CN104564354A - Aero-engine service life prolonging controller designing method - Google Patents

Abstract

The invention discloses a design method for an aero-engine life extension controller. By adding a high-pressure rotor acceleration limit in the aero-engine control system, the index representing the life of the aero-engine and the index representing performance are simultaneously incorporated into the optimization objective function, and the genetic The algorithm optimizes the acceleration limit, so that the controller prolongs the life of the aero-engine while ensuring that the acceleration performance of the aero-engine remains unchanged or only slightly decreases, effectively prolonging the life of the aero-engine, and at the same time only by modifying the software control program of the digital electronic controller Can achieve. The design method of the aero-engine life-extending controller can not only be used in the new aero-engine life-extending control, but also avoid greatly modifying the control hardware when upgrading the existing control system; it not only prolongs the life of the aero-engine, but also reduces the use and maintenance cost.

Description

A Design Method of Aeroengine Life Extension Controller

technical field

The invention relates to the field of aerospace propulsion system control and simulation, in particular to a design method for an aeroengine life extension controller.

Background technique

The traditional method of extending the service life of aero-engines is to replace parts or redesign long-life parts, such as patent CN103982242A, by redesigning the circular arc end teeth of the gas turbine engine to solve the problems of the existing arc end teeth. The transition zone cannot withstand the stress generated by high-speed operation, resulting in the problem of too short life, but this method requires redesign and manufacture of the wheel. In 1988, Carl F.Lorenzo first proposed the concept of Life Extending Control (LEC) (A ReusableRocket Engine Intelligent Control[R].NASA Technical Memorandum 100963,Washington:NASA,1988), which is not within the allowed range Under the premise of affecting the system to complete the task, the control strategy to reduce or prevent the development of damage by appropriately reducing the dynamic performance of the system, thereby greatly prolonging the working life of the system, the key lies in the proper balance between the dynamic performance of the system and the durability of key components. Compromise, to achieve the purpose of completing the task and prolonging the working life of the system, to reflect the requirements of enhancing the reliability, availability, maintainability and durability of components of the system. Although some exploratory researches on life extension control have been carried out at home and abroad in recent years, these researches basically remain at the theoretical stage and are difficult to be used in practical aeroengines. Life extension control has important and universal significance for military aircraft engines, civilian aircraft engines, and gas turbine engines for other purposes, and it also completely changes the design concept of expensive device control systems.

Contents of the invention

In order to avoid the deficiencies in the prior art, the present invention proposes a design method for an aero-engine life extension controller; the purpose is to increase the high-pressure rotor acceleration limit in the aero-engine control system, and simultaneously combine the indicators representing the life of the aero-engine and the indicators representing performance Incorporated into the optimization objective function, the genetic algorithm is used to optimize the acceleration limit, so that the controller can prolong the life of the aero-engine while ensuring that the acceleration performance of the engine remains unchanged or only slightly decreases, effectively prolonging the life of the aero-engine, reducing the use and maintenance costs.

The technical scheme that the present invention solves its technical problem adopts is:

A kind of aero-engine life extension controller design method is characterized in that comprising the following steps:

Step 1. selects the life-limiting part that determines aero-engine life, sets up the life model of aero-engine; Select high-pressure turbine guide vane as the life-limiting part that represents aero-engine life, and the life model of aero-engine is expressed as:

${\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; metal</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

In the formula: N _s is the service life of the aero-engine, T _{△ max} is the maximum temperature difference between the leading and trailing edges of the blade,

is the blade metal temperature under the maximum temperature difference;

Step 2. Modify the acceleration control law; from the life model, it can be known that the life of the aero-engine is related to the maximum temperature difference T _{△ max} between the front and rear edges of the blade, and the blade metal temperature under the maximum temperature difference related, while T _△max , Appears in the process of the engine accelerating from idle to maximum thrust, by increasing the high-pressure rotor acceleration limit in the original control system, modifying the acceleration control law, adjusting the engine acceleration process, and changing the life of the aero-engine;

Step 3. Construct a suitable high-pressure rotor acceleration limit curve; through the analysis of the simulation results of the original control system, determine the acceleration limit curve, do not limit the early acceleration, to ensure a certain acceleration performance of the engine; limit the acceleration in the later period, by sacrificing a small amount of acceleration Acceleration performance to reduce the maximum temperature difference between the front and rear edges of the blade and the metal temperature of the blade during acceleration, prolonging the life of the engine;

Step 4. Utilize the genetic algorithm to optimize the limit curve; the genetic algorithm is set as follows: the chromosome is set as the control point of the limit curve; the objective function then includes the index representing the life of the aeroengine, the total strain difference of the blade and the index representing the engine acceleration performance in the acceleration process , to accelerate the rise time; at the same time, constrain the coordinates of the control points to avoid the unpredictable shape of the curve; use the genetic algorithm to optimize the acceleration limit curve;

Step 5. Expand the optimized control point coordinates into a high-pressure rotor acceleration limit curve, and write it into the engine control program to form a life extension controller that modifies the acceleration control law.

Beneficial effect

The design method of the aero-engine life extension controller proposed by the present invention, by increasing the high-pressure rotor acceleration limit in the existing aero-engine control system, the index representing the life of the aero-engine and the index representing the performance are incorporated into the optimization objective function at the same time, and the genetic The algorithm optimizes the acceleration limit so that the controller prolongs the life of the aero-engine while ensuring that the acceleration performance of the aero-engine remains unchanged or only slightly decreases, effectively prolonging the life of the aero-engine. At the same time, only by modifying the software control program of the digital electronic controller can be achieved. The design method of the aero-engine life-extending controller can not only be used in the new aero-engine life-extending control, but also avoid greatly modifying the control hardware when upgrading the existing control system; it not only prolongs the life of the aero-engine, but also reduces the use and maintenance cost.

Description of drawings

A method for designing an aero-engine life extension controller according to the present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic diagram of the calculation flow of the aero-engine life model of the present invention.

Figure 2 is a curve diagram of the low-pressure rotor speed, the temperature in front of the turbine, and the temperature difference between the leading and trailing edges of the blade during the acceleration process.

Fig. 3 is a schematic diagram of the combined limitation curve of the rotor acceleration.

Figure 4 is a third-order Bezier curve.

Figure 5 is a flow chart of acceleration control law optimization.

Figure 6 is a structural diagram of the LEC control system.

Figure 7 is the original rotor acceleration and LEC limit curve.

Figure 8 is the low pressure rotor speed curve.

Figure 9 is the temperature curve before the turbine.

Figure 10 is the temperature difference curve before and after the blade.

Detailed ways

This embodiment is a design method for an aero-engine life extension controller.

Referring to Figures 1 to 6, taking a certain type of small bypass ratio twin-rotor turbofan engine as an example, the specific steps of the life extension controller design method are as follows:

Step 1, select the life-limiting components that determine the life of the aero-engine, and establish a life model that represents the life of the aero-engine;

The life of an aeroengine mainly depends on the life of the life-limiting parts of the disc, shaft, casing, and blades, where the blades are closer to the combustion chamber, and the thermomechanical damage is more obvious; the guide vanes are selected as the life-limiting parts representing the life of the engine in this embodiment. The life model of the aero-engine is established, and the life model of the aero-engine is established according to the process, and the obtained model is expressed as:

${\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; metal</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula: N _s is the service life of the aero-engine, T _{△ max} is the maximum temperature difference between the leading and trailing edges of the blade, is the blade metal temperature under the maximum temperature difference, and P _i,max is the peak value of pressure after the high-pressure compressor, before the high-pressure turbine, and after the high-pressure turbine.

Step 2. From step 1, it can be seen that the length of aero-engine life is related to the maximum temperature difference T _{△ max} between the leading and trailing edges of the blade and the metal temperature of the blade under the maximum temperature difference. related, while T _△max , It usually occurs when the engine accelerates from idle to maximum thrust; the simulated curves of low-pressure rotor speed, temperature in front of the turbine, and temperature difference between front and rear blades during the acceleration process show that T _{△ max} , Both appear in the late stage of acceleration; in this embodiment, the acceleration control law is modified by adding a high-pressure rotor acceleration limiting module in the original control system, so as to adjust the acceleration process of the engine in the late stage of acceleration, and change T _{△ max} , Thereby changing the life of the aero-engine.

Step 3, constructing a suitable high-voltage rotor acceleration limit curve;

In order to simplify the optimization process of the acceleration limit curve in this embodiment, the acceleration limit curve of the high-pressure rotor is designed to be composed of a controllable Bezier curve and a straight line as the speed increases and the acceleration limit decreases; the Bezier curve is a third-order Bezier curve composed of four Points P ₁ (x ₁ ,y ₁ ), P ₂ (x ₂ ,y ₂ ), P ₃ (x ₃ ,y ₃ ), P ₄ (x ₄ ,y ₄ ) are determined by the control polygon, and its mathematical expression (2) is:

$\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 4</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; t</span>}}^{\mathrm{<span\; class="notranslate">\; k</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; k</span>}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

When the points P ₁ (x ₁ ,y ₁ ), P ₄ (x ₄ ,y ₄ ) are determined, the shape of the third-order Bezier curve will only be determined by P ₂ (x ₂ ,y ₂ ), P ₃ (x ₃ ,y ₃ ) to determine; according to the above analysis, the limit curve will have four fixed points P ₁ , P ₂ , P ₃ , P ₄ and two control points C ₁ , C ₂ , when the fixed points are determined, the change of the control points will make the middle A suitable limit curve can be produced by changing the shape of the Bezier curve.

Step 4: Use the genetic algorithm to optimize the acceleration limit curve of the high-pressure rotor to ensure that after adding the high-pressure rotor acceleration limit, the basic acceleration performance of the engine will not be greatly reduced, and at the same time, the fatigue life of the guide vane will be improved to the greatest extent; among them, the genetic algorithm algorithm Chromosomes and objective functions are defined as follows:

Chromosomes for Genetic Algorithms:

The coordinates of the two control points of the limit curve are shown in Table 1:

Table 1 Chromosomes of combined restriction curves

The objective function is:

Fitness＝1/[α△ε _total +(1-α)t _r ] (3)

Among them, △ε _total is the total strain difference during the acceleration process of the blade, which is used as an index representing the life of the blade; t _r is the acceleration rise time, which is used as an index representing the acceleration performance of the engine; α is the weight coefficient, and its value is between 0-1 The change is used to determine the proportion of the total blade strain difference △ε _total and the rise time t _{r of} the low-pressure rotor in the objective function. By adjusting this value, different rise times and corresponding blade life are obtained. The above parameters are all normalized.

The △ε _total and t _r in the objective function are obtained through simulation. The specific method is to convert the C1 and C2 coordinate values optimized by the genetic algorithm into the high-voltage rotor acceleration limit curve, and use it as the LEC control law, and import the law into the LEC control system. In the acceleration limiter, the acceleration simulation is carried out, and the data obtained by the simulation is processed to obtain the △ε _total and t _r under the coordinate values of the control points.

Optimization constraints:

In order to ensure that the acceleration limit curve does not appear unpredictable, the coordinate range of the two control points is constrained:

The value ranges of the horizontal and vertical coordinates of the four points C1 and C2 to be optimized are selected as [0.89,1.02], [200,1600], [0.89,1.02], [200,1600].

Step five, using the optimized high-voltage rotor acceleration limit curve in the acceleration limit module to form a life extension controller based on the modified acceleration control law.

Figure 6 is the structure diagram of the life extension control system, in which the LEC control law is used to receive the designed acceleration limit curve, and the acceleration limiter gives the appropriate fuel flow according to the limit curve and the actual rotor acceleration, which is calculated with the original controller The fuel flow of is taken as the final fuel flow.

In order to further illustrate the effect of this embodiment, through simulation experiments, the life extension controller in this embodiment is compared with the control performance of the original aero-engine controller; using the above method, set α=0.1, 0.4, 0.6, 0.9, the simulation results of different life extension controllers and the original controller are shown in Figures 7 to 10 and Table 2.

Figure 7 shows the acceleration curve of the original high-voltage rotor and the LEC limit curve obtained under different weights, where the solid black line is the acceleration curve of the high-voltage rotor under the original controller, and the dotted line is the limit curve. As the weight α increases, the weight of the total strain difference of the guide vane in the objective function increases, and the optimization is more inclined to reduce the total strain difference of the blade, and the limit curve obtained by optimization is more constrained, so as to avoid excessive temperature difference between the front of the turbine and the temperature difference between the front and rear of the blade. Great, prolongs the life of the engine.

Fig. 7, Fig. 8, Fig. 9, Fig. 10, respectively, when α = 0.1, 0.4, 0.6, 0.9, the life-extending controller and the original controller under the engine's large transition state low-pressure rotor speed curve, the temperature curve before the turbine and the front and rear of the blade temperature difference curve. As the weight α increases, the peak temperature of the turbine front temperature and the temperature difference between the front and rear of the guide vane gradually decrease, and the rising trend of the low-pressure rotor speed slows down in the late acceleration period.

Table 2 shows the comparative values of engine parameters under different weights under the life extension control and the original controller. As α increases, the acceleration performance of the engine decreases slightly, but the temperature before the turbine, the temperature difference between the front and rear of the guide vane, and the temperature before the turbine The change values are all reduced, resulting in a decrease in the total strain difference on the blade, and a longer service life of the blade with TMF.

Table 2 Comparison of engine parameters between the life extension controller and the original controller

Claims (1)

1. an aeroengine life extension control device design method, is characterized in that comprising the following steps:

Step 1. selects the life-span limiting part determining the aeroengine life-span, sets up the life model of aeroengine; The life-span limiting part in choose high-pressure turbine guide vane representatively aeroengine life-span, the life model of aeroengine is expressed as:

$N_s=f(T_{\mathrm{\&Delta;}\max },T_{\mathrm{metal}\left(T_{\mathrm{\&Delta;}\max }\right)})$

In formula: N _sfor the aeroengine life-span, T _{△ max}for blade front and rear edge maximum temperature difference,

for maximum temperature difference lower blade metal temperature;

Step 2. is revised and is accelerated control law; From life-span length and the blade front and rear edge maximum temperature difference T of the known aeroengine of life model _{△ max}, maximum temperature difference lower blade metal temperature relevant, and T _{△ max}, appearing at motor accelerates in the process of maximum thrust by slow train, and by increasing the restriction of high pressure rotor acceleration in original control system, control law is accelerated in amendment, and adjustment engine accelerating course, changes the life-span of aeroengine;

Step 3. constructs suitable high pressure rotor acceleration restrictive curve; By the analysis of simulation result to original control system, determine acceleration restrictive curve, acceleration is not limited early stage, ensure the certain acceleration performance of motor; To the restriction of acceleration later stage, accelerating later stage a small amount of acceleration performance by sacrificing, to reduce accelerating process Leaf front and rear edge maximum temperature difference and blade metal temperature, extending engine life;

Step 4. utilizes genetic algorithm optimization restrictive curve; Genetic algorithm arranges as follows: chromosome is set to the control point of restrictive curve; Objective function then comprises the index representing the aeroengine life-span simultaneously, the total strain of accelerating process Leaf difference and represent engine acceleration Fa Dongjicongzhidingdituilizhuantaianquanxunsudiguodudaozhidinggaotuili can index, accelerate the rise time; Control point coordinate is retrained simultaneously, avoid curve to occur unpredictable shape; Genetic algorithm is utilized to be optimized acceleration restrictive curve;

The control point coordinate obtained after optimization is extended to high pressure rotor acceleration restrictive curve by step 5., and is written in engine control procedures, forms the life extension control device that control law is accelerated in amendment.