One-dimension Evaporation Model Of Gel Fuel Droplet

With the development of technology, the demand for high-performance andimproved safety propellants for various rocket motor applications has been constantlyincreasing, and gels seem to be a promising answer to these requirements. Gels areliquids whose rheological properties have been altered by the addition of certaingelling agents and as a result their behavior resembles that of solids. Gels havesignificantly improved density impulse in comparison to liquids. Combustion is aparticularly complex process and the combustion phenomenon of gels with addedgelling agents is not clear, which seriously affecting the promotion of gels. Therefore,the establishment of the evaporation model of gel fuel droplet can provide atheoretical basis for people to research it.In this study, based on the special evaporation phenomenon, a evaporation modelof gel fuel droplet is established via Matlab software. The model describes theevaporation process into three different stages: gellant film formation, dropletswelling, droplet bursting. The model simulates gel droplet evaporation characteristicsin convection conditions and the impact of gelling agent concentration, environmentalstress, environmental temperature, convection velocity and initial temperature toevaporation process are analyzed. It concludes that in the stage of gellant filmformation, the evaporation of gel is similar with the evaporation of conventional fuels,which both comply with the D2law. In the whole evaporation process, bubbles areproduced inside the droplet and the bubbles can grow and burst resulting in theoscillation phenomena of the radius, evaporation flux and fuel vapor concentration ofgel droplet. Radius and evaporation flux is gradually reduced and droplet surfacetemperature and fuel vapor concentration first increase then decrease in the process.With the increase of gelling agent concentration, time of gellant film formationbecomes short and the lifetime of gel droplet is reduced. Increasing the ambie nttemperature will increase evaporation flux, fuel vapor concentration and dropletsurface temperature resulting in the decrease of gel droplet lifetime. The higherambient pressure is, the higer the equilibrium evaporation temperature will be in thegellant film formation stages. Then gellant film will be form hardly. Also highpressure will cause more bubbles produced inside the gel droplet. The oscillation frequency will decrease, too. Convection velocity has a greater impact on the lifetimeof film formation and gels, but has little effect on the surface vapor concentration.With the increase of gel droplet initial temperature, the lifetime of droplet will reduce.Of all the considering characteristics parameters, only gelling agent concentration hasgreat impact on the radius in the end of gellant film formation.