Effect of Forced Convection on the Combustion Chemistry of PMMA Spheres in Microgravity

IF 1.3 4区工程技术 Q2 ENGINEERING, AEROSPACE Microgravity Science and Technology Pub Date : 2024-07-13 DOI:10.1007/s12217-024-10128-6

Tatyana Bolshova, Andrey Shmakov, Vladimir Shvartsberg

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Abstract

The influence of the forced convection rate on the chemical structure of a polymethyl methacrylate (PMMA) flame in an oxidizer flow under microgravity conditions was studied using numerical modeling. Gas flow around a solid sphere was simulated using the full Navier–Stokes equations for a multicomponent mixture. A multistep chemical kinetic mechanism was considered in the gas phase. The heat transfer and radiation in both the condensed and gas phases were considered in the modeling. On the PMMA surface, the pyrolysis reaction leading to the transformation of fuel from the condensed phase to the gas phase is specified. The forced convection speed varied in the range from 3 to 20 cm/s. Analysis of CO₂ concentration fields near the burning surface under microgravity conditions showed that the maximum CO₂ concentration is observed in the downstream zone. The width of the flame zone and its chemical structure depend on the intensity of forced convection. The width of the flame against the flow decreases, and the maximum CO concentration increases as the forced convection rate increases. Analysis of the rates of fuel consumption reactions showed that at a low convection speed (v_st=3 cm/s), the reaction with the H radical, which has the highest diffusion coefficient, plays a crucial role in MMA oxidation.

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强制对流对微重力条件下 PMMA 球体燃烧化学性质的影响

利用数值模型研究了微重力条件下氧化剂流中强制对流速率对聚甲基丙烯酸甲酯（PMMA）火焰化学结构的影响。使用多组分混合物的全纳维-斯托克斯方程模拟了固体球体周围的气体流动。考虑了气相中的多步化学动力学机制。建模时考虑了凝结相和气相的传热和辐射。在 PMMA 表面，指定了导致燃料从凝结相转变为气相的热解反应。强制对流速度的变化范围为 3 至 20 厘米/秒。对微重力条件下燃烧表面附近二氧化碳浓度场的分析表明，下游区域的二氧化碳浓度最大。火焰区的宽度及其化学结构取决于强制对流的强度。随着强制对流速率的增加，逆流火焰宽度减小，最大 CO 浓度增加。对燃料消耗反应速率的分析表明，在低对流速度下（vst=3 cm/s），与扩散系数最大的 H 自由基的反应在 MMA 氧化中起着关键作用。

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来源期刊

Microgravity Science and Technology 工程技术-工程：宇航

CiteScore

3.50

自引率

44.40%

发文量

期刊介绍： Microgravity Science and Technology – An International Journal for Microgravity and Space Exploration Related Research is a is a peer-reviewed scientific journal concerned with all topics, experimental as well as theoretical, related to research carried out under conditions of altered gravity. Microgravity Science and Technology publishes papers dealing with studies performed on and prepared for platforms that provide real microgravity conditions (such as drop towers, parabolic flights, sounding rockets, reentry capsules and orbiting platforms), and on ground-based facilities aiming to simulate microgravity conditions on earth (such as levitrons, clinostats, random positioning machines, bed rest facilities, and micro-scale or neutral buoyancy facilities) or providing artificial gravity conditions (such as centrifuges). Data from preparatory tests, hardware and instrumentation developments, lessons learnt as well as theoretical gravity-related considerations are welcome. Included science disciplines with gravity-related topics are: − materials science − fluid mechanics − process engineering − physics − chemistry − heat and mass transfer − gravitational biology − radiation biology − exobiology and astrobiology − human physiology