A modified low-speed balancing method for flexible rotors based on holospectrum

Most high-speed rotating machineries operate at a speed higher than their first critical speeds. Since there are two different modal shapes existing in rotors under and over that speed, the most currently used balancing techniques for rotors require two steps to fulfill the balancing purpose. Firstly, a traditional low-speed rigid balancing is performed, and secondly, a high-speed balancing procedure is carried out. This high-speed balancing procedure is very complicated and dangerous; it needs large number of test runs and causes corresponding wastages as well. This paper develops a novel balancing method, called Low-Speed Holo-Balancing (LSHB), which can balance a flexible rotor without test runs at high speeds. The principle of LSHB is mainly based on the holospectrum technique, which will be explained in detail at the end of this paper. Instead of using information from a single sensor, through a multi-sensor fusion a three-dimensional holospectrum is constructed to describe the vibration response of a rotor vividly and accurately. LSHB can easily balance the flexible rotors at lower speeds than the first critical speed, according to the decomposition results of holospectrum. Because LSHB does not need any test runs at or higher than the first critical speed like any other traditional balancing techniques do, the balancing procedure is much safer, and economical. The key points and main operating steps of LSHB will be presented. The experimental results conducted on a flexible-rotor test rig validated the effectiveness of this method.