VAPORIZATION OF HYDROCARBON FUEL DROPLET ' ON A HEATED FLAT PLATE

Abstract

A new vaporization model for hydrocarbon fuel droplets under conditions (intake valve surface temperature, pressure and temperature distribution in the intake system) relevant to spark ignition engines fitted with multipoint fuel injection system has been developed. The model is based on experimental observations by other investigators. Equations for vaporization lifetime (the time required from droplet contact with heated surface to evaporate and disappearance) of single droplet and spray of droplets were obtained in terms of initial droplet size, composition and surface temperature. The motive for this work was to get a better insight in to the phenomenon of evaporation of fuel on the surface of intake valves of Sl engines. First, the representative diameters of the droplets in a spray were randomly generated and the dynamics (heat flux and drop shape after impingement) of the droplets immediately after arrival was "studied thoroughly and subsequent evaporation was then modeled. The software developed in .turbo C++, was used for numerical solution and representative spray droplet diameters random generation. Finally, the results were compared with the experimental results reported by other investigators and a good agreement was obtained. From the result we observed that reducing droplet diameter is an extremely effective way to shorten evaporation lifetime of a droplet in the temperature range up to 40CC above the boiling points of all the fuels investigated. The result was also applied to the calculation of mixture formation in the intake system of a gasoline engine with specifications as given in Table 5.4 and an acceptable agreement was obtained.