Search Results

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 adapter 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 effects of tumble flow generated by various intake ports on the lean burn characteristics in a four-valve pentroof engine were investigated. Tumble intensities were tested for three intake ports of different entry angle; 25°, 20° and 15°. The flow characteristics in cylinder were measured under motored conditions with laser Doppler velocimetry. The lean burn performances were examined in an operating 4-cylinder engine. The combustion duration under lean mixture conditions were calculated by heat release analysis of the pressure trace. The flame developments in a single-cylinder optical engine were visualized with an image-intensified CCD camera to see the effect of different flow patterns with three inlet ports of strong and weak tumble. It was found that there is a correlation between the stronger tumble during induction and the higher convective velocity and turbulence levels at the time of ignition, which result in faster and stable combustion under lean mixture conditions.