Improving the NOx-BSFC Trade Off of a Turbocharged Large Diesel Engine Using Performance Simulation

The purpose of this study is to determine the optimum intake valve closing time of a large diesel engine having lower fuel consumption and lower NOx emission. The performance simulation has been conducted for this purpose, and a phenomenological combustion model is verified by experimental data of heat release rate and NOx emission in order to enhance the prediction quality of the performance simulation. The results of performance simulation are compared with measured data to confirm the modeling method and results. The fuel injection system simulation has been also performed to get fuel injection rate, and the results is also verified by experimental data of fuel injection pump pressure and injected fuel mass. The performance simulation investigate the application of Miller cycle to a large diesel engine, and so, the intake valve closing time is determined at the condition of reducing NOx emission and fuel consumption at the same time. As that result, Miller cycle has a feature that the maximum reduction of NOx emission is 15.7% while the improvement of specific fuel oil consumption is 1.7g/kWh.