The Experimental Research On The Auto-ignition Characteristics Of Cylinder Lubricating Oil Of Marine Engine

The combustion of cylinder lubricating oil will cause the increase of particulate matter(PM)emissions.In addition,for premixed combustion gas engines,the auto-ignition of lubricating oil could lead to pre-ignition,a most threatening abnormal combustion.Therefore,it is very necessary to understand the ignition characteristics of cylinder lubricating oil droplets.An oil droplet suspending apparatus was applied to investigate the ignition and combustion characteristics of a kind of cylinder oil and its two major base oils — 150 BS(Bright Stock)base oil and 400 SN(Solvent Neutral)refined oil droplets.The results indicate that the auto-ignition process of cylinder oil droplets can be divided into three phases: the initial heating phase,evaporating phase,and auto-ignition phase.The droplet's temperature rose after it was sent into the high temperature environment.The droplet started evaporating when its surface temperature reached boiling point.For cylinder oil and 150 BS base oil,there were bubbles generated and their growth finally caused explosions of droplet in the process of evaporation.When the concentration of mixture of the oil vapor and ambient gas satisfied the ignition condition,the auto-ignition started.After a period of combustion,the whole droplet burnt out,and there were some coking residue on the quartz fiber.The ignition delay decreased with the increase of the ambient temperature under the condition of the same initial droplet diameter.The ignition delay increased with the increase of the initial droplet diameter under the condition of the same ambient temperature.There was a minimum ambient temperature for ignition.The droplets did not auto-ignite when the ambient temperature is lower than this temperature.There was a minimum droplet size for ignition in a certain ambient temperature.The droplets did not auto-ignite when their diameters were smaller than the minimum droplet size for ignition.For the same kind of oil droplets,the minimum droplet diameter of ignition limit has a fluctuating range.With the increase of ambient temperature,it showed a trend of decrease.However,when the temperature was gradually reduced to the minimum ignition temperature,fluctuating range increased gradually.