US2818109A - Variable load burner construction - Google Patents

Description

Dec. 31, 1957 T. s. -VOORHE|S VARIABLE LOAD BURNER CONSTRUCTION Filed .June 22, 1953 2 Sheets-Sheet l INVENTOR. TEMPLE 5. VOORHE/S 4 TTOR/VE Y8 Dec. 31, 1957 T. s. VOORHEIS 2,8

VARIABLE LOAD BURNER CONSTRUCTION Filed June 22, 1953 2 Sheets-Sheet 2 INVENTORN TEMPLE 8. VOORHE/S VARIABLE LOAD BURNER CONSTRUCTION Temple S. Voorheis, San Francisco, Calif.

Application June 22, 1953, Serial No. 363,211

2 Claims. (Cl. 1581.5)

This invention relates to a new and improved variable load burner constructions.

In commercial forced air draft oil and gas burners used to generate heat for boilers or the like, it is frequently desirable that such burners be capable of 6113- ciently operating over a relatively broad firing range to meet greatly varied load conditions.

More particularly, in many industrial heating applications in connection with which burners are used, maximum efficiency in over-all operation is attainable only if the burner is capable of successfully operating with substantially equal efiiciency at both a relatively high and relatively low firing rate. Thus, for example, it has been found that in many instances, the burner should be capable of operating substantially equally satisfactorily anywhere within a ten-to-one load range, or, in other words, that the burner should be capable of operating efiiciently at as low as one-tenth of its maximum capacity or firing rate.

Although several of the more conventional forced air draft oil or gas burners in commercial use today of which I have knowledge are capable of operating reasonably efficiently and satisfactorily over a one-to-four or one-tofive firing range, if one attempts to operate such conventional burners at much below one-fourth or one-fifth of their maximum firing rate serious practical difliculties to the point of actual failure in combustion may result.

Perhaps the principal reason why prior art burners cannot be operated successfully at much below one-fourth or one-fifth of their maximum capacity is that no sufficiently satisfactory means has heretofore been developed for insuring an adequate or proper intermixture between air and fuel within the combustion chamber under conditions where both the volume of air and fuel introduced into the combustion chamber is less than one-fourth or one-fifth of the amounts introduced into the chamber when the burner is operated at maximum capacity.

It is a principal object of the present invention, therefore, to provide a burner construction which is capable of operating satisfactorily and efiiciently over a relatively broad firing range, as, for example, over a ten-to-one firing range.

In the drawings:

Fig. l is a side elevational view of a burner construction embodying the invention with portions thereof shown broken away in section.

Fig. 2 is a plan view of the burner with the fan motor cover removed.

Fig. 3 is an enlarged longitudinal sectional view of the burner proper.

Fig. 4 is an enlarged perspective view of one of the air register vanes.

Fig. 5 is an enlarged fragmentary view in side elevation showing the air register vanes, in closed position.

Referring now more particularly to the drawings, the burner construction therein shown comprises, generally a blower or fan assembly A, a plenum or windbox unit B, an air register assembly C,a gas burner assembly D, an

" ice oil injection assembly E, and a combustion chamber, the entrance to which is designated generally at F.

'lhe tan or blower assembly, neretorote indicated generally at A, preferably comprises a motor-drlven tan blower 10 mounted for rotation wlthln a scroll type or volute tan housing 11. 'lhe motor 12 connected by belt drive 1.5 to drive shaft 14 may be convemently located within enclosed Cover 1: removably secured to tan housing 11. the blower discharge end or the tan nOLlSlDg is connected as at 10 to the inlet side or the plenum or windbox heretolore indicated generally at B.

As above indicated, windbox 5 consists of a scroll type or volute casing 11 which may be provided with one or more internal names such as indicated at 16 for insuring umrorm air distribution to the burner via circular air register C.

blIULllzlI air register C comprises, more specifically, a plurality of arcuate vanes 19, each of wmcn are plvotally mounted on an associated axle 21 ror cltljLlSlflDlfi opening and closing movements. More particularly, each or the vane sup orting axles A1 are rotataoiy jOufndlfid to opposlte sioes or a circular rrame AA whereby the vanes may be dUJUdLaU-l) opened or closed in unison concurrently with variation in nrlng rate, by control means to oe herelnalter described.

Lurcular arr register assembly C is located within the scroll plenum 11 111 such manner that the clearance between the circular register and the walls or the plenum diminishes in the direction or the air now through the plenum so as to insure unlrorm distribution or air through the register vanes and into the burner.

the circular register is also located coaxially with respect to the throat opening of the combustion chamber, as well as with respect to the gas inyectlon ring and oil spray nozzle of the burner, as will more fully hereinafter appear.

the construction of the air register is preferably such that when the vanes are fully closed or shut each vane lies generally within the plane of circumference of the circular register frame. lt is further noted that the vanes are constructed and arranged so that when they are closed contiguous edges of ad acent vanes partially overlap one another in shingle-like arrangement, as shown in Fig. 5, for example. because when the vanes are closed to near shut position during operation of the burner within its lowermost firing range, a highly desirable spiral motion will be imparted to the air now through the register vanes as it passes into the combustion chamber. The importance and significance of inducing a spiral action to the air draft during low load operating conditions will be described more fully hereinafter.

Each of the vane axles 21 may be provided with a pinion or spur gear, such as indicated at 23, adjacent its rearwardly projecting end. To control opening and closing movements of the vanes 19 in unison a ring gear 24 may be provided in mesh engagement with all of the vane axle pinions 23. Selective movement of ring gear 24 in clockwise or counter-clockwise direction may be controlled through manipulation of control lever 26 provided with a spur gear or pinion 27 in mesh engagement with ring gear 24. Referring specifically to Fig. 1, it is seen that upward movement of lever 26 will through its spur gear connection with the ring gear,

cause the latter to move in a clockwise direction for chronizing the opening and closing movements of the circular air register vanes concurrently with variations 'lhis arrangement is important v in the "air aiidfuelsupplyto the burner, a manual control station, indicated genran' at G,"may b'eprovided. More specifically, control station G comprises a manual control lever 50, pivoted as at to quadrant 52 and pivotally connected "byjlink arm '53 to mul ti-Iouve'r fair damper 54, which said damper is'in communication with fan housing for regulating the volume of 'air flow into the blower'iinit. c sed arm "50 is also pivotally corinetedtb g'as valve55 by a link arm "56. Control arm 50 is further connected to control lever 26 by link "5622. I I

Fromtlieforegoin'g arrangem nt, it is seen that when master controllev'er 50 is moved upwards, the damper blades "57 of -niul'ti lo'u ver damper S i will move toward closed position through conventional linkage comprising a control bar '59 and blade levers 61), thereby restricti'ng the volume "of 'air into blower unit 19. Upward movement of 'i'n'aster control lever 50 will also cause corfespondirig closing of "gas'valve 55 and circular air register C by virtue of link connections 56 and 56a with these latter components. a

It is evidentfof course, "that downward movement of manuareontreiiever SD will, through the linkageabove mentioned, cause corresponding simultaneous opening of theinultidouver damper 54, air register assembly C, and gas valv'e ss.

It'vvill ber'ea'dily understood, of course, that when oil instead of 'gasis burned, other linkage corresponding to that described above for opening and closing the gas valve may be provided'for similarly controlling the oil supply to thebiirner upon movement of manual control lever 50 ana'iapmp'e'r relation to the'air supply.

In addition to'providing a manual control station for adjustablyre'g'ulating the supply of fuel and air depend ing on existing load conditions concurrently with adjustmerit of 'v'ane' opening of an adjustable vane register as abov'e' describ'ed, it is desirable in many commercial installations embodying theinvehtion to provide a suitable sysmm for automatically controlling both the air and fuel supply to the burner according to varying load conditions. It will sufiice to remark that various types of automatic or semi automatic control systems have been developed and used i'n'the past for controlling air and fuel supply to a burner according to heat requirement of the boileror other unit in connection with which the burner is employed for generating heat. Such automatic or semi-automatic control systems are, accordingly, well known in the art, and further elaboration in regard to such'sy'stems'is therefore considered unnecessary, beyond recognizing that by this invention such automatic means of varying rate of fuel and air supply to a burner, will concurrently'vary the vanes of an adjustable vane air register as above described from a closed or nearly closed position at minimum firing rate to a largely open position at maximum firing rate.

The actualburner unit shown in the drawings comprising gas burner assembly D, oil injection assembly E, and combustion chamber, above mentioned, inayalso be of more or les conventional design. More specifically, the entrance to combustion chamber F is truncated conical shape in cross-section defining a restricted throat 27, and is formed of suitable plastic refractory material.

The oil burner assembly E is shown as comprising a mechanical atomizer (or steam atomizer) 28 adapted for connection to a source of oil (and steam) under pressure (not shown), an oil supply tube 29 and a spray nozzle tip 31. The supply tube 29 andspray tip 31 are housed within'a guide tube 32 which, inturn,'isprovided with an oil burner shield 33 adjacent its forward end.

Thegas'burner assembly-D-is shown as comprising a gas ring 3-4 adapted forconnection via supply conduit 35 to a source of gas under pressure (not shown) and-formed with-a plurality of; gas jets-or openings 36 through which gas is supplied tothe combustion chamber.

Generally speaking, whenaburner of the:generaltype above described is operated within a firing range at or "approaching its maximum firing "rate, no particular "diffi- 'lent intermixing between thefuel and air by virtue of the decreased volume of air and fuel being introduced into the combustion chamber at the lower firing ranges.

As hereinabove pointed out, the more conventional oil or gas burners employing a scroll plenum or a circular or rectangular plenum in conjunction with a fixed vane type register, are incapable of being operated within a firing range inuc h below one-fourth to one-fifth of maximum capacityi. e. when an attempt is made to operate the burner at a firing rate between one-fifth to'onetenth of maximum capacity, improper combustion, or failure of combustion, will result, due .principally tolack of sufficieiit rotational air velocity toprovide adequate turbulent intermixing of the fuel and the air.

However, in burners constructed accordingto the present invention when such a burner is-operated in-itslower firing range, the air register vanes arepreferably closed to practically fully shut position whereat the contiguous edges of adjacent arcuate vanes partially overlie or-overlap one another inshingle-like arrangement. Indeed, ex-

cellentresults are obtained in operatingthe burner within its lower-most---firing range by closing theregister vanes to a point where substantially only air leakage through the vanesis permitted. By closing thevanes tothis extent, 'sufficient resistance is built up to overcome the natural'direction-al-flow of air aroundthe outer surface's of the scrollnplenumto insure uniform distribution 'a'nd flow of air through the register vanes. In this connection, it is pointed out that if a fixed or set open vane register is employed with a=scroll plenum the fixedvanes'will'not provide sufficient-resistance at low loads or firing rates-to the directional'flow of the 'air around the-plenum t'o 'pr'event substantiallyall "of the air flow from entering the burner through a localized area of the register-such as the one vane openinglo'cate'd at the point of minimum clearance between the register and the volute'walls of' tlie plenum. However, and as above stated, by closing-the adjustable vane register to a point where'only minimum air leakage-ispermitted through the'van'es, s'ufiicie'nt resist-an'ce is built up to overcome the directional flow of the air -and eauseit touniformly enter through a lhinstead of simply one-or several, of the vanes.

A further advantageous and important factor in closing the air-register vanesto a point where' only air leakage is permitted during operation of the burner within its lower-most range is that the overlapped arrange'mentof the vanes imparts a highly desirable swirling motion'to the air'flowing into the "combustion'chamber.

'Moreparticularly, it has been determined from experience that a pronounced swirling motion imparted -to the air willpro'duce and maintain optimum efiiciency between gas and air mix, and it is particularly desirable, of course, to be'able' to 'inaintai'n optimum efficiency betweenfuel and-air mix when the burner is operating in its lowermost firing range, as well as through its upper firing range.

Although, it'might perhapsbeexpected that reasonably satisfactory admixture ofw-gas and -air would be-obtained under theselatteroperating conditions; it hasbeen found,

very-surprisingly; that substantially equally ood: results are obtained in oper-at-ing the unit as #anpil "bu'rn'er.

More'particularly,"it has been found tliat the flov'v cfair entering through throat 27 and into the combustion chamber proper will actually cause the comparatively small conical shaped atomized oil spray injected from nozzle tip 31 to be mushroomed or sucked outwardly toward the truncated conical shaped walls of the burner resulting in intimate intermixing of the oil spray particles with the air stream to insure complete combustion with a minimum of excess air. This mushrooming outwardly of the oil spray and consequent admixture with the swirling air fiow will occur even when the amounts of oil and air being introduced into the chamber have been reduced to such an extent that the burner is operating at or approaching one-tenth of its maximum firing capacity.

Although the present invention has been described in some detail by way of illustration and example for purposes of clarity and understanding, it is understood that certain changes and modification may be practiced within the spirit of the invention as limited only by the scope of the claims appended hereto.

I claim:

1. In a forced air draft oil or gas burner of the type in which air under pressure is supplied to the combustion chamber for intermixing with the fuel to be burned, the combination comprising: a blower assembly for inducing a forced draft of air; adjustable damper means associated with said blower assembly for regulating volume of air flow through said blower assembly; a scroll plenum in communication with said blower assembly; a circular air register for imparting a swirling motion to air discharged therefrom disposed interiorly of said scroll plenum comprising a circular frame; a plurality of vanes pivotally mounted to said frame for movement from a closed position, whereat said vanes lie generally within the line of circumference of said circular frame and with contiguous edges of adjacent vanes overlapped in shingle-like arrangement, to an open position, whereat said vanes are disposed generally radially with respect to said circular frame; said circular air register disposed within said scroll plenum with the clearance between the circular register and the volute walls of the scroll plenum diminishing in the direction of air flow from said blower assembly through said plenum; an entrance to a combustion chamber; said circular air register disposed in coaxial alignment with respect to said entrance; fuel supply means; adjustable regulating means for regulating the fuel supply to said entrance; and manual control means associated with said damper means, said vanes of said circular air register, and said adjustable fuel supply means, for simultaneously regulating proportionate fuel and air supply to said entrance in relation to varying load requirements of the burner concurrently with air register vane control.

2. In a forced air draft oil or gas burner of the type in which air under pressure is supplied to the combustion chamber for intermixing with the fuel to be burned, the combination comprising: a blower assembly for supplying substantially of all combustion air; adjustable damper means operably associated with said blower assembly for regulating volume of air flow through said blower assembly; a windbox in communication with said blower assembly; a circular air register to impart a swirl to air discharged therefrom disposed interiorly of said windbox comprising a circular frame; a plurality of vanes pivotally mounted to said frame for movement from a closed position to an open position to impart varying degrees of swirl to air passing through said register; an entrance to a combustion chamber; said circular air register disposed in coaxial alignment with respect to said entrance; fuel supply means located adjacent said entrance; adjustable fuel regulating means for regulating the fuel supply to said entrance; and manual control means operably associated with said damper means, said vanes of said circular air register, and said adjustable fuel regulat ing means, operable to substantially simultaneously relatively open and close said damper means, said vanes, and said fuel regulating means proportionate to the increase and decrease respectively of the load requirements of the burner.

References Cited in the file of this patent UNITED STATES PATENTS 1,684,079 White Sept. 11, 1928 1,738,176 Dyer Dec. 3, 1929 2,203,553 Thoresen June 4, 1940 2,211,684 Baker Aug. 13, 1940 2,382,913 Robinson Aug. 14, 1945 2,387,280 Mcllvaine Oct. 13, 1945 2,473,347 Sanborn June 14, 1949

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