Experimental study on effects of compression ratio, ignition timing, and hydrogen addition on ignition delay and combustion rate of heavy-duty truck engine fueled with liquefied methane

Natural gas (NG) is a potential alternative fuel for carbon neutral and has been received increasing attentions on its combustion behaviors in engine. However, there is little systematic quantitative investigation on the combustion characteristic of purified NG (methane) engine. In this study, the sweeping tests for compression ratio (CR), ignition timing, and hydrogen addition were conducted on a heavy-duty truck liquid methane engine, and the influence factors of ignition delay and combustion rate at each stage were quantitatively investigated. Some new findings and interesting conclusions were obtained. Overall, CR especially the higher CR has small effect on the ignition delay of methane engine (less than 2 deg). Under all the conditions discussed, the ignition delay almost linearly increases with the advance of ignition timing, resulting in the slight advance of start of combustion (SOC). Compared with ignition timing, hydrogen addition has larger effect on SOC since it reduces ignition delay largely (up to 7.3 deg at 1400rpm). By increasing hydrogen addition, the CA10-50 shortens slightly while CA50-90 elongates largely, resulting in a rising trend in CA10-90 finally. All these have extended the research on methane engine and are useful to improve its combustion performance.