Performance Simulation And Optimization Of Marine Diesel Engine Based On Hydrogenation Combustion

Facing with the two major problems of petroleum resource consumption and environmental pollution,it is urgent to improve thermal efficiency of marine diesel engine and reduce pollutant emissions.In order to achieve the goal of sustainable development,China has launched the"dual carbon"strategy,and hydrogen energy is also applied to diesel engines.In this paper,the combustion chamber model of a four-stroke marine diesel engine was constructed using the commercial software AVL-Fire,and the effects of intake air hydrogenation,intake air humidification and EGR on in-cylinder combustion and emissions of diesel engine were investigated by reforming the intake air components using numerical simulation methods.The technology solutions that can simultaneously reduce NO_x and soot emissions with non-reduce the thermal efficiency of diesel engine were being explored.Intake air hydrogenation used the principle of energy substitution to ensure that the total low calorific value of fuel entering cylinder is constant.The results of the studies show that hydrogen addition results in faster heat release rate and shorter ignition delay.The in-cylinder temperature and pressure increase with the increase of hydrogen energy ratio.The end time of diesel injection is advanced,which makes CA50move forward.The improvement of combustion constant volume can enhance the work ability of in-cylinder gas,and the indicated work increases accordingly.The shorter diesel injection duration also improves in-cylinder equivalence ratio distribution and the maximum generation and final emission of soot are reduced.CO₂ emission is reduced due to less diesel injection.Intake air humidification and EGR reduce the in-cylinder oxygen concentration and temperature through dilution and thermal effects,which in turn the combustion and emission of diesel engine.When water-fuel ratio is 150%or EGR rate is 19.8%,NO_xemission of diesel engine is reduced by 78.2%,which is lower than the requirements of IMO Tier III emission regulations.The differences in the effects of intake air humidification and EGR on combustion and emissions were compared for the same NO_x emissions.Compared with intake air humidification,EGR has lower in-cylinder oxygen concentration and slower diesel combustion speed.CA50 is delayed and indicated work is reduced.Soot and CO emissions increased with the increase of water-fuel ratio and EGR rate.The numerical simulation results show that intake air hydrogenation coupled with intake air humidification and EGR can achieve the goal of reducing NO_x and soot emissions with non-reducing the thermal efficiency of diesel engine.Intake air humidification and EGR can significantly reduce NO_x emissions,but soot emission increases due to combustion deterioration.Intake air hydrogenation can not only increase in-cylinder temperature and accelerate oxidation rate of soot,but also reduce diesel injection quality and reduce the generation of soot from the root.After hydrogenation,the in-cylinder pressure of the diesel engine increases,and the forward movement of CA50 can increase indicated work.On the premise of reducing soot emission and increasing indicated work,the NO_x emissions of 28 calculation schemes are lower than prototype engine.There are 18 calculation schemes for intake air hydrogenation coupled with intake air humidification and 10 for intake air hydrogenation coupled with EGR.If NO_x emissions are lower than the requirements of IMO Tier III regulations,there are 8 calculation schemes can meet the requirements.There are 7 calculation schemes for intake air hydrogenation coupled with intake air humidification,and only 1 scheme for intake air hydrogenation coupled with EGR.Intake air hydrogenation coupled with intake air humidification is better than intake air hydrogenation coupled with EGR in reducing pollutant emission and improving thermal efficiency of diesel engine.