Global energy balance in a diesel engine with a thermoelectric generator

Abstract

The best possible thermal and mechanical energy management is necessary to have more efficient and less pollutant means of transport. This can be accomplished recovering part of the energy lost through exhaust systems in internal combustion engines. One of the devices able to recover this waste thermal energy is a thermoelectric generator. Plenty of works about their design have already been presented but their effects on the energy fluxes of the engine, which are crucial to the future thermal management of vehicles with thermoelectric generators, have not yet been studied in a comprehensive manner. A thorough and novel experimental analysis of the behavior of the main energy fluxes in a diesel engine with a thermoelectric generator was accomplished, an approach not already followed in previous literature. Due to their higher air-to-fuel ratio, in diesel engines is more difficult to recover exhaust energy. Furthermore, this study was conducted in the most adverse for energy recovery but most used part of the engine map, i.e. common driving conditions, and not only at high loads. Conditions in which thermoelectric generators could be more beneficial and less harmful to the efficiency of the engine were identified. It was found that thermoelectric generators can improve the global efficiency of internal combustion engines despite the low efficiency of current thermoelectric materials.