An experimental study of energy balance in low heat rejection diesel engine

Effects of thermal barrier coating on gas emissions and performance of a LHR engine with different injection timings and valve adjustments

The fundamental driving force for the development of thermal barrier coatings has been the continuing quest for ever higher temperatures in gas turbines. Over the period 1940–1970, the temperature capability of superalloys for gas turbine blades, which is defined in terms of 100 h life at 20000 psi (138 MPa) stress, was increased from approximately 1400°F (760°C) to 1900 °F (1040 °C) [1]. This was a costly process which required the development of numerous generations of new superalloys. It was a necessary and successful step, however, in producing the highly reliable and efficient gas turbine engines that we know today. Between 1940 and 1970, higher temperature superalloys, along with improved engine design, allowed specific fuel consumption to be reduced by more than half, thrust-to-weight ratios to be tripled, and time between overhaul to be increased from less than 100 h to over 12000 h [1]. A recent review of the effect of materials on current and future gas turbine performance has been given by Kool [2].

Thermal barrier coatings

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.

Low Heat Rejection Engines – An Overview

The Effects of Ceramic Coatings on Diesel Engine Performance and Exhaust Emissions

Experimental investigations were made with a single-cylinder direct-injection Diesel engine with heat-insulated piston. The most important result is an inferior economy compared with the not insulated aluminum-piston engine. It was found that this phenomenon is not caused by neither a changed combustion process nor increased blowby nor different friction losses, but rather by a drastic increase of the heat transfer coefficient during the first part of combustion with increasing surface temperature. This is taken into account in a modified equation for the heat transfer coefficient. Cycle-simulations using this modified equation show that there is neither a gain in fuel economy of naturally aspirated nor of turbocharged nor of turbocompound Diesel engines with ''heat insulated'' combustion chamber walls.

Walter Spindler

Papers

Heat insulation of combustion chamber walls ― a measure to decrease the fuel consumption of I.C. engines?