Title:
Draft control
United States Patent 2151642


Abstract:
This invention relates to a method and apparatus for controlling drafts for solid-fuelburning furnaces within predetermined limits. The majority of such heating apparatus or furnaces, especially those used for domestic purposes, depend upon natural draft for proper combustion of the fuel....



Inventors:
Rose, Harold J.
Application Number:
US7854936A
Publication Date:
03/21/1939
Filing Date:
05/08/1936
Assignee:
Philadelphia, And Reading Coal
Primary Class:
Other Classes:
110/147, 122/30, 126/73, 126/112, 126/293
International Classes:
F23L11/02
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Description:

This invention relates to a method and apparatus for controlling drafts for solid-fuelburning furnaces within predetermined limits.

The majority of such heating apparatus or furnaces, especially those used for domestic purposes, depend upon natural draft for proper combustion of the fuel.

This natural draft when furnished by a chimney or stack is highly variable and depends upon a 0 great number of factors such as the composition, temperature, and volume of the products of combustion, the temperature and humidity of the outdoor air, and the velocity and direction of wind. By reason of the variability of conditions, 5 uncontrolled natural draft is not satisfactory for year round operation, especially when used for automatically regulated heaters.

One object of my invention is to maintain natural draft available for immediate use by the :0 heater at any time within certain predetermined limits.

Further objects of my invention are to supplement natural draft when necessary, utilizing excess heat from the heating apparatus, to release I5 or diminish excess draft, and to prevent down drafts or negative drafts from reaching the fuel in the heater.

Since combustion gases are somewhat heavier than air at the same temperature due to their high 0 content of carbon dioxide, it is necessary to maintain these combustion gases at a relatively high temperature in the chimney in order to create a natural draft. This is rather difficult to do in certain seasons, especially if the chimney 5 becomes damp by reason of rains or moisture condensation.

In accordance with my inventi6n I therefore provide means for passing heated air into the chimney which has the dual effect of reducing 0 the density of the combustion gases, and increasing their drying power. This tends to maintain the chimney warm and dry at all times and the desired draft is thus always available for immediate use.

5 Wind direction and velocity are also important factors and may very materially affect the amount of draft available even though the chimney is maintained warm and dry. If the wind produces a lower pressure at the top of the chimney 0 than at the bottom thereof, excessive draft will be created and therefore a further object of this invention is to automatically by-pass cold air into the chimney when such excessive draft is created. Wind may also create a pressure at 5 the'top of the chimney and cause down drafts and it is, therefore, also preferred to provide an automatic release for such down drafts before they reach the heating apparatus.

The smaller the heating apparatus, the greater difficulty is normally encountered with draft con- a ditions and my invention therefore finds particular application to small domestic heating devices such as those used for burning solid fuel to heat water. My invention is also particularly applicable to and has special advantages when employed in combination with heating apparatus such as shown and described in the co-pending application of R. Johnson, Serial No. 64,835, filed February 20, 1935.

The foregoing and further objects and advantages of this invention may be better understood from a consideration of .an embodiment thereof illustrated in the drawings, in which the figure illustrates a vertical cross section of a domestic water heater of the solid-fuel-burning radiation type.

In the drawings, numeral I indicates a shell which may be of a cylindrical or other shape and defines a fire-pot of a solid-fuel-burning furnace.

Solid fuel may be supported upon the grate 2, which may be of any suitable construction for allowing a combustion medium, such as air, to pass upwardly therethrough. This grate may be supported in any desirable manner, as by an arm 2a. Fuel is preferably fed to the fire-pot, as defined by the grate 2 and the shell 1, through a magazine indicated generally at 3. This magazine comprises a storage compartment 3a above the shell I and is preferably provided with inwardly sloping side walls 4 and vertical dependIng walls 5 for directing the fuel into the fire-pot.

The magazine should be tightly closed as by the lid 6, having a handle 7.

Spaced from the shell I, and surrounding the same, is a jacket made up of an outer wall 8 and an inner wall 9 designed to contain the water 10 to be heated. An inverted frusto conical section II, and an annular member 12 are positioned to cooperate with the shell I in defining a closed air space 13 between the shell I and the wall 9. The outer fluid-containing jacket and the magazine are preferably provided with a heat insulating layer 14 which may be of some relatively non-conducting material or provided with a reflective outer surface as is understood 5O in the art. Water to be heated is supplied to the outer jacket by pipe 15 and the heated water is drawn off through the pipe 16.

Air for combustion may be supplied to the ash pit 17 and grate 2 by means of the opening 18. The ash pit II is preferably provided with a section 20 of suitable shape to cooperate with a tightly fitting door 21 provided with a locking handle 21a. Suitable means may also be prbvided for shaking the grates 2.

The top of the shell I is preferably spaced from the lower end of the depending wall 5 a sufficient distance to allow the products of combustion from the fuel to pass out through the opening 22 to a pipe 23 which leads to the flue or stack. The lower end of pipe 23 communicates with the air space 13 by means of an extension 24 and may be suitably reinforced and held in place by the tie-rod 25. Air supplied to the space 13 by way of an opening 26 is preferably deflected to circulate through the air space by the baffle 21.

The passage of combustion air through the fuel and the passage of air through the space 13 are both regulated by a single valve member 28 which may be pivoted about a rod 29 and positioned near the juncture of the pipes 22 and 23.

In one position the damper 28 rests upon the supporting stud 30 and substantially closes the passage leading from the air space 13 to the flue. A small opening 31 may be provided in the damper to allow continuous flow of a minimum amount of air or products of combustion at all times. When the damper 28 is swung to the other extreme position, the opening 22 is substantially closed and the fire is effectively checked.

Suitable handle or other means may be provided on the shaft 29 for the operation of this valve member.

To provide for the release of gases from the pipe 23 when a condition of down draft is creSated I provide the damper 32, which may be mounted on the rod 33 for pivotal movement.

Suitable weighting means 34 is preferably provided to susbtantially balance this damper on the rod 33. Under conditions of positive draft, 40 the lower end of the damper is held against the stop 35 and is thus maintained closed. When the draft is reduced to zero or a condition of down draft is created, this damper will automatically open and allow air rushing down the 45 chimney and into the pipe 23 to escape into the room.

In order to take care' of and reduce excess drafts, the damper 36 is pivotally mounted on the rod 31 and suitably weighted by means of the 50 weight 38 so that under all normal conditions it remains in a vertical clos9d position. When excessive drafts are created, however, the lower portion of this damper will swing inwardly, allowing cold air from the room or cellar to pass up into the stack and reduce its temperature. This damper also serves to relieve the fire'immediately of excessive draft and since it swings into the flue, it functions to throttle the flow of gases from both the openings 22 and 24.

The operation of the heating apparatus is generally similar to that described in the application of Raymond Johnson Serial No. 64,835, filed February 20, 1936, and heat is transferred from the solid fuel in the fire-pot I to the water 10 principally by radiation.

My invention is designed to particularly take advantage of the air space between the water 0 jacket and the shell I and to utilize air heated by passage through this space to maintain the flue and chimney in a warm and dry condition.

While in the embodiment of my invention illustrated the air is heated by both the fire-pot and the water jacket, it is evident that the excess heat may be extracted from either the fire-pot or the fluid being heated alone.

Draft regulation In accordance with my invention has especial advantages when used in combination with a radiating solid-fuel heater.

For example, the withdrawal of heat from the space 13 and discharge of heated air to the stack when the fire is checked assists the thermal valve action of the radiation heater by immediately cooling the outer or radiating surface of the shell I. Thus, when the fire is on draft and the damper 28 rests on the stud 30, only a minimum amount of heat is withdrawn from the air space 13, the bulk of it being transferred to the water 10. As soon as the fire is checked by moving the valve 28 to the other extreme position, the flow of cold air in through the passageway 26 and the withdrawal of heated air through the passageway 24 facilitates the thermal valve action of the radiation heater by quickly cooling the radiating surface and preventing the water 10 from becoming overheated. Overheating or what is known as overruns are effectively eliminated where my improved draft regulation is applied to a radiation heater.

The net result of this improvement when the fire is banked is that the fire is not caused to burn faster than necessary to supply hot combustion gases to the chimney with the attendant overheating of the hot water. After a heater has been operating at high capacity for some time and the fire is checked the surplus heat is usefully applied to maintaining the chimney draft and preventing it from overheating the water.

The use of heated air to maintain chimney drafts in general as compared with heated combustion products is especially advantageous because tests have shown that the combustion gases from anthracite coal must be, heated as much as 40° F. hotter than air to give the same draft effect.

The two valves 32 and 36 have a special utility in combination with a heater embodying my invention, since the combination provides an effective control and maintenance of available draft at all times within predetermined limits and under all possible conditions. When the fire is on draft it is desirable that some air be drawn through the space 13 and passed to the chimney since this has the action of supplementing the heat of the products of combustion and of decreasing their density and also reducing the tendency for moisture to condense in the chimney.

For the reasons discussed above, I have found that it is distinctly advantageous to correlate the flow of primary air for combustion with the flow of heated air to the stack.. Any suitable means may be employed for this purpose either at the outlet from the furnace as shown, or at the inlet as in openings 18 and 26.

However, it is to be distinctly understood that my invention is not limited to such features but individually controlled dampers may be employed at any available positions in the system. For example, individual manually operated dampers may be employed in the openings 18 and 26, or in the openings 22 and 24, or in the openings 22 and 26, or even at all four positions.

The terms and expressions which I have employed are used as terms of description and not of limitation, and I have no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invention claimed.

No claim is made herein to the particular construction of the damper 28 illustrated in the drawing, since this feature is claimed in the copending application of Hilmar R. Hagen Serial No. 193,838, filed March 4, 1938.

I claim: 1. Heating apparatus comprising a fire-pot for burning solid fuel, means for confining a liquid medium to be heated in a position spaced from a wall of said fire-pot and arranged to transfer heat from said fire-pot wall to said confining means principally by radiation, means for admitting air to the space between the fire-pot and said means, and means for conducting heated air from said space to a stack 2. Heating apparatus comprising a solid-fuelburning fire-pot, means confining a fluid medium spaced therefrom and arranged to be heated principally by radiation, means for admitting primary air to said fire-pot for combustion of fuel therein, means for admitting air to the space between said fire-pot and confining means, a conduit for conducting products of combustion to a stack, means providing the only outlet from said space for admitting regulated quantities of heated air from said space to said conduit, means for introducing cold air into said conduit when the draft therein exceeds a predetermined amount, and means for allowing a gas to escape from said conduit when a positive pressure is created therein.

3. In a solid fuel burning water heater, a firepot for burning solid fuel, a water jacket laterally spaced from and arranged to receive heat from a wall of the fire-pot principally by radiation, means for introducing primary air into said fire-pot to support combustion therein, means for passing controlled quantities of products of combustion from said fire-pot to a stack, means for introducing secondary air into the space between the fire-pot and jacket in heat exchanging relationship with said water jacket, and means for passing regulated quantities of said heated secondary air to said stack when the fire 4 in said fire-pot is checked.

4. A method of maintaining a stack warm and dry to provide efficient natural stack draft for a solid-fuel-burning heater comprising, flowing primary air through a bed of fuel for combustion thereof in said heater, flowing additional air into heat exchanging relation with said fuel but out of contact therewith, passing the products of said combustion and the additional heated air to said stack, and regulating the flow of " said products of combustion and heated air to the stack to amounts Inversely proportioned to each other so that said-heated air supplements the effect on the stack draft of said products of combustion when the flow of the latter is reduced or checked.

5. A method of maintaining a stack warm and dry to provide an efficient natural stack draft for a solid-fuel-burning water heater compris6 ing, flowing primary air through a bed of fuel for combustion thereof in said heater, flowing additional air into heat exchanging relation with said fuel and said water out out of contact therewith, passing the products of said combustion and the additional heated air to said * stack, and regulating the flow of said products of combustion and heated air to the stack to amounts inversely proportioned to each other so that said heated air supplements the effect on the stack draft of said products of combustion when the flow of the latter is reduced or checked.

6. The method of maintaining efficient natural stack draft available for a solid-fuel-burning heater in which a confined fluid medium is heated principally by radiation of heat from a fire-pot wall across an air space comprising, flowing primary air through said fire-pot for combustion of fuel therein, flowing additional air into heat exchanging relation with said fuel but out of contact therewith, passing the products of said combustion and the additional heated air to said stack, and regulating the flow of said additional heated air so that substantial quantities thereof are passed to the stack to supplement the effect of the products of combustion on the stack draft only when the flow of the latter is reduced or checked.

7. The method of maintaining efficient natural stack draft avilable for a solid-fuel-burning heater in which a confined fluid medium is heated principally by radiation of heat from a firepot wall across an air space comprising, flowing primary air through said fire-pot for combustion of fuel therein, flowing additional air through said space in heat exchanging relation with said medium and the fire-pot but out of contact with the fuel, passing the products of said combustion and additional heated air to the stack, and regulating the flow of said heated air to increase the amount thereof when the flow of products of combustion is reduced or checked.

8. The method of maintaining efficient natural stack draft available for a solid-fuel-burning hot, water heater in which the water is heated in a jacket principally by heat radiated laterally thereto across an air space from a fire-pot wall comprising, flowing air through the firepot for combustion of fuel therein, flowing a stream of additional air through said space, passing the products of said combustion to the stack, and passing said heated air to the stack when the flow of products of combustion is reduced or checked to remove excess heat from the heater and to supplement the effect on the stack draft of the products of combustion.

9. Apparatus for heating comprising a jacket for containing a fluid medium to be heated arranged to define a substantially vertical central opening, a fire-pot for burning solid fuel disposed wholly within said opening, said fire-pot having a wall spaced from said jacket, said jacket being constructed and arranged so that heat received by said jacket from said fire-pot is transferred thereto from said wall principally by radiation, and means for passing a stream of air through the space between said wall and Jacket and thence to a stack when the fire in said fire-pot is checked.

10. Apparatus for heating comprising a jacket 05 for containing a fluid medium to be heated, means for introducing and removing fluid from said jacket, means including walls spaced laterally from said jacket for defining a solid lump fuel burning fire-pot, said jacket substantially enclosing the heat radiating surface of said walls and being constructed and arranged so that heat received by said jacket from said fire-pot is transmitted thereto principally by radiation from said walls, means for flowing a stream of air to be heated through the space between said 70 walls and jacket, and means for passing said heated air to a stack in amounts proportioned inversely to the amounts of combustion products passed to the stack.

HAROL J. ROE K