Optimization, Numerical and Experimental Investigation of Performance and Emission Parameters in HCNG Fueled SI Engine

The global automotive and power generation sectors are facing severe challenges due to the rising demand for energy, depletion of fossil fuels, and stringent emission norms. Conventional fuels such as diesel, gasoline, and even compressed natural gas (CNG) have limitations related to combustion efficiency and emission control. To address these challenges, the present study investigates the optimization, numerical, and experimental analysis of a spark ignition (SI) engine fueled with hydrogen-enriched compressed natural gas (HCNG). The main objective is to evaluate and enhance the performance and emission parameters by optimizing hydrogen blending ratio, ignition timing, and crank angle position. A single-cylinder, four-stroke, variable compression ratio (VCR) SI engine was used for experimentation. The engine was operated on pure CNG and different HCNG blends (10%, 20%, and 30% hydrogen by volume) under varying load and speed conditions. Parameters such as brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), and major exhaust emissions (CO, HC, NOx) were recorded. Numerical analysis and experimental observations indicate that with the increase of hydrogen fraction in the blend, combustion improves due to the higher flame speed and lower ignition energy of hydrogen. Consequently, BTE increases by approximately 6–8%, and CO and HC emissions reduce by 20–35%. However, an increase in NOx formation was observed at higher hydrogen concentrations because of elevated in-cylinder temperatures. The optimized blend ratio was found to be around 20% hydrogen, which provides the best trade-off between enhanced engine performance and acceptable emission levels. The study concludes that HCNG is a viable transitional fuel that bridges the gap between conventional fossil fuels and future hydrogen-based energy systems. The findings of this investigation contribute to cleaner combustion technology and sustainable energy solutions for the automotive industry.