Modelling and simulation of conventional turbocharged and electrically assisted turbocharged automotive diesel engine

Increasing charge air density by utilizing a turbocharger or a supercharger is indispensable method to engine downsizing with high power density and lean boosting for reducing the fuel consumption in diesel engines. Supercharging system suffers from fuel consumption penalty because of compressor powered by engine output. Turbocharging system utilizes wasted exhaust energy that means compressor powered by exhaust turbine but has a turbo lag problem. The electrically assisted turbocharger that can eliminate turbo lag problem and fuel consumption penalty is the topic of this thesis. The experimental work of matching an electrically assisted turbocharger to an engine is rather expensive, it was therefore decided to simulate conventional turbocharged automotive diesel engine and validate with experimental results and subsequently electrical device acting as motor/generator was integrated to the model and effects of electrically assisted turbocharger on diesel engine performance parameters were analyzed. In this study, one dimensional computer simulation programmed named Boost developed by AVL used for the engine simulation. A lot of experimentally obtained data, flow coefficients of the engine valves, turbine and compressor maps, intercooler, cylinder and combustion parameters, etc., were applied to enhance the accuracy of the simulation model. Good agreement of the simulated and measured results achieved for the steady state and transient operation of the conventional turbocharged diesel engine. Therefore the simulation extended to deal with steady and transient behavior of a turbocharged diesel engine that is electrically assisted. Simulations results revealed that electrically assisted turbocharger increases low-end torque and improves transient response and fuel consumption of conventional turbocharged diesel engine.