A Direct Drive Rotary Valve for Efficient Power Generation in Gas Expander Based Small Scale Power Plants

Organic Rankine Cycle (ORC) based small-scale energy generation systems can be utilized to address the rapidly increasing demand for low-cost power. But the overall efficiency of these systems is limited by the efficiency of the gas expander which extracts work from the working fluid. This efficiency can be greatly improved by regulating the flow of working fluid into the expander chamber using a control valve. In this manuscript, a rotary valve driven by a direct drive stepper motor (DDRV) is proposed and the dynamics of the valve is studied. The overall performance of the limaçon expander equipped with this valve on the inlet port is also analyzed. The thermodynamic performance of the system such as isentropic efficiency and filling factor are calculated. An increase in isentropic efficiency of 14.86% with a decrease in filling factor of 16.88% is achieved compared to the ported, without an inlet valve, expander.