Simulation Of The Combustion Process In A Marine LNG Engine With REGR

As the global energy shortage and environmental pollution problem are more and more serious,looking for low cost,high efficiency clean substituted fuel and developing internal combustion engine technology have become strategic objectives for global marine power research institutions and manufacturers.Due to its abundant reserves and clean combustion,Natural gas has become the most popular alternative fuel.Because the existing natural gas engine hasn’t fully developed the advantages of natural gas in emissions,it still needs continuous improvement and optimization.It is a hot research direction to use the exhaust gas fuel recirculation technology on the natural gas engine.To study the EGR and simulation reformed gas on marine LNG engine,this paper sets a test bench for YC6MK200NL-C20,and tests the propulsive characteristics of the original machine.Then,a 1-D model in AVL Boost and 3-D model in AVL Fire were established,and the accuracy of the models was verified by comparison with the original experimental data.On the basis of the model,the simulations of the different EGR rates and different simulated reformed gas ratios are carried out.The results show that,at different operating conditions,the average pressure of the cylinder decreases with the increase of the EGR rate.The average temperature also decreases when the EGR rate increases.The whole combustion process is shifted while the combustion duration is increased.The indicated power and NO emission of the engine decrease,but the indicated fuel efficiency increases.Increasing the EGR rate can effectively reduce the NO emission.It also shows that the impact on the engine at low load is greater than that at high load.A appropriate EGR rate is determined based on the comprehensive consideration of dynamic economy and emission.Then the simulation of different reformed gas ratios is carried out.The combustion behavior is improved with the increase of the reformed gas ratio.The average pressure and temperature in the cylinder increase with the increase of mixing rate and the combustion duration is also shortened.As the ratio of reformed gas increases,the indicated power of the engine is increased,NO emission is increased,and the fuel consumption efficiency is basically unchanged.But when the mixing rate of the reformed gas is increased to a certain degree,the reduction of the fuel consumption efficiency is obvious.With the mixed reformed gas and EGR gas,the engine-out NO concentration can be reduced without sacrificing the power of the engine.When the engine operates at 75% load,the effect of reducing emissions is the weakest.NO emission is only 5.8% lower than that of the original machine.The effect of reducing emission which working at 25% load is the best,the reduction of NO emission is 16% compared with the original engine.