Abstract
The study aims to investigate the feasibility of integrating piston compressed air engines in four-stroke internal combustion engine for idle start and regenerative braking application. The simulation model is developed to analyze the engine cylinder pressure and recycle pressure in the storage tank during operations using thermodynamic and gas dynamic models. The simulation model is developed using commercially available software (MATLAB). From the simulation results, a buffer tank is necessary in the four-stroke operation due to the increased pressure in the cylinder and resistance of piston movement during compression process. A 100 cc IC engine has been modified for compressed air operation to examine the recycle pressure and fluid properties at various cranking torques and different buffer tank volumes during regenerative braking. The results show that the compressed air engine operated at two-stroke cycle has better performance than the four-stroke one, which has higher recycle pressure and better efficiency . This study also tested the idle start operation with four-stroke design, but it didn’t succeed with current valve timing. It has been identified that two-stroke operation has better performance not only in regenerative braking but also high possibility for the application of idle start. However, a specified mechanism is needed for transferring the four-stroke operation to two-stroke. During two-stroke regenerative braking, the highest recycle pressure is 6.5 bar which is higher than the minimum pressure for idle start ( ~4 bar). The application of compressed air engine for idle start and regenerative braking is feasible if it is operated in two-stroke mode.