Abstract
The scroll expander—generator is suitable to be used in the small-scale organic Rankine cycle system to generate electricity. In this article, a mathematical model has been developed which includes thermodynamic model, mechanical model, and load resistance model. The stable rotating speed, volumetric efficiency, and isentropic efficiency influenced by the suction pressure, discharge pressure, and generated current have been analysed. The results show that the stable condition of scroll expander—generator is determined by the driven and resistance moments. The transient rotating speed increases with the running time until the machine runs stably in the starting process. The scroll expander—generator is accelerated or decelerated when the suction pressure, discharge pressure, and generated current are changed. The stable time increases with the variation of suction pressure either in the acceleration or deceleration process. The stable rotating speed and volumetric efficiency increase with the suction pressure but decrease with the discharge pressure and generated current. The isentropic efficiency increases with the suction pressure but decreases with the generated current. A maximum isentropic efficiency is found with the increase of discharge pressure.
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