CN114856833A - Novel-configuration large-bypass-ratio turbofan engine redundancy control method and device - Google Patents

Novel-configuration large-bypass-ratio turbofan engine redundancy control method and device Download PDF

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CN114856833A
CN114856833A CN202210449449.0A CN202210449449A CN114856833A CN 114856833 A CN114856833 A CN 114856833A CN 202210449449 A CN202210449449 A CN 202210449449A CN 114856833 A CN114856833 A CN 114856833A
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control loop
engine
control
redundant
fan
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CN114856833B (en
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刘帅
张圣秋
王伟
杨坤
白杰
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Civil Aviation University of China
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C9/00—Controlling gas-turbine plants; Controlling fuel supply in air- breathing jet-propulsion plants
    • F02C9/48—Control of fuel supply conjointly with another control of the plant
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C9/00—Controlling gas-turbine plants; Controlling fuel supply in air- breathing jet-propulsion plants
    • F02C9/26—Control of fuel supply
    • F02C9/28—Regulating systems responsive to plant or ambient parameters, e.g. temperature, pressure, rotor speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02K—JET-PROPULSION PLANTS
    • F02K1/00—Plants characterised by the form or arrangement of the jet pipe or nozzle; Jet pipes or nozzles peculiar thereto
    • F02K1/06—Varying effective area of jet pipe or nozzle
    • F02K1/15—Control or regulation
    • F02K1/16—Control or regulation conjointly with another control
    • F02K1/17—Control or regulation conjointly with another control with control of fuel supply
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2260/00—Function
    • F05D2260/84—Redundancy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2270/00—Control
    • F05D2270/70—Type of control algorithm
    • F05D2270/705—Type of control algorithm proportional-integral
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Abstract

The invention provides a novel-configuration redundant control method and device for a turbofan engine with a large bypass ratio, wherein the method comprises the following steps of controlling the engine through a main control loop and a redundant control loop which are parallel: determining control variables of the engine, wherein the control variables comprise a main control variable and a redundancy control variable; wherein the redundant control variable is the VAFN area; designing a main control loop according to the main control variable; designing a redundancy control loop according to the redundancy control variable, and setting activation logic for the redundancy control loop; and outputting a control command to control the engine to work according to the established scheduling table by utilizing the main control loop and the redundant control loop. When the invention is applied to the turbofan engine with a new configuration, the key performance indexes of the fan and the engine can be obviously improved.

Description

Novel-configuration large-bypass-ratio turbofan engine redundancy control method and device
Technical Field
The invention belongs to the field of aircraft engines, and particularly relates to a novel-structure redundant control method and device for a turbofan engine with a large bypass ratio.
Background
The national aeronautics and astronautics administration (NASA) proposed an N +3 research project in 2011, and provides a technical route map for the development of a propulsion system for a subsonic fixed wing aircraft in 2020 to 2035. In order to achieve the goals set by the N +3 plan, NASA also proposes its own N + 3-level reference propulsion system, named AGTF30, which has the following features:
for the fan, the pressure increasing ratio is reduced to 1.3 from the current about 1.7, meanwhile, the diameter of the fan reaches 2.54 meters, and the rotating speed is lower so as to improve the efficiency, the fuel economy and reduce the noise; the fan is connected with the low-pressure rotor through a gear box with the reduction ratio of 3.1; the bypass ratio will also be further raised to above 25. An adjustable geometric mechanism, called Variable Area Fan Nozzle (VAFN), is introduced at the outlet of the bypass, and the VAFN mechanism can change the fan supercharging ratio by adjusting the throat area of the nozzle of the bypass, so that the fan can work in a high-efficiency state on the premise of not causing the fan to enter a surge or blockage state.
For the core machine, the engine pressure ratio can reach 55 due to the newly designed core machine, and the total temperature of a turbine inlet can be increased to more than 1800K due to the introduction of the ceramic matrix composite material and the advanced turbine cooling technology.
The purpose of the aircraft engine control is to enable it to operate stably and reliably and to produce the desired thrust under any ambient conditions and any operating conditions within the declared and approved flight envelope. Since thrust cannot be directly measured, conventional control systems typically achieve a speed (N) that is significantly linear with thrust by controlling fuel flow only 1 ) Or an instruction value (EPR). For any given throttle lever angle and current flight condition, the control system can calculate the current required fuel flow, and this value is usually unique.
And comparing the deviation value between the instruction value and the measured value of the rotating speed by the engine controller, adjusting the fuel flow by using a PI controller with gain scheduling, screening the output fuel flow by a limit protection module, and feeding the screened output fuel flow into a combustion chamber for combustion so as to enable the actual rotating speed value to be the same as the instruction value. However, in this process, the working state point of the fan can only move along the designed track, and cannot be flexibly adjusted.
After the VAFN is introduced, redundant control is generated, and the adjustment of the working state point of the fan can be realized in a full flight envelope. Taking the VAFN area reduction as an example, the working state of the outer duct moves to a critical state; static to total pressure ratio at the outlet
Figure BDA0003618032230000021
Will decrease, approaching 0.5832 for the critical case; outlet static pressure p due to full expansion of outlet gas flow e Const, so the total outlet pressure
Figure BDA0003618032230000022
Will rise; assuming no loss of flow, the total pressure at the outlet of the outer duct is the same as the total pressure at the outlet of the fan; eventually causing the fan pressure ratio to rise. Similarly, the fan pressure ratio decreases as the VAFN area increases. This enables adjustment of the fan operating condition point.
Redundant control of the engines can then enable more flexible control strategies at a given flight condition, such as: under the condition of unchanged fan rotating speed, larger thrust output can be realized by reducing the VAFN area; in a transition state, the surge margin and efficiency of the fan can be adjusted through the VAFN, and the performance of the fan is fully exerted; the controller may then select the optimum one of the combinations of rotational speed and VAFN area.
VAFN, as a redundant control variable, introduces a new control problem: since the controller adds a control variable, N for a given throttle lever angle and flight condition 1 Or EPR can be realized by controlling the fuel flow and the VAFN area at the same time, for N 1 Or EPR forms redundant control, thereby improving the control speed, quality and flexibility, but the existing control method can only realize the control of the main control variable and can not be well compatible with the control of the redundant control variable.
Disclosure of Invention
In view of the above, the present invention is directed to a method and a device for controlling redundancy of a new-type turbofan engine with a large bypass ratio, so as to overcome the disadvantages of the existing control method in the VAFN of the new-type turbofan engine.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
first aspect
The embodiment of the invention provides a redundancy control method of a turbofan engine with a new configuration and a large bypass ratio, which controls the engine through a main control loop and a redundancy control loop which are parallel and comprises the following steps:
determining control variables of the engine, wherein the control variables comprise a main control variable and a redundancy control variable; wherein the redundant control variable is the VAFN area;
designing a main control loop according to the main control variable;
designing a redundancy control loop according to the redundancy control variable, and setting activation logic for the redundancy control loop; the activation logic is used for controlling the opening and closing of the redundancy control loop, when the engine works in a steady state, the redundancy control loop is closed, otherwise, the redundancy control loop is opened;
and outputting a control command to control the engine to work according to the established scheduling table by utilizing the main control loop and the redundant control loop.
Further, designing a master control loop according to the master control variable includes:
selecting fuel flow as a main control variable;
adopting a PI controller with a limit protection module as a main control loop, wherein the output of the PI controller is shown as the following formula:
Figure BDA0003618032230000041
wherein r is i And y i Respectively representing a reference output and an actual output, K P And K I Respectively representing proportional and integral gains, K P And K I The two are scheduled according to the fan rotating speed, the flying height and the flying Mach number, and the following formula is shown:
K P ＝K P (N,H,MN)；K I ＝K I (N,H,MN)；
where N is the fan speed, H is the flight altitude, and MN is the flight Mach number.
Further, designing a redundancy control loop according to the redundancy control variable, and setting an activation logic for the redundancy control loop includes:
determining a control scene of the engine, and determining the activation and closing conditions of the redundant control loop according to the control scene to obtain the activation logic of the redundant control loop;
determining a control target of the engine, and solving to obtain a scheduling logic according to the relation between the redundant control variable and the control target;
the redundant control loops are designed according to the activation logic and the scheduling logic.
Further, the activation logic includes:
the method comprises the following steps of starting a redundancy control loop when a function g is taken as an activation function and is taken as 1, closing the redundancy control loop when the function g is taken as 0, wherein the function g takes the following value:
Figure BDA0003618032230000042
wherein the subscript set in the formula represents a predetermined constant greater than zero,
Figure BDA0003618032230000051
represents [ T-T set ,t]Within a time range of
Figure BDA0003618032230000052
The average value of (1) is called an acceleration forward average value, and the acceleration forward average value in the formula are absolute values;
current time of day
Figure BDA0003618032230000053
Less than a predetermined threshold value alpha 1,set And the acceleration forward mean value does not exceed the preset threshold value alpha 2,set Then make the redundancy control backThe way remains closed under steady state conditions;
current time of day
Figure BDA0003618032230000054
Greater than a preset threshold value alpha 1,set But the acceleration forward mean value does not exceed the preset threshold value alpha 2,set When the redundancy control loop is closed, the redundancy control loop is kept closed under the steady state condition;
current time of day
Figure BDA0003618032230000055
Greater than or equal to a preset threshold value alpha 1,set And the acceleration forward mean value is also more than or equal to a preset threshold value alpha 2,set When the redundancy control loop is started, the redundancy control loop is started;
current time of day
Figure BDA0003618032230000056
Less than or equal to a preset threshold value alpha 1,set But the acceleration forward mean value is more than or equal to a preset threshold value alpha 2,set And starting the redundant control loop to ensure that the redundant control loop continues to keep an activation state for a certain time and ensure that the VAFN actuating mechanism completes the adjustment of the VAFN area.
Further, the preset threshold value alpha 1,set And alpha 2,set Values need to be taken according to different control purposes; for a control scene with higher requirements on rapidity and sensitivity, a preset threshold value needs to be reduced; for a control scene with a high requirement on stability, the preset threshold value needs to be increased.
Further, the determining a control target of the engine and solving to obtain a scheduling logic according to a relationship between the redundant control variable and the control target includes:
determining that the steady-state efficiency of an engine fan is optimal as a control target of the engine;
a VAFN area control plan formula is formulated as follows:
Figure BDA0003618032230000057
wherein the h function represents the fan converted speed N f,cor Fan efficiency related to the flight mach number MN and VAFN area, Ω refers to the VAFN area set that makes the model solve convergence;
solving the VAFN area control plan formula, wherein the solving process is as follows:
Figure BDA0003618032230000061
wherein u in the formula A Refers to the output of the redundant control loop, A opt. Represents an optimal value; the above equation indicates that the output of the redundant control loop is the VAFN area when the fan efficiency is optimal in the steady state, and within the set Ω, the fan efficiency is highest sometimes and only when the VAFN area is optimal;
operating a pneumatic thermal model of the engine at a plurality of steady-state points in an engine fan characteristic diagram and performing iterative solution to obtain corresponding fan efficiency values;
and adjusting the area value of the VAFN to ensure that the engine fan reaches the highest efficiency at each steady-state point, and obtaining the scheduling logic, namely a scheduling table, of the VAFN under each flight condition.
Further, the designing the redundant control loop according to the activation logic and the scheduling logic includes:
an open-loop feedforward controller without feedback is adopted as a redundant control loop aiming at the control of the VAFN area;
determining the output of the redundancy control loop to be scheduled according to the converted rotating speed of the fan and the flight Mach number, and formulating an activation formula of the redundancy control loop according to activation logic, wherein the activation formula is shown as the following formula:
Figure BDA0003618032230000062
wherein the fan converts the rotating speed N f,cor The flight Mach number MN is a scheduling parameter, and the function g is an activation function;
storing the VAFN area control plan formula and a redundant control loop activation formula in a redundant control loop.
Further, the control of the engine by using the main control loop and the redundant control loop to give control commands according to the formulated schedule table comprises:
inputting the fan instruction rotating speed into a main control loop, and inputting the fan conversion rotating speed and the flight Mach number into a redundancy control loop;
acquiring a fuel instruction u output by a main control loop F ；
Obtaining area instruction u output by redundant control loop based on VAFN area scheduling table A ；
Using fuel command u F And area instruction u A And controlling the engine to work.
Second aspect of the invention
The embodiment of the invention provides a novel-configuration redundancy control device for a turbofan engine with a large bypass ratio, which comprises:
a memory for storing executable program code;
the sensor is used for monitoring the working state of the engine;
and the controller is used for reading the executable program codes stored in the memory and the monitoring data of the sensors so as to execute the redundancy control method of the turbofan engine with the large bypass ratio in the new configuration.
Third aspect of the invention
The invention also provides a new-configuration large-bypass-ratio turbofan engine which comprises the new-configuration large-bypass-ratio turbofan engine redundancy control device.
Compared with the prior art, the redundancy control method and device for the turbofan engine with the novel structure and the large bypass ratio have the following advantages:
when the invention is applied to the turbofan engine with a new configuration, the key performance indexes of the fan and the engine can be obviously improved; for the redundancy control variable (VAFN area) of the example, various control purposes can be realized by formulating different redundancy control targets, and the applicability of the control method and the control device is improved; for redundant control variables generated by various new configurations which may appear in future aeroengines, corresponding controllers can be designed on the basis of the control method disclosed by the invention, and the redundant control variables are used for realizing the efficient control of the turbofan engine.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is a schematic diagram of an engine configuration according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a redundant controller according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a redundant control loop according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a dispatch schedule according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of simulation data of changes in control commands and controlled parameters according to an embodiment of the present invention;
FIG. 6 is a simulation diagram illustrating an accelerated process fan operating condition point change according to an embodiment of the present invention;
FIG. 7 is a simulation diagram illustrating fan performance during a step response process according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a simulation of the overall performance of an engine in a step response according to an embodiment of the present invention.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate a number of the indicated technical features. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Example 1
The embodiment of the invention provides a design method of a newly-configured large bypass ratio turbofan engine redundancy controller, wherein the designed redundancy controller is formed by connecting a main control loop for controlling fuel flow and a redundancy control loop for controlling variable area fan tail injection (VAFN) in parallel, wherein the main control loop adopts a mature engineering method to design a control loop; and activation logic and scheduling logic are designed for the redundant control loops.
Illustratively, the activation logic is divided into 4 conditions and 8 preset parameters in total, and in the actual application process, a person skilled in the art can flexibly select the conditions and the preset parameters according to different control scenes; in addition, in the actual application process, a person skilled in the art can also use the same method to generate different schedules according to different redundancy control targets.
The embodiment of the invention also provides a novel structural redundancy control method for the turbofan engine with the large bypass ratio, the engine is controlled by the parallel main control loop and the redundancy control loop, and the method specifically comprises the following steps:
step 101, determining control variables of an aircraft engine, including a main control variable (fuel flow) and a redundant control variable (VAFN area);
102, designing a master control loop for a master control variable by adopting a common mature method in engineering, wherein a person skilled in the art can select a proper design method to design the master control loop according to needs;
103, determining preset conditions for activating and closing a redundant control loop aiming at the VAFN area according to different control target scenes, wherein the preset conditions comprise 8 preset values of 4 conditions;
104, solving the redundancy control variable according to different redundancy control targets to obtain a VAFN area scheduling table;
105, designing a redundancy control loop according to the redundancy control variable;
and 106, connecting the main control loop and the redundant control loop in parallel to form a redundant controller, and giving a control instruction to control the engine to work by using the redundant controller according to the formulated scheduling table.
FIG. 1 is a schematic diagram of an engine configuration according to an embodiment of the present invention; for example, referring to fig. 1, a 30000-pound thrust class civil high bypass ratio turbofan new-type engine for a trunk passenger bus is taken as a controlled object, the configuration of the engine comprises three supercharging components and two turbine components, wherein an HPT, an HPC, an LPT and an LPC are respectively connected with a high-pressure shaft and a low-pressure shaft, a fan is not directly connected with the low-pressure shaft, but is connected with the low-pressure shaft through a reduction gearbox with a transmission ratio of 3.1, the rotation speed of the LPC can be increased to compress air more efficiently, the rotation speed of the fan is reduced to inhibit noise and improve efficiency, the model engine is designed for internal and external bypass separate exhaust, and a VAFN is used for adjusting the throat (outlet) area of an external bypass.
Fig. 2 is a schematic structural diagram of a redundant controller according to an embodiment of the present invention, and referring to fig. 2, after analyzing a redundant control function of a VAFN area, a redundant controller of a new configuration engine is designed, and a structure of the designed redundant controller is shown in fig. 2, where the redundant controller outputs a fuel flow instruction output by a main control loop including a fuel flow and a VAFN area instruction output by a redundant loop including a VAFN area, as shown in the following formula:
u＝[u F u A ] T the control law of the redundant control loop takes the optimal efficiency as a design criterion; in the above formula u F Indicating fuel flow command, u, output by the main control circuit A A VAFN area command indicating the output of the redundant control loop.
The redundant control loop and the main control loop are connected in parallel to form the redundant controller, wherein the main control loop for controlling the fuel oil is used as a main control loop and is still designed by adopting a method mature and common in engineering; the control loop of the VAFN area is a redundant control loop, and in the actual operation process, even if the redundant control loop fails, the operation of the engine is not influenced, only the performance of the engine is reduced, and the stability and the reliability of the engine under the control of the control method are improved.
In the practical application process, a PI controller can be adopted as a fuel flow controller for controlling the fuel flow, the existing Edmund method can be used for parameter adjustment for each design point in a envelope, and the second-order transfer function of an engine system matched with the fuel flow controller is ensured to have amplitude-frequency margin and phase margin which are respectively larger than 6dB and 45 degrees.
Optionally, after the design of the fuel flow controller is completed, a limiting protection module, such as a low-selection-high-selection module with a limiting protection function, may be added, each sub-protection controller in the low-selection-high-selection module may adopt a PI controller, so as to ensure that the fuel is stably combusted in the combustion chamber, the temperature and pressure of the key station is not over-limited, and the fuel flow controller and the low-selection-high-selection module with the limiting protection function are connected in series to form a main control loop.
The output of the PI controller is generally written as follows:
Figure BDA0003618032230000121
wherein r is i And y i Respectively representing a reference output and an actual output, wherein for the fuel flow controller, the reference output is a fan instruction rotating speed; for each sub-controller within the limit protection module, the reference output is each limit red line value, i.e. a pre-established fan speed threshold, which can be established and adjusted according to actual needs, in the case of activation.
In the above formula K P And K I The proportional gain and the integral gain are respectively expressed, and are scheduled according to the fan rotating speed, the flying height and the Mach number, and the following formula is shown:
K P ＝K P (N,H,MN)K I ＝K I (N, H, MN, where N is the fan speed, H is the flight altitude, and MN is the flight Mach number.
Optionally, a redundant control loop for VAFN control may employ an open-loop feedforward controller without feedback, where the output of the open-loop feedforward controller is scheduled according to the converted rotation speed of the fan and the flight mach number, as shown in the following formula:
Figure BDA0003618032230000131
fan conversion speed N in fan f,cor And the flight Mach number MN is a scheduling parameter, the function g is an activation function, the redundancy controller is activated when the value 1 is obtained, the redundancy controller is closed when the value 0 is obtained, and the value is represented by the following formula:
Figure BDA0003618032230000132
in the above formula the subscript set denotes a predetermined constant greater than zero,
Figure BDA0003618032230000133
represents [ T-T set ,t]Within a time range of
Figure BDA0003618032230000134
All areThe value is called the acceleration forward mean, and the acceleration and acceleration forward mean are absolute values in the formula. The above equation also represents the activation and deactivation conditions for the redundant controllers, as described in detail below:
current time of day
Figure BDA0003618032230000135
Less than a predetermined threshold value alpha 1,set And the acceleration forward mean value does not exceed the preset threshold value alpha 2,set This condition is to keep the redundant controller off in a steady state situation.
Current time of day
Figure BDA0003618032230000136
Greater than a preset threshold value alpha 1,set But the acceleration forward mean value does not exceed the preset threshold value alpha 2,set Keeping the redundant control loop closed under steady state conditions; this condition is to prevent the redundant controller from being repeatedly activated by an acceleration error on the rotor due to an external disturbance.
Current time of day
Figure BDA0003618032230000137
Greater than or equal to a preset threshold value alpha 1,set And the acceleration forward mean value is also more than or equal to a preset threshold value alpha 2,set Enabling the redundant control loop to be started; this condition is to have the redundant controller activated in the transition state.
Current time of day
Figure BDA0003618032230000138
Less than or equal to a preset threshold value alpha 1,set But the acceleration forward mean value is more than or equal to the preset threshold value alpha 2,set Enabling the redundant control loop to be started; when the rotating speed is changed to a command value, the acceleration of the rotor drops back and is lower than a preset threshold value, and no VAFN area sensor feeds back to the controller, so that the condition is that the redundant controller is ensured to continuously keep an activated state for a period of time, and the actuating mechanism is ensured to finish the area adjustment.
The preset threshold in the activation logic may be a value according to different control objectives. If in a control scene with higher requirements on rapidity and sensitivity, the preset value can be properly reduced; in a control scenario with a high requirement on stability, the preset value can be properly increased. It should be noted that the preset values of the above 4 conditions can be set respectively, so as to improve the flexible adaptability to various control scenarios.
In the practical application process, the purpose of setting the activation logic is as follows:
firstly, the aero-engine works in a steady state in most of the time; the redundant control loop is not required to be in an active state all the time, and only needs to be activated in a transition state and kept closed in a steady state;
and secondly, the addition of the redundant control loop occupies the calculation resource of the controller, increases the power consumption and the heat productivity, does not need to keep activated output in a steady state, and is beneficial to reducing the power consumption and the heat productivity of the redundant controller by starting the redundant control loop when needed, thereby ensuring that the redundant controller can continuously and stably work.
Fig. 3 is a schematic structural diagram of a redundant control loop according to an embodiment of the present invention, and referring to fig. 3, a redundant control loop can be finally designed by setting an activation logic of the redundant control loop.
In the redundant control loop, the VAFN area control plan is designed by using the principle of optimizing the steady-state efficiency, and the following formula is formulated and stored in the controller:
Figure BDA0003618032230000141
in the formula, h function represents fan efficiency related to fan conversion rotating speed, flight Mach number and VAFN area, wherein omega refers to a VAFN area set enabling a model to solve convergence; the specific solving process is shown as the following formula:
Figure BDA0003618032230000151
and operating the pneumatic thermal model of the engine at a plurality of steady-state points in the fan characteristic diagram and carrying out iterative solution to obtain corresponding fan efficiency values, then adjusting the VAFN area value to force the fan to achieve the highest efficiency at each steady-state point, and obtaining a scheduling schedule table, namely a scheduling table.
Fig. 4 is a schematic diagram of a scheduling schedule according to an embodiment of the present invention, and the obtained VAFN scheduling schedule is shown in fig. 4.
It should be noted that, according to the difference of the redundancy control targets, a person skilled in the art may also select different h functions as needed to achieve multiple redundancy control targets; for example, the redundant control target may be determined to be a steady-state thrust maximum, i.e., the h-function represents the magnitude of thrust associated with the fan converted speed, flight mach number, and VAFN area, and the solving process may be performed without change, and may be referred to as the solving process described above.
Fig. 5 is a schematic diagram of simulation data of control commands and controlled parameter changes in the embodiment of the present invention, and it can be obtained from fig. 6 that the rotational speed of the univariate engine is overshot by less than 5%, the same steady-state thrust as that in the univariate state is fixed in the state of redundant control, and the rotational speed of the fan can be reduced by more than 5%. Because the fan is the largest noise source of the engine, the lower fan rotating speed has obvious effect on noise reduction in the takeoff stage.
Fig. 6 is a simulation diagram of the change of the operating point of the fan during the acceleration process according to the embodiment of the present invention, and it can be obtained from fig. 6 that the operating point of the fan of the redundancy control engine is better matched with the optimal efficiency curve during the acceleration process, for comparison, because the operating point of the fan is not adjusted by VAFN, the fan efficiency of the univariate engine is lower, and the surge margin is too high.
Fig. 7 is a simulation diagram of fan performance during the step response process in the embodiment of the present invention, and it can be obtained from fig. 7 that the fan efficiency of the univariate engine starts to fluctuate and decrease at about 6s, by contrast, the VAFN area of the redundantly controlled engine starts to decrease, the fan operating state point is adjusted to make the fan efficiency continue to increase, and finally the fan efficiency is about 10% higher than that of the univariate engine.
Additionally, the VAFN may adjust the fan pressure ratio to keep the fan running at high efficiency without the fan entering surge or blockage. In contrast, the fan surge margin of a univariate engine is too conservative to fully exploit fan performance.
Also, the exemplary controlled engine of the present invention is a split exhaust turbofan engine, and a portion of the inner ducted internal circulation work is transferred to the fan for increasing the kinetic energy of the bypass airflow and overcoming bypass flow losses, and since most of the thrust and flow of the turbofan engine with a large bypass ratio is generated by the bypass, there is an optimum fan pressure ratio at which the ratio of turbine work distribution between the inner and outer ducts is optimized and the engine specific thrust is maximized. The fan pressure ratio of the redundantly controlled engine is better matched with the corresponding optimal pressure ratio, and the maximum deviation of the fan pressure ratio and the optimal pressure ratio in the step process is 1.31 percent; for comparison, the maximum deviation for a univariate engine is 1.72%. The internal and external bypass circulation power distribution of the engine with the redundant control is more ideal, and finally the unit thrust of the engine is larger.
Fig. 8 is a simulation of the overall performance of the engine in step response according to an embodiment of the present invention, and as can be seen from fig. 8, the redundantly controlled engine produces a net thrust that is 10% higher at the expense of a 7% higher fuel consumption. If the same steady-state thrust force as that in the single variable state is fixed in the state of redundant control, the fuel consumption of the engine can be reduced by 3.7% in the whole step process.
In addition, compared with a single variable engine, the fan efficiency of the engine under the redundant control is higher, the throat part of the outer bypass is closer to a critical state, and the net thrust generated by the engine under the redundant control is higher than that of the single variable engine by more than 10% under the condition that the steady-state rotating speeds are the maximum takeoff thrust.
Also, thanks to the new configuration of VAFN, the redundantly controlled engine cycle work is more flexibly distributed and regulated between the inner and outer culverts, the fan pressure ratio is closer to the optimum value, and the unit thrust generated by the engine during the step change process is higher than that of the univariate engine by nearly 20%.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. A novel configuration redundancy control method for a turbofan engine with a large bypass ratio is characterized in that the engine is controlled by a main control loop and a redundancy control loop which are parallel, and the redundancy control method comprises the following steps:
determining control variables of the engine, wherein the control variables comprise a main control variable and a redundancy control variable; wherein the redundant control variable is the VAFN area;
designing a main control loop according to the main control variable;
designing a redundancy control loop according to the redundancy control variable, and setting activation logic for the redundancy control loop; the activation logic is used for controlling the opening and closing of the redundancy control loop, when the engine works in a steady state, the redundancy control loop is closed, otherwise, the redundancy control loop is opened;
and outputting a control command to control the engine to work according to the formulated scheduling table by utilizing the main control loop and the redundant control loop.
2. The method of claim 1, wherein designing the master control loop according to master variables comprises:
selecting fuel flow as a main control variable;
adopting a PI controller with a limit protection module as a main control loop, wherein the output of the PI controller is shown as the following formula:
Figure FDA0003618032220000011
wherein r is i And y i Respectively representing a reference output and an actual output, K P And K I Respectively representing proportional and integral gains, K P And K I The two are scheduled according to the fan rotating speed, the flight altitude and the flight Mach number, and the following formula is shown:
K P ＝K P (N,H,MN)；K I ＝K I (N,H,MN)；
where N is the fan speed, H is the flight altitude, and MN is the flight Mach number.
3. The method of claim 1, wherein designing a redundant control loop based on the redundant control variable and setting activation logic for the redundant control loop comprises:
determining a control scene of the engine, and determining the activation and closing conditions of the redundant control loop according to the control scene to obtain the activation logic of the redundant control loop;
determining a control target of the engine, and solving to obtain a scheduling logic according to the relation between the redundant control variable and the control target;
the redundant control loops are designed according to the activation logic and the scheduling logic.
4. The method of claim 3, wherein the activation logic comprises:
the method comprises the following steps of starting a redundancy control loop when a function g is taken as an activation function and is taken as 1, closing the redundancy control loop when the function g is taken as 0, wherein the function g takes the following value:
Figure FDA0003618032220000021
wherein the subscript set in the formula represents a predetermined constant greater than zero,
Figure FDA0003618032220000022
represents [ T-T set ,t]Within a time range of
Figure FDA0003618032220000023
The average value of (1) is called an acceleration forward average value, and the acceleration forward average value in the formula are absolute values;
current time of day
Figure FDA0003618032220000024
Less than a predetermined threshold value alpha 1,set And the acceleration forward mean value does not exceed the preset threshold value alpha 2,set In time, the redundant control loop remains closed under steady state conditions;
current time of day
Figure FDA0003618032220000025
Greater than a preset threshold value alpha 1,set But the acceleration forward mean value does not exceed the preset threshold value alpha 2,set In time, the redundant control loop remains closed under steady state conditions;
current time of day
Figure FDA0003618032220000026
Greater than or equal to a preset threshold value alpha 1,set And the acceleration forward mean value is also more than or equal to a preset threshold value alpha 2,set When the redundancy control loop is started, the redundancy control loop is started;
current time of day
Figure FDA0003618032220000031
Less than or equal to a preset threshold value alpha 1,set But the acceleration forward mean value is more than or equal to a preset threshold value alpha 2,set And starting the redundant control loop to ensure that the redundant control loop continues to keep an activation state for a certain time and ensure that the VAFN actuating mechanism completes the adjustment of the VAFN area.
5. The method of claim 4, wherein: the preset threshold value alpha 1,set And alpha 2,set Values need to be taken according to different control purposes; for a control scene with higher requirements on rapidity and sensitivity, a preset threshold value needs to be reduced; for a control scene with a high requirement on stability, the preset threshold value needs to be increased.
6. The method of claim 3, wherein determining a control objective for the engine and solving for the scheduling logic based on the relationship between the redundant control variables and the control objective comprises:
determining that the steady-state efficiency of an engine fan is optimal as a control target of the engine;
a VAFN area control plan formula is formulated as follows:
Figure FDA0003618032220000032
wherein the h function represents the fan converted speed N f,cor Fan efficiency related to the flight mach number MN and VAFN area, Ω refers to the VAFN area set that makes the model solve convergence;
solving the VAFN area control plan formula, wherein the solving process is as follows:
Figure FDA0003618032220000033
wherein u in the formula A Refers to the output of the redundant control loop, A opt. Represents an optimal value; the above equation indicates that the output of the redundant control loop is the VAFN area at which the fan efficiency is optimal in the steady state, and within the set Ω, the fan efficiency is highest, and only if the VAFN area is optimal;
operating a pneumatic thermal model of the engine at a plurality of steady-state points in an engine fan characteristic diagram and performing iterative solution to obtain corresponding fan efficiency values;
and adjusting the area value of the VAFN to ensure that the engine fan reaches the highest efficiency at each steady-state point, and obtaining the scheduling logic, namely a scheduling table, of the VAFN under various flight conditions.
7. The method of claim 6, wherein designing a redundant control loop based on activation logic and scheduling logic comprises:
an open-loop feedforward controller without feedback is adopted as a redundant control loop aiming at the control of the VAFN area;
determining the output of the redundancy control loop to be scheduled according to the converted rotating speed of the fan and the flight Mach number, and formulating an activation formula of the redundancy control loop according to activation logic, wherein the activation formula is shown as the following formula:
Figure FDA0003618032220000041
wherein the fan converts the rotating speed N f,cor The flight Mach number MN is a scheduling parameter, and the function g is an activation function;
storing the VAFN area control plan formula and a redundant control loop activation formula in a redundant control loop.
8. The method of claim 7, wherein said using the primary control loop and the redundant control loop to provide control commands according to a programmed schedule to control engine operation comprises:
inputting the fan instruction rotating speed into a main control loop, and inputting the fan conversion rotating speed and the flight Mach number into a redundancy control loop;
acquiring a fuel instruction u output by a main control loop F ；
Obtaining area instruction u output by redundant control loop based on VAFN area scheduling table A ；
Using fuel command u F And area instruction u A And controlling the engine to work.
9. A new configuration of a large bypass ratio turbofan engine redundancy control apparatus, comprising:
a memory for storing executable program code;
the sensor is used for monitoring the working state of the engine;
and the controller is used for reading the executable program codes stored in the memory and the monitoring data of the sensors so as to execute the redundancy control method of the turbofan engine with the large bypass ratio in the new configuration.
10. A new configuration of high bypass ratio turbofan engine comprising the new configuration of high bypass ratio turbofan engine redundant control apparatus as claimed in claim 9.
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