發(fā)布時(shí)間：2018-10-16 13:43

【摘要】：密閉空間內(nèi)層流預(yù)混火焰?zhèn)鞑ナ强扇細(xì)怏w安全、內(nèi)燃機(jī)應(yīng)用和爆轟波理論等領(lǐng)域重要的燃燒科學(xué)與技術(shù)課題。如何有效地預(yù)防可燃?xì)怏w的火災(zāi)爆炸(爆轟)事故,控制其發(fā)展蔓延和減輕事故危害,這些問(wèn)題的解答需要科學(xué)研究作為依據(jù)。而內(nèi)燃機(jī)領(lǐng)域也亟需基礎(chǔ)的火焰?zhèn)鞑?shù)據(jù)和詳細(xì)的化學(xué)反應(yīng)機(jī)理來(lái)建立燃燒模型,以實(shí)現(xiàn)其自身結(jié)構(gòu)的優(yōu)化改進(jìn)和對(duì)替代燃料的性能評(píng)估。因此,為了更加全面地揭示火焰發(fā)生、發(fā)展以及加速突變的本質(zhì)規(guī)律和機(jī)理,深入剖析火焰內(nèi)部反應(yīng)區(qū)結(jié)構(gòu)和物理化學(xué)過(guò)程,并建立綜合完善的化學(xué)動(dòng)力學(xué)模型,同時(shí)也為了積累更多有用的火焰?zhèn)鞑セA(chǔ)數(shù)據(jù),本文利用實(shí)驗(yàn)、理論和數(shù)值模擬手段對(duì)密閉空間內(nèi)典型可燃?xì)怏w層流預(yù)混火焰?zhèn)鞑ソY(jié)構(gòu)形態(tài)、火焰加速和突變動(dòng)力學(xué)、層流火焰速度以及化學(xué)反應(yīng)機(jī)理開(kāi)展了細(xì)致嚴(yán)謹(jǐn)?shù)目茖W(xué)研究。 本文首先對(duì)氫-空氣和丙烷-空氣預(yù)混火焰在封閉管道內(nèi)的傳播特性開(kāi)展研究,內(nèi)容包括火焰和超壓動(dòng)力學(xué)、火焰與誘導(dǎo)流場(chǎng)和壓力波的相互作用等。高速紋影攝像技術(shù)用于捕捉和記錄火焰位置和形態(tài)變化,高精度壓力傳感器用于探測(cè)管道內(nèi)瞬時(shí)的壓力變化特性。實(shí)驗(yàn)結(jié)果表明,封閉管道內(nèi)預(yù)混火焰?zhèn)鞑ソ?jīng)歷了復(fù)雜的形狀變化,呈現(xiàn)出經(jīng)典的或變形的Tulip結(jié)構(gòu),由于受到火焰加速和減速、壁面約束、邊界層效應(yīng)、壓力波效應(yīng)以及火焰誘導(dǎo)流場(chǎng)等影響,火焰裙邊運(yùn)動(dòng)、火焰與壁面接觸點(diǎn)運(yùn)動(dòng)、Tulip尖端運(yùn)動(dòng)和火焰尖端運(yùn)動(dòng)等都表現(xiàn)出明顯的階段性特征,Bychkov模型對(duì)基本運(yùn)動(dòng)參數(shù)(位置和速度)的預(yù)測(cè)并不理想,僅適用于火焰發(fā)展早期。所有工況都觀察到了火焰尖端位置(速度)及壓力脈動(dòng)現(xiàn)象,只是頻率和幅度各有不同。變形Tulip結(jié)構(gòu)并不是封閉管道內(nèi)氫-空氣預(yù)混火焰特有的行為,在化學(xué)計(jì)量比(中=1)附近的預(yù)混丙烷-空氣火焰中也有發(fā)現(xiàn),且Tulip變形過(guò)程中都伴隨著顯著的火焰尖端速度脈動(dòng)。壓力波并不是火焰速度脈動(dòng)及Tulip變形的誘因,但確實(shí)會(huì)起到促進(jìn)作用；而壁面和邊界效應(yīng),楔形擠壓流、水力學(xué)不穩(wěn)定性及火焰誘導(dǎo)流動(dòng)的綜合效應(yīng)可能是主要物理起因。 隨后我們利用圓柱形雙燃燒室實(shí)驗(yàn)臺(tái),結(jié)合高速攝像和紋影技術(shù),對(duì)C2碳?xì)淙剂?主要是乙烷、乙烯和乙炔等)常壓和高壓層流火焰速度開(kāi)展了實(shí)驗(yàn)研究和測(cè)量,并分析了當(dāng)量比、初始?jí)毫腿剂戏肿咏Y(jié)構(gòu)對(duì)火焰?zhèn)鞑サ挠绊�。常壓�?shí)驗(yàn)結(jié)果與權(quán)威文獻(xiàn)數(shù)據(jù)吻合得很好,并對(duì)一些歷史數(shù)據(jù)較少且分散的工況做了補(bǔ)充和驗(yàn)證。對(duì)于不同燃料反應(yīng)體系,二氧化碳稀釋的作用機(jī)制明顯不同。表觀的,二氧化碳會(huì)抑制乙烯火焰以及富燃料乙烷火焰?zhèn)鞑?但對(duì)于乙炔火焰以及貧燃料乙烷火焰幾乎沒(méi)有影響,表明其抑制作用被抵消�？傮w來(lái)說(shuō),USC Mech Ⅱ?qū)恿骰鹧嫠俣鹊亩款A(yù)測(cè)不是很理想(特別是對(duì)高壓火焰),僅能較好地反映火焰速度的變化趨勢(shì)。 本文討論分析了USC MechⅡ模型存在的問(wèn)題和缺陷,進(jìn)而以化學(xué)動(dòng)力學(xué)領(lǐng)域最新的研究成果為基礎(chǔ),借助量子化學(xué)計(jì)算和實(shí)驗(yàn)測(cè)量等手段,建立了新的綜合化學(xué)反應(yīng)模型。實(shí)驗(yàn)驗(yàn)證表明新模型對(duì)常壓和高壓典型可燃?xì)怏w層流預(yù)混火焰速度的預(yù)測(cè)能力相比USC Mech Ⅱ有了顯著的提高。新模型為我們揭示了乙烷、乙烯、乙炔火焰體系的主要反應(yīng)路徑；發(fā)現(xiàn)了碳?xì)淙剂匣鹧娼Y(jié)構(gòu)和燃燒行為之間很多相似之處；同時(shí)還指出了高壓火焰體系中一些重要的基元反應(yīng)以及火焰速度對(duì)反應(yīng)速率常數(shù)的敏感度變化(相比常壓情況)。二氧化碳稀釋對(duì)火焰體系的化學(xué)和第三體效應(yīng),主要表現(xiàn)為抑制和促進(jìn)兩個(gè)矛盾方面。一方面,過(guò)量的C02會(huì)逆轉(zhuǎn)反應(yīng)CO+OH=CO2+H,并增強(qiáng)第三體反應(yīng)H+O2(+M)=HO2導(dǎo)致體系H原子濃度降低；另一方面,作為強(qiáng)第三體,C02稀釋同樣也會(huì)加劇HCO的分解反應(yīng)HCO (+M)=H+CO (+M),從而補(bǔ)償一定的H原子損失。表觀的二氧化碳稀釋效果是這兩種內(nèi)在作用機(jī)制相互競(jìng)爭(zhēng)和抵消的綜合體現(xiàn)。乙炔火焰中由于反應(yīng)CO+OH=CO2+H并不是產(chǎn)物C02主要生成通道,因而其重要性減弱,二氧化碳稀釋的抑制和促進(jìn)作用相互抵消；而乙烯和乙烷火焰速度對(duì)HCO分解反應(yīng)速率常數(shù)的敏感度較低(反應(yīng)重要性較弱,尤其是在高壓下),因此火焰總體受到抑制。特別的,二氧化碳稀釋對(duì)富燃料乙烷火焰體系的化學(xué)和第三體效應(yīng)較弱,體系的熱量和質(zhì)量輸運(yùn)性質(zhì)以及混合物組成和密度的變化是導(dǎo)致火焰減速的本質(zhì)原因。與乙烷和乙烯火焰不同的是,0原子(而不是H原子)在乙炔火焰體系中起著決定性作用,其濃度變化將直接影響火焰?zhèn)鞑バ袨椤?br/>[Abstract]:Laminar premixed flame propagation in confined space is an important topic of combustion science and technology in the fields of combustible gas safety, internal combustion engine application and detonation wave theory. How to effectively prevent the fire explosion (detonation) accident of combustible gas, control its development spread and alleviate the accident hazard, the answer of these questions need scientific research as the basis. In the field of internal combustion engine, it is necessary to establish combustion model based on flame propagation data and detailed chemical reaction mechanism, so as to realize optimization improvement of its own structure and performance evaluation of alternative fuel. Therefore, in order to reveal the essence rule and mechanism of flame generation, development and accelerating mutation more comprehensively, deeply analyze the structure and physical and chemical process of flame interior reaction zone, and establish a comprehensive and perfect chemical kinetic model. At the same time, in order to accumulate more useful flame propagation basic data, this paper uses experiment, theory and numerical simulation to simulate the structure, flame acceleration and mutation dynamics of typical combustible gas laminar premixed flame in confined space. The laminar flame velocity and chemical reaction mechanism have carried out detailed and rigorous scientific research. Firstly, the propagation characteristics of hydrogen-air and propane-air pre-mixed flame in closed pipelines are studied. The contents include flame and overpressure dynamics, flame and induced flow field and pressure wave. The high-precision pressure sensor is used to detect the instantaneous pressure change in the pipeline, and the high-precision pressure sensor is used for capturing and recording flame position and shape change. The experimental results show that the pre-mixing flame propagation in the closed pipeline has undergone a complex shape change, which presents a classical or deformed Tulp structure, which is affected by flame acceleration and deceleration, wall restraint, boundary layer effect, pressure wave effect and flame-induced flow field, etc. The motion, flame and wall contact movement, Tulp tip movement and flame tip movement all show obvious periodic characteristics. The prediction of basic motion parameters (position and velocity) by Bychbach model is not ideal, and it is only suitable for flame development. Earlier, the flame tip position (velocity) and pressure pulsation phenomenon were observed for all operating conditions, except for frequency and amplitude. The deformation of the Tulp structure is not characteristic of the hydrogen-air pre-mixing flame in the closed pipeline, and is also found in the pre-mixed propane-air flame near the stoichiometric ratio (= 1), and there is a significant flame tip speed during the Tulp deformation process. Pulsation. Pressure wave is not the cause of flame velocity fluctuation and Tulp deformation, but does play a promoting role; and the wall surface and boundary effect, wedge-shaped extrusion flow, hydraulic instability and flame-induced flow can be the main physics. Then we carried out experimental research and measurement on C2 hydrocarbon fuel (mainly ethane, ethylene and acetylene, etc.) at normal pressure and high pressure laminar flame speed by using cylindrical double combustion chamber experiment table, combined with high speed camera and image shadow technology. The equivalence ratio, the initial pressure and the molecular structure of the fuel are analyzed. The experimental results of atmospheric pressure are well coincident with authoritative literature data, and some historical data are less and dispersed. Replenishment and verification. For different fuel reaction systems, carbon dioxide dilution works Visible, carbon dioxide suppresses the flame propagation of ethylene and fuel-rich ethane, but has little effect on acetylene flame and lean-fuel ethane flame, indicating its suppression The effect is cancelled. In general, the quantitative prediction of laminar flame velocity by USC Mech II is not ideal (especially for high-pressure flame) and only better reflects flame speed. In this paper, the problems and defects of USC Mech 鈪，

本文編號(hào)：2274543