US1978518A - Method of combustion - Google Patents

Description

ct. 30, 1934. A. u. WETHERBEE 1,978,518

METHOD OF COMBUSTION Original Filed Jan. 15, 1927 2 Sheets-Sheet l Oct. 30, 1934. A, U WET ERBEE 1,978,518

METHOD OF COMBUSTION Original Filed Jan. 15, 1927 2 Sheets-Sheet 2 Mir Patented Oct. 30, 1934 a r 1 97 518 METHOD OF COIWBUSTION Ashur U. Wetherbee, Evanston, 111., assignor to Autogas Corporation, Chicago, 111., a corporation of Delaware Original application January 15, 1927, Serial No. 161,296.. Divided and this application July 13, 1931, Serial No. 550,452

6 Claims. ((31. 158117.5) I

My invention relates to means for burning users reduce the pressure at the outlet to such gaseous fuel for the production of heat for heatan extent that unsatisfactory combustion results. ing homes. This application is a division of my According to one phase of my invention I copending application, Serial No. 161,296, filed overcome this difliculty of pipe friction by em- January 15, 1927. ploying a positive metering and feeding device,

It is intended that the burner of my invention that is, a device which, by suction, draws the shall be applied to any suitable heater, such as is gas from the main and compresses the same in employed in house heating as, for example, a predetermined quantities, so that the variations hot air furnace, a hot water heater, or a steam of pressure in the main do not disturb the 10. or vapor boiler. efficiency of combustion, nor in fact, the rate of The heating of houses, garages, and such like combustion. detached buildings which do not conveniently I provide, in addition to the above, means for support expert firemen and burn fuel on a large maintaining the delivery pressure substantially scale could, theoretically, be best performed by constant; that is, the delivery pressure of either 5 burning gas since it is at once cleanly and 0011- the gas or the air, or the mixture of gas and air, venient and easily controllable. and provide means for varying the size of the The great difiiculty heretofore has been that mass of incandescent material simultaneously the cost of burning gas in furnaces of the known with the variations of de ve y for example, construction has entailed too great an expense. in accordance with thermostatic regulation.

29 I have conceived the possibility of employing the Where there is likelihood of relatively great fuel in the most efficient form commercially u u t i th as r a pr ssure, I propossible, so as tominirnize the objection of high vide re ulati ans n the i tak sid of the cost of gaseous fuel. It is a well known fact f din d v s t u a t at f ai infl w that the transmit of heat. from the fire to a np opo t n to the rate of gas fl we air 'heated surface is performed more efiiciently if is p e y introduced into the burner y a the heat can be applied in the form of radia t, positive feedingdevice which is driven in unison energy as distinguished from heating a current or synchronously with the gas feeding device and of air and then transferring the heat of the air s P a y 0f t Same yp that the w to the surface, as by convection. Since air is a, str ms, namely, gas and air, are delivered under 30 poor conductor of heat at b t, a d in it, ha pressure to a mixing device and thence conveyed low specific heat, the passing of large quantities to the burner! of air thru a furnace is highly undesirable. I In the connection between the mixing device have, therefore, employed the type of combustion and theburner I interpose a flame arrester in known as surface combustion in which the heat order to prevent the flame from striking back 35 of the gaseous fuel is developed mainly in the from the burner when theme is shut olf. form of radiant energy and I employ only o This flame arrester should preferably be much air flow as is nece sary i support placed'as close as possible to the burner so that b sti In th usual pen a type of a minimum disturbance will be created when the bustion a large amount of excess air is perfire 135mm 011,- I mayembody the flame 40 tt t pass thru the fu and it carries roster in the valve which controls the extent of a large amount of heat out the stack. This loss incandescence the refractory mass is greatly reduced in surface combustion Where f gntenpg from the.nozz.le of the burger the amount of air used is intended to be only may be lgmted elther by pllqt hght hot wlre' sufficl-ent to support combustion or by a spark plug embedded in the mass of re- So far as I am aware heretofore surface comfractory' bustion has not been employed in an off and on further feature of my mventlon Ijesldes in type of burner and in f t f having the air and gas come together n such a ac alias I a aware manner and at such location as to maintain at no means for varylng the effective slze of themass f d 1 M all times a minimum of combustible mixture. been. gevjlsnectn escent leflactory has heretofore This is highly desirable to prevent explosion by I back firing, or from any cause at all; I find I1 Supplylng 25 36 5 uel to burners of this that even with interposed flame arresters it is kind there is the distribution difficulty which has diflicult to prevent back firing when the burner heretofore been encountered and that is that, is stopped and started. Hence, there is the de- 55 u t0 D pe friction, heavy, demands by. many. sirability ofmixing the gas and air as closeto the point of burning as possible to lessen the volume of mixture, and also by mixing the gas and air within the confines of the furnace any slight popping noise which might arise from such back fire will be masked.

In order to acquaint those skilled in the art with the manner of constructing and operating a device embodying my invention, I shall describe in connection with the accompanying drawings a system in which my invention ap-- pears.

In the drawings:--

Fig. l is a side elevationalview of a system embodying my invention showing a hot air furnace partly in vertical section.

Fig. 2 is a vertical section on an enlarged scale showing the burner of Fig. 1.

Fig. 3 is a vertical section on an enlarged scale showing the gas and air mixer in vertical section.

Fig. 4 is a fragmentary vertical section of the bottom part of the burner showing a modified form of valve and flame arrester.

Fig. 5 is a similar fragmentary section of an automatic regulating valve for the nozzle of the burner.

Fig. 6 is a diagrammatic view similar to Fig. 1 showing a thermostatic control for simultaneously controlling the delivery of the gas feed device and the air feed device and the regulating valve for the burner nozzle.

Fig. 7 is a transverse vertical section through one of the feeding devices or pumps showing the regulating means for regulating delivery.

Fig. 8 is a diagram illustrating the control valve between the gas line and the air line running to the feeding device.

Referring now to Fig. 1, I provide a hot air furnace 1 having a suitable air space 2, the interior of which is defined by the inner furnace wall 3, which Wall is adapted to be heated by the burner 4 and the products of combustion escaping therefrom. The hot air space 2 communicates by way of a delivery pipe5 with the regis-' ters of the house thru suitable pipes or trunks controlled by regulating valves, such as 6 and '7. Air to be heated enters by way ofthe pipe or trunk 8. The burner 4 is provided with a vent space 9 below the same and the outlets 10 to the stack or chimney 11 are located preferably at a level considerably below the burner 4. The burner 4 comprises preferably a metal shell 12 in the general shape of a bowl or the like having a lining 13 of plastic refractory material and a mass 14 of broken refractory material or refractory bodies within which mass the combustion of the mixture of as and air is carried on.

The bowl 12 has a distributor nozzle 15 projecting into the mass of refractoryl l, this nozzle being in the nature of a tunnel preferably disposed in a vertical direction with a plurality of nozzle openings 16 communicating with the interior 17. Preferably, the character of the mixture as delivered to the nozzle 15 is such that complete combustion is carried on in the mass of refractory 14 a short distance below the surface of the same. That is to say, with a given delivery pressure and the proper velocity thru the nozzle 15, the upper nozzle openings lfiiwill deliver the combustible mixture into the mass M in such a manner that the flame remains Within the mass of refractory.

Now it will be observed that the nozzle 15 isof tubular form with a rounded or semi-spherical ;upper end and the nozzle cpenings may extend over substantially the entire outer surface of the same. Ihese nozzle openings are preferably packed with fibrous refractory material disposed in dovetail openings in the surface of the nozzle 15. A combined valve and flame arrester 18 is arranged within the nozzle 15 in such a manner that by raising this member 18 the lower nozzle openings will be closed off to limit the amount of refractory material in which the flame occurs. When the valve member 18 is lowered the lower nozzle openings 16 are uncovered and delivery of combustible mixture thru them occurs, with the result that the zone of refractory material in which combustion occurs is increased. In other words, the valve 18 regulates the delivery of the combustible mixture in such a manner that for small flame only the central part of the mass of refractory material 14 is heated to maximum temperature, and for a larger fire the flame of the burner is increased to heat a larger amount of the refractory material in a lateral direction. Hence for variable delivery, assuming a substantially constant pressure, the amount of refractory material which is included in the flame is regulated.

It will be seen that by this means a minimum loss of heat occurs since a small flame means that only a small part of the refractory is heated to incandescence, but that is close to the surface so that the heat may be transferred to the furnace walls by radiation directly.

Since it is an important part of this invention to convert as large a proportion of the heat of combustion to radiant heat as is possible, and since the heat radiated increases in quantity faster than the increase in temperature, it is desirable to have a small area at a high temperature, rather than a larger area at a lower temperature.

I believe that this manner of regulating sur face combustion is broadly new. Heretofore, so far as I am aware, the nozzle opening has been fixed with the result that variations in rate of delivery have prevented the maintenance at incandescence of a mass of refractory proportional to the rate of delivery. The theory of surface combustion includes the idea of burning the mixture at the point where the rate of flame propagation is substantially equal to the rate of mixture flow.' Herc-tofore, vhen the rate of mixture flow has decreased the flame has gone down into the mass of refractory, and if the flame has not been sufficient to maintain the entire mass incandescent, the incandescent zone has traveled down inside of the mass of refractory with the result that the desired effect of transmitting the heat by radiant energy has been, to a large extent, defeated. Consequently, heretofore, it has been the desire to hold the delivery constant and at such a point that the zone of incandescence was substantially at the surface of the mass of refractory, so as to secure a maximum of radiant energy. By my scheme I maintain the delivery substantially constant in pressure but not in volunle and, as a result, I maintain incandescent a mass of material adjacent the surface of the burner so that a maximum of radiant energy may be developed, and when the amount of mixture delivered is increased I increase the zone of incandescence aiming always to keep the flame so disposed that the zone of incandescence will not travel up and down, but laterally.

I pack the interior of the valve member 18 with metal W001, may employ a mass of metal screen, to form the flame. arrester 19. As shown in Fig. 2, thevalve member 18 is. moved up and down by means ofa ratchet pinion 20, this pinion beingmounted on ashaft which extends out laterally to a suitable hand wheel, not shown. This hand wheel may be disposed outside of the furnace if so desired. i

In Fig. 5 I have shown automatic means-for controlling the valve member 18', this means comprising a diaphragm 21 connected to the stem 22 of the valvemember 18 and arranged to vary the position of the valve member'18' in response to the delivery pressure of gas entering thru the delivery pipe 23.. The diaphragm 21 is loaded by a spring 24, the pressure of which is varied by a regulating screw 25. By this means the combined area of the nozzle openings 16 is so regulated as to maintain the delivery pressure onathese nozzles substantially constant and to thereby vary the number of. such nozzle openings. to correspond to the amount of mixture which is delivered to the nozzle.

The valve 18, shown in Fig. 2, may be actuated in unison with the means which controls the output of the gas and air feeding :devices, aswill be. explained more fully in connection with Fig. 6.

The gas and air. are delivered by, a motor driven outfit which comprises the gas feeding device 27 and the air feeding device 28. These pumps 27 and 28 are driven by an electric motor 29, preferably directly connected to each other and to the motor, and they comprise preferably eccentric vanepumps or equivalent devices such as Root blowers, which deliver with great accuracy predetermined quantities of gas and air. The gas is supplied from the gas main thru a pipe 30, which pipe leads to the suction side of the pump 2'7. The gas is delivered thru olelivery pipe 31 to the gas and air mixer 32. Air is delivered from the pump 28 thru the pipe 33 which also leads to the mixer 32. Since the pump 2'7 draws fromthe gas main by suction and delivers at, a pressure above atmospheric the variations in gas pressure are-relatively inconsequential. I find," however, that I can regulate the air supply in accordancewith the. intake gas pressure by means of a control. valve, such as is shown in Fig. 8. In this case the gas pipe communicates with a diaphragmchamber having a diaphragm 35 and the. diaphragm in turn controls an air control valve 36, which is preferably of the balanced pressure type, to regulate the flow of air to correspond to the flow of gas to the respective feeding devices, The air pipe .3? leads to the suction side of the air pump 28. The. diaphragm 35 is connected by a suitable stem 38 to the stem of the air valve 36. diaphragm 35 is controlled by a control spring 39 which is adjustable by means of anadjusting screw 40. It will bev seen that if pipe 30 is put under suction the diaphragm 35' moves to the left, asviewed in Fig.2 8, tending to close the.

The

F'Ihe gas mixer 32 comprises agenerally cylindrical body having an outer shell 42 and an inner shell 43concentric with the same. The gas is delivered into one end of the inner shell 43 and the mixture of gas and air is discharged out of the opposite end to the burner 4. The inner shell 43 is perforated by pushing in lips or vanes which have the effect of breaking up the gasfiow and also of introducing the air in a generally diagonal direction. The vanes 44 may be disposed in a circumferential direction to give the resultant flow of gas and air a spiral mixing effect. The two sleeves are joined by generally conical heads 45 and 46. Air is delivered by the air pipe 33 into the space between the two sleeves 42 and 43. The mixer 32 is preferably disposed as closely adjacent the burner 4 as possible in orderto decrease the amount of mixture which may be containedin the system when the burner is shut off. The air and gas connections may be reversed.

. In Fig. 6 I. have shown a system in which the deliveries of the pumps varied. V

The pump 28 is shown in section in Fig. 7. It

comprises an outer shell or casing 47 having inlet anddelivery ports 48 and 49, respectively. A rotatable drumror impeller 50 has a series of sliding vanes 51 therein, these vanes being of substantially the .width of the casing and being adapted to slide in and out in slots formed in thedrum 50, as' is well understood by those skilled in the art. The drum50 has a driving shaft mounted in a bearing concentric with the shell 47. Within the shell 47 there is an eccenric cylinder 52 which has suitable ports for intake and delivery, said cylinder being connected to a regulating lever 53 and being supportedgin the casing 47 so that angular movement of the lever 53 varies the eccentricity of the drum 50, with respect to the working cylinder 52. By this means'the displacement of the pump is controlled. The shaft 51 of the pump 28 is connected to the shaft 54 of the gas pump 2'7; The .two shafts in turn are connected by means-of a pair of flexible couplings 55 to the motor shaft of the motor 29. The two pumps are simultaneously varied, as to delivery, by means of a common yoke or connecting member 57 which is connected to the arm 53 of the air pump 28 and to the arm 56,01 the gas pump 27. This yoke member 57 is suitably guided to insure the-same degree of angular motion of each of said arms so as to control the two pumps together. The yoke 57 is connected to a lever 58 pivoted to a stationary pivot at 59, the other end of said lever 58 being connected to a valve operating lever arm G l-for controlling the valve 18 of the burner nozzle 15. The housing of the valve 18 has'an extension 62 in which is mounted a rock shaft 63, said rock shaft being connected to the lever arm and having a valve operating arm or arms 64 for raising and lowering the valve 18. The levers 63 and 58 are connected by a link 65 so that simultaneously with decrease in the delivery of the air and gas feeding pumps the nozzle valve 18 is shifted to decrease the size of the fire in the burner 4.

The arm 60 is adapted to be controlled either by automatic or manual means so as to regulate theamount of heat generated by the burner. I

have shown the lever 60 as "connected by a linlr 66 with the diaphragm 6'7 of a temperature sen- V sitive unites-winch has a tube 6.9 of relatively are simultaneously small bore extending throughout the building or portion of the building to be heated.

Instead of using the valve 18 to regulate the number of nozzle openings which are active in the nozzle 15, I may permit the fire within the mass of refractory 14 to move in and out if so desired. That is to say, the means for controlling the output of the two pumps in unison may be synchronized with the control valve 18 for the nozzle, or may be independent. As shown in Fig. i, I may employ merely a control valve '70 at the burner nozzle 71 for regulating the back pressure according to delivery to maintain substantially constant pressure on the mixer and on the deliveries of the pumps for the pur pose of minimizing the variations of intake pressure. In this case the valve '70 controls the port 72 in the bottom of the bowl 12 of the burner, the position of the valve being determined by a rocker shaft '73, and arm 7 1 connected thru a linkage to the valve stem 75. The rocker shaft 73 may be connected by suitable linkage to the lever 58 which controls the delivery of the feeding pumps in any suitable manner. The distributor nozzle 71 may be omitted, the refractory material serving to cause distribution. This is satisfactory only if the delivery velocity is substantially constant. In this form of the burner I have shown the fiame arrester, comprising metal wool 76, as disposed in a pocket over the end of the mixture delivery pipe 23 so that the flame cannot strike back thru the pipe 23. The metal wool '76 is introduced thru an opening 7'? in the bottom of the housing '78, which opening is thereafter closed by means of a plate or plug.

In the operation of the burner as above described, I preferably employ two controls. One control is the so-called off and on control; namely, a thermostatic control which stops the electric motor 29 when the temperature of the space to be heated attains the desired maximum. Such a system of off and on control requires, in addition, means for igniting the mixture when the burner is to be started.

I have shown in Fig. 2 two devices for igniting the mixture, the first of which is the spark plug disposed in the mass of refractory material a point sufiiciently remote from the nozzle 15 that the velocity of the gas may be relatively low so that ignition is easily accomplished.

It is highly desirable to ignite the mixture as soon as possible in order that no appreciable amount of combustible mixture escapes above the mass of refractory 14 and I have, therefore,

disposed the spark plug 80 within the confines to the nozzle 15 since the velocity of the gases at this point is relatively high and ignition is not accomplished with the same degree of certainty as if it is placed further away. However,

there is the advantage in placing the spark plug quite close to the nozzle 15 in that the flame then occurs beyond the spark plug tending to keep the spark plug cool and prolonging the life of the same. I consider it broadly new, however, to place the ignition device within the mass of refractory since it performs the useful result of obtaining ignition before the escape of combustible mixture outside of the mass of refractory.

If desired, a gas pilot may be employed to the same purpose, but instead of placing the flame directly within the refractory where it might be blown out by ignition of the combustible mixture, I dispose the pilot burner 81 in a tube projecting thru the bowl l2 and having an upper end made preferably of a lava or porcelain tip- 82 with perforations formed therethru for maintaining the lava tip and the mass of refractory about the same in substantially incandescent condition so that the incandescent mass forms the igniting means for the mixture escaping from the nozzle 15. In this manner the ignition is certain and there is a minimum of danger of blowing out the pilot flame.

I find by experiment that it is relatively easy to ignite the gas mixture within the mass of re fractory. After the mass has apparently cooled down below any visible incandescence, it will still light the mixture readily. There seems to be a catalytic action promoting ignition.

I provide a thermostat 83 in conjunction with the pilot nozzle 81 to prevent closing of the motor circuits for the motor 29 in the event that the pilot does not maintain the refractory tip 82 hot enough to serve as an igniting device. Thus if the pilot should go out the motor 29 will not start. The pilot burner 81 may be ignited through a suitable hole formed in the side wall of the vertical tube 84.

The system of Fig. 1 is, therefore, adapted to off and on control under the control of a suitable thermostatic regulator, such as the well known Minneapolis heat regulator.

In addition to the off and on control I have found that it is possible with the device of my invention to provide a so-called up and down control, that is, controlling the amount of fuel burned in accordance with the temperature requirements. As a matter of fact, either off and on control or up and down control alone may be provided, or the two controls may be conjointly employed.

The up and down control is illustrated in Fig. 6 wherein the delivery output of the pumps and the position of the nozzle valve 18 is jointly controlled by the thermostat 68 so that within limits the temperature of the space to be heated may be maintained by increasing or decreasing the size of the fire in the mass of refractory 14. By the means which I have disclosed the amount of refractory material which is maintained at incandescence is varied in accordance with the amount of combustible mixture. In this manner the most eificient type of heat transfer is maintained by maintaining a mass of incandescent refractory in the center of the bowl as close to the upper surface as is possible. In this manner the fire remains on as long as is possible and hence the delay of bringing the refractory mass to incandescence is avoided.

I have found that when the pressure does not vary too greatly, it is possible to use fans instead of the positive feeding devices shown. A fan with suitable well known means such as a damper in the suction or discharge is satisfactory for the handling of the air under any conditions.

While one method, and particular apparatus for carrying it out, have been described in detail, it is not my intention to limit the scope of the invention by that description, or otherwise than by the terms of the appended claims.

I claim:-

1. The method of controlling surface combustion in a porous mass of refractory material which comprises delivering a gaseous combustible mixture under substantially constant pressure to and maintaining a central flame in said mass adjacent the surface and increasing the volume of the combustible mixture supplied thereto and expanding said flame laterally while maintaining the same close to the surface of the refractory mass.

2. The method of controlling surface combustion in a porous mass of refractory material which comprises injecting a combustible mixture into said mass and varying the width of the zone of combustion in accordance with variations in the amount of the mixture injected into the mass, while maintaining said zone substantially constant in thickness.

3; The method of developing heat from the combustion of fuel which comprises projecting a combustible mixture of fuel and air into a porous mass of refractory material so that the mixture burns adjacent the surface of the mass and increasing and decreasing the zone of combustion adjacent the surface of the mass by varying the amount of combustible mixture injected into the mass and maintaining the pressure of said mixture substantially constant.

4. The method of developing heat from the combustion of fuel which consists in projecting a combustible mixture of fuel and air into a porous mass of refractory material, burning the mixture in a zone adjacent the surface of the mass and correspondingly varying the area of said zone and varying the heat developed by varying the amount of combustible mixture injected into the mass while maintaining combustion below the surface of the mass.

5. The method of developing heat from the combustion of fuel which consists in injecting a combustible mixture of fuel and air into a porous mass of refractory material having passages extending therethrough for free flow throughout the mass, burning the mixture below the surface of the mass to heat the mass adjacent the flame to incandescence and varying the effective size of the incandescent zone by varying the width of the zone of injection of the combustible mix ture while maintaining combustion below the surface of the refractory mass.

6. The method of developing heat from the combustion of fuel which comprises the projection of a combustible mixture of fuel and air into a porous mass of refractory material, burning the mixture as a flame in a zone closely adjacent to but below the surface of the mass to heat the immediate surface of the mass to incandescence and expanding said flame to increase the width of the zone'of incandescenoe to increase correspondingly the incandescent area of the surface of said mass While maintaining combustion below the surface of the refractory mass.

ASHUR U. WETHERBEE.

Images