Research on a pneumatic hybrid engine with regenerative braking and compressed air assisted cranking
With the aim of improving the energy efficiency of conventional vehicles, this paper proposes a pneumatic hybrid engine concept, which features regenerative braking and compressed air assisted cranking functions. In the regenerative braking mode, the engine works as a two stroke compressor and converts the kinematic energy of the vehicle into compressed air. In the two stroke air motor mode, a throttle valve in the intake manifold is used to block the ambient air, and an electropneumatic solenoid valve is employed to control the compressed air injection. The compressor mode is modelled on the basis of thermodynamics and gas dynamics theories and is improved according to the bench test results of a single cylinder engine converted from a two cylinder diesel engine. Transient engine cranking tests are also conducted and are discussed. Urban driving cycle simulation results show that the fuel consumption of a light duty vehicle with a pneumatic hybrid system can be reduced by 8%