本文是利用GRI-Mech 3.0甲烷化學反應機構及ESI-CFD v.2004數值方法對交互作用下的噴流火焰組進行一系列有關火焰當量比、火焰間距與火焰穩定的機制之定性與定量研究。經由改變火焰間距及火焰組數之定性觀察與現象分析，本文提出一套有關火焰交互作用下其延伸貧油火焰穩定之機制，並且配合相關火焰外型、長度的拍照、熱電偶測溫、流場雷射實驗量測所得之定量化數據，以驗證數值計算之結果。
雙噴流火焰在間距（L）槽寬（d）比移近到小於四倍以下（L/d < 4）時，開始產生外觀上相互推擠的交互作用，本文利用數值方法仔細分析其間流場、溫度場及化學物質之分合及運動，探討火焰如何作交互作用及對穩定機制之貢獻。兩噴嘴間的流場由四倍槽寬間距（L = 4d）的引導流，轉移成三倍槽寬間距（L = 3d）的局部渦流場，及最後成形兩倍槽寬間距（L = 2d）的全面迴流，且側向對衝流場強度由輕微、明顯、到激烈，隨噴嘴槽寬間距比的縮小而逐步加強。兩倍槽寬間距（L = 2d）的條件下，兩噴嘴間全面迴流的流場是由於下游強烈的對衝流場且形成停滯點，造成火焰排出的後火焰無法完全由下游宣洩，且向上游回堵，一支向上，另一支向下所造成的。同時燃燒的熱量也不易有效順暢地隨流場快速排出，只能向側面已轉彎的流場上游傳導造成火焰向上游延燒，形成有側移傾角的火焰外觀。對衝流場可以同時降低噴嘴出口的流速及後火焰的流速，降低流埸帶走熱量的速度，加上對稱軸原有的熱保溫效果，後火焰可以有較多的熱量向上游回傳，增加燃燒速度。更有利於波速較慢的貧油火焰波向上游趕上流場，降低可操作的貧油當量比的下限值。全面迴流為火焰基部帶來了延續燃燒所需要的溫度，並與噴嘴形成搜集化學中間產物的機構，加強火焰基部與噴嘴槽的貼著能力。
固定為兩倍槽寬間距、當量比φ = 0.88 / 0.3 / 0.88的三噴流火焰組是不對稱的側向對衝火焰組。兩噴嘴間對衝的流場由φ = 0.88 / 0.7 / 0.88的全面迴流減弱為φ = 0.88 / 0.3 / 0.88的渦流場，側向對衝的停滯點由兩噴嘴間的中間位置往中間φ=0.3的弱火焰方向退縮。中間火焰的後火焰漸漸微弱，側向對衝的角色逐漸由中間噴嘴的未燃氣來代為執行。停滯點下游部份的外側後火焰流速比較快，以黏滯力拉著中間火焰的後火焰，使其加快脫離火焰面往下游流動。這是一種加速對流的效果，並不利於中間後火焰熱量的保持，會明顯降低火焰燃燒溫度。且由於火焰厚度的拉大，沿流線方向的溫度梯度減緩，降低向上游的熱傳導的能力。中間火焰的未燃氣雖然無法充分的由自己的後火焰來加熱，但由外側火焰提供的大量且高溫的後火焰是可靠且有效的熱量來源。對中間火焰而言，化學中間產物的穩駐機構可分為火焰基部及主火焰兩部份:中間火焰的基部可直接由側面吸收外側火焰的熱量及化學中間產物，做正壓式側向對衝燃燒。而中間火焰的主火焰是一種沿著等溫線的階梯式燃燒，由側面吸收外側後火焰的熱量，第一個階梯式燃燒是利用本火焰基部的化學中間產物，之後的階梯式燃燒，有互相做化學中間產物交換的機構，是一種跨流線的燃燒，也是一種為負壓式側向對衝燃燒。
交互作用次極限貧油火焰的研究受限於並存的高低溫燃燒，強烈對比造成光學量測的困難，至今所知有限。數值分析是目前最有效的方法之一，且有助於新實驗方法的設計。
本文成功的解析了貧油、超貧油交互作用噴流火焰燃燒的穩駐特性以及其燃燒過程中重要化學步驟，對噴流火焰組的實際應用以及燃燒器的設計將有莫大的幫助。

This study aims to investigate interactive parallel lean and sub-limit lean premixed methane-air flames issued from two or three rectangular slot burners with variable jet spacing, equivalence ratio and burner exit speed. The twin-jet flames consist of two identical slot flames which are called symmetrical interactive flames. The triple-jet flames, with a same jet spacing, consist of two identical slot flames in outboard side on lean combustion and one center flame on sub-limit lean combustion in the center. The outboard and center jet flames form non-symmetrical interactive flames. The flowfield and combustion chemical reactions are predicted by detailed numerical simulation with Skeletal and GRI–Mech 3.0 reaction mechanisms. Numerical results such as velocity streamlines, temperature, flame height and flame shape are validated with those obtained by experimental particle image velocimetry (PIV) and flame measurements. When moved closer beyond a threshold jet spacing, twin-jet flames become interactive and both flames tilt outward in appearance. This symmetrical flame interaction provides a wider operation range. Numerical predictions found that there are three different interactive flow fields: entrainment, recirculation and reverse flows according to jet-to-jet spacing. At the reverse flow stage, a stagnating flowfield termed lateral impingement is generated along the symmetrical axis between the flames, which is similar but not identical to that found in the counterflow flames. Regardless of the extent of flame interaction or the degrees of flame tilting angle, the interacting postflame flowfield creates a restriction to slow down itself, reduces the convective heat to the down stream and increases the conductive heat transfer to the upstream unburned mixture. This is the main mechanism to enhance the flame stabilization, especially in lean conditions. The stabilization mechanism of the interactive twin-jet flames is also enhanced by other crucial factors such as low dissipation of heat, inter-change of chemical species between two flames, and import chemical species from main flame to burner rim.
In contrast to the twin-jet flames, the triple flames, with jet spacing L/d = 2 and equivalence ratio of φ = 0.88 outboard and φ = 0.7 ~ 0.3 for inboard flame, can be classified as a non-symmetrical lateral impingement. The interactive postflame consists of one weak flow in the center and one strong flow in the outside. The interactive thermal field also combines one hot flow and one cold flow. It is verified that the sub-limit lean center flame is mainly sustained by the hot products of outboard lean flames. The strong outboard postflame twists the flow direction of center postflame in a sharp angel to the flame sheet. Usually the flow direction is nearly normal to the flame sheet. This twisted flame is called cascade flame. The cascade flame accommodates the slow flame speed of the sub-limit mixture, extents the residence time and allows the chemical species to perform the cross streamline combustion. The cascade flame is a kind of negative lateral impinged flame. The center flame base is supported by the outboard flame with the same method as the twin-jet flames. This sub-limit lean flame is mainly burnt through the path of HO2 / CH3O with branching reaction step of O2 + H-> O + OH. The experimental study of sub-limit lean combustion is difficult to conduct due to the strong contrast ratio between two non-symmetrical flames. Thus, the current numerical method is one of the feasible methods to study the sub-limit lean combustion.

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