洁净煤技术

2020, v.26;No.126(02) 73-77

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预燃室对逆喷旋流煤粉燃烧器流场特性作用研究
Influence of pre combustion chamber on flow characteristics of reverse swirl pulverized coal burner

牛芳;
NIU Fang;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

摘要(Abstract):

煤粉高效低氮燃烧技术是煤炭高效利用领域持续关注的热点。煤粉燃烧器作为煤粉锅炉的核心设备,研究适合多煤种、宽负荷条件的煤粉燃烧器设计原理及技术至关重要。逆喷射流稳燃机理大都应用在航空发动机和燃气轮机领域,在煤粉燃烧领域应用极少。前人大量研究了预燃室对旋流燃烧器流场特性的影响,但鲜见预燃室对逆喷旋流燃烧器流场影响的相关研究。为了探究预燃室对逆喷旋流煤粉燃烧器流场特性的影响规律,笔者针对一款20 t/h逆喷旋流燃烧器,基于等温模化原理建立冷态燃烧器模型,利用热线风速仪和飘带法进行了流场测试和分析,结果表明:预燃室的存在不改变逆喷旋流煤粉燃烧器回流区环形的形状,但在逆喷旋流煤粉燃烧器内形成一个有利于煤粉着火的轴向速度低和湍流强度大的回流区。在X/D<1.3区域内,由于圆锥形预燃室对气流的挤压作用,预燃室的存在对回流区的面积起到抑制作用;在1.32.3区域内,预燃室对燃烧器内部流场的作用减弱,可忽略不计。在预燃室的作用下,回流区最宽处的直径从0.97D降至0.86D,最大相对回流率位置从截面X/D=1后移到截面X/D=1.6处,相对回流率从1.17减小至0.99。预燃室的存在对二次风区域内的轴向平均速度和湍流度分布规律影响较大。无预燃室工况下,在X/D<0.6区域内,速度和湍流度均出现峰值,在X/D>1.6区域内峰值消失,内外二次风完全混合;有预燃室工况下,在X/D<0.6区域速度沿着径向方向逐渐增大,湍流度沿着径向方向逐渐减小,在X/D>1.6区域,速度和湍流度沿着径向方向分布均匀。预燃室的存在有利于回流区煤粉的稳定燃烧,工程应用中起到煤粉迅速着火以及难燃煤稳定燃烧的作用。另外预燃室壁面气流速度较大,刚性强,避免预燃室壁面超温或结焦现象的发生,延长了煤粉燃烧器无故障运行时间和整体的使用寿命。
Pulverized coal high-efficiency and low-nitrogen combustion technology is a hot spot in the field of coal utilization.As a core equipment of the pulverized coal boiler,it is very important to study the design principle and technology of pulverized coal burner suitable for multiple coal types and wide load conditions.The mechanism of reverse jet steady combustion is mostly applied in the field of aero-engines and gas turbines,and rarely used in the field of pulverized coal combustion.Therefore,the studies on the influence of the pre-combustion chamber on the flowfield characteristics of the swirl burner are available,however,there are few studies about the influence on the flow field of the reverse-jet swirl burner.In this paper,In order to explore the influence of precombustion chamber on the flow field characteristics of a reverse swirl pulverized coal burner,and taking a 20 t/h reverse jet swirling burner as a prototype,a cold burner model was built based on the isothermal modeling principle.Then,with the help of streamer method,the flow field test and analysis were carried out via hot-wire anemometer.The results show that the annular shape of the backflow area will not be changed in the presnece of the pre-combustion chamber.By contrast,the recirculation zone,formed within the burned and featured by low axial velocity and high turbulence intensity,is beneficial to pulverized coal ignition. For the aera of X/D < 1. 3,the area of backflow area is prohibited due to the existence of pre-combustion chamber,which is conected to the squeezing effect of the conical pre-combustion chamber on the airflow. While for 1.32.3,the effect of pre-combustion chamber on the internal flow field can be ignored.The widest part of the recirculation zone is reduced from 0.97 D to 0.86 D under the action of the pre-combustion chamber.At the same time,the maximum relative recirculation rate is moved from the cross section X/D = 1 to 1. 6 and the relative recirculation rate is decreased from 1. 17 to 0. 99. The existence of pre-combustion chamber has a great influence on the axial mean velocity and turbulence distribution in the secondary air zone. Under the condition of no pre-combustion chamber,in the region of X/D<0.6,the peak values of velocity and turbulence appear; in the region of X/D>1.6,the peak values disappear,and the inner and outer secondary air are completely mixed; under the condition of pre-combustion chamber,in the region of X/D<0.6,the velocity increases along the radial direction,and the turbulence decreases along the radial direction; in the region of X/D>1.6,the velocity and turbulence are evenly distributed along the radial direction.The existence of pre-combustion chamber is beneficial to the stable combustion of pulverized coal in recirculation zone.It plays the role of rapid ignition of pulverized coal and stable combustion of low volatile coal in engineering application.In addition,the over-temperature or coking phenomenon of the pre-combustion chamber will be prevented by the pre-combustion chamber wall with large air velocity and strong rigidity,which is expected to prolong the trouble-free operation time and overall service life of the pulverized coal burner.

关键词(KeyWords): 预燃室;逆喷旋流燃烧器;烟气回流区;湍流度;轴向速度
pre combustion chamber;reverse swirl pulverized coal burner;recirculation zone;turbulence intensity;axial velocity

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基金项目(Foundation): 煤炭科学技术研究院科技发展基金项目技术创新项目(2018CX02)

作者(Author): 牛芳;
NIU Fang;China Coal Research Institute Company of Energy Conservation;State Key Laboratory of High Efficient Mining and Clean Utilization of Coal Resources;National Energy Technology & Equipment Laboratory of Coal Utilization and Emission Control;

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