Flame Quenching in the Micro-Chamber Passages of I .C. Engines with Regular-Symmetric Sonex Piston Geometry 2001-28-0002

Both physical experiments and detailed chemical kinetics studies establish that Sonex micro-chambers imbedded in the walls of the piston bowl of an I.C. engine generate highly reactive intermediate chemical species and radicals- which, when allowed to mix with the fresh charge of the next cycle in the main chamber, substantially alter the chemical kinetics of main chamber combustion. A much more stable overall combustion process is observed, requiring substantially leaner air-fuel ratios than normal, and with much lower ignition temperatures. The net result, without any efficiency penalty, is an engine with an “ultra-clean” exhaust and with a greater tolerance to a wider range of fuels. Crucial to this process is the quenching of the flame in the passages connecting the micro-chambers to the piston bowl. It is flame quenching which enables the incomplete combustion of the charge trapped in the micro-chamber cavities.

This qualitative study seeks to corroborate the conclusions derived from earlier experimentation concerning the role of flame quenching in the Sonex combustion system (SCS) and examines the relative importance of various key parameters on this flame quenching process. To enable focus on the flow characteristics and flame quenching around the passage between the micro and main chambers, the size of the numerical simulation for the regular bowl-in-piston SCS design is abridged by the use of symmetry. Chief among the corroborative numerical findings is the verification of height of the connecting passage between the micro-chamber and combustion chamber as the most important parameter affecting flame quenching, with an appropriately narrow passage (channel) being able to also trap the charge in the micro-chamber.