【作者】 李理；

【导师】 杨涛；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2011， 博士

【摘要】 固体火箭冲压发动机以其高速、大比冲和机动能力强的特点成为了现代战争中极具发展前景的武器动力装置之一。热防护是固冲火箭发动机研制过程中的一大关键技术问题，也是多年来制约固冲发动机发展的问题。开展固冲发动机烧蚀机理研究对推动固冲发动机发展具有相当的理论和工程意义。本文以采用硅基绝热层的冲压发动机为研究对象，以理论分析，数值计算和试验分析相结合的方法对硅基绝热层的烧蚀问题进行研究，并以相关研究结论为依据对进气道进行了优化设计，使进气道获得最大总压恢复和最小绝热层烧蚀率。首先，以经典传热理论为基础建立了硅基绝热层热化学烧蚀模型。二维数值模拟结果表明温度控制了发动机绝热层的烧蚀速度。温度的不均匀性分布是导致烧蚀坑出现的主要原因之一。以CVT插值方法实现了流固耦合的边界数据交换，对发动机烧蚀问题进行了三维数值模拟。在进气道进口两侧的高温区逐渐形成了由化学反应引起的烧蚀坑。而在补燃室下游区域，由于近壁面气流温度下降较快，烧蚀则不明显。当碳化层形成后，绝热层烧蚀现象增速很快。在碳化层形成后，在稳定的流场环境下，化学烧蚀即趋于稳定。根据硅基绝热层的特点，分析了硅基绝热层烧蚀的三种形式，包括气动冲蚀，颗粒剥蚀和热化学烧蚀。在硅化物生成率是稳态的假设条件下，建立了补燃室绝热层的烧蚀模型。对试车试验工况下的发动机进行了数值模拟，分别计算了化学烧蚀率，气动冲蚀率和颗粒剥蚀率。综合计算结果，对于硅基绝热层，在硅化物形成后发生的气动冲蚀率是造成补燃室绝热层失效的主要原因之一。气动冲蚀效应较强的区域是进气道开口后半段两侧及紧靠进气道的部分区域。分析了颗粒相与壁面碰撞后的运动形式，分别模拟了固相与液相颗粒对绝热层的影响。颗粒相对绝热层的影响主要是强化绝热层传热和颗粒冲蚀两个方面。对绝热层热增量有较大影响的颗粒是粒径较大，速度较快的液相颗粒，与壁面碰撞后的运动形式为飞溅形态。对颗粒冲蚀效应有较大影响的仍然是粒径较大的颗粒。颗粒冲蚀较严重的区域是补燃室的中部。研究了发动机结构特征参数对绝热层烧蚀的影响。燃气发生器喷口结构对于补燃室的烧蚀形态有着一定的影响。相比五喷口燃气发生器，采用单一喷口烧蚀率较低。燃气发生器间的喷口间距增大对气流冲蚀的影响不大，但化学烧蚀率提高较大。进气道进气角度对气动冲蚀率有着较大影响。在其他进口条件不变的情况下，进气角度较小时，气流冲蚀影响区域在轴向上范围扩大，但是周向影响区域减小，最大气流冲蚀率有小幅减弱；近壁面燃气流温度较高，绝热层表面化学反应速度较快，使得化学烧蚀率提高。进气道出口面积缩小使得空气来流速度提高，气流冲蚀率形态呈现出影响范围沿轴向较长的特点，最大冲蚀率也出现了小幅下降。在对发动机参数对进气道的影响分析基础上，对进气道进行了优化设计。进气道内通道设计中，以补燃室的绝热层是气动冲蚀率与内通道长度为优化目标对内通道进行了优化设计。优化分析结果表明，内通道平直扩张段对内通道长度的影响是单调的。更多还原

【Abstract】 Solid Ramjet features with its high velocity, high specific impulse and wellmaneuverability. These merits make it a good candidate of weapon power system.Thermo Protection is a key technology in ramjet development. And it’s also the bottleneck in solid ramjet research. So, the research on ramjet insulator ablation would makesignificant progress on ramjet research.In this paper, one kind of silica insulators has been taken into research. Approachesof theory analysis, numerical computation, and experimental study have been applied inthis research. And with the conclusion of this research, the ramjet inlet has been optimaldesigned, in order to maximize total pressure recovery and minimize insulator ablationrate.First, thermo-chemical ablation model has been established based on classicalthermo transfer theory. A2-D numerical simulation result shows that the temperaturecontrols insulator ablation rate. And non-uniform temperature distribution inducesablation holes on insulator surface. With the method of CVT, Constant-VolumeTetrahedron, boundary condition problems on fluid-solid interface have been solved.And a3-D numerical simulation has been computed. On the two sides of each inlet,there are two zones of high temperature, and also two ablation holes. The temperature ofzones that downstream of the combustion chamber declines quickly. And insulatorablation on these zones is not such serious as zones besides the inlet. The ablation rategets bigger while the char layer generates. And also chemical ablation rate wouldgradually approach a constant after char layer generates.According to silica insulator ablation features, three kinds of insulator ablationmechanics have been analyzed, including ablation due to gas blowing, particleimpingement and thermo-chemical ablation. Based on the assumption of stable silicidesgeneration rate, the insulator ablation model has been established. It is calculated thechemical ablation rate, gas-bolowing ablation rate and particle erosion rate under acertain condition. The numerical simulation result shows that, among these3mechanics,gas blowing is the main effect causing TPS failure. The zones besides inlet anddownstream the combustion chamber are seriously ablated. The gas temperature is veryhigh in this zone.The particle movement after impingement has been analyzed. The effect of solidparticles and liquid particles to insulator ablation has been argued. Heat transfer andparticle erosion are the main particle effects. The liquid particles, with high speed andlarge particle diameter, strengthen insulator heat transfer. After impingement, rather thanadhering on the insulator, they all split into small particles, and spray out. Also, particlesof large diameter charge the particle erosion. The zones with serious particle erosion locate at the centry of the combustion chamber.Ramjet structure parameters’ effect to insulator ablation has been argued. It isfound that the structure of gas generator outlet affects insulator ablation. The insulatorablation of the one having only one jet on gas generator declines while compared to theone having5jets. The zone with most serious ablation moves to the downstream of thecombustion chamber and is far from the inlet. The distance of two neighbor jets haslittle affect to ablation due to gas blowing, but heavily affects the chemical ablation.The inlet angle affects ablation due to gas blowing. Small inlet angle makes themaximum ablation rate decreases. Small inlet angle also makes temperature of the gas,adjacent to the chamber wall, increases. But this makes the chemical ablation rate getlarger. Inlet area reducing enhances the velocity of air flow. And this makes themaximum ablation rate decreases.Based on the conclusions of other ramjet structure parameters’ effects on inlet, theinlet has been optimal designed. Minimizing gas-blowing ablation rate and the tunnellength are taken as two optimal targets in inner tunnel design. The optimal results shows,the length of flat tunnel has little affect on the tunnel length. Inlet angle affects both theablation rate and inlet inner tunnel length.更多还原