A design method for high-altitude start-up fuel supply patterns based on plain start-up fuel supply patterns.

Abstract

This application belongs to the field of aero-engine design and presents a design method for high-altitude starting fuel supply patterns based on the low-altitude starting fuel supply patterns. It involves first conducting high-altitude bench tests on the starter to obtain the power reduction characteristics of the starter at different altitudes. Then, based on the power balance equation, the acceleration time of the starter from rotor standstill to idle speed is determined. Finally, based on the acceleration time of the starter from rotor standstill to idle speed, the time allocation of the three starting stages of the starting process—starter engagement, starter disengagement, and engine starting—is performed to obtain the high-altitude starting fuel supply pattern. This method enables rapid and accurate design of the high-altitude fuel supply pattern, taking into account the engine's stability margin design in high-altitude areas, starter power characteristics, and the attenuation characteristics of starter power with increasing altitude, thus avoiding abnormal phenomena such as engine cold suspension and overheating. Furthermore, it can be based on ground starting data statistics, achieving better design compatibility and reducing debugging work.

Description

Technical Field

[0001] This application belongs to the field of aero-engine design, and specifically relates to a design method for high-altitude start-up fuel supply law based on the start-up fuel supply law in plains areas. Background Technology

[0002] my country has eight of the world's top ten high-altitude airports, which creates a stronger demand for the operation of Chinese military and civilian aircraft and engines. This is of great significance to my country's national security, the advancement of national defense, and the improvement of people's lives in high-altitude areas.

[0003] Currently, my country lacks mature design methods for engines used at high altitudes. The technical measures generally adopted include two approaches: external and internal. External approaches include vacuuming and replacing the starter with a more powerful one. Internal approaches mainly involve improving component capabilities and designing fuel supply patterns. Fuel supply pattern design generally corrects the fuel quantity by adjusting the pressure as altitude increases, but it does not consider matching the starter power. Moreover, the design process is relatively simple and cannot accommodate the margin characteristics of existing components. Generally, the fuel supply pattern is adjusted and verified on-site using high-altitude test benches or mobile test stands, and then this state is maintained for high-altitude use.

[0004] The adopted technical solution lacks a direct and rapid high-altitude fuel supply pattern design method that takes into account engine margin and starter power characteristics. It primarily relies on methods such as high-altitude mobile test benches or on-site high-altitude starting verification to explore a baseline fuel supply pattern through experimentation and debugging. However, this technology has significant drawbacks: long testing cycles, high manpower and material costs, low debugging efficiency, and the inability to obtain an optimal fuel supply pattern. It is generally highly dependent on the individual engines used for testing, resulting in mass-produced engines not adapting well to high-altitude environments. Furthermore, during actual use, the engine is prone to cold suspension and overheating anomalies.

[0005] Therefore, how to quickly design the fuel supply pattern for high-altitude startup is a problem that needs to be solved. Summary of the Invention

[0006] The purpose of this application is to provide a design method for plateau start-up fuel supply patterns based on plain start-up fuel supply patterns, in order to solve the problems of long design cycles and high individual correlations in existing plateau start-up fuel supply patterns.

[0007] The technical solution of this application is: a design method for plateau start-up fuel supply law based on plain start-up fuel supply law, including:

[0008] A high-altitude bench test was conducted on the starter motor to obtain the power reduction characteristics of the starter motor at different heights.

[0009] Based on the power balance equation, the acceleration time for the starter motor to accelerate from rotor standstill to idle speed is determined as follows:

[0010]

[0011] In the formula, P H-T P is the starter motor output power. T η represents the turbine output power; P K P is the compressor power; 功率提取 For aircraft power extraction; P T ·η-P K The high-pressure turbine power is used; the starter output power P at sea level and plateau conditions is obtained by analyzing the starter's altitude and speed characteristics. H-T Characteristics; Aircraft power extraction P 功率提取 The value is fixed; the high-pressure turbine power P is obtained through a starting torque measurement test. T ·η-P K ;

[0012] Based on the acceleration time of the starter motor from rotor standstill to idle speed, the time allocation of the three starting stages of the starting process—starter motor rotation, starter motor disengagement, and engine starting—is determined to obtain the fuel supply pattern for starting at high altitudes.

[0013] Preferably, the method for obtaining the high-pressure turbine power is as follows:

[0014] Ignoring the effects of flow rate, speed, and turbine inlet total temperature on the high-pressure turbine power at different speeds under the same air-fuel ratio, the relationship between turbine residual power and intake flow rate at different starting heights is as follows:

[0015] (P T ·η-P K ) / W=C

[0016] In the formula, W is the core machine airflow, and C is a constant;

[0017] Based on engine principle performance calculations, the intake airflow of the core engine during startup under airport conditions at different altitudes is obtained. The constant C is then dimensionless, yielding the increment t of the high-altitude startup time relative to the ground startup time:

[0018]

[0019] This application presents a method for designing a high-altitude starting fuel supply pattern based on the low-altitude starting fuel supply pattern. First, a high-altitude bench test of the starter motor is conducted to obtain the power reduction characteristics of the starter motor at different altitudes. Then, based on the power balance equation, the acceleration time of the starter motor from rotor standstill to idle speed is determined. Finally, based on the acceleration time of the starter motor from rotor standstill to idle speed, the time allocation of the three starting stages of the starting process—starter motor engagement, starter motor disengagement, and engine starting—is performed to obtain the high-altitude starting fuel supply pattern. This method enables rapid and precise design of the high-altitude fuel supply pattern, considering the engine's stability margin design in high-altitude areas, the starter motor power characteristics, and the starter motor power attenuation characteristics with increasing altitude, avoiding abnormal phenomena such as engine cold suspension and overheating. Furthermore, it can be based on ground starting data statistics, achieving better design compatibility and reducing debugging work. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a schematic diagram of the overall process of this application;

[0022] Figure 2 This is a schematic diagram of the time allocation for the ground start-up process in this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0024] A method for designing high-altitude start-up fuel supply patterns based on plain start-up fuel supply patterns, such as... Figure 1 As shown, it includes the following steps:

[0025] Step S100: Conduct a high-altitude bench test of the starter motor to obtain the power reduction characteristics of the starter motor at different heights;

[0026] When conducting bench tests on starters at different heights, the same set of equipment should be used to ensure the accuracy of the data. For example, the power of a certain type of starter decreases rapidly with increasing altitude. Taking an altitude of 4,000 meters as an example, the maximum power decreases by about 24% relative to sea level.

[0027] Step S200: Based on the power balance equation, determine the acceleration time of the starter motor from rotor standstill to idle speed as follows:

[0028]

[0029] In the formula, P H-TP is the starter motor output power. T η represents the turbine output power; P K P is the compressor power; 功率提取 For aircraft power extraction; P T ·η-P K For high-pressure turbine power;

[0030] The acceleration time from rotor standstill to idle speed can be derived as follows:

[0031]

[0032] The starter output power P at sea level and plateau conditions was obtained by analyzing the starter's altitude and speed characteristics. H-T Characteristics; Aircraft power extraction P 功率提取 For high-altitude start-up without loading, P is a fixed value. 功率提取 =0; P T ·η-P K The remaining engine power after the turbine overcomes the resistance of the compressor, accessories, and friction can be obtained by measuring the starting torque under sea-level conditions.

[0033] The power of a high-pressure turbine is a function of the turbine inlet flow rate and the enthalpy drop at the turbine inlet and outlet. The enthalpy drop at the turbine inlet and outlet, in turn, is a function of the total inlet temperature, speed, and flow rate of the high-pressure turbine. During the starting phase at different heights, it can be approximated that, under the same air-fuel ratio, the flow rate, speed, and total inlet temperature at different speeds are not significantly different; or, in other words, the common operating line of the engine does not change much. Therefore, it can be approximated that the remaining turbine power at different starting heights is proportional to the intake flow rate.

[0034] (P T ·η-P K ) / W=C (3)

[0035] In the formula, W is the core engine airflow, which is approximately considered to be directly proportional to the turbine inlet airflow.

[0036] By performing performance calculations based on engine principles, the intake airflow of the core engine during startup under different airport altitude conditions can be obtained. Then, using the above formula, the corresponding turbine residual power under high-altitude conditions can be calculated and evaluated, and the constant C can be determined.

[0037] P H-T +P T ·η-P K -P 功率提取 Rewritten as:

[0038] This makes the parameters dimensionless:

[0039]

[0040] Based on the starter characteristics, the change in remaining power at different altitudes relative to sea level can be obtained. According to the calculation formula, the increment of the start-up time at the plateau relative to the start-up time at ground level can be obtained.

[0041] Taking an altitude of 4000m as an example, the plateau start-up time can be approximately calculated to be about 1.4 to 1.5 times that of the sea level start-up time.

[0042] Step S300: Based on the acceleration time of the starter motor from rotor standstill to idle speed, the time allocation of the three starting stages of the starting process, namely starter motor rotation, starter motor disengagement and engine starting, is performed to obtain the high-altitude starting fuel supply pattern.

[0043] Assuming an initial sea-level start-up time of 65 seconds, ground start-up according to engine principles can be divided into three stages, see... Figure 2 ;

[0044] In the first section, at sea level, the engine ignites and supplies fuel according to its speed, with a time of about 20 seconds. Based on the time calculated earlier, the ignition and fuel supply time at high altitude is about 28 seconds. However, engine ignition and fuel supply generally has a time limit (i.e., 22 seconds). Therefore, the engine ignition and fuel supply is carried out according to the time, and the ignition and fuel supply speed will be relatively lower than at ground level.

[0045] In the second stage, at sea level, the starter motor typically disengages after the engine reaches its disengagement speed, with a disengagement time generally around 54 seconds. At high altitudes, engine ignition is time-based, and the engine speed is lower. Considering the 6-second (28-22-second) time difference between the first stage ignition and fuel supply, the second stage lasts approximately 53 seconds. Adding the 22-second ignition and fuel supply time exceeds the 60-second disengagement time limit for the starter motor. Therefore, the actual starter motor disengagement is time-based. However, the design of the engine fuel supply pattern for this stage should also ensure that the engine speed is higher than the engine's equilibrium speed when the starter motor disengages, i.e., around 62% of the engine's speed ratio.

[0046] The third step involves adjusting the engine speed increase rate based on the remaining time.

[0047] By adjusting the engine's fuel supply pattern according to the corresponding time intervals, it can be ensured that the engine does not overheat when starting at high altitudes.

[0048] This application first conducts high-altitude bench tests on the starter motor to obtain the power reduction characteristics of the starter motor at different altitudes. Then, based on the power balance equation, it determines the acceleration time of the starter motor from rotor standstill to idle speed. Finally, based on the acceleration time of the starter motor from rotor standstill to idle speed, it allocates the time for the three starting stages of the starting process: starter motor rotation, starter motor disengagement, and engine starting, thus obtaining the high-altitude starting fuel supply law. This allows for rapid and precise design of the high-altitude fuel supply law, taking into account the engine's stability margin design in high-altitude areas, the starter motor power characteristics, and the starter motor power attenuation characteristics with increasing altitude, avoiding abnormal phenomena such as engine cold suspension and overheating. Based on ground starting data statistics, it achieves better design compatibility and reduces debugging work.

[0049] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for designing a high-altitude starting fuel supply pattern based on the starting fuel supply pattern in plains areas, characterized in that, include: A high-altitude bench test was conducted on the starter motor to obtain the power reduction characteristics of the starter motor at different heights. Based on the power balance equation, the acceleration time for the starter motor to accelerate from rotor standstill to idle speed is determined as follows: ； In the formula, This refers to the starter motor output power; This refers to the turbine output power; Compressor power; For aircraft power extraction; - The power output of the high-pressure turbine is obtained; the starter output power at sea level and at high altitude is obtained by analyzing the starter's altitude-speed characteristics. Features; Aircraft power extraction The value is fixed; the high-pressure turbine power is obtained through a starting torque measurement test. - ; Based on the acceleration time of the starter motor from rotor standstill to idle speed, the time allocation of the three starting stages of the starting process—starter motor rotation, starter motor disengagement, and engine starting—is determined to obtain the high-altitude starting fuel supply pattern. The method for obtaining the power of the high-pressure turbine is as follows: Ignoring the effects of flow rate, speed, and turbine inlet total temperature on the high-pressure turbine power at different speeds under the same air-fuel ratio, the relationship between turbine residual power and intake flow rate at different starting heights is as follows: ； In the formula, W is the core machine airflow, and C is a constant; Based on engine principle performance calculations, the intake airflow of the core engine during startup under airport conditions at different altitudes is obtained. The constant C is then dimensionless, yielding the increment t of the high-altitude startup time relative to the ground startup time: 。

Images