US2067173A - Fuel combustion - Google Patents

Description

Jan. 12, 1937. G. DALEN FUEL coMBUsTIoN Filed oct. 30, 1933 2 sheets-sheet 1 INVENTOR I 7?-17, *d ATTORNEY Jan. l2, 1937. DALN v 2,067,173

FUEL COMBUSTION Filed Oct. 50, 1933 2 Sheets-Sheet 2 o o ooo ooe oooo tcfjvooo o ooo OOOO 00000 7I INVENTOR la ATTORNEY Patented Jan. l2, i937 UNITE STA'ES FUEL COBEUSTION Gustar Dalen,

Lidingo, Sweden,

assigner to Svenska Aktiebolaget Gasaccumulator, Stockholm, Sweden, a corporation of Sweden Application 0ctober 30, 1933, Serial No. 695,883 In Sweden November 3, 1932 8 Claims.

The present invention relates to fuel combustion and has particular reference to continuous combustion of a gaseous fuel of Which one of the constituents is fuel vapor obtained by the vaporization of a liquid fuel such, for example, as heavy hydrocarbon fuel of the type commonly termed fuel oil. Still more particularly the invention relates to fuel combustion apparatus of the above character which is adapted to supply heat continuously to apparatus such as domestic cookstoves, Water heaters, refrigeration apparatus of the absorption type requiring heat for its operation, and like apparatus Where a continuously available source of heat is required.

In apparatus of the character under discussion, it is important that the vaporizer for vaporizing the liquid hydrocarbon fuel be maintained at a substantially constant temperature. This is required because of the fact that if the temperature of the vaporizer falls below a given minimum value, dry distillation of the heavy hydrocarbon constituents of the fuel will take place, which dry distillation results in the formation of a residue of pitch-like products which are ultimately converted into coke deposits in the vaporizer. On the other hand, if a given maximum temperature of the vapcrizer is exceeded, partial decomposition or cracking of the heavy hydrocarbons into their elementary constitutents will take place, and as a result free carbon in the form of soot will be formed.

The difference in temperature between the maximum and minimum temperatures permissible Without forming soot or undue quantities of pitch-like residue is comparatively small, and it is important that the vaporizer be kept as far as possible at a constant temperature between the limiting values.

The general object of the present invention is to provide apparatus of the character described in which it is possible to keep the vaporizer for vaporizing the liquid fuel at a constant or substantially constant temperature of the desired value regardless of variations in the temperature of other associated parts in the apparatus which may vary in temperature due to differences in the rate at which useful heat is taken from the apparatus.

Other objects and the nature and advantages of the invention will become apparent in conjunction With the accompanying description of a domestic cook-stove of the hot plate type to which the invention is applied. The invention is particularly advantageous applied to stoves of 1 this type, and such a stove has been chosen for purposes of illustration, but it is to be understood that the invention is not limited in its use to such apparatus.

In the accompanying drawings forming a part erally at l0 providing hot plates l2 and I4 and an oven I6. A second 10W temperature oven I8 may also be provided. The hot plates l2 and I4 and the oven l5 are adapted to be heated by conduction of heat through the metal of the structure l0 from gases of combustion which pass through channel to a suitable stack opening 22 adapted to be connected to a chimney. Plates l2 and l are adapted to be covered by insulated cover plates 24 and 2G. The burner indicated generally at B is spaced from vthe structure I0 and comprises a metal base member 28 which, as will be observed from Fig. 2, comprises a portion in the form of a body of revolution, the sectional area of the generatrix of which is in the form of a J. This portion provides an inner annular upstanding flange 30 and an outer upstanding flange 32. To one side of the above described portion the member 28 is extended to provide a vaporizer having a vaporizing chamber 34, the Walls of which are in intimate heat conducting relation with the combustion Zone of the burner. I'he bottom wall of chamber 34 provides a vaporizing surface 36 upon which liquid fuel falls from a liquid fuel feeding member 38, to Which a suitably regulated amount of liquid fuel is supplied through passage 40. The vaporizer thus provided may be said to be a contact vaporizer in which liquid fuel which may be a relatively heavy hydrocarbon is vaporized upon coming into contact with a high temperature vaporizing surface upon which the liquid fuel falls. In the embodiment illustrated fuel is supplied to the passage 40 from a reservoir 4l from which it flows through a fuel regulating apparatus indicated generally at 44. This structure per se forms no part of the present invention, and need not be described in detail herein. A small quantity of air is admitted to the chamber 34 through pipe t2 which is in communication with the atmosphere, and the inner end of which is in communication with the annular space 44 around the tip of the fuel feeding member 38.

A perforated pipe i5 rests at its lower end on the flange 3!! and at its upper end is closed by suitable cover plate means such as that indicated at 48. Pipe i6 is preferably provided with a relatively large number of small diameter perforations indicated at 5D. A second perforated pipe 52 having perforations 54 therein rests at its lower end against the flange 32, the lower end of pipe 52 being considerably above the level of the lower end of pipe 46. Pipes d6 and 52 provide between them an annular space 56 which is in communication with the annular space 55a formed between the inner wall of the flange 32 and the lower portion of pipe 46. Outside of pipe 52 and spaced therefrom to provide an annular outer space 58 is a pipe 60, the lower end of which is spaced above the upper edge of flange 32. Space 58 is preferably closed at its upper end as indicated at 62. A pipe 64 which, in the present embodiment is in effect a continuation of the pipe 52, forms a channel 66 which provides communication between the annular space 55 and the channel 20 in the structure Hl.

As will be seen from Fig. l, the burner is spaced from the structure l and the space between these parts is filled with insulating material such as asbestos or kiesel-guhr. The lower portion of the burner structure and the vaporizer are preferably housed in a compartment within the stove providing a chamber 58 in communication with the lower end of the space 58 between pipes 52 and Gil. Chamber 68 is also in communication by way cf pipe 'lil with the space 'I2 inside of the pipe i6 and with the atmosphere. The member 28, forming the base portion of the burner and the vaporizer associated therewith, is preferably surrounded by insulating material inf dicated at i4.

In the illustrated embodiment, in which the burner is connected to the heat requiring hot plate structure by means of a pipe such as pipe Sli, this pipe is preferably made of metal having relatively poor heat conducting characteristics, such, for example, as a chromium-iron alloy, and the perforated burner pipes also are preferably made of such material for reasons which will hereinafter appear.

Turning now to the operation of the device, fuel is fed to the vaporizing chamber, upon the vaporizing surface of which it falls and is vaporized. The fuel vapor formed in chamber 34 is drawn by the draft created by the burner into the annular space 55, with which the vaporizing chamber is in communication, and tends to pass upwardly through this space. At the same time air is drawn by the suction created by the draft through the openings A in pipe 52 from the space 5B and through the openings 50 in pipe 46 from the space 72. Spaces 56 and 55a provide a combustion zone in which combustion takes place in the form of a large number of relatively small flame jets at the several perforations in pipes A36 and 52, through which perforations combustion air flows to the combustion space. The speed of air now through the perforations in the lower portion of the burner is substantially constant, so that the amount of fuel consumed at these openings is substantially constant. Thus, as the fuel Vapor rises in the combustion zone, it is gradually burned at a relatively constant rate until it is all consumed, variation in the vate at which fuel vapor is supplied causing the end point or upper level of active combustion to vary. Regardless, however, of the distance of the end point of combustion above the base part 28, this part is subjected to the heat generated by a fixed number of flames occurring within the recess in which the lower portion of pipe 46 is located. The heat absorbed by part 28 and conducted to the vaporizer is not all lost, since the major portion is returned in the preheated fuel vapor and air drawn into the burner.

If we now consider Fig. l it will be evident that heat is transmitted to the hot plate structure not only by the combustion gases but'also by conduction through the walls of the structure forming the channel for flow of combustion gases, which structure is formed in part by the perforated pipes # 36 and 54. l'f the hot plate structure is not in use the temperature thereof rises to a stabilized degree at which the heat absorbed just balances the heat lost by radiation, and there is a minimum of difference between the temperature of the hot plate structure and the burner structure. Under such conditionsv the flow of heat by conduction is at a minimum. If now heat is withdrawn from the hot plate structure for cooking purposes, the temperature thereof tends to drop, thus tending to increase the flow of heat by conduction from the burner and tending to reduce the temperature of the burner and of the vaporizer. This is obviously undesirable, since under such conditions the vaporizer is required to vaporize an increased quantity of fuel which is supplied to take care of the increased demand for heat.

In accordance with the present invention the tendency of the burner structure to vary in temperature due to variations in temperature of the structure to which the burner supplies combustion gases is susbtantially eliminated by placing the burner in poor heat conducting relation with the heat requiring parts of the apparatus. In the embodiment illustrated, this poor heat conducting relation is secured by spacing the burner from the heat requiring parts, filling the intervening spaces with heat insulating material, and by making the structure forming the walls of the channel for flow of combustion gases from the burner to the heat requiring structure of mate-- rial which has relatively poor heat conducting characteristics. This, taken in conjunction with the placing of the fuel vaporizer in good heat conducting relation with the burner structure, and with the arrangement whereby an amount of heat is generated in the burner adjacent to the vaporizer at a rate substantially coinciding with that required to maintain the vaporizer at the desired temperature, provides for maintenance of the vaporizer at a substantially constant temperature regardless of variations in temperature of the heat requiring parts.

While it has been found to be practical and convenient to make the parts such as pipe 5ft of metal having relatively low heat transmitting characteristics, such as a chromium-iron alloy, it will be evident that for the purpose of maintaining the burner in poor` heat conducting relation with respect to the heat requiring parts, the walls of the channel for flow of combustion gases may be made of other materials having poor heat conducting characteristics, such, for eX- ample, as ceramic or asbestos materials and the like.

It will be evident from Fig. l that the portieri of the burner apparatus which it is important to maintain at relatively constant temperature is the lower or base portion thereof comprising the part 23, and it will also be seen that for heat to be lost from this portion of the burner structure by conduction it must iiow through the perforated pipes i6 and 52. Thus, from the standpoint of heat conduction, these pipes may be considered as continuations of the pipe 64, and they are therefore advantageously made of material having poor heat conducting characteristics. I have found that chromium-iron alloy is particularly well suited for this use, since in order to be satisfactory the material must be capable of withstanding very high gas temperatures, and metal comprising a chromium-iron alloy, in addition to having relatively poor heat conducting characteristics, is capable of withstanding high temperatures without rapid deterioration.

In order to further reduce the rate at which heat may be conducted through the pipes 46 and 52 away from the base member 28, these pipes may be constructed as shown in Fig. 3, in which the inner pipe 36 in addition to being provided with a plurality of orifices 50 is provided with a number of transversely extending slots 5l, which may advantageously be staggered circumferentially of the pipe as shown in the figure. Pipe 52 is also shown as being provided with a number of circumferentially staggered transversely extending slots 53 in addition to the orifices 54. It will be apparent that the provision of these slots will greatly reduce the cross sectional area of metal providing a path for flow of heat by conduction, and it will also be apparent that other specific means may be employed for reducing the ability of the pipe structure to conduct heat away from the base of the burner. Obviously, in order to make the rate of heat conduction through the burner pipe structure as low as possible, the thickness of metal employed in the pipes and consequently the cross sectional areas thereof should be as small as practical.

In the embodiment shown in Fig. 3, the base member is slightly different in contour from that shown in Fig. 1 and the fuel, vapors admitted to the space 55a may be admitted thereto through a perforated plate 15.

From the foregoing it will be evident that the iiarnes burning in the portion of the combustion zone below the level of the upper edge of the flange 32 forming the side wall of the recess in part 23 transmit to this part the amount of heat required for the vaporizer and consequently the height of this flange is made such that it will be opposite a sufficient number of the perforations to enable it to absorb and transmit the quantity of heat required by the vaporizer when the latter is operating at full capacity. Any surplusage of heat from the ames opposite the ange and the heat from the flames above the top of the flange is carried by the combustion gases to the heat requiring parts. Since the base portion of the burner is insulated against flow of heat by conduction therefrom, this division or distribution of the heat developed results in the maintenance of the base portion, including the vaporizer, at substantially constant temperature. It will also be evident that when there is no demand for heat from the hot plate structure, and only enough fuel is supplied to compensate for radiation losses and to keep the apparatus at the desired temperature level, the level of active combustion may be below the top of the flange 32.

The specic vaporizer structure involving the liquid fuel feeding and air feeding arrangements and the means for regulating the fuel supply have not been described herein in detail, since such description is not necessary to an understanding of the present invention, and, within the scope of the present invention other specific forms of vaporizer and fuel feeding structure may be employed. The vaporizer and fuel feeding structure arrangement herein shown by way of illustration is disclosed and claimed in the copending application of Gustaf Dalen and G. E. Bjorklund, Serial No. 655,334, led February 6, 1933.

While in accordance with the patent statutes I have described a preferred embodiment of apparatus for carrying the invention into effect, it is to be understood that the invention is not limited to such embodiment, and that certain novel features of the invention may be employed to the exclusion of others without departing from the spirit or scope of the invention.

What I claim is:

1. A stove of the hot plate type comprising a metal mass having a hot plate part and a channel for combustion gases through said mass for heating said part, a burner located within the body of the stove and spaced from said mass, said burner having parts providing a combustion zone for producing gases for heating said hot plate part, a Contact Vaporizer located within the body of the stove and having a vaporizing chamber in intimate heat conducting relation with the burner structure for vaporizing fuel to be burned in said burner, means within the body of the stove having relatively poor heat conducting characteristics providing a channel for flow of combustion gases from said combustion Zone to the first-mentioned channel, and a mass of heat insulating material within the stove surrounding the burner and said means.

2. A stove of the hot plate type comprising a metal mass having a hot plate part and a channel for combustion gases through said mass for heating said part, a burner located within the body of the stove and spaced from said mass, said burner having a heavy metal base member providing a vaporizing surface for contact vaporization of heavy hydrocarbon fuel and tubular burner parts extending upwardly from said base member to provide a combustion Zone for fuel vapor produced by said vaporizing surface, said base member having portions arranged to absorb heat directly from the lower portion of said-combustion Zone to maintain said vaporizing surface at high temperature, means within the body of the stove having relatively poor heat conducting characteristics providing a channel for flow of combustion gases from the upper portion of said combustion Zone to the first-mentioned channel, and a mass of heat insulating material surrounding said means and the tubular parts of said burner, said means preventing rapid flow of heat by conduction through the walls of the second-mentioned channel when withdrawal of heat from said hot plate part reduces the temperature of said metal mass so as to produce a relatively great temperature difference between the temperature of the metal mass and that of the base member of the burner, whereby to insure relatively even high temperature of the vaporizing surface regardless of the temperature of said mass.

3. In a heating device of the character described, a heat requiring part within the device arranged to be heated by combustion gases owing in contact therewith and to transmit heat by conduction to a body to be heated, said part tending to vary in temperature with variations in the rate at which heat is absorbed therefrom by the body to be heated, burner structure within the device including a contact vaporizer spaced from said heat requiring part and in intimate heat transfer relation with at least a portion of the combustion zone of the burner, and a pipe structure within the device having poor heat conducting characteristics, said pipe structure connecting said burner structure with said heat requiring part to provide a channel for ow of cornbustion gases within the device to said part and the poor heat conducting characteristics of the pipe structure retarding the loss of heat from the burner structure to the heat requiring part by conduction through the walls of said channel.

4. In a heating device of the character described, a heat requiring part within the device arranged to be heated by combustion gases flowing in contact therewith and to transmit heat by conduction to a body to be heated, said part tending to vary in temperature with variations in the rate at which heat is absorbed therefrom by the body to be heated, burner structure within the device including a contact vaporizer spaced from said heat requiring part and in intimate heat transfer relation with at least a portion of the combustion zone of the burner, and metal. pipe structure Within said device providing a channel for iiow of combustion gases within the device from said burner structure to said heat requiring part, said pipe structure including at least a section formed of metal having a low coeicient of heat conductivity for retarding loss of heat from the burner structure to said part by conduction through the Walls of said channel.

5. In a heating device of the character described, a heat requiring part within the device arranged to be heated by combustion gases flowing in contact therewith and to transmit heat by conduction to a body to be heated, said p-art tending to vary in temperature with variations in the rate at which heat is absorbed therefrom by the body to be heated, burner structure within the device including a contact vaporizer spaced from said heat requiring part and in intimate heat transfer relation with at least a portion of the combustion zone of the burner, and a relatively thin walled pipe structure of chromium-iron alloy Within said device for conducting combustion gases from the burner structure to said heat requiring part while retarding loss of heat from the burner structure to said part by conduction through the walls of the pipe structure.

6. In a heating device of the character described, a heat requiring part within the device arranged to be heated by combustion gases fiowing in contact therewith and to transmit heat by conduction to a body to be heated, said part tending to vary in temperature with variations in the rate at which heat is absorbed therefrom by the body to be heated, burner structure within the device comprising a metal base portion spaced from said heat requiring part, said base portion including a space for combustion of fuel and a contact vaporizer in intimate heat transfer relation with said space, and pipe structure within the device connecting said base portion and said heat requiring part for flow of combustion gases to said part, said pipe structure being constituted at least in part by another portion of said burner structure and the last mentioned portion being made of metal having a low coefficient of heat conductivity for retarding loss of heat by conduction from said base portion to said heat requiring part.

'7. In a heating device of the character described, a heat requiring part within the device arranged to be heated by combustion gases flowing in contact therewith and to transmit heat by conduction to a body to be heated, said part tending to vary in temperature with variations in the rate at which heat is absorbed therefrom by the body to be heated, burner structure within the device comprising a metal base portion spaced from said heat requiring part and a perforated combustion pipe portion, said base portion including a space for combustion of fuel and a contact vaporizer in intimate heat transfer relation with said space, and pipe structure within the device constituted at least in part by a perforated combustion pipe part of the burner, said pipe structure connecting said base portion with said heat requiring part to provide a channel for ow of combustion gases to said part and said perforated combustion pipe part being made from metal having a low coecient of heat conductivity to retard loss of heat by conduction from said base portion to said heat requiring part.

8. In a heating device of the character described, a heat requiring part within the device arranged to be heated by combustion gases nowing in contact therewith and to transmit heat by conduction to a body to be heated, said part tending to vary in temperature with variations in the rate at which heat is absorbed therefrom by the body to be heated, burner structure within the device comprising a metal base portion spaced from said heat requiring part and a perforated combustion pipe portion, said base portion including a space for combustion of fuel and a contact vaporizer in intimate heat transfer relation with said space, and pipe structure within the device constituted at least in part by a perforated cornbustion pipe part of the burner, said pipe structure connecting said base portion with said heat requiring part to provide a channel for ow of combustion gases to said part and said perforated combustion pipe part being made from vmetal having a low coefiicient of heat conductivity and having transverse slots formed therein, whereby to retard loss of heat by conduction from said base portion to said heat requiring part.

GUsTAF DALN.

Images