【作者】 周松柏；

【导师】 刘君；

【作者基本信息】 国防科学技术大学 ， 力学， 2009， 博士

【摘要】 本文以超声速内外流干扰为研究对象,以计算方法的建立、验证及应用为主线,采用计算为主、实验为辅的研究方法,对超声速内外流的异质气体干扰特性、非定常喷流干扰控制与燃烧特性等方面开展了研究。发展了层流、湍流、化学非平衡流的统一算法,建立了数值模拟软件,完成了算法的数值验证。该算法的主要特征为:⑴基于多组分NS方程和Menter’s Shear-Stress Transport k ?ω两方程湍流模型,对流动项和化学反应生成源项进行解耦处理,有效解决了化学非平衡流计算中的刚性问题;⑵基于结构网格,采用有限差分法进行方程离散,流动项的时间离散采用Runge-Kutta法(避免了原算法中采用时间分裂法时对差分格式的限制),对流项离散采用NND-1或WAF格式,粘性项采用中心差分格式。数值验证表明:该算法具有较高的时空精度,非常适合对非定常流动尤其是非定常化学非平衡流动进行模拟。基于平面激光诱导荧光技术和纹影技术,设计并开展了异质喷流干扰的一个模型实验。模型实验表明:⑴采用平面激光诱导荧光技术和纹影技术相结合的实验技术,可以对喷流干扰流场进行有效的光学诊断,平面激光诱导荧光技术适合于异质喷流干扰的显示和测量;⑵喷流介质的物性参数(比热比和气体常数)对喷流干扰有重要影响。针对典型异质气体喷流干扰问题,开展了算法的应用。第一,数值模拟了固体火箭发动机尾喷流的干扰流场,分析了工程实验中防护板发生脱落的原因之一在于喷流的引射效应。第二,数值模拟了导弹横喷干扰流场,获得了典型工况下推力放大系数随横喷燃气比热比的关系曲线,建立了一种通过调整横喷总压来关联冷喷和热喷数据的方法。第三,数值模拟了典型超燃冲压发动机燃烧室内的横喷干扰流场,捕捉到了实验没有发现的横喷燃料沿下游运动并向凹腔扩散的非定常流动现象。以超燃实验中的脏空气效应问题为背景,设计了具有随机特性的脏空气来流条件下钝头体激波诱导振荡燃烧的算例,数值研究了来流随机扰动对非定常化学非平衡流的影响问题。在脏空气来流参数和飞行来流参数均值一致的前提下,对脏空气来流工况和飞行来流工况的计算结果进行有效对比,结果表明:当随机扰动最大相对偏差值小于5%时,脏空气来流的随机特性对流动的基本结构演变影响不大,但对流动参数随时间变化的细节有直接影响,且该影响呈无规则、非线性的随机态势。以超燃研究中的增强混合燃烧问题为背景,根据漩涡增强混合燃烧的流动机理,采用非定常流动控制技术,依托多个燃料加注喷嘴进行脉冲式喷注,设计了“新型超燃冲压发动机燃料交替脉冲喷注器”的方案,并对其在典型超燃冲压发动机中的应用特性进行了数值模拟研究。研究表明:采用燃料交替脉冲喷注器进行燃料加注时,燃料以团状进入燃烧室,在漩涡的作用下可充分与空气混合并高效地组织燃烧,可缩短燃烧的流向分布空间,从而有利于通过缩短隔离段和燃烧室的长度来减轻发动机重量。更多还原

【Abstract】 The jet interaction in supersonic external flow was studied by means of numerical simulation and experimental investigation. The development, validation and application of the CFD algorithms for various jet interactions were focused on in the dissertation. And the heterogeneous gas jet interaction characteristics, unsteady jet interaction control and combustion characteristics and so on were studied.The uniform CFD algorithms for the simulation of laminar flows, turbulent flows, chemical nonequilibrium reaction flows were developed. The leading characteristics of the algorithms are: (1) NS equations plus a two-equation turbulence model(Menter’s Shear-Stress Transport model), species conservation equations are used as the governing equations, and an uncoupled method is adopted to simulate chemical nonequilibrium reaction flow which has the stiffness problem. (2) a finite difference method is used based on structured girds, Runge-Kutta method is used for time integration, which could go beyond the limit of difference schemes in time splitting technique, NND-1 scheme and WAF scheme for convection terms’discretization, and central difference scheme for viscous terms’discretization. Numerical validation showed that the uniform CFD algorithms are of higher-order accuracy, and suitable for the simulation of unsteady flows (especially the unsteady chemical nonequilibrium reaction flows).Based on PLIF (Planar Laser-Induced Fluorescence) technique and schlieren technique, a model experiment was designed and carried out for typical jet interaction research. The model experiment showed: (1) PLIF technique and schlieren technique are suitable for the optic diagnosis of jet interaction, and PLIF technique is capable of capturing the flow field of heterogeneous gas jet interaction; (2) the physical parameters (the ratio of specific heats and the gas constant) of jet have an effect upon jet interaction.The CFD algorithms were used to simulate typical heterogeneous gas jet interactions. Firstly, after simulating a solid rocket engine’s jet interaction, it showed that one of the reasons for the shield board’s dropout in experiment is the ejection effect of jet. Secondly, after simulating the lateral jet flow fields of a missile with wings for some different ratios of specific heats and gas constants of the lateral jet, the thrust force amplification factor versus the lateral jet’s ratio of specific heats for typical case was obtained, and a method for correlating the data of cold jet case and hot jet case was constructed by adjustting jet’s total pressure. Thirdly, after simulating the inner flow field of a typical scramjet combustion chamber with fuel jet and cavity structure, the unsteady dynamic phenomenon that fuel jet moves downstream and diffuses into the cavity is captured (The corresponding experiment fails to capture that phenomenon).According to the vitiated air effects in supersonic combustion experiments, an CFD example, which is the oscillating shock-induced combustion of a blunt body with random and vitiated air flow coming from the far field, was designed and simulated for analyzing the effects of the random disturbance on the unsteady chemical nonequilibrium reaction flow field. On condition the mean parameters of the vitiated air were equal to the flight air parameters, the CFD results of vitiated air case and flight air case were compared. The results showed that, when the maximal relative error is smaller than 5%, the random disturbance has less effect upon the basic flow structures, but has an effect upon the variety of typical flow parameters versus time, and the effect is ruleless and nonlinear.According to the problem of enhancing mixing and combustion in supersonic combustion researches, based on the flow mechanism of vortex’s enhancement on mixing and combustion, an“innovative fuel injector with alternate and impulse jet for scramjet”was designed by an unsteady flow control technique with multiple impulse jets, and its application characteristics were simulated furthermore. The results showed that the innovative fuel injector injects fuel into the combustor dollop by dollop, which could enhance the mixing and combustion of fuel and air, and reduce the combustion zone length in the main flow direction, so it is favorable to reduce the length of isolator and combustor, and the weight of scramjet by using the innovative fuel injector.更多还原