Intelligent Life Extending Control Of Aircraft Engine

The design of traditional aircraft engine control focuses on how to ensure safety and reliablity,while improve the engine performance as much as possible, but engine or component life israrely incorporated into the design of control system. However, engine life is greatly affectedby its control system, while a new generation of aircraft engines put forward higherrequirements for operability and durability. Life Extending Control (LEC) addresses therelationship between control and engine component life, and researches on extending engineor components life by adjusting control system. This paper uses the thermo-mechanicalfatigue (TMF) life of high-pressure turbine stator to demonstrate how LEC can drasticallyextend the components life with minimum sacrifice in performance, in order to providetheoretical basis and engineering application reference to improve durability of aircraft engine.The main contents are organized as follows:Firstly, this paper analyzes the common fatigue of aircraft engine, and the high-pressureturbine stator is selected as the research object. Then the simplified TMF life model isestablished. On the basis, an approach based on probability theory is described to estimatestator life in operating environment uncertainties. A closed-loop simulation system with aTMF life model is built and a Monte Carlo simulation approach is used to generate theanalysis datas, Weibull distribution is then used to calculate the probability of failure and theequal life usage is given. The simulation shows that the model meets the research needs ofLEC with small amount of computation, while the actual operating environment has animportant impact on the life usage and probability of failure of the stators.Next, the factors affecting the TMF life of the high-pressure turbine stator are analyzed, whichare associated with acceleration process. Therefore, the high-pressure rotor accelerationlimiter is added to the original control system to extend the life of the stator; then, rise timeand total strain are incorporated into the optimization objective function, and geneticalgorithm is used to optimize the acceleration limit curve. The results show that, the lifeextending control based on modified acceleration law can be greatly improved stator life, andthe engine acceleration performance does not reduce significantly in different operatingconditions.Subsequently, an adaptive LEC strategy that the LEC limit curve relaxs with the increase of the degradation degree is proposed. Then a double layer structure for adaptive LEC is given,which could estimate the degradation degree in real time and select the appropriate LECcontrol law. Simulation results show that the adaptive LEC can make the engine accelerationperformance remain unchanged and extend the component life in the whole life.However, life extending control and traditional control are designed for normal use; but insome emergency events, aircraft engines are expected to provide enhanced performance.Therefore, the implementation and performance of two emergency control modes are studiedin detail. At last, a multi-layer control system architecture is introduced to integratedemergency control, life extending control and traditional performance control.Finally, life extending control, adaptive LEC and emergency control have been implementedin an actual electronic controller (PC104). Real-time, hardware in the loop simulation resultsshow that the control technologies are achievable in the hardware level of current aviationelectronic engine controller, and thus have a certain value in engineering.