突扩燃烧室内预混湍流燃烧的数值模拟研究

发布时间：2018-01-24 18:37

本文关键词： 湍流强度预混燃烧当量比大涡模拟　出处：《上海应用技术学院》2015年硕士论文　论文类型：学位论文

【摘要】：湍流是经典物理中尚未解决的问题之一,普遍存在于自然界和应用于实际工程当中,而研究湍流燃烧更是在湍流的基础上增加了难度,因为燃烧的出现使得湍流场更加复杂。湍流燃烧过程的研究是近年来研究的热点和前沿之一,随着社会的进步和科学技术的发展,人们对于环境保护的意识也越来越高,因此对于低排放高效率的燃烧室的研发受到众多研究人员的重视,许多新思路新方法也都应用在燃烧室。本文以某燃气轮机的火焰筒为参数建立三维模型,致力于研究提高燃气涡轮发动机燃烧室的燃烧效率和减少污染物的排放问题,建立了非稳态三维湍流化学反应模型。文中数值模拟的湍流模型为大涡模拟方法(LES),燃烧模型采用有限速率／涡耗散模型(Finite Rate/Eddy Dissipation)。首先计算了燃烧室燃气不同湍流强度条件下燃烧状况,得到燃烧室内的速度场、温度场、各组分浓度场和涡量场的分布情况,研究湍流强度对预混燃烧效率以及一氧化碳(C0)排放量的影响。然后计算了不同当量比的预混燃气对预混燃烧效果的影响,研究了燃烧室的温度场,一氧化碳浓度场,涡量场和压力场的分布,分析预混燃气当量比对预混燃烧效率和一氧化碳生成量的影响。最后使用EMD方法对数值模拟的数据进行了分析,主要对火焰界面、火焰内部或火焰外部三个区域的U、V、T间歇性进行了比较。计算得到的主要结论如下：(1)在预混燃气当量比和入口速度不变的条件下,随着预混燃气入口湍流强度的增大,燃烧室内低温区域逐渐减小,火焰的相对长度随着湍流强度的增大而缩短,燃料更多的在燃烧室内充分的燃烧,提高了能源利用率,节约了能源。湍流强度的增大使得火焰表面的CO的分布区域越来越薄,在燃烧室内的总体分布区域变小,而且高浓度区域也随着湍流强度的增大而减小,为减少C0的生成,可以适当提高预混燃料的湍流强度,减小对环境的污染。(2)预混燃气中的甲烷的含量对燃烧产物温度影响很大,在预混燃料入口速度和湍流强度不变的情况下,燃烧室的最高温度随当量比的增大而明显升高,而且燃烧室的最高温度随当量比的变化呈现出一定的规律性。通过分析在预混燃料不同当量比条件下的燃烧,发现随着当量比的提高,燃烧产生的CO浓度和分布区域增大因此,为减少C0的生成,可以适当减小预混燃料的当量比。(3)发现在火焰界面和火焰内部,当T的局部间歇性振幅较大时,U的局部间歇性频率较高,这说明T波动的活跃程度受到U频率的影响。当U周期越短,T的指数就越不稳定,波动越剧烈,可以理解为当湍流脉动越剧烈时,燃烧反应也会加剧,温度的变化也越大,表现为燃烧效率也会更高。
[Abstract]:Turbulence is one of the unsolved problems in classical physics. It is widely used in nature and applied in practical engineering, and the study of turbulent combustion is more difficult on the basis of turbulence. Turbulent combustion process is one of the hotspots and frontiers in recent years, with the progress of society and the development of science and technology. People are more and more aware of environmental protection, so the research and development of low emission and high efficiency combustor has been paid attention by many researchers. Many new ideas and new methods are also applied to the combustion chamber. In this paper, a three-dimensional model is built based on the flame tube of a gas turbine. To study the problem of improving combustion efficiency and reducing pollutant emission of gas turbine engine combustor. The unsteady three-dimensional turbulent chemical reaction model is established. The turbulent model in this paper is the large eddy simulation method (Les). The combustion model uses finite rate / vortex dissipation model (Finite Rate/Eddy dissipation). Firstly, the combustion conditions of combustor gas with different turbulent intensity are calculated. The distribution of velocity field, temperature field, concentration field and vorticity field in the combustor are obtained. The effect of turbulence intensity on premixed combustion efficiency and carbon monoxide (CO) C0 emission is studied. Then the effect of premixed gas with different equivalent ratio on premixed combustion efficiency is calculated and the temperature field of combustion chamber is studied. The distribution of carbon monoxide concentration field, vorticity field and pressure field, and the effect of premixed gas equivalent ratio on combustion efficiency and carbon monoxide production are analyzed. Finally, the numerical simulation data are analyzed by EMD method. Mainly for the flame interface, the flame inside or outside of the three regions of the UGV. T intermittency is compared. The main conclusions are as follows: 1) under the condition of constant equivalent ratio and inlet velocity of premixed gas, the turbulence intensity increases with the inlet of premixed gas. The low temperature region of the combustion chamber decreases gradually, the relative length of flame decreases with the increase of turbulence intensity, and the fuel is more fully burned in the combustion chamber, which improves the energy efficiency. The increase of turbulence intensity makes the distribution region of CO on the flame surface thinner and smaller in the combustion chamber, and the high concentration region also decreases with the increase of turbulence intensity. In order to reduce the formation of C _ 0, the turbulence intensity of the premixed fuel can be increased appropriately, and the pollution to the environment can be reduced. (2) the content of methane in the premixed gas has a great influence on the combustion product temperature. Under the condition of constant inlet velocity and turbulent intensity of premixed fuel, the maximum temperature of combustion chamber increases obviously with the increase of equivalent ratio. And the maximum temperature of combustion chamber shows certain regularity with the change of equivalent ratio. By analyzing the combustion under different equivalent ratio of premixed fuel, it is found that with the increase of equivalent ratio. Therefore, in order to reduce the formation of C0, the equivalent ratio of premixed fuel can be reduced appropriately. When the local intermittent amplitude of T is larger, the local intermittent frequency of U is higher, which indicates that the active degree of T fluctuation is affected by U frequency. When the U cycle is shorter, the exponent of T is more unstable and the fluctuation is more intense. It can be understood that when the turbulence pulsation is more intense, the combustion reaction will be intensified, and the change of temperature will be greater, and the combustion efficiency will be higher.
【学位授予单位】：上海应用技术学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK16

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