The Potential of Exhaust Waste Heat Use in a Turbocharged Diesel Engine for Charge Air Cooling

Even a basic analysis of the use of fuel energy in a combustion engine would indicate that one-third of fuel energy is converted into exhaust waste, which is released into the environment. The scale of energy loss encourages scientists to try to consider the waste heat of exhaust gases as a potential source of useful energy. It is a standard today that waste heat is commonly used to power a turbocharger applied to internal combustion engines. Waste heat can also be used to drive an adsorption cooling system for air-conditioning inside the car. The drawback of that solution is complexity of the system and size of adsorption bed which make it not suitable for automotive industry use. The concept of increasing the capability of vehicles’ turbo engines can boost performance of turbo-charged engines through extra cooling of air being impelled into the combustion chamber of the engine. Cooling of the charge inside the intake manifold saves fuel and reduces nitric oxide emissions in exhaust gases. The paper presents a turbo cooling system that consists of one exhaust gases driven turbocharger and one air-driven turbocharger. Since the turbochargers are connected in parallel it further lead to the temperature decrease of intake air and enlarges the system boundaries to use excess cool air, e.g. for car air conditioning. A thermodynamic model is shown. The model was developed using mass and energy balance data for each component of the system. Diesel engine simulation results are discussed in the paper. Results show high potential of decreasing intake air temperature. The use of the new system resulted in a reduction of fuel consumption by about 1%. It was our observation that reduction of the fuel consumption was mainly related to the increase of the energy efficiency ratio for the cooling device operation process.