Study of Turbulent Entrainment Quasi-Dimensional Combustion Model for HCNG Engines with Variable Ignition Timings 2018-01-1687

Presently, urban transportation highly depends on the fossil fuels, but its rapid fluctuating economic issues and environmental consequences impose the variegation of energy sources. Hydrogen enriched compressed natural gas (HCNG) engines offer the potential of higher brake thermal efficiency with low emissions, which also satisfies the strict pollutant emission standards. The two-zone turbulent entrainment quasi-dimensional combustion model is developed to predict the combustion process of spark-ignited hydrogen enriched compressed natural gas-fueled engines. The fundamentals of thermodynamic process, turbulent flame propagation model and other sub-models like laminar burning velocity, adiabatic temperature and ignition lag model are introduced for the better accuracy. The experiments have been conducted for three different fuels; pure CNG, 20% HCNG, and 40% HCNG blends under MAP of 105 kPa for various excess air ratios (λ) and ignition timing (θ_i). The three calibration coefficient of the model; Turbulent intensity coefficient C₂, the Taylor length scale coefficient C₃, and Ignition lag coefficient C_ig are tuned to generate the pressure traces which closely resembled to experimental results. After comparing the numerical simulation results with the experiment’s outcomes it is found that the predictive accuracy of the presented model is quite impressive, and it is well accepted for the extremely fuel lean conditions where issues of bad combustion become serious.