RBCC引射模态DAB模式二次燃烧数值研究

对火箭基组合循环(RBCC)引射模态煤油燃料扩散后体燃烧(DAB)模式二次燃烧过程进行了数值研究。研究中使用了简单快速单步不可逆化学反应模型、三维非结构网格有限体积方法和k-ε湍流模型。结果发现引入DAB燃烧后,可以提高系统推力性能,但在地面静止自由引射状态未发现推力正增益;二次燃料喷嘴处于二次燃烧室的后部将更加有利于提高燃烧效率。     

超燃冲压发动机燃烧室亚/超燃模态数值研究

采用Mac Cormack格式、B-L湍流模型及氢/空气两步化学反应模型,计算了双模态冲压发动机燃烧室在不同来流条件和供油规律下的二维燃烧流场。计算结果表明,在相同来流条件下,供油规律对燃烧室的工作模态有着重大影响;在不同来流条件下,可通过调节供油规律,使燃烧室分别实现亚燃模态和超燃模态。     

固体燃料冲压发动机内部套管结构数值分析

为了研究固体燃料冲压发动机内部套管结构调节燃料流量的特性,对某模型发动机的湍流燃烧流场进行了数值分析。研究发现,套管开口靠近有效载荷末端与燃烧室入口收缩段时,燃料流量的变化速度较快,而在二者之间的位置基本保持不变;套管开口紧贴有效载荷末端时,燃烧室出口燃烧效率较无套管有所提高,套管向下游移动,将使燃烧室出口燃烧效率降低;套管壳体的最高温度出现在套管出口位置,应适当加强套管末段的热防护。     

PMMA在固体燃料冲压发动机中燃烧特性的数值模拟

为了解PMMA在固体燃料冲压发动机燃烧室内的燃烧特性,采用RNG κ-ε模型、涡耗散湍流燃烧模型和一阶迎风格式,对以PMMA为燃料的固体燃料冲压发动机燃烧室进行了数值模拟,得到了燃烧室内的流场结构、温度及组分分布.通过比较数值计算结果与国外试验数据,验证了该数值方法的可靠性.研究表明,随着轴向位置的增大,燃料局部退移速...     

高过载条件下固体火箭发动机绝热层失效研究

根据化学反应／两相流耦合,建立了铝粒子燃烧模型,通过化学反应速率模型的模化湍流燃烧,对含铝推进剂固体火箭发动机在高过载条件下的内流场进行数值研究。结果表明,过载条件下燃烧室局部异常铝滴积聚及剧烈的化学放热反应是导致绝热层异常烧蚀的主要原因。     

固液混合火箭发动机燃烧室和喷管流动数值模拟

固液混合火箭发动机是采用液体作为氧化剂,固体作为燃料的一种典型的混合火箭发动机.固液混合火箭发动机中的燃烧和流动问题是固液混合火箭发动机设计中的关键问题,对固液混合火箭发动机的燃烧室和喷管进行一体化计算很有必要.利用二维轴对称N-S方程和组分方程对选用液氧/端羟基聚丁二烯推进剂的固液混合火箭发动机的燃烧室和喷管进行了一体化计算.计算采用LU时间隐式格式、MUSCL空间离散和Van Leer矢通量分裂方法,采用有限速率化学反应模型,对化学源相进行了点隐式处理.计算中分别采用了一步化学反应模型和两步化学反应模型方案,计算了多个氧化剂流速和燃烧室压强下的燃烧室和喷管流场分布,对化学模型进行了选择,为固液混合火箭发动机的设计提供了依据.     

Al/AP粉末发动机燃料喷射流场的数值研究

为研究Al/AP粉末发动机燃料输送方式对粉末分散及混合效果的影响,利用气相控制方程、湍流模型、欧拉模型,对金属粉末发动机粉末燃料喷射掺混过程进行了详细的数值模拟。数值计算结果表明:固相体积分数和喷射入口有无锥体结构对流场参数具有较大影响。随着Al/AP粉末入口固相质量分数增加,粉末混合区域由燃烧室尾部向燃烧室头部移动。入口处安装锥体有利于粉末在燃烧室内分散,燃烧室头部颗粒相质量分数增加,轴线上平均固相质量分数降低,喷管前粉末局部积聚现象消失。     

H2O2固液混合发动机燃烧流动计算分析

建立了H2O2固液混合发动机催化分解、PE燃料热解和热解气体与氧化剂分解气体扩散燃烧的综合模型，根据发动机实际工部采用可压SIMPLE方法计算了发动机二维燃烧室内流场，对燃烧室流场的计算结果与燃烧室热力计算结果进行了对比，证明内流场的计算结果符合实际情况，根据燃烧室内流场计算结果，分析了固液混合发动机试验中出现的氧化剂入口附近燃料表面燃烧局部强化的现象。     

RBCC燃烧室超声速反应混合层特性的大涡模拟

以飞行马赫数为4.5Ma的RBCC发动机典型工作状态为研究背景,采用大涡模拟研究了支板火箭射流和空气来流形成的超声速反应混合层的掺混燃烧过程,获得了燃烧室内详细的流场结构和流动特征,分析了强射流条件下超声速反应混合层的特性。结果表明由于速度梯度的存在,火箭射流进入燃烧室后与空气来流形成环形剪切层,剪切层内丰富的旋涡结构主导火箭射流和空气来流的掺混燃烧,随着湍流能量的串级输运,化学反应过程中释放的能量将被转化成细观尺度的湍流动能,大尺度旋涡将能量传递给小尺度旋涡并最终耗散,细小尺度的旋涡一方面能够促进燃烧反应物的掺混并强化燃烧过程,另一方面会给化学反应过程带来强烈的脉动,使得局部火焰淬灭,火焰结构表现出明显的非定常性。     

当量比对超声速燃烧室性能影响的数值研究

采用欧拉-拉格朗日法在来流Ma=2的条件下,对带支板凹腔组合结构的煤油超燃燃烧室的内流场进行数值计算,分析了燃烧室下游支板不同当量比对燃烧室燃烧流场的影响,并对燃烧室的性能做了定量分析。研究表明,随下游支板燃料当量比增加,燃烧反压对燃烧室上游影响加重,流动分离区扩大,上游燃料发生亚声速燃烧状态,且亚声速燃烧区域变大。在支板和凹腔共同作用下,凹腔后方形成了亚声速燃烧区和超声速燃烧区,当量比增加时超声速燃烧区减小,亚声速燃烧区扩大,从而有利于燃料的充分混合和燃烧。随当量比增加,燃烧室总压恢复系数和推力增加,燃料消耗率和比冲量减小。     

水反应金属燃料发动机三维两相燃烧数值模拟

用三维湍流N-S方程及颗粒轨道模型描述水反应金属燃料发动机内部喷雾两相湍流燃烧过程。通过耦合求解气液两相流模型方程,得到发动机燃烧流场。通过模拟Mg与水的反应,分析比较了一次和二次进水方案的不同流场特性。研究结果表明,二次进水方案更有利于火焰稳定和提高燃烧性能。     

Numerical study on operating characteristics of a magnesium-based fuel ramjet

A two-dimensional axis symmetrical model for multi-phase turbulent combustion simulation has been developed in a magnesium-based fuel ramjet, the stochastic model is applied to track the motion and transportation of discrete phase in the whole flow field in Lagrangian frame. Firstly, the flow field parameters distribution including temperature, velocity, Mg particle burning rate, main components are obtained to describe the basic operating characteristics, and the thermoacoustic oscillation during the combustion process is predicted due to the observed vortex. Then combined with the developed thermodynamic calculation program, the influencing rules of water/fuel ratio and magnesium-based fuel composition ratio on ramjet operating characteristics are analyzed. The results obtained show that the distribution of two water/fuel ratios exerts a direct impact on the temperature fluctuations in combustor, further influences the combustion stability, as for theoretical specific impulse, a maximal value is observed along with the total water/fuel ratio, while the monotonous trends for thermal efficiency and propulsive efficiency are achieved respectively. Moreover, the magnesium-based fuel composition ratio is a dominant factor to influence the operating characteristics, and it is proved that the high-proportion Mg in fuel is beneficial to specific impulse augment through validation of both simulation results and thermodynamic calculation results.     

An experimental study on the stability of jet diffusion flame

The stability behavior of jet diffusion flame developing in a coflowing high temperature air stream was studied experimentally, using city gas and hydrogen as fuel gases. The primary variables studied were temperature and velocity of the air stream. Two distinct types of stability limits were observed. The first is the blow-off of the rim-stabilized flame, which is familiar and has been studied by a number of investigators. The second is the break-off or extinction of the turbulent portion of the flame at the transition point from laminar to turbulent flow. The second limit is quite unfamiliar and is interesting in relation to the structure of turbulent diffusion flames. The important implications of the experimental findings concerning the stability and the structure of turbulent diffusion flames is discussed.     

Two-phase flow effect on hybrid rocket combustion

This study numerically explores the aerodynamic and combustion processes in a hybrid rocket combustor, under a two-phase turbulent flow environment, considering the evaporation, combustion and drag of droplet and droplet ignition criterion. The predictions of temperature, reaction mode, reactant mass fraction, velocity, oxidizer consumption, fuel regression and droplet number distribution enhance understanding of the two-phase combustion aerodynamics inside the combustor. A parametric study of the inlet spray pattern, including spray cone angle, spray injection velocity and droplet size, is performed to improve the operation of reactant mixing and higher fuel regression rate. Analytical results indicate that both the oxidizer consumption and the fuel regression increase with increasing spray cone angle and spray injection velocity in the practical range of operation. However, for stoichiometric operation, the superior spray cone angle is within 20–60°, and spray injection velocity within 20–40 m/s, under a volume-mean droplet radius of 50 μm. The power dependence of solid-fuel regression on total mass flux is found to decrease with rising of droplet mean size.     

固体火箭冲压发动机性能调节研究

在对固体火箭冲压发动机的高度特性进行分析的基础上，分别研究了壅塞式和非壅塞式固体火箭冲压发动机性能调节特性及方案，并着重分析了非壅塞式固体火箭冲压发动机的燃气流量自适应调节原理与规律，分析计算表明，非壅塞式固体火箭冲压发动机不仅结构简单，且能明显提高发动机在非设计状态时的性能。     

Large eddy simulation based studies of jet–cavity interactions in a supersonic flow

Interactions of a cavity flameholder with an upstream injected jet in a Ma 2.52 supersonic flow are investigated numerically. A hybrid RANS/LES (Reynolds-Averaged Navier–Stokes/Large Eddy Simulation) method acting as wall-modeled LES is adopted, for which the recycling/rescaling method is introduced to treat the unsteady turbulent inflow. Patterns of the fluid entrainment into the cavity and escape from the cavity are identified using a scalar-tracing method. It is found that the jet–cavity interactions remarkably enhanced the mass exchange between the fluids in and out of the cavity, resulting in reduced residence time of the cavity fluids. Increasing the distance between the fuel injection and the cavity leading edge tends to attenuate the jet–cavity interactions, leading to weaker mass exchange. Raising the injection pressure appears to enhance the jet–cavity interactions, resulting in a shorter residence time of the cavity fluids. Moreover, the mass decay processes for the fuel and air within the cavity are basically the same while the entrainment processes for the fuel and air into the cavity seem quite different.     

水反应金属燃料能量特性分析

提出了水反应金属燃料与水/金属燃料发动机概念;通过比较多种化学推进剂能量特性,可知水反应金属燃料能量密度明显高于传统火箭燃料,可以预见它在水下高速推进系统中具有广阔应用前景;通过热力计算,分析了水反应金属燃料能量特性的影响因素.     

空气涡轮火箭发动机掺混燃烧研究进展

在混流燃烧室内组织富燃燃气与空气的高效稳定掺混燃烧对于空气涡轮火箭发动机（ATR）性能至关重要。回顾了国外各研究机构关于ATR掺混燃烧方案的试验研究,对波瓣混流器在航空领域强化内、外涵气流掺混中的典型应用及研究成果进行总结评述,总结并提出ATR掺混燃烧的特点和关键问题,分析了后续掺混燃烧研究中需重点关注的问题。     

Combustion characteristics of the end burning hybrid rockets in laminar flow

In this study, we aim to clarify the blowoff mechanism for flame spreading in an opposed laminar flow in narrow solid fuel ducts. To clarify this mechanism we conducted two experiments. First, we observed the changes of the flame spread rate at various oxygen velocities, ambient pressures, and port diameters. For flame spreading in laminar flow, combustion modes could be classified into 3 distinct regimes based on the strength of the opposed flow, i.e., chemical regime, thermal regime, and stabilized regime. This result is consistent with the result in turbulent flow. In the stabilized regime, quenching distance is almost constant despite oxygen velocity. In order to investigate the effect of ambient pressure and port diameter of fuels on blowoff limit, transition oxygen velocity is observed. As a result, transition oxygen velocity is proportional to the logarithm of the ambient pressure and port diameter. This relation is applicable despite the flow condition. Furthermore, we calculated velocity gradient at the fuel surface to reveal the determining factor of the blowoff limit in laminar flow. Consequently, velocity gradient, which is considered to dominate flow separation in laminar flow, would not be constant. This is because the velocity gradient at the fuel surface could not be evaluated by only the assumption of Hagen–Poiseuille flow but other parameters, such as vaporized fuel gas and natural convection by buoyancy should be included.     

水反应金属燃料发动机的性能调节

在水反应金属燃料发动机性能分析研究基础上,分析了壅塞式和非壅塞式发动机构型优缺点及性能调节特性,着重探讨了非壅塞式水反应金属燃料发动机燃气流量自适应调节规律和特点。计算结果分析表明,非壅塞式发动机具有水燃比自适应调节特性,且高压强指数水反应金属燃料调节效果显著。