Gamma-Stirling engine – The effect of different working gases and pressures

This paper presents an investigation into the effects of changing the charge pressure as well as the working gas in a gamma type Stirling engine. An algorithm is developed to predict the effects of engine pressure and the type of working gas on the performance of a gamma-type Stirling engine. Based on the equation of state and the principle of energy and mass conservation, a set of first order differential equations are established. The fourth order Runge-Kutta method is used to solve these equations. The heat losses due to imperfect regeneration and pumping losses in the heat exchangers are included in the solution. The results show that using a working gas of lower density will cause less power losses compared to a working gas of higher density. Above 7.5bar the increase in efficiency with increased pressure becomes less significant with less than 4% increase from 7.5bar to 15bar for air. There is a linear relation between the amount of actual work and the nominal pressure charge of the engine. The results obtained from this simulation show a satisfactory working condition of the engine. The model sections and subsections were verified step by step using detailed and laborious manual calculations.