Study On Steady Combustion And Two-phase Flow Characteristics Of Nozzle In Nano-metal Fuel Engine

Nano metal fuel has many advantages,such as high combustion calorific value,high specific energy,high combustion rate,and no waste gas pollution of combustion products.In the future,it will replace the fossil non renewable energy such as coal,oil,natural gas,etc.,and widely used in underwater vehicles,surface ships,space vehicles,deep space detectors and other energy power systems,as well as deep-sea workstations,underwater drilling platforms,space workstation and power generation system in remote mountainous areas.It is a new fuel with great development prospect.In recent years,a bimetallic metal fuel engine technology has entered the field of scientific research.This technology enables the vehicle to not only sail at a high speed under water supercavitation,but also advance at a high speed over water supersonic,which will greatly promote the development of national aerospace and underwater weapon equipment technology in the future.In particular,the nano metal fuel engine(more than 80% metal content)has the advantages of high burning rate,high specific energy,high specific impulse,safety and controllability,which can realize the high-speed propulsion of the vehicle.In this paper,the two-phase flow characteristics of the nozzle of the water reaction nano aluminum based metal fuel engine and the oxygen reaction nano iron based metal fuel engine were studied,and the influence of particle shape,size,condensed phase content and other factors on the engine performance were discussed.In addition,the effects of non-spherical particles on the specific impulse loss and combustion stability of metal fuel engine were studied.Firstly,in this paper,the water-reaction nano-aluminum-based metal fuel engine and the oxygen-reaction nano-iron-based metal fuel engine were studied,respectively.The two-phase flow governing model and the particle combustion model of the nozzle with regard to the water-reaction nano-aluminum-based and oxygen-reaction nano-iron-based metal fuel engine were established,respectively.The combustion characteristics of nano-metal fuel particles and the two-phase flow peculiarities in nozzle were simulated.The variation trends of significant parameters such as fluid density,pressure,Reynolds number,Mach number,gas velocity,gas temperature,particle velocity,particle temperature,particle diameter,particle mass transfer rate,particle density distribution,particle linear burning rate,particle mass release rate,particle velocity lag,temperature lag and burning time were studied.The flow characteristics of the particles in the nozzle of the nano-metal fuel engine and the effects of the particle size and the condensed phase content on the two-phase flow loss were discussed.The results show that the average specific impulse of water-reaction nano-aluminum-based metal fuel engine can reach 4900 N·s/kg when the condensed phase content is about 36% and the particle size is about 0.40-0.70 ?m;when the condensed phase content is about 30% and the particle size is about 0.4-1.0 ?m,the specific impulse of oxygen reaction nano-iron-based metal fuel engine can reach more than 3100 N·s/kg.Furthermore,the two-phase flow characteristics of metal fuel engine nozzle considering the factors of non-spherical particles such as ellipsoid and cube were studied.Non-spherical particle drag coefficient,particle Nusselt number model and two-phase flow governing model of metal fuel engine nozzle were established.The effects of three kinds of particle models,ellipsoidal,cubic and spherical,on the two-phase flow loss in the nozzle were simulated at different angles of attack.The results show that the ellipsoidal model can fit the experimental results better.Finally,the combustion models of prolate and oblate spheroid particles were established,and the combustion performance of different particle shapes and sizes under certain conditions was analyzed.The results show that the particle shape,size and Reynolds number have a significant effect on the combustion characteristics of the nano aluminum based propellant.The research method in this paper can provide theoretical basis and reference for the technical optimization design of dual medium vehicle engine.