Abstract: A combustion method for an internal combustion engine which prevents the occurrence of engine knock and improves fuel consumption and economy, by spray injecting part of the fuel used in one cycle into a combustion chamber, performing preliminary combustion of a diluted air-fuel mixture below combustible limits at a temperature lower than the self-igniting temperature of the fuel, then injecting the remaining fuel into the combustion chamber, and performing main combustion by flame propagation using spark plugs as ignition sources. Accordingly, the combustion method for an internal combustion engine of the present invention can attain stable combustion even at high air-fuel ratios and makes high compression ratios possible.

Abstract: In a reciprocating internal-combustion engine of a low-temperature catalytic-combustion type, catalyst layers which act at low catalyst temperatures of about 500.degree. C. or downwards to permit combustion of a gaseous air-fuel mixture are formed or secured on the inner wall surfaces of each combustion chamber of the engine, whereby low-temperature catalytic combustion of the air-fuel mixture is made possible in quench layer formed along the inner wall surfaces of each combustion chamber separate from its piston-sliding region, whereby incomplete combustion is prevented, a regular operation is made possible even with a dilute gas mixture having air-fuel ratio exceeding the limit of misfire in the conventional engines, the fuel efficiency is enhanced and the reduction in hydrocarbon, CO and NOx in exhaust gas is attained as well.