Abstract
A recent work attracts attention to the difficulties of vehicle electrification. For mass production it is predicted the building of an electric car with a battery range of maximum 100 km, but the maximum limit of 30 km is not excluded /1/. A solution that is enjoying ever greater attention is the hybrid propulsion. This solution has great chances of application for a long time to come with regard to the Otto engine as it can still be used independently, having not yet exhausted its qualities. At the moment the Otto engine could use a combustion chamber that works according to the stratification principle of the air-fuel mixture, given its capacity of ensuring the burning out of lean mixtures. In this work the authors propose as a viable solution a combustion chamber with channels on the piston had /3/. This combustion chamber adapts relatively easy and efficiently to the requirements of the combustion process based on the mixture stratification concept. Its geometry, as well as its intensity and the structure of the internal movements of the mixture can be partially optimized ever since the design stage. The proposed combustion chamber must be inevitably equipped with direct injection, both as a functional requirement (a fuel jet enters the channel in the piston head after the closing of the admission valve) as well as to satisfy the most severe norm of pollution emissions which is EURO 6. The new combustion chamber concept with channels in the pistons head aims to perform the stratification of the air–fuel mixture in a new form in relation to the current solutions, combining the movement of opposed swirls generated by the squishing surfaces between the cylinder head and the piston with the tumble movement produced in the channels within the piston. The work researches in detail the intensity of the swirls, the impact of the opposed swirls in the channels, the formation of tumbles, their intensity and orientation, applying all the above to geometric methods of control. The movement research within the cylinder was made with computer programs and is highlighted in the related film and figures. In the end a complex correlation is established between the combustion chamber’s properties and the performances it can accomplish in regard to: the use of lean and very lean mixtures with beneficial consequences for the fuel economy and the reduction of pollution emissions, the use of large compression ratios and of the supercharge with minimum or no danger of knock, the great stability of the spark ignition, the more efficient filling up of the cylinder. The work defines several precision numeric criteria which allow the optimization of the combustion chamber.
Keywords: Combustion Chamber, Stratified Mixture, Tumble Movement, Swirls Movement, Channels in the Piston Head