The effect of imbalance distribution and measurement locations on critical speeds in a turboprop engine rotor

Abstract

The critical speeds of a turbomachine can be defined as the speeds at which synchronous response to imbalance is maximum (Vance,1988). Identifying the proper placement of critical speeds is very important in the design process of turbomachinery. This study examines the influence of imbalance distribution and vibration measurement location on critical speeds for a model turboprop engine rotor. Imbalance response measurements are presented for a full scale model mounted in rolling bearings with squeeze film damper. The measurements were recorded with a Bentley Nevada ADRE 208 Data Acquisition Interface Unit System. These measurements are compared with predictions from a XLROTOR (Spreadsheet for Rotordynamic Analysis) computer model. Measurement imbalance responses show that imbalance location has profound influence on critical speeds. A critical speed variation up to 25 % was found. Comparison between the XLROTOR computer model prediction and measurement shows excellent agreement.