Simulation On Performance Of Marine Low-pressure Dual-fuel Engine

With the development of the economic globalization,exhaust emissions from marine transport have a significant impact on global air quality.In order to effectively control the emission of marine exhaust gases,Annex VI "Regulations for the prevention of Air Pollution from ships" of the "MARPOL73/78" issued by the International Maritime Organization(IMO),and clearly stipulates the emission limits of pollutants in the exhaust of ships.The face of increasingly stringent emission regulations,dual-fuel engine technology with the good emission has become an important direction for the development of marine engines.In this paper,study about a two-stroke marine low-speed dual-fuel engine,and use the numerical simulation method.Analysis of the low-pressure dual-fuel engine working process detailed and based on the study of natural gas injection conditions,pre-combustion chamber structure,Analysis the impact of engine performance and emissions.The study laid the foundation for the optimization of low pressure dual fuel engine.First of all,a three-dimensional simulation model of low-pressure dual-fuel engine is established by using CFD simulation software.And grid,boundary division and calculation parameter configuration are carried out.Combined with the each operation condition experimental data under certain conditions calibration calculation model calibration.The relevant boundary conditions and initial conditions involved in the model are provided by the established one-dimensional calculation model.The calibrated three-dimensional model is used to analyze engine scavenging,natural gas injection and pilot fuel combustion.The influence of each operation condition and different working process on the physical field in the cylinder of the engine was studied.According to the results,the variation rules of pressure,temperature and pollutant generation in the cylinder were obtained.Secondly,the effects of natural gas injection angle,injection valve position,injection valve radius,natural gas intake time and natural gas intake duration on engine performance and emissions were studied by changing the natural gas injection valve structure and natural gas intake conditions.Analyze from the influence of convection field,combustion and emission respectively.The effects of various parameters on the velocity field,the uniformity of the mixed gas,the pressure in the cylinder,the temperature,the heat release rate and the changes of the pollutants generation were investigated in detail.Finally,the changes of pre-combustion chamber structure(presence of pre-combustion chamber structure,pre-combustion chamber passage diameter,pre-combustion chamber passage angle)and changes of pilot fuel injection conditions(fuel injection orifice,pilot fuel injection timing,fuel injection Duration)on engine performance and emissions.Considering the influence of flame propagation,combustion and emission,the variation of temperature field distribution,velocity field distribution,pressure and temperature in cylinder and pre-combustion chamber,heat release rate and pollutant generation were analyzed.The research results obtained in this paper can provide references for the design and optimization of marine low-pressure dual-fuel engines and lay a foundation for further improving engine performance and reducing emissions.