Abstract
This study aims to investigate the intake and exhaust system designed for a piston-type compressed air engine and examine the air engine application on motor vehicle. A simulation approach which uses thermodynamic and compressed gas models of single cylinder piston-type compressed air engine has been performed with MATLAB. The simulation is to evaluate the power performance and fluid characteristics of the compressed air engine at different valves timings, valves diameter sizes, and the cam lift effects. A conventional 100 cc four-stroke internal combustion engine (IC engine) was modified to two-stroke compressed air engine to examine the power output and fluid properties at various intake pressures and rotation speeds. The torque output, air flow rate and cylinder pressure have been recorded which can help to understand the fluid characteristics of the compressed air engine during operation. The acquired experimental results have been compared with simulation and show that the conventional engine design uses cam mechanism to control intake and exhaust valves and has the consequence of gradually valve opening and closing. Therefore, this restricts the air flowing in and out of cylinder at high rotation speeds and high supplying air pressure. In order to solve this problem, a rotatable intake-exhaust system was designed and it has the advantages of fast valve opening and closing. The new system can sustain at high air pressure up to 13 bar and the cylinder pressure during operation can raise faster than the one using the conventional cam mechanism. The air engine installed with the rotatable intake-exhaust system can provide power output of 2.15 kW and 15.97 N-m at 13 bar air pressure. The study of split-cycle concept of the compressed air engines has also been carried out. Split-cycle air engine is designed to recycle the exhaust compressed air by adding another cylinder to the system, and it can be improved the efficiency of air engine operating at low speed. Finally, the compressed air engine was installed in a small size motorcycle for vehicle application which demonstrates the concept of green energy vehicle with zero emission. The motorcycle installed with the compressed air engine can operate at maximum speed around 38.2 km/hr and range of 5 km.