Experimental Study On Ignition And Flame Combustion Characteristics Of Engine Oil On Hot Surfaces

Ignition on hot surfaces of automobiles is a main cause of automobile fires.The most noteworthy hot surfaces are the the engine and the exhaust system,which accumulate a amount of heat energy during the work of the automobile,which is very easy to ignite the dripping fuel.However,the current experimental data of igniting flammable liquids on hot surfaces are relatively limited,the theory of hot surface ignition is not perfect,and basic research is rarely done to explain the mechanism of hot surface ignition.Therefore,carrying out experimental research on the ignition and flame spread characteristics of engine oil is important for revealing the mechanism of hot surface ignition.moreover,It can prevent ignition on hot surfaces of motor vehicles and ensure the safety of automotive industry systems.To this end,under different experimental conditions,we study the ignition and flame spread characteristics of engine oil with hot surface ignition.The research parameters include:ignition delay time,minimum ignition temperature of hot surface,ignition probability of hot surface,flame spread speed,flame height and characteristic flame temperature.The main conclusions are as follows:As the hot surface temperature enhances,the ignition delay time generally shows a downward trend.450℃ is the critical point,and the ignition delay time decreases slowly;the oil volume is in the range of 0.1-0.4ml,and the ignition delay time also increases with the increase in oil volume;the ignition delay time is closely related to the droplet diameter.The larger the droplet diameter,the longer the ignition delay time.The general trend is that the ignition delay time is similar at 0.4-0.5 ml and fluctuates within 0.68-1.3 s.When the amount of oil in a single injection in the experiment was increased from 0.1 ml to 0.4 ml,the minimum ignition temperature of the hot surface dropped from 370℃ to 310℃,and when the amount of oil rose to 0.5 ml,the minimum ignition temperature was 312℃.In addition,the hot surface ignition in the temperature range is a probabilistic event,and the probabilistic behavior occurs in the temperature difference range of 42-50℃,and the result presents an S-shaped distribution.Finally,it was found that the height of the ignition core at the beginning of the flame spread was between 3.13-5.978 cm.As the temperature of the hot surface increases,the flame spread rate first increases and then stabilizes at 480℃.At the same temperature,the flame propagation reaches the maximum when the oil volume is 0.2 ml.The average temperature of the blue flame is in the range of 732.75-1161.5℃,and the existence time of the blue flame has no obvious correlation with the temperature,both are between 0.025 and 0.051 s.The average temperature of the hot flame is in the range of 986.9-1540℃.The maximum flame temperature and the maximum heat flame height are positively correlated with the amount of oil,and the maximum heat flame height range is within 7.03-8.87 cm.