直到耗散尺度的湍流與復(fù)雜化學(xué)相互作用數(shù)值模擬研究
發(fā)布時間:2018-06-18 17:19
本文選題:火災(zāi) + 一維湍流模型; 參考:《中國科學(xué)技術(shù)大學(xué)》2013年博士論文
【摘要】:實際火災(zāi)是湍流燃燒過程,而在湍流燃燒中湍流流動與復(fù)雜化學(xué)是時空多尺度耦合作用的。研究湍流與復(fù)雜化學(xué)的相互作用是一項既有挑戰(zhàn)也十分有意義的課題。湍流的空間尺度可以分為含能尺度、慣性子區(qū)尺度和耗散尺度三個層次。湍流渦旋從最小的耗散尺度開始就與火焰有著強烈的相互作用。 數(shù)值模擬研究湍流與復(fù)雜化學(xué)的相互作用需要解決耦合詳細(xì)化學(xué)反應(yīng)機理的耗散尺度湍流反應(yīng)流模擬,和海量模擬結(jié)果診斷分析的兩個難題。本文采用一維湍流模型(one-dimensional turbulence, ODT)和化學(xué)反應(yīng)爆炸模式分析方法(chemical explosive mode analysis, CEMA)解決了這兩個難題,建立了ODT+CEMA分析湍流與復(fù)雜化學(xué)相互作用的數(shù)值分析平臺,并對典型滅火劑與氫氣射流火焰的相互作用進行了數(shù)值模擬和深入分析。 復(fù)雜化學(xué)研究中,詳細(xì)化學(xué)反應(yīng)機理的分析及簡化對實現(xiàn)湍流耦合復(fù)雜化學(xué)的數(shù)值模擬十分重要。本文中采用關(guān)系圖法對典型碳?xì)淙剂戏磻?yīng)機理進行了簡化研究。不但研究了在保持一定計算精度情況下簡化機理能達到的最小規(guī)模,還深入分析了方法參數(shù)對簡化結(jié)果的影響,并且引入強關(guān)系組分群的概念,分析了復(fù)雜化學(xué)反應(yīng)機理中強關(guān)系組分群的聚集、分布情況。為了加快反應(yīng)機理的計算,本文還做了利用圖形顯卡并行計算求解大型化學(xué)反應(yīng)機理的研究,在大型機理情況下計算加速效果明顯。 一維湍流模型ODT,可以實現(xiàn)耦合復(fù)雜化學(xué)的耗散尺度湍流反應(yīng)流模擬。本文介紹了ODT模型的計算框架、湍流模擬機制和數(shù)值求解方法。并用此方法模擬分析了氫氣射流火焰,以及添加典型滅火劑后的射流火焰基本特性。 高精度的湍流反應(yīng)流模擬會產(chǎn)生海量的計算數(shù)據(jù),傳統(tǒng)采用典型系統(tǒng)參數(shù)如溫度、關(guān)鍵組分的濃度,甚至一階導(dǎo)數(shù)的分析方法已經(jīng)不適合處理如此龐大、精細(xì)的計算結(jié)果;瘜W(xué)反應(yīng)爆炸模式分析方法是一種分析湍流反應(yīng)流局部系統(tǒng)特征值的方法。本文系統(tǒng)介紹了化學(xué)反應(yīng)爆炸模式分析方法的數(shù)學(xué)基礎(chǔ)和基于ODT模擬數(shù)據(jù)的湍流反應(yīng)流信息分析方法。 通過對添加滅火劑的氫氣空氣預(yù)混熱自燃模型的化學(xué)反應(yīng)爆炸模式分析發(fā)現(xiàn),系統(tǒng)反應(yīng)進行最劇烈的時候也是最大正特征值發(fā)生明顯變化的時刻。添加了滅火劑后,熱自燃時間不但明顯推遲,其反應(yīng)進程和最大正特征值的突變性更加明顯;瘜W(xué)反應(yīng)爆炸模式分析可以直觀的觀察到湍流反應(yīng)流局部系統(tǒng)狀態(tài)的變化,對診斷湍流火焰中的熱自燃、熄火、重燃等行為十分有效。 局部Damkohler數(shù)是控制火焰結(jié)構(gòu),研究湍流與復(fù)雜化學(xué)相互作用的重要參數(shù)。在本文分析中重新定義了Damkohler數(shù)。通過分析湍流火焰在新Da數(shù)空間的散點分布發(fā)現(xiàn):新定義的Da數(shù)是判定局部熄火的良好標(biāo)準(zhǔn),而滅火劑的作用途徑主要是通過增大局部反應(yīng)系統(tǒng)的熱自燃時間,進而減小Da數(shù),增加熄火概率。 通過分析,本文還解釋了Re數(shù)增加時滅火劑滅火效果增加的原因。研究結(jié)果明確指出了主要組分和主要基元反應(yīng)在射流火焰中的作用區(qū)域,以及在火焰抑制效果不同時,火焰中心區(qū)域主要作用組分和基元反應(yīng)的差異。 本文的主要創(chuàng)新點和貢獻在于:為研究湍流與復(fù)雜化學(xué)相互作用,建立了ODT+CEMA的數(shù)值分析平臺,提供了一種分析湍流與復(fù)雜化學(xué)相互作用的新方法。
[Abstract]:The real fire is a turbulent combustion process , and the turbulent flow and complex chemistry in turbulent combustion are both time - space and multi - scale coupling . The research on the interaction between turbulence and complex chemistry is an important subject . The spatial scale of turbulence can be divided into three levels including energy scale , inertial sub - zone scale and dissipation scale . The turbulent vortex has strong interaction with the flame from the minimum dissipation scale .
Numerical simulation of the interaction between turbulent and complex chemistry needs to solve the two difficult problems of the dissipation scale turbulent flow simulation of coupled detailed chemical reaction mechanism and the diagnosis and analysis of massive simulation results . The two problems are solved by using one - dimensional turbulent model ( odt ) and chemical reaction explosion pattern analysis ( CEMA ) . The numerical analysis platform for analyzing the interaction of turbulence and complex chemical interaction is established . The interaction between typical fire extinguishing agent and hydrogen jet flame is simulated and analyzed in depth .
In the study of complex chemistry , the analysis and simplification of the mechanism of chemical reaction are very important to realize the numerical simulation of the complex chemistry of turbulent coupling .
The dissipation scale turbulent flow simulation of coupled complex chemistry can be realized by one - dimensional turbulent model . The calculation framework , turbulence simulation mechanism and numerical solution method of the odt model are introduced in this paper , and the basic characteristics of the jet flame after the typical fire extinguishing agent are added are simulated by this method .
High - precision turbulent reaction flow simulation results in massive computational data . Traditional system parameters such as temperature , concentration of key components , and even first derivative analysis method are not suitable to deal with such a large and fine calculation result . The chemical reaction explosion pattern analysis method is a method for analyzing the characteristic value of local system of turbulent flow reaction flow . The system introduces the mathematical basis of chemical reaction explosion pattern analysis method and the turbulence reaction flow information analysis method based on the odt simulation data .
By the chemical reaction explosion mode analysis of the hydrogen air pre - mixing self - ignition model to add the fire extinguishing agent , it is found that the most violent time is the time when the maximum positive characteristic value changes obviously . After the fire extinguishing agent is added , the heat self - ignition time is obviously delayed , and the reaction progress and the maximum positive characteristic value are more obvious . The chemical reaction explosion mode analysis can visually observe the change of the local system state of the turbulent flow reaction flow , and is very effective for diagnosing the heat self - ignition , extinguishing , reburning and the like in the turbulent flame .
The local Damkohler number is an important parameter for controlling the flame structure and studying the interaction between turbulence and complex chemical . In this paper , we redefine the Damkohler number . By analyzing the distribution of turbulent flame in the new Da number space , it is found that the Da number newly defined is a good standard for judging local extinguishment , and the action way of the fire extinguishing agent is mainly by increasing the heat self - ignition time of the local reaction system , thus reducing the Da number and increasing the extinction probability .
Through the analysis , this paper also explains the reason for the increase of the extinguishing effect of the fire extinguishing agent when Re number is increased . The results clearly show that the main components and main elements react in the jet flame , and the difference of the main components and elementary reactions in the central zone of the flame is not the same as the flame suppression effect .
The main innovation points and contributions of this paper are : To study the interaction between turbulence and complex chemistry , a numerical analysis platform for the odt + CEMA is established , and a new method for analyzing the interaction between turbulence and complex chemistry is provided .
【學(xué)位授予單位】:中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】:博士
【學(xué)位授予年份】:2013
【分類號】:O643.21;TU998.1
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