Heat loss is one of the greatest energy losses in engines. More than half of the heat is lost to cooling media and exhaust losses, and they thus dominate the internal combustion engine energy balance. Complex processes affect heat loss to the cylinder walls, including gas motion, spray-wall interaction and turbulence levels. The aim of this work was to study and improve the heat transfer characteristics of conventional diesel combustion. Speed, load, injection pressure, swirl level, EGR rate and air/fuel ratio (λ) were varied in a multi-cylinder engine. Temperature measurements in the engine cooling media were used to set up the engine energy balance and find out how much heat was lost to cooling media in different parts of the engine. Based on these calculations and heat release analysis, conclusions could be drawn regarding how heat losses in different parts of the engine were affected by changes in these parameters. Load was found to be more influential than speed, swirl did not have any effect on heat transfer, and EGR and λ both increased cooling water losses while piston losses were reduced.

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