditions specified by the two control factors of the gas generator speed and the gas temperature (that is, the gas generator speed is within the preset range and the gas temperature reaches the calculated corrected value; or the gas generator speed reaches the maximum value of the preset range), the gas temperature is corrected first. During the correction process, the gas generator speed range is adjusted according to the engine starting test verification results (whether the engine starting success rate and other requirements are met), which is equivalent to cyclically adjusting the two parameters of the gas generator speed and the gas temperature, so that the starter disengagement condition can be finally determined, and the adjustment efficiency is more efficient, which is ultimately beneficial to improving the starting success rate and extending the service life of the starter.

[0128] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0129] The principles and implementation methods of the present invention are explained herein. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for determining a turboshaft engine starter disengagement condition, characterized in that: The following steps are involved: S1. Determine the rotor acceleration rate after the starter is disengaged, including the acceleration rate of the gas generator rotor and the power turbine rotor; S2. Establishing a mathematical model after the starter is disengaged: Based on the acceleration rates of the gas generator rotor and the power turbine rotor after the starter is disengaged determined in step S1, combined with the flow balance of the inlet and outlet cross sections of the engine combustion chamber, the gas turbine and the power turbine and the dynamic balance of the two rotors, a mathematical model of the engine after the starter is disengaged is established to determine the performance parameters of the engine after the starter is disengaged; S3. Preliminary determination of the gas generator speed range (n min ,n max ); S4, according to the mathematical model after the starter is disengaged established in step S2, determine the gas generator speed range (n min ,n max ), the gas temperature after the starter is disconnected at different gas generator speeds; S5. According to the result of step S4, the starter disengagement condition is preliminarily determined, that is, when the gas generator speed is (n min ,n max ) range and the gas temperature reaches the value determined in step S4, the starter is disengaged, or the gas generator speed reaches n max The starter is disengaged; The mathematical model after the starter is disengaged in step S2 is based on the compressor, gas turbine and power turbine working together, and according to the common working conditions of the aircraft engine, the following five working equations are obtained to calculate the performance parameters of the engine after the starter is disengaged: a) Gas flow balance equation for the combustion chamber outlet section and the gas turbine inlet section: Wa4 / Wa41-1=0 (3) Where Wa4 is the flow rate at the combustion chamber outlet, and Wa41 is the flow rate at the gas turbine inlet; b) Gas flow balance equation for gas turbine outlet section and power turbine inlet section: Wa44 / Wa45-1=0 (4) Where Wa44 is the gas turbine outlet cross-sectional flow rate, Wa45 is the power turbine inlet cross-sectional flow rate; c) Gas flow balance equation for power turbine outlet section and tail nozzle outlet section: Wa5 / Wa8-1=0 (5) Where Wa5 is the flow rate at the power turbine outlet, and Wa8 is the flow rate at the tail nozzle outlet; d) Gas generator rotor dynamics equation: Where dn / dt is the gas generator rotor acceleration rate, N is the power output of the gas turbine, η is the gas generator rotor mechanical efficiency, N cp is the power consumed by the compressor, N ex is the power extracted from the accessory, J is the moment of inertia of the gas generator rotor, and n is the speed of the gas generator; e) Power turbine rotor dynamics equation: Where, dnp / dt is the acceleration rate of the power turbine rotor, np is the power turbine speed, N p The power turbine generates power, η p is the mechanical efficiency of the power rotor, N rex is the power consumed by the load, J p is the moment of inertia of the power turbine rotor.

2. A method for determining a turboshaft engine starter disengagement condition according to claim 1, characterized in that: The method for determining a turboshaft engine starter disengagement condition further comprises: S6. Based on the engine starting test verification, the gas temperature after the starter is disengaged at different gas generator speeds is corrected; S7. According to the engine starting test verification results, determine whether to disconnect the starter speed range, that is, the gas generator speed range (n min ,n max ) is adjusted, if adjusted, repeating steps S4 to S6; S8, finally determine the starter disengagement condition, that is, when the gas generator speed is (n min ,n max ) range, and the gas temperature reaches the value corrected in step S6, the starter is disengaged; or the gas generator speed reaches n max , the starter is disengaged.

3. A method for determining a turboshaft engine starter disengagement condition according to claim 1, characterized in that: In step S1, the gas generator rotor acceleration rate and the power turbine rotor acceleration rate are determined according to the engine ground slow state gas generator speed, the engine ground slow state power turbine speed and the starting time requirement, using the average acceleration rate of the starting process.

4. A method for determining a turboshaft engine starter disengagement condition according to claim 3, characterized in that: The calculation formulas for the gas generator rotor acceleration rate dn / dt and the power turbine rotor acceleration rate dnp / dt are shown in formula (1) and formula (2), respectively: Where n0 is the gas generator speed at ground slow speed, and t0 is the required start time of the engine; Where np0 is the power turbine speed of the engine at ground idle state.

5. A method for determining a turboshaft engine starter disengagement condition according to claim 4, characterized in that: According to the working principle of aircraft engines, the compressor operating point is determined by the gas generator speed n and the compressor pressure ratio πcp, the gas turbine operating point is determined by the gas generator speed n and the gas turbine pressure drop ratio πgt, and the power turbine operating point is determined by the power turbine speed np and the power turbine pressure drop ratio πpt; then, according to formula (1) and formula (2), the gas generator rotor acceleration rate and the power turbine rotor acceleration rate after the starter is disengaged are calculated, and substituted into formula (6) and formula (7) respectively, and then the engine common working equation formula (3) to formula (7) form a joint equation group, and the gas generator speed n, the power turbine speed np, the compressor pressure ratio πcp, the gas turbine pressure drop ratio πgt and the power turbine pressure drop ratio πpt are solved by the joint equation group, and then the compressor operating point, the gas turbine operating point and the power turbine operating point are determined, and then the temperature and pressure values ​​of each section from the engine inlet to the outlet are calculated in turn to determine the gas temperature.

6. A method for determining a turboshaft engine starter disengagement condition according to claim 5, characterized in that: The specific calculation process of the temperature and pressure values ​​of each section and the gas temperature is as follows: a) Calculation of compressor inlet parameters Where, T2 is the total temperature at the compressor inlet, T0 is the atmospheric temperature; k1 is the adiabatic index, M is the flight Mach number, P2 is the total pressure at the compressor inlet, P0 is the atmospheric pressure, and σ is the total pressure recovery coefficient of the inlet duct, which is obtained from the inlet duct characteristic diagram; b) Compressor outlet air flow parameters P3=P2*πcp (10) Where T3 is the total temperature at the compressor outlet, P3 is the total pressure at the compressor outlet, k2 is the air specific heat ratio, and ηc is the compressor efficiency, which is obtained from the compressor characteristic diagram; c) Combustion chamber outlet air flow parameters P4=P3*σ B (12) Where T4 is the total temperature at the combustion chamber outlet, P4 is the total pressure at the combustion chamber outlet; and σ B is the total pressure recovery coefficient of the combustion chamber, Wf is the fuel flow rate, ηb is the combustion efficiency, Hu is the lower heating value of the fuel, Cp is the heat capacity of the air, Cpg is the heat capacity of the gas, and W3a is the combustion chamber inlet air flow rate, which can be obtained through the compressor characteristic diagram; d) Gas temperature calculation Where T45 is the gas temperature, kg is the gas specific heat ratio, and ηt is the gas turbine efficiency, which is obtained from the gas turbine characteristic diagram.

7. A method for determining a turboshaft engine starter disengagement condition according to claim 1, characterized in that: The empirical value of the gas generator speed range in which the turboshaft engine starter is disengaged in step S3 is determined to be (40%, 60%) of the design speed.

8. A method for determining a turboshaft engine starter disengagement condition according to claim 1, characterized in that: In step S4, the gas temperature under the conditions of different intake pressures, intake temperatures and gas generator speed ranges within (40%, 60%) of the design speed is determined; in step S5, the starter disengagement condition is preliminarily determined as the starter disengagement when the gas generator speed is within the range of (40%, 60%) of the design speed and the gas temperature reaches the value determined in step S4, or the starter disengagement when the gas generator speed reaches 60% of the design speed.

9. A method for determining a turboshaft engine starter disengagement condition according to claim 2, characterized in that: In step S6, according to the engine starting test verification, the calculation results of the gas temperature under different engine intake pressures, intake temperatures and gas generator speed ranges at the design speed (40%, 60%) are corrected.

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