【作者】 周超；

【导师】 郑亚；

【作者基本信息】 南京理工大学 ， 机械电子工程， 2009， 博士

【摘要】 以微小型姿控膏体推进剂火箭发动机应用为背景,对膏体推进剂流变学特性、供给方式、管道输送特性和流动数值仿真方法进行了研究,为发动机输送系统设计及优化奠定了理论及实验基础。本文首先对四种膏体推进剂配方样品和三种模拟液样品开展了流变学测试研究,分析稳态和动态测试结果曲线可以得到如下结论:配方中增稠剂含量对膏体推进剂粘度和流动特性有显著影响,并且这种影响在不同剪切速率下表现一致。配方中氧化剂和还原剂的种类对样品粘度有明显调节作用,但在高剪切速率下这种调节作用减弱。动态测试结果表明,膏体推进剂的应力松弛过程与初始应变有关,初始应变越大,应力松弛过程速度越快,曲线也越陡。蠕变/恢复结果表明,在流动中膏体推进剂的粘性表现比弹性表现更明显。模拟液的流变测试结果显示增加固体颗粒含量在不同温度下都使样品粘度增加,但对储能模量和损耗模量等动态特性没有明显影响。温度对模拟液的影响同时表现在粘度和特征剪切速率两方面。在总结现有膏体推进剂供给系统的基础上,针对姿控发动机应用特性提出了新型膏体推进剂供给方式,以转速控制代替截面控制达到流量调节的目的。为了验证新型供给方式,建立了模拟供给实验平台,并作为管道流动试验的供给系统。对膏体推进剂及模拟液进行了管道流动试验,试验分两部分:一是PIV测速试验,得到了模拟液之一—丁羟(HTPB)圆管内速度分布,经比较与理论结果符合较好。二是推进剂及模拟液的管道测压试验,通过对直管输送研究,验证了沿程阻力系数与广义雷诺数的关系符合λ=64/Re_g;对突变截面和弯管道的研究表明,局部阻力系数与广义雷诺数的关系近似满足指数为-1的幂函数规律,随着雷诺数的增大,局部阻力系数减小。对于变截面管道,截面变化比β越接近1,局部阻力越小,对于弯管管道,弯径比d/R越大,局部阻力越小。通过拟合试验数据建立了局部阻力系数计算经验公式。综合流变学测试数据和管道流动数据,得到了膏体推进剂及模拟液的本构关系及相关参数。以0.001 1/s剪切速率下的粘度作为样品零剪切粘度,得到了不同温度下样品相对粘度与固体颗粒体积分率的关系:η/η_r=1+6.92φ+126.9φ~2,与文献表达式对比可以看出,膏体推进剂模拟液的相对粘度的增长随固体体积分率增长较快。以直管道和变截面管道为研究对象,探讨了膏体推进剂管道流动数值模拟方法及过程,研究结果表明,在考虑了壁滑移特性后,数值仿真方法能较准确预测直管流动阻力,但对变截面管道局部阻力的预测与试验值相差较大。更多还原

【Abstract】 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.更多还原