The examination of performance characteristics of a beta-type Stirling engine with a rhombic mechanism: The influence of various working fluids and displacer piston materials

Abstract

In this study, to develop a power generation system that can use renewable energy resources more efficiently, a beta-type Stirling engine with rhombic mechanism was designed and manufactured. Kinematic and thermodynamic analyses of a beta-type Stirling engine were performed numerically in the Fortran program. Volume and pressure changes depending on crankshaft angle of Stirling engine were made using the isothermal analysis. The effects of the basic parameters related to engine performance, such as working fluid mass, charge pressure, heater, and coolant temperatures, on the net work amount were investigated. Five different gases, including helium, air, nitrogen, carbon dioxide, and argon, were used as a working fluid in experimental studies. The effects of all these gases on engine performance characteristics were examined at charge pressures of 1 to 5 bar for two different displacer pistons made of stainless steel and titanium material. The performance characteristics of Stirling engine manufactured were tested using a specially designed electrical heater, at 727 degrees C hot end and 27 degrees C cold end temperature, depending on engine speed. In all experimental studies, maximum power output was acquired to be 215.48 W, at 4 bar and 550 rpm when a stainless steel displacer piston and helium gas as a working fluid were used, and maximum torque value was acquired to be 7.54 Nm, at 5 bar and 150 rpm. The lowest engine power output among maximum engine powers was acquired to be 34.66 W when argon gas was used as a working fluid at 3 bar and 300 rpm, using a displacer piston made of titanium material. Maximum power output acquired in the experimental studies using a stainless steel displacer piston and helium; it was determined that it is 72.12%, 73.69%, 241.49%, and 288.81% higher than the engine power acquired by nitrogen, air, carbon dioxide, and argon gases, respectively.