Abstract
The study aims to investigate feasibility of a single cylinder piston-type compressed air engine assisting to an internal combustion engine for idle start. The engine will be started as compressed air engine mode at beginning and it will later switch to internal combustion mode once the engine speed reaches to higher rpm. In this study, a theoretical analysis using thermodynamics and compressed air model has been carried out with MATLAB to understand the engine performance as well as fluid characteristics. A commercial available 100 c.c. single cylinder four-stoke internal combustion engine is modified to a 100 c.c. four-stroke air-powered engine to test the torque and power output. The experimental results have been compared with the data from theoretical analysis. A four-stroke compressed air engine has been modified with the inlet valve to operate with high pressure compressed air before the experiments. A buffer tank is connected to the four-stroke air-engine operation through the spark plug hole due to high cylinder pressure resulted from the isentropic compression. Different buffer tank volumes have been examined during the experiment for the torque and power output. The buffer tank with volume of 1.5 litters and compressed air pressure of 5 bar is used for the subsequent tests of idle-start. A four-stroke engine with four valves is also examined theoretically to find the feasibility of idle-start which can select one or two valves to connect with buffer region instead of using the spark plug hole. An exchangeable cam mechanism which can switch the two-stroke mode operation to/from four-stroke mode has also been studied, this mechanism can be used to start the engine as two–stroke compressed air engine then switch to four-stroke internal combustion mode. It can also be used to switch the four-stroke internal combustion mode back to two-stroke mode for regenerative braking and recycling the compressed air.