Passive Pre-Chamber Spark Plug Development, Optical Analysis and Mass Production Feasibility

Prechamber ignition is a means to further optimize the internal combustion engine in terms of knock resistance and thus efficiency. The flame plumes emitted by the prechamber lead to a faster flame propagation especially to the outer circumference of the combustion chamber. The paper describes the development and the features of this passive pre-chamber spark plug including layout, CFD simulation, thermal simulation and testing up to a prototype vehicle. Specialties like AVL’s residual gas chamber, which allows zero load operation, are described. Together with Tenneco a production feasible solution of this passive pre-chamber is developed. The way from the prototype to the functional production feasible part is described. Design features as well as simulation results are described. A specific part of the paper is reserved for optical analysis of prechamber spark plugs as this represents a straightforward tool for developing against some deficiencies allocated with prechamber spark plugs such as catalyst heating, starting and low load operation. We report on some principal thermodynamic and visual analysis of ignition and flame propagation in a passive PC system with documentation of ignition and combustion behavior including the limits of ignitability and misfires. High load operation, on the other hand, needs to observe limits arising from PC component temperatures. Here, thermal imaging of the pre-chamber’s internal surfaces and especially the spark electrodes, provides understanding of temperature limits and gives guidance for well controlled thermal conditioning of the PC’s contacting surfaces.