Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.

Identification of a Crack in a Rotor System using a Model-based Wavelet Approach

Abstract: The dynamics and diagnostics of a cracked rotor have been gaining importance in recent years. Vibration monitoring during start-up or shut-down is as important as during steady-state operations to detect cracks especially for machines such as aircraft engines which start and stop quite frequently and run at high speeds. In the present study, a model-based method is proposed for the on-line identification of cracks in a rotor while it is passing through its flexural critical speed. The fault-induced change of the rotor system is taken into account by equivalent loads in the mathematical model. The equivalent loads are virtual forces and moments acting on the linear undamaged system to generate a dynamic behaviour identical to the measured one of the damaged system. The rotor has been modelled using FEM, while the crack is considered through local flexibility change. The crack has been identified for its depth and location on the shaft for different rotor accelerations. The nature and symptoms of the fault ...

Development of an ultra high speed permanent magnet synchronous motor

Abstract: To accomplish the research of a PM synchronous motor driven by 15 kW at a rated speed of 120 krpm. This paper represents an approach to minimize the eddy current losses that occur frequently at high speeds. Various simulation and testing techniques are applied to grasp the physical phenomena. Here, sleeve thickness is proposed parameter for analysis. Finally, this paper studies the developed model which represents a tendency for minimizing eddy current loss, von-Mises stress, unbalance vibration response and maximizing critical speed. It comes to the conclusion that sleeve thickness should be chosen after considering the function of mechanical stress, critical speed and unbalance vibration response of the rotor. The design efficiency is well suited to the efficiency test, having a maximum error of 2.7%.

Balancing of flexible rotors without trial weights based on finite element modal analysis

Abstract: With the continuous improvement of aviation engine performance, the engine rotor’s working speed is above the first critical speed, and some small engine rotor’s operating speed exceeds the second critical speed, thus most of the aircraft engine rotor is now flexible rotor. The primary goal of this research is to provide a new method without trial weights for flexible rotor balancing, which is based on the traditional modal balancing method and combines the dynamic characteristics of the rotor, such as the model shape, obtained by using finite element analysis software, the critical speed, the modal damping ratio, and so on. To demonstrate the validity and accuracy of the new method, two experiments are carried out. One is on a four-disk simply supported structure rotor experiment, which is balanced by using three balancing planes. After balancing the amplitude of the rotor through the first critical speed is reduced 80%. The other is on a turboshaft engine power turbine rotor which had been balanced quit...