Abstract
To get rid of the combustion instability and knock in combustion of low-concentration coalbed methane in the large-bore engine, the combustion-supporting effect of passive pre-chamber was studied, exploring the influence of passive pre-chamber igniting position on the combustion in pre-chamber, jet characteristics and overall combustion. Three-dimensional fluid simulation was conducted to study the influence of igniting positions on the combustion performance of the engine by setting a fixed ignition time and changing the igniting position.The results show that as the igniting position lowers, the combustion rate in the pre-chamber slows down, the combustible mixture escaped from the nozzle hole during the cold jet duration decreases, and more heat is used for the hot jet to ignite the combustible mixture in the main combustion chamber. When the igniting position is 2mm away from the bottom of pre-chamber, the indicated thermal efficiency of the engine reaches its best, which is 1.6% higher than the one at original igniting position.