Investigation On The Liquid Phase Ignition And Mixing Mechanism Of Hypergolic Ionic Liquids Propellants

The hypergolic ignition liquid rocket engine does not require an ignition system and is widely used in propulsion systems for satellites,missiles and other spacecraft.Conventional hypergolic ignition liquid rocket engines are fueled by MMH,UDMH and other hydrazine fuels,which have the characteristics of high toxicity and storage security risk.Therefore,in recent years,the space powers have launched the plans of green alternatives for hydrazine fuels.In this paper,the liquid phase flow in the light-off course and self-ignition mechanism,propellant combination optimization and numerical simulation of the collision jet in the liquid phase mixing and start-up process of the new type of hypergolic ignition energetic ionic liquids propellants are investigated.The main academic innovations are as follows: 1)New types of ignition phenomena of spontaneous liquid propellants are discovered.The self-ignition experimental platform of ionic liquids and oxidants is designed and set up.The microscopic images of the liquid surface mixing and the flame profile of ignition process after the collision of the ionic liquid droplets with the oxidant at different speeds are realized.The results show that there are three self-ignition modes after the collision of different energetic ionic liquids with the oxidant,that is,after the collision,(a)a micro-explosion ignition mode that generates a large number of splashed secondary droplets,and(b)the gas layer ignition mode with intermediate products forming a Leidenfrost layer,and(c)the merged ignition mode after the coalescence of droplet and liquid pool.Among them,the ultra-fast Coulomb explosion ignition phenomenon observed in some(c)type ignition modes has not been reported in the field of international spontaneous combustion propellant research;2)Two potential green energetic ionic liquids are preferred.Ignition performance parameters of a variety of different energetic ionic liquids,such as Coulomb explosion delay time,explosion delay time,ignition delay time,and flame area,are quantitatively obtained.The dependence of the Coulomb explosion delay time on the length of the ionic liquid cation side chain and the influence of cation unsaturation on the ignition delay time are found.The mechanism of the ionic liquid breaking through the Rayleigh instability limit and achieving the Coulomb explosion is clarified.The self-ignition of the ionic liquid-oxidant combinations and the presence or absence of solid product performance are evaluated,and two of the best performing propellant combinations are selected,which are expected to be used to replace the traditional highly toxic hydrazine fuel;3)The formation process of liquid film,liquid ligaments and droplets in the mixing and breaking process of symmetric double jets collision are explored.Simulation calculation of double-jets collision is conducted by Fluent,where the VOF-coupled Level Set method is used to calculate the transient process within 2ms.The formation of liquid film,liquid ligaments and broken droplets are observed.It is found that the jet atomization effect is better when the collision angle is 80°,which provides a reference for the subsequent experimental and simulation studies on the collision of self-igniting ionic liquid propellant jets with asymmetric physical properties.