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Vehicle manufacturers face mounting pressure to increase fuel economy and reduce vehicle tailpipe emissions in order to reduce the environmental impact of their vehicles and to meet ever more stringent regulations. Wrightbus have developed first generation single– and double–deck Hybrid Electric Vehicle (HEV) city buses, a number of which are in regular service in London and other cities. These buses utilise a series hybrid powertrain with a turbo-diesel engine, drive motors with total output powers between 120 kW and 170 kW and a DC electrical storage system. Fuel savings up to 30% have been achieved in service. This paper presents a literature review of hybrid vehicle modelling, and covers the work completed by Queen's University to create a software model of the Wrightbus HEV drivetrains in the Mathworks Mat-lab/Simulink environment. The model has been calibrated to several drivetrain configurations, including differing battery technologies, control systems and vehicle hardware.

An increase in global oil consumption, coupled with a peak in oil production, has seen the price of fuel escalate in recent years, and consequently the transport sector must take measures to reduce fuel consumption in vehicles. Similarly, ever-tightening emissions legislation is forcing automotive manufacturers to invest in technology to reduce toxic emissions. In response to these concerns, this project aims to address one of the fundamental issues with the Internal Combustion Engine - approximately one third of the fuel energy supplied to the engine is lost as heat through the exhaust system. The specific aim of this project is to reduce the fuel consumption of a diesel-electric hybrid bus by recovering some of this waste heat and converting it to useful power. This report details how turbocompounding can be applied to the engine, via the inclusion of a turbogenerator, and assesses its waste heat recovery performance.

In any internal combustion engine, the amount of heat rejected from the engine, and associated systems, is a result of the engine inefficiency. Successfully recovering a small proportion of this energy would therefore substantially improve the fuel economy. The Rankine Cycle system has been raising interest for its aptitude to produce systems capable of capturing part of this waste heat and regenerate it as electrical or mechanical power. By integrating these systems into existing hybrid engine environments, it has been proved that Rankine Cycle system, which is more than 150 years old, can play a major role in reducing fuel consumption. The use of such a system for waste heat recovery on a hybrid engine represents a promising compromise in transforming the thermal energy into electricity and feeding this electricity back to the vehicle drivetrain by using the in situ electrical motor system or storing it into batteries.