Exergy assessment of combustion and EGR and load effects in DI diesel engine using comprehensive two-zone modeling

A model extended to include exergy terms is presented in this investigation, providing more useful results. It complements the energy analysis, based on in-house, validated, advanced, 2-zone combustion model, predicting performance and emissions in direct injection (DI) naturally-aspirated (N/A) diesel engine, operating at two loads with or without exhaust gas recirculation (EGR), with implementation on test results from a diesel obtained by the authors. The exergy terms of each of the two zones (unburned and burned) are identified and computed discretely, while charge chemical exergy is considered. The accurate account of temperature and chemical species histories in the burned zone and the mass entrainment from the unburned zone can lead to a more precise evaluation of the exergy terms of the whole cylinder content, against a single-zone combustion modeling, hence revealing the influence of zoning (presenting also entropy diagrams), which is important if irreversibility is computed from exergy balance. The effect of load is scrutinized and the investigation proceeds using various EGR rates, by keeping constant fueling rate. History diagrams of rate and cumulative exergy terms, for the total cylinder charge and each zone discretely, supply detailed information for the chemical exergy, irreversibility and losses. (C) 2020 Elsevier Ltd. All rights reserved.