A non-intrusive method for determining the time-resolved fuel mass flow rate in a hybrid rocket engine is proposed based on tunable diode laser absorption spectroscopy (TDLAS). The present work performed experimental tests using oxygen/paraffin as the propellant in a laboratory-scale hybrid rocket engine, applying oxidizer-to-fuel ratios in the range of 2.5–2.9 corresponding to combustion chamber pressures of 1.68–2.46 MPa. Variations in temperature and H₂O partial pressure at the nozzle outlet were determined adopting TDLAS based on H₂O absorption near 2.5 μm. Three H₂O absorption lines at 4029.5, 4030.6 and 4030.7 cm⁻¹ were simultaneously measured using only one diode laser at 2.0 kHz repetition rate and adopting a scanned-wavelength direct absorption strategy. The airflow velocity at the nozzle outlet was ascertained in two-dimensional numerical simulations. In this manner, the time-resolved fuel mass flow rate participating in combustion can be derived from the ideal state equation. A detailed discussion of the measurement uncertainty was provided herein considering the influence from determination of temperature, H₂O partial pressure and velocity. The effectiveness of the novel method was validated by comparing its results with that acquired with the traditional weight-loss technique. Finally, it is initially analyzed that the combustion efficiency of pure paraffin fuel gradually increases during the combustion process according to the measurement results.

提出了一种基于可调谐二极管激光吸收光谱(TDLAS)的混合火箭发动机时间分辨燃料质量流量的非侵入式测定方法。目前的工作在实验室规模的混合火箭发动机中使用氧气/石蜡作为推进剂进行了实验测试，使用 2.5-2.9 范围内的氧化剂与燃料比，对应于 1.68-2.46 MPa 的燃烧室压力。采用TDLAS基于2.5μm附近的H ₂ O吸收来确定喷嘴出口处温度和H ₂ O分压的变化。在 4029.5、4030.6 和 4030.7 cm ^-1处的三个 H ₂ O 吸收谱线仅使用一个二极管激光器以 2.0 kHz 重复率同时测量，并采用扫描波长直接吸收策略。在二维数值模拟中确定喷嘴出口处的气流速度。以这种方式，参与燃烧的时间分辨燃料质量流量可以从理想状态方程导出。考虑到温度、H ₂测定的影响，本文详细讨论了测量不确定度O 分压和速度。通过将其结果与使用传统减肥技术获得的结果进行比较，验证了新方法的有效性。最后根据测量结果初步分析纯石蜡燃料在燃烧过程中的燃烧效率逐渐提高。