以固体燃料和液体氧化剂为推进剂的固液火箭发动机具有结构简单、安全 环保、成本低廉、推力可调节及和可重复启动等优点，是当前火箭发动机领域 的研究热点。然而，由于固液火箭发动机的燃烧过程非常复杂，涉及燃料药柱 的受热热解、气化、氧燃掺混和燃烧等多个物理化学过程，是药柱内部封闭空 间的有限扩散燃烧，目前诸多燃烧诊断技术难以应用，导致其燃烧特性缺乏认 知，尤其缺乏动态工况下例如氧燃比、退移速率和内部流动等持续变化对于发 动机燃烧特性影响规律的理解，严重限制了固液火箭发动机的发展。因此，迫 切需要一种基础实验和测量方法，掌握发动机内部的火焰结构数据，开展固液 火箭发动机动态燃烧特性的研究。本文以精确刻画发动机动态火焰结构以及探 索火焰结构与燃烧特性关联性为目标，发展了一种基于多角度辐射成像的火焰 动力学分析方法，能够在不干扰流场、不借助外部光源激励的情况下，得到固 液火箭发动机燃烧室内部的火焰图像，提取火焰的主要脉动特征，对于深入固 液火箭发动机的动态燃烧特性具有重要意义。本文主要工作如下： 首先，提出了一种基于内窥式成像光纤的固液火箭发动机燃烧室火焰动力学 研究方法。针对真实的固液火箭发动机设计了多角度成像光路，以聚乙烯螺旋孔 药柱和圆孔药柱作为燃料，进行点火实验验证了多角度成像光路的可行性，并对 原始图像的火焰动力学特性进行了分析。使用了本征特征值分解方法（Proper orthogonal decomposition, POD）提取了火焰的主要脉动结构。最后结合发动机退 移速率和特征速度，对燃烧性能进行了评价。结果表明螺旋孔药柱的火焰脉动更 强、火焰区更宽，并产生了更强的湍流和火焰脉动特性。证明了螺旋孔药柱能够 有效地提高发动机燃烧室内的流动湍流度，增强对流换热，从而有效地提升药柱 的退移速率。 第二，扩展并应用了固液火箭发动机燃烧室火焰动力学研究方法，开展了旋 流/特征结构协同作用下复合式药柱火焰动力学特性实验研究。使用圆孔石蜡基 药柱、螺旋孔丙烯腈-丁二烯-苯乙烯嵌套石蜡基燃料复合药柱，在氧气直流喷注 和旋流喷注的情况下，采集了燃烧室内的火焰图像，并对其火焰动力学特性展开 了分析。使用 POD 方法和动态特征值分解方法对火焰图像的主要脉动特性进行 了提取与分析，发现直流喷注下，复合式螺旋孔药柱相比圆孔药柱火焰区更广且 脉动性更强。旋流喷注火焰结构更加清晰，燃烧室内的火焰可以观察到明显的旋 转特性；且当氧化剂喷注方向和药柱螺旋结构方向相同（同向旋流）时，火焰主 要位于螺旋沟槽内部并更贴近药柱表面，当氧化剂喷注方向与药柱螺旋结构方向 相反（反向旋流）时，火焰主要位于燃烧室内并具有更强的湍流度。证实了复合式螺旋结构药柱主要通过增强湍流度加强对流换热从而提高退移速率；而旋流喷 注能够有效压缩火焰，使火焰更加靠近燃料表面，从而加强换热提高退移速率， 且同向旋流的压缩效果比反向旋流更强。

Hybrid rocket motor, typically using solid fuel and liquid oxidizer as propellants, which has the advantages of simple structure, high safety, environmental friendly, low cost, thrust adjustability and restart capability and so on, is currently a research hotspot in the field of rocket motors. However, the combustion process of hybrid rocket motor is highly complex and belongs to the typical limited diffusion combustion, coupled with multiple physical and chemical processes including fuel heating, pyrolysis, oxidizer mixing and combustion of the mixture. Currently there is no unified understanding of the dynamic combustion characteristics of hybrid rocket motors and no accurate evaluation methods for the combustion performance. Thus, it is critically important to develop an experimental and measuring technique to obtain the flame structure inside the combustion chamber of the motor to deepen the understanding of the dynamic combustion characteristics of hybrid rocket motors. Aiming to accurately depict the flame dynamics and its correlation to the combustion characteristics, this paper develops an analysis method of flame dynamics based on a multiangle radiation imaging system. This method is able to intrusively obtain the flame structure inside the combustion chamber of the hybrid rocket motor and extract its main fluctuation characteristic without external light sources, which vitally important for the understanding of the combustion characteristic of hybrid rocket motors. The main work of this paper is as follows: Firstly, an analysis method of the flame dynamics of hybrid rocket engine combustion chambers based on endoscopic imaging optical fibers was proposed. A multi-angle imaging optical system was designed for the configuration of a real hybrid rocket motor. The multi-angle imaging system was verified in the firing tests using polyethylene helical and circular fuel grain as propellant, and the flame dynamics characteristics of the raw image were analyzed. The proper orthogonal decomposition (POD) method was used to extract the main fluctuation characteristics of the flame. Finally, the combustion performance was evaluated by analyzing the motor’s regression rate and characteristic velocity. The results indicate that the helical grain’s flame zone is wider, and stronger turbulence and flame fluctuation characteristics are generated. It has been proven that helical propellant can effectively improve the flow turbulence in the combustion chamber of the motor, enhance convective heat transfer, and thus effectively improve the regression rate of the propellant. Secondly, the analysis method was extended and applied, and experimental research on the flame dynamics of a novel composite grain flames under the effect of swirl injection was conducted. Using circular paraffin grain and a novel acrylonitrile butadiene styrene nested paraffin-based fuel as propellent, flame images in the combustion chamber were collected under the conditions of oxygen direct injection and swirl injection, and their flame dynamics characteristics were analyzed. The flame dynamics characteristics of the raw image were analyzed, and the main fluctuation characteristics of the flame image were extracted and analyzed using POD method and dynamic eigenvalue decomposition method. It was found that under direct injection, the composite helical grain had a wider flame area and stronger fluctuation compared to the circular grain. The structure of the swirling injection flame is clearer, and obvious rotational characteristics of the flame in the combustion chamber can observed. Additionally, when the direction of the oxidizer injection is the same as the direction of the helical structure of the grain (co-swirl), the flame is mainly located in the helical groove and closer to the surface of the grain. When the direction of the oxidizer injection is opposite to the direction of the helical structure of the grain (counter-swirl flow), the flame is mainly located in the combustion chamber and has stronger turbulence. It has been proven that the composite helical structure grain mainly enhances convective heat transfer by enhancing turbulence of flow; swirl injection can effectively compress the flame, making it closer to the fuel surface, thereby enhancing heat transfer and increasing the regression rate. Moreover, the compression effect of coswirl flame is stronger than that of counter-swirl flame.