Numerical Study on Exergy Losses of n-Heptane Constant-Volume Combustion by Detailed Chemical Kinetics

Abstract

A theoretical numerical analysis on the roles of initial charge temperature, initial pressure, equivalent ratio, and oxygen concentration in exergy loss events of the n-heptane adiabatic constant-volume combustion process by detailed chemical kinetics was explored, based on computing the various entropy generation terms among chemical reactions. Three apparent peaks are observed in the overall exergy loss rate, so the combustion process is classified as Stage 1 (large molecule fuels → small molecule fuels), Stage 2 (small molecule fuels → H2O2 loop reactions → CO), and Stage 3 (oxidation of CO, H, and O to final products CO2 and H2O). It was observed that the exergy losses are relevant to exergy loss rates together with durations of the reactions, and the durations always have more dominant effects on deciding the exergy losses. A trade-off relation between exergy loss and incomplete conversion loss was also observed, and ways to reduce the total loss of combustion processes were determined by investigating the influences of multiple parameters on loss distributions.