低浓度瓦斯脉动燃烧的理论与实验研究

发布时间：2018-05-31 23:11

本文选题：煤矿瓦斯 + 低浓度　；参考：《中国矿业大学》2013年博士论文

【摘要】：大力开发低浓度煤矿抽采瓦斯这种具有高热值，低污染的新能源，对优化我国能源消费结构，促进环境经济协调发展有着重要的作用和意义。但对于煤矿低浓度瓦斯来说由于其甲烷浓度含量低燃烧释放热值低，用常规的燃烧方式很难将其稳定燃烧高效利用，极大地制约了其利用率。针对这个问题，本文将脉动燃烧技术与煤矿低浓度瓦斯燃烧利用相结合，提出一种新的低浓度瓦斯燃烧利用方法，并从燃烧理论、数值模拟及实验研究三个方面对低浓度瓦斯脉动燃烧特性进行分析研究。理论研究上分析了脉动燃烧基本理论，包括其工作原理、热力学模型及热声耦合机理，结合低浓度煤矿瓦斯燃烧特性，建立了低浓度瓦斯脉动燃烧气柱振荡模型的数学模型并根据瑞利准则，分析了脉动燃烧稳定性机理和驱动机理；建立了低浓度瓦斯脉动着火的数学模型，并探讨了脉动燃烧过程中控制污染物排放的机理。结合低浓度瓦斯气体燃料的性质及实验条件，，确定了脉动燃烧器型式为Helmholtz型，根据脉动燃烧器设计原则，设计了额定功率为10kW的低浓度瓦斯脉动燃烧装置，系统主要包括：配气系统、燃烧系统及数据采集测量系统。在数值模拟方面建立了适合低浓度瓦斯脉动燃烧的数学模型、物理模型及求解模型，并通过编制UDF入口控制程序实现了对脉动入口边界条件的自动控制，运用Fluent流场分析软件对瓦斯浓度低于10%的低浓度瓦斯脉动燃烧特性进行了研究，数值模拟结果表明：在一个脉动周期内各流场分布包括压力场、速度场及温度场分布也呈现周期性变化，其变化趋势符合脉动原理；在进气入口夹角为90°时温度场分布最均匀；污染物NOx分布明显低于常规的直接燃烧，并以快速型NOx为主；实验研究：首次自行搭建了低浓度煤矿瓦斯脉动燃烧实验台，对低浓度瓦斯的脉动燃烧特性进行了实验研究。实验结果表明：通过燃烧火焰声音、燃烧室压力及空气自吸现象可以判断是否进入脉动；找出了影响各燃烧指标的主要脉动参数；以及低浓度瓦斯在不同脉动燃烧参数条件下的燃烧污染物排放特性；同时得到了在实验条件下额定负荷为10kW的燃烧功率时，低浓度瓦斯脉动燃烧的脉动频率范围60-110Hz；燃烧最佳参数组合为热负荷8kW、尾管长度2000mm、瓦斯浓度8%；实验结果还表明采用脉动燃烧方法不仅可以扩展低浓度瓦斯的贫燃极限，实现瓦斯在5%浓度下稳定而充分的燃烧，而且污染物的排放也处于一个较低的水平范围之内。论文最后将实验结果与数值模拟结果进行了比较分析，结果表明实验与模拟得到的脉动参数变化对燃烧特性的影响具有相同的变化规律，即尾管长度越长，脉动频率越低；瓦斯浓度越大，燃烧温度越高；燃烧室温度随着热负荷的增加而增加在并在一定热功率时达到最大，证明了数值模拟结果的准确性与燃烧模型的正确性。
[Abstract]:The development of low concentration coal mine gas, which has high heat value and low pollution, has an important role and significance to optimize the energy consumption structure and promote the coordinated development of the environment and economy. However, it is difficult to use conventional combustion methods for low concentration gas in coal mines because of low methane concentration and low burning rate. In view of this problem, a new low concentration gas combustion method is proposed by combining pulsating combustion technology with low concentration gas combustion in coal mine, and the combustion characteristics of low concentration gas pulsation from three aspects of combustion theory, numerical simulation and experimental research are presented in this paper. Carry on the analysis and study.
In theory, the basic theory of pulsating combustion is analyzed, including its working principle, thermodynamic model and thermoacoustic coupling mechanism. Combining with the gas combustion characteristics of low concentration coal mine, a mathematical model of gas column oscillation model of low concentration gas pulsating combustion is established and the mechanism of pulsating combustion stability and driving mechanism are analyzed according to Rayleigh criterion. The mathematical model of pulsating ignition of low concentration gas is discussed, and the mechanism of controlling pollutant emission in pulsating combustion process is discussed.
According to the properties and experimental conditions of low concentration gas and gas fuel, the pulsating burner type is Helmholtz type. According to the design principle of pulsating burner, a low concentration gas pulsating combustion device with a rated power of 10kW is designed. The system mainly includes the gas distribution system, the combustion system and the data acquisition and measurement system.
In the numerical simulation, a mathematical model, a physical model and a solution model for low concentration gas pulsation combustion are established, and the automatic control of the boundary conditions of the pulsating inlet is realized by a UDF entry control program. The Fluent flow field analysis software is used to study the combustion characteristics of the low gas pulsation combustion of a gas with a concentration of less than 10%. The numerical simulation results show that the distribution of the flow field in a pulsating period includes the pressure field, the velocity field and the distribution of the temperature field also show periodic changes. The change trend is in accordance with the pulsating principle; the distribution of the temperature field is the most uniform when the inlet inlet angle is 90 degrees; the NOx distribution of the pollutants is obviously lower than that of the conventional direct combustion. NOx is the main part.
Experimental research: for the first time, a low concentration coal mine gas pulsating combustion test bed was set up for the first time, and the pulsating combustion characteristics of the low concentration gas were experimentally investigated. The experimental results show that the combustion chamber pressure and air self absorption can be judged to enter the pulse through the combustion of the flame, and the main pulse which affects the combustion indexes is found. The dynamic parameters, and the emission characteristics of the combustion pollutants under the conditions of different pulsating combustion parameters of the low concentration gas, and the pulsating frequency range 60-110Hz of the low concentration gas pulsating combustion under the rated load of 10kW under the experimental conditions, the optimum parameters of the combustion are 8kW, the length of the tail tube, the gas, and the gas. The concentration is 8%, and the experimental results also show that the pulsating combustion method can not only expand the poor combustion limit of low concentration gas, but also achieve a stable and full combustion of gas under 5% concentrations, and the emission of pollutants is also within a lower level.
At the end of the paper, the experimental results are compared with the numerical simulation results. The results show that the change of the pulsating parameters of the experiment and simulation has the same change law on the combustion characteristics, that is, the longer the tail tube length is, the lower the pulse frequency is, the higher the gas concentration is, the higher the combustion temperature is, the combustion chamber temperature increases with the increase of the heat load. The accuracy of the numerical simulation and the correctness of the combustion model are verified by increasing the maximum power at a certain heat power.
【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TD712

【参考文献】