Qualitative Flow Field Studies of Combustion in I.C. Engines Using a Simplified Sonex Bowl-in-Piston Geometry

This study qualitatively examines pressure exchange, fluid flow and charge trapping in the combustion process of I.C. engines in which Sonex micro-chamber cavities have been imbedded inside the walls of the piston bowl. The geometry of these micro-chambers serves to generate intermediate chemical species and radicals by quenching the flame in the passages connecting the micro-chambers to the piston bowl, thus allowing incomplete combustion of the charge trapped inside the cavities. It is established from experimentation that, when the products of this incomplete combustion are then allowed to mix with the fresh charge of the next cycle in the main chamber, there is a significant change in the chemical kinetics of the main chamber combustion. The overall combustion process can be made to operate with good stability at substantially lower ignition temperatures and leaner air-fuel ratios than normal … resulting in an ultra-clean exhaust.

Also considered in this study are the basic effects of the Sonex piston geometry modification on flame propagation near and in the channel (passage) between the micro-chamber and the main chamber. Because of the complexity of the physics involved and the need for only qualitative results to enhance understanding of the basic phenomenon involved, the numerical size of the full-simulation is abridged through the use of symmetry and simplified geometry.

Among the findings presented, the work corroborates the existence of high-velocity radical-laden jets emanating from the micro-chamber during the later two-thirds of the power stroke and conclusively demonstrates the charge trapping process. Also the study shows the strong interaction between the heat release rates in the squish area of the main chamber and flow fluctuations in the passage of the micro-chamber during the first one third of the power stroke.