Blade tip clearance is one of the important parameters affecting the performance, safety and stability of a gas turbine engine. However, it is difficult to measure the tip clearance in real time and accurately during the development and test process of an engine. In order to promote the development of tip clearance–measuring technology and the optimal design of the gas turbine engine, some typical measuring methods of tip clearance and a novel measuring method based on AC discharge are introduced. In this article, the significance for measuring tip clearance of an engine is illustrated first. Then, operating principles, characteristics and developments of those typical measurement approaches are introduced. After that, these methods are analyzed, and the particular characteristic of each measuring approach is summarized.
Due to the poor working conditions of an engine, its control system is prone to failure. If these faults cannot be treated in time, it will cause great loss of life and property. In order to improve the safety and reliability of an aero-engine, fault diagnosis, and optimization method of engine control system based on probabilistic neural network (PNN) and support vector machine (SVM) is proposed. Firstly, using the German 3 W piston engine as a control object, the fault diagnosis scheme is designed and introduced briefly. Then, the fault injection is performed to produce faults, and the data sample for engine fault diagnosis is established. Finally, the important parameters of PNN and SVM are optimized by particle swarm optimization (PSO), and the results are analyzed and compared. It shows that the engine fault diagnosis method based on PNN and SVM can effectively diagnose the common faults. Under the optimization of PSO, the accuracy of PNN and SVM results are significantly improved, the classification accuracy of PNN is up to 96.4%, and the accuracy of SVM is up to 98.8%, which improves the application of them in fault diagnosis technology of aero-piston engine control system.
To provide the desired thrust and prevent the engine from exceeding any safety or operational limits, a min-max selector with linear limiters is widely employed in current aircraft engine control logic. However, with the further requirements of engine performance, the traditional linear limiters should be improved. Though there are many researchers working on the development of improvement methods, none of those methods consider the limitation of core shaft acceleration. In this paper, a novel control scheme for aircraft engine based on sliding mode control with acceleration/deceleration limiter is proposed. Above all, the controller construction process is introduced, and the asymptotic stability of the whole controller is given. Then, with linearized model of JT9D turbofan engine, the control performance of the new approach is presented, which is also compared with the traditional methods. The simulation results show that the proposed method is efficient, and it can ensure all outputs of the controller, including the core shaft accelerationṄ c , high-pressure turbine outlet temperature increment T 48 , high-pressure compressor stall margin increment SmHPC, and so on, are well controlled. INDEX TERMS Min-max logic, sliding mode control, aircraft propulsion, acceleration/deceleration limit.
A new measuring system for the engine tip clearance based on alternate current discharge is proposed in this article. Firstly, theoretical analysis and numerical simulation of the system, as well as the experiment of gas discharge are introduced to prove the feasibility of the method. Then a validation platform is built to study the effects of different probe materials and structures, as well as changes in temperature and humidity under atmospheric pressure on the system. Finally, the system calibration and tip clearance measurement are carried out. The results show that tungsten copper probe with planar structure is more suitable for measuring the tip clearance. When the tip clearance is between 0-6mm, the designed system has high measurement accuracy and its measurement error within 0.05mm. Compared with the traditional spark discharge method, the proposed method not only has the similar advantages, but also overcomes many defects, and has a broader application prospect. INDEX TERMS Tip clearance, AC discharge, measurement accuracy, spark discharge method.
Abstract. Min-Max selector structure is widely employed in current aircraft engine control logic. And the structure must provide desired thrust and prevent the engine from exceeding any safety or operational limits. In this paper, a new control scheme, that is Min-Max selector structure composed of Sliding Mode (SM) regulator and linear regulator, is presented. The main regulator is a linear regulator and all limit regulators are SM regulators. It could overcome the possibility of limit violation for the traditional Min-Max, and don' t need the augmented state references that is one drawback of SMC Min-Max(all regulators are SM regulator ). The simulation results show that the proposed approach could effectively prevent limit violation and can improve Min-Max limit protection for aircraft engine control.
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