Research On Identification For Vibration Parameters Of Rotating Blades Using Blade Tip Timing Without The Once-per Revolution Sensor

Rotating blades are key components in aero-engine,which are usually used to convert energy to motion and are usually subjected to several sources of excitation such as centrifugal force easily leading to blade vibration.Therefore,blade vibration measurement during operation is of great importance from the perspective of safety and reliability.Blade Tip Timing(BTT)is considered a promising technique for monitoring blade vibration online for aero-engine.The majority of BTT measurement and analysis systems require a once-per revolution(OPR)sensor to generate a timing reference and measure the rotating speed of blades.However,one of the challenges in the development of BTT technique is that it's extremely difficult to install the OPR sensor and that the installation of the OPR sensor may cause potential security risks.The effective solution to this dilemma is BTT measurement without the OPR sensor.Provided that there is an alternative method for the OPR sensor,BTT measurement without the OPR sensor can be implemented.This dissertation focuses on the research on BTT measurement and parameters identification of rotating blade vibration without the OPR sensor.The functions of the OPR sensor in BTT measurement are summarized and the alternative methods for the OPR sensor have been looked for.The main works are shown as follows:1.Under the condition that the OPR sensor is unavailable,the OPR signal is derived by utilizing tip timing signals of one blade between neighboring two circles or the relation between the rotational angle of blade and the arrival time of blade,respectively.Taking the influence of rotational speed fluctuation into consideration,the method has been improved and a flexible way of blade numbering is put forward,which lays the foundation for BTT measurement without OPR sensor.2.For the demand of identification of synchronous vibration parameters,the vibration displacement change is deduced on the basis of the derived OPR signal.The method of synchronous vibration parameters identification,called Two Parameter Plot Method,is improved by mounting an additional BTT sensor and the amplitude and Engine Order(Ne)of blade vibration can be identified through analyzing the vibration displacement change.Moreover,the effects of BTT sensors placement on identification are discussed.The result of numerical simulation shows that the arithmetic is valid.3.Aimed at measuring and analyzing asynchronous vibration without the OPR sensor,the method called Delay Sampling is presented and improved by the same way as Two Parameter Plot Method.By analyzing the vibration displacement change,the amplitude and frequency of blade vibration can be identified.The result of numerical simulation also shows that the arithmetic is valid.4.Under the present experimental conditions,an experimental scheme is made according to the identification arithmetic of blade vibration.Finally,the methods of generation of derived OPR signal and the identification arithmetic of blade vibration are proven through experiments.The result shows validity of the arithmetic.