US2488152A - Device for admitting preheated secondary air into furnace fireboxes - Google Patents

Description

Nov* 15, 1949 E. L. WIEDMAN DEVICE FOR ADMITTING PREHEATED SECONDARY AIR INTO FURNACE FIREBOXES Filed July 28, 1945 Patented Nov. 15, 1949 UNITED STATES TENT OFFICE DEVICE FOR ADMITTING PREHEATED SEC- ONDARY AIR INTO FURNACE FIREBOXES 1 Claim.

My invention relates to improvements in fuel saving devices, and more particularly to that type designed to preheat air while being introduced into the combustion chamber of a boiler or furnace to cause the preheated air to commingle with the products of combustion and thus facilitate the burning of unconsumed and escaping gases rising from the burning fuel.

The object of my invention is to provide an airheating device designed to be attached to the door closing the fuel-feed opening in a boiler or furnace so as to project into the combustion chamber of the latter when the door is closed, it being so designed that the air drawn into the device is caused to travel through a circuitous path and to compel the air in its path through the device to come in contact with the maximum heating surfaces and retard the ow of the preheated air therethrough while separating the same into small volumes to assure maximum heating eifect.

It is also the object of my invention to provide a device of this kind, the body portion or casing of which can be cast and in which the minimum of machining is required so as to provide a simple and inexpensive device readily installed to the door of the fuel-feed opening of a boiler or furnace or in the wall of the latter so that preheated air is delivered over the burning fuel.

In the accompanying drawings illustrating my invention in what I now consider its most aplproved form,

Fig. 1 is a central longitudinal section through the device, showing the same applied to the door of a boiler or furnace closing the fuel-feed opening leading to the combustion chamber or iire box.

Fig. 2 is a transverse section taken on line 2 2, Fig. 1, looking toward the right.

Fig. 3 is a transverse section on the same line, looking to the left.

Fig. 4 is a transverse section taken on line 4 4, Fig. 1, looking in the direction of the arrow crossing said line.

Fig. 5 is a transverse section taken on line 5 5, Fig. 1, looking in the direction of the arrow crossing said line.

The device comprises a housing or casing 6 which is preferably cast in two parts 'I and 8, connected together in a manner to be hereinafter described to form a unitary structure.

Medially this housing is cylindrical, as at 9, and at its attaching or outer end it is enlarged, as at I D, to form a bell-shaped terminal, or expansion chamber as it may be termed. The inner or free end of the housing or casing is of 2 bulbous formation and gradually enlarged from the medial cylindrical portion 9. This bulbous portion is designated by the numeral II and serves also as an expansion chamber. In the region of this bulbous portion the two parts l and 8 of the casing or housing are connected to' closed by an end Wall I4 having a hub I5 and spacing lugs IS lying in contact with the inner surface of the door II closing the fuel-feed opening leading to the combustion chamber of a boiler or furnace in which -coal or other similar fuel is used to generate heat. Extending through the door I'I isa pipe I8 which is threaded into the hub I5 of the casing and to the outer end of this pipe an air-inlet head I9 is threaded, it having a chamber 20 in communication with the interior of the pipe I8 and numerous air-inlet openings 2i leading to said chamber. This air-inlet head also serves as a nut to tighten the device against the inner side of the door I1. An air-inlet pipe 22 is also threaded into the hub I5 from the inner side of the casing and this pipe trends lengthwise and axially through the major portion of the casing or housing. Pipe 22 serves asa continuation of pipe I8. A single pipe may, therefore, be substituted for the pipes I8 and 22 so long as it is securely fastened within the end wall lll of the casing and extends through the door I'l a sufficient distance for attachment of the air-inlet head I9 thereto. The pipes I8 and 22 may, therefore, be considered a continuous air-inlet tube, the outwardly projecting portion of which serves as a means to attach the device to the door Ii or to pass the same through an opening in the Wall of the combustion chamber of the boiler or furnace. Broadly considered, the door I1 serves as a portion of the wall of the combustion cham- .ber and, therefore, where hereinafter reference is made to the wallof the combustion chamber, it is to include the door I1.

Cast Within the part 8 of the casing at or near its inner end is a bridge member 23 so constructed that air passing through the casing will pass around this bridge member, and in the drawings I have illustrated segmental openings 2d at opposite sides of the bridge member for this purpose. This bridge member is recessed on its outer face and into this recess is threaded or other- Wise' secured an air-return pipe 25 surrounding and concentric with the air-inlet pipe 22 and spaced therefrom to form an annular air passage 26 between the two pipes, or tubes as they may also be termed. By reason ci its attachment to the bridge member 23, this air-return pipe is closed at its inner end and its outer end is open and terminates in spaced relation to the end wall I4 of the casing. i In the enlarged outer end of the casing an annulariange 27 is cast and projecting from the end surface of thisange are heating fingers or elongated nubs 28 which trend outwardly or toward the open end of the air" return pipe 25. These ngersorjriiihs"are'spaeed apart circumferentially and sirieeftheyare 'fornieii integral with the wall of the casingithey become well heated due to the fact that'the'y are disposed directly over the burning fuelwitl'iinthefc'om bustion chamber.

nubs 29 project and thse also trend towardthe (.pe'n end` of the' return' pipeVlr 25 The iingers`29 are preferably disposed at a greater' angle 'to the axis of the",d casingthan thev fingers or nubs: 28 and'they are; s taggeredwith relationtothe latter, being p osi'tioriedinY linewith the spaces betvienusaidfingers*'28?` 'I he n'gersor nubs/29 are, therefore;jalfsofina-v circular series. y l

the outer suriarlsed of theA bridge-inember 23faiircularrserie i o'f fheating vngers or ,elongated nubs@ BDeXtend'and'ithey are spacedfrom the air-return pipe 25, a s best shown in Fig. 1.v VSurrounding the circular seriesI of fingers or'n'ubs 30 isk a i circular seriesioilheating fingers for elongated nubs 3l which extendinw'ardly `or .toward the'rairf esca-peend ofthedevice".` ,'Ihengers or nubs 31| of the seriesfaren spaced apart; and spaced' outwardly froml thebutt endfscf`-tlieV lattera ciricular series ofheating ngers ornubs 32' isarranged. These Iare` also'spa'c'ed apart and staggered with respect tothengers lZitlfand 31.

vIt is -to be noted that y the v.free en-dsjof'-l the ngers or nubs '30 terminate in'theiannular space between-'the' circularseriesfofiingers 3f]` 'and 32.'

Projecting `outwardly from thennjeij lsuriaeepf the'ipart 8 of 5thecasing are two' circular series r of fingers 33, '34wihich surround :airesca'pe'area 35"from whichfpreheated lair escapesthr-ougfhfa circular 'series pfff Iai` i escape' openings 36" formed in thjeipart-o'ftheicasing. y i

V'ru clarifykv thejiterms' inwardly and foute w-ardly, L consider-thatfend ofthe deviceseoured to thedoor I1 and: receivingrth'e atmospheric air to bethe outer end and the air-discharge or: op'- po'sit'e end'tobe the inner end.

Ima-device ,ofl this generaltype'airtalenfin n one'end", heated, `an-d discharged over'th'elburniiig fuelA at the other endf' 'Ihe naturalfdifaftfcreated 'byv the communiationwestablished between "the combustion chamber and 'thelchiiijin'ey-1to which theiboiler or'turnacei's 'connected fcreat'e's ia rent 'ofV air through the devicei W'heni thev fifre in the combustion chamber is burning;- the" device isheated byreason of its beingvr locateddirectly above-the burning iuel.,v Air 'passingthroighthe device entersthe inlet openings inthe fair'linifet in its course through the'"device; The '-dii'etibn From the inner side giri-,he Y ange additional heating fingers or elfngatid..

4 of the passage of iair is then again reversed so as to travel in the same direction as the :air passing through the air-inlet pipe 22, coming in contact, whil-e being compressed in the restricted end of the bell-shaped terminal or expansion chamber l0, with the two annular series `of heating lingers 28, 29, which project inwardly from the annular flange/2,1 located rat the receding portion of the Wall of saidv expansion chaginber', the; air being thus lthoroughly heated and the' vair' current broken up by contact with the considerably augmented heating surface Iprovided yby the ngers or nubs 28 and 291' After passing these ngers lor nubs thelair is further, compressed in the medial restrictedgportion 9 of the casing rand retarded in its" passage" through the device, with the result that lal moreecient preheating of the same is assured. After passing through the medial restr'icte'd; portion of the device, or compression chamber as it may be termed, it ag-ain encounters, in: successive order,` the heating in'ger-'sior'-nbs 3`2; '31' and 30, which are' staggeredwithl respect to each otheriandare'located' with'ina gradually widening portion'of the casing sov that a complete breaking 'up of the ia'i'r ciirrer'it isaissured While the 'airisv again-.under expansion.; Againdn pass.- ing'through this p'ortiri'of the larcu'rreni', path provided in the? device`,l'it comes inoontact 4with a' greater augmentedhea'tin'g 'surface`l and due" to the many fingers ornubsi'provided'and Yiiieea'use or trrejeombired"superrciai'areas cfthese nubs exceeding' many tiniesfthesupetcial area'r offth'e partsvfroi'iif'which theyY project, a* considerably higher temperature i'sf prcvidedio'r the airias it apprdachesitsrregi'on o'f escape.

After' passing" through the nngerf or mib area. containing the nubs-'32; 311'and130gthe'air' ypasses through the seg-'mental' op eningsf'za: iny th'en bridge member: Zavyherethe greatesty diameter -o'if the bulbous' inner endor'headiof.thefdevicefis` located. The" 'air then? in 'highly heated forin passes'between the two circular ser-ies off g'ers '33 and 3l and' reaches ther-air escape area 136' surrounded by' saidi 1ast-iinentionedA fingers.. fin-ally?. escaping through the ai'r escape openings 35Fin the'fbulbous inner ender headofthe'device.'

It will'beapparent from the foregoing that the air inpassing tl'noughtheirdevicelis given'a cir'- cuitous' course and'ithat' at twofp oints in its' course it passes through' expansioniregion's vand also through a compression region betweenthe expatrision"regionis.. Alsdby. reason' of the factjthat comparatively longv fingers* or nubs extend iriwardly from the"wa11"of".thev` casing or housing,

which latterfis"thoroughlyheate'd by 'the burning fuel, :these ngers .or nubs are likewise heated` and preheat'ingcontact surfaces AareJprvided"greatly exceeding in superficiali 'areas-thel :annular or cir'- euiar'regions' froiii'whieuthey' reject:` Btl-reason -of the fingers `or nubs being 'slaggerdwith respect 'to each" other;l the'air icurren't's-L are-'divided *onryto' come 'together'again"afoie body under compression by passing through-arsticted -arerafals'o by reason of atleast/brie annlar'series `of angersY or nubs being formed." -on'ajg adualiy restricted wall portion prior to pas'siii'gtlouh a 'restricted area,v the llow' ofthe air` througl'il the device is retarded' and;'thereicre,"subicted'tb the' high temp erature 'within the d'e'ivioef'over a longer periodici 'timefthaii "wouid' otherwisefiiie pessime. ,i

'nrief'preiieatifig 'eff'the'lairz'isgreatiy increased @by reason of" 'the heatngffiigrs for" hubls bei-rig located atapliurfaglityY fof 'regidiisad especially 'Sirce two-'f these 'regiii"a1'e=`l0oted"`at O1? 'i' the air escaping end of the device, where the in- ,terior of the device is subjected to greatest heat. As the air escaping from the device comes in contact with the unconsumed products of combustion, these are ignited and thus consumed pass off in the usual manner through the chimney to which the boiler or furnace is connected after having utilized the maximum heat created for the purpose intended.

It will be apparent from the foregoing that :my invention is subject to many changes in construction and design without departing from the spirit of the same or sacricing any advantages thereof while adhering to the scope of the invention as disclosed in the following claim.

What I claim is:

A fuel saving device for furnaces or the like, comprising a. tubular casing fastened at one end to the wall of a combustion chamber and projecting inwardly therefrom into said chamber, said casing having its fastened end enlarged to form an expansion chamber and its opposite end enlarged to a lesser degree to form a second expansion chamber, an air-inlet :pipe extending axially into said casing from the fastened end thereof and having an air-inlet head outside of said casing through which air enters said pipe, said airinlet pipe being open at its inner end, an air- 6 return pipe having a closed end confronting and spaced from the open inner end of said lair-inlet pipe and having its opposite end opening into said mst-mentioned expansion chamber, two series of heating ngers extending inwardly from the wall of said first-mentioned expansion chamber and having the fingers of one series staggered lwith reference to those of the other, and heating fingers extending from the wall of said second expansion chamber and staggered with respect te each other, said second expansion chamber having air-escape openings through which the heated air escapes aiter contact with the various heating fingers Within ysaid easing.

EDWARD L. WIEDMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,267,295 West May 21, 1918 1,482,104 Van Daam Jan. 29, 1924 1,578,151 Marsh Mar. 23, 1926 1,717,421 Van Daavm June 18, 1929 1,733,901 Owen Oct. 29, 1929

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