Research On Thermal Oxidation And Pressurization Behavior Of Al-Mo Alloy Fuel

Metal fuel is an important part of solid propulsion power system,and its combustion performance directly affects the specific impulse of solid propellant.To solve the problem of serious two-phase flow loss caused by combustion agglomeration,this paper proposes the concept of combustion-pressurization alloy fuel for the first time:Compared with the elemental aluminum powder,the low-boiling product produced by combustion exists by gas without reducing the volume combustion enthalpy,causing additional pressurization in the combustion chamber.Simultaneously,the high melting point molybdenum element and aluminum element are alloyed for the first time to prepare Al-Mo alloy fuel with pressurization effect.In this paper,vacuum levitation melting and ultra-high temperature gas atomization(nozzle temperature is higher than 1600?)were used to prepare series Al-Mo alloy fuels successfully.The combustion performance of series of Al-Mo alloy fuels was comprehensively evaluated,and the phase composition,morphology,and thermal oxidation behavior of Al-Mo alloy fuels were characterized by XRD,SEM,and TG-DTA respectively.Optimal composition ratio and internal organizational structure of alloy fuel had been obtained.The results showed that Al-Mo alloy fuels burned completely at oxygen pressure of 3.0 MPa,the volume combustion enthalpy of Al-20Mo alloy fuel is the largest,as high as 81.064 k J/cm³.A large amount of rice-like Al₁₂Mo phase and Al phase are alternately distributed on the surface and inside of Al-20Mo alloy particle.The preferential oxidation of the alloy phase and the volatilization of gaseous Mo O₃ provide oxygen channels for the oxidation of the Al phase inside the particle,and further promote the complete oxidation of the particle.The actual weight gain of Al-20Mo alloy fuel is 49%,and the oxidation completeness is as high as 95.9%.The Al-20Mo alloy fuel with the best composition ratio was mechanically alloyed with graphite fluoride(PMF)to prepare an Al-Mo-PMF composite fuel.It is found that the doping of 5%PMF can promote the complete combustion of the composite fuel,while excessive PMF significantly reduces the energy performance of the composite fuel.To further study the pressurization performance of Al-Mo alloy fuel.A metal fuel combustion pressure test platform has been developed independently.The constant-volume and equicaloric combustion experiment was used to explore the influence of gaseous product on pressure of oxygen bomb,and record the pressure change curve.The XRD and in-situ SEM were used to characterize the phase composition and morphology of the volatile product.The results showed that Al-Mo alloy fuel show obvious pressurization effect,which is attributed to the presence of gaseous Mo O₃ with low-boiling point.Al-20Mo alloy fuel has the best pressurization effect,the maximum pressure is 3.413 MPa,and the maximum pressurization rate is 1.151 MPa/s,which is 44.9%higher than pure Al.For Al-20Mo-PMF composite fuel,the addition of PMF is conducive to the overflow of gaseous products,while too much PMF will inhibit the oxidation of the composite fuel,and part of the Al and Mo elements will even be carbonized.When the PMF content is 5%,the energy and pressurization performance of the composite fuel reach the best.In summary,Al-Mo alloy fuel and Al-Mo-PMF composite fuel have obvious pressurization effect.The application of it in solid propellants can increase the internal pressure of the engine,reduce the two-phase flow loss,and increase the energy specific impulse.It shows excellent prospects in the field of aerospace and weapon power.