A method for controlling the state of an open rotor engine (OEI) and indicating the same in a cockpit

Abstract

The application discloses a kind of OEI state control requirements and cabin indicating method of turboshaft engine, first, the mathematical model of turboshaft engine component level is established, then based on the control of the steady-state process of turboshaft engine to incremental PID algorithm and steady-state PID control method, ensure that the steady-state process of turboshaft engine under OEI state can smoothly run, in addition, the steady-state control method and OEI state control requirement of turboshaft engine under OEI state are combined, the dynamic process of turboshaft engine is controlled by the method that total distance feedforward control is combined with feedback control, ensure that turboshaft engine can smoothly run when entering OEI state, and according to engine operating state, cabin indicating requirement is formulated;The application fills the vacancy problem of current domestic turboshaft engine OEI state control law, is suitable for the control law and cabin indicating design of a variety of models turboshaft engine under OEI state, has positive promoting effect for subsequent engine health management, sensor fault diagnosis etc.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, and mainly to a turboshaft engine OEI status control requirement and cockpit indication method. Background Technology

[0002] During flight, aircraft may experience engine failure due to various factors, including inadequate fuel and air intake, engine mechanical malfunctions, cloud icing, or improper use of anti-icing systems. Airworthiness regulations require commercial aircraft to ensure that, at any point during a mission, they can safely terminate the flight without incident if one engine fails. To meet safety and airworthiness requirements, most commercial aircraft currently used internationally are equipped with two or more engines, especially large and medium-sized transport aircraft. When one engine fails, the remaining engines will provide the power required for flight.

[0003] Engine failure can occur at any stage of the flight spectrum. However, during high-power flight phases such as takeoff, catapult launch, and landing, the impact on the aircraft's overall aerodynamics and operational performance is significant, making these phases a key focus in safety analysis. For fixed-wing aircraft, given weight, gust winds, and atmospheric conditions, the runway must be of sufficient length to ensure takeoff or abort takeoff if one engine fails at a critical point in the expected takeoff trajectory. Rotary-wing aircraft / helicopters, on the other hand, typically operate vertically without sufficient runways or heliports. During high-power critical flight phases such as takeoff and landing, to ensure sufficient power for a safe landing or rapid landing after an emergency climb in the event of engine failure, the current mainstream design approach requires the remaining engine to operate in a short-term high-emergency power state. This state is usually higher than normal takeoff or maximum continuous rated power, potentially leading to damage to engine components and reduced lifespan. Therefore, there are corresponding usage restrictions and post-operation maintenance requirements for this state. This one-engine inoperative (OEI) state, used in helicopter emergency situations, is also known as the single-engine failure state.

[0004] Given the unique nature of the OEI (Out of the Air) status and its impact on helicopter flight safety, civil aviation authorities in various countries have successively added airworthiness clauses related to OEI status design, verification, use, and maintenance to their engine airworthiness regulations over the past decade or so. The Civil Aviation Administration of China (CAAC), in its 2012 "Airworthiness Regulations for Aircraft Engines" (CCAR-33-R2), comprehensively added requirements for OEI status design, verification, and airworthiness restrictions (mandatory inspection and maintenance requirements after OEI status use). Of the 53 clauses applicable to turbine engines in CCAR-33-R2, 9 relate to OEI status, with OEI appearing 68 times throughout the text. It can be said that the OEI status airworthiness requirements for helicopter engines (usually turboshaft engines) are a major difference between CCAR-33-R2 and CCAR-33-R1. Furthermore, OEI status requirements are also one of the main differences between military and civilian turboshaft engine development requirements.

[0005] Most mainstream civilian turboshaft engines on the market today have OEI rated power settings, such as the Arriel 2C, PT6-67C, and TM333 2B, which all have 30-second OEI rated power, 2-minute OEI rated power, and continuous OEI rated power settings. However, China lacks technology for determining OEI status, analyzing, verifying, and evaluating corresponding airworthiness requirements for civilian turboshaft engines, which introduces uncertainties and risks into the research and development of domestic civilian turboshaft engines. Therefore, research on OEI status control laws and cockpit indication is of great significance. Summary of the Invention

[0006] Purpose of the invention: To address the problems existing in the background technology, the present invention provides a steady-state control method and a cockpit indication method for a turboshaft engine under OEI state. Based on the nonlinear mathematical model of the turboshaft engine, the invention realizes steady-state control of the turboshaft engine under single-engine failure state. By combining collective pitch feedforward control and feedback control, the invention ensures that the turboshaft engine can operate smoothly under OEI state and formulates cockpit indication requirements according to the engine operating status.

[0007] Technical solution: To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0008] A turboshaft engine OEI state control requirement and cockpit indication method, characterized in that the OEI state control requirement is as follows:

[0009] (1) When there is at least one parameter in the engine OEI state performance parameter index whose current value is greater than or equal to the limit value for entering a certain level of OEI state, the control system will determine that the engine has entered a certain level of OEI state.

[0010] (2) During a certain level of OEI steady-state control, the engine OEI state performance parameters must not exceed the limits of the previous level OEI state; if any parameter exceeds the limit, the engine will automatically enter the previous level OEI state.

[0011] (3) In the event of a single engine failure, the OEI controller automatically releases the performance parameter restrictions of the OEI state, controls the power turbine speed to remain constant, and automatically adjusts the fuel flow increment based on the current engine power status to enable the engine to enter the corresponding OEI state.

[0012] (4) When the current values ​​of all OEI state performance parameters of the engine are lower than the current OEI state exit judgment value, the control system determines that it has exited the OEI state and stops timing.

[0013] Correspondingly, the cockpit indication method specifically includes:

[0014] Step L1: Divide the OEI status into two limit levels: 30 seconds and 2 minutes. When at least one of the engine's OEI status performance indicators exceeds the OEI status limit value of 30 seconds or 2 minutes, the engine enters the quasi-OEI status and starts timing.

[0015] Step L2: When the engine is in the 2-minute level and has been in the quasi-OEI state for more than 5 seconds, the engine officially enters the OEI state; when the engine is in the 30-second level and has been in the quasi-OEI state for more than 3 seconds, the engine officially enters the OEI state; at this time, the cockpit OEI status indicator light illuminates, and the recording of OEI state usage time begins; the OEI state usage time includes the duration of the quasi-OEI state; when the OEI state performance parameters exceed the previous level OEI limit value within a certain period of time or the engine exits the current OEI state, the quasi-OEI state duration and usage number are recorded separately.

[0016] Step L3: When the engine has been in the 30-second limit level for a certain period of time, the cockpit will issue a warning to the pilot and prompt the pilot to choose to enter the 2-minute limit level or exit the OEI state. When the engine has been in the 2-minute limit level for a certain period of time, the cockpit should warn the pilot and suggest exiting the OEI state.

[0017] Furthermore, by combining collective pitch feedforward control and feedback control, the turboshaft engine can be ensured to operate smoothly in OEI mode, and cockpit instructions can be formulated based on the engine's operating status; specifically,

[0018] The engine control system is set to a transient state upon entering the OEI state. The transient state control scheme includes collective pitch feedforward control and feedback control. The feedback control employs a cascade control system composed of a power turbine speed control loop and a gas generator speed change rate control loop, with the gas generator speed change rate n... gdot As the controlled object, the typical PID control law is as follows:

[0019] k p +K i / s+K d s

[0020] Collective pitch feedforward control employs collective pitch compensation. By predicting changes in the collective pitch lever angle and based on the mapping relationship between the collective pitch lever angle and fuel quantity, the fuel quantity command is corrected in advance, thereby accelerating the response speed of the engine output power to changes in the power required by the helicopter. The feedforward compensation value of the fuel flow rate is obtained by interpolation of the mapping curve between the rotor collective pitch angle and fuel quantity, and the fuel quantity is adjusted in real time according to this curve when the collective pitch changes.

[0021] Furthermore, once the turboshaft engine enters the OEI state, an incremental PID algorithm and a steady-state PID control method are used to control the steady-state process of the turboshaft engine, ensuring its smooth operation in the OEI state; specifically,

[0022] Step S1: Establish a component-level mathematical model of the turboshaft engine;

[0023] Step S2: The output of the incremental PID algorithm controller is the increment between the current actual value of the system control quantity and the actual value of the control quantity in the previous step, specifically expressed as:

[0024] Δu k =u(k)-u(k-1)=K p [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k+2)]

[0025] Where u(k-1) is the control variable of the system at time k-1, u(k) is the control variable of the system at time k, and Δu k K represents the control increment. p For proportional gain, The integral coefficient is... Here, e(k) represents the differential coefficient, and e(k) represents the current system error.

[0026] Step S3: The steady-state PID control method is a cascade control system, which includes an inner loop and an outer loop, each loop having its own controller; the outer loop is the power turbine speed n. pThe inner loop is the gas generator speed n. g By controlling the fuel quantity W f This causes the power turbine speed n p Tracking a given rotational speed n pd ;

[0027] When the rapid collective pitch command changes, the rotor power changes. Due to the mismatch between engine power and load, n p Significant droop or overshoot; the outer loop circuit is based on the power turbine speed setpoint n. pd The deviation from the actual value is adjusted by PID control to change the gas turbine speed command value. The control law is expressed as follows:

[0028]

[0029] The output of the outer loop controller is used as the setpoint for the inner loop, based on the gas turbine speed n. g To address the deviation, an incremental PID algorithm is used to adjust the fuel quantity W. f The control law is expressed as follows:

[0030] K p +K i / s

[0031] Meanwhile, the outer loop is equipped with an integral separation component, and the inner loop is equipped with an anti-integral saturation component, which improves the dynamic performance of the system, reduces steady-state error, and achieves steady-state control of the turboshaft engine.

[0032] Beneficial effects:

[0033] The steady-state control method and cockpit indication method for a turboshaft engine under OEI (Out of Energy) conditions provided by this invention first establishes a component-level mathematical model of the turboshaft engine. Then, based on incremental PID algorithm and steady-state PID control method, the steady-state process of the turboshaft engine is controlled to ensure stable operation of the turboshaft engine under OEI conditions. Simultaneously, combining the steady-state control method and OEI control requirements of the turboshaft engine under OEI conditions, a method combining collective pitch feedforward control and feedback control is used to ensure stable operation of the turboshaft engine under OEI conditions, and cockpit indication requirements are formulated according to the engine operating status. Attached Figure Description

[0034] Figure 1 This is a flowchart of the steady-state control method for a turboshaft engine under OEI state provided by the present invention;

[0035] Figure 2 This is the cockpit alarm logic diagram under OEI status provided by the present invention;

[0036] Figure 3This invention provides a simulation of the gas turbine rotation speed ng of a helicopter entering the OEI state for 30 seconds.

[0037] Figure 4 This invention provides a simulation of the turbine inlet temperature T45 when a helicopter enters the OEI state for 30 seconds.

[0038] Figure 5 This invention provides a simulation of the turbine rotation speed np of a helicopter entering a 30-second OEI state.

[0039] Figure 6 This invention provides a simulation of the gas turbine rotation speed ng of a helicopter entering a 2-minute OEI state.

[0040] Figure 7 This invention provides a simulation of the turbine inlet temperature T45 when a helicopter enters the OEI state for 2 minutes.

[0041] Figure 8 This invention provides a simulation of the turbine rotation speed np of a helicopter entering a 2-minute OEI state.

[0042] Figure 9 This invention provides a simulation of the gas turbine rotation speed ng of a helicopter under a combined OEI state of 30 seconds and 2 minutes.

[0043] Figure 10 This invention provides a simulation of the turbine inlet temperature T45 of a helicopter under a combined OEI state of 30 seconds and 2 minutes.

[0044] Figure 11 This invention provides a simulation of the turbine rotation speed np of a helicopter under a combined OEI state of 30 seconds and 2 minutes. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0046] This invention provides a steady-state control method and a cockpit indication method for a turboshaft engine under OEI (Out of Energy) conditions. The specific process is as follows: Figure 1 As shown.

[0047] First, a component-level mathematical model of the turboshaft engine is established. Then, the steady-state process of the turboshaft engine is controlled based on incremental PID algorithm and steady-state PID control method to ensure stable operation of the turboshaft engine under OEI conditions. Specifically,

[0048] Step S1: The output of the incremental PID algorithm controller is the increment between the actual value of the current system control quantity and the actual value of the control quantity in the previous step, specifically expressed as:

[0049] Δu k =u(k)-u(k-1)=K p [e(k)-e(k-1)]+K I e(k)+K D [e(k)-2e(k-1)+e(k+2)]

[0050] Where u(k-1) is the control variable of the system at time k-1, u(k) is the control variable of the system at time k, and Δu k K represents the control increment. p For proportional gain, The integral coefficient is... Here, e(k) represents the differential coefficient, and e(k) represents the current system error.

[0051] Step S2: The steady-state PID control method is a cascade control system, which includes an inner loop and an outer loop, each loop having its own controller; the outer loop is the power turbine speed n. p The inner loop is the gas generator speed n. g By controlling the fuel quantity W f This causes the power turbine speed n p Tracking a given rotational speed n pd ;

[0052] When the rapid collective pitch command changes, the rotor power changes. Due to the mismatch between engine power and load, n p Significant droop or overshoot; the outer loop circuit is based on the power turbine speed setpoint n. pd The deviation from the actual value is adjusted by PID control to change the gas turbine speed command value. The control law is expressed as follows:

[0053]

[0054] The output of the outer loop controller is used as the setpoint for the inner loop, based on the gas turbine speed n. g To address the deviation, PI control is used to adjust the fuel quantity W. f The control law is expressed as follows:

[0055] K p +K i / s

[0056] Meanwhile, the outer loop is equipped with an integral separation component, and the inner loop is equipped with an anti-integral saturation component, which improves the dynamic performance of the system, reduces steady-state error, and achieves steady-state control of the turboshaft engine.

[0057] Combining the steady-state control method and control requirements of the turboshaft engine under OEI state described above, a combination of collective pitch feedforward control and feedback control is used to ensure that the turboshaft engine can operate smoothly under OEI state, and to formulate cockpit instruction requirements based on the engine operating status.

[0058] The engine control system is set to a transient state upon entering the OEI state. The transient state control scheme includes collective pitch feedforward control and feedback control. The feedback control employs a cascade control system composed of a power turbine speed control loop and a gas generator speed change rate control loop, with the gas generator speed change rate n... gdot As the controlled object, the typical PID control law is as follows:

[0059] k p +K i / s+K d s

[0060] Collective pitch feedforward control employs collective pitch compensation. By predicting changes in the collective pitch lever angle and based on the mapping relationship between the collective pitch lever angle and fuel quantity, the fuel quantity command is corrected in advance, thereby accelerating the response speed of the engine output power to changes in the power required by the helicopter. The feedforward compensation value of the fuel flow rate is obtained by interpolation of the mapping curve between the rotor collective pitch angle and fuel quantity, and the fuel quantity is adjusted in real time according to this curve when the collective pitch changes.

[0061] The cockpit indication method under OEI status is based on the following OEI status control requirements:

[0062] (1) When the engine OEI state performance parameters, such as the physical speed of the gas generator, the total temperature before the power turbine, the output shaft torque, etc., have a current value greater than or equal to the limit value for entering a certain level of OEI state, the control system will identify the engine as entering a certain level of OEI state.

[0063] (2) During a certain level of OEI steady-state control, the engine OEI state performance parameters must not exceed the limits of the previous level OEI state; if any parameter exceeds the limit, the engine will automatically enter the previous level OEI state.

[0064] (3) In the event of a single engine failure, the OEI controller automatically releases the performance parameter restrictions of the OEI state, controls the power turbine speed to remain constant, and automatically adjusts the fuel flow increment based on the current engine power status to enable the engine to enter the corresponding OEI state.

[0065] (4) When the current values ​​of all OEI state performance parameters of the engine are lower than the current OEI state exit judgment value, the control system determines that it has exited the OEI state and stops timing.

[0066] Correspondingly, the cockpit indication method is as follows: Figure 2 As shown:

[0067] Step L1: Divide the OEI status into two limit levels: 30 seconds and 2 minutes. When at least one of the engine's OEI status performance indicators exceeds the OEI status limit value of 30 seconds or 2 minutes, the engine enters the quasi-OEI status and starts timing.

[0068] Step L2: When the engine is in the 2-minute level and has been in the quasi-OEI state for more than 5 seconds, the engine officially enters the OEI state; when the engine is in the 30-second level and has been in the quasi-OEI state for more than 3 seconds, the engine officially enters the OEI state; at this time, the cockpit OEI status indicator light illuminates, and the recording of OEI state usage time begins; the OEI state usage time includes the duration of the quasi-OEI state; when the OEI state performance parameters exceed the previous level OEI limit value within a certain period of time or the engine exits the current OEI state, the duration of the quasi-OEI state and the number of times it is used need to be recorded separately.

[0069] Step L3: When the engine has been in the 30-second limit level for the maximum time, the cockpit will issue a warning to the pilot and prompt the pilot to choose to enter the 2-minute limit level or exit the OEI state; when the engine has been in the 2-minute limit level for the maximum time, the cockpit should warn the pilot and suggest that he exit the OEI state as soon as possible.

[0070] To ensure the effectiveness of the control law and cockpit indication method for the turboshaft engine under OEI state designed in this invention, a specific embodiment is provided below, in which digital simulation is carried out on the control system of a certain type of engine under OEI state.

[0071] First, by increasing the engine load power, the engine's OEI state is simulated. The simulation results of various control parameters under controller adjustment in the OEI state are as follows: Figure 3-11 shown. Specifically,

[0072] like Figure 3-5 When a single engine fails, the engine control system automatically switches to a 30-second OEI state, and the gas turbine speed N... g Turbine inlet temperature T45 and power turbine speed np respond quickly, reaching the 30-second OEI state limit value and remaining within the 30-second OEI state index range. Figure 6-8 This characterizes the engine limit value as the 2-minute OEI limit value. When the engine enters the 2-minute OEI state, the gas turbine speed, turbine inlet temperature T45, and power turbine speed np respond rapidly to reach the 30-second OEI state limit value and are within the 30-second OEI state index range. Figure 9-11The engine was initially in the 30-second OEI (Out of Energy) level. After the 30-second OEI period expired, the limit level was switched to the 2-minute OEI, and the 2-minute OEI period also expired. It can be seen that the engine parameters can operate smoothly without exceeding limits under both the 30-second and 2-minute OEI states.

[0073] In summary, this invention provides a control law and cockpit indication scheme for a turboshaft engine in OEI state. When the engine enters OEI state, the engine state is automatically switched and the engine speed is automatically increased according to the engine load, so that the engine can operate smoothly in emergency situations.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cockpit indication method under the OEI state control requirements of a turboshaft engine, characterized in that, The OEI status control requirements are as follows: (1) When there is at least one parameter in the engine OEI state performance parameter index whose current value is greater than or equal to the limit value for entering a certain level of OEI state, the control system will determine that the engine has entered a certain level of OEI state. (2) During a certain level of OEI steady-state control, the engine OEI state performance parameters must not exceed the limits of the previous level of OEI state; if any parameter exceeds the limit, the engine will automatically enter the previous level of OEI state. (3) In the event of a single engine failure, the OEI controller automatically releases the performance parameter restrictions of the OEI state, controls the power turbine speed to remain constant, and automatically adjusts the fuel flow increment based on the current engine power status to enable the engine to enter the corresponding OEI state. (4) When the current values ​​of all performance parameters of the engine in each OEI state are lower than the current OEI state exit judgment value, the control system determines that it has exited the OEI state and stops timing; The cockpit indication method specifically includes: Step L1: Divide the OEI status into two limit levels: 30 seconds and 2 minutes. When at least one of the engine's OEI status performance indicators exceeds the OEI status limit value of 30 seconds or 2 minutes, the engine enters the quasi-OEI status and starts timing. Step L2: When the engine is in the 2-minute level and has been in the quasi-OEI state for more than 5 seconds, the engine officially enters the OEI state; when the engine is in the 30-second level and has been in the quasi-OEI state for more than 3 seconds, the engine officially enters the OEI state; at this time, the cockpit OEI status indicator light illuminates, and the recording of OEI state usage time begins; the OEI state usage time includes the duration of the quasi-OEI state; when the OEI state performance parameters exceed the previous level OEI limit value within a certain period of time or the engine exits the current OEI state, the quasi-OEI state duration and usage number are recorded separately. Step L3: When the engine has been in the 30-second limit level for a certain period of time, the cockpit will issue a warning to the pilot and prompt the pilot to choose to enter the 2-minute limit level or exit the OEI state. When the engine has been in the 2-minute limit level for a certain period of time, the cockpit should warn the pilot and suggest exiting the OEI state.

2. The cockpit indication method under the OEI state control requirements of a turboshaft engine according to claim 1, characterized in that, By combining collective pitch feedforward control and feedback control, the turboshaft engine can be ensured to operate smoothly in OEI state, and cockpit instruction requirements can be formulated according to the engine operating status. The engine control system is set to a transient state upon entering the OEI state. The transient state control method includes collective pitch feedforward control and feedback control. The feedback control employs a cascade control system composed of a power turbine speed control loop and a gas generator speed change rate control loop, using the gas generator speed change rate... As the controlled object, the typical PID control law is as follows: in, The proportional coefficient for PID control. For PID control, the integral coefficient is... The derivative coefficients of the PID control are... It is a complex variable; Collective pitch feedforward control employs collective pitch compensation. By predicting changes in the collective pitch lever angle and based on the mapping relationship between the collective pitch lever angle and fuel quantity, the fuel quantity command is corrected in advance, thereby accelerating the response speed of the engine output power to changes in the power required by the helicopter. The feedforward compensation value of the fuel flow rate is obtained by interpolation of the mapping curve between the rotor collective pitch angle and fuel quantity, and the fuel quantity is adjusted in real time according to this curve when the collective pitch changes.

3. The cockpit indication method under the OEI state control requirements of a turboshaft engine according to claim 1, characterized in that, Once the turboshaft engine enters the OEI state, the steady-state process of the turboshaft engine is controlled using an incremental PID algorithm and a steady-state PID control method to ensure that the turboshaft engine can operate smoothly in the OEI state. Step S1: Establish a component-level mathematical model of the turboshaft engine; Step S2: The output of the incremental PID algorithm controller is the increment between the current actual value of the system control quantity and the actual value of the control quantity in the previous step, specifically expressed as: in For the system in Control variables at time, For the system in Control variables at time, This indicates the control increment. For proportional gain, The integral coefficient is... These are the differential coefficients. This represents the current system error. Step S3: The steady-state PID control method is a cascade control system, which includes an inner loop and an outer loop, each with its own controller; the outer loop is the power turbine speed. The inner loop is the gas generator speed. By controlling the amount of fuel This increases the speed of the power turbine. Tracking a given rotational speed ; When the rapid collective pitch command changes, the rotor power changes. Due to the mismatch between engine power and load, this leads to... Significant droop or overshoot; outer loop circuit based on power turbine speed setpoint. The deviation from the actual value is adjusted by PID control to change the gas turbine speed command value. The control law is expressed as follows: in, The proportional coefficient for PID control. For PID control, the integral coefficient is... The derivative coefficients of the PID control are... It is a complex variable; The output of the outer loop controller is used as the setpoint for the inner loop, based on the gas turbine speed. To address the deviation, an incremental PID algorithm is used to adjust the fuel quantity. The control law is expressed as follows: Meanwhile, the outer loop is equipped with an integral separation component, and the inner loop is equipped with an anti-integral saturation component, which improves the dynamic performance of the system, reduces steady-state error, and achieves steady-state control of the turboshaft engine.

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