Development and comparative experimental investigations of laser plasma and spark plasma ignited hydrogen enriched compressed natural gas fueled engine

A customized port-fuel-injection (PFI) SI engine was operated in spark ignition (SI) and laser ignition (LI) modes at varying brake mean effective pressure (BMEP) and relative air-fuel ratio (lambda) under naturally aspirated conditions. Test fuel used were hydrogen enriched compressed natural gas (HCNG) mixtures and results were compared with baseline CNG. For H-2 enrichment of CNG, a customized dynamic fuel mixing system was developed. For LI, a solid state Q-switched Nd:YAG laser (200 mJ; 30 Hz; 6-9 ns) was used, and the laser beam was focused using a converging lens of 50 mm focal length. Experiments of HCNG fueling exhibited relatively higher peak pressure (P-max) with its peak shifted closer to the top dead center (TDC). H-2 enrichment of CNG led to increase in peak in-cylinder P-max (by similar to 2.9 bar), RoPR (by similar to 0.72 bar/deg) and HRR (by similar to 7.2 kJ/m(3).deg) for 40HCNG compared to baseline CNG. The maximum BTE was observed to be similar to 42.8% (at lambda = 1.4) in LI mode for 30HCNG fueled engine. The lowest BSFC obtained were at lambda = 1.2 for HCNG in SI mode, while corresponding value in LI mode was obtained at lambda = 1.4. BSHC emissions were always lower for LI mode than the SI mode. At 3.96 bar BMEP, BSHC emissions reduced from 0.54 g/kWh (for CNG) to 0.35 g/kWh (for 40HCNG), which further reduced to 0.21 g/kWh (for H-2) in LI mode. BSNOx emissions increased with increasing BMEP but reduced from 0.89 g/kWh at lambda = 1.5 for CNG to 0.17 g/kWh for 30HCNG at lambda = 1.7 at 30 Nm load. (C) 2020 Elsevier Ltd. All rights reserved.