Influence of a Regenerator on Stirling Engine Performance

Abstract

Stirling engines, as external combustion engines, can be powered using a variety of heat sources achieving significantly reduced emissions. Energy systems using Stirling engines optimize their performance in specific operating conditions. Their capacity depends on the geometric characteristics of the machine, the design of the unit, and the environment in which it works, as well as the size of the load. Therefore, the numerical analysis of each Stirling engine using more realistic independent variables is crucial for predicting the actual indicated power and efficiency for a given engine speed, mean pressure, and heater and cooler metal temperatures. A comprehensive thermodynamic analysis of the Solo 161 V Stirling engine, using the Stirling engine thermodynamic analysis model (SETAM) is presented. Working gas friction pressure drop is presented all over the engine, but mostly in the regenerator. The gas mass flow is laminar in the regenerator and turbulent at the heater and cooler. The regenerator porosity and matrix wire diameter are critical to the Stirling engine performance. The steady state condition of the engine depends on the regenerator matrix heat capacity. High matrix porosity values leads to high regenerator effectiveness but to low engine performance. An increase of the matrix heat capacity leads to reduction of the engine’s performance, the torque as well as the work output. A low speed engine is more effective with a low porosity regenerator installed. Engine performance can be independent by the speed at specific matrix porosity value. The temperature profile of the working medium in the regenerator is presented in relation to position and time. The nonideal behavior of the regenerator is demonstrated and the remaining heat in the regenerator grid is recorded when the thermal equilibrium is achieved. The effect of the regenerator’s geometrical characteristics on its effectiveness and on engine’s performance is recorded. An optimal construction design area for the regenerator, leading both to high engine’s efficiency and performance levels in certain operating conditions is presented. The Stirling engine performance in various operating conditions in relation to its geometrical characteristics is investigated.