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This paper investigates theoretically the effects of heat transfer characteristics, such as crank-angle phasing and wall temperature swings, on the thermodynamic efficiency of an IC engine. The objective is to illustrate the fundamental physical basis of applying thin thermal barrier coatings to improve the performance of military and commercial IC engines. A simple model illustrates how the thermal impedance and thickness of coatings can be manipulated to control heat transfer and limit the high temperatures in engine components. A friction model is also included to estimate the overall improvement in engine efficiency by the proper selection of coating thickness and material.

A technique of calculating the evolution of turbulence during the combustion phase of a reciprocating engine cycle is presented. The method is based on a local linearization of the full non-linear equations of motion. It is valid when the turbulence is distorted more rapidly by the changes in mean flows than it interacts with itself. The theory requires as input strain rates of the deterministic mean motion, and the initial state of turbulence. Calculations are presented for the particular case of a cylindrical chamber geometry. In the burning process it is assumed that the spark plug is located on the cylinder axis and the strain field is that established by the flame front. The theory calculates the turbulence parameters during the combustion period. Combustion rates, and durations, as a function of equivalence ratio and the initial turbulent and thermodynamic conditions.

This paper reviews the phenomoneological modeling of the combustion processes for the diesel and fuel-injected stratified charge engines. Distinctions are made between phenomenological and multi-dimensional finite-difference approaches. The modeling methodologies and the basic components in these models are described. These include characterization of the fuel spray, fuel-air mixing, ignition, burning and heat transfer processes. An attempt is made in the paper to highlight the similarities and contrasts of various models and relate to their utility in addressing emission research and engine performance development objectives.

The performance and heat transfer characteristics of a single cylinder diesel engine in the metal and in the ceramic-coat-insulated configurations were compared at the same speeds, loads and air flow rates. Compared to the metal engine, the insulated engine had a higher brake specific fuel consumption which was attributed to a slower combustion process; the exhaust as well as the time averaged surface temperatures of the insulated engine were higher. The unsteady heat flux amplitudes in the insulated engine were lower which suggested a lower overall heat flux. This lower heat flux was attributed to the lower flame temperatures because of the poor combustion quality in the non-optimized insulated engine.

Lowering lubricant viscosity to reduce friction generally carries a side-effect of increased metal-metal contact in mixed or boundary lubrication, for example near top ring reversal along the engine cylinder liner. A strategy to reduce viscosity without increased metal-metal contact involves controlling the local viscosity away from top-ring-reversal locations. This paper discusses the implementation of insulation or thermal barrier coating (TBC) as a means of reducing local oil viscosity and power cylinder friction in internal combustion engines with minimal side-effects of increased wear. TBC is selectively applied to the outside diameter of the cylinder liner to increase the local oil temperature along the liner. Due to the temperature dependence of oil viscosity, the increase in temperature from insulation results in a decrease in the local oil viscosity.