Methodology to estimate fuel's exergy in SI engines using Otto cycles principles limited by the knock

Montoya J.P.G.; Arrieta A.A. · Proceedings of the LACCEI international Multi-conference for Engineering, Education and Technology (2023)

Resumen

A novel methodology is proposed to estimate the exergy of liquid and gaseous fuels for spark ignition (SI) engines, based on the thermodynamics laws and two scientific methodologies, one for measurements of fuels methane number (MN), and other for estimation of gaseous fuels energy quality. Two engines were used 1) A CFR engine to measure fuel's critical compression ratio (CCR) and MN. 2) A hybrid diesel engine with a high compression ratio (CR) converted to SI using custom pistons for high turbulence intensity designed by CFD simulations, for biogas SI (BSI) combustion. In both engines, fuels with MNs ranging from 37 to 140 were used, biogases, methane, propane, and blends of biogas with methane/propane and hydrogen. The BSI engine combines diesel engines characteristics (high airflow inlet, and high combustion pressures) with SI engines characteristics (premixed combustion using SI for combustion phasing at the knocking threshold (KT)). The BSI engine was used to measure the fuels maximum electrical energy generation and thermal efficiency at the KT. Correlations between MN and research octane number (RON) were used to develop the methodology. Fuels exergy efficiency is estimated with fuels γ, hydrogen/carbon (H/C) ratio, and limited by fuels MN/RON. The methodology proposed correlates fuels exergy, fuels entropy, adiabatic flame temperature (Tad), and fuels exergy efficiency for Otto cycles limited by the knocking.

Instituciones: Universidad Tecnológica del Perú