A speed control method and controller based on turbojet engine rotating speed protection

Abstract

This invention discloses a speed control method and controller based on turbojet engine speed protection. The control method first generates a Mach number command calculation strategy for aircraft speed protection based on the engine speed protection threshold, and then sets the estimated cruise angle of attack and target speed N at altitude H. def A thrust and drag model for the aircraft was established, and the Mach number was calculated under the condition of thrust-drag balance, thereby adjusting the engine speed. This method ensures that the aircraft flies within the appropriate speed range and meets the time limit requirements by calculating a suitable Mach number command, thus ensuring flight safety. Flight test results have also proved the effectiveness of this method.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and in particular to a speed control method and controller based on turbojet engine speed protection. Background Technology

[0002] In the aerospace field, many aircraft rely on turbojet engines for power. These engines can adjust their speed to provide the necessary power to meet performance requirements. However, they also have limitations such as minimum and maximum operating speeds, maximum exhaust temperatures, and continuous operating time. Taking an aircraft engine as an example, based on combustion chamber flameout characteristics, the engine can accept N... defmin To N defmax The engine's operating time at different speeds is also limited; under good ventilation conditions, the speed is limited to N. def1 The following can be operated continuously at a speed of N. def1 To N def2 The continuous operating time does not exceed t1min, and the speed is within N. def2 To N defmax Under the condition of a large vehicle, the engine continuously runs for no more than t2minmin(N) defmin <N def1 <N def2 <N defmax (t1 > t2). If the limit is exceeded, there is a risk of engine shutdown, affecting the execution of the flight mission. Ensuring that the continuous engine operation time does not exceed the maximum time requirement is a key technology in aircraft speed closed-loop control. Summary of the Invention

[0003] To address the aforementioned problems, this invention aims to provide a turbojet engine speed protection speed control method and controller based on the flight Mach number command calculated from the desired rotational speed, preventing the engine from shutting down due to excessive operating time at high rotational speeds, thus ensuring flight safety.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A speed control method based on turbojet engine speed protection, characterized by comprising the following steps:

[0006] S1: When the aircraft is cruising, it generates a Mach number command calculation strategy for aircraft speed protection based on the engine speed protection threshold.

[0007] S2: Establish engine thrust and drag models;

[0008] S3: Based on the engine thrust model and drag model established in step S2, calculate the Mach number during the flight of the aircraft, and adjust and control the engine speed according to the Mach number command calculation strategy in step S1.

[0009] Furthermore, the specific operation of step S1 includes the following steps:

[0010] S101: During cruise, the aircraft operates according to the engine speed threshold N. def1 and N def2 The Mach number of the aircraft is calculated in three stages, namely...

[0011]

[0012] In the formula, N def1 N is the lower limit of engine speed. def2 N is the upper limit of engine speed. def Ma is the physical speed of the engine. c2 To calculate the Mach number instruction, Ma cs For N def <N def1 The Mach number instruction obtained by time calculation, Ma cm For N def1 <N def <N def2 The Mach number instruction obtained by time calculation, Ma cl For N def2 <N def The Mach number command obtained by time calculation;

[0013] S102: Based on the calculation results of step S101, establish the Mach number command calculation strategy for aircraft speed protection as follows:

[0014]

[0015] In the formula, Ma c For the next stage Mach number, Ma c1 This refers to the programmable Mach number.

[0016] Furthermore, the specific operation of step S2 includes the following steps:

[0017] S201: Establishing the equations of motion for the aircraft

[0018]

[0019] In the formula, m is the mass of the aircraft, v is the speed of the aircraft, t is the flight time of the aircraft, P is the thrust of the engine, X is the drag, and α, β and θ are the angle of attack, sideslip angle and trajectory inclination angle, respectively.

[0020] S202: Converts the engine's physical speed into a relative equivalent speed.

[0021]

[0022] In the formula, N cor Here, k(H) represents the relative reduced speed of the engine, and k(H) is a coefficient related to atmospheric temperature and speed of sound. The value of k(H) varies depending on the atmospheric temperature and speed of sound. Ma is the Mach number.

[0023] S203: Fitting the thrust values ​​under different engine thrust conditions yields the engine thrust model.

[0024] P(H, Ma, N) cor )=a·H+b·Ma+c·N cor +d·Ma 2

[0025] In the formula, a, b, c, and d are model reference coefficients, which have no actual physical meaning; H is the cruising altitude.

[0026] S204: Based on the aircraft motion equations and engine thrust model in step S201, the engine drag model can be obtained as follows:

[0027] D = qsC d (Ma, α)

[0028] In the formula, D is the engine drag, q is the current dynamic pressure, s is the aircraft reference area, and C... d This is the drag coefficient.

[0029] Furthermore, the specific operation of step S3 includes the following steps:

[0030] S301: By fixing the angle of attack during the steady-state phase to a single value, the drag coefficient simplifies to be dependent only on the Mach number, expressed as...

[0031] C d =e·Ma

[0032] In the formula, e is a reference coefficient;

[0033] S302: Combining the aircraft's equations of motion, thrust model, and drag model, it can be concluded that when the aircraft moves at a constant speed...

[0034]

[0035] In the formula, V yin ρ is the speed of sound, and ρ is the density of the atmosphere.

[0036] S303: Solve the expression in step S302 to obtain the corrected Mach number instruction Ma. c2Correcting the calculated Mach number instruction Ma c2 Represented as an equation

[0037] s·e·ρ·v yin 2 ·z 4 -20·d·z 3 -20·b·z 2 -20·a·H·z-20·k·c

[0038] The positive real solutions;

[0039] In the formula, k is the conversion coefficient, and z is the unknown that needs to be solved;

[0040] It should be noted here that the equation

[0041] s·e·ρ·v yin 2 ·z 4 -20·d·z 3 -20·b·z 2 -20·a·H·z-20·k·c

[0042] It is not a specific equation, but a generalized equation. By solving the equation in step S302 and substituting it into this equation, we can obtain the specific formula of the equation.

[0043] S304: Compare and correct the Mach number command obtained after the solution. c2 With programmable Mach number Ma c1 The Mach number Ma is determined in the next stage based on the Mach number instruction solution strategy. c The engine will be based on the next stage Mach number. c Adjust the rotation speed.

[0044] A speed controller based on turbojet engine speed protection is characterized by comprising a command execution system and an onboard control system for the aircraft missile, wherein the onboard control system executes the speed control method based on turbojet engine speed protection described above.

[0045] The beneficial effects of this invention are:

[0046] The speed control method based on turbojet engine speed protection in this invention can generate Mach number commands online by setting the target engine speed, flight altitude and angle of attack when the aircraft is cruising for a long time and the engine operating time is limited. The onboard control system tracks the smaller value between the programmed Mach number command and the maximum Mach number command that can be reached, so that the engine always operates in a suitable operating range, ensuring the safety of the aircraft. Attached Figure Description

[0047] Figure 1 The simulation experiment of Embodiment 1 of this invention includes the flight segment Mach number programmable command, the corrected Mach number command, and the Mach number curve.

[0048] Figure 2 The physical speed curve of the engine during the cruise phase of the aircraft in the simulation experiment of Embodiment 1 of the present invention;

[0049] Figure 3 The angle of attack curve of the aircraft during the cruise phase in the simulation experiment of Embodiment 1 of the present invention;

[0050] Figure 4 This is a block diagram of the speed controller structure in Embodiment 2 of the present invention. Detailed Implementation

[0051] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0052] Example 1

[0053] A speed control method based on turbojet engine speed protection includes the following steps:

[0054] S1: When the aircraft is cruising, it generates a Mach number command calculation strategy for aircraft speed protection based on the engine speed protection threshold.

[0055] Specifically, S101: During cruise, the aircraft adjusts its speed according to the engine speed threshold N. def1 and N def2 The Mach number of the aircraft is calculated in three stages, namely...

[0056]

[0057] In the formula, N def1 N is the lower limit of engine speed. def2 N is the upper limit of engine speed. def Ma is the physical speed of the engine. c2 To calculate the Mach number instruction, Ma cs For N def <N def1 The Mach number instruction obtained by time calculation, Ma cm For N def1 <N def <N def2 The Mach number instruction obtained by time calculation, Ma cl For N def2 <N def The Mach number command obtained by time calculation;

[0058] S102: Based on the calculation results of step S101, establish the Mach number command calculation strategy for aircraft speed protection as follows:

[0059]

[0060] In the formula, Ma c For the next stage Mach number, Ma c1 This refers to the programmable Mach number.

[0061] Furthermore, S2: Establish engine thrust and drag models;

[0062] Specifically, S201: Establishing the equations of motion for the aircraft.

[0063]

[0064] In the formula, m is the mass of the aircraft, v is the speed of the aircraft, t is the flight time of the aircraft, P is the thrust of the engine, X is the drag, and α, β and θ are the angle of attack, sideslip angle and trajectory inclination angle, respectively.

[0065] When the aircraft is in the non-maneuvering phase, its state is relatively stable, and α, β, and θ are all small quantities. As can be seen from the above equation, to maintain uniform motion, thrust should be balanced with drag.

[0066] S202: The thrust of an aero-engine is generally related to altitude, Mach number, and engine speed. In engineering practice, a thrust value table is typically obtained for different thrust conditions. The speed corresponding to this three-dimensional interpolation table is generally the relative equivalent speed N. cor Therefore, the engine's physical speed is converted into a relative equivalent speed.

[0067]

[0068] In the formula, N cor Here, k(H) represents the relative reduced speed of the engine, and k(H) is a coefficient related to atmospheric temperature and speed of sound. Different atmospheric temperatures and speeds of sound result in different k(H) values, which ultimately depend on altitude. Ma represents the Mach number.

[0069] S203: Fitting the thrust values ​​under different engine thrust conditions yields the engine thrust model.

[0070] P(H, Ma, N) cor )=a·H+b·Ma+c·N cor +d·Ma 2

[0071] In the formula, a, b, c, and d are model reference coefficients, which have no actual physical meaning; H is the cruising altitude.

[0072] S204: Based on the aircraft motion equations and engine thrust model in step S201, the engine drag model can be obtained as follows:

[0073] D = qsC d (Ma, α)

[0074] In the formula, D is the engine drag, q is the current dynamic pressure, s is the aircraft reference area, and C... d This is the drag coefficient.

[0075] Furthermore, S3: Based on the engine thrust model and drag model established in step S2, the Mach number during the flight process of the aircraft is calculated, and the speed of the engine is adjusted and controlled according to the Mach number command calculation strategy in step S1.

[0076] Based on the engine's operating status, determine the desired engine speed for the next step. If the engine is already at N... def2 To N def max If the large vehicle has been operating for nearly t2 minutes, then the next step is to reduce the engine speed to N. def2 The next step can be done in N. def1 To N def2 Select a suitable speed for the segment; if the engine is already at N... def1 To N def2 If the engine has been operating in this state for nearly t1 minutes, then the next step is to reduce the engine speed to N. def1 The following step, to ensure a high flight Mach number, can be chosen to be less than but close to N. def1 The engine speed is adjusted to ensure it can operate under this condition for an extended period. The specific operation includes the following steps:

[0077] S301: Considering that the engine thrust expression is a fitted function, it has a certain error. Furthermore, to reduce costs, some aircraft are not equipped with wind speed sensors, resulting in a certain deviation between the Mach number measured during actual flight and the windward Mach number. Therefore, the angle of attack during the steady-state phase is fixed at a relatively large value, while the calculated Mach number command is made smaller to ensure that the actual engine speed is within a safe range. When the angle of attack is fixed, the drag coefficient simplifies to be only related to the Mach number, expressed as...

[0078] C d =e·Ma

[0079] In the formula, e is a reference coefficient;

[0080] S302: Combining the aircraft's equations of motion, thrust model, and drag model, it can be concluded that when the aircraft moves at a constant speed...

[0081]

[0082] In the formula, V yinV is the speed of sound, ρ is the atmospheric density; at a constant cruising altitude, V yin And ρ are also fixed values;

[0083] S303: Solve the expression in step S302 to obtain the corrected Mach number instruction Ma. c2 Mach number instruction Ma c2 Represented as an equation

[0084] s·e·ρ·v yin 2 ·z 4 -20·d·z 3 -20·b·z 2 -20·a·H·z-20·k·c

[0085] The solution;

[0086] In the formula, k is the conversion coefficient, and z is the unknown that needs to be solved;

[0087] There are four solutions above. Generally, there are two real roots and two complex roots. The real roots are one positive and one negative. The Mach number instruction takes the positive real root.

[0088] S304: Compare and correct the Mach number command obtained after the solution. c2 With programmable Mach number Ma c1 The Mach number Ma is determined in the next stage based on the Mach number instruction solution strategy. c The engine will be based on the next stage Mach number. c Adjust the rotation speed.

[0089] Simulation experiment:

[0090] This simulation experiment uses specific numerical values ​​for simulation.

[0091] S1: When the aircraft is cruising, it generates a Mach number command calculation strategy for aircraft speed protection based on the engine speed protection threshold.

[0092] This aircraft is powered by a turbojet engine. Under good ventilation, the engine can operate continuously below 40,000 r / min; between 40,000 r / min and 43,000 r / min, the continuous operating time does not exceed 30 minutes; and between 43,000 r / min and 45,000 r / min under heavy-duty conditions, the continuous engine operating time does not exceed 5 minutes. Based on the speed protection thresholds of 40,000 r / min and 43,000 r / min, the aircraft's Mach number is calculated in three stages.

[0093]

[0094] The strategy for calculating the Mach number command for aircraft speed protection is as follows:

[0095]

[0096] S2: Establish engine thrust and drag models;

[0097] Specifically, the equations of motion for aircraft

[0098]

[0099] Convert the engine's physical speed into a relative reduced speed.

[0100]

[0101] In the above formula, atmospheric temperature T and speed of sound V yin All are determined by altitude;

[0102] The thrust values ​​under different engine thrust conditions are fitted. Since the thrust in the interpolation table is in units of large Newtons, the engine thrust model is expressed as follows:

[0103] P(H, Ma, N) cor ) = 10(-0.0127H-38.4Ma+165.6N cor +37.9Ma 2 )

[0104] The engine's drag model is expressed as:

[0105] D = qsC d (Ma, α)

[0106] S3: Based on the engine thrust model and drag model established in step S2, the Mach number actually measured during the flight of the aircraft is corrected, and the speed of the engine is adjusted and controlled according to the Mach number command solution strategy in step S1.

[0107] Assuming the engine has been operating at 43,000 to 45,000 r / min for nearly 5 minutes, the next step is to reduce the engine speed to below 43,000 r / min. 42,800 r / min is chosen as the target speed for the next stage.

[0108] Considering that the engine thrust expression is a fitted function, it has a certain error. Furthermore, there is a certain deviation between the Mach number measured during actual flight and the wind-driven Mach number. Therefore, the angle of attack during the steady-state phase is set to 4°, and the calculated Mach number command is made slightly smaller to ensure that the actual engine speed is within a safe range. When the angle of attack is fixed, the drag coefficient can be simplified to be related only to the Mach number, expressed as...

[0109] C d=0.0558Ma

[0110] Combining the aircraft's equations of motion, thrust model, and drag model, we can derive that when the aircraft is flying at a constant speed at an altitude of 8 km, we have:

[0111]

[0112] The above equation has four solutions: -0.9658, 0.7691, 0.1865-0.9798i, and 0.1865+0.9798i. Therefore, the positive real root 0.7691 is chosen as the Mach number instruction Ma. c2 . Because of Ma c1 Since the value is 0.8, which is greater than 0.7691, the next step is to select the Mach number instruction as 0.7691.

[0113] During this process, the aircraft's cruise phase Mach number programming commands, Mach number correction commands, and Mach number curves are as follows: Figure 1 As shown in the attached figure, the physical speed curve of the engine during the cruise phase of the aircraft is as follows. Figure 2 As shown in the attached figure, the angle of attack curve of the aircraft during the cruise phase is as follows. Figure 3 As shown; the aircraft first reached a speed of Mach 8km. c1 =0.8 is the programmable Mach number instruction, from Figure 2 It can be seen that from 900s onwards, the engine continuously operates at approximately 43200 r / min under heavy load conditions. Therefore, after 260s, using the Mach number calculation method of this invention, with 42800 r / min as the target speed for the next stage, and assuming a cruise angle of attack of 4° for the next stage, the Mach number is calculated. c =0.7691. From Figure 1 It can be seen that the Mach number command drops to 0.7691 at 1160s, and the engine speed drops to around 42600 r / min after 1160s. Because the cruise angle of attack is approximately 2° after the Mach number command decreases, the drag is smaller than at an angle of attack of 4°. Therefore, the actual engine speed is lower than the target speed, which ensures the engine operates normally within its safe operating range. The results show that this method is effective and has high engineering value.

[0114] Example 2:

[0115] Example 2 provides a speed controller based on turbojet engine speed protection, as shown in the attached figure. Figure 4 The system includes a command execution system and an onboard control system for the aircraft missile. The onboard control system for the aircraft missile executes the speed control method based on turbojet engine speed protection as described in Embodiment 1.

[0116] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A speed control method based on turbojet engine speed protection, characterized in that, Includes the following steps, S1: When the aircraft is cruising, it generates a Mach number command calculation strategy for aircraft speed protection based on the engine speed protection threshold. S2: Establish engine thrust and drag models; S3: Based on the engine thrust model and drag model established in step S2, calculate the Mach number during the flight of the aircraft, and adjust and control the speed of the engine according to the Mach number command calculation strategy in step S1. Step S1 includes the following steps: S101: During cruise, the aircraft operates according to the engine speed threshold. and The Mach number of the aircraft is calculated in three stages, namely... ； In the formula, This is the lower limit of engine speed. This is the upper limit of engine speed. This refers to the engine's physical rotational speed. The Mach number instruction is calculated. for The Mach number command obtained from the time calculation for The Mach number command obtained from the time calculation for The Mach number command obtained by time calculation; S102: Based on the calculation results of step S101, establish the Mach number command calculation strategy for aircraft speed protection as follows: ； In the formula, For the next stage Mach number, The programmable Mach number; Step S2 includes the following steps: S201: Establishing the equations of motion for the aircraft ； In the formula, m is the mass of the aircraft, v is the speed of the aircraft, t is the flight time of the aircraft, P is the thrust of the engine, and X is the drag. , and These are the angle of attack, sideslip angle, and trajectory inclination angle, respectively. S202: Converts the engine's physical speed into a relative equivalent speed. ； In the formula, The relative reduced speed of the engine. The coefficients are related to atmospheric temperature and speed of sound; different atmospheric temperatures and speeds of sound... Different; Ma is the Mach number; S203: Fitting the thrust values ​​under different engine thrust conditions yields the engine thrust model. ； In the formula, a, b, c, and d are model reference coefficients, which have no actual physical meaning; H is the cruising altitude. S204: Based on the aircraft motion equations and engine thrust model in step S201, the engine drag model can be obtained as follows: ； In the formula, D is the engine drag, q is the current dynamic pressure, s is the aircraft reference area, and C... d This is the drag coefficient.

2. The speed control method based on turbojet engine speed protection according to claim 1, characterized in that, Step S3 includes the following steps: S301: By fixing the angle of attack during the steady-state phase to a single value, the drag coefficient simplifies to be dependent only on the Mach number, expressed as... ； In the formula, e is a reference coefficient; S302: Combining the aircraft's equations of motion, thrust model, and drag model, it can be concluded that when the aircraft moves at a constant speed... ； In the formula, For the speed of sound, Atmospheric density; S303: Solve the expression in step S302 to obtain the corrected Mach number instruction. Correcting the calculated Mach number instruction Represented as an equation The positive real solutions; In the formula, k is the conversion coefficient, and z is the unknown that needs to be solved; S304: Compare and correct the Mach number obtained after the solution. With programmable Mach number The Mach number for the next stage is determined based on the Mach number instruction solution strategy. The engine will be based on the next stage Mach number. Adjust the rotation speed.

3. A speed controller based on turbojet engine speed protection, characterized in that: It includes a command execution system and an onboard control system for the aircraft missile, wherein the onboard control system for the aircraft missile executes the speed control method based on turbojet engine speed protection as described in claim 1.

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