DNS, experimental and modelling study of axially compressed in-cylinder swirling flow

Abstract

Abstract The paper reports on recent progress in the investigation and modelling of joint effects of compression and swirl on turbulence in a cylinder of a single-stroke rapid compression machine (RCM). Experimental and modelling investigations cover a flat cylinder geometry and a `squish' configuration with a bowl-in-cylinder head. In addition, the direct numerical simulations (DNS) of all three operational modes of RCM have been performed: steady rotation, transient spin-down without compression and transient spin-down with compression. The Reynolds-averaged Navier–Stokes simulation (RANS) was performed using a low-Re-number second-moment closure. The results obtained are compared with the experimental results and with DNS. Prior to the computation of the RCM, the applied turbulence model was validated in several generic flows relevant to the RCM: developed and developing flows in an axially rotating pipe, swirling flows in combustion chamber geometries and long straight pipes and several flows with mean compression, ranging from homogeneous compression to the compression in a closed cylinder. It is demonstrated that in all cases considered including the RCM, the applied RANS model reproduces reasonably well both the DNS and experimental results, without any model or coefficient modifications.