Abstract

In this study, the effect of enriching CNG with H₂ (called hythane) on engine combustion, performance and emissions were investigated using a prototype single cylinder supercharged engine at two different operating conditions (naturally aspirated & supercharged) with different ignition sources [spark ignition (SI) and laser ignition (LI)]. The blending ratios were varied using a customized dynamic mixing system. The effect on flame kernel growth and start of combustion (SoC) using Nd:YAG laser (@1064 nm; 40 mJ/ pulse) for different HCNG blends were studied in constant volume combustion chamber (CVCC) at initial chamber filling pressures of 5 and 10 bar and 100°C temperature respectively. CVCC results showed that increased initial chamber filling pressure from 5 bar to 10 bar, the 10% mfb or SoC became faster, however combustion duration (CD) increased. Increasing H₂ fraction reduced 10% mfb and CD for both pressures. Engine investigations showed that 30HCNG showed relatively earlier SoC, and lower coefficient of variation of indicated mean effective pressure (COV_IMEP) at all load conditions. Laser ignition increased the brake thermal efficiency (BTE) at lean operating condition (approx. 42% for 30HCNG), and extended lean limit to 1.7 and 1.8 for 30HCNG and 40HCNG respectively. BSNOx decreased as λ increased but increased with increasing H₂ fraction in the test fuel. Boosting resulted in slightly higher HC emissions due to lower in-cylinder temperatures.

© 2017 Optical Society of America