Experimental and numerical investigation of swirl enhancing grooves on the flow and combustion characteristics of a DI diesel engine

This paper discusses the results of numerical and experimental investigations carried out with swirl enhancing modifications on a DI diesel engine. Six tangential holes on each piston with diameters of the hole varying from 2, 2.5, 3 and 3.5 mm are made in the piston with suitable inclinations with respect to the cylinder axis. Numerical investigations are carried out at full load condition with the modified engine piston. Results reveal that the tangential hole, of 2.5 mm produce a better combustion and higher pressure. The swirl motion as well as kinetic energy increases with the increasing hole diameters. The piston with 2.5 mm hole produce a highest performance improvement while the pistons with higher diameter than 2.5 mm produce a slightly lower performance. While the increase in diameter increases the flow field characteristics like swirl, the performance declines beyond 2.5 mm. Considering the performance point of view a 2.5 mm diameter hole provides better combustion and hence highest pressure for the same fuel injected. The other holes like 2.5 mm, 3 mm and 3.5 mm have slightly higher soot emission. Since numerical results proved that 2.5 mm provides a better performance, only three tangential holes 2 mm, 2.5 mm and 3 mm were taken up for experimental investigation. Of all the modifications the 2.5 mm piston gives better performance with higher brake thermal efficiency and lowest soot emission. (C) 2016 Elsevier Ltd. All rights reserved.