US3369527A - Boilers - Google Patents

Description

G. BROLA Feb. 20, 1968 BOILERS 2 Sheets$heet 1 Filed June 5, 1966 G. BROLA Feb. 20, 1968 BOILERS 2 Sheets-Sheet 2 Filed June 5, 1966 0 0O 0 h 0 O O O 0 0 0 o o o O O O 0 0 O 5 iiiiittti. J

- IlIIlIIt/IIIIIIII'II I, Illlllllllll.IIIIIIIIIIIIIIIIIIIIIIIIIIIII" IIIIIIII'IIIIIIIIIII United States Patent 3,369,527 BOILERS Gabriel Brola, Nogent-sur-Marne, France, assignor to Socit Generale Thermique, Le Pre Saint-Gervais, France, a company of France I Filed June 3, 1966, Ser. No. 555,157 Claims priority, application France, June 4, 1965,

6 Claims. (01. 122-410 ABSTRACT OF THE DISCLOSURE A fire-tube boiler in which the water being heated circulates without being pumped to insure uniform heating throughout the boiler. An annular water chamber surrounds a flame tube in which water tubes extend between the upper and lower portions and beyond the ends of a longitudinally extending feed water distributor in the lower portion and a longitudinally extending collector in the upper portion to provide for the continuous circulation of the water to prevent non-uniform heating.

This invention relates to boilers.

In fire-tube boilers used for the production of low or high pressure steam, or in boilers for the production of hot water or super-heated water, the internal circulation of the water is caused only by thermo'siphon. In effect, since the section of the water passage in the boiler as a whole is very large, the water velocity resulting from the inlet of feed water is negligible, being of the order of from to 10 millimetres per second.

But this natural circulation is only established very slowly after the boiler has been fired assuming that the volume of the water is substantial in relation to the heat flux received at any given instant. Until the boiler is working under normal operating conditions, the circulation is practically nonexistent, and the coefficient of convection between the water and the walls of the boiler is thus even lower than during normal operation.

During this period, certain metal parts of the boiler exposed to the heat flux, are less well cooled, which results in an increase in the temperature of the metal, and, as a result, an increase in the thermal stress. Certain walls exposed to the hot gases are subjected to thermal shock especially when the starting is effected with the burner operating at its maximum output. In large boilers, it is observed quite frequently, that even after a certain time of operation, the water which is at the bottom of the boiler is still cold whilst in the upper part the water is in its vapour phase. This indicates that the natural circulation has not been established in the whole of the boiler.

Moreover, the natural circulation, which is established in a boiler is a function of the operational conditions of the burner and as these conditions vary constantly, the distribution of the heat flux in the boiler also changes. In certain conditions of operation it is possible that in one part of the boiler the natural circulation speed is increased, and in another part it is reduced or vice versa. In the region where the speed of the water becomes very low or even nil, excessive heating of the metal walls may result.

It is also possible that pockets of steam may be formed in the regions where the water speed becomes very low or nil; as these pockets cannot be entrained by the water, they isolate the metal of the boiler, which therefore results, in this region, considerable over-heating of the metal. This over-heating may, in consequence, increase the stresses and fatigue of the metal.

The present invention has for its object a fire-tube boiler which is improved in such a manner as to overcome these disadvantages. I

The boiler, according to the invention includes, in known manner, a flame tube disposed within a body which contains the water to be heated or to be vaporised and is traversed by combustion-gas tubes communicating with the flame tube, and is characterised by water tubes which are disposed transversely with respect to the flame tube, preferably in the neighbourhood of the rear end of the flame-tube, and which connect the lower part of the body to the upper part of the latter.

These tubes receive from the flame tube an intense heat flux and, as the volume of water which they contain is low in relation to the flux received, the water is instantaneously set in motion by the thermo-syphon effect. Water circulation is thus established in the tubes which is varied as a function of the operation of the burner. The speed of circulation in these tubes may reach 1.5 to 2.5 metres per second.

The water tubes thus constitute a thermal pump which produces a continual recycling of the water in the boiler, that is to say an internal motion of all the water. The discharge of the water into the tubes may be such that the Water contained in the boiler traverses them from four to eight times before leaving the boiler.

This mixing of the water in the boiler avoids local over-heating. As the circulation is produced before the burner reaches normal operational conditions, it avoids the thermal shocks occasioned by starting. Finally, the speed of the water being higher than the critical speed necessary for avoiding pockets of steam which may accumulate 0n the flame tube or on the tubular plates; these pockets can thus no longer be formed.

In the case of a hot Water boiler, the tubes are preferably of annular form. In the case of a steam boiler they are, preferably, in the form of elbows in order to prevent the circulation of the water from disturbing the water level.

Two embodiments of a boiler in accordance with the invention, will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a view in axial section of a first embodiment of the boiler;

FIG. 2 is a cross-section on the line IIH of FIG. 1;

FIG. 3 is a similar view to that of FIG. 1 of a second embodiment of the boiler; and

FIG. 4 is a cross-section of the line IVIV of FIG. 3.

As is shown in the drawing, the boiler in accordance with the invention includes a cylindrical body 1 within which there is arranged a flame tube 2, the latter being coaxial with the body 1, as shown, or alternatively mounted eccentrically with respect to it. A burner 3, for combustible liquid or gas, discharges into one end of the flame tube 2.

The body 1 is closed by end plates 4 and is traversed by combustion-gas tubes 5 which are secured to the plates 4 and communicate with flame tube 2. In this example, the tubes 5 form two concentric bundles and a transverse wall 6 which is disposed at the end of the tube 2 opposite to the burner 3, redirects combustion gases from the flame tube to the inner bundle of tubes. A second transverse wall 7 disposed around the upstream end of the flame tube redirects the gases to the outer bundle of tubes which have just passed through the inner bundle, the gases finally being then exhausted to a chimney through a' duct 8 and/or a duct 8a. In the lower portion of the body or chamber 1 there is disposed a feed water distributor arranged longitudinally which is in communication with a feed tube for cold water 10, and serves to distribute this water to the upstream part of the boiler as well as to its downstream part. At the same time, upper portion of the body or chamber 1 has a longitudinally-extending collector 11 which communicates with a discharge pipe 12.

Tubes are disposed transversely to and across the flame.

tube 2 and connect the lower part of the body 1 to its upper part.

In FIGS. 1 and 2 which show a hot water boiler, and these tubes 9 are in the form of circulating rings 13 which are secured in the wall of the flame tube, in the region of the downstream end of the latter, through the intermediary of lower connectors 14 and upper connectors 15. The water contained in the body 1 can thusenter the rings through the connectors 14 and leave through the connectors 15. The sleeves 14 and 15 may be disposed in the vertical, median plane or even, as shown, may be slightly inclined with respect to this vertical plane, some of them in one direction and the others in the opposite direction, in order to increase the spacing between two adjacent connectors 14 and 15.

When the burner 3 is ignited, the heat of the combustion gases and the radiation from the flame are transmitted to the rings 13. By the thermo-syphon effect and assuming a low volume of water contained in the rings in relation to the flux received, the water in the interior of these rings is instantly set in motion. The cold water at the bottom of the boiler enters the lower connectors 14,

then flows to the rings 13 andpasses through the upper connectors 15 to the upper portion of the boiler. The water then falls around the periphery of the boiler chamber 1, as indicated by the arrows 16 in order to pass once again into the rings. The water at any given time in the boiler is thus circulated simultaneously whilst the speed of the water over the plate 4 at the rear end adjacent the flame tube 2 is increased.

The distribution and the collection of the water through the longitudinal conduits 9 and 11 ensures an improved distribution of the water in the boiler without disturbing the circulation eflect created by the thermal-siphon which is caused by the rings 13.

In the embodiment of FIGS. 3 and 4, the boiler is intended for the generation of steam, and the plane of separation of the water and the steam is indicated at 17. The tubes are here constituted by elbows 18 which are placed in the flame tube 2 face to face, two by two, symmetrically with respect to the vertical median plane. These elbows direct the water towards the periphery of the boiler, which substantially prevents disturbance of the water surface.

It will be clear that the invention is not to be considered to be limited to the embodiments described and shown, but it covers, on the contrary all modifications.

I claim:

1. In a boiler:

means defining a chamber in which liquid to be heated is contained, said chamber having relatively lower and upper portions,

means defining a flame tube extending into said chamber,

a longitudinally extending feed water distributor in the lower portion of said chamber. and a longitudinally extending collector in the upper portion of said chamber,

at least one water tube extending transversely across said flame tube and providing communications between said lower and upper portions, said water tube lying beyond one of the ends of said feed water distributor and said collector.

2. A boiler according to claim 1, wherein said flame tube comprises:

a relatively upstream portion, and

a relatively downstream portion,

said water tube being disposed in the downstream portion.

3. A boiler accordingto claim 1, wherein the water tube is in the form of a ring, the boiler serving to supply hot water.

4. A boiler according to claim 1, wherein the water tube is in the form of an elbow, the boiler serving to supply steam.

5. In a boiler according to claim 1:

water feed means comprising an inlet pipe, and

said feed water distributor communicating with said inlet pipe.

6. In a boiler according to claim 1, wherein said heated water collector means comprising:

a conduit extending in the upper portion of the chamber parallel to theflame tube, and

a discharge pipe,

said discharge pipe communicating with said conduit.

References Cited UNITED STATES PATENTS 741,353 10/1903 Makin 122-145 2,604,080 7/1952 Grubbs l22145 3,241,530 3/1966 Blockley et al. 122-410 FOREIGN PATENTS 928,097 6/1963 Great Britain.

CHARLES J. MYHRE, Primary Examiner.

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