Study On Oscillating Flow Characteristics In Abrupt Cross-section And Bent Pipes Of Stirling Cycles

Stirling engine has the characteristics of good adaptability of heat sources.It has a good prospect in the fields of solar power generation and distributed power generation system.The abrupt components and curved pipes in Stirling engines brings flow resistance which can not be ignored.Systematic study of flow resistance provides an important reference for optimal design of Stirling engine.Direct numerical simulation(DNS)and Reynolds average Navier-Stokes simulation(RANS)were used in this study to analyze the flow field of abrupt components.The change in flow resistance coefficient with the oscillating frequency was the main content.Compared with experimental data,the result of DNS was more reliable than RANS.The error between DNS and experiment was 6%and 12%;Based on the result of DNS,the relation between flow resistance coefficient and the maximum Reynolds number is shown below:fh =-0.0108(Re/100)3 + 0.561(Re/100)-9.2662(Re/100)+64.713(200?R?1000)fh = 16.3(Re>1000)Under the same oscillating frequency,flow resistance coefficient of abrupt components increased with the increase of the ratio of diameter.The relation is shown below:fh = 24.819(d2/d1)2-84.287(d2/d1)+ 78.983(500<Re<900)As for the structure of curved pipes,the flow resistance coefficient decreased with the increase of radius of curvature under the same frequency.The flow resistance coefficient decreased with the increase of oscillation frequency under the same radius of curvature.There were significant differences between the variation of flow field of abrupt components and curved pipes in a cycle.There were "sudden loop","stagnation ring","axial velocity fault" and "radial velocity fault" presented in some phases under the simulation of abrupt components and the "stagnation zone","Stagnation band" and presented in the simulation of curved pipes.This paper attempts to establish a visualization platform for oscillating flow based on particle image velocity measurement.The results of qualitative analysis show that the experimental flow field and the simulated flow field have the same characteristics.