Study On Wall Wetting And Evaporation Process Of Different Fuels Based On Wall Wettability

As the main power source of automobile,the optimization and control of internal combustion engine have been paid more and more attention.Of the many factors limiting the development of the internal combustion engine,one of the most important is the "wet wall" phenomenon.Restricted by combustion mode in the confined space of internal combustion engine,spray wet wall is inevitable.At the same time,it will have a negative impact on the emission,economy and service life of the internal combustion engine.Previously,few researchers have studied the wet wall phenomenon under different boundary conditions based on the infiltration of the combustor wall.In this paper,the spray wet-wall phenomenon of internal combustion engine is studied based on the material surface infiltration.It mainly built three test platforms,namely material surface processing platform,droplet wall collision test platform and spray wall collision test platform.In addition,the image information quantization processing program is designed based on MATLAB software,and then the impact parameters such as spreading factor,rebound factor,spreading radius and suction height are analyzed quantitatively.Based on the above test platform,the infiltration of different fuels on different material surfaces was improved.Based on the previous work,the following two aspects are mainly studied.In this paper,the effects of wall temperature and material surface wettability on the shape development,spreading factor and rebound factor of fuel droplets after they hit the wall are studied.The experimental results of wall temperature show that the droplet experiences the process of spreading,shrinking and spreading again after hitting the wall.As the wall temperature increases,the heat transfer modes of fuel droplets on the wall experience natural convection,nuclear boiling,over boiling and membrane boiling in sequence.With the change of heat transfer mode between fuel droplet and wall surface,the spreading factor shows a decreasing trend,and the rebound factor increases gradually,and the rebound rate also increases gradually.At different temperatures,the bounce factor and bounce rate of n-butanol droplet are basically higher than that of diesel droplet.The experimental results show that the spreading factor increases with the increase of the surface roughness and the rebound factor decreases before the droplet reaches the boiling state.The spreading factor of the fuel after hydrophobic treatment is obviously smaller than that of the material surface without hydrophobic treatment.The spreading factor of n-butanol on all test surfaces is greater than that of diesel,but the rebounding factor is smaller.After entering the boiling state,the influence of wall temperature on the wet wall of fuel droplets is much greater than that of wall infiltration characteristic parameters.In the aspect of spray wall collision,the effects of material surface infiltration,wall temperature and ambient pressure on the morphological development process,spreading radius,entrainment height and mixture concentration in the near-wall area were studied.The results show that the spreading radius and entrainment height of diesel fuel spray increase gradually under different wall temperatures.The spreading radius and entrainment height of n-butanol spray increased first and then decreased after hitting the wall.At all test temperatures,the entrainment height of diesel oil was significantly higher than that of n-butanol.The spreading radius and entrainment height of fuel spray after hitting the wall decrease with the increase of ambient pressure.Under the condition of different wall infiltration,the spreading radius of the two fuels decreases with the increase of the surface roughness of the materials.The test results of the mixture concentration in the near-wall area show that the ambient pressure has an inhibitory effect on the formation of the mixture in the near-wall area.At different temperatures,different fuels have different degrees of sensitivity to wall infiltration.With the increase of wall temperature,the sensitivity of fuel to wall infiltration gradually decreases.