A continuous pulse incremental ignition fuel supply method for aircraft engines

Abstract

The present invention discloses a continuous pulse incremental ignition fuel supply method for aircraft engines. The method comprises: setting multiple fuel supply pulses, each fuel supply pulse including adjacent fuel supply time periods at a fixed fuel flow rate and fuel supply time periods at an incremental fuel flow rate, dynamically detecting the ignition state, terminating the ignition program when ignition is successful, and performing the next fuel supply pulse when ignition fails, with a preset time interval between the two fuel supply pulses, and the incremental fuel flow rate increasing in the order of the fuel supply pulses. The ignition fuel supply method provided by the present invention has enhanced compatibility with the auxiliary power unit body, improved the ignition success rate of the auxiliary power unit, enhanced environmental adaptability, and ensured that the auxiliary power unit can reliably ignite in extreme environments; when ignition is unsuccessful in a fuel supply pulse, the next fuel supply pulse ignition can be quickly and safely started, which not only achieves automatic and rapid ignition, but also eliminates the risk of deflagration or overheating at start-up caused by fuel accumulation.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation engines, and in particular to a continuous pulse incremental ignition and fuel supply method applied to aviation engines. Background Art

[0002] There is a risk of unsuccessful ignition of the auxiliary power unit (APU) during startup. If the ignition fails, the APU will not be able to enter normal working state and thus cannot output electrical power / pneumatic power, which will reduce the application and combat capabilities of the aircraft using the APU. Especially when the aircraft is performing emergency missions, the delay in timing will lead to certain negative effects.

[0003] The auxiliary power unit ignition process is as follows: after pressing the start button of the auxiliary power unit, the auxiliary power unit enters the starting program, and the electronic controller controls the backup starting contactor, ignition device, and main starting contactor to be powered on in sequence. The starting motor relay is closed, and the ignition device begins to ignite. That is, when the auxiliary power unit speed Ng = 0%, the auxiliary power unit is driven by the starting motor. After the rotation is successful, the engine speed continues to rise. When the speed Ng = 7%, the fuel solenoid valve opens and starts to supply fuel to the auxiliary power unit. The existing ignition fuel supply method generally adopts an open-loop fuel supply control method based on the Ng speed. Under certain environmental conditions, the ignition fuel supply flow rate is a constant value, and the fuel supply rule is as follows:

[0004]

[0005] Where: W f is the ignition fuel flow rate, k is the APU thermal correction coefficient, W f0 W is the initial starting fuel flow rate under sea level and standard atmospheric conditions, P2 is the atmospheric pressure, and T2 is the atmospheric temperature. f0 The variation pattern with Ng is shown in Table 1 below;

[0006] Table 1 Oil supply rules in the open-loop phase of the starting process

[0007]

[0008] The disadvantages of the above-mentioned ignition and fuel supply method are: (1) poor environmental adaptability. Under low temperature, high altitude and other environmental conditions, ignition failure is easy to occur due to poor atomization effect in the combustion chamber; (2) poor compatibility with the auxiliary power unit. As the life of the auxiliary power unit continues to accumulate, the performance of the combustion chamber decreases, and the spark energy generated by the ignition nozzle decreases due to long-term carbon deposition. The fixed fuel supply pattern cannot guarantee reliable ignition. Summary of the Invention

[0009] In order to solve the above problems, the inventors have made the present invention, and through specific implementation methods, provide a continuous pulse incremental ignition and fuel supply method for aircraft engines.

[0010] An embodiment of the present invention provides a continuous pulse incremental ignition fuel supply method for an aircraft engine, comprising the following steps:

[0011] Multiple fuel supply pulses are set, each fuel supply pulse includes adjacent time periods of fuel supply at a fixed fuel flow rate and time periods of fuel supply at an increasing fuel flow rate, and the ignition state is dynamically detected. When ignition is successful, the ignition program is terminated. When ignition fails, the next fuel supply pulse is performed. A preset time interval is between two fuel supply pulses, and the increasing fuel flow rate increases in the order of the fuel supply pulses.

[0012] Optionally, the continuous pulse incremental ignition fuel supply method applied to an aircraft engine further includes the following steps:

[0013] When multiple fuel supply pulses fail to ignite, fuel supply and ignition are stopped, and the starting procedure is terminated.

[0014] Optionally, multiple fuel supply pulses are provided, each fuel supply pulse includes adjacent fuel supply time periods at a fixed fuel flow rate and fuel supply time periods at an increasing fuel flow rate, the ignition state is dynamically detected, when ignition is successful, the ignition procedure is terminated, when ignition fails, the next fuel supply pulse is performed, the interval between two fuel supply pulses is a preset time, when multiple fuel supply pulses fail to ignite, the fuel supply and ignition are stopped, and the starting procedure is terminated, including the following steps:

[0015] Three fuel supply pulses are provided. In the first fuel supply pulse, fuel is supplied to the auxiliary power unit at a fixed fuel flow rate during a first fuel supply time period. When the first fuel supply time period ends, a second fuel supply time period begins. During the second fuel supply time period, fuel is supplied to the auxiliary power unit at the initial fuel flow rate. When ignition is successful, ignition fuel supply is terminated. When ignition fails, the first interruption time period begins when the second fuel supply time period ends.

[0016] When the first interruption period ends, a second fuel supply pulse is started, and a third fuel supply period is calculated. During the third fuel supply period, fuel is supplied to the auxiliary power unit at a fixed fuel flow rate. When the third fuel supply period ends, a fourth fuel supply period is calculated. During the fourth fuel supply period, fuel is supplied to the auxiliary power unit at a first increasing fuel flow rate. When ignition is successful, ignition fuel supply is terminated. When ignition fails, the second interruption period is calculated when the fourth fuel supply period ends.

[0017] When the second interruption time period ends, the third fuel supply pulse begins, and the fifth fuel supply time period starts. During the fifth fuel supply time period, the auxiliary power unit is fueled at a fixed fuel flow rate. When the fifth fuel supply time period ends, the sixth fuel supply time period starts. During the sixth fuel supply time period, the auxiliary power unit is fueled at a second increasing fuel flow rate. When the ignition is successful, the ignition fuel supply is terminated. When the ignition fails, the fuel supply and ignition are stopped, and the starting procedure is terminated.

[0018] Optionally, the continuous pulse incremental ignition fuel supply method applied to an aircraft engine further includes the following steps:

[0019] Determine the fixed fuel flow rate based on the auxiliary power unit fuel line layout and combustion chamber performance;

[0020] The ignition state is determined based on the increase in the exhaust temperature or whether the exhaust temperature is greater than 100°C.

[0021] Optionally, the continuous pulse incremental ignition fuel supply method applied to an aircraft engine further includes the following steps:

[0022] The initial fuel flow rate of the incremental fuel flow rate is determined according to Wf_base = β*f(P2, T2), where Wf_base represents the initial fuel flow rate, β is the fuel temperature correction factor, P2 is the atmospheric pressure, T2 is the atmospheric temperature, and f(P2, T2) is the fuel flow rate function used to determine the fuel flow rate before correction.

[0023] Optionally, the function table of the fuel flow function f(P2, T2) is:

[0024] Table 2f (P2, T2) Fuel flow rate as a function of P2, T2

[0025]

[0026] Where, the unit of P2 is kPa, the unit of T2 is °C, and the unit of f(P2, T2) is kg / h. Determine the fuel flow rate before correction based on the values ​​in the above table or the curve fitted based on the values ​​in the above table.

[0027] Optionally, the first incremental fuel flow rate is k1 times the initial fuel flow rate, and the second incremental fuel flow rate is k2 times the first incremental fuel flow rate. k1 and k2 are greater than 1 and less than 2, and k1 is less than k2.

[0028] Optionally, each time period for supplying fuel to the auxiliary power unit at a fixed fuel flow rate does not exceed 1 second, the total time period for supplying fuel at an increasing fuel flow rate does not exceed 10 seconds, and the preset time of each interval is not less than 2 seconds and not more than 3 seconds.

[0029] Optionally, during a preset time interval between two fuel supply pulses, the fuel accumulated in the combustion chamber is blown out of the combustion chamber body.

[0030] Optionally, the fixed fuel flow rate is greater than the fuel supply amount during any time period of fuel supply at an increasing fuel flow rate.

[0031] The beneficial effects of the above technical solutions provided by the embodiments of the present invention include at least:

[0032] The ignition and fuel supply method provided by the present invention has enhanced compatibility with the auxiliary power unit body, and will not reduce the ignition success rate due to the attenuation of the auxiliary power unit combustion chamber performance, thereby improving the ignition success rate of the auxiliary power unit, and the ignition success rate is close to 100%. The environmental adaptability of the auxiliary power unit using this method is enhanced, ensuring that the auxiliary power unit can be reliably ignited at an altitude of 12,000 meters, in plateau areas, and in high-altitude cold areas; when ignition is unsuccessful in the fuel supply pulse, the next fuel supply pulse ignition can be started quickly and safely, which not only realizes automatic and rapid ignition, but also eliminates the risk of fuel accumulation in the combustion chamber causing explosion during the next ignition or overheating during startup.

[0033] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0034] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 This is a timing diagram of the continuous pulse ignition and fuel supply method in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0038] In order to solve the problems existing in the prior art, an embodiment of the present invention provides a continuous pulse incremental ignition and fuel supply method applied to an aircraft engine.

[0039] An embodiment of the present invention provides a continuous pulse incremental ignition fuel supply method for an aircraft engine, comprising the following steps:

[0040] Multiple fuel supply pulses are set, each fuel supply pulse includes adjacent time periods of fuel supply at a fixed fuel flow rate and time periods of fuel supply at an increasing fuel flow rate, and the ignition state is dynamically detected. When ignition is successful, the ignition program is terminated. When ignition fails, the next fuel supply pulse is performed. A preset time interval is between two fuel supply pulses, and the increasing fuel flow rate increases in the order of the fuel supply pulses.

[0041] In some specific embodiments, the continuous pulse incremental ignition fuel supply method applied to an aircraft engine further includes the following steps:

[0042] When multiple fuel supply pulses fail to ignite, fuel supply and ignition are stopped, and the starting procedure is terminated.

[0043] In some specific embodiments, multiple fuel supply pulses are provided, each fuel supply pulse includes adjacent fuel supply time periods at a fixed fuel flow rate and fuel supply time periods at an increasing fuel flow rate, the ignition state is dynamically detected, when ignition is successful, the ignition procedure is terminated, when ignition fails, the next fuel supply pulse is performed, and a preset time interval is left between two fuel supply pulses. When multiple fuel supply pulses fail to ignite, fuel supply and ignition are stopped, and the starting procedure is terminated, including the following steps:

[0044] Three fuel supply pulses are provided. In the first fuel supply pulse, fuel is supplied to the auxiliary power unit at a fixed fuel flow rate during a first fuel supply time period. When the first fuel supply time period ends, a second fuel supply time period begins. During the second fuel supply time period, fuel is supplied to the auxiliary power unit at the initial fuel flow rate. When ignition is successful, ignition fuel supply is terminated. When ignition fails, the first interruption time period begins when the second fuel supply time period ends.

[0045] When the first interruption period ends, a second fuel supply pulse is started, and a third fuel supply period is calculated. During the third fuel supply period, fuel is supplied to the auxiliary power unit at a fixed fuel flow rate. When the third fuel supply period ends, a fourth fuel supply period is calculated. During the fourth fuel supply period, fuel is supplied to the auxiliary power unit at a first increasing fuel flow rate. When ignition is successful, ignition fuel supply is terminated. When ignition fails, the second interruption period is calculated when the fourth fuel supply period ends.

[0046] When the second interruption time period ends, the third fuel supply pulse begins, and the fifth fuel supply time period starts. During the fifth fuel supply time period, the auxiliary power unit is fueled at a fixed fuel flow rate. When the fifth fuel supply time period ends, the sixth fuel supply time period starts. During the sixth fuel supply time period, the auxiliary power unit is fueled at a second increasing fuel flow rate. When the ignition is successful, the ignition fuel supply is terminated. When the ignition fails, the fuel supply and ignition are stopped, and the starting procedure is terminated.

[0047] In some specific embodiments, the continuous pulse incremental ignition fuel supply method applied to an aircraft engine further includes the following steps:

[0048] Determine the fixed fuel flow rate based on the auxiliary power unit fuel line layout and combustion chamber performance;

[0049] The ignition state is determined based on the increase in the exhaust temperature or whether the exhaust temperature is greater than 100°C.

[0050] In some specific embodiments, the continuous pulse incremental ignition fuel supply method applied to an aircraft engine further includes the following steps:

[0051] The initial fuel flow rate of the incremental fuel flow rate is determined according to Wf_base = β*f(P2, T2), where Wf_base represents the initial fuel flow rate, β is the fuel temperature correction factor, which corrects the fuel flow rate based on the fuel temperature, P2 is the atmospheric pressure, T2 is the atmospheric temperature, and f(P2, T2) is the fuel flow function used to determine the fuel flow rate before correction.

[0052] In some specific embodiments, the function table of the fuel flow function f(P2, T2) is:

[0053] Table 2f (P2, T2) Fuel flow rate as a function of P2, T2

[0054]

[0055] Where P2 is in kPa, T2 is in °C, and f(P2,T2) is in kg / h. Determine the pre-correction fuel flow rate based on the values ​​in the preceding table or a curve fitted to the values. For example, when the atmospheric pressure and temperature are outside the values ​​shown in Table 2, fit the corresponding curve to the values ​​in Table 2 and use the curve to determine the pre-correction fuel flow rate at the corresponding atmospheric pressure and temperature.

[0056] In some specific embodiments, the first incremental fuel flow rate is k1 times the initial fuel flow rate, and the second incremental fuel flow rate is k2 times the first incremental fuel flow rate. k1 and k2 are greater than 1 and less than 2, and k1 is less than k2.

[0057] In some specific embodiments, the time period for supplying fuel to the auxiliary power unit at a fixed fuel flow rate does not exceed 1 second, the total time period for supplying fuel at an increasing fuel flow rate does not exceed 10 seconds, and the preset time for each interval is not less than 2 seconds and not more than 3 seconds.

[0058] In some specific embodiments, during the preset time interval between two fuel supply pulses, the fuel accumulated in the combustion chamber is blown out of the combustion chamber body.

[0059] In some specific embodiments, the fixed fuel flow rate is greater than the fuel supply amount during any time period of supplying fuel at an increasing fuel flow rate.

[0060] In some specific embodiments, after pressing the start button of the auxiliary power unit, the auxiliary power unit enters the start-up procedure. The electronic controller sequentially controls the standby start contactor, the ignition device, and the main start contactor to be powered on, the start motor relay closes, and the ignition device starts to ignite. That is, when the rotational speed Ng of the auxiliary power unit is 0%, the auxiliary power unit is rotated by the start motor. After successful rotation, the engine speed continues to rise. When the rotational speed Ng = 7%, the fuel solenoid valve opens and starts to supply fuel to the auxiliary power unit. The ignition and fuel supply law of the solution in this embodiment is as Figure 1 shown, where the horizontal axis represents time t and the vertical axis represents fuel flow rate wf. Figure 1 In it, Wf_plus is a fixed fuel flow rate, and its value is evaluated according to the fuel pipeline layout of the auxiliary power unit and the performance of the combustion chamber. Its function is to quickly fill the fuel pipeline, instantaneously increase the fuel flow rate, improve the fuel nozzle pressure, and improve the atomization effect, thereby improving the ignition success rate. The duration of Wf_plus should not be too long, generally controlled within 1 second, otherwise it is easy to cause overheating during start-up. Wf_base is the basic fuel flow rate required by the combustion chamber during ignition. k1 < k2, and k1 and k2 are generally taken in the range of (1, 2), and this value is corrected by the test results of the whole machine. The fuel supply time of t1~t2, t4~t5, and t7~t8 should not be too long, and is generally controlled within 10 seconds in engineering applications. The fuel supply interruption time of t2~t3 and t5~t6 is 2~3 seconds. This design is to prevent deflagration or overheating during start-up caused by fuel accumulation in the combustion chamber when ignition is unsuccessful under the condition of the previous fuel supply pulse. Through the 2~3-second interruption time, the fuel accumulated in the combustion chamber is blown out of the combustion chamber body under the action of the high-speed flowing air flow.

[0061] Figure 1 Among them, (1) a fixed flow rate of Wf_plus is given at the time of 0~t1, which is used to quickly fill the fuel pipeline and is beneficial to the successful ignition at the time of t1~t2;

[0062] (2) Whether the exhaust temperature collected by the electronic controller at time t1 to t2 is greater than 100°C is used to determine whether the ignition is successful. If the ignition is successful, the fuel supply from time t3 to t8 will be stopped;

[0063] (3) If ignition fails by time t2, the subsequent fuel supply operation will continue. The fuel supply interruption time t2 to t3 is set. At this time, the high-speed airflow brought by the engine operation can blow the fuel from time 0 to t2 out of the combustion chamber body, preventing overheating or deflagration during the fuel supply from t3 to t5;

[0064] (4) Since the period includes the period of increasing fuel supply in pulse order, the total fuel supply amount wf3 from t6 to t8 is greater than the total fuel supply amount wf2 from t3 to t5, and the total fuel supply amount wf2 from t3 to t5 is greater than the total fuel supply amount wf1 from t1 to t2. Increasing the fuel supply amount is conducive to successful ignition. Whether the exhaust temperature collected by the electronic controller at t3 to t5 is greater than 100°C is used to determine whether the ignition is successful. If the ignition is successful, the fuel supply from t6 to t8 will be stopped.

[0065] (5) If ignition is still unsuccessful between t3 and t5, the subsequent fuel supply operation will be carried out. If ignition is unsuccessful after three pulse fuel supply operations, the starting procedure will be terminated to avoid starting risks.

[0066] The present invention employs a three-pulse ignition fueling method: fueling pulses from 0 to t2, from t3 to t5, and from t6 to t8. Once the auxiliary power unit successfully ignites (the electronic controller determines whether ignition is successful based on the exhaust temperature increase), subsequent fueling pulses cease, and the fueling mode immediately switches to starting acceleration fueling. If the auxiliary power unit still fails to ignite after three fueling pulses, due to a malfunction of the auxiliary power unit or the ignition nozzle failing to produce a spark, fueling and ignition are stopped, terminating the starting sequence. This method has been tested and proven effective at altitudes of 12,000 meters, in high-altitude areas, and in cold regions, achieving a 100% ignition success rate for one auxiliary power unit.

[0067] In the above method of this embodiment, the ignition and fuel supply method provided by the present invention has enhanced compatibility with the auxiliary power unit body, and will not reduce the ignition success rate due to the attenuation of the auxiliary power unit combustion chamber performance, thereby improving the ignition success rate of the auxiliary power unit, and the ignition success rate is close to 100%. The environmental adaptability of the auxiliary power unit using this method is enhanced, ensuring that the auxiliary power unit can be reliably ignited at an altitude of 12,000 meters, in plateau areas, and in cold and high-altitude areas; when the ignition is unsuccessful in the fuel supply pulse, the next fuel supply pulse ignition can be started quickly and safely, which not only realizes automatic and rapid ignition, but also eliminates the risk of fuel accumulation in the combustion chamber causing the next ignition explosion or overheating during startup.

[0068] Those skilled in the art can change the above sequence without departing from the scope of protection of the present disclosure.

[0069] Any modifications, supplements, and equivalent replacements made within the scope of the principles of the present invention shall still fall within the scope of the patent of the present invention. The terms "first," "second," etc., mentioned above, do not indicate a sequence, but are merely used to identify relevant fuel flow rates, time periods, etc.

Claims

1. A continuous pulse incremental ignition fuel supply method for aircraft engines, characterized in that: The following steps are involved: Multiple fuel supply pulses are set, each fuel supply pulse includes an adjacent fuel supply time period at a fixed fuel flow rate and a fuel supply time period at an incremental fuel flow rate, the ignition state is dynamically detected, when the ignition is successful, the ignition fuel supply is terminated, when the ignition fails, the next fuel supply pulse is performed, the interval between the two fuel supply pulses is a preset time, and the incremental fuel flow rate increases in the order of the fuel supply pulses; The continuous pulse incremental ignition fuel supply method applied to an aircraft engine further comprises the following steps: Determine the initial fuel flow rate of the incremental fuel flow rate according to Wf_base=β*f(P2,T2), where Wf_base represents the initial fuel flow rate, β is the fuel temperature correction coefficient, P2 is the atmospheric pressure, T2 is the atmospheric temperature, and f(P2,T2) is the fuel flow rate function used to determine the fuel flow rate before correction; The function table of the fuel flow function f(P2, T2) is: f(P2, T2) Fuel flow rate as a function of P2 and T2 Where, the unit of P2 is kPa, the unit of T2 is °C, and the unit of f(P2, T2) is kg / h. Determine the fuel flow rate before correction based on the values ​​in the above table or the curve fitted based on the values ​​in the above table.

2. The method according to claim 1, wherein The continuous pulse incremental ignition fuel supply method applied to an aircraft engine further comprises the following steps: When multiple fuel supply pulses fail to ignite, fuel supply and ignition are stopped, and the starting procedure is terminated.

3. The method according to claim 2, wherein Multiple fuel supply pulses are set, each fuel supply pulse includes adjacent fuel supply time periods at a fixed fuel flow rate and fuel supply time periods at an increasing fuel flow rate, the ignition state is dynamically detected, when ignition is successful, the ignition program is terminated, when ignition fails, the next fuel supply pulse is performed, the interval between two fuel supply pulses is preset, when multiple fuel supply pulses fail to ignite, the fuel supply and ignition are stopped, and the starting program is terminated, including the following steps: Three fuel supply pulses are provided. In the first fuel supply pulse, fuel is supplied to the auxiliary power unit at a fixed fuel flow rate during a first fuel supply time period. When the first fuel supply time period ends, a second fuel supply time period begins. During the second fuel supply time period, fuel is supplied to the auxiliary power unit at the initial fuel flow rate. When ignition is successful, ignition fuel supply is terminated. When ignition fails, the first interruption time period begins when the second fuel supply time period ends. When the first interruption period ends, a second fuel supply pulse is started, and a third fuel supply period is calculated. During the third fuel supply period, fuel is supplied to the auxiliary power unit at a fixed fuel flow rate. When the third fuel supply period ends, a fourth fuel supply period is calculated. During the fourth fuel supply period, fuel is supplied to the auxiliary power unit at a first increasing fuel flow rate. When ignition is successful, ignition fuel supply is terminated. When ignition fails, the second interruption period is calculated when the fourth fuel supply period ends. When the second interruption time period ends, the third fuel supply pulse begins, and the fifth fuel supply time period starts. During the fifth fuel supply time period, the auxiliary power unit is fueled at a fixed fuel flow rate. When the fifth fuel supply time period ends, the sixth fuel supply time period starts. During the sixth fuel supply time period, the auxiliary power unit is fueled at a second increasing fuel flow rate. When the ignition is successful, the ignition fuel supply is terminated. When the ignition fails, the fuel supply and ignition are stopped, and the starting procedure is terminated.

4. The method according to claim 1, wherein The continuous pulse incremental ignition fuel supply method applied to an aircraft engine further comprises the following steps: Determine the fixed fuel flow rate based on the auxiliary power unit fuel line layout and combustion chamber performance; The ignition state is determined based on the increase in the exhaust temperature or whether the exhaust temperature is greater than 100°C.

5. The method according to claim 3, wherein The first incremental fuel flow rate is k1 times the initial fuel flow rate, and the second incremental fuel flow rate is k2 times the first incremental fuel flow rate. k1 and k2 are greater than 1 and less than 2, and k1 is less than k2.

6. The method according to claim 1, wherein Each time period during which the auxiliary power unit is supplied with fuel at a fixed fuel flow rate shall not exceed 1 second, and the total time period during which fuel is supplied at an increasing fuel flow rate shall not exceed 10 seconds. The preset time for each interval shall not be less than 2 seconds and not more than 3 seconds.

7. The method according to claim 1, wherein During the preset time between two fuel supply pulses, the fuel accumulated in the combustion chamber is blown out of the combustion chamber body.

8. The method according to any one of claims 1 to 7, characterized in that: The fixed fuel flow rate is greater than the fuel supply amount during any time period of fuel supply at an increasing fuel flow rate.

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