Analysis of thermodynamic scope engine simulation model empirical coefficients: Suitability assessment and tuning of conventional hydrocarbon fuel coefficients for bio syngas

Assessment of producer gas thermo-physical properties indicates four times higher thermal conductivity of producer gas (40.0 mW/mK) compared to gasoline (11.2 mW/mK), attributed to the presence of hydrogen. The influence is on convective cooling which is reflected in about 32% cooling load as against 25% for spark ignited engines. In response, the Reynolds number power coefficient of convective heat transfer correlation nearly doubles from 0.35 to 0.76. Analysing laminar flame speed coefficients, the inability of CHEMKIN-III to accurately predict laminar flame speed of hydrogen containing gases requiring adoption of CHEMKIN-II is a key observation. Substantial deviations are also observed for apparent heat release profiles with extended terminal stage combustion duration for producer gas, attributed to enhanced convective cooling. Curve fit analysis evolves producer gas specific shape and efficiency coefficients of 0.71 and 2.23 as against 2.0 and 5.0 for conventional fuels. The terminal combustion duration also changes from 1.22 to 2.12 ms. Using tuned coefficients permits near concurrent evolution of simulation and experimental pressure and heat release profiles establishing the need for fuel specific coefficients.