Theory And Experimental Research For Inlet Electrostatic Sensor On Aero-engine

It is the basis of safety and reliability for accurate condition monitoring on aero-engine. The electrostatic monitoring technology, which equipped with foreknowledge information for engine faults, could expediently get the realization of Condition-Based Maintenance(CBM) through online monitoring; moreover, it can effectively enhance the capacity of flight safety and reduce support costs. On the foundation of studies from predecessors, in this dissertation, theory and experimental studies for inlet electrostatic sensor on aero-engine are carried out. To begin with, the sources of aero-engine inlet and exhaust particles are analyzed. Fouthermore, through the description of particles charge mechanism and electrostatic monitoring principle, the composition of aero-engine gas path electrostatic monitoring system is described. The key technologies to inlet electrostatic sensor are seen as followed:(1) Inlet electrostatic sensor technologyThe design principle of of inlet electrostatic sensor is analyzed. Based on point-charge theory, sensitivity space to circular electrostatic sensor probe is calculated by finite element method. What’s more, factors that affect the spatial sensitivity distribution are given with data fitting. Considering of sensor sensitivity, uniformity, mechanical processing and installation etc., the optimal ring size is designed accordingly.(2) Inlet electrostatic sensor dynamic performanceSpace sensitivity distribution function is obtained by function fitting with different axial sensitivity data. Electrostatic sensor in space and time domain, which makes static current formed by charged particles weighted average, is equivalent to low pass spatial filter. There is a conclusion that band width is changed with particle speed, radial position and the axial length of sensitive element. Furthermore, on turbojet engine, circular electrostatic sensor could not only effectively monitor the state of the gas line but also sensitively reflect the changes of engine condition and the situation of charged particles. The method is tested to verify the validity and the feasibility of the sensor.(3) Anti-interference technology and stability study to electrostatic sensorThis dissertation takes full account of shielded wire against foreign interference signal. To eliminate magnetic coupling interference, signal wires are far away from power lines. In addition, grounding design is allowed for shielding layer. Thirdly, low pass filter as well as electromagnetic interference shielding circuit and quiescent point stabilization circuit is designed to improve accuracy and stability, which eliminates temperature influence on static working point. After simulation and actual running test, good de-noising effect is obtained. Fourth, with adaptive filtering method that applied feedback to adjust filter coefficients, there is good noise reduction effect on restraining or eliminating interference. Finally, the important index temperature drift of sensor stability is analyzed by time series modeling, from which it find out the change law of temperature drift data. Consequently, this dissertation provides stability basis for sensor structure optimization and error compensation.(4)Inlet foreign object electrostatic monitoring experimentsFirstly, the inhalation environment simulation test box is designed. From signal feature parameters and its main numerical characteristics, the electrostatic induction signal generated by charged particles under different conditions are analyzed. Last but not the least, gas path electrostatic monitoring integrated-bench is designed also, from which foreign object electrostatic monitoring experiments are carried out under engine environment. For the four logic judgments of foreign object, its influence model to engine is analyzed respectively. Therefore, there must be reference and basis for further studies in future.