Experimental evaluation of laser ignited hydrogen enriched compressed natural gas fueled supercharged engine

•HCNG mixtures tested in PFI supercharged prototype engine in LI and SI modes.•Maximum cylinder pressure decreased with supercharging of HCNG-air mixtures.•In boosted prototype engine, BSFC in LI mode reduced with hydrogen enrichment.•BTE was higher in LI mode compared to SI mode for all HCNG mixtures.•Increased boost for HCNG mixtures reduced BSNOx emissions in LI mode. Laser-induced ignition could be the most promising alternative to conventional spark ignition, in order to reduce engine-out emissions. A single-cylinder naturally aspirated, water-cooled, direct injection diesel engine (Kirloskar, DM-10) was adapted/ modified to supercharged spark ignition (SI)/ laser ignition (LI), port fuel injection (PFI) gaseous fueled engine operation at a compression ratio (CR) of 11, and the experiments were conducted at a constant engine speed of 1500 rpm. Compressed natural gas (CNG), Hydrogen (H2) and HCNG mixtures (CNG & H2 mixed on a volume basis) were used as test fuels in this study. Comparison of LI vs. SI mode of ignition was investigated for combustion, performance, and emission characteristics of different HCNG mixtures under identical maximum brake torque (MBT) timing of 31°CA bTDC with an increased boost. For HCNG experiments, a dynamic HCNG mixing system was designed and developed, which delivered HCNG mixtures of desired composition on demand dynamically to the engine. It was observed that during supercharging or boosting the engine, 0.1 bar boost was optimum boost. At optimum boost, engine torque increased in LI mode compared to SI mode and it varied from 29 Nm to 32.5 Nm for CNG and from 20 Nm to 24 Nm for H2. Maximum peak in-cylinder pressure (Pmax) reduced with H2 enrichment of CNG. Pmax was 47.62 bar for CNG, which reduced to 39.77 bar for 40HCNG. At optimum boost, LI mode improved brake thermal efficiency (BTE) from 36.9% to 37.82% for CNG and from 37.7% to 38.6% for 40HCNG. Brake specific fuel consumption (BSFC) in LI mode reduced from 0.20 kg/kWh for CNG to 0.180 kg/kWh for 40HCNG. In LI mode, exhaust gas temperature (EGT) reduced. In LI mode at 0.15 bar boost, BSCO, and BSNOx emissions reduced with H2 enrichment.