Investigation of the Flow Characteristics of the Compression Ring Groove Cavity in the Expansion Time of a Compression Ignition Engine

In the expansion stroke of reciprocating engines, it is desired that the pressure generated after combustion acts on the piston surface without any losses. However, there are some losses during this process. One of these is the pressure losses in the ring grooves and gaps. In this study, the flow characteristics of the peak compression ring gaps of the Renault F8Q706 engine were examined. Investigations were carried out using Computational Fluid Dynamics (CFD) at 2500 rpm, full load and at the beginning of the piston expansion stroke after a crankshaft angle of 15 from the top dead center. Combustion products were used as fluids in the investigations. In the study, firstly, a 1D engine model was created and verified with the same engine tests in the literature. In-cylinder characteristics taken from the 1D model are defined as boundary conditions in 2-Dimensional (2D) CFD analyses. As a result, in response to the ring cavity inlet pressures of 6.5MPa, 5MPa, 3MPa, the leakage flow rates in the cavity were calculated as 2.97E-05, 1.66E-05, 3.41E-6 kg/s, respectively. For 6.5 MPa inlet pressure, the net pressure was calculated as 6.49941 MPa as a result of the pressure losses in the ring gap.