Condition Monitoring of Aircraft Engine Rotor System with Stiffness Anisotropy of Rotor Supports. Comparative Analysis of Accelerometers Mounting Schemes

Abstract

Elimination of dangerous vibration modes is one of the major issues in Modern aircraft engines designing. The main source of vibrations in gas-turbine engines is rotors (Khronin in Vibrations in aircraft engines. Mashinostroenie, Moscow, 1980). Aircraft engines weight reducing and applying of new engineering solutions (Inozemtsev et al. in Fundamentals of aircraft and power plants gas turbine engines construction, 2008) lead to appearing of shaft and case units stiffness decreasing tendency. This may cause a problem with supports stiffness anisotropy which leads to complexity of vibration modes. It is known that standard (in vertical plane of engine) accelerometer mounting scheme is not effective for detecting anisotropy of supports stiffness. Therefore it might be more useful to place sensor at the angle of 45 degrees to the weak and strong stiffness axes. Comparison of both mounting schemes was made on the base of experiments performed on the rotor test rig. During experimental investigation, supports accelerations, shaft displacements and shaft rotational speeds were obtained and analyzed. Comparative qualitative analysis for both mounting schemes was provided.