【作者】 刘晨；

【导师】 伍贻兆；

【作者基本信息】 南京航空航天大学 ， 流体力学， 2009， 博士

【摘要】 随着吸气式高超声速飞行器的发展,超声速燃烧冲压发动机的研究得到了世界各国的高度重视。超燃冲压发动机燃烧室工作过程复杂,其内部流场是复杂的三维流动,充满着激波、膨胀波、燃烧波、各种涡系、附面层及其相互之间的干扰,对于液态燃料还包含燃料的雾化、变形、蒸发、碰撞、破碎等复杂的物理过程。作为燃烧室设计的关键技术,复杂燃烧流场数值模拟技术的重要性日益显现。本文结合计算流体力学、燃烧学、传热学、多相流等学科,针对燃烧流场中涉及的化学反应、宽马赫数范围、气液两相流掺混等复杂流动现象,发展了基于非结构/混合网格的全速域高效数值模拟算法及大规模分布式并行计算技术,为先进飞行器推进系统的设计提供了有效手段。考虑到在超燃冲压发动机概念设计和初步设计阶段,需要大量分析推进系统的性能,本文发展了一种能够对燃烧室性能进行快速评估的一维流分析方法。对该方法中涉及的控制方程、经验模型、计算方法等方面进行了详细讨论,采用Billig实验模型进行了数值验证,并对一种典型超声速燃烧室几何与燃料喷口参数等对燃烧室性能的影响作了数值分析,分析结果可以给燃烧室的初步设计提供依据。针对气态燃料燃烧流场,以多组分N-S方程为基础,利用高阶迎风格式、湍流模型及有限速率化学反应模型等,发展了基于非结构/混合网格的可应用于全速域燃烧流场数值模拟的大规模并行计算方法。空间离散格式包含AUFS、Van Leer、AUSM+和HLLC/E等迎风分裂格式;湍流模型包含S-A一方程、k-εCMOTT和k-ωSST两方程湍流模型。以对称边界为例,讨论了人工边界条件处理方法对计算结果的影响;利用量级分析的方法,研究了在低马赫数情形时采用预处理方法的必要性和有效性;并详细介绍了几种常见通量分裂格式的预处理方法。利用多个经典算例对本文发展的算法进行了分析和验证。计算结果表明,本文发展的算法对无粘流、层流、湍流、反应流、全速域流等都具有较好的计算精度和可靠性。针对液态燃料燃烧流场,采用Eulerian-Lagrangian方法,基于随机轨道模型,整合现有的液滴蒸发、变形、二次破碎、碰撞聚合、气液相间作用等模型,在气态燃料燃烧数值模拟算法基础上,发展了基于非结构/混合网格的液态燃料燃烧流场数值模拟的大规模并行计算方法。通过验证算例检验了本文发展的气液两相流算法中各子模型的可靠性和计算精度;最后通过Lin的水横喷实验和结合氢引导火焰与凹腔的煤油超燃算例的分析研究,表明了本文开发的算法对液态燃料燃烧流场的模拟能力。更多还原

【Abstract】 With the development of the air-breathing hypersonic vehicle, supersonic combustion ramjet (Scramjet in short) has received more and more attention. In the combustor of scramjet, there are complex phenomena, such as shock, combustion, vortex, turbulence, and the interactions between them. If liquid fuels, such as kerosene, the flowfields of combustor will also contain complex droplet acts, such as droplet evaporation, droplet oscillation and distortion, droplet breakup, droplet collision and coalescence. As one of the key methods, numerical methods for simulating complex combustion flowfields are very important. In this dissert, involving many subjects, such as Computational Fluid Dynamics, combustion science, heat transfer theory, multiphase flow, an efficient parallel method based on unstructured/hybrid meshes for simulating combustion problems at all speeds was developed, and used to analyze the complex phenomenon in the combustor of scramjet, which is helpful for the advanced aircraft propulsion design.A rapid means of predicting the propulsion system is needed for the concept stage and preliminary stage of the scramjet design, so a quasi-one-dimensional analysis model was developed. The equations, experimental models, numerical methods were discussed in detail. Numerical result was compared with Billig’s experiment, which shows the reliability of this analysis model. Using this model, the effects of the expansion angle and the fuel-injector location on the performance of typical supersonic combustor have been studied.Numerical methods for combustion flowlfields of gas fuel were investigated. Based on the multi-component Navier-Stokes equations, an efficient parallel method on the unstructured/hybrid meshes was developed, using higher-order upwind schemes, turbulence models and finite rate chemical reaction model. The equations are solved using the cell-centered finite volume method. Four schemes including AUFS, Van Leer, AUSM+ and HLLC/E can be used for the inviscid flux vector calculation. S-A one-equation turbulence model, k-εCMOTT and k-ωSST two-equation turbulence model are implemented to evaluate the turbulent viscosity. Taking the case of symmetry boundary, the differences between two methods of the boundary were discussed. An order analysis was conducted to search for the convergence characteristics of Euler equations with Weiss-Smith preconditioner in low speed flow. Then several preconditioned upwind schemes were introduced. Many benchmark cases were simulated to validate the capabilities of this numerical method for the invisid, laminar, turbulence, chemical reacting flow, all speeds flow. The results indicate that the numerical method has good resolution and reliability.Numerical methods for combustion of liquid fuels were developed with Eulerian-Lagrangian method. A stochastic particle method was used to calculate the liquid sprays with turbulence effects. Many spray models were implemented to control the behavior of the spray droplets, including evaporation, droplet oscillation and distortion, droplet breakup, and droplet collision and coalescence, the interaction between the ambient fluid and the spray. The performance of individual spray submodels has been validated by comparing the numerical results of some benchmark cases to theory and experimental results from the literature. The performance of the complete numerical method has been explored by investigating the flowfield of a kerosene scramjet model with cavity and pilot hydrogen.更多还原