Pulsed jet combustion—Key to a refinement of the stratified charge concept

Pulsed jet combustion, PJC, is initiated by an efflux of products of spark ignited rich airfuel mixture emanating from a small pre-chamber cavity that can be accommodated in a conventional ignition plug of an engine, its volume being of an order of 0.5 cm 3 . The jet plume produced thereby at the exit orifice displays the characteristic features of turbulent shear layers where convection associated with entrainment and engulfment provide the predominant mechanism for the propagation of the process, in contrast to the conventional system of a flame traversing the charge, FTC—a process governed by diffusion. Reported here is an experimental study of the early, active stage of PJC—a process dominated by turbulent convection. A particularly noteworthy feature of this mode of combustion is that the residence time of the reacting medium in the zone of essential chemical activity—the region of an appreciable concentration of active radicals—is effectively prolonged, being located in the cores of large scale vortex structures, the essential components of the flow field of a turbulent jet plume. It is for this reason that the PJC system is introduced here as a key to a refinement of the stratified charge concept, offering the prospects of reduced formation of pollutants in engines, combined with their increased efficiency and multi-fuel capability. Moreover, one may visualize, using a number of electronically activated PJC generators per cylinder could lead to the development of engines where the process of the evolution and deposition of exothermic energy, the essential elements of heat release, are externally controlled by a microprocessor system.