Theoretical investigations on the Stirling engine working process

The use of CFD models significantly extends the capabilities for the detailed analysis of the complex heat transfer and gas dynamic processes which occur in the internal gas circuit of a Stirling engine. In this paper, some restrictions on the implementation of a two-dimensional CFD model for the description of the working process of the Stirling Engine with a complex geometry for its heat exchangers are discussed. A mathematical model for a 2-dimensional simulation of a "V"-type Stirling engine is described and a simplified axis-symmetric calculation scheme for the engine has been assumed using the standard K-E turbulence model with a deforming mesh to describe the piston movements for the analysis of the engine's working process. Gas temperature and pressure distributions and velocity fields in the internal circuit of the engine have been obtained and pressure-volume diagrams for the working spaces of the machine have been calculated. Comparison of the numerical results obtained from the two-dimensional simulation of the engine's working process with those computed with the use of second-order mathematical models shows that there are considerable differences. In particular, an analysis of the data obtained shows that the changing of the gas temperature in the compression space depends on the location in the cylinder and it may differ substantially from being harmonic in time. At present work on the experimental validation of the computational results is underway and it is planned to use the developed approach in the design process of new Stirling engines in the Laboratory for Stirling Engines at the Physical-Technical Institute in Tashkent.