燃气燃烧与应用：第6章 扩散式燃烧器

1、2022/8/21第六章 扩散式燃烧器Diffusion Flame Burners1.燃烧器分类与技术要求 Burner Classification & Tech. Requirements2.自然引风式扩散燃烧器 Diffusion Flame Burners3. 鼓风式扩散燃烧器 Nozzle Mix Burners2022/8/22第一节 燃烧器的分类与技术要求一、燃烧器的分类（一）按一次空气系数分类1.扩散式燃烧器2.大气式燃烧器3.完全预混式燃烧器Burner Classification & Tech. Requirements2022/8/23（二）按空气的供给方式分类1.引

2、射式燃烧器2.鼓风式燃烧器3.自然引风式燃烧器（三）按燃气的压力分类1.低压燃烧器：燃气压力在5000Pa以下2.高（中）压燃烧器:燃气压力在5000Pa-3105 Pa之间2022/8/241.燃烧器分类与技术要求 Burner Classification & Tech. RequirementsBurner for industrial & commercial applications can be broadly classified under 5 headings, based on the means adopted for mixing gas & air:Diffusion

3、-flame, post-aerated, neat gas, non-aerated, luminous burnerGas issuing from the burner or pipe is neat, no premixing of air and gas takes place. The necessary air for combustion arrives at the reaction zone from the surrounding atmosphere by diffusion or entrainment after burner nozzle.Laminar flow

4、, turbulent flow2. Atmospheric burner, Natural-draught, Gas Blast BurnerGas entrains a % of the air for combustion before entering the burner. This is achieved by an atmospheric injector, where the gas under pressure entrains atmospheric air. Flame: short & intense. Gas pressure 10-20mbar, air injec

5、ted less than stoichiometric, secondary, LP Gas pressure increase, air injected=stoichiometric, no 2nd air, HP2022/8/251.燃烧器分类与技术要求 Burner Classification & Tech. Requirements3. Air-blast, All or part of the air required is supplied at pressure above atmospheric by fan or compressor. Air entrains gas

6、. Another premix system4. Nozzle-mix burnersno prior mixing of the gas and air until the burner nozzle. Gas and air proportioned separately by linked valves or other techniques and fed independently to burner nozzle. The air and gas enter separate manifolds prior to burner nozzle where their flow pa

7、tterns are controlled.Mixing by this method is very positive, intense rates of combustion are developed for high temperature work5. Other burner systemPulsating combustor, catalytic combustor, radiant tubes, immersion tube burner etc.2022/8/26二、对燃烧器的技术要求1.燃烧比较完全；2.在额定压力下燃烧器达到额定热负荷； 3.燃烧效率高；4.燃烧稳定；5.

8、结构紧凑、调节方便、无噪音。2022/8/27对工业燃烧器的另外技术要求:1.严格按照要求的燃烧方法进行燃烧，并建立炉内所需要的气氛（氧化、还原、中性）；2.火焰特性符合要求（温度、高度等）；3.配备必要的自动调节和自动安全装置。2022/8/286.2,自然引风式扩散燃烧器 Diffusion Flame Burners定义：按照扩散式燃烧方法设计的燃烧器称为扩散式燃烧器。Neat gas supplied to burner head and mixes with surrounding atmospheric airLaminar diffusion/posted aerated fla

9、mes: mixes by molecular diffusionTurbulent post-aerated flame: Eddy diffusionMixing + combustionLuminous appearance: unburnt gas being cracked by heat developed by the outer flameHistorically in the era of manufactured gas, diffusion flame burners dominated the design of most domestic, commercial an

10、d low temperature industrial heating plant2022/8/29扩散式燃烧器自然引风式扩散燃烧器强制鼓风式扩散燃烧器一、自然引风式扩散燃烧器（一）构造及工作原理2022/8/210节流圈或阀门燃气2022/8/2111.管式扩散燃烧器（1）排管式扩散燃烧器2022/8/212（2）涡卷式扩散 燃烧器集气管涡卷形管子特点:a.节省炉膛所占有的面积;b.在组成的平面上火孔分布均匀;c.空气流畅。2022/8/2132. 扇形火焰扩散燃烧器特点:a.火孔呈缝隙状;b.火焰与空气接触面大; c.燃烧快，火焰短。2022/8/2143. 冲焰扩散燃烧器特点: 火焰相

11、撞增加了混合强度，提高了燃烧的稳定性。2022/8/2154. 炉底（床）扩散式燃烧器夹角： 900-1800直管管径d： 50-100mm火孔直径dp： 2-4mm火孔中心距： (6-10)dp 2022/8/2164. 炉底（床）扩散式燃烧器夹角： 900-1800直管管径d： 50-100mm火孔直径dp： 2-4mm火孔中心距： (6-10)dp 2022/8/217Laminar Post-aerated Burner for Natural Gas2022/8/218Laminar Post-aerated Burner for Natural Gas2022/8/219Turbu

12、lent Post-aerated Burner for Natural Gas2022/8/220（二）自然引风式扩散燃烧器火孔热强度火孔热强度: 1mm2火孔面积在单位时间内所放出的热量。单位：W/mm2(J/mm2h)2022/8/221不同燃气的火孔热强度对火焰的影响：层流 无黄焰 火软层流 黄焰 火硬过渡区蓝色 紊流离 焰烟 炱2022/8/222（三）自然引风式扩散燃烧器特点和应用范围1.优点（1）燃烧稳定，不回火，运行可靠；（2）结构简单，制造方便；（3）操作简单，易点火；（4）可以利用低压燃气；（5）不需要鼓风设备。2022/8/2232.缺点3.应用范围（1）燃烧强度低，火焰

13、长，燃烧室大；（2）容易产生不完全燃烧；（3）过剩空气系数大，燃烧温度低。 要求温度不高，但是温度分布均匀、火焰稳定的场合。例如：沸水器、热水器、纺织工业烧毛、食品工业的加热、小型采暖锅炉、点火器、指示性燃烧器等。2022/8/224四，管式扩散燃烧器的计算计算目的：确定火孔直径，数目，间距及所需压力已知条件：燃气种类，燃烧器热负荷1， 选取火孔直径dp及火孔间距s2， 选取火孔热强度qp及火孔出口速度vp3， 计算火孔总面积Fp4, 计算火孔数目n5， 计算燃烧器头部燃气分配管截面积Fg6, 计算燃烧器前燃气所需要的压力h2022/8/225五，炉床式扩散燃烧器的计算目的：确定火孔直径，数目

14、，间距，火道尺寸及所需压力已知条件：燃气种类，热负荷，热效率，燃烧室尺寸，炉膛压力1，计算燃气分配管截面积2， 计算火道尺寸3， 计算火孔直径4， 计算火孔间距s5， 计算火孔数目6， 计算燃气分配管长度7， 计算火道尺寸8， 计算燃烧器前燃气所需要的压力h2022/8/2266.3.鼓风式扩散燃烧器 Nozzle Mix Burnerstunnel mixing burners, or package burners, Air supply at pressure, discharged through an annulus or annuli at the burner head or f

15、ace. Gas ports, which again may be of many forms, admit gas into the air stream Combustion takes place either totally or partially in a burner tunnel or at the burner face.Air/gas mixing and combustion takes place simultaneously at the burner nozzle, usually in a refractory tunnel or quarl. The tunn

16、el acts as a means of flame retention:1. heat stored in the refractory walls serves to stabilise the flame, 2. recirculation of flame gases keeps the root of the flame at temperatures encouraging ignition. This enables satisfactory operation at quite low throughputs, both in stoichiometric condition

17、s and with a large excess of air. Light-back is unlikely to occur, since combustion and mixing are co-current. 2022/8/227强化燃气与空气混合的措施： 将燃气分成多股细流射入空气中； 采用空气旋流。鼓风式燃烧器形式: 套管式; 旋流式; 平流式等。2022/8/228（一）鼓风式燃烧器的构造和工作原理1.套管式燃烧器优点： （1）结构简单； （2）工作稳定， 不回火。缺点： 燃气、空气为同心平行流，混合强度弱，火焰较长。2022/8/229British Gas Self Pr

18、oportioning Tunnel Mixing BurnerLarge area for mixing, a series of air jets is used surrounding the central gas pipe, all discharging axially into a refractory tunnel, or quarl. Air jets provide a recirculation stabilising system. Multi-tube versions of this burner are used for large loadings, in ex

19、cess of 300 kw2022/8/230Stordy-Hauck NMG BurnerThis type of burner provides low velocity gas entry, whilst air enters in three ways:Tangentially in a plane at 90 to the flow axis, through a series of holes in the gas pipe.Axially through a ring of small holes situated in a stepped collar surrounding

20、 the gas pipe.Axially, through an outer annulus formed by the stepped collar of the gas pipe and the burner quarl Tunnel mixing burner with parallel flow discharge and stabilisation by hot refractory surface2022/8/231Urquhart NM BurnerTunnel mixing burner with opposing gas and air swirls to assist m

21、ixingAir is supplied through a series of air jets inclined to burner axis, Gas entering through a central orifice. Mixing surface area is increased by using a series of air orifices rather than an annulus. The air jets constitute a means for forming stabilising eddies2022/8/2322.旋流式燃烧器其结构特点为燃烧器本身带旋流

22、口，根据旋流器的结构及供气方式分1）、导流叶片式旋流燃烧器2）、中心供气蜗壳式旋流燃烧器3）、螺旋板式燃烧器4）、切向供空气旋流式燃烧器5）、径向供燃气旋流式燃烧器2022/8/2332.旋流式燃烧器（1）导流叶片式旋流燃烧器2022/8/234燃气喷嘴2022/8/235Tunnel mixing burner with swirling flow discharge and stabilisationOpposed gyrations in the two streams, setting up high relative velocities. Overall flow from the

23、 burner is largely axial, since the gyration of the air stream is relatively low speed. Combustion is stabilised within a divergent refractory quarl, material and heat transfer in the swirl system encourage ignition at the entry to the quarl.2022/8/236（2）中心供气蜗壳式旋流燃烧器2022/8/2373）、螺旋板式燃烧器由2张平行钢板卷制而成，具

24、有2个螺旋通道。 燃气和空气分别从偏心切向进入各自通道，边旋转边向前流动，在燃烧器出口开始混合。 特点：燃气与空气接触面积大，混合均匀，燃烧器调节范围大。2022/8/2384）、切向供空气旋流式燃烧器空气切向进入, 燃气轴向进入, 在高速旋转的空气带动下, 燃气也随之旋转,并进行混合燃烧。火焰呈圆筒型。空气在圆筒形火焰与燃烧室壁中间旋转流动。2022/8/2395）、径向供燃气旋流式燃烧器当燃气孔口布置合理时，每股燃气形成单股射流。故燃气与空气接触面积大，火焰短。若布置不合理，会形成一个大的中心火焰，燃烧恶化 。2022/8/240（二）鼓风式燃烧器的特点和应用范围1.优点（1）与热负荷相同的引射式燃烧器相比，其结构紧凑、体形轻巧，占地面积小； （2）热负荷调节范围大，调节系数一般大于5；（3）可以预热空气或预热燃气；（4）要求燃气压力较低； （5）容易实现煤粉燃气、油燃气联合燃烧。 2022/8/241二、鼓风式燃烧器的特点和应用范围优点：1、Low air pressure may be used2、Preheated