Propulsion Health Monitoring assessed by Microwave Sensor Performance and Blade Tip Timing

Gas turbine engine makers are always striving to implement newer technologies to help monitor the engine health and performance. Among these technologies is the employment of highly specialized sensors within the engine compartment. The sensors are to screen response of components such as rotor disk blades which are subjects to complex loading conditions and that includes combined thermal and mechanical loads. Detecting unexpected or excessive blade Vibration before failure is critical to ensure safety and to achieve expected apparatus life. Traditional detection methods have relied solely on component inspection during service or on the use of gage telemetry systems as well as other means of non-destructive evaluation. These methods require time and cost and do not provided an accurate feedback of the health when the engine is in operation. At NASA Glenn Research Center, an effort is underway to develop and test validate microwave based blade tip timing sensors in support of the latter concerns and for the purpose of investigating their application for propulsion health monitoring under the Transformational Tools and Technologies Project. The process involves working with prototype sensors to determine their applicability and assess their ability in making blade tip clearance measurements along with further refining a methodology required to extract deflection measurements from the raw data acquired from the sensors. The efforts focus specifically on the use and implementation of microwave based tip-timing sensors that are intended to be used for non-contact stress measurement application. The current study includes an experimental task to define the optimum setup of these sensors, determine their sensitivity in making blade tip deflection measurements and validate their performance against realistic geometries in a spin rig. It also includes analytical calculations to compare to the experimental results. Data pertaining to the findings obtained from the testing as well as the supportive analytical results are presented and discussed.