Turbofan engine starting and flameout detection method and system

Abstract

The invention provides a turbofan engine starting and flameout detection method and system. The method comprises the steps that the rotating speed change rate of an engine is determined; determining an exhaust temperature; determining the total pressure ratio of the engine, wherein the total pressure ratio of the engine is related to compressor outlet static pressure and engine inlet total pressure; if any two of the following characteristics are met, it is judged that the engine is started and flamed out: the first characteristic is that the engine speed change rate is smaller than a first threshold; secondly, the engine speed change rate is smaller than a second threshold value, and the exhaust temperature is monotonically decreased; thirdly, the total pressure ratio of the engine is smaller than a third threshold value, and the third threshold value is related to the rotating speed of the engine.

Description

Technical Field

[0001] This invention relates to turbofan engines, and more specifically to a method and system for detecting turbofan engine start-up and shutdown. Background Technology

[0002] For aero engines, the start-up process is the intermediate step from a shutdown state to a stable operating state, and it is also a prerequisite for ensuring the normal operation of the engine. An aero engine consists of an inner duct and an outer bypass duct. The airflow entering the inner duct passes sequentially through the compressor, combustion chamber, and turbine. Inside the combustion chamber, it mixes with fuel and burns. The combustion gases then do work through the turbine, driving the compressor to compress the air.

[0003] The starting process requires the turbine to work and accelerate the engine shaft, or both the turbine and starter motor must work together to accelerate the engine shaft. In starting scenarios requiring starter motor input, the engine speed is low in the initial stage, and the turbine's work capacity is weak, making it unable to accelerate the engine independently. When the combustion chamber shuts off, it cannot produce high-temperature, high-pressure combustion gases, the turbine ceases to work, and the starter motor alone cannot complete the starting process. In starting scenarios where starter motor input is not required or the starter motor is disengaged, when the combustion chamber shuts off, it cannot produce high-temperature, high-pressure combustion gases, the turbine ceases to work, and the starter will also fail, preventing the starter process from completing. Therefore, the detection and handling of flameout during starting is crucial, impacting airline operational efficiency and even flight safety.

[0004] However, during flight operations, engine shutdown detection can only be performed directly using onboard engine speed, temperature, or pressure signals, achieved by setting thresholds for these signals. Since these signals haven't undergone further calculations, their direct use to reflect the engine's operating status is very limited, leading to high false alarm and false negative rates. Summary of the Invention

[0005] The purpose of this invention is at least to provide a method and system for detecting the start-up and shutdown of a turbofan engine, which can reduce the false alarm rate and the missed detection rate.

[0006] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0007] One embodiment of the present invention provides a method for detecting engine start-up and shutdown of a turbofan engine. The method includes: determining the rate of change of engine speed; determining the exhaust temperature; determining the total pressure ratio of the engine, the total pressure ratio of the engine being related to the compressor outlet static pressure and the total pressure at the engine inlet; and determining engine start-up and shutdown if any two of the following characteristics are met: first characteristic: the rate of change of engine speed is less than a first threshold; second characteristic: the rate of change of engine speed is less than a second threshold, and the exhaust temperature decreases monotonically; third characteristic: the total pressure ratio of the engine is less than a third threshold, the third threshold being related to the engine speed.

[0008] In some embodiments, if the rate of change of engine speed at any time point within the first timing period is less than the first threshold, then feature one is determined to be satisfied.

[0009] In some embodiments, if the rate of change of engine speed at any point in time during the second timing period is less than the second threshold, and the exhaust temperature decreases monotonically during the second timing period, then feature two is satisfied.

[0010] In some embodiments, if the rate of change of engine speed at any point in time within the second timing period is not less than the second threshold, it is determined that feature two is not satisfied.

[0011] In some embodiments, before determining whether any two of the first, second, and third features are satisfied, it is determined whether the engine is in a starting state; if it is determined that the engine is in a starting state, then the determination of whether any two features are satisfied is initiated.

[0012] In some embodiments, the rate of change of engine speed is the time derivative of engine speed.

[0013] In some embodiments, the total pressure at the engine inlet is positively correlated with the ambient atmospheric pressure.

[0014] In some embodiments, the first threshold is a negative value, and the first threshold is related to the flight altitude and Mach number.

[0015] In some embodiments, the second threshold is greater than the first threshold.

[0016] In some embodiments, the third threshold is determined by engine speed interpolation.

[0017] One embodiment of the present invention provides a turbofan engine start-stop detection system. The system includes a first determining module, an acquisition module, a determining module, and a judging module. The first determining module is used to determine the engine speed change rate; the acquisition module is used to determine the exhaust temperature; the determining module is used to determine the engine total pressure ratio, which is related to the compressor outlet static pressure and the engine inlet total pressure; the judging module is used to determine whether the engine has started and stopped. Based on satisfying any two of the following characteristics, the judging module determines whether the engine has started and stopped: First characteristic: the engine speed change rate is less than a first threshold; Second characteristic: the engine speed change rate is less than a second threshold, and the exhaust temperature decreases monotonically; Third characteristic: the engine total pressure ratio is less than a third threshold, which is related to the engine speed.

[0018] One embodiment of the present invention provides a turbofan engine start-up and shutdown detection device, the device including a processor, the processor being used to execute the turbofan engine start-up and shutdown detection method described in any of the above embodiments.

[0019] One embodiment of the present invention provides a non-transitory computer-readable medium for storing instructions, which, when executed by at least one processor, cause at least one processor to implement the turbofan engine start-up and shutdown detection method described in any of the above embodiments.

[0020] The turbofan engine start-up and shutdown detection method of the present invention realizes real-time detection of start-up and shutdown faults on the flight path through existing airborne sensors. It has the characteristics of high detection rate and low false alarm rate, which improves the efficiency of flight line operation and flight safety. Attached Figure Description

[0021] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related properties or features may have the same or similar reference numerals. Wherein:

[0022] Figure 1 This is an exemplary block diagram of a turbofan engine start-up and shutdown detection system according to some embodiments of this specification;

[0023] Figure 2 This is an exemplary flowchart of a turbofan engine start-up and shutdown detection method according to some embodiments of this specification;

[0024] Figure 3 This is a logic block diagram for determining the start-up and shutdown of a turbofan engine, as shown in some embodiments of this specification.

[0025] Figure 4 This is a logic block diagram for determining the first feature according to some embodiments of this specification;

[0026] Figure 5 A graph showing the rate of change of engine speed during startup;

[0027] Figure 6 This is a logic block diagram for determining the second feature according to some embodiments of this specification;

[0028] Figure 7 It is a graph showing the change in exhaust temperature when the engine starts;

[0029] Figure 8 This is a logic block diagram for determining the third feature according to some embodiments of this specification;

[0030] Figure 9 It is a graph showing the relationship between the total engine pressure ratio and the engine speed when the engine starts. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0032] It should be understood that the terms “system,” “device,” “unit,” and / or “module” used herein are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other words can achieve the same purpose, they may be replaced by other expressions.

[0033] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0034] The turbofan engine start-up and shutdown detection system is used to detect the engine's starting status under different operating parameters. Based on speed, temperature, and pressure data, it determines the engine speed change rate, exhaust temperature, and total pressure ratio. Based on this, it determines whether the engine has started and shut down, allowing for timely handling and ensuring flight safety. In some embodiments, the turbofan engine start-up and shutdown detection system is applied to the whole-engine bench testing of aero-engines, which helps improve test safety and reduces the difficulty of test data mining. In some embodiments, the turbofan engine start-up and shutdown detection system is applied during line flight, reducing false alarm and missed detection rates, which helps ensure flight safety. In some embodiments, the turbofan engine start-up and shutdown detection system is applied to the start-up and shutdown judgment of ground gas turbines and marine gas turbines, which helps improve the operational safety of gas turbines. This specification uses the application of the turbofan engine start-up and shutdown detection system in line flight as an example. The application scenarios of the turbofan engine start-up and shutdown detection system include processors, memory, and data acquisition devices.

[0035] The processor processes data and / or information from at least one component or external data source in the turbofan engine start-stop detection system. For example, the processor acquires and processes speed, temperature, and pressure data collected by a data acquisition device via a network. In some embodiments, the processor is local or remote. In some embodiments, the processing device is implemented on a cloud platform.

[0036] Memory is used to store data and / or instructions. For example, memory stores instructions or programs that can be invoked by a processor. As another example, memory stores processed data output by the processor and acquired data output by a data acquisition device. Memory includes one or more storage components, each of which can be a separate device or part of another device. In some embodiments, the memory is implemented on a cloud platform.

[0037] The data acquisition device is used to collect data related to the engine's operating status. In some embodiments, the data acquisition device includes a speed sensor, a temperature sensor, and a pressure sensor, etc. In some embodiments, the data acquisition device is configured on an aircraft using the engine. In some embodiments, the data acquisition device transmits the collected data to a processor and memory, etc., via a network or cable.

[0038] Figure 1 This is an exemplary block diagram of a turbofan engine start-stop detection system according to some embodiments of this specification.

[0039] like Figure 1 As shown, the gearbox temperature testing system 10 includes a first determining module 11, an acquisition module 12, a second determining module 13, and a judgment module 14.

[0040] The first determining module 11 is used to determine the engine speed change rate. The first determining module 11 determines the engine speed change rate based on the engine speed. For more information on the engine speed change rate, see [link to relevant documentation]. Figure 2 And its related descriptions.

[0041] Module 12 is used to acquire the exhaust temperature. Module 12 acquires the actual collected exhaust temperature. For more information on acquiring exhaust temperature, please refer to [link to relevant documentation]. Figure 2 And its related descriptions.

[0042] The second determining module 13 is used to determine the engine total pressure ratio. The second determining module 13 determines the engine total pressure ratio based on the compressor outlet static pressure and the engine inlet total pressure. For more information on engine total pressure ratio, see [link to relevant documentation]. Figure 2 And its related descriptions.

[0043] The determination module 14 is used to determine whether the engine has started and stopped. Based on any two of the following characteristics, the determination module 14 determines whether the engine has started and stopped: First characteristic: the rate of change of engine speed is less than a first threshold; Second characteristic: the rate of change of engine speed is less than the second threshold, and the exhaust temperature decreases monotonically; Third characteristic: the total pressure ratio of the engine is less than a third threshold, where the third threshold is related to the engine speed. For more information on determining engine start and stop, please refer to [link to relevant documentation]. Figure 2 And its related descriptions.

[0044] Figure 2 This is an exemplary flowchart of a turbofan engine start-up and shutdown detection method according to some embodiments of this specification. In some embodiments, process 20 is executed by a processor. Figure 2 As shown, process 20 includes the following steps:

[0045] Step 21: Determine the rate of change of engine speed.

[0046] In some embodiments, the rate of change of engine speed is the time derivative of engine speed. In some embodiments, the rate of change of engine speed is the first time derivative of engine speed. The first time derivative of engine speed is denoted by N²dot, i.e., the rate of change of engine speed, and is defined as N²dot = dN² / dt, where N² is the engine speed. In some embodiments, engine speed refers to the high-voltage shaft speed of the engine. In some embodiments, engine speed is acquired by acquiring data from a speed acquisition device used to collect the high-voltage shaft speed.

[0047] Step 22: Determine the exhaust temperature.

[0048] In some embodiments, the exhaust temperature is determined by acquiring data from a temperature sensor used to collect the exhaust temperature.

[0049] Step 23: Determine the engine total pressure ratio. The engine total pressure ratio is related to the compressor outlet static pressure and the engine inlet total pressure.

[0050] In some embodiments, the engine total pressure ratio (OPR) is calculated based on the compressor outlet static pressure Ps3 and the engine inlet total pressure P2 using the formula: OPR = Ps3 / P2. In some embodiments, the compressor outlet static pressure Ps3 and the engine inlet total pressure P2 are obtained by acquiring data from pressure sensors used for pressure measurement. In some embodiments, to ensure the accuracy of the engine inlet total pressure P2, the engine inlet total pressure P2 is calculated using the formula: P2 = P0(1 + (k-1) / 2Ma 2 ) (k / (k-1)) It is determined that P0 is the atmospheric ambient pressure, Ma is the Mach number, and k is the air adiabatic constant. Therefore, the total inlet pressure P2 is positively correlated with the atmospheric ambient pressure P0.

[0051] Step 24: If any two of the first, second, and third characteristics are satisfied, then the engine is determined to have started and stalled. It should be understood that satisfying any two of the first, second, and third characteristics includes satisfying all three characteristics simultaneously.

[0052] In some embodiments, before determining whether any two of the first, second, and third characteristics are satisfied, it is necessary to determine whether the engine is in a starting state. When the engine is not in a starting state, it is unnecessary to determine whether the engine is starting or shutting down. In some embodiments, starting states include ground starting, in-flight assisted starting, and windmill starting. In some embodiments, if it is determined that the engine is in a starting state, the determination of whether any two characteristics are satisfied is initiated. If it is determined that the engine is not in a starting state, the determination of whether any two characteristics are satisfied is not initiated. If it is determined that the engine is in a starting state, the characterization parameter L0 = 1; if it is determined that the engine is not in a starting state, the characterization parameter L0 = 0.

[0053] Meeting any two of the first, second, and third characteristics determines engine start-stop, which improves the detection rate and reduces false alarm and missed detection rates. If only one of the first, second, and third characteristics is met, only a start-stop alarm is issued without fault handling, thus preventing false alarms.

[0054] The decision logic for step 24 is as follows: Figure 3As shown, L1 is the characterization parameter of the first feature. When the first feature is satisfied, L1 = 1; when the first feature is not satisfied, L1 = 0. L2 is the characterization parameter of the second feature. When the second feature is satisfied, L2 = 1; when the second feature is not satisfied, L2 = 0. L3 is the characterization parameter of the third feature. When the third feature is satisfied, L3 = 1; when the third feature is not satisfied, L3 = 0. When L0*(L1 + L2 + L3)>1, that is, the engine is in the starting state and any two of the first feature, the second feature and the third feature are satisfied, it is determined that a starting and stalling fault has occurred, and an alarm is triggered accordingly and the stalling process is executed. When 0 < L0*(L1 + L2 + L3) ≤ 1, that is, the engine is in the starting state and one of the first feature, the second feature and the third feature is satisfied, it is determined that a starting and stalling fault is suspected, and a warning is issued but no treatment is performed. When L0*(L1 + L2 + L3) ≤ 0, that is, the engine is not in the starting state or the engine is in the starting state but does not satisfy any of the first feature, the second feature and the third feature, it is not determined that a starting and stalling fault has occurred.

[0055] The first feature in step 24 is that the engine speed change rate is less than the first threshold.

[0056] In some embodiments, the first threshold is negative. When the engine speed change rate is less than the first threshold, it means that the engine speed drops sharply. In some embodiments, the first threshold is related to the flight altitude and Mach number. In some embodiments, the first threshold is a function of the flight altitude and Mach number and is preset. For example, the function of the first threshold and the flight altitude and Mach number is pre-stored in the memory. Associating the first threshold with the flight altitude and Mach number related to the flight state of the aircraft can determine whether the first feature is satisfied according to the actual flight state of the aircraft, ensuring the reliability of the judgment.

[0057] In some embodiments, if the engine speed change rate at any time point within the first timing period is less than the first threshold, it is determined that the first feature is satisfied. Specifically, the judgment logic of the first feature is as Figure 4 shown.

[0058] See Figure 4The process involves determining the engine speed change rate N2dot at a first time point and checking if it is less than a first threshold N2dotthd1. If not, feature one is considered false, L1 = 0, and the timing is cleared. If yes, it is determined whether timing has not started. If yes, the first time point t = t1 is recorded, and timing begins with a duration (i.e., the timing cycle length) of Tk1. If no, timing has started. If the engine speed change rate N2dot is detected to be less than the first threshold N2dotthd1 at any time point within the first timing cycle (i.e., t1 ≤ t ≤ t1 + Tk1), feature one is considered true, and L1 = 1. In some embodiments, the timing cycle length Tk1 ranges from 0 to 5 seconds; for example, the timing cycle length Tk1 is 2 seconds or 3 seconds.

[0059] The judgment logic for the first feature is based on the characteristics of the rate of change of engine speed during engine start-up and shutdown. These characteristics are as follows: Figure 5 As shown. Figure 5 The curve in the figure represents the state of N2dot changing over time. N2dot is positive when the engine starts, and decreases sharply when the engine starts and stops, until it is less than the first threshold. The duration of N2dot being less than the first threshold is the length of the timing cycle, which is Tk1.

[0060] The second characteristic in step 24 is that the rate of change of engine speed is less than the second threshold and the exhaust temperature decreases monotonically.

[0061] In some embodiments, the second threshold is greater than the first threshold. When the rate of change of engine speed is less than the second threshold, it indicates that the engine speed is slowly increasing or slowly decreasing. In some embodiments, the second threshold is a positive value. The second threshold is preset. For example, the second threshold is stored in memory in advance. In some embodiments, if the rate of change of engine speed at any point in time within the second timing cycle is not less than the second threshold, it is determined that feature two is not satisfied. In some embodiments, if the rate of change of engine speed at any point in time within the second timing cycle is less than the second threshold, and the exhaust temperature decreases monotonically within the second timing cycle, it is determined that feature two is satisfied. In some embodiments, the determination of the monotonically decreasing exhaust temperature within the second timing cycle is implemented by: determining that the average exhaust temperature decreases sequentially in chronological order within multiple consecutive detection cycles within the second timing cycle. Specifically, the determination logic of the second feature is as follows: Figure 6 As shown.

[0062] See Figure 6The process involves determining the engine speed change rate N2dot at the first time point and checking if it is less than the second threshold N2dotthd2. If not, the second characteristic is considered false, L2 = 0, and the timing is cleared. If it is, the process checks if timing has not started. If it is, the first time point t = t2 is recorded, and timing begins with a duration (i.e., the length of the timing cycle) of Tk2. If not, timing has started. At the end of the second timing cycle, i.e., t = t2 + Tk2, if EGTavg1 - EGTavg2 > Degt, the second characteristic is considered true, and L2 = 1. Otherwise, the second characteristic is considered false, L2 = 0, and the timing is cleared. Here, EGTavg1 is the average exhaust temperature within the time period t2 + Tk2 - 2Dt ≤ t ≤ t2 + Tk2 - Dt, EGTavg2 is the average exhaust temperature within the time period t2 + Tk2 - Dt ≤ t ≤ t2 + Tk2, Dt is the detection period for the average exhaust temperature, and Degt is the exhaust temperature decrease threshold.

[0063] In some embodiments, the timing period length Tk2 ranges from 1 to 30 seconds, for example, Tk2 is 5 seconds or 10 seconds. In some embodiments, the exhaust temperature decrease threshold Degt ranges from 0 to 10 K, for example, Degt is 3 K or 5 K. In some embodiments, the detection period Dt for the average exhaust temperature ranges from 0.5 to 5 seconds, for example, Dt is 1 second or 2 seconds.

[0064] The judgment logic for the second feature is based on the characteristics of exhaust temperature change during engine start-up and shutdown, as shown in the following figure. Figure 7 As shown. Figure 7 The curve in the figure represents the state of exhaust temperature EGT changing with time. When the engine starts, the exhaust temperature EGT gradually increases. When the engine starts and stops, the exhaust temperature EGT decreases. When the speed change rate N2dot is lower than the threshold, the timing begins, which is t2. From t2, the exhaust temperature EGT decreases sharply. In the second timing cycle from t2 to t2+Tk2, the average exhaust temperature decreases sequentially in time within multiple consecutive detection cycles Dt.

[0065] The third feature in step 24 is: the total engine pressure ratio is less than the third threshold.

[0066] In some embodiments, the third threshold is related to engine speed. In some embodiments, the third threshold is determined by engine speed interpolation. In some embodiments, a table showing the relationship between the third threshold and engine speed is provided in advance, and the third threshold changes with engine speed. For example, the table showing the relationship between the third threshold and engine speed is stored in advance in memory. By associating the third threshold with the engine speed related to the engine's operating state, it is possible to determine whether the third characteristic is met based on the actual operating state of the engine, ensuring the reliability of the determination. Specifically, the determination logic for the third characteristic is as follows: Figure 8 As shown.

[0067] See Figure 8 Based on the engine speed N2R at the first time point, the third threshold OPR1 is determined, and the total engine pressure ratio OPR at the first time point is determined; it is then determined whether OPR is less than OPR1. If not, feature three is determined to be false, and L3 = 0; if yes, feature three is determined to be true, and L3 = 1.

[0068] The judgment logic for the third feature is based on the relationship between the engine total pressure ratio and engine speed during engine start-up and shutdown. The relationship between the engine total pressure ratio and engine speed is as follows: Figure 9 As shown. Figure 9 The normal start curve represents the relationship between the engine's total pressure ratio and engine speed during normal engine start-up. The start-up stall curve represents the relationship between the engine's total pressure ratio and engine speed during start-up stall. The start-up shutdown curve represents the relationship between the engine's total pressure ratio and engine speed during start-up shutdown. A start-up shutdown criterion curve is determined between the start-up stall curve and the start-up shutdown curve. This start-up shutdown criterion curve is the third threshold. When the engine speed is constant, if the engine's total pressure ratio is less than the third threshold, the engine will shut down during start-up.

[0069] This invention establishes multiple quantitative parameters for determining start-up and engine failure, enabling rapid response during startup and improving the timeliness of fault detection. Furthermore, it allows for storage of data during flight operations and fault analysis based on the quantitative parameters after flight completion.

[0070] The basic concepts have been described above. It is clear that the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification, especially for those skilled in the art. Furthermore, unless expressly stated in the claims, the order of elements and sequences, the use of numbers and letters, or other names in this specification are not intended to limit the order of the processes and methods described herein. Although various examples of inventive embodiments that are currently considered useful have been discussed in the foregoing disclosure, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments described herein.

Claims

1. A method of detecting misfire during start of a turbofan engine, characterized in that, The method comprises: determining an engine speed change rate; determining an exhaust temperature; determining an engine total pressure ratio, the engine total pressure ratio being related to a compressor outlet static pressure and an engine inlet total pressure; if any two of the following features are met, it is determined that the engine is started and then flameout occurs: a first feature: the engine speed change rate is less than a first threshold value; a second feature: the engine speed change rate is less than a second threshold value, and the exhaust temperature monotonically decreases; a third feature: the engine total pressure ratio is less than a third threshold value, the third threshold value being related to an engine speed.

2. The method of turbofan engine start misfire detection according to claim 1, characterized in that, if the engine speed change rate at any time point in a first time period is less than the first threshold value, it is determined that feature one is met.

3. The method of turbofan engine start misfire detection according to claim 1, wherein, if the engine speed change rate at any time point in a second time period is less than the second threshold value, and the exhaust temperature monotonically decreases in the second time period, it is determined that feature two is met.

4. The method of detecting start stall of a turbofan engine according to claim 3, wherein, if the engine speed change rate at any time point in the second time period is not less than the second threshold value, it is determined that feature two is not met.

5. The method of turbofan engine start misfire detection according to claim 1, wherein, before determining whether any two of the first feature, the second feature and the third feature are met, it is determined whether the engine is in a starting state; if it is determined that the engine is in the starting state, the determination of whether the any two features are met is started.

6. The method of turbofan engine start misfire detection according to claim 1, wherein, the engine speed change rate is a time derivative of the engine speed.

7. The method of detecting misfire during start-up of a turbofan engine according to Claim 1, wherein, the engine inlet total pressure is positively related to an atmospheric environmental pressure.

8. The method of turbofan engine start misfire detection according to Claim 1, wherein, the first threshold value is a negative value, and the first threshold value is related to a flight altitude and a Mach number.

9. The method of detecting start stall of a turbofan engine according to Claim 8, wherein, the second threshold value is greater than the first threshold value.

10. The method of detecting misfire during start-up of a turbofan engine according to Claim 1, wherein, the third threshold value is determined by an engine speed interpolation.

11. A turbofan engine start misfire detection system characterized by, The system comprises a first determining module, an obtaining module, a determining module and a determining module; wherein, the first determining module is configured to determine an engine speed change rate; the obtaining module is configured to determine an exhaust temperature; the determining module is configured to determine an engine total pressure ratio, the engine total pressure ratio being related to a compressor outlet static pressure and an engine inlet total pressure; the determining module is configured to determine whether the engine is started and then flameout occurs, based on whether any two of the following features are met: a first feature: the engine speed change rate is less than a first threshold value; a second feature: the engine speed change rate is less than a second threshold value, and the exhaust temperature monotonically decreases; a third feature: the engine total pressure ratio is less than a third threshold value, the third threshold value being related to an engine speed.

12. A turbofan engine start misfire detection apparatus characterized by, The device comprises a processor configured to execute the turbofan engine starting and flameout detection method of any one of claims 1-10.

13. A non-transitory computer-readable medium for storing instructions, the instructions comprising: The instructions, when executed by at least one processor, cause the at least one processor to implement the engine starting and flameout detection method of any one of claims 1-10.

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