The Research On Cold Startability Of Marine Diesel Engine

A huge of challenges could arise in the cold starting period of marine diesel engines,such as lower starting speed,higher friction resistance and gas leakage,more heat loss etc,which seriously influence the common use of marine diesel engines.It is of great significance to grasp and properly use the influence law that how different factors influence the diesel engines' cold starting performance.This paper was researched on the cold starting period of a marine diesel engine,and was carried out a series of simulation on some potential influences,including starting speed,compression ratio,inlet temperature,valve timing and injection parameters etc.On this basis,according to the requirement of the target engine when the environment temperature was-28?,the concrete starting strategies was put forward in this paper.First of all,through constructing the 1D and 3D simulation model,the factors and combustion process that could influence the diesel engine's cold starting performance were analyzed in this paper,from which could conclude that: in low air temperature conditions,the gas leakage rate of the engine was mainly influenced by starting speed and decreased with the increasing of starting speed.The cylinder temperature at the end of compression increased 1.2~1.5? when inlet temperature increased 1?;in contrast,the temperature at the end of compression increased about 19? when compression ratio increased 1 unit.In addition,the diesel engine's temperature at the end of compression could be efficiently controlled by appropriate adjustment on IVO and EVC timing conditions to decrease the overlap and control the back flow mass of exhaust gas.What's more,in the initial period of cold starting,the premixed combustion near the wall commenced when the temperature in cylinders comes to 700 K,and cold start performance of the engine could be improved by appropriately increasing fuel injection and delaying injection time.Then,by applying the influence law and effects that could change the engine's cold startability,the two-stage cooler system solution was put forward in this paper.According to the results of the engine's experiment,the accuracy of the CFD model and the heat transfer multiplier of the two coolers were confirmed,which made the simulation results are same as the experiment.Finally,according to the calibrated simulation model and influence law of cold starting performance,the concrete starting strategies were put forward when environment temperature is-28?.By contrast to the different arrangement schemes of the two coolers,it offerd a best solution to the engine's-28? starting in this paper,namely,the low-temperature cooler was arranged on the high-temperature cooler,water temperature in the two coolers was heated to 5? and 36.3?.