A study using PIV of the intake flow in a diesel engine cylinder

The admission flow generated by a parallel valve diesel engine cylinder head was investigated by planar and stereoscopic Particle Image Velocimetry in a steady flow test bench through measurements in the swirl and tumble planes. By combining several sets of measurements a full three-dimensional, three-component reconstruction of the flow was made. The flow out of the valves forms a jet which collides with the cylinder wall before flowing down along the wall. Despite the fact that there is no piston a recirculation bubble is formed in the tumble plane. This is due to the entrainment of gas into the jet which needs to be replaced and thereby sets up a counter flow. In the swirl plane complex jet-dominated vortex structures are detected close to the cylinder top. Moving away from the cylinder top, a counter-rotating vortex-pair structure is observed from which a single coherent swirling structure develops further down the cylinder. Some clear differences are observed between the flow at high and moderate valve lifts, which correspond to a distinct change in the swirl intensity. By introducing a strong swirling motion the flow is stabilized which can be seen by tracking the instantaneous position of the swirl centre. For high swirl the variation of the position of the swirl centre decreases substantially.