Internal combustion engines in hybrid vehicles

In this paper the use of internal combustion engines in hybrid powertrains is investigated. The substantial differences between the use of internal combustion engines in conventional and in hybrid vehicles mean that engines for hybrid vehicles should be designed specifically for the purpose. At the TNO Road-Vehicles Research Institute, internal combustion engines are adapted for dedicated hybrid applications, which have proven the ability to reach near-zero emission levels. Two examples of hybrid projects at TNO are presented, one showing the development of an optimized CNG engine for a hybrid urban bus, and one showing the research into a diesel hybrid powertrain for passenger cars. Besides the engine adaptions, special attention is given to the determination of the hybrid power control strategy, because of its major importance to the actual operating behaviour of the internal combustion engine.