Feasibility study on the conversion of a small engine into a single-piston expander operating under different pressure and valve timing conditions

Abstract

There are limited studies on improving the piston expander performance for a wider operating range by adopting the variable valve timing method. This study uses a simple conversion technique to develop a single-piston expander (SPE) from a small two-stroke engine. The SPE is being tested at different operating conditions to study the feasibility of the SPE operating under different intake pressure and valve timing conditions. By fixing the exhaust valve timing, the SPE was tested at four intake pressure; 3, 4, 5, and 6 bar, while the intake valve closing varied from 30° to 110°. From the study, the highest power produced by the SPE was only 64 Watt when tested at 6 bar, with the intake valve opening at TDC and closed at 70°. The results show that the converted SPE is feasible in terms of functionality, but it is not performance-wise because much power has been lost through the recompression process. The study also observed that the intake valve timing could significantly affect the SPE power output, besides the intake pressure alone.