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Combustion characteristics of the end burning hybrid rockets in laminar flow

机译：层流末端燃烧混合火箭的燃烧特性

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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.
机译：在这项研究中，我们的目的是弄清在狭窄的固体燃料管道中，相对的层流中火焰蔓延的喷射机理。为了阐明这种机制，我们进行了两个实验。首先，我们观察了在各种氧气速度，环境压力和端口直径下火焰扩散速率的变化。为了使火焰在层流中扩散，可以根据对流的强度将燃烧模式分为3种不同的状态，即化学状态，热状态和稳定状态。该结果与湍流的结果一致。在稳定状态下，尽管氧气速度，淬灭距离几乎恒定。为了研究环境压力和燃料的进气口直径对泄放极限的影响，观察了过渡氧气速度。结果，过渡氧气速度与环境压力和端口直径的对数成正比。尽管存在流动条件，该关系仍然适用。此外，我们计算了燃料表面的速度梯度，以揭示层流中吹扫极限的决定因素。因此，被认为是支配层流中流动分离的速度梯度将不是恒定的。这是因为不能仅通过假设哈根-泊瓦伊流来估计燃料表面的速度梯度，而应包括其他参数，例如蒸发的燃料气体和通过浮力进行的自然对流。

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