Exergy analysis in combined heat and power systems: A review

Performance investigation of a combined heat and power system with internal and external combustion engines

Comprehensive Performance Evaluation and Demands’ Sensitivity Analysis of Different Optimum Sizing Strategies for a Combined Cooling, Heating, and Power System

Numerical research of pressure depression in aerostatic thrust bearing with inherent orifice

A numerical method for solution of the discharge coefficients in externally pressurized gas bearings with inherent orifice restrictors

Vibrations, particularly low-frequency vibrations caused by self-excited gas films, significantly affect the safety and economy of turbomachinery, which becomes dangerous at high rotational speeds. This experimental study focuses on the dynamic characteristics of a Permanent magnet (PM) disk-type motor rotor supported by gas aerostatic bearings. Nonlinear dynamic behavior, including double low frequency and gas film half whirling, was analyzed in the experiments. The dynamic features of double low frequency and gas whirling are described in the paper. The most important finding is that the sum of the whirling ratios of low frequencies 1 and 2 is always 1.00. The occurrence mechanism requires further study. The effects of bearing supply gas pressure on the dynamic response characteristics of the multi-disk PM rotor are implemented to improve rotor stability.

Experimental studies on the effects of bearing supply gas pressure on the response of a permanent magnet disk-type motor rotor

High-speed gas bearings for turbomachinery can dramatically improve the isentropic efficiency of turbine plants. Vibrations, especially low-frequency vibrations caused by the gas-film self-excited vibrations, significantly affect the safety and economy of the turbomachinery, which is dangerous at high rotational speeds. This experimental study focuses on the dynamic characteristics of a flexible rotor supported by gas hybrid bearing and driven by a radial turbine with high-pressure air. Cylindrical whirling, conical whirling, and first-order bending natural frequencies that change with bearing supply pressures were obtained by experimental modal analysis. Nonlinear mechanic behaviors, including gas film half-speed whirling and gas-film whip, in the experiments were identified by nonlinear measurements and analyses. The occurrence mechanism of gas-film whirling and whip is also discussed in this paper. Experiments for eliminating and restraining whirling and whip were conducted to investigate the gas bearing-rotor system stability effect of bearing supply pressure and elastic foundation. Some simple and effective measures were given to improve the stable rotational speed.

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Experimental research on the dynamic characteristics of gas-hybrid bearing-flexible rotor system

Parameters optimization in the critical speed region has the important influence on operational stability of an air cycle machine. Effects of bearing stiffness and unbalanced exciting force on critical speed and response characteristics are investigated by the modal method and harmonic response analysis. Resonance separation phenomenon in the critical speed region is analyzed in detail. When difference exists in the phase of unbalanced exciting force, resonance separation appears in the conical whirling speed region. The characteristics after resonance separation are closely related to the phase difference value and amplitude of unbalanced exciting force. The paper provides theoretical and experimental foundations for resonance separation analysis and also provides data support for dynamic balance and dynamic design of the rotor system.

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Dynamic Characteristics of Air Cycle Machine Rotor System

The dynamic characteristics of the rotor-bearing system for micro-gas turbine are the key factors that affect the safe and stable operation of the micro-gas turbine. This paper carried out the experimental investigations on the vibration characteristics during the speed-up process of rotating shaft, based on rotor structure of micro gas turbine generator supported by aerostatic bearings. Rotor vibration characteristics during conical whirling critical speed area, mixed control area, surge area, self-holding speed area, and bending critical speed area were analyzed. Simultaneously effects of bearing supply pressure and radial clearance on the shaft vibration characteristics were studied by experiments. The results showed that the ignition fuel flow has stepped increase when the ignition fuel valve was opened, which caused easily the rotor and bearing rubbing. And the reasonable bearing radial clearance and gas supply pressure can effectively restrain the occurring of the low frequency whirling and gas film oscillation, and improve the bearing-rotor system stability.

Dongjiang Han

Papers

Experimental studies on the effects of bearing supply gas pressure on the response of a permanent magnet disk-type motor rotor

Experimental research on the dynamic characteristics of gas-hybrid bearing-flexible rotor system

Dynamic Characteristics of Air Cycle Machine Rotor System

Experimental Investigations on Vibration Characteristics for Bearing-Rotor System of Micro Gas Turbine

Study on different heat supplementation strategies for a combined cooling, heating and power system