Research On Failure Modes Of The Aero-engine Speed Sensor

Speed sensor failure detection is a basic part for airworthiness of aero-engines.At present,the research on the failure modes of speed sensors are mainly focused on the optimization of the internal components of sensor probes or conditioning circuits.As an important part of the speed measurement system,the influence of the measured gear on the output signal is rarely studied.In this paper,the influence of different gear configurations,working environment temperature and gear mechanical faults on the sensor output signal is analyzed,and the sensor failure modes related to the measured gear is studied,which can support the development of airworthiness certification of the aero-engine speed sensor.Based on the structure of N1 speed sensor detection platform of CFM56 aero-engine,a physical model is built and input into the software Ansoft Maxwell for electromagnetic analysis,which offers the original signals.Then according to the digital signal processing method,a numerical calculation model of the signal conditioning circuitthe is built based on the software Matlab.Finally,the signal feature detection programs are designed based on software Matlab.These programs support analysis on the high and low values of signals,the duty ratio of signals,the effective voltage value of signals and rotation speed values under different conditions.As for the influence of gear configurations on the signals,the gears with tooth angles of0~o,5~o,10~o and 15~o are built up for simulation tests.The results show that the sensor fails at some speeds when the tooth angle increases.As for the influence of the working environment temperature on the signals,the maximum variation of the measurement distance caused by the thermal expansion effect of the measured gear is 0.22mm,and then the distances of 0.8mm,0.9mm,1.0mm and 1.1mm are set up for simulation tests.The results show that the sensor fails at some speeds when the measuring distance increases.In view of the influence of the gear teeth angle on the signals,the tooth angle changes caused by the wear is considered.The gears with wear angles of 0~o,5~o and 10~o for a single tooth are built up for simulation tests.The results show that the sensor will fail when the single tooth was seriously worn.In view of the influence of measurement distance on the signals,the changes of measurement distance caused by gear teeth fracture are considered.Gears with one single tooth fracture of 0mm,1mm,2mm,and 3mm are set up for simulation tests.The results show that the sensor will fail when the tooth fracture is severe.