Internal combustion engines fueled by natural gas—hydrogen mixtures

Abstract In this study, a survey of research papers on utilization of natural gas–hydrogen mixtures in internal combustion engines is carried out. In general, HC, CO 2 , and CO emissions decrease with increasing H 2 , but NO x emissions generally increase. If a catalytic converter is used, NO x emission values can be decreased to extremely low levels. Consequently, equivalence zero emission vehicles (EZEV) standards may be reached. Efficiency values vary with H 2 amount, spark timing, compression ratio, equivalence ratio, etc. Under certain conditions, efficiency values can be increased. In terms of BSFC, emissions and BTE, a mixture of low hydrogen percentage is suitable for using.