Ignition and extinction in combustion of initially unmixed reactants

[syoukera]

https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/ignition-and-extinction-in-combustion-of-initially-unmixed-reactants/68FEFC2CC55A062CA48743EA24874888

[syoukera]

辻のタイ交流拡散火炎についてのレビュー論文にて、この図のmultiple transitionの引用元

[syoukera]

Abstruct

The adequacy of direct one-step chemical kinetics for describing ignition and extinction in initially unmixed gases is studied through the particular case of inviscid axisymmetric stagnation-point flow. Oxidant is assumed to blow from upstream infinity at a non-gaseous reservoir of pure fuel at its boiling (or sublimating) temperature. Before reaching the reservoir the oxidant reacts with gaseous fuel flowing in the opposite direction to form product and release heat. This heat is in part conducted and diffused to the reservoir interface to transform more fuel into the gaseous state and continue the steady-state burning. Second-order Arrhenius kinetics for Lewis-number unity is examined. A critical parameter characterizing the phenomenon is shown to be the first Damkohler similarity group D1, the ratio of a time characterizing the flow to a time characterizing the chemical activity.

• 初期に混合されていないガスの着火と消炎を表現するのに一段総括反応の妥当性を検討した
• 非粘性の軸対象よどみ点の流れをもちいた
• ルイス数１の二次のアレニウス反応動力学を調査した
• 現象を決定づけるクリティカルなパラメータは一次のダンケラー相似性D1だと示した

For small D1 the reactants convect away heat without releasing the energy stored in their chemical bonds. Regular perturbation about chemically frozen flow establishes this condition as the weak burning limit. For large D1 singular perturbation describes a narrow region of intense chemical activity. For infinite D1 (indefinitely fast rate of reaction) the region is reduced to a surface of discontinuity (the thin-flame kinetics of Burke & Schumann).

small D1

• 化学結合にエネルギーを蓄えたまま熱を輸送する

  large D1

• 特異摂動が化学反応を引きおこす狭い領域を示す

  infinite D1

• 火炎面モデルと同等の非連続な表面につながる

For intermediate D1 numerical techniques establish that a solution describing burning of moderate intensity joins the two previously mentioned asymptotic limits. It is suggested that sudden transition of the system between the various branches in this domain of intermediate D1 accounts for the phenomena of ignition and extinction of burning.

intermediate D1

• ２つの漸近限界を組み合わせた適切な強度での燃焼
• 別の様々な分岐からのシステムの急激な遷移が着火や消炎と対応している

[syoukera]

[syoukera]

4. Axisymmetric geometry

[syoukera]

仮定された渦のシート対称性の不在は、z_x < z < 0の流れに対して、z > 0における非粘性非圧縮軸対象よどみ点流れの鏡像となる事を求める。

azimuthal = 方位角の（水平方向の角度の変異）