Alternative crankshaft mechanisms and kinetic energy recovery systems for improved fuel economy of light duty vehicles

The introduction of advanced internal combustion engine mechanisms and powertrains may improve the fuel conversion efficiency of an engine and thus reduce the amount of energy needed to power the vehicle. The paper presents a novel design of a variable compression ratio advanced spark ignition engine that also permits an expansion ratio that may differ from the induction stroke therefore generating an Atkinson cycle effect. The stroke ratio and the ratio of maximum to minimum in-cylinder volumes may change with load and speed to provide the best fuel conversion efficiency. The variable ratio of maximum to minimum in-cylinder volumes also improves the full load power output of the engine. Results of vehicle driving cycle simulations of a light duty gasoline vehicle with the advanced engine show dramatic improvements of fuel economy. The novel gasoline vehicle has close to diesel fuel energy usage and CO2 production while retaining the after treatment advantages of the stoichiometric operation with spark ignition. Coupled to advanced powertrains using mechanical kinetic energy recovery systems to recover the braking energy thus reducing the thermal energy supply in the following acceleration phase, these engines may offer even better than current hybrid electric vehicles fuel economy (comparison of compact size passenger cars with a turbo direct injection diesel and a mechanical kinetic energy recovery system and a gasoline hybrid electric vehicle published in a previous paper). The results of the paper are based on modelling techniques. These results need to be confirmed by experiments.