Abstract
In modern dissipated power generation systems, microturbines of power output ranging between 1 and 20 kW are applied. The development of a reliable bearing technology for high-speed small turbomachinery could be essential to these power-generating devices. In order to introduce this technology to common use, the optimal design selection from the viewpoint of machine reliability must be conducted. Therefore, one should analyze thoroughly the dynamics of the rotor-bearing-casing system in the whole operating range of the machine. The rotating system presented in the paper is supported in oil-free, airfoil bearings. Compliant surface foil gas bearings are a class of hydrodynamic bearings that use the ambient gas as their working fluid and thus require no dedicated lubrication systems, which makes their design much simpler. The article presents the development and experimental verification of a theoretical numerical model of the foil bearing for analysis of its dynamic characteristics (a sum of properties: two elastic elements connected in a series and their relative motion, friction that is related to this motion with respect to the elastic and cylindrical foils subjected to deformation) that will be an useable part of the study referring to numerical analyses oriented on developing a model of the high-speed rotor supported in bump-foil bearings.
Highlights
The micro-power system, with the power output ranging between 0.05 and 20 kW, is based on the Brayton or Rankine cycle and consists of a turbine and a generator
The compressibility of gas is an important factor and it has to be included in the analysis of various forms of gas bearings— both aerodynamic and aerostatic
An important problem of the aerodynamic gas bearing application is connected to the start-up and the shut-down in contact with the shaft surface and : coupled dynamic coefficients, linearized around the static equilibrium position of the bearing
Summary
The micro-power system, with the power output ranging between 0.05 and 20 kW, is based on the Brayton or Rankine cycle and consists of a turbine (gas turbine) and a generator. The system requires high revolutions to generate sufficient power in the small-size turbine (microturbine). The term “microturbine” is often used for turbine systems characterized by the power output from a few watts to hundreds of kW. In this field, we consider a microturbine to produce electricity in this power range at the speed of approximately 10,000–100,000 rpm. More and more common applications of non-conventional materials in the machine design provide opportunities for considering an idea of applying the working medium used in a small high-speed turbomachine as a lubricating medium for its bearings very realistic. While studying possible applications of non-conventional lubricating media, one should analyze thoroughly the dynamics of the “rotor-bearing-casing” system within the whole range of machine operation [4]
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