Simulation of exhaust waste energy recovery potentials using electric turbo compound in a turbocharged gasoline engine

Abstract

Thermal efficiency of a spark-ignited engine is normally in the range of 25 % to 35% and reciprocating engines represent a very large source of waste heat with most of the losses are from the exhaust, through coolant, by direct convection and radiation to the environment. There is a significant potential to expand waste heat recovery usage by tapping the large volumes of unused exhaust heat into useful energy such as electricity. The methodology involved in the thesis includes assessment of each waste heat recovery technology based on current developments, research trends and its future in an automotive application. It also looked into the potential energy recoveries, performances of each technology, other factors affecting the implementation and comparison for each technology. Finally, simulation of an Electric Turbo Compounding (ETC) was presented using a Ford EcoBoost as a baseline engine with modification using HyBoost setup modeled with the 1- Dimensional AVL Boost engine performance software. A validated 1-D engine model was used to investigate the impact on the Brake Specific Fuel Consumption (BSFC) and Brake Mean Effective Pressure (BMEP) and was run at full load conditions. The results showed a maximum reduction of 3.0% BSFC and a maximum increment of BMEP of 0.5 bar achieved at an engine speed of 2500 rpm, during the full load condition. The setup was also able to achieve 1 kW of power and up to 3.75 kW recovered from the exhaust heat. A comparison between the engine testing and 1-D engine model showed a good agreement at the full load conditions with a minimum BSFC Standard Deviation of 0.0206 at the engine speed of 3000 rpm.