Modified Stirling cycle thermodynamic model IPD-MSM and its application

Abstract

A Stirling cycle is a thermoelectric conversion method with high efficiency and reliability. The Stirling cycle applies to small- and medium-sized power space nuclear reactors or radioisotope heat sources. A high-precision and well-predicted Stirling cycle thermodynamic model is the key to optimizing and improving the Stirling engine for space. The present study modified the classical Simple model by incorporating the local pressure loss into the pressure loss. An improved second-order adiabatic model based on the Simple model, namely the Incorporated Pressure Drop-modified Simple Model (IPD-MSM), was proposed. The prediction of the IPD-MSM shows well with the changing tendency of the GPU-3 Stirling engine experimental data. Moreover, this model has better prediction accuracy at high-pressure and high-frequency conditions than other adiabatic models, such as CAFS and ISAM. The thermodynamic properties of He, H2, and Helium-Xenon mixtures in the Stirling cycle were also analyzed. Results show that the He-Xe mixture reaches the highest output power and thermal efficiency when the mole percentage of Xe is approximately 2%. The mechanism is as follows: the addition of Xe leading to the reduction in non-ideal heat transfer loss exceeds the increase in pressure loss. The addition of Xe leads the pressure loss to increase abruptly as the mole percentage of Xe exceeds 2%. The characteristics and application analysis of H2, He, and He-Xe mixture were discussed. The present study provided theoretical support for the Stirling cycle analysis for space missions and the selection of working fluids.