Experimental and Analytical Study of a Steam Vane Expander
PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB
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An experimental and analytical study of a rotary vane steam expander was conducted to determine the effect of leakage, friction and heat transfer on the expander performance. A commercially available rotary vane air motor was modified to operate on steam utilizing little or no liquid lubricant. The indicated power output, shaft power output and frictional power loss of the vane expander were experimentally determined as a function of speed, inlet timing and supply steam conditions. The steam mass flow rate and component temperatures were also measured. The data show that severe internal leakage and frictional energy dissipation were major causes of efficiency reductions. An analytical model of the expander thermodynamics, friction, leakage and heat transfer was developed from fundamental principles. The model predicts the expander leakage flow rate, frictional power loss heat transfer rate and the effect of these losses on the power output and efficiency. The analytically and experimentally determined frictional power losses were in agreement. The component temperature profiles were predicted with maximum errors of 10 - 15. The predicted leakage flow was approximately 16 below the experimentally determined value. Errors in the leakage flow predictions resulted in the predicted indicated power outputs being 20 - 40 below the experimental values. This was considered reasonably good in light of the difficulty in identifying the steam leakage paths and component clearances.
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