Low Heat Rejection Engines – An Overview

This paper presents a general overview about the previous research efforts into Low Heat Rejection Engine (LHRE) concept. The purpose of this paper is to explain the effect of insulation on engine performance, heat transfer characteristics, combustion and emission characteristics. Many researchers have carried out a large number of studies on LHRE concept. Some of them are experimental work and many are theoretical studies. In the case of LHR engines almost all theoretical studies predict improved performance but many experimental studies show different picture. This paper analyzes the reason for this deviation. The operating conditions, under which the experimental and simulation studies are carried out, have been clearly discussed. The factors, which affect thermal efficiency, combustion, and exhaust emissions in LHR engine, are deduced and their influences discussed. Effect of fuel injection characteristics on LHR engine performance is also reviewed. It is concluded that much more research is needed to overcome the practical problems before LHR engines can be put into production.