Research On Effects Of Fuel Injector Parameters Of Marine Low Speed Diesel Engine On Combustion

The combustion characteristics in marine low speed two-stroke diesel engine mainly depend on the mixture formation in cylinder. Spray characteristic is an important factor which affects the mixture formation. Further, parameters of the fuel injector directly influence the spray characteristic. Therefore, conducting the research of effects of fuel injector parameters on the combustion process of marine low speed two-stroke diesel engine is very meaningful. Besides experimental investigation, numerical simulation based on bench test is an effective method to study diesel engine combustion process.Take a marine low speed two stroke diesel engine as the research object, First, establishing the geometric model of cylinder,exhaust port and scavenging box, meshing grid respectivelyby software STAR-CD/ES-ICE, PRO-STAR, ICEM and STAR-CCM+ according to their different characteristics. Then assembling every part grid together, all of these create diesel engine work process simulation calculation model in cylinder; Then, gas exchange, spray and combustion process is simulated combined with initial and boundary conditions provided by 1D system simulation. And the calculation results are analyzed, combustion heat release rate curve of calculation is compared with the test results of reference model to verify the accuracy of the calculation model. Finally, study number of nozzle holes, nozzle hole angle, nozzle hole jet direction, nozzle hole arrangement and so on fuel injector parameters influencing on marine low speed diesel engine combustion process based on the simulation of the spray and combustion process by control variable method. The contour pictures of fuel, temperature and the concentration of NOX, and the change curves of heat release rate, mean pressure, mean temperature and NOX production in cylinder are analyzed emphatically.The results show that: flowcoefficientobtained bygas exchangesimulation is one of the important parameters of 1D system simulation, and delivery efficiency and scavenging efficiency provide reference for 1D; eachvariabledistributionincylinderandeachvariable changecurvesofcombustionprocessobtainedbyspray and combustionsimulationmakeafoundationofanalysisofcombustionincylinderof dieselengine; the number of nozzle holes of injector has a great influence on spray atomization, especially has a greater influence on the fuel evaporation mass during delay period, each additional nozzle hole, NOX production increases about 6%~9%; nozzle hole angle affects spray distribution, especially the distance between spray and cylinder head, nozzle hole angle each reduces 2.5°, NOXproduction reduces about 2.5%~5%, nozzle hole angle each increases 2.5°, NOXproduction reduces about 1.5%-3%, and it has most NOXproduction under nozzle hole angle of original machine; nozzle hole jet direction impacts spray distribution, especially the distance between spray and cylinder wall; the nozzle with two raw nozzle holes can extend scope of spray distribution, and avoid mutual interference between two sprays from adjacent nozzle holes.