Experimental and simulation study of diesel/methane/hydrogen triple-fuel combustion progression in a heavy-duty optical engine

Abstract

Experiments were carried out in an optical engine, and the effects of hydrogen ratio on the combustion process of diesel/methane/hydrogen triple fuel combustion with 5% diesel fuel ratio were studied. The natural photometric images of the combustion process were recorded by a high-speed camera. Combined with the optical experimental results, the combustion process of methane and hydrogen mixture ignited by trace diesel oil was simulated. The development process of in-cylinder temperature, OH group and combustion components during combustion with different hydrogen ratios was studied. It is found that the increase of hydrogen ratio promoted the combustion, the ignition delay time and combustion duration were significantly reduced, and the heat release stage of combustion was also advanced. When the second derivative of the heat release rate is the largest, a low temperature ignition point is formed at the edge of the cylinder at first, and the flame expands with the increase of temperature in a short time. With the increase of intake pressure, the ignition delay period decreases at the same hydrogen ratio. High hydrogen ratio leads to more NOx emissions due to higher combustion temperature, and CO and CH4 emissions decrease with the increase of hydrogen ratio.