燃?xì)馊紵c應(yīng)用：第6章 擴(kuò)散式燃燒器

1、2022/8/21第六章 擴(kuò)散式燃燒器Diffusion Flame Burners1.燃燒器分類與技術(shù)要求 Burner Classification & Tech. Requirements2.自然引風(fēng)式擴(kuò)散燃燒器 Diffusion Flame Burners3. 鼓風(fēng)式擴(kuò)散燃燒器 Nozzle Mix Burners2022/8/22第一節(jié) 燃燒器的分類與技術(shù)要求一、燃燒器的分類（一）按一次空氣系數(shù)分類1.擴(kuò)散式燃燒器2.大氣式燃燒器3.完全預(yù)混式燃燒器Burner Classification & Tech. Requirements2022/8/23（二）按空氣的供給方式分類1.引

2、射式燃燒器2.鼓風(fēng)式燃燒器3.自然引風(fēng)式燃燒器（三）按燃?xì)獾膲毫Ψ诸?.低壓燃燒器：燃?xì)鈮毫υ?000Pa以下2.高（中）壓燃燒器:燃?xì)鈮毫υ?000Pa-3105 Pa之間2022/8/241.燃燒器分類與技術(shù)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.燃燒器分類與技術(shù)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、對燃燒器的技術(shù)要求1.燃燒比較完全；2.在額定壓力下燃燒器達(dá)到額定熱負(fù)荷； 3.燃燒效率高；4.燃燒穩(wěn)定；5.

8、結(jié)構(gòu)緊湊、調(diào)節(jié)方便、無噪音。2022/8/27對工業(yè)燃燒器的另外技術(shù)要求:1.嚴(yán)格按照要求的燃燒方法進(jìn)行燃燒，并建立爐內(nèi)所需要的氣氛（氧化、還原、中性）；2.火焰特性符合要求（溫度、高度等）；3.配備必要的自動調(diào)節(jié)和自動安全裝置。2022/8/286.2,自然引風(fēng)式擴(kuò)散燃燒器 Diffusion Flame Burners定義：按照擴(kuò)散式燃燒方法設(shè)計(jì)的燃燒器稱為擴(kuò)散式燃燒器。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擴(kuò)散式燃燒器自然引風(fēng)式擴(kuò)散燃燒器強(qiáng)制鼓風(fēng)式擴(kuò)散燃燒器一、自然引風(fēng)式擴(kuò)散燃燒器（一）構(gòu)造及工作原理2022/8/210節(jié)流圈或閥門燃?xì)?022/8/2111.管式擴(kuò)散燃燒器（1）排管式擴(kuò)散燃燒器2022/8/212（2）渦卷式擴(kuò)散 燃燒器集氣管渦卷形管子特點(diǎn):a.節(jié)省爐膛所占有的面積;b.在組成的平面上火孔分布均勻;c.空氣流暢。2022/8/2132. 扇形火焰擴(kuò)散燃燒器特點(diǎn):a.火孔呈縫隙狀;b.火焰與空氣接觸面大; c.燃燒快，火焰短。2022/8/2143. 沖焰擴(kuò)散燃燒器特點(diǎn): 火焰相

11、撞增加了混合強(qiáng)度，提高了燃燒的穩(wěn)定性。2022/8/2154. 爐底（床）擴(kuò)散式燃燒器夾角： 900-1800直管管徑d： 50-100mm火孔直徑dp： 2-4mm火孔中心距： (6-10)dp 2022/8/2164. 爐底（床）擴(kuò)散式燃燒器夾角： 900-1800直管管徑d： 50-100mm火孔直徑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）自然引風(fēng)式擴(kuò)散燃燒器火孔熱強(qiáng)度火孔熱強(qiáng)度: 1mm2火孔面積在單位時(shí)間內(nèi)所放出的熱量。單位：W/mm2(J/mm2h)2022/8/221不同燃?xì)獾幕鹂谉釓?qiáng)度對火焰的影響：層流 無黃焰 火軟層流 黃焰 火硬過渡區(qū)藍(lán)色 紊流離 焰煙 炱2022/8/222（三）自然引風(fēng)式擴(kuò)散燃燒器特點(diǎn)和應(yīng)用范圍1.優(yōu)點(diǎn)（1）燃燒穩(wěn)定，不回火，運(yùn)行可靠；（2）結(jié)構(gòu)簡單，制造方便；（3）操作簡單，易點(diǎn)火；（4）可以利用低壓燃?xì)?；?）不需要鼓風(fēng)設(shè)備。2022/8/2232.缺點(diǎn)3.應(yīng)用范圍（1）燃燒強(qiáng)度低，火焰

13、長，燃燒室大；（2）容易產(chǎn)生不完全燃燒；（3）過剩空氣系數(shù)大，燃燒溫度低。 要求溫度不高，但是溫度分布均勻、火焰穩(wěn)定的場合。例如：沸水器、熱水器、紡織工業(yè)燒毛、食品工業(yè)的加熱、小型采暖鍋爐、點(diǎn)火器、指示性燃燒器等。2022/8/224四，管式擴(kuò)散燃燒器的計(jì)算計(jì)算目的：確定火孔直徑，數(shù)目，間距及所需壓力已知條件：燃?xì)夥N類，燃燒器熱負(fù)荷1， 選取火孔直徑dp及火孔間距s2， 選取火孔熱強(qiáng)度qp及火孔出口速度vp3， 計(jì)算火孔總面積Fp4, 計(jì)算火孔數(shù)目n5， 計(jì)算燃燒器頭部燃?xì)夥峙涔芙孛娣eFg6, 計(jì)算燃燒器前燃?xì)馑枰膲毫2022/8/225五，爐床式擴(kuò)散燃燒器的計(jì)算目的：確定火孔直徑，數(shù)目

14、，間距，火道尺寸及所需壓力已知條件：燃?xì)夥N類，熱負(fù)荷，熱效率，燃燒室尺寸，爐膛壓力1，計(jì)算燃?xì)夥峙涔芙孛娣e2， 計(jì)算火道尺寸3， 計(jì)算火孔直徑4， 計(jì)算火孔間距s5， 計(jì)算火孔數(shù)目6， 計(jì)算燃?xì)夥峙涔荛L度7， 計(jì)算火道尺寸8， 計(jì)算燃燒器前燃?xì)馑枰膲毫2022/8/2266.3.鼓風(fēng)式擴(kuò)散燃燒器 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強(qiáng)化燃?xì)馀c空氣混合的措施： 將燃?xì)夥殖啥喙杉?xì)流射入空氣中； 采用空氣旋流。鼓風(fēng)式燃燒器形式: 套管式; 旋流式; 平流式等。2022/8/228（一）鼓風(fēng)式燃燒器的構(gòu)造和工作原理1.套管式燃燒器優(yōu)點(diǎn)： （1）結(jié)構(gòu)簡單； （2）工作穩(wěn)定， 不回火。缺點(diǎn)： 燃?xì)?、空氣為同心平行流，混合?qiáng)度弱，火焰較長。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.旋流式燃燒器其結(jié)構(gòu)特點(diǎn)為燃燒器本身帶旋流

22、口，根據(jù)旋流器的結(jié)構(gòu)及供氣方式分1）、導(dǎo)流葉片式旋流燃燒器2）、中心供氣蝸殼式旋流燃燒器3）、螺旋板式燃燒器4）、切向供空氣旋流式燃燒器5）、徑向供燃?xì)庑魇饺紵?022/8/2332.旋流式燃燒器（1）導(dǎo)流葉片式旋流燃燒器2022/8/234燃?xì)鈬娮?022/8/235Tunnel 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）中心供氣蝸殼式旋流燃燒器2022/8/2373）、螺旋板式燃燒器由2張平行鋼板卷制而成，具

24、有2個(gè)螺旋通道。 燃?xì)夂涂諝夥謩e從偏心切向進(jìn)入各自通道，邊旋轉(zhuǎn)邊向前流動，在燃燒器出口開始混合。 特點(diǎn)：燃?xì)馀c空氣接觸面積大，混合均勻，燃燒器調(diào)節(jié)范圍大。2022/8/2384）、切向供空氣旋流式燃燒器空氣切向進(jìn)入, 燃?xì)廨S向進(jìn)入, 在高速旋轉(zhuǎn)的空氣帶動下, 燃?xì)庖搽S之旋轉(zhuǎn),并進(jìn)行混合燃燒?；鹧娉蕡A筒型?？諝庠趫A筒形火焰與燃燒室壁中間旋轉(zhuǎn)流動。2022/8/2395）、徑向供燃?xì)庑魇饺紵鳟?dāng)燃?xì)饪卓诓贾煤侠頃r(shí)，每股燃?xì)庑纬蓡喂缮淞?。故燃?xì)馀c空氣接觸面積大，火焰短。若布置不合理，會形成一個(gè)大的中心火焰，燃燒惡化 。2022/8/240（二）鼓風(fēng)式燃燒器的特點(diǎn)和應(yīng)用范圍1.優(yōu)點(diǎn)（1）與熱負(fù)荷相同的引射式燃燒器相比，其結(jié)構(gòu)緊湊、體形輕巧，占地面積??； （2）熱負(fù)荷調(diào)節(jié)范圍大，調(diào)節(jié)系數(shù)一般大于5；（3）可以預(yù)熱空氣或預(yù)熱燃?xì)?；?）要求燃?xì)鈮毫^低； （5）容易實(shí)現(xiàn)煤粉燃?xì)?、油燃?xì)饴?lián)合燃燒。 2022/8/241二、鼓風(fēng)式燃燒器的特點(diǎn)和應(yīng)用范圍優(yōu)點(diǎn)：1、Low air pressure may be used2、Preheated