开口管道煤尘—甲烷预混火焰动力学特性研究

发布时间：2018-04-13 19:00

本文选题：煤尘-甲烷预混燃烧 + 火焰传播结构　；参考：《武汉理工大学》2015年硕士论文

【摘要】：课题通过搭建煤尘-甲烷预混物燃烧火焰特性实验平台,结合高速摄像机、数据采集仪和温度传感器等,测量得到不同条件下煤尘-甲烷预混燃烧火焰传播形态图、传播速度、温度等火焰传播特征参数,并分析煤尘-甲烷预混燃烧火焰的传播特性以及煤尘粒径和甲烷浓度对混合物燃烧火焰传播特性的影响。得出以下结论:(1)煤尘-甲烷预混燃烧火焰传播形态以及燃烧强度与甲烷浓度以及煤尘粒径密切相关。甲烷浓度为3.7%时,火焰前锋呈离散不规则状态,而当甲烷浓度增大为4.5%、6.7%时,火焰前锋呈较规则的平面或抛物面;当煤尘粒径较小时,燃烧火焰前沿较为规则连续,且发出较为强烈的白光,表明燃烧较为剧烈,而随着煤尘粒径的增大,燃烧火焰前沿趋向于离散不规则状态,发出红黄色光,表明燃烧强度降低。(2)在预混燃烧火焰传播过程中,甲烷燃烧火焰放热和粒径大小影响热电偶温度上升时间,但主要是甲烷浓度决定热电偶温度上升时间;煤尘粒子燃烧决定火焰温度最大值。在煤尘粒径较大(54-74μm)时,不同甲烷浓度的温度上升时间差别很大;煤尘粒径减小时,甲烷浓度为3.7%和4.5%的温度上升时间差别不大,但甲烷浓度为6.7%的温度上升时间差别较大;6.7%的甲烷浓度的火焰温度在预混物点燃很短的时间内及开始上升。随煤尘粒径增大,由于煤尘粒子的反应速率和释放的能量都降低,火焰温度整体随煤尘粒径增大而减小,但中间略有波动。(3)火焰传播速度是由甲烷和煤粉共同决定的,其中甲烷对火焰传播速度影响远远大于煤粉,而煤粉的火焰传播速度随粒径的增大而减小,因此,当煤粉粒径小于30-38.5μm时,甲烷浓度对预混火焰的传播起主导作用,6.7%甲烷浓度的预混火焰传播速度远远大于3.7%和4.5%甲烷浓度;当煤粉粒径大于30-38.5μm时,煤粉粒径开始影响预混火焰的传播特性,导致火焰传播速度降低。同时,课题分别采用单步化学反应模型(the single kinetic rate model)和扩散-动力控制燃烧模型(the kinetics/diffusion-limited rate model)重现煤尘-甲烷混合物的预混燃烧过程。通过分析燃烧管道中煤尘-甲烷混合物的预混燃烧的火焰图像以及火焰温度,并结合数值模拟方法,得出以下结论:(4)由煤尘-甲烷预混燃烧的数值模拟结果表明,预混火焰的前锋位置以甲烷燃烧为主,而对于煤尘粒子,小部分热量在火焰前锋内释放,但在火焰前锋过后,煤尘粒子依然持续燃烧较长的时间,并释放出它的大部分热量。(5)根据煤尘-甲烷预混燃烧火焰锋面处的温度和化学反应速率数值模拟云图可得到预热区厚度。在不同实验条件下煤尘-甲烷预混燃烧火焰的预热区厚度在2~16mm范围之间,且随煤尘粒径的增大,火焰传播速度降低,热量传播时间增加,在相同的热传导速率条件下预热区厚度增加。随甲烷浓度增大,甲烷燃烧反应速率增高、释放热量增多,传递给预热区的热量增多,使得预热区厚度增大。
[Abstract]:The characteristics of the flame combustion experimental platform blends to build coal - methane pre, combined with high speed camera, data acquisition instrument and temperature sensors, the measured under different conditions of coal - methane premixed combustion flame shape map, propagation speed, the flame propagation characteristic parameters of temperature, and the analysis of coal - methane premixed combustion flame and the characteristics of coal dust particle size and concentration of methane on flame propagation characteristics of combustion of the mixture effect. Draw the following conclusions: (1) the burning flame shape and combustion intensity and concentration of methane and coal dust particle size is closely related to pre mixed coal methane. Methane concentration is 3.7%, the flame front is discrete and irregular, and when the concentration of methane increase of 4.5%, 6.7%, the flame front had a regular plane or paraboloid; when the dust particle size is small, the flame front is regular and continuous, the strong white hair The light indicates that the combustion is more severe, and with the increasing of the size of coal dust particle, the flame front tends to discrete and irregular state, a red and yellow light, indicating that the combustion intensity decreased. (2) in the premixed combustion flame propagation, flame heat and particle size effect of thermocouple temperature rise time of methane combustion, but mainly the methane concentration determines the thermocouple temperature rise time; coal dust combustion to determine the maximum flame temperature in coal dust. The larger particle size (54-74 m), different methane concentration temperature rise time difference; dust particle size decreases, methane concentration is 3.7% and 4.5% of the temperature rise time had little difference, but the methane concentration is 6.7% the temperature rise time difference; 6.7% of the methane concentration in the premixed flame temperature are ignited in a very short period of time and began to rise. With increasing diameter of coal dust particle, the reaction rate and the release of dust particles Energy is reduced, the temperature of the flame with the dust particle size decreases, but slight fluctuations. (3) the flame propagation velocity is determined by methane and coal, the effects of methane on flame propagation speed is far greater than that of pulverized coal, and the flame propagation velocity of pulverized coal with the particle size decreasing, therefore, when the coal the particle size is less than 30-38.5 m, the pre mixed flame propagation of methane concentration plays a dominant role, 6.7% concentration of methane premixed flame propagation speed is far greater than the 3.7% and 4.5% methane concentration; when the particle diameter is larger than 30-38.5 m, the propagation characteristics of pulverized coal particle size began to influence the premixed flame, the flame propagation speed reduced. At the same time, paper by a one-step chemical reaction model (the single kinetic rate model) and diffusion kinetic control combustion model (the kinetics/diffusion-limited rate model) to reproduce the coal - methane mixture premixed combustion Burning process. Through the analysis of the combustion pipe in coal - methane mixture premixed combustion flame image and flame temperature, and combining with numerical simulation, draw the following conclusions: (4) numerical simulation by coal - methane premixed combustion. The results show that the forward position of premixed flame in combustion of methane, and for coal dust particles small part of the heat release, the flame front, but after the dust particles in the flame front, still continue to burn for a longer time, and most of the heat release of it. (5) according to the flame temperature and chemical reaction rate can be obtained by numerical simulation of cloud thickness preheating zone combustion of blended coal methane in coal - pre. Under different experimental conditions of methane premixed combustion flame preheating zone thickness in the range of 2~16mm, and with the increase of the diameter of coal dust particle, the flame propagation speed is reduced, the heat transmission time increases, in the same heat conduction velocity The thickness of preheating area increased with the increase of methane concentration, and the rate of methane combustion increased, the amount of heat released increased, the heat transferred to the preheating area increased, and the thickness of preheating area increased.

【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD714.5;O643.21

【参考文献】