本文選題：射流擴(kuò)散火焰 + 燃燒效率��； 參考：《中國(guó)科學(xué)技術(shù)大學(xué)》2014年博士論文

【摘要】：隨著人類(lèi)在高原、高空環(huán)境活動(dòng)的增多,低壓下火災(zāi)為人類(lèi)帶來(lái)了新的問(wèn)題和挑戰(zhàn)。發(fā)展高原和高空環(huán)境下火災(zāi)的防治技術(shù)顯得越來(lái)越重要,因此研究低壓下火災(zāi)燃燒特性具有重要的現(xiàn)實(shí)意義。根據(jù)前人的研究發(fā)現(xiàn),對(duì)于火災(zāi)燃燒條件來(lái)說(shuō),低氣壓環(huán)境區(qū)別于正常大氣環(huán)境的最大不同就是空氣密度和氧氣分壓的減小。不同壓力下空氣密度和氧氣分壓的改變,分別直接導(dǎo)致了浮力作用和碳黑產(chǎn)生量的不同。浮力和火焰抖動(dòng)、火焰形態(tài)等息息相關(guān),一般用弗勞德數(shù)表征浮力對(duì)火焰作用的大小。而碳黑與燃燒效率、火焰形態(tài)、產(chǎn)煙傾向等有關(guān)。因此自然地確定浮力和碳黑作為研究低壓對(duì)火災(zāi)燃燒作用的途徑,并選取在不同壓力下有著相等質(zhì)量損失速率的氣體燃料作為研究對(duì)象。 低氣壓環(huán)境的實(shí)現(xiàn)主要有高海拔現(xiàn)場(chǎng)自然環(huán)境和低壓艙人工模擬環(huán)境兩種方式。現(xiàn)場(chǎng)自然環(huán)境實(shí)驗(yàn)雖然花費(fèi)大開(kāi)展難,但是它適合開(kāi)展大尺度的火災(zāi)燃燒實(shí)驗(yàn),特別適合用來(lái)發(fā)現(xiàn)不同氣壓下火災(zāi)宏觀現(xiàn)象的不同,因此在拉薩和合肥兩地分別搭建了小型錐形量熱儀進(jìn)行實(shí)驗(yàn),主要用氣體分析儀測(cè)量排煙管道內(nèi)的燃燒產(chǎn)物、熱電偶樹(shù)測(cè)量火焰羽流溫度、輻射計(jì)測(cè)量火焰對(duì)周?chē)妮椛錈崃�、光學(xué)煙密度計(jì)測(cè)量煙氣的消光系數(shù),并使用簡(jiǎn)化的化學(xué)量熱法計(jì)算熱釋放速率。在揭示不同海拔高度火災(zāi)宏觀現(xiàn)象的基礎(chǔ)上,在低壓艙內(nèi)開(kāi)展多級(jí)低壓條件下適于研究燃燒機(jī)理的多種實(shí)驗(yàn)。實(shí)驗(yàn)中,主要采用不加裝濾光片的相機(jī)測(cè)量發(fā)光火焰形狀、加裝CH濾光片的相機(jī)嘗試獲取化學(xué)當(dāng)量比火焰形狀,采用高速相機(jī)和快速傅里葉變換先后拍攝火焰抖動(dòng)過(guò)程和計(jì)算火焰抖動(dòng)頻率。 在拉薩和合肥兩個(gè)海拔高度上,通過(guò)錐形量熱儀測(cè)量甲烷、乙炔和丙烷的熱釋放速率和輻射熱流等參數(shù),進(jìn)一步揭示和明確了低氣壓對(duì)燃燒效率和輻射分?jǐn)?shù)等主要參數(shù)的影響。通過(guò)總結(jié)不同含碳量燃料的類(lèi)似結(jié)果,可以表明：低壓下火焰的熱釋放速率和燃燒效率更高；低壓下火焰總羽流溫度更高；低壓下火焰輻射熱流和輻射分?jǐn)?shù)更�。坏蛪合禄鹧娈a(chǎn)生煙氣的透射率更大,說(shuō)明低壓下火焰的產(chǎn)煙率更小 在低壓艙內(nèi)通過(guò)實(shí)驗(yàn)研究了多個(gè)等級(jí)低壓下甲烷、乙烯和丙烷擴(kuò)散火焰抖動(dòng)行為,主要是研究火焰抖動(dòng)頻率和壓力之間的關(guān)系以及出口速度對(duì)抖動(dòng)頻率的影響。主要發(fā)現(xiàn)總結(jié)如下：層流擴(kuò)散火焰抖動(dòng)行為可以分為頂部抖動(dòng)、間歇抖動(dòng)、和連續(xù)抖動(dòng)3個(gè)區(qū)域,連續(xù)抖動(dòng)發(fā)生在較大燃料流量或較大壓力下；抖動(dòng)頻率對(duì)燃料流量和類(lèi)型不敏感,隨流量的增加只略微增加,相同實(shí)驗(yàn)壓力下3種燃料火焰的抖動(dòng)頻率幾乎相等；抖動(dòng)頻率隨壓力升高而增大,實(shí)驗(yàn)壓力范圍內(nèi)從8Hz增加到12Hz,測(cè)量的抖動(dòng)頻率隨壓力增加的0.27次冪而增大；另外,在一些條件下觀察到了丙烷火焰存在多重頻率現(xiàn)象。 在低壓艙內(nèi)測(cè)量了0.03到O.1MPa壓力范圍內(nèi),不發(fā)煙甲烷、乙烯和丙烷穩(wěn)定火焰的發(fā)光形狀,經(jīng)過(guò)對(duì)高度和寬度使用無(wú)量綱數(shù)縮放分析,得到了如下結(jié)論：Reynolds數(shù)線性縮放模型對(duì)烴類(lèi)燃料基本適用,在不同的Re數(shù)下浮力和碳黑的共同作用使得線性關(guān)系的斜率發(fā)生了輕微變化；在最大的Fr數(shù)或最低壓力下,浮力對(duì)火焰高度的影響不重要,相反,在最小Fr數(shù)區(qū)域,浮力對(duì)火焰高度作用占主導(dǎo)地位；在對(duì)火焰寬度進(jìn)行Froude數(shù)縮放時(shí),發(fā)現(xiàn)歸一化火焰寬度和Froude數(shù)存在著很好的線性關(guān)系。 在低壓艙測(cè)量了多級(jí)壓力下,不發(fā)煙甲烷、乙烯和丙烷穩(wěn)定火焰的發(fā)光形狀,特別為甲烷火焰進(jìn)行了0.2個(gè)大氣壓的實(shí)驗(yàn),發(fā)光火焰高度和寬度隨壓力的變化規(guī)律總結(jié)如下：第一種情形,對(duì)于較大燃料流量和較高壓力范圍條件,火焰高度呈現(xiàn)“先增后減”趨勢(shì)；第二種情形,在較小流量和較低壓力范圍內(nèi),可總結(jié)出“先減后增”趨勢(shì)。第三種情形,在合適的燃料流量和壓力范圍下,火焰高度會(huì)呈現(xiàn)“先減后增再減”趨勢(shì)。 在低壓艙內(nèi)進(jìn)行了乙炔層流射流擴(kuò)散火焰煙點(diǎn)實(shí)驗(yàn),實(shí)驗(yàn)壓力范圍為0.03～0.1MPa。利用建立的反應(yīng)射流中心線速度變化模型對(duì)實(shí)驗(yàn)結(jié)果進(jìn)行深入分析,發(fā)現(xiàn)煙點(diǎn)火焰高度、燃料質(zhì)量流量、存留時(shí)間和壓力之間存在如下關(guān)系：低壓下乙炔煙點(diǎn)火焰高度隨壓力升高而減小,這個(gè)變化趨勢(shì)與高壓下乙烯和甲烷火焰的變化規(guī)律相同；煙點(diǎn)燃料質(zhì)量流量隨壓力的冪指數(shù)變化,冪指數(shù)為負(fù)值,與先前多數(shù)實(shí)驗(yàn)結(jié)果一致；在一個(gè)很大的壓力范圍(0.03MPa到1.6MPa)內(nèi),煙點(diǎn)火焰存留時(shí)間隨壓力升高而減小。
[Abstract]:With the increase of human being in high altitude and high altitude environment , the fire at low pressure brings new problems and challenges to mankind . It is important to study the fire control technology in high altitude and high altitude environment .

In this paper , a large scale fire combustion experiment is carried out in a low - pressure chamber , which is suitable for the investigation of the combustion mechanism in the low - pressure chamber .

The effects of low air pressure on combustion efficiency and radiation fraction have been further revealed and clarified by measuring the heat release rate and radiant heat flux of methane , acetylene and propane at two altitudes of Lhasa and Hefei . By summarizing the similar results of different carbon content fuels , it is shown that the heat release rate and combustion efficiency of flame at low pressure are higher .
the flame total plume temperature at low pressure is higher ;
the heat flow and the radiation fraction of the flame radiation at low pressure are smaller ;
The transmissivity of the flue gas generated by the flame at low pressure is larger , which indicates that the smoke production rate of the flame at low pressure is smaller .

In the low - pressure chamber , the flame - shaking behavior of methane , ethylene and propane under low pressure is studied experimentally . It is mainly to study the relationship between flame jitter frequency and pressure and the influence of outlet velocity on the dither frequency . The main findings are as follows : laminar diffusion flame jiggle can be divided into top jitter , intermittent jitter , and continuous jitter , and continuous jitter occurs at large fuel flow or large pressure ;
The dither frequency is insensitive to the fuel flow and the type . With the increase of the flow rate , the dither frequency of the three fuel flames is almost equal under the same experimental pressure ;
The jitter frequency is increased with the increase of pressure , from 8 Hz to 12 Hz in the experimental pressure range , and the measured jitter frequency increases with the increasing pressure of 0.27 power .
In addition , the presence of multiple frequency phenomena in the propane flame was observed under some conditions .

In the low - pressure cabin , the light - emitting shape of the stable flame of methane , ethylene and propane is measured in the range of 0.03 to 0.1 MPa . The results are as follows : The linear scaling model of Reynolds number is basically applicable to hydrocarbon fuels , and the slope of the linear relationship is slightly changed under different Reynolds number linear scaling models .
The influence of buoyancy on flame height is not important at the maximum Fr number or lowest pressure , but in the area of minimum Fr , the buoyancy plays a dominant role in flame height .
There is a good linear relationship between the normalized flame width and Froude number when Froude number scaling is carried out on the flame width .

In the low - pressure tank , the light - emitting shape of non - smoking methane , ethylene and propane - stabilized flame , especially the methane flame , was tested for 0.2 atmospheres , the height and width of the flame - emitting flame were summarized as follows : the first case , for larger fuel flow and higher pressure range , the flame height presented the " first increase and decrease " trend ;
In the second case , the " pre - deceleration " trend can be summarized in a smaller flow rate and a lower pressure range . In the third case , the flame height will exhibit a " pre - and - decrease " trend under appropriate fuel flow and pressure ranges .

In the low - pressure chamber , the experiment of laminar jet diffusion flame of acetylene is carried out . The experimental pressure range is 0.03 ~ 0.1MPa . The experimental results are analyzed in depth by using the established reaction jet center line velocity variation model . It is found that the flame height , mass flow rate , residence time and pressure of the smoke point decrease with increasing pressure , which is the same as that of ethylene and methane flame under high pressure .
The power exponent of flue gas fuel mass flow with pressure changes with a negative value , which is consistent with the previous experimental results .
In a large pressure range ( 0.03 MPa to 1.6 MPa ) , the residence time of the smoke point decreases with increasing pressure .

【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類(lèi)號(hào)】：X932

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本文編號(hào)：1789043