Performance and emissions of natural gas and hydrogen/natural gas blended fuels in spark ignition engine

The basic intent of the present work is to evaluate the potential of using alternative gaseous fuels like compressed natural gas (CNG) and H-2/CNG as a spark ignition (SI) engine (lean bum engines) fuel. Computer modeling of internal combustion engine is useful in understanding the complex processes that occur in the combustion chamber. This research deals with quasi-dimensional, two-zone thermodynamic simulation of four-stroke SI engine fueled with CNG and H-2/CNG. The fraction of hydrogen in the H-2/CNG blend, for simulation was varied from 0-60% by volume. The developed computer model has been used for the prediction of the combustion and emission characteristics of H-2/CNG blended fuel in SI engines, which includes the power, thermal efficiency, cylinder pressure-crank angle history, exhaust emissions (NOx and CO), fuel consumption, combustion duration, ignition delay, etc. Predicted results indicate that the presence of hydrogen in H-2/CNG blend can improve combustion duration as it has a higher flame speed. There are increases in oxides of nitrogen emissions, but decrease in carbon monoxide and hydrocarbon emissions, when comparing H-2/CNG blended fuel to neat CNG. The validity of the model has been carried out by comparing the computed results with experimental data obtained under same engine setup and operating conditions. The results obtained from the theoretical model when compared with those from experimental ones show a good agreement. Also, the effects of the many operating parameters such as equivalence ratio, engine speed, and spark timing have been studied.