【作者】 杨硕；

【导师】 吴晋湘；

【作者基本信息】 河北工业大学 ， 热能工程， 2015， 硕士

【摘要】 弥散燃烧技术具备显著节能和环保的特性,对加强能源的利用、改善空气质量、降低企业生产资金、提高企业的竞争力具有十分重要的意义,国际社会称之为21世纪燃烧领域最具备发展潜力的新型关键燃烧技术之一。为探讨弥散燃烧技术在烟气自循环工业炉上的应用,本文通过软件(FLUENT)数值模拟研究了弥散燃烧技术在工业炉上的形成条件,并进行了实验验证。本文首先验证了工业炉装置下不同湍流模型的适用性,并与实验结果对比分析,发现standard k-ε模型与实际情况最为接近,表现较好。本文就炉膛半径改变对工业炉内形成弥散燃烧过程进行了模拟,发现炉膛半径的加大使得炉膛局部高温区逐步减小。炉膛内平均温度、出口温度、最高温度均降低。这表明宽大的炉膛空间有利于炉膛温度均匀性,形成弥散燃烧过程,但不宜过大增加炉膛半径。在本课题研究中,炉膛半径限定在180mm-240mm最佳。本文对不同燃料流量对工业炉内形成弥散燃烧过程进行了模拟,发现随着燃料流量的增加,炉膛温度分布更加均匀。炉膛的高温区域主要分布在炉膛的中后部,随着燃料流量的增加,高温区域面积逐步扩大。因此,燃料流量较低时,燃烧在相对低氧范围内进行,反应速率缓慢,符合形成弥散燃烧的条件。本文还针对回流烟气预热空气对工业炉内形成弥散燃烧过程影响进行了不同初始空气速度下有无烟气回流通道的对比分析。发现在两种情况下,随着高温空气喷射速度的增加,炉膛内的出口温度、最高温度均下降,炉膛平均温度上升,这符合弥散燃烧的形成条件。在不存在烟气回流通道时炉膛最高温度、出口温度、平均温度以及炉膛温差均远高于存在烟气回流通道情况,NOX的生成量也远远增加。可见,较大空气初始动量对空气、燃料混合的推迟作用及烟气回流对高温空气、燃料的稀释作用。本文就该装置下形成弥散燃烧是否与燃烧器布置方式有关展开了探讨,将燃烧器布置方式改为传统布置样式(中间为燃气入口,上部为空气喷射入口),利用三维模拟探究了燃料喷嘴与空气喷嘴间距不同时流场分布状况。研究表明,当燃料喷口与空气喷口间距不同时,炉膛空间温度场分布变化很大。随着燃气喷嘴与空气喷嘴的间距增大,炉膛温度梯度变小,炉膛空间温度分布更加均匀。符合弥散燃烧基本特征。更多还原

【Abstract】 The technology of diffuse combustion has significant characteristics of energy saving and environmental protection. It has great significance in enhancing the utilization of energy, improving the air quality, reducing the enterprise production capital and enhancing the competitiveness of enterprises. It is considered one of the new key combustion technologies which has the most development potential in the 21 century in combustion field.In this article, to explore the technology of diffuse combustion in the application of the industrial furnace with exhaust gas auto-circulation, numerical simulation of study the forming conditions on the diffuse combustion technology in the industrial furnace was made by software(FLUENT), and experimental verification.Firstly, the paper verifies the applicability of industrial furnace device with different turbulent models, and compares with the experimental results, and finds the standard k-ε model gets closest to the actual situation and it works well.Simulation of changing of industrial furnace hearth radius in diffuse combustion process was made. It is found that the local high temperature reduced gradually by increasing of hearth radius. The average temperature, exit temperature, maximum temperature all reduce. It shows that the wide chamber of a furnace space has advantages in averaging the temperature of furnace hearth, forming diffuse combustion process, but should not be too large to increase furnace radius. In the study of this paper, the best hearth radius is limited to 180mm- 240 mm.Simulation of the influence in forming diffuse combustion by changing fuel flow was made. It finds that the more fuel flows in, the temperature distributes more uniform. The high temperature of furnace area is mainly distributed in the rear of the hearth. The high temperature area will gradually expand, with the increase of fuel flowing in. Therefore, combustion in the scope of relatively low oxygen and the reaction rate slowly meet the requirements of forming diffuse combustion when the fuel flows slowly.This paper also contrast analysis the influence in forming diffuse combustion in industrial furnace by using backflow fuel gas preheating air with or without backflow channel of fuel gas under different initial air velocity. In both cases, the exit temperature, the maximum temperature in the hearth will decrease and the furnace temperature will rise when increasing the injection rate of high temperature air. It is in line with the formation of the diffuse combustion conditions. When there are no flue gas backflow channel in the furnace hearth, max temperature, outlet temperature and the average temperature were much higher than the presence of flue gas flow channel and NOX generation is also increasing. Visibly, larger initial momentum has effect to the air and fuel mixture of delayed action, and flue gas flow has effect to the high temperature air and fuel of dilution.It is discussed that the change of the arrangement of burner to the formation of diffuse combustion, change the burner arrangement to the traditional decorate style(for gas inlet, middle upper air jet entrance), using 3d simulation explores the fuel nozzle and air nozzle flow field distribution of different spacing. Studies show that when the fuel nozzle and nozzle spacing is different, the temperature field distribution in the chamber of a furnace space changes a lot. As the gas nozzle and air nozzle spacing increases, the furnace temperature gradient, furnace space temperature distribution more uniform. Conform to the basic characteristics of diffuse combustion.更多还原