Control of heat release in engine combustion chamber by multiple flames (A research on the reduction of NOx by controlling the heat release process)

Combustion in the cylinder of an internal combustion engine requires a short but finite time to occur. Since the combustion is usually controlled by a fuel mixture supply and an ignition timing depending on the required load, the combustion characteristics cannot actively be changed once ignited. However, if the combustion is achieved in several zones in the combustion chamber, and the ignition of each zone is independently controlled by either the multiple direct injections coupled with an individual ignition or the multiple ignitions in a premixed charge, the process may positively be changed during combustion period. The effect of ignition timing control by the multiple flames on the combustion process of the test engine is investigated in the present study. The multiple flames are initiated from two ignition sources located around the disk type combustion chamber or by the sequential ignition from one ignition source. Depending on the separately controlled ignition timing of each electrode and the swirling speed at the ignition point, a growth of flame area and a separation between flames can be controlled using the single combustion test engine fueled with methane. The ignition timing retard is effective for reducing NOx at the sacrifice of a fuelmore » economy, when the combustion process after ignition is not properly adjusted. A qualitative evaluation of the cycle performance related to the combustion process, using the simulator reformed for the purpose of the present case, and an approximated Wiebe function for the experimental heat release rate, shows that the optimum processes under these combustion control may exist.« less