Numerical Analysis of In-Cylinder Flow in a Single Cylinder Research Engine with Variable Compression Ratio

In this work, the in-cylinder flow of a spark ignited Single Cylinder Research Engine (SCRE) with variable compression ratio was simulated using STAR-CD, a Computational Fluid Dynamics (CFD) software with es-ice module for internal combustion engines. The engine used in this work was an AVL SCRE with 82 mm bore and 86 mm stroke. The simulations were made in two different configurations, one with a piston suited for wall guided direct injection and a steel liner (Configuration 1) and another with flat piston and a transparent liner (Configuration 2). Configuration 1 was simulated with the compression ratios of 9.3:1, 11.5:1 and 12.0:1 and had its in-cylinder values of tumble, Turbulent Kinetic Energy (TKE), pressure and temperature analyzed and compared between compression ratios. Configuration 2 was used for validation of in-cylinder flow field using Particle Image Velocimetry (PIV) measurements and experimental in-cylinder pressure. Both configurations were simulated for 1000 RPM. The validation comparing simulation and experimental results showed an average and maximum difference of in-cylinder pressure of 2% and 7% respectively and an average and maximum difference of mean velocity at the visualization window of 12% and 18% respectively. Very small differences were observed in the tumble coefficients and TKE levels between compression ratios while temperature and pressure increased as expected with increasing compression ratio.