S.I. Engine Combustion Flame Propagation Measurement and Knocking Analysis by Ion Current Probes Including Moving Intake and Exhaust Valve Faces 2007-01-1420

In S.I. Gasoline Engines, knocking constrains allowable highest compression ratio which means improvement of fuel consumption and power output that is restricted by possible ignition timing advance. This study started in order to research methods to reduce or eliminate knocking. Firstly it is important to observe flame propagation precisely in order to recognize the knocking phenomenon. For that purpose, ion-current probe method is adopted and 92 ion-current probes are mounted to cover whole combustion chamber wall especially including moving intake and exhaust valve faces to eliminate blank area. As a result, extremely fine observation of flame propagation has been realized. Simultaneously by using two combustion pressure sensors, the pinpoint position of start of knocking can be determined. In every case the position is at some distance from the engine bore wall and then rapid flame propagation to the bore wall is observed contrary to the previous knowledge. This phenomenon is also described in this paper on the conditions of supercharged or different gasoline octane number.