An investigation on dynamic characteristics of a high speed rotor with complex structure for microturbine test rig

During the research and development of 100kW class microturbine, a test rig with complex structure rotor for turbine impeller was constructed. Due to the limitation of test rig, the test rotor has to adopt cantilever configuration, which consists of shaft, connect disk with cool air holes, turbine impeller, and tie bar that joints the previous three components together. Because the rotor has a high rotational speed of 30000rpm, the ceramic rolling bearing is adopted for the test rig. In order to understand the dynamic characteristics of the rotor, a numerical model for temperature field has been developed using three dimensional finite element method firstly; then a numerical model to analyze the dynamic characteristics of high-speed ceramic rolling bearing and a numerical model to analyze the dynamic characteristics of the rotor considering the effect of temperature, shear deflection and gyroscopics have been developed too. At last, the temperature field and the dynamic characteristics of the test rig rotor were investigated in detail, some numerical results such as the critical speeds of lateral and torsional vibration, imbalance response, accelerate transient response were obtained. The numerical result of the first critical speed of lateral vibration shows good agreement with the experimental data, so the numerical model can provide accurate results for rotor dynamic analysis of such kind of rotor. Meanwhile, the critical speeds of lateral vibration and torsional vibration are far away from the operation speed of the rotor, and the response values are also very small, so that the rotor can operate reliably.