1 Department of Mechanical Engineering, Technical University of Denmark2 Fluid Mechanics, Coastal and Maritime Engineering, Department of Mechanical Engineering, Technical University of Denmark3 Thermal Energy, Department of Mechanical Engineering, Technical University of Denmark4 Department of Wind Energy, Technical University of Denmark5 Fluid Mechanics, Department of Wind Energy, Technical University of Denmark6 Energy Engineering, Department of Mechanical Engineering, Technical University of Denmark7 MAN Diesel & Turbo SE
A simplified model of a low speed large twostroke marine diesel engine cylinder is developed. The effect of piston position on the in-cylinder swirling flow during the scavenging process is studied using the stereoscopic particle image velocimetry technique. The measurements are conducted at different cross-sectional planes along the cylinder length and at piston positions covering the air intake port by 0, 25, 50 and 75 %. When the intake port is fully open, the tangential velocity profile is similar to a Burgers vortex, whereas the axial velocity has a wakelike profile. Due to internal wall friction, the swirl decays downstream, and the size of the vortex core increases. For increasing port closures, the tangential velocity profile changes from a Burgers vortex to a forced vortex, and the axial velocity changes correspondingly from a wake-like profile to a jet-like profile. For piston position with 75 % intake port closure, the jet-like axial velocity profile at a cross-sectional plane close to the intake port changes back to a wake-like profile at the adjacent downstream cross-sectional plane. This is characteristic of a vortex breakdown. The non-dimensional velocity profiles show no significant variation with the variation in Reynolds number.
Journal of Marine Science and Technology, 2013, Vol 18, Issue 1, p. 133-143