Engine Performance and Combustion Characteristics of Hydrogen in a Direct Injection Engine

Hydrogen's h1gh tlammabll1ty, low igmt1on energy, clean burnmg and h1gh flame speed are attractive advantages for use 111 internal combustion engines to attain high performance and efficiency_ To overcome volumetric efficiency loss, high NOx emissions and abnormal combustion, direct injection option is being studied_ Optimisation of the direct mjection strategies and understanding of the combustion processes are currently being studied in the automotive industry and research mstitutions In this study, the engine performance and combustwn charactenstics of hydrogen in a single cylinder direct injection engine was investigated. The engine was originally designed for CNG fuel with a compression ratio of 14: I_ To demonstrate practicality and ease of adoption, no modification was made to the engine_ Tests were carried out at full throttle for speeds from 1800 rpm to 4000 rpm. The effects of varying injection timing and air fuel ratio were studied for the purpose of finding optimised operations. Comparisons with CNG operation were made to demonstrate the potential of hydrogen direct injection to improve the engine performance_ The study has demonstrated that desp1te having to 'de-rate' the eng me tor pre-1gnit1on control at higher speeds, I 0% performance improvement can be achieved when operating on hydrogen at low engine speeds and WOT It was shown that full and late partial direct injection at stoichiometric operation would be desired for maximum performance_ At mtermediate speed, 3000 rpm, the operation at lambda 1.2 would be optimum for engine efficiency while maintaimng the performance. An indicated thermal efficiency of 46% would be possible at lower loads by runnmg the engine w1th unthrottled lean operation_ While the CO and THC emissiOnS were an order of magnitude lower than CNG, the NOx emission would be higher at low speed. Due to the degree of stratification, at close to stoichiometric, the NOx emission increased as SOl was advanced despite lower performance and peak cylinder pressure_ Operating at lambda higher than 1.3 y1eld low NOx emission, however the performance was much compromised