【作者】 范周琴；

【导师】 刘卫东；

【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】 论文以超燃冲压发动机燃烧室内部的超声速燃烧现象为研究背景,以超声速燃烧火焰面模型为主要研究对象,综合运用理论分析、数值计算、实验研究等多种手段对超声速燃烧火焰面模型进行了系统、深入的研究。根据火焰面模型的基本思想,系统介绍了层流扩散火焰面理论、低速湍流燃烧火焰面模型、超声速湍流燃烧火焰面模型及相应的火焰面数据库生成方法;针对超声速流的特点并结合当前超声速流中火焰面模型的修正方法,建立了考虑激波作用的超声速燃烧稳态火焰面模型。针对超声速燃烧流场是否能用火焰面模型进行描述这一根本性问题,从理论上系统地对超燃冲压发动机燃烧室内部的超声速燃烧流场是否满足火焰面模型假设进行了判别。结果表明,对于预混燃烧,由于实际低速回流区/剪切层中脉动速度较低,所有飞行马赫数下的超声速燃烧流场均满足火焰面模型假设;对于非预混燃烧,除高飞行马赫数下极小部分燃烧流场位于慢化学反应区外,其余状态也均满足火焰面模型假设。针对稳态火焰面模型在临界标量耗散率附近的处理方法会导致解的不连续,进而可能引发流场非物理解和数值不稳定等缺陷,参考低速流中的火焰面/进度变量模型,建立了考虑激波作用的超声速燃烧火焰面/进度变量模型,并提出了一种高效的火焰面数据库生成方法。为了考察所建立的火焰面/进度变量模型用于描述带有复杂构型超声速燃烧流场的适用性,采用实验和数值计算两种手段分别对带有支板和凹腔的超燃冲压发动机燃烧室内部燃烧流场进行研究。实验与计算结果的对比分析表明,文中所建立的火焰面/进度变量模型可用于描述带有复杂构型的超声速燃烧流场。对于带有支板的超声速燃烧流场,通过数值计算定量研究了燃料喷注当量比、支板厚度等因素对燃烧效率的影响,发现燃料喷注当量比和支板厚度对燃烧效率影响较小。对于带有凹腔的超声速燃烧流场,通过数值计算定量研究了燃料喷注角度、燃料喷注当量比、多凹腔构型等因素对燃烧效率的影响,发现燃料垂直喷射时燃烧效率较高;燃料喷注当量比对燃烧效率影响较小;串联凹腔构型会使燃烧效率提高,并联凹腔构型单侧喷注燃料时对燃烧效率几乎没有影响,反而会使流场总压损失增大,但并联凹腔构型双侧喷注燃料会使燃烧效率大幅提高。更多还原

【Abstract】 The present research investigates the supersonic combustion in a scramjet combustor and develops a new flamelet model for supersonic combustion. The new flamelet model was implemented based on the in-house hybrid LES/RANS code and validated by experimental investigations.Firstly, flamelet model for turbulent combustion in low-speed flow was introduced based on basic theory of flamlet for laminar flow, then it was extended to supersonic flow and revised according to compressibility and occurrence of shock waves in flow field. A steady flamelet model for supersonic turbulent combustion was established, and it takes into account the effects of shock waves.Secondly, whether the flamelet model is feasible for the supersonic combustion flow field is analyzed by distinguishing whether the supersonic combustion flow field in a scramjet combustor meets the assumptions of flamelet model. The results show that: (i) for premixed combustion, as the fluctuation velocity of the flow in low-speed recirculation zone and mixing layer is very slow, the entire flow field will satisfy the assumption of flamelet model at all flight Mach numbers, (ii) for non-premixed combustion, most parts of the flow field satisfy the assumption of flamelet model and only a small part of the flow field at high flight Mach number does not meet.Thirdly, the processing methods of the steady flamelet model in the vicinity of the critical scalar dissipation rate may result in a discontinuity of the solution. Further, this discontinuity can introduce non-physical solutions and numerical instabilities. Based on the flamelet/progress variable model for the low-speed flows, a new flamelet/progress variable model which takes into account the effect of the shock waves was established. In the meantime, an efficient method for the generation of flamelet data libraries was developed.Finally, in order to validate the applicability of the new flamelet/progress variable model to simulate the supersonic combustion flow field with complex configurations, the supersonic flow and combustion of the scramjet combustors with strut and cavity configurations were investigated through both experimental investigations and numerical simulations. The results indicate that the new developed flamelet/progress variable model is capable of describing the fluid flow and combustion in a scramjet combustor with complex configurations. When the strut thickness and the ER of the fuel change, the response of the combustion efficiency was quantificationally investigated, and the results reveal that the strut thickness and the ER of the injected fuel have little effect on the combustion efficiency. Through the quantificational studies, the influence of the injection angle and ER of the fuel, and the multi-cavity configuration on the combustion efficiency were revealed. The results show: (i) the combustion efficiency is higher when the fuel is injected in a vertical direction than in any other direction, (ii) an increase in the ER has little effect on the combustion efficiency, (iii) cavities installed in tandem can increase the combustion efficiency, (iv) when the fuel is injected from one side of the combustor walls, the cavities installed in parallel have little effect on the combustion efficiency but increase the loss of total pressure, and (v) when the fuel is injected from both sides of the combustor walls, cavities installed in parallel will greatly increase the combustion efficiency.更多还原