The Study On Rheological And Supply Behaviour Of Pasty Propellant

On the background of the application of microminiature pasty propellant rocket, the rheological characteristic of pasty propellant,the supply method,the pipe transportation and the numerical simulation for pipe flow are studied in this paper. The purpose is to establish theoretical and the experimental foundation for the design and the optimization of pasty propellant expulsion system.The research work is started from rheology tests for four kinds of formulations of pasty propellant samples and three kinds of formulations of pasty propellant simulants. From the steady and dynamic test results,following conclusions can be made.The content of thickening agent has clear influence on viscosity and flow characterisitc of pasty propellant,and this influence shows accordance at different shear rate interval. The species of oxidizer and reducer affect sample's viscosity,but at high shear rate, the fluent tends to weaken.The stress relaxation process of pasty propellant is related to initial strain.The initial strain is bigger,the stress relaxation speed is high,and the curve is also steeper.The creep and recovery test show that the recovery quantity takes up a small proportion in totally strain.So viscosity characteristic is more important than elasticity in flow.As to simulants,increasing the volume fraction of solid particle makes the viscocity of simulants increase.But there is no clearly different about dynamic characteristic of two kinds of HTPB/salt suspension. Temperature changes both of viscosity and the key shear rate at which the simulants converts from Newtonian to non-Newtonian behavior.Based on summarying of existing supply systems,a new kind of supply method is proposed for aerospace attitude control use.In the new system,the flow rate is managed with controlling rotation speed of moto instead of changing the coss area of flow.In orde to test the new supply method,an artificial experimental system is setup and serves as supply system for pipe flow experments.The pipe flow experiments are conduced with pasty propellant and three kinds of simulants.The tests include two sections:one is using PIV technology to study velocity profile of HTPB flowing in round pipe.The results appear that the velocity profile has the parabolic shape and is accord with theoretical result well.Another section is pipe flow experiments with pressuer and volume flow rate measurement. Based on the straight pipe experiments,conclusion can be made that the energy loss coefficient of pasty propellant for laminar flow has the same forms as Newtonian fluid, that isλ=64/Re_g.The energy loss caused by contraction/expansion and 90°bend is also researched.The empirical formula for local engery loss coefficient K is derived by analysis and fitting experimental data.In the laminar region with low Reynolds number,local engery loss coefficient decreases when Reynolds number increases.As to sudden area change,local engery loss coefficient decreases along with the ratio of the cross-sectional areasμtending to 1.As to 90°bend component,local engery loss coefficient decreases with increasing of ratio of curvature and diameter R/d.On the basis of rheolohical tests and pipe flow tests,the constitutive Equations of pasty propellant and simulants are established with consideration of temperature influence. Taking shear viscosity at shear rate 0.01 1/s as zero shear viscosity,the relative viscosity of pasty propellant simulants varies with solid volume content in accord with the equation:η//η_r=1+6.92φ+126.9φ~2.Comparing with literature,the result indicates that the pasty propellant simulants' relative viscosity increase with solid volume content more quickly than other kinds of suspension.Taking straight pipe and contraction/expansion pipe as research object,numerical simulation of pasty propellant flowing in pipe is investigated.Camparing simulation result with experimental result,the conclusion can be made that,with considerion of wall slip condition,numerical method can predict laminar flow route loss accurately, but cann't pridict the local loss well.