US2052710A - Combustion control for heating systems - Google Patents

Description

Sept. 1, 1936.

' A. W. HOLMES COMBUSTION CONTROL. FOR HEATING SYSTEMS 2 Sheets-Sheet l hr/zvzzar Filed Aug. 30, 1952 Se t. 1, 1936. A. w. HOLMES COMBUSTION CONTROL FOR HEATING SYSTEMS Filed Aug. 30, 1

Hull 3% 6 r x f f w A n m Patented Sept. 1, 1936 PATENT o-r-rles comUsTioNooN'moL FOR HEATING SYSTEMS Albert w. Holmes, Providence, a. 1. Application August 30, 1932,-Serial No. 631,005' '6 Claims. (01. 110-75) My present invention relates totheheating art,

' and has particular reference to the 'control of combustion of hand fired stoves, furnaces, and boilers.

, Careful study of the combustion of coal in the above hasd'isclosed that approximately fourteen pounds of air must be supplied per pound of coal consumed, and that about one half must be supplied below the grate as primary air, and one half in the combustion space above the fire as secondary air, to ensure complete combustion.

. Complete combustion under usual operating conditions has been found to require an initial or primary combustion, and a subordinate or sec- 5 ondary combustion; the primary combustion occurring on the grate bars and in the fire bed, and

the secondary combustion occurring in the combustion space above the fire bed. Theprimary combustion requires a sufiicientsupply' of air under the gratebars, and a sufficient temperature to" produce the desired combustion; this is obtained by controlling the flow of air intothe ash pit, or'under thegrate bars,-and regulating the rate of gasification of the coal in the fuel bed.

The secondary combustion'r'equires admission of a sufficient supply of air to the combustion'space,

' a thorough mixture of this air with the gases from the fuel bed, sufiicient temperature to complete thecombustion, sufiicient space to permit the-necessary expansion of the gases during the combustion process, and control of the outflow so as to permit the combustion to be completed.

Eficient'furnaceoperation thus requires accurate control of the primary air, the secondaryair, and the speed of combustion; as the combustible gases must'have sufiicient time in'the'firebox for completecombustion. Moreover, the secondary air shouldbe heated, and injected intothe com bustion space 'so as to spread over the fuel bed'and thoroughly mix with the gases ascending from the fuel bed.

It is the principal object of my invention to control the supply of primary air, secondary air, and the speed of combustionso as to obtainmaximum 45 efiiciency; Other objects of my invention are to preheat the secondary air and to inject the secondary air in many small streams over the fuel bed so as to thoroughly mix oxygen with the combustible gases and complete the combustion.

With the above and other objects'and advanta'geous features in view, the invention consists of an arrangement of parts more fully disclosed in the detailed descriptionfollowing, in' conjunction with the accompanying drawings, and more 'spe-' cifically defined in' the claims appended thereto.

' Referring to the drawings,

Fig. 1 is an elevation of a furnace equipped with the novel control; parts being broken away;

Fig. 2 is an elevation of the smoker pipe damper control;

unit;

Fig; 10 is a section on the line ltl'l3 of Fig. 9; Fig; 11 is a section on the line IE'-H of Fig. 10; and

Fig. 12 is a section on the line l2--|2'of Fig. 10.

Referring to the drawings, the furnace i5 is equipped with a fire box unit It for controlling the admission of air to the combustion space of the firebox and for preheating the admitted air,

a damper unit H for controlling the outflow of H the flue gases, and a device lflfor admitting air below the grate. These units are adapted to be operated in unison by manual movement of a ratchet typecontrollever l9, which movement is communicatedto the 'units by means of chains or the like 28,2! and 22; counterweights 23, 24, and 25 are attached to the chains, in the usual manner, to normally hold the units in closed position.

The damper unit is illustrated in Figs; 2 to 4, and includes a casting 26 which is adapted to be mounted in the smoke pipe and is provided with side bosses to which a pivot stud plate 21 and a bearing plate 28 is secured, as by screws or bolts;

the damper 29 having a recess 39 to seat over the stud of the plate 21 and having an operating shaft 3| extending through the bearing plate, an operating handle 32 being secured'to the end thereof.

The bearing plate 28 is preferably formed with a guide quadrant 33, graduated in degrees, and having stops 3 3 at each end, whereby move ment of the operating handle sets the damper at the desired degree of opening, a stop 35 being provided for the damper to prevent complete closure.

The smoke pipe device or damper unit is fur ther provided with a draft control opening 36 contrblle'd by aslide' plate 31' which is slidably mounted on a guiderod 38"seated at its 'ends in end socket stands '39 secured" to suitable bosses of the casting or smoke pipe 25. v The plate 31 is shifted'by pressing two levers 40' which are pivotally mounted-on the platetowards each other, the levers being spring pressed away from each other by a spring 'd Land having-pins 52- at their inner ends adapted to contact the rod 38 when released. r

The operation of the damper unit may now be explained. Movement of the operating handle sets the main damper to the degree of opening, and movement of the slide plate 31 controls the stack draft, and hence the speed of combustion in the fuel bed. The. parts are designed for simplicity of operation, are easily assembled, and cannot get out of order under normal operating conditions. i

The fire box device is shown in Figs. 5 to 8, and includes an air admission unit 43 andan air preheater unit 44, the two being secured in align therethrough, an inlet, a fan shaped nose having ment to the fire, box door. The air admission unit includes a base 45 having a central outlet 46 and spaced air flow slots 41, an inlet shell 48' being secured to the base, as by a central screw, and having air admission openings 49; a control valve 50 of plate type is rotatably mounted on the base between the base and the inlet shell, and has slots 5| adapted to uncover-the slots' l'l in response to movement of the valve 50. The valve- 56 is shifted by movement of ,a'handle 52, which also functions as a pointer and cooperates with a scale 53 mounted on the base and graduated in degrees; limit stops are provided for the valve, the preferred type including a pin 54 seated in the base and cooperating recesses or notches 55 in the valve59. q.

The ash pit air admission unit 18 is in'this instance similar in construction to the fire box air admission unit, but is larger. The operationv is identical, the valves being rotatedmanually by movement of the handle, or by securing the operating chain to the handle in any desired and suitable manner, the rotation of the valve uncovering the flow slots tothe desired number of degrees as indicated on the scale and regulating the air inflow in accordance. 1

The air preheater unit is illustrated in detail in Figs. 9 to 1 2, and comprises a casting 56 which extends into the furnace combustionchamber and through which the air 'isconveyed in a tortuousmanner before emerging from a fanshaped nose provided with many outlets or. jets-.:

The casting has vertical flues or: passages 51' through which the hot furnace gases may readily circulate, and has an air inlet 58 whichcommunicates with the upper portion, see Figs}? and 11,

the air passing between'the flues 5'! over the 'central partition 59 to the forward end, and back along the outer sides, then down as shown inFig. 10, and around the flues 5! to the outlets 60 which as shown are drilled'to produce sharp edges to ensure maximum velocity of the air passing into the combustion space and are arrangedafan shapeto distribute the heated air overthe entire fire box. The air'preheater unit is preferably cast in two parts 6!, ,62, see Fig. 10, to simplify manufacture.

The operation of the air preheater is as follows:

the admitted air is subjected tothe fire box heat. 7

in its tortuous passage, being initially heated along the upper portion, and then along the lower portion where it is exposed to the direct heat of the fire: the constant passing of the hot gases through the vertical flues 'orpassages facilitates transfer of heat from the hot gases to the air.

It is therefore evident that the novel construction provides an accurate control of the supply of primary air, an accurate control of the supply of secondary air, the secondary air being heated andjspread over the coal bed, and an accurate control of the velocity and volume of the outflowing flue gases, whereby the control of combustion is more exact, and the amount of excess air and the resultant heat loss is reduced to a minimum. 7

While I have described a specific constructional embodiment of my invention, it is clear that changes in the arrangement, proportions, and relative size of the parts, may be made to suit the requirements for particular installations without departing from the spirit and the scope of the invention as definedin the appended claims.

I claim:

1; An air preheater having a flue extending extending therethrough, a partition transverseto' said flues dividing the interior into an upper and a lower portion, an inlet communicating with the upper portion at one end, a plurality of outlet openings in the lower portion at the other end, and partitions for guiding the air passing into the upper portion between the flues to the other end, back around the flues to the entrance end, and into the lower portion to again pass through and around the flues to the outlet openings;

3. An air preheater having a plurality offlues extending therethrough, a partition transverse to said flues dividing-the interior into an upper and alower portion, an inlet'communicating with the upper portion at one, end, the other end being formed as a fan shaped nose having apluralityof outlet openings to spread'the outflowing air in a wide area, and partitions for guiding the air passe having a plurality of flues extending there-.

through, said air preheater having an inlet jcom'-. inunicating with said. flow'oontrol: opening, a partition transverse to said fluesdividing'the'interior into an upper and a lower portion, theinlet. communicating with the. upper portion at one end, a plurality of outlet openingsrin the lower portionat the other end, and partitions for guiding the airpassing into the upper portion between the flues tothe other end, back around the flues to the entrance end, andinto-the lowerportion to again pass through and around the flues to the outlet openings.

5. An air'preheater having aflue extending therethrough, an inlet, a plurality of outlet openings, and partitions directingthe flowing air in a tortuous passage 'aboutsaid flue to-s aid outlet openings, the cross sectional area of said tortuous.

- passage progressivelyincreasing towards the outlet openings.

6. An airpreheaterhaving two flues extending therethrough, an inlet, a plurality of outlet ope'n-. ings, andpartition means guidingthe flow of air between the flues forwardly from said inlet, then backwardly around the flues, then forwardly between and around the fluesto said outletopen-

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