Experimental studies of the air hybrid engine charging operation

Over the last few years, theoretical and modelling studies have been carried out on the feasibility and potential of novel mild air hybrid engine concepts based on production components. These mild air hybrid concepts are able to convert vehicle brake energy into pneumatic energy in the form of compressed air stored in the air tank. The compressed air can then be used to crank-start the engine by either injecting and expanding in the cylinder or driving a production air starter. Thus, the regenerative stop-start operation can be readily realised for improved fuel economy. In order to demonstrate air hybrid engine charging operation experimentally and validate the theoretical analysis, a single-cylinder engine has been adapted to operate in the compressor mode with the novel one-way intake system. Two air intake designs were implemented and tested so that their ability to capture compressed air could be analysed. In particular, it is shown that the compressor mode can be accomplished effectively through a simple cam profile switching device which has been used in production engines. Furthermore, the experimental and analytical results show a good agreement which gives high confidence to the theoretical analyses carried out on different mild air hybrid engine concepts examined.