Numerical Simulation Investigation Of Ship Diesel's Combustion And Emission

With the energy crisis and environmental problems having become increasingly serious, people's requirements of the ship diesel economy, emissions performance is increasing. Since the International Maritime Organization (IMO) developed more stringent emission standards, reducing diesel engine nitrogen oxide (NOx) and particulate emissions becomes a pressing problem. Diesel combustion process is the most fundamental factor to determine the combustion and emission performance. Computer science and technology and the rapid development of numerical simulation of the combustion process have become an important means to study the combustion process. The CFD (Computational Fluid Dynamic) simulation softwares have the advantagement of low cost, fast, and they can provide some test data which is not available from the experimentation.This paper uses FIRE as a research tool. ESE module coming from FIRE is applicated to establish the combustion chamber geometric model and moving mesh of TBD234V12 diesel. The calculating initial parameters are setted. The diesel engine combustion simulation platform is established and validated by experimental data.This paper calculates and analyzes combustion emissions of TBD234V12 diesel as the ship auxiliary diesel power when the load changes. The results show that as the load increased, the combustion ignition delay was decreased,and cylinder temperature, pressure, heat release rate, Soot and NO emissions are increased. This paper calculates and analyzes the combustion and emissions of TBD234V12 sequential turbocharging diesel engine as propulsion system of ship.The combustion and emissions performance of before and after switching point are investigated. The results show that, the 1TC condition is powerful than the 2TC conditions. 1TC conditions of temperature and heat release rate is less than 2TC conditions. The NO, Soot and CO2 emissions performance of the 1TC condition are better than the 2TC conditions.Under different load,the change of inlet pressure on diesel engine combustion and emissions performance are calculated and analysised. The results showed that with the increase of inlet pressure, the ignition delay is shortened gradually. At low load,the inlet pressure impacts on the ignition delay greatly.At high load,the inlet pressure impacting on the ignition delay is less affected.In 13% load, with the increasing of inlet pressure, NO, Soot reduced.At 89% load, with the increasing of inlet pressure, NO increased and than decreased, Soot decreased and then increased. The diesel's combustion emissions performance of inlet pressure at different intake valve shutting down time is investigate. The results show that the intake valve shutting down early has little effect on combustion heat release rate and is in advantage of reducing the cylinder temperature in the high inlet pressure.The intake valve shutting down early is more favorable reducing the NO and CO2 formation.The performance of diesel engine combustion and emissions and different injection rate and injection timing are investigated. The results showed that the square wave injection rate lead the higher maximum combustion temperature and more NO emissions are, but lower Soot emissions.With the increase of fuel injection timing, ignition delay is extended.The maximum combustion pressure and maximum temperature are rised.The combustion heat release rate at the beginning of combustion and the rate of pressure rise is relatively high. Delayeing injection timing appropriately can reduce the NO emissions.At -10°CA ATDC fuel injection timing, the performance of combustion emissions of the diesel engine is better.