CN114856833B - Redundancy control method and device for turbofan engine with large bypass ratio - Google Patents

Redundancy control method and device for turbofan engine with large bypass ratio Download PDF

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CN114856833B
CN114856833B CN202210449449.0A CN202210449449A CN114856833B CN 114856833 B CN114856833 B CN 114856833B CN 202210449449 A CN202210449449 A CN 202210449449A CN 114856833 B CN114856833 B CN 114856833B
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control loop
engine
redundant
redundant control
fan
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CN114856833A (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

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Feedback Control In General (AREA)

Abstract

The invention provides a redundancy control method and a device for a turbofan engine with a large bypass ratio, wherein the method comprises the following steps of: determining control variables of an engine, wherein the control variables comprise a main control variable and a redundant control variable; wherein the redundant control variable is the VAFN area; designing a main control loop according to the main control variable; designing a redundant control loop according to the redundant control variable, and setting an activation logic for the redundant control loop; and outputting control instructions to control the engine to work according to the formulated 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

Redundancy control method and device for turbofan engine with large bypass ratio
Technical Field
The invention belongs to the field of aero-engines, and particularly relates to a redundancy control method and device for a turbofan engine with a large bypass ratio.
Background
The National Aviation Space Agency (NASA) has proposed an n+3 study plan in 2011, providing a technical roadmap for the development of propulsion systems for subsonic fixed-wing aircraft in 2020 to 2035. To achieve the goals set by the n+3 program, NASA also proposes its own n+3 level reference propulsion system, named AGTF30, which has the following characteristics:
for fans, the boost ratio is reduced from about 1.7 to 1.3, and the diameter of the fan reaches 2.54 meters, so that the rotating speed is lower 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 a reduction ratio of 3.1; the bypass ratio will also be further raised above 25. An adjustable geometry mechanism, called variable area fan tail jet (Variable area fan nozzle, VAFN for short), is introduced at the outlet of the outer duct, and the VAFN mechanism can change the fan boost ratio by adjusting the throat area of the outlet of the outer duct, so that the fan can work in a higher efficiency state on the premise of not causing the fan to enter a surge or blockage state.
For a core engine, the engine pressure increasing rate can reach 55 by the core engine with a brand new design, and the total temperature of the turbine inlet can be raised to more than 1800K by the introduction of ceramic matrix composite materials and advanced turbine cooling technology.
The purpose of the aeroengine control is to enable its stable and reliable operation, and to generate the desired thrust, in any environmental conditions and in any operating conditions within the declared and approved flight envelope. Since the thrust force cannot be directly measured, conventional control systems typically achieve a rotational speed (N) that is significantly linear with thrust force by controlling only the fuel flow rate 1 ) Or instruction value (EPR). The control system can calculate the current required fuel flow for any given throttle lever angle and current flight condition, and this value is typically unique.
The engine controller compares the deviation between the instruction value and the actual measurement value of the rotating speed, the PI controller with gain scheduling is used for adjusting the fuel flow, and the output fuel flow is screened by the limiting protection module and then is fed into the combustion chamber for combustion, so that the actual rotating speed value is 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.
Redundant control is created after the VAFN is introduced, and adjustment of the fan operating status point can be achieved within the full flight envelope. Taking the reduction of the area of the VAFN as an example, the working state of the outer duct can move to a critical state; static total pressure ratio of outlet position
Figure GDA0004237155970000021
Will decrease, approaching 0.5832 for critical situations; the outlet static pressure p due to the complete expansion of the outlet air flow e Let go total pressure +.>
Figure GDA0004237155970000022
Will rise; assuming no loss of flow, the total pressure of the outlet of the outer duct is the same as the total pressure of 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 achieves the fan operationAnd (5) adjusting the state point.
Thus, at a certain flight condition, a redundantly controlled engine may implement a more flexible control strategy, such as: under the condition of unchanged fan rotating speed, larger thrust output can be realized by reducing the area of the VAFN; during the transition state, the surge margin and efficiency of the fan can be regulated through the VAFN, so that the performance of the fan can be fully exerted; the controller may then select the optimal one of the combinations of speed and VAFN area.
VAFN, as a redundant control variable, creates new problems in control after introduction: because the controller is added with a control variable, N is the same under the given throttle lever angle and the flight state 1 Or EPR can be realized by controlling fuel flow and VAFN area simultaneously for N 1 Or EPR forms redundant control, so that the control speed, quality and flexibility are improved, but the existing control method can only control the main control variable and cannot be well compatible with the control of the redundant control variable.
Disclosure of Invention
In view of the above, the present invention aims to provide a redundancy control method and device for a turbofan engine with a large bypass ratio, so as to overcome the defects of the existing control method in the case of a turbofan engine with a new configuration of VAFN.
In order to achieve the above 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 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 an engine, wherein the control variables comprise a main control variable and a redundant control variable; wherein the redundant control variable is the VAFN area;
designing a main control loop according to the main control variable;
designing a redundant control loop according to the redundant control variable, and setting an activation logic for the redundant control loop; the activation logic is used for controlling the start and stop of the redundant control loop, and when the engine is in steady-state operation, the redundant control loop is closed, otherwise, the redundant control loop is opened;
and outputting control instructions to control the engine to work according to the formulated scheduling table by utilizing the main control loop and the redundant control loop.
Further, the design of the main control loop according to the main control variable includes:
selecting fuel flow as a main control variable;
a PI controller with a limiting protection module is adopted as a main control loop, wherein the output of the PI controller is shown as the following formula:
Figure GDA0004237155970000041
wherein r is i And y i Respectively represent a reference output and an actual output, K P And K I Respectively represent proportional gain and integral gain, K P And K I The two are scheduled according to the rotation speed of the fan, 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)；
wherein N is the rotation speed of the fan, H is the flying height, and MN is the flying Mach number.
Further, the designing the redundant control loop according to the redundant control variable and setting the activation logic for the redundant control loop includes:
determining a control scene of the engine, and determining activation and closing conditions of a redundant control loop according to the control scene to obtain activation logic of the redundant control loop;
determining a control target of the engine, and solving to obtain scheduling logic according to the relation between the redundant control variable and the control target;
the redundant control loop is designed according to the activation logic and the scheduling logic.
Further, the activation logic includes:
and starting a redundant control loop by adopting a function g as an activation function, and closing the redundant control loop when the value of the function g is 1, wherein the value of the function g is shown in the following formula:
Figure GDA0004237155970000042
wherein the subscript set represents a predetermined constant greater than zero,
Figure GDA0004237155970000051
representation [ T-T ] set ,t]Is>
Figure GDA0004237155970000052
The average value of (2) is called an acceleration forward average value, and the acceleration forward average value in the above are absolute values;
at the current time
Figure GDA0004237155970000053
Less than a preset threshold alpha 1,set And the acceleration forward average value is also smaller than a preset threshold value alpha 2,set When the redundant control loop is in a steady state condition, the redundant control loop is kept closed;
at the current time
Figure GDA0004237155970000054
Greater than a preset threshold alpha 1,set But the acceleration forward average value is smaller than a preset threshold value alpha 2,set When the redundant control loop is in a steady state condition, the redundant control loop is kept closed;
at the current time
Figure GDA0004237155970000055
Greater than or equal to a preset threshold alpha 1,set And the acceleration forward average value is also greater than or equal to a preset threshold value alpha 2,set When the redundant control loop is started;
at the current time
Figure GDA0004237155970000056
Less than or equal to a preset threshold alpha 1,set But the forward average value of the acceleration is larger than or equal to a preset threshold value alpha 2,set In the case, the redundancy control is returnedAnd the circuit is started, so that the redundant control loop is ensured to keep in an activated state for a certain time, and the VAFN actuating mechanism is ensured to finish the adjustment of the area of the VAFN.
Further, the preset threshold value alpha 1,set Alpha and alpha 2,set The value is required to be taken according to different control purposes; for a control scene with high requirements on rapidity and sensitivity, a preset threshold value is required to be reduced; for a control scene with higher stability requirement, the preset threshold value is required to be adjusted to be higher.
Further, the determining the control target of the engine, and solving to obtain the scheduling logic according to the relation between the redundant control variable and the control target includes:
determining that steady-state efficiency of an engine fan is optimal as a control target of the engine;
and (3) making a VAFN area control plan formula, wherein the formula is as follows:
Figure GDA0004237155970000057
wherein the h function represents the rotation speed N converted with the fan f,cor Fan efficiency, related to flight mach number MN and VAFN area, Ω refers to the set of VAFN areas that model solves for convergence;
solving a VAFN area control plan formula, wherein the solving process is as follows:
Figure GDA0004237155970000061
wherein u is in the formula A Refers to the output of a redundant control loop, A opt. Representing an optimal value; the above indicates that the output of the redundant control loop is the VAFN area where the fan efficiency is optimal in steady state, and within the set Ω, there is and only when the VAFN area is optimal the fan efficiency is highest;
operating a pneumatic thermodynamic model of the engine at a plurality of steady-state points in a fan characteristic diagram of the engine and carrying out 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 design of 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 for controlling the area of the VAFN;
determining the output of the redundant control loop to be scheduled according to the fan converted rotating speed and the flight Mach number, and formulating a redundant control loop activation formula according to the activation logic, wherein the formula is as follows:
Figure GDA0004237155970000062
wherein the fan converts the rotation speed N f,cor The flight Mach number MN is a scheduling parameter, and the function g is an activation function;
the VAFN area control plan formula and the redundant control loop activation formula are stored in a redundant control loop.
Further, the method for controlling the engine to work by using the main control loop and the redundant control loop to give out control instructions according to the formulated scheduling table comprises the following steps:
inputting the fan command rotation speed into a main control loop, and inputting the fan converted rotation speed and the flight Mach number into a redundant control loop;
acquiring a fuel instruction u output by a main control loop F ；
Acquiring area instruction u output by redundancy control loop based on VAFN area schedule A ；
By fuel command u F Sum-area instruction u A And controlling the engine to work.
Second aspect
The embodiment of the invention provides a redundancy control device of a large bypass ratio turbofan engine, which comprises the following components:
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 sensor so as to execute the large bypass ratio turbofan engine redundancy control method.
Third aspect of the invention
The invention also provides a large-bypass-ratio turbofan engine, which comprises the redundancy control device of the large-bypass-ratio turbofan engine.
Compared with the prior art, the redundancy control method and device for the large bypass ratio turbofan engine 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 an exemplary redundant control variable (VAFN area), various control purposes can be realized by formulating different redundant control targets, and the applicability of the control method and the device is improved; for redundant control variables generated by various new configurations which possibly occur in future aeroengines, corresponding controllers can be designed on the basis of the control method disclosed by the invention and used for realizing efficient control of the turbofan engine.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 is a schematic illustration of an engine configuration according to an embodiment of the present disclosure;
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 scheduling schedule according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of simulation data of control command and controlled parameter variation in an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating a simulation of a change in operating status points of a fan during an acceleration process according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a simulation of fan performance during a step response in an embodiment of the present invention;
FIG. 8 is a schematic diagram of a simulation of the overall engine performance in a step response in an embodiment of the present invention.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not 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 a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication 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 in a specific case.
The invention will be described in detail below with reference to the drawings in connection with embodiments.
Example 1
The embodiment of the invention provides a design method of a redundancy controller of a large bypass ratio turbofan engine, wherein the designed redundancy controller is formed by connecting a main control loop for controlling fuel flow and a redundancy control loop for controlling an area-adjustable fan tail spray (VAFN) in parallel, and the main control loop adopts a mature method in engineering to control loop design; whereas the activation logic and the scheduling logic are designed for the redundant control loop.
The activation logic is divided into 4 conditions, and total 8 preset parameters, so that 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 this embodiment, the generation process of the redundant control variable schedule is described by taking the fan steady-state efficiency optimization as an example, and in addition, in the practical application process, a person skilled in the art can also use the same method to generate different schedules according to different redundant control targets.
The embodiment of the invention also provides a redundancy control method of the turbofan engine with a large bypass ratio, which controls the engine through a main control loop and a redundancy control loop which are parallel, and specifically comprises the following steps:
step 101, determining control variables of an aero-engine, including a main control variable (fuel flow) and a redundant control variable (VAFN area);
step 102, firstly, designing a main control loop for a main control variable by adopting a common mature method in engineering, and selecting a proper design method to design the main control loop according to the needs of a person skilled in the art;
step 103, determining activation and closing preset conditions of a redundant control loop aiming at the area of the VAFN according to different control target scenes, wherein the conditions comprise 8 preset values of 4 conditions;
104, according to the difference of the redundant control targets, solving the redundant control variables to obtain a scheduling table of the area of the VAFN;
step 105, designing a redundant control loop according to the redundant control variable;
and 106, connecting the main control loop and the redundant control loop in parallel to form a redundant controller, and utilizing the redundant controller to give out control instructions according to a formulated scheduling table to control the engine to work.
FIG. 1 is a schematic illustration of an engine configuration according to an embodiment of the present disclosure; for example, referring to fig. 1, a new engine with a thrust rating of 30000 lbs for a trunk passenger aircraft and a civil large bypass ratio turbofan is taken as a controlled object, the configuration of the engine comprises three supercharging components and two turbine components, wherein the HPT and the HPC, the LPT and the LPC are respectively connected through a high-pressure shaft and a low-pressure shaft, the 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 rotating speed of the LPC can be increased to compress air more effectively, the rotating speed of the fan is reduced to inhibit noise and improve efficiency, and the model engine is designed for separating exhaust from the inside and the outside, wherein the VAFN is used for adjusting the throat (i.e. outlet) area of the outer bypass.
Fig. 2 is a schematic structural diagram of a redundant controller according to an embodiment of the present invention, referring to fig. 2, after analyzing a redundant control function of a VAFN area, a redundant controller of an engine with a new configuration is designed, and the structure of the redundant controller after the design is shown in fig. 2, where the redundant controller outputs a fuel flow command output by a main control loop including a fuel flow and a VAFN area command output by a redundant loop with a VAFN area, and the following formula is shown:
u＝[u F u A ] T wherein the control law of the redundant control loop takes the optimal efficiency as a design criterion; u in the above F Indicating the fuel flow command output by the main control loop, u A Representing VAFN area instructions output by 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 fuel is used as a main control loop and is designed by adopting a mature common method in engineering; the control loop with the area of the VAFN 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 affected, and only the performance of the engine is reduced, so that 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, and the existing Edmund method can be used for adjusting parameters for each design point in the envelope, so that 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 finished, a limiting protection module, such as a low-selection-high-selection module with a limiting protection function, can be added, each sub protection controller in the low-selection-high-selection module can adopt a PI controller, stable combustion of fuel in a combustion chamber is ensured, the temperature and the pressure of a key station are 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.
Wherein the output of the PI controller is generally written as:
Figure GDA0004237155970000121
wherein r is i And y i Respectively representing a reference output and an actual output, wherein the reference output is a fan command rotating speed for the fuel flow controller; for each sub-controller in the limiting protection module, the reference output is each limiting red line value under the activation condition, namely a preset fan rotating speed threshold value, and the fan rotating speed threshold value can be formulated and adjusted according to actual needs.
K in the above P And K I Respectively representing proportional gain and integral gain, both scheduled according to fan speed, altitude and mach number, as shown in the following equation:
K P ＝K P (N,H,MN)K I ＝K I (N, H, MN), wherein N is the fan speed, H is the flight altitude, and MN is the flight Mach number.
Alternatively, the redundant control loop for VAFN control may employ an open loop feedforward controller without feedback, the open loop feedforward controller output being scheduled according to fan converted speed and flight mach number as shown in the following equation:
Figure GDA0004237155970000131
conversion rotation speed N of fan f,cor And the flight Mach number MN is a scheduling parameter, the function g is an activation function, the redundant controller is activated when the value is 1, and the redundant controller is closed when the value is 0, wherein the value is represented by the following formula:
Figure GDA0004237155970000132
the subscript set in the above formula represents a predetermined constant greater than zero,
Figure GDA0004237155970000133
representation [ T-T ] set ,t]Is>
Figure GDA0004237155970000138
Is referred to as the acceleration forward average, and the acceleration and acceleration forward average are absolute values. The above equation also represents the activation and deactivation conditions of the redundant controllers, as follows:
at the current time
Figure GDA0004237155970000134
Less than a preset threshold alpha 1,set And the acceleration forward average value does not exceed the preset threshold value alpha 2,set This condition is to keep the redundant controller off in steady state conditions.
At the current time
Figure GDA0004237155970000135
Greater than a preset threshold alpha 1,set But the acceleration forward average 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 generated on the rotor due to an external disturbance.
At the current time
Figure GDA0004237155970000136
Greater than or equal to a preset threshold alpha 1,set And the acceleration forward average value is also greater 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.
At the current time
Figure GDA0004237155970000137
Less than or equal to a preset threshold alpha 1,set But the forward average value of the acceleration is larger than or equal to a preset threshold value alpha 2,set Enabling the redundant control loop to be started; after the rotating speed changes to the command value, the acceleration of the rotor falls back and is lower than a preset threshold value, and as no VAFN area sensor is fed back to the controller, the condition is to ensure that the redundant controller keeps in an activated state for a period of time, and ensure that the actuating mechanism completes the adjustment of the area.
The magnitude of the preset threshold in the activation logic can be valued according to different control purposes. In a control scene with higher requirements on rapidity and sensitivity, the preset value can be properly reduced; in the control scene with higher requirement on stability, the preset value can be properly adjusted up. In addition, it should be noted that the preset values of the above 4 conditions may be set separately, so as to improve flexibility and adaptability to various control scenarios.
In the actual application process, the purpose of setting the activation logic is as follows:
firstly, the aero-engine works at a steady state most of the time; the redundant control loop is not necessarily always in an activated state, only needs to be activated in a transitional state, and is kept closed in a steady state;
and secondly, the addition of the redundant control loop occupies the computing resource of the controller, increases the power consumption and the heating value, does not need to keep the activation output in a steady state, and is beneficial to reducing the power consumption and the heating of the redundant controller by starting the redundant control loop when required, so 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, the redundant control loop may 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 adopting the principle of optimizing steady-state efficiency, and the following steps are formulated and stored in the controller:
Figure GDA0004237155970000141
where h functions represent fan efficiency in relation to fan converted speed, flight Mach number and VAFN area, Ω refers to a set of VAFN areas that causes the model to solve for convergence; the specific solving process is as follows:
Figure GDA0004237155970000151
and operating the aerodynamic 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 values to force the fan to reach the highest efficiency at each steady-state point, and obtaining a scheduling schedule, namely a scheduling table.
Fig. 4 is a schematic diagram of a scheduling schedule according to an embodiment of the present invention, and the calculated VAFN scheduling schedule is shown in fig. 4.
It should be noted that, according to different redundancy control targets, a person skilled in the art can select different h functions according to needs to realize multiple redundancy control targets; for example, it may be determined that the redundancy control target is the steady-state thrust maximum, i.e., the h-function represents the thrust magnitude related to the fan-converted speed, the flight mach number, and the VAFN area, while the solving process is unchanged, and the solving may be performed with reference to the solving process described above.
Fig. 5 is a schematic diagram of simulation data of control command and controlled parameter variation in the embodiment of the present invention, as can be obtained from fig. 6, the rotation speed of the univariate engine may have overshoot less than 5%, the steady-state thrust same as that in the univariate state is fixed in the state of redundancy control, and the rotation speed of the fan may be reduced by more than 5%. Since the fan is the largest noise source of the engine, lower fan speeds have a significant effect on noise reduction during the take-off phase.
Fig. 6 is a schematic diagram of a simulation of a change of a fan operating state point in an acceleration process according to an embodiment of the present invention, as can be obtained from fig. 6, in an acceleration process, a fan operating point of a redundancy control engine is better matched with an optimal efficiency curve, and in contrast, due to lack of a VAFN adjusting fan operating point, a fan efficiency of a single variable engine is lower, and a surge margin is reserved too high.
FIG. 7 is a schematic diagram of a simulation of fan performance during step response in an embodiment of the present invention, as can be obtained from FIG. 7, the fan efficiency of the single variable engine begins to fluctuate for about 6 seconds, and in contrast, the VAFN area of the redundant controlled engine begins to decrease, the fan operating point is adjusted, the fan efficiency continues to rise, and the final fan efficiency is about 10% higher than that of the single variable engine.
In addition, the VAFN can adjust the fan pressure ratio to keep the fan running at high efficiency without the fan entering surge or choke. In contrast, the fan surge margin of a single variable engine is too conservative to fully exploit the fan performance.
Also, the exemplary controlled engine of the present invention is a split exhaust turbofan engine, a portion of the inner bypass inner circulating work will be transferred to the fan for increasing the kinetic energy of the outer bypass airflow and overcoming the outer bypass flow losses, since most of the thrust and flow of the large bypass ratio turbofan engine is produced by the outer bypass, there is an optimum fan pressure ratio at which the ratio of the distribution of the inner and outer bypass turbine work is optimized and the unit thrust of the engine is maximized. The fan pressure ratio of the redundant control 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%; in contrast, the maximum deviation of the single variable engine was 1.72%. The internal and external culvert circulation work distribution of the redundant control engine is more ideal, and finally the unit thrust is larger.
FIG. 8 is a schematic diagram of a simulation of the overall engine performance in a step response in an embodiment of the present invention, as can be seen from FIG. 8, where the redundantly controlled engine produces a net thrust of 10% higher than 7% higher fuel consumption. If the same steady-state thrust as in the univariate state is fixed in the state of redundant control, the engine can reduce the fuel consumption by 3.7% in the whole step process.
In addition, compared with a univariate engine, the fan efficiency of the engine with the redundancy control is higher, the throat of the outer duct is closer to a critical state, and under the condition that the steady-state rotating speeds are all the maximum takeoff thrust, the net thrust generated by the engine with the redundancy control is higher than that of the univariate engine by more than 10%.
Also, thanks to the new configuration of the VAFN, the distribution of the engine cycle work of the redundant control is more flexible, the fan pressure ratio is closer to the optimal value, and the unit thrust generated by the engine during the step process is approximately 20% higher than that of a single-variable engine.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims (8)

1. The redundancy control method of the turbofan engine with the large bypass ratio is characterized by controlling the engine through a main control loop and a redundancy control loop which are parallel, and comprises the following steps of:
determining control variables of an engine, wherein the control variables comprise a main control variable and a redundant control variable; wherein the redundant control variable is the VAFN area;
designing a main control loop according to the main control variable;
designing a redundant control loop according to the redundant control variable, and setting an activation logic for the redundant control loop; the activation logic is used for controlling the start and stop of the redundant control loop, and when the engine is in steady-state operation, the redundant control loop is closed, otherwise, the redundant control loop is opened;
the main control loop and the redundant control loop are utilized to output control instructions according to a formulated schedule to control the engine to work;
the design of the redundant control loop according to the redundant control variable and the setting of the activation logic for the redundant control loop comprise:
determining a control scene of the engine, and determining activation and closing conditions of a redundant control loop according to the control scene to obtain activation logic of the redundant control loop;
determining a control target of the engine, and solving to obtain scheduling logic according to the relation between the redundant control variable and the control target;
designing a redundant control loop according to the activation logic and the scheduling logic;
the method for determining the control target of the engine and solving to obtain scheduling logic according to the relation between the redundant control variable and the control target comprises the following steps:
determining that steady-state efficiency of an engine fan is optimal as a control target of the engine;
and (3) making a VAFN area control plan formula, wherein the formula is as follows:
Figure QLYQS_1
wherein the h function represents the rotation speed N converted with the fan f,cor Fan efficiency, related to flight mach number MN and VAFN area, Ω refers to the set of VAFN areas that model solves for convergence;
solving a VAFN area control plan formula, wherein the solving process is as follows:
Figure QLYQS_2
wherein u is in the formula A Refers to the output of a redundant control loop, A opt. Representing an optimal value; the above indicates that the output of the redundant control loop is the VAFN area where the fan efficiency is optimal in steady state, and within the set Ω, there is and only when the VAFN area is optimal the fan efficiency is highest;
operating a pneumatic thermodynamic model of the engine at a plurality of steady-state points in a fan characteristic diagram of the engine and carrying out 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.
2. The method of claim 1, wherein the designing a master control loop based on master control variables comprises:
selecting fuel flow as a main control variable;
a PI controller with a limiting protection module is adopted as a main control loop, wherein the output of the PI controller is shown as the following formula:
Figure QLYQS_3
wherein r is i And y i Respectively represent a reference output and an actual output, K P And K I Respectively represent proportional gain and integral gain, K P And K I The two are scheduled according to the rotation speed of the fan, 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)；
wherein N is the rotation speed of the fan, H is the flying height, and MN is the flying Mach number.
3. The method of claim 1, wherein the activating logic comprises:
and starting a redundant control loop by adopting a function g as an activation function, and closing the redundant control loop when the value of the function g is 1, wherein the value of the function g is shown in the following formula:
Figure QLYQS_4
wherein the subscript set represents a predetermined constant greater than zero,
Figure QLYQS_5
representation [ T-T ] set ,t]Is>
Figure QLYQS_6
The average value of (2) is called an acceleration forward average value, and the acceleration forward average value in the above are absolute values;
at the current time
Figure QLYQS_7
Less than a preset threshold alpha 1,set And the acceleration forward average value is also smaller than a preset threshold value alpha 2,set When the redundant control loop is in a steady state condition, the redundant control loop is kept closed;
at the current time
Figure QLYQS_8
Greater than a preset threshold alpha 1,set But the acceleration forward average value is smaller than a preset threshold value alpha 2,set When the redundant control loop is in a steady state condition, the redundant control loop is kept closed;
at the current time
Figure QLYQS_9
Greater than or equal to a preset threshold alpha 1,set And the acceleration forward average value is also greater than or equal to a preset threshold value alpha 2,set When the redundant control loop is started;
at the current time
Figure QLYQS_10
Less than or equal to a preset threshold alpha 1,set But the forward average value of the acceleration is larger than or equal to a preset threshold value alpha 2,set And when the redundant control loop is started, the redundant control loop is ensured to keep in an activated state for a certain time, and the VAFN actuating mechanism is ensured to finish the adjustment of the area of the VAFN.
4. A method according to claim 3, characterized in that: the preset threshold alpha 1,set Alpha and alpha 2,set The value is required to be taken according to different control purposes; for a control scene with high requirements on rapidity and sensitivity, a preset threshold value is required to be reduced; for a control scene with higher stability requirement, the preset threshold value is required to be adjusted to be higher.
5. The method of claim 1, wherein designing a redundant control loop based on the activation logic and the scheduling logic comprises:
an open loop feedforward controller without feedback is adopted as a redundant control loop for controlling the area of the VAFN;
determining the output of the redundant control loop to be scheduled according to the fan converted rotating speed and the flight Mach number, and formulating a redundant control loop activation formula according to the activation logic, wherein the formula is as follows:
Figure QLYQS_11
wherein the fan converts the rotation speed N f,cor The flight Mach number MN is a scheduling parameter, and the function g is an activation function;
the VAFN area control plan formula and the redundant control loop activation formula are stored in a redundant control loop.
6. The method of claim 5, wherein said using the primary control loop and the redundant control loop to give control instructions to control engine operation according to a formulated schedule comprises:
inputting the fan command rotation speed into a main control loop, and inputting the fan converted rotation speed and the flight Mach number into a redundant control loop;
acquiring a fuel instruction u output by a main control loop F ；
Acquiring area instruction u output by redundancy control loop based on VAFN area schedule A ；
By fuel command u F Sum-area instruction u A And controlling the engine to work.
7. A large bypass ratio turbofan engine redundancy control device, comprising:
a memory for storing executable program code;
the sensor is used for monitoring the working state of the engine;
a controller for reading executable program code stored in the memory and monitoring data of the sensor to perform the large bypass ratio turbofan engine redundancy control method of any one of claims 1-6.
8. A high bypass ratio turbofan engine comprising the high bypass ratio turbofan engine redundancy control of claim 7.
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