Abstract
This paper explores the use of Liquefied Petroleum Gas (LPG) fuel in a 1.5 liter Spark Ignition (SI) four cylinder gasoline engine with double over head camshafts, four valves per cylinder equipped with a novel mixture preparation and ignition system comprising centrally located Direct Injection (DI) injector and Jet Ignition (JI) nozzles. The engine is turbocharged for high power density and high efficiency running lean. The LPG fuel is injected in liquid phase in the main chamber. The new generation fast actuating, high pressure, high flow rate injector is capable of injection shaping and multiple events and produces bulk lean stratified mixtures. The jet ignition system uses a second direct injector to inject a small amount of fuel in a small pre chamber, where a spark plug ignites a slightly rich to stoichiometric mixture then igniting the main chamber mixture through multiple jets of hot reacting gases. Bulk ignition and combustion of the lean, jet controlled, stratified main chamber mixture resulting from coupling DI with JI enables high efficiency burning of main chamber mixtures with fuel-to-air equivalence ratios reducing almost to zero for a throttle less control of load diesellike.
Keywords: Gas engines, direct injection, bulk jet ignition, lean burn stratified bulk combustion.