An OPR-free Blade Tip Timing Method Based on Blade Spacing Change

Compressor blades often operate in high temper-ature, high pressure, and heavy load environments. They are in direct contact with the outside air, which causes their life to be severely limited. Blade vibration is an important factor that reflecting the state of the blade. Therefore, effective blade vibration monitoring methods are needed. Blade tip timing (BTT) is a non-contact blade vibration measurement method that has the potential to achieve real-time condition monitoring. However, one of the biggest obstacles to real-time condition monitoring is the once per revolution (OPR) sensor in BTT. Due to the internal environment limitations of aero-engines, installing the OPR sensor in an actual engine is extremely expensive, and it is almost impossible to install the OPR sensor. To solve this problem, the relationship between the blade spacing change (BSC) and the blade vibration is analyzed and the measurement principle of BSC is presented in this study. Based on BSC, we proposed a novel BTT measurement method that does not need the OPR signal. The simulation and experiment are conducted to show the rationality of the proposed method.