Design, manufacturing and performance analyses of beta type a Stirling engine

In this study, a beta-type Stirling engine with rhombic drive mechanism with 365 cm3 swept volume was designed and manufactured. In this context, the kinematic and thermodynamic analyses of a beta-type Stirling engine with rhombic drive mechanism were examined numerically in the Fortran program. Volume and pressure changes depending on the crank angle of the engine with rhombic drive mechanism were made using the isothermal analysis method developed by Gustav Schmidt. 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 working fluids on engine performance characteristics were examined at charge pressures of 1, 2, 3, 4, and 5 bar for two different displacer pistons made of stainless steel and titanium material. The performance characteristics of the manufactured Stirling engine were tested by using the specially designed electrical heater, at 727 °C (± 10 °C) hot end and 27 °C (± 5 °C) cold end temperature, depending on engine speed. In all experimental studies, the maximum engine power was obtained to be 215.48 W at a charge pressure of 4 bar and an engine speed of 550 rpm when a stainless steel displacer piston and helium gas as a working fluid were used, and the maximum engine torque value was obtained to be 7.54 Nm at a charge pressure of 5 bar and an engine speed of 150 rpm. The lowest engine power among the maximum engine powers was obtained to be 34.66 W when argon gas was used as working fluid at pressure of 3 bar and an engine speed of 300 rpm, using a displacer piston made of titanium material. The most efficient performance values among all the experimental studies conducted were obtained when displacer piston made of stainless steel and helium gas as a working fluid were used. In all working fluids except for nitrogen, displacer piston with stainless steel material performed better performance than displacer piston with titanium material. The maximum engine power obtained in the experimental studies with the stainless steel material displacer piston and helium; It was determined that it is 72.12%, 73.69%, 241.49% and 288.81% more than the powers obtained by nitrogen, air, carbon dioxide and argon gases, respectively. Energy and exergy analyses were carried out using the temperature, pressure, speed, and torque values measured in the performance tests. As a result of the exergy analysis, helium gas performed the best in the stainless steel displacer piston at a charge pressure of 4 bar and an engine speed of 550 rpm. Under the said conditions, 0.3726 W/K entropy production and 195.53 W destroyed exergy were calculated in the thermodynamic analysis in the helium working fluid. Furthermore, under the same conditions, helium gas achieved the highest efficiency values of 48.04% for thermal efficiency, 56.54% for exergy efficiency, and 69.2% for Carnot efficiency. The lowest exergetic performance was revealed in the titanium displacer piston when argon was used as working fluid.