A starter power calculation method considering performance degradation

Abstract

The application belongs to the field of aero-engine design and is a starter power calculation method considering performance attenuation. A corresponding relationship between starter torque and high-pressure turbine torque attenuation is established, and a corresponding relationship between starter output power and starter torque is determined, then the corresponding high-pressure turbine unit attenuation when the high-pressure turbine efficiency drops by 1% is calculated, and the high-pressure turbine efficiency of different high-pressure rotors at different relative physical speeds is calculated through identification, and the engine performance parameters at different high-pressure rotor relative physical speeds below the slow speed at different engine working hours are counted, so as to calculate the high-pressure turbine torque attenuation M D after the corresponding engine working hours, and the corresponding starter torque and output power demand are obtained. The influence of the performance attenuation factor is considered, the power calculation result is more reliable, and the power demand of the starter in the whole life cycle of the engine is met.

Description

Technical Field

[0001] This application belongs to the field of aero-engine design, and specifically relates to a method for calculating starter power considering performance degradation. Background Technology

[0002] Starter power requirement calculation is a crucial technical activity in the design of aero-engine starting performance. The starter power level determines whether the aero-engine can start successfully and directly reflects the starter's rotation capability. Professionally, starter power requirement calculation mainly uses the rotor torque balance equation. By discretizing and solving the equation, the starter power that meets the starting performance requirements is obtained.

[0003] The core idea of ​​the rotor torque balance equation is to solve for the net residual torque, which is the driving torque minus the resistance torque. The driving torque includes the turbine torque and the starter torque, while the resistance torque includes the compressor aerodynamic resistance torque, frictional resistance torque, lubricating oil accessory resistance torque, and resistance torque generated by power extraction. Currently, starter power calculations, due to a lack of design experience and methods, do not consider the impact of performance degradation on the net residual torque. However, engines inevitably experience performance degradation after long-term use. If the impact of performance degradation is not considered, the calculated starter power will be insufficient to meet the starting performance requirements after long-term engine use (such as nearing the first overhaul period), which can easily lead to engine starting failure.

[0004] The drawback of the existing calculation method is that when calculating the starter power using the rotor torque balance equation, the factor of performance degradation is not taken into account, resulting in a lower calculated starter power value, which cannot guarantee the starting performance throughout the engine's entire lifespan.

[0005] Low starter power weakens the starter's ability to turn the engine. While this may not have a significant impact on a newly manufactured engine, over long-term use, engine performance inevitably declines due to factors such as increased turbine blade tip clearance, increased blade surface roughness, and the accumulation of impurities and dirt. This performance degradation directly results in a decrease in the turbine's work capacity, leading to reduced turbine torque. Furthermore, as engine usage time increases or performance degradation deepens, the engine's net residual torque further decreases. Low starter power hinders rotor acceleration, increasing the probability of start-up failure. If the engine experiences an in-flight shutdown after installation, it will be difficult to restart in the air, posing a threat to the safety of the aircraft and pilot.

[0006] To this end, this patent proposes a starter power calculation method that takes into account performance degradation factors, ensuring that the engine still has a high starting success rate after long-term use. Summary of the Invention

[0007] The purpose of this application is to provide a starter power calculation method that takes into account performance degradation, so as to solve the problem that existing engine aerodynamic power calculations do not take into account engine performance degradation, which makes engine starting prone to failure.

[0008] The technical solution of this application is: a method for calculating starter power considering performance degradation, comprising:

[0009] The relationship between starter torque and high-pressure turbine torque attenuation is established based on the rotor torque balance equation, and the relationship between starter output power and starter torque is determined.

[0010] Based on the low-speed characteristics of rotating components and the overall engine performance calculation theory using extrapolation correction, the unit attenuation ΔM of the high-pressure turbine is calculated when the high-pressure turbine efficiency decreases by 1%. T ;

[0011] Before the engine leaves the factory, engine performance parameters at different high-pressure rotor relative physical speeds below idle are recorded. The high-pressure turbine efficiency at different high-pressure rotor relative physical speeds is identified and calculated. At the same time, engine performance parameters at different high-pressure rotor relative physical speeds below idle are statistically analyzed at different engine operating hours, and the corresponding high-pressure turbine efficiency reduction Δη is identified and calculated. T ;

[0012] Calculate the amount of high-pressure turbine torque reduction M caused by performance degradation after the corresponding engine has been operating for a certain number of hours. D Then, by substituting this into the rotor torque balance equation, the corresponding starter torque and output power requirements are calculated.

[0013] Preferably, the method for calculating the unit attenuation of the high-pressure turbine when the high-pressure turbine efficiency decreases by 1% is as follows:

[0014] Calculate the unit attenuation ΔM of the high-pressure turbine corresponding to different relative physical speeds of the high-pressure rotor above engine ignition speed and below idle speed. T For different high-voltage rotor relative physical speeds n H The high-pressure turbine unit attenuation and the relative physical speed n of the high-pressure rotor are obtained by sorting from low to high and fitting the data. H The functional expression between ΔM T =f(n) H ).

[0015] Preferably, the relative physical speed of the high-pressure rotor includes ignition speed, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and idle speed.

[0016] Preferably, the method for calculating the decrease in high-pressure turbine efficiency is as follows:

[0017] Based on the performance parameters corresponding to different engine speeds below idle speed, the turbine efficiency η corresponding to different engine speeds before delivery is identified and calculated. T,基准 As a benchmark efficiency:

[0018] η T,基准 =f(n) H ,F,T6,sfc)

[0019] In the formula, n H Where is the relative physical speed of the high-pressure rotor, F is the engine thrust, T6 is the engine temperature, and sfc is the engine fuel consumption rate.

[0020] Then, the engine performance parameters at different speeds below idle after the engine has been working for a specified time are statistically analyzed. The turbine efficiency of the engine after working for a specified time is obtained by identification and calculation. At the same time, the corresponding turbine efficiency after the engine has been working for other set times is also identified and calculated.

[0021] Subtracting the turbine efficiency, identified after a certain period of engine operation, from the baseline efficiency yields the decrease in turbine efficiency after a certain period of engine operation. This is represented by the relative physical speed n of the high-pressure rotor. H Turbine efficiency decrease Δη corresponding to operating hours T Obtained through the difference.

[0022] Preferably, after the engine has been running for a certain number of hours, the high-pressure turbine torque reduction M due to performance degradation is... D for:

[0023] M D =ΔM T ×Δη T .

[0024] This application provides a starter power calculation method considering performance degradation. First, it establishes a correspondence between starter torque and high-pressure turbine torque degradation, and determines the correspondence between starter output power and starter torque. Then, it calculates the unit degradation of the high-pressure turbine when the engine's high-pressure turbine efficiency decreases by 1%. Next, it identifies and calculates the high-pressure turbine efficiency at different relative physical speeds of the high-pressure rotor. Simultaneously, it statistically analyzes engine performance parameters at different high-pressure rotor relative physical speeds below idle speed during different engine operating hours, identifying and calculating the corresponding high-pressure turbine efficiency reduction Δη. T This allows for the calculation of the high-pressure turbine torque reduction M caused by performance degradation after the corresponding engine has been operating for a certain number of hours. D This yields the corresponding starter torque and output power requirements. The impact of performance degradation is considered, making the power calculation results more reliable and meeting the starter power requirements throughout the engine's entire lifespan. Attached Figure Description

[0025] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0026] Figure 1 This is a schematic diagram of the overall process of this application;

[0027] Figure 2 This is a schematic diagram showing the relationship between the high-pressure turbine torque attenuation and rotational speed corresponding to a 1% decrease in turbine efficiency in this application.

[0028] Figure 3 This is a schematic diagram showing the decrease in turbine efficiency under different operating hours and different speeds in this application. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] A method for calculating starter power that takes performance degradation into account, such as Figure 1 As shown, it includes the following steps:

[0031] Step S100: Establish the correspondence between starter output power and torque, and between starter torque and high-pressure turbine torque attenuation.

[0032] First, establish the correspondence between the starter torque and the high-pressure turbine torque attenuation based on the rotor torque balance equation. According to the torque balance equation, the left side of the equation represents the net residual torque, and the right side represents the rate of increase in speed and the moment of inertia of the high-pressure rotor.

[0033]

[0034] Where: M ST —Starter torque (N·m), M T — Turbo torque (N·m), M C — Compressor aerodynamic drag torque (N·m), M Z —Frictional resistance torque (N·m), M F —Lubricating oil accessory resistance torque (N·m), M P —Drag torque (N·m), M generated by power extraction D — Torque reduction of the high-pressure turbine due to performance degradation (N·m), J — Rotor moment of inertia (kg·m) 2 ), n H— Physical speed of the high-pressure rotor of the engine (r / min), t — starting time (s).

[0035] In the rotor torque balance equation, apart from the starter torque and the high-pressure turbine torque attenuation, all other parameters can be directly collected during engine operation or calculated directly using the collected parameters through existing formulas. In other words, using this equation, as long as the high-pressure turbine torque attenuation is obtained, the starter torque can be directly calculated.

[0036] Then, the corresponding relationship between the starter motor output power and the starter motor torque is determined, specifically:

[0037]

[0038] In the above formula: p ST —Starter motor output power (kW), n ST —Starter motor physical speed (r / min).

[0039] The physical speed of the starter can be directly obtained, so as long as the torque of the starter is obtained, the output power of the starter can be directly calculated using this formula.

[0040] By establishing the above correspondence, we only need to obtain the torque attenuation of the high-pressure turbine to obtain the starter power and output torque considering the performance degradation, without needing to perform any other calculations, which is efficient and fast.

[0041] Step S200: Set and calculate the unit attenuation of the high-pressure turbine.

[0042] Based on the low-speed characteristics of rotating components and the overall engine performance calculation theory using extrapolation correction, the unit attenuation ΔM of the high-pressure turbine is calculated when the high-pressure turbine efficiency decreases by 1%. T ;

[0043] Preferably, the specific calculation method is as follows:

[0044] like Figure 2 As shown, calculate the unit attenuation ΔM of the high-pressure turbine corresponding to different relative physical speeds of the high-pressure rotor above the engine ignition speed and below the idle speed. T For different high-voltage rotor relative physical speeds n H The high-pressure turbine unit attenuation and the relative physical speed n of the high-pressure rotor are obtained by sorting from low to high and fitting the data. H Function expressions between:

[0045] ΔM T =f(n) H (3)

[0046] The relative physical speeds of the high-voltage rotor include ignition speed, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and idle speed.

[0047] By setting and calculating the unit attenuation of the high-pressure turbine, the torque attenuation of the high-pressure turbine can be directly obtained by multiplying the actual decrease in high-pressure turbine efficiency by the unit attenuation of the high-pressure turbine. The calculation is simple and accurate.

[0048] Step S300, Calculation of high-pressure turbine efficiency reduction

[0049] Before the engine leaves the factory, engine performance parameters at different high-pressure rotor relative physical speeds below idle are recorded. The high-pressure turbine efficiency at different high-pressure rotor relative physical speeds is identified and calculated. At the same time, engine performance parameters at different high-pressure rotor relative physical speeds below idle are statistically analyzed at different engine operating hours, and the corresponding high-pressure turbine efficiency reduction Δη is identified and calculated. T .

[0050] Preferably, the method for calculating the decrease in high-pressure turbine efficiency is as follows:

[0051] Step S310: Based on the performance parameters corresponding to different engine speeds below idle speed, identify and calculate the turbine efficiency η corresponding to different engine speeds before delivery. T,基准 As a benchmark efficiency:

[0052] η T,基准 =f(n) H (4)

[0053] In the formula, n H is the relative physical speed of the high-pressure rotor, F is the engine thrust, T6 is the engine temperature, and sfc is the engine fuel consumption rate.

[0054] Step S320: Then, after the engine has been running for a specified time (set to 100 hours), the engine performance parameters at different speeds below idle are statistically analyzed, and the turbine efficiency η of the engine after 100 hours of operation is obtained through identification and calculation. T,100 Simultaneously, it identifies and calculates the turbine efficiency η after the engine has worked for 200 hours, 300 hours, ... hours. T,200 η T,300 ...

[0055] η T,100 =f(n) H (5)

[0056] Step S330: Subtract the turbine efficiency identified after the engine has been running for a certain period of time from the baseline efficiency; the turbine efficiency decrease Δη after 100 hours of operation. T,100This can be expressed as Equation 6 below. Similarly, the turbine efficiency reduction corresponding to other operating hours such as 200 hours and 300 hours can be obtained, see... Figure 3 .

[0057] Δη T,100 =η T,基准 -η T,100 (6)

[0058] Therefore, different rotational speeds n H Turbine efficiency decrease Δη corresponding to operating hours T It is possible Figure 3 Interpolation is used to obtain the result.

[0059] By calculating the turbine efficiency decrease at different time points and forming function curves, the turbine efficiency decrease at any time point can be obtained by interpolation.

[0060] Step S400, Calculation of high-pressure turbine torque attenuation

[0061] Calculate the amount of high-pressure turbine torque reduction M caused by performance degradation after the corresponding engine has been operating for a certain number of hours. D for:

[0062] M D =ΔM T ×Δη T (7)

[0063] Substituting this into the rotor torque balance equation, the corresponding starter torque M is calculated. ST With output power p ST need.

[0064] This application first establishes the correspondence between starter torque and high-pressure turbine torque attenuation, and determines the correspondence between starter output power and starter torque. Then, it calculates the unit attenuation of the high-pressure turbine when the engine's high-pressure turbine efficiency decreases by 1%. Next, it identifies and calculates the high-pressure turbine efficiency at different relative physical speeds of the high-pressure rotor. Simultaneously, it statistically analyzes engine performance parameters at different high-pressure rotor relative physical speeds below idle speed during different engine operating hours, identifying and calculating the corresponding high-pressure turbine efficiency decrease Δη. T This allows for the calculation of the high-pressure turbine torque reduction M caused by performance degradation after the corresponding engine has been operating for a certain number of hours. DThis process yields the corresponding starter torque and output power requirements. The impact of performance degradation is considered, making the power calculation results more reliable and meeting the starter power requirements throughout the engine's entire lifespan. Even if engine performance degrades after long-term use, starting performance remains guaranteed. Furthermore, it improves the success rate of restarting the engine after an in-flight shutdown, enhancing the survivability of the aircraft and pilot. Simultaneously, the enhanced starter rotation capability provides more flexibility in adjusting the accelerator fluid during starting, significantly reducing the likelihood of starting stall and overheating issues.

[0065] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0066] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0067] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating starter power considering performance degradation, characterized in that, include: The relationship between starter torque and high-pressure turbine torque attenuation is established based on the rotor torque balance equation, and the relationship between starter output power and starter torque is determined. Based on the low-speed characteristics of rotating components and the overall engine performance calculation theory using extrapolation correction, the unit attenuation of the high-pressure turbine is calculated when the high-pressure turbine efficiency decreases by 1%. ; Before the engine leaves the factory, engine performance parameters at different high-pressure rotor relative physical speeds below idle are recorded. The high-pressure turbine efficiency at different high-pressure rotor relative physical speeds is identified and calculated. At the same time, engine performance parameters at different high-pressure rotor relative physical speeds below idle are statistically analyzed at different engine operating hours, and the corresponding decrease in high-pressure turbine efficiency is identified and calculated. ; Calculate the amount of high-pressure turbine torque reduction due to performance degradation after the corresponding engine has been operating for a certain number of hours. Substitute this into the rotor torque balance equation to calculate the corresponding starter torque and output power requirements; The method for calculating the decrease in high-pressure turbine efficiency is as follows: Based on the performance parameters corresponding to different engine speeds below idle, the turbine efficiency at different engine speeds before delivery is identified and calculated. As a benchmark efficiency: ； In the formula, Where is the relative physical speed of the high-pressure rotor, and F is the engine thrust. For engine temperature, Engine fuel consumption rate; Then, the engine performance parameters at different speeds below idle after the engine has been working for a specified time are statistically analyzed. The turbine efficiency of the engine after working for a specified time is obtained by identification and calculation. At the same time, the corresponding turbine efficiency after the engine has been working for other set times is also identified and calculated. Subtracting the turbine efficiency obtained after the engine has been running for a certain period of time from the baseline efficiency yields the decrease in turbine efficiency after the engine has been running for a certain period of time. This is calculated based on the relative physical speeds of different high-pressure rotors. Turbine efficiency reduction corresponding to operating hours Obtained through the difference; The decrease in high-pressure turbine torque due to performance degradation after the engine has been running for a certain period of time. for: 。 2. The starter power calculation method considering performance degradation as described in claim 1, characterized in that, The method for calculating the unit attenuation of the high-pressure turbine when the efficiency decreases by 1% is as follows: Calculate the unit attenuation of the high-pressure turbine corresponding to different high-pressure rotor relative physical speeds above engine ignition speed and below idle speed. For different high-voltage rotor relative physical speeds The high-pressure turbine unit decay rate and the relative physical speed of the high-pressure rotor are obtained by sorting from low to high and fitting the data. Function expressions between .

3. The starter power calculation method considering performance degradation as described in claim 2, characterized in that: The relative physical speeds of the high-voltage rotor include ignition speed, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and idle speed.

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