An exergy analysis methodology for internal combustion engines using a multi-zone simulation of dual fuel low temperature combustion

Abstract

Increasing fuel efficiency of internal combustion (IC) engines is an imperative economic and environmental need. To this end, in the present work, an exergy analysis methodology was developed and incorporated within a previously validated, closed cycle, multi-zone, thermodynamic simulation of diesel-methane dual fuel low temperature combustion (LTC). To study in-cylinder exergy transformation, the diesel start of injection (SOI) was varied from 300 crank angle degrees (CAD) to 340 CAD for a fixed engine load 6 bar brake mean effective pressure (BMEP) and speed (1700 rev/min). Gross indicated fuel conversion efficiency (iFCE) and exergetic efficiency (including exhaust exergy at exhaust valve opening) were computed for different SOIs. Results show that at all SOIs ~41–42 percent of the total input exergy was destroyed due to combustion irreversibilities. When combustion started, in-cylinder chemical exergy reduced significantly due to exergy transfers associated with work transfer and heat transfer as well as exergy destruction. While at SOI = 340 CAD (representative of conventional dual fuel combustion), ~14 percent of the fuel chemical exergy exited as exhaust physical exergy, this reduced to ~5.5 percent at SOI = 300 CAD (representative of dual fuel LTC). The “maximum efficiency SOI” was SOI = 310 CAD with an iFCE of 43.6 percent and an exergetic efficiency of 52.2 percent.