Investigation of the Bowl-Prechamber-Ignition (BPI) Concept in a Direct Injection Gasoline Engine at Part Load

In this work a new concept for GDI engines is presented. Concerning a stable ignition a main goal of the so called Bowl-Pre-chamber-Ignition (BPI) process is to reduce the influence of varying flow and spray effects. The characteristic signs of the concept are the dual direct injection, a centrally arranged piston bowl and the special pre-chamber spark plug, that partly dips into the bowl at TDC. During that process most fuel is injected early (intake stroke) into the intake manifold or directly into the cylinder to form a homogeneous pre-mixture. Later in the compression stroke, only a small amount of fuel is injected into the piston bowl. So formed locally stratified charge mixture is transported by the piston bowl to the pre-chamber-spark plug, the pre-chamber dips into the bowl and the mixture flows directly to the spark plug electrode. The result is a very stable lean combustion.

The BPI-concept has been applied to a modified 4-Valve 4-Stroke engine and first results of numerical and experimental investigations are presented. The injection, the charge stratification and also the dip-in-flow has been demonstrated by transient 3D-CFD simulation. The different injection modes and the combustion stability has been shown by measurements.