Abstract
Since it is well known that the flow and spray characteristics are critical factors on the performance and emission in a direct injection diesel engine, this study aims to investigate the interaction between flow and spray characteristics. At first, in-cylinder flow distributions in swirl/tumble adaptor for 4-valve cylinder head of DI Diesel engine were investigated under steady conditions with different SCV angles mounted on the cylinder head by using 2-D LDV. It was found that swirl flow is more dominant than tumble on spray interaction in the engine. For the analysis, the in-cylinder flow was quantified in terms of non-dimensional rig swirl/tumble, mean flow coefficient, swirl ratio/tumble ratio. It was confirmed that the swirl ratio is controlled between 2.3 and 3.8 by changing SCV angles.
Spray characteristics of the intermittent injection also were investigated by using PDA system to measure droplet size and velocity. The analyses of the PDA results were carried out with Time Dividing Method. It was found that there is a correlation between the swirl flow and SMD. The droplet size and the velocity were found to be nearly constant value with SCV angles, while the swirl ratio become higher with smaller SMD. The swirl ratio was found to be helpful factor to the atomization of droplet.