Simulation Performance Of Marine Low Speed EGR Diesel Engine With Two Turbocharger With Different Size

Marine low-speed diesel engines have been widely used as the main power plant in ocean transport vessels.Nitrogen oxide contained in their emission could severely harm the atmospheric environment and human health.According to regulations in Annex VI of"International Convention for the Prevention of Pollution from Ships" formulated by International Maritime Organization(IMO),since January 1st of 2016,ships navigating in the emission control area shall be subject to Tier III rules,that is,nitrogen oxide emission of low-speed diesel engines shall be controlled below 3.4g/kWh.Exhaust gas recirculation technology is one of the effective technical measures that can greatly reduce nitrogen oxide emission of marine diesel engines and thus satisfy Tier III rules.Taking 7G80ME-C9.2 diesel engines from MAN Corporation as the prototype,the article established the simulation model of the diesel engine by applying the GT-POWER software,and conducted matching verification.Based on this model,by referring to exhaust gas recirculation diesel engine matching mode of 6S80ME-C9.2 from MAN Corporation,the article established a high-pressure EGR system,selected one large and one small turbocharger for re-matching,and created the simulation model for 7G80ME-C9.2 EGR diesel engine.The article also analyzed and studied the operational strategies of diesel engines in different areas under diversified working conditions,and respectively calculated 25%,50%,75%and 100%working conditions.According to the results,when functioning under Tier II mode,performances and emission indices of EGR diesel engines using one large and one small turbocharger were close to those of 7G80ME-C9.2 prototype;when functioning under Tier III mode,NOx emission was significantly reduced,which satisfies the requirements of regulations,but the fuel consumption increased slightly.While using the EGR system to satisfy requirements of NOx emission regulations,particulate matters and SOx generated in the combustion process must be handled well in order to prevent recirculating exhaust gas from entering into the cylinder,corroding and wearing the scavenge system,combustion chamber assemblies,cylinder casing,piston ring,piston,cylinder head and piston rod,exhaust valve as well as other core components of the machine,and ensure long-term reliable operation of the machine.Therefore,the article carried out studies on wet washing scheme of the EGR system by applying the sodium alkali method,calculating and analyzing its operating economy,with an aim at offering technical data for practical applications.The simulation research of the article can be used as references for control strategy research on NOx emission of marine low-speed two-stroke diesel engines that apply high-pressure exhaust gas recirculation of one large and one small turbocharger;it has certain engineering application values.