Abstract Several studies regarding the combustion characteristics of a pintle injector, which is one of techniques for throttling liquid rocket engines, have been conducted; however, the primary focus was on the performance instead of on the flame. To study the fundamental flame characteristics and provide a useful design guide for a pintle injector, gaseous methane and oxygen flames under the laminar condition were visualized by CH* chemiluminescence and Schlieren imaging techniques. The pintle injector used in this study had a fully opened annular injection area, and the combustion chamber was designed as a square cylinder with two windows to visualize the flames. The mass flow rates of methane and oxygen were controlled to change the injection condition, and the pintle opening distance was changed as a geometrical variation. The flame shapes could be classified globally into two types: a shear layer flame, located between two injected propellants and a tip-attached flame located near the pintle tip. The flame angles were measured from deconvoluted flame images, and measured angles were compared with spray angles from previous studies. In conclusion, the flame-anchoring locations and flame shapes were found to be critical for the injection momentum flow rate. Additionally, a new non-dimensional number, the pintle number, K p , for the normalized angle is proposed, and the pintle number has a strong relation with the flame and spray angles. It is expected that the pintle number can be used to design a pintle injector.

中文翻译：

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环形轴针喷油器GOX/GCH4火焰锚固位置和角度特性

摘要 对作为液体火箭发动机节流技术之一的轴针喷油器的燃烧特性进行了多项研究；然而，主要关注的是性能而不是火焰。为了研究基本的火焰特性并为针阀喷射器提供有用的设计指南，层流条件下的气态甲烷和氧气火焰通过 CH* 化学发光和纹影成像技术可视化。本研究中使用的针阀喷射器具有完全打开的环形喷射区域，燃烧室设计为带有两个窗口的方形圆柱体，以可视化火焰。控制甲烷和氧气的质量流量以改变注入条件，并改变枢轴开口距离作为几何变化。火焰形状总体上可以分为两种类型：位于两种喷射推进剂之间的剪切层火焰和位于枢轴尖端附近的尖端附着火焰。火焰角度是从解卷积的火焰图像中测量的，并将测量的角度与之前研究的喷雾角度进行比较。总之，发现火焰锚定位置和火焰形状对喷射动量流速至关重要。此外，还提出了一个新的无量纲数，即归一化角度的轴针数 K p ，轴针数与火焰和喷雾角度有很强的关系。预计轴针数可用于设计轴针喷油器。位于两个喷射的推进剂和位于枢轴尖端附近的尖端连接火焰之间。火焰角度是从解卷积的火焰图像中测量的，并将测量的角度与之前研究的喷雾角度进行比较。总之，发现火焰锚定位置和火焰形状对喷射动量流速至关重要。此外，还提出了一个新的无量纲数，即归一化角度的轴针数 K p ，轴针数与火焰和喷雾角度有很强的关系。预计轴针数可用于设计轴针喷油器。位于两个喷射的推进剂和位于枢轴尖端附近的尖端连接火焰之间。火焰角度是从解卷积的火焰图像中测量的，并将测量的角度与之前研究的喷雾角度进行比较。总之，发现火焰锚定位置和火焰形状对喷射动量流速至关重要。此外，还提出了一个新的无量纲数，即归一化角度的轴针数 K p ，轴针数与火焰和喷雾角度有很强的关系。预计轴针数可用于设计轴针喷油器。发现火焰锚定位置和火焰形状对喷射动量流速至关重要。此外，还提出了一个新的无量纲数，即归一化角度的轴针数 K p ，轴针数与火焰和喷雾角度有很强的关系。预计轴针数可用于设计轴针喷油器。发现火焰锚定位置和火焰形状对喷射动量流速至关重要。此外，还提出了一个新的无量纲数，即归一化角度的轴针数 K p ，轴针数与火焰和喷雾角度有很强的关系。预计轴针数可用于设计轴针喷油器。