CONVERSION OF DIESEL ENGINE INTO SPARK IGNITION ENGINE TO WORK WITH CNG AND LPG FUELS FOR MEETING NEW EMISSION NORMS

Abstract

Fluc tu at ing fuel prices and as so ci ated pol lu tion prob lems of largely ex ploited pe tro - leum liq uid fuel has stim u lated the re search on abun dantly avail able gas eous fu els to keep the mo bil ity in dus try in tact. In the pres ent work an air cooled die sel en gine was mod i fied suit ably into a spark ig ni tion en gine in cor po rat ing elec tronic ig ni tion and vari able speed de pend ant spark tim ing to ac com mo date both LPG and CNG as fu els. En gine was op ti mized for stoichiometric op er a tion on en gine dy na mom e ter. Ma te ri - als of a few in tri cate en gine com po nents were re placed to suit LPG and CNG ap pli - ca tion. Ig ni tion tim ing was mapped to work with gas eous fu els for dif fer ent speeds. Com pen sa tion was done for re cov er ing vol u met ric ef fi ciency when op er ated with CNG by in tro duc ing more vol ume of air through reso na tor. Ig ni tion tim ing was ob - served to be the per ti nent pa ram e ter in achiev ing good per for mance with gas eous fu - els un der con sid er ation. Per for mance and emis sion tests were car ried out on en gine dy na mom e ter and chas sis dy na mom e ter. Un der wide open throt tle and at rated speed con di tion, it was ob served that the peak pres sure with LPG was ly ing be tween die sel fuel and CNG fuel op er a tion due to slow burn ing na ture of gas eous fu els. As com - pres sion ra tio was main tained same for LPG and CNG fuel op er a tion, low CO emis - sions were ob served with LPG where as HC + NOx emis sions were lower with CNG fuel op er a tion. Chas sis dy na mom e ter based emis sion tests yielded lower CO2 lev els with CNG op er a tion.