Optimizing charge stratification in a lean-burn spark ignition engine

This paper uses a new injection mode named as In-Port Twice Fuel Injection in spark ignition engines for improving lean mixture combustion. The total amount of fuel for each cycle is divided into two parts. One part is injected to offer a lean homogeneous mixture for the whole combustion chamber, and the other part is injected to form a mixture of local stratification around the spark plug in virtue of intake airflow and timed injection. Some experiment results gained in a 5-valve engine prove that this new injection mode can decrease fuel consumption by 17%, and also extend lean-burn ability by 2 units of air-fuel ratio and reduce emissions concentration by 30%-50% lower than the conventional injection mode with lean-burn. The air-fuel mixture strength can be adjusted arbitrarily both in the spark plug region and in the other room of the combustion chamber by means of controlling the ratio of fuel divided. The technique of In-Port Twice Fuel Injection opens up a new way to optimize the in-cylinder charge distribution in spark ignition engines.