Cycle Simulations of a Coal-Fueled, Reciprocating, Internal- Combustion Engine: the Role of Volatiles and Liquid Carriers

Abstract

An engine cycle simulation was developed to investigate the role of volatiles and liquid carriers on the combustion process and performance of a coal-fueled, reciprocating engine operating at 1000 rpm. Models for coal particle combustion and devolatilization, liquid droplet vaporization, fuel vapor combustion, cylinder heat transfer, piston work, and mass flow rates were combined with a thermodynamic analysis of the engine to yield instantaneous cylinder conditions and overall indicated engine performance. Four representative devolatilization rate expressions for bituminous coal were selecled from the literature for comparison in this study. With rapid devulatilization of the coal, no external energy source was necessary to ignite and completely combust the fuel for an initial (at BDC) gas temperature of 450 K. In contrast. for no volatile evolution, an initial gas temperature of 600 K was needed to achieve maximum engine performance. The initial gas temperature was identified as a significant parameter with respect to evaluating the ignition characteristics of coal fuels in engines. In addition to dry coal and dry coal-char (no volatiles), three coal slurries were considered: coal/oil.coal methanol. and coal/water. For the coal/oil and coal/water slurry fuels, maximum efficiency was obtained for an initial ges temperature of ahout 370 K and 575 K, respectively.