發(fā)布時間：2018-05-05 23:56

  本文選題：火溢流 + 腔室火　； 參考：《中國科學技術(shù)大學》2016年博士論文

【摘要】：開口火溢流是腔室火中一種常見且極為重要的燃燒現(xiàn)象。通風狀況在火溢流的形成及蔓延進程中扮演了重要角色。以往研究均主要針對無風下單開口腔室場景,對其他復雜無風及有風場景則鮮有涉及。本文對無風下單開口及雙開口以及側(cè)向風作用下的雙開口火溢流的形成及燃燒動力學進行了系統(tǒng)理論研究,分析了雙開口及側(cè)向風的影響機制；采用燃燒風洞及小尺度腔室火溢流實驗臺,模擬了不同風速下對稱雙開口火溢流場景,對其燃燒機理及動力學參數(shù)開展了系統(tǒng)研究。研究結(jié)果綜述如下：對于無風下的單開口腔室火溢流場景,燃料供應速率及腔室溫度的升高會造成中性面的降低�；诎敕鍖挼母咚狗植己瘮�(shù)揭示了徑向溫度的軸對稱高斯自相似分布規(guī)律,實驗數(shù)據(jù)與文獻數(shù)據(jù)較好符合�；谛拚齔ukoski數(shù)和長度因子揭示了無風下單開口火溢流軸向溫度與火焰高度的自相似分布規(guī)律。在連續(xù)火焰區(qū)、間歇火焰區(qū)及浮力羽流區(qū),火溢流的軸向溫度自相似分布函數(shù)具有與經(jīng)典羽流一致的冪指數(shù)。隨著過余熱釋放速率增加,火溢流逐漸由墻面火向軸對稱火焰轉(zhuǎn)變,在墻面火焰區(qū)火焰高度自相似分布函數(shù)的冪指數(shù)與經(jīng)典羽流不同,壁面附近空氣卷吸受限可能是主要原因。無風條件下,相比于單開口情形,雙開口的存在會使腔室的中性面升高,并對腔室火溫度產(chǎn)生影響�；诶碚撏茖Й@得了無風下非對稱雙開口火溢流的中性面高度模型,與文獻中數(shù)據(jù)符合較好。側(cè)向風的加入,會因補充氧氣促進燃燒,也可冷卻可燃物,這兩種效應會相互競爭,從而對腔室燃燒強度和室內(nèi)溫度產(chǎn)生影響。理論推導表明,側(cè)向風對對稱雙開口的腔室火溢流壓差分布產(chǎn)生三種影響,即直接在順風及逆風沿的腔室開口施加風壓：造成靜壓變化：造成流體靜壓變化。側(cè)向風的作用還會造成小尺度對稱雙開口腔室火溢流順風沿和逆風沿中性面升高及降低,并影響火溢流的流態(tài)及流動方向。以上推導的結(jié)論均與實驗數(shù)據(jù)一致。不同側(cè)向風風速下的實驗數(shù)據(jù)表明,采用半峰寬(FWHM)作為歸一化變量的無量綱高斯函數(shù)可以較好地擬合不同風速下的徑向溫度數(shù)據(jù),不會因不同風速造成的軸線軌跡彎曲而變化。側(cè)向風作用會使火溢流軸線軌跡形成初始階段的脫離壁面區(qū)域和隨后的附著壁面區(qū)域：半峰寬(FWHM)沿高度方向上呈弱線性分布。側(cè)向風風速1.5 m/s及3 m/s的實驗數(shù)據(jù)表明,耦合側(cè)向風的無量綱模型及長度因子可以較好地對不同側(cè)向風風速、開口尺寸和內(nèi)部燃燒強度下的火溢流軸向溫度及壁面總熱通量進行擬合。在連續(xù)火焰區(qū)、間歇火焰區(qū)及浮力羽流區(qū),火溢流軸向溫度自相似分布函數(shù)具有與經(jīng)典羽流一致的冪指數(shù)：風速增加會使得二個火焰分區(qū)之間的轉(zhuǎn)化加快,空氣卷吸增強是主要原因。側(cè)向風作用造成的中性面高度下降會增強火溢流的近場及遠場空氣卷吸；外立面的空氣卷吸受限也會對火溢流的溫度分布及軸線軌跡產(chǎn)生顯著的影響。不同風速下的數(shù)據(jù)表明,側(cè)向風的作用會對壁面總熱通量及溫度產(chǎn)生兩個相互競爭的作用,使其隨著風速增加出現(xiàn)非線性變化趨勢。
[Abstract]:Open fire overflow is a common and extremely important combustion phenomenon in the chamber fire. Ventilation has played an important role in the formation and spread of the fire overflow. Previous studies were mainly aimed at the single opening of the oral chamber scene without wind, and rarely involved in other complicated and windless scenes. The formation of double opening fire overflow and combustion dynamics under side wind are systematically studied, and the influence mechanism of double opening and lateral wind is analyzed. The flow field of symmetrical double opening under different wind speeds is simulated by combustion wind tunnel and small scale chamber fire overflow test platform, and its combustion mechanism and dynamic parameters are carried out. The research results are summarized as follows: for a single open oral chamber fire overflow scene without wind, the fuel supply rate and the increase of the chamber temperature will result in the reduction of the neutral surface. The Gauss distribution function based on the half peak width reveals the axisymmetric Gauss self similarity distribution of the radial temperature, and the experimental data are in good agreement with the literature data. Based on the modified Zukoski number and the length factor, the self similar distribution of the axial temperature and the flame height of a single open fire overflow is revealed. In the continuous flame region, the intermittent flame region and the buoyancy plume, the self similar distribution function of the axial temperature of the fire overflow has the power exponent consistent with the classical plume. With the increase of the rate of excess heat release, The fire overflow gradually changes from the wall fire to the axisymmetric flame. The power exponent of the self similar distribution function of the flame height in the wall flame area is different from that of the classical plume. The air entrainment near the wall may be the main reason. Under the condition of no wind, the double opening will increase the neutral surface of the chamber and the chamber fire temperature. Based on the theoretical deduction, the neutral surface height model of unsymmetrical double opening fire overflow is obtained, which is in good agreement with the data in the literature. The addition of the side wind will increase the combustion and can cool the combustibles. These two effects will compete with each other, thus influencing the chamber combustion strength and indoor temperature. The derivation shows that the lateral wind has three effects on the distribution of the pressure difference distribution in the chamber with symmetrical double opening, that is, the wind pressure is applied directly to the opening of the chamber with the wind and the opposite wind, which causes the static pressure change: the hydrostatic pressure changes. The lateral wind will also cause the small scale symmetrical double opening chamber fire overflow along the wind and the counter wind to rise along the neutral surface. The above conclusions are all consistent with the experimental data. The experimental data under different lateral wind speeds show that the dimensionless Gauss function using half peak width (FWHM) as a normalized variable can well fit the radial temperature data under different wind speeds and will not be caused by different wind speeds. The axis trajectory of the axis changes. The lateral wind can cause the fire overflow axis to form the initial stage of the separation from the wall area and the subsequent attachment wall area: the half peak width (FWHM) is a weak linear distribution along the direction of height. The experimental data of 1.5 m/s and 3 m/s for the lateral wind wind speed show that the dimensionless model and length factor of the wind in the coupling side In the continuous flame region, the intermittent flame area and the buoyancy plume region, the self similar distribution function of the fire overflow axial temperature is consistent with the classical plume in the continuous flame region, the intermittent flame area and the buoyancy plume region. The increase of wind speed will make the wind speed increase two. The main reason for the conversion between the flame zones is that the air entrainment is the main reason. The decrease of the neutral surface caused by the lateral wind effect will enhance the near and far field air entrainment of the fire overflow; the air entrainment limitation of the outer surface will also have a significant effect on the temperature distribution and axis trajectory of the fire overflow. The effect of wind on the total heat flux and temperature of the wall has two competing effects, making it nonlinear trend with the increase of wind speed.

【學位授予單位】：中國科學技術(shù)大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：X932

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