Two-Dimensional Compressible Non-Acoustic Modeling of Stirling Machine-Type Components

Abstract

Starting with an existing two-dimensional incompressible e ow computer code, a two-dimensional code was developed for modeling enclosed gas volumes with oscillating boundaries. The incompressible code was modie ed to use compressible nonacoustic Navier‐ Stokes equations. The devices modeled have low Mach numbers and are sufe cientlysmallthatthetimerequiredforacousticstopropagateacrosstheinteriorsissmallcomparedtothecycle period.Therefore,acousticswereexcludedtominimizecomputingtime.Thecompressiblenonacousticassumptions are discussed. The governing equations are presented in transport equation format. The numerical methods are briee y described.Codepredictionsarecompared with experimentaldata.Compressiblenonacousticpredictionsof gas spring losses agreed well with 10-rpm test data, and »50- and 500-rpm calculated and experimental pressure‐ volume diagrams agreed well. For a heat-exchanger/piston-cylinder test rig, calculations of heat exchanger heat e uxes at various axial locations over the cycle agreed well qualitatively with the data, but quantitative agreement was not good.