Design And Analysis Of New Pneumatic Engine’s Test Prototype

The absence of petroleum resources and the pollution of environment, theexistence and development of internal combustion engines are endangered. So we haveto look for available substitute for the energy of internal combustion engines. Pneumaticengine is a power plant which can transform high-pressure air energy into mechanicalenergy. Compared with the internal-combustion engine, the main advantages ofPneumatic engine is zero-pollution and zero oil consumption, it can be widely used andwill have extensive business prospects. At present, the domestic and foreign Pneumaticengine mostly uses internal-combustion engine institutions, some engines adoptsimpeller which can be swayed by high-pressure air. The paper designs a new Pneumaticengine-a sealed chamber is added on the basis of automatic exhaust pneumatic engine.Which can effectively improve the pressure difference of the of the exhaust valve’supper and lower surfaces, in order to close the exhaust valve using the high-pressure gasin the sealed chamber. Meanwhile, a test system is designed for the new Pneumaticengine.First, the working principle of new Pneumatic engine is introduced. Themodification scheme is determined, according to the work principle and the originalmachine structure of NGH GT35R, that is single-cylinder two-stroke engine. And themodified parts are also designed and calculated. Then, the geometric models of withsealed chamber and without sealed chamber are established, and the working process ofthem are simulated using renormalization group (RNG) k-turbulence model based onFluent platform in CFD software. Simulation represents the change of in-cylinder flowfield with the changes in the structure, e.g., cylinder pressure, exhaust flow. Thecalculation results show that, the structure with sealed chamber improves the pressuredifference of the exhaust valve’s upper and lower surfaces, which comes from the highpressure gas in the process of inlet. It well realizes the function ofusing high-pressure gas pressure to automatically close the exhaust valve. Meanwhile, itreduces the gas loss due to gas exhaust out of cylinder during the inlet process. Finally,under the FLOW-3D software, using FAVOR technology to process the grid influid-solid boundaries, to simulate the new pneumatic engine in the condition of cylinder under isothermal expansion. Results show that the cylinder pressure in theintake process is close to the inlet pressure, the flow rate at the beginning is relativelyfast. The distribution of cylinder pressure is uniform during the expansion process.Because of the unchanged volume expansion rate, which is lead by the fixed valve train,the cylinder pressure at the final expansion is slightly higher than the pressure of theexternal environment. The negative pressure difference caused by insufficiencyexpasion is generated in the exhaust process, and then the reverse torque is delivered tothe crank and connecting rod mechanism, so the engine performance is reduced. Underthe different inlet pressure, effective power output of engine and energy utilization rateof each are not identical, the inlet pressure is greater, the engine’s effective power islarger, but its energy utilization rate will be relatively reduced.