Simulation And Performance Optimization Of A Natural Gas Engine Working Process

With the rapid development of shipbuilding industry and the increasingly more serious emissions regulations, countries all around the world are actively looking for ideal alternative fuels. Natural gas has those performances: high calorific value and rich reservation and low emissions pollution. So natural gas is an idea alternative fuel. It is very important to choose the reasonable control and structural parameters to increase the power and economy performance of natural gas engine. Combining theoretical analysis and experimental study and simulation, this paper did a research to optimize natural gas engine.The natural gas engine was investigated in experimental platform by experiment. The gas engine was tested several performance, including torque, power, gas consumption rate, cylinder pressure and so on. Compare these performance data and calculation results. The results showed that the power performance of natural gas engine is lower than the diesel engine, its gas consumption and exhaust temperature turn out to be higher than the diesel one.The author established an eight-cylinder gas engine model by GT-Power. Based on physical and chemical properties of natural gas, the author studied the influence of different compression ratio, ignition advance angle, valve timing and intake system structure on engine performance.Simulated the model under the different loads, which showed the effects of compression ratio on power, economy and cylinder pressure of engine. Analyzed how the different comparison ratio affected the engine power, torques, gas consumption rate, cylinder pressure and maximum rate of pressure rise. The results show that the compression ratio is 12.5, engine torque and power would be enhanced. Simulated the model for various ignition advance angles to analysis how the power economy and cylinder pressure of engine change under the different loads. The results show that the engine power has improved and gas consumption rate has declined when ignition advance angle is 18~20°CA.Simulated the model speeds for detecting the influence of main intake pipe and intake manifold pipe on engine performance under the different load. This paper analyzed the influence of different intake pipe on variation of combustion pressure, torque and gas consumption with structure of intake pipe. It is shown that a good structure of intake pipe impacts could increase volumetric efficiency of engine.Simulated the model under three certain type speeds to see how the different valve timings affect engine performance. This paper analyzed that the effects of IVC on volumetric efficiency, and the effects of EVO on pumping loss. The results show that reducing properly IVC can improve volumetric efficiency; reducing properly EVO can reduce pumping loss. It could prepare for the cleaning of waste gas and the entry of fresh air mixture. So the power and economy of engine could be improved.