US2175013A - Boiler circulation - Google Patents

Description

Oct. 3, 193% J. BLzzARD BOILER CIRCULATION Filed Dec. '7, 1957 INVENTOR JOHN z/ZARQ Patented Oct. 3, 1939 BOILER CIRCULATION John Blizard, Garden City, N. Y., assigner to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application December 7, 1937, Serial No. 178,510

6 Claims.

My invention provides a novel boiler circulatory system which utilizes horizontally disposed tubes for the heating elements. The invention is particularly well adapted to the recovery of waste 5 heat such as contained in the exhaust gases of internal combustion engines and to munie the exhaust of such engines, but the invention is not limited thereto.

Prior types of steam generators which operate l by natural or thermo-syphon circulation, have their heating or steam generating elements disposed at various convenient angles ranging be* tween the vertical and an inclined horizontal. Such disposition of the heating elements has l been thought necessary heretofore to cause the steam when generated in the heating elements:

to ow only in the direction desired for the circulation through the generator. The inclination of the tubes from the horizontal causes the steam always to move toward the highest point in eac heating element in the path of lesser resistance and thereby provides a deiinite circulation through the boiler. However, when horizontally disposed heating elements are utilized without means for forcing circulation in the desired direction, the steam upon generation in the heating elements will tend to flow in both longitudinal directions of the elements and no circulation will ensue.

My invention overcomes this difculty and provides a boiler employing horizontally disposed heating elements, with a positive natural circulation.

The nature of the invention will be understood from the following description taken in connection with the accompanying drawing, forming a part hereof, and in which:

Fig. 1 is a vertical sectional View of a boiler embodying the invention and arranged to recover the heat from the exhaust gases o an internal combustion engine;

Fig. 2 is an elevational View of the right hand end of the boiler shown in Fig. l; and

Fig. 3 is an enlarged longitudinal sectional view 15 of a Venturi tube shown in Figs. l and 2.

Referring to the drawing, reference character I0 designates an internal combustion engine of any type, a Diesel engine for example, having an exhaust manifold I l which receives exhaust gases 30 from the engine and delivers them to an exhaust pipe I2 from which they are discharged into the inlet I3 of the boiler. After flowing over the heating elements of the boiler the exhaust gases flow out of the boiler outlet |41 and may be con- '05 ducted to a flue or stack.

The boiler heating chamber, designated l5 is dened by vertically disposed walls of substantial construction to withstand the relatively severe pulsations of pressure of the exhaust gases.

The heating elements of the boiler are horizon- 5 tally disposed in the heating chamber or zone l5.

In the embodiment shown, two rows of economizer tubes i8 and four rows of boiler tubes i9 are employed, with the economizer tubes disposed at the upper part of the heating chamber 10 above the boiler tubes. The tubes i8 and I9 are preferably straight steel pipes encased in cast iron members 2l) which provide extended surfaces in the form of a plurality of outwardly tapering iins or gills. The members 29 may be applied 15 to the tubes in a number o1 ways but preferably they are separate rings or groups of rings which are shrunk onto the tubes and are fitted together with dovetail joints so as to completely surround and encase the tubes. 2O

The tubes of each horizontal row or bank are preferably spaced relatively close together so that the fins 2! almost contact each other. The rows of tubes are spaced farther apart than the spacing of the tubes in each row, to thereby pro- 25 vide distinct restrictions in the path of flow of the gases passing through the heating chamber so that the gases are successively restricted and expanded. The tubes of adjacent rows are also staggered to break up the gas flow and cause 30 the gases to iiow in a tortuous path through the heating chamber.

Water is supplied to the boiler through conduit 22 to the economizertubes i8 and after passing therethrough flows through conduit 23 into the 35 lower part of a steam and water drum 24 disposed outside the heating chamber and, as shown, transversely to the heating elements. Economizer tubes I8 are connected serially by U-bends which are disposed outside the heating chamber 40 and are encased in insulation within casing E5.

Water flows from` drum 24 through downcomers comprising two side connections 2l and Venturi tubes 2B, then through elbows 29 and horizontal connections 3i) into manifold 3l that 45 extends the width of the boiler at the height of the lowest row of tubes. From manifold 3l the water ows in parallel to all the individual tubes of the lowest row, thence in parallel successively through individual tubes of the other rows and through connections 32v into the bottom of the steam and Water drum. U-bends outside the heating chamber walls and in casings 26 connect vertically disposed boiler tubes in series. As there are twelve tubes to a roW, and four rows of boiler tubes in the embodiment shown, there are twelve groups of four tubes each connected in series between the manifold and the steam and Water drum.

The tubes are made of U-bend units, each unit having a plate 33 arranged thereon at the bent end. Plates 33 may be of various shapes and together constitute one of the Walls of the heating chamber I5. The ends of the tubes opposite the bends are expanded into the heating chamber wall and have flanges 34 at their `ends outside the Wall for connection to U-bend headers 35. Plates 33 are held by the tubes. Ribs 36 on plates 33 bear against the tube bends 25 and serve to determine the position of the plates to build up the wall member. Tightness at this side of the chamber is obtained by tightness of casing 26 enclosing the tube bends.

While it is preferable that all the parts coming in contact with the exhaust gases be of cast iron, it is more practical to make the walls of steel in order to facilitate manufacture. The steel plate for the walls can be made so heavy, for example over an inch thick, as to permit corrosion thereof without injury to the boiler.

By using the arrangement above described it is a simple matter to maintain gas tightness of the boiler heating chamber. This is facilitated by the horizontal arrangement of tubes and by the arrangement of vertical series connection. In an ordinary boiler red by coal or the like, the combustion chamber and flue gas passages are under vacuum and if there is a leakage it is into this space, and is objectionable only because of its adverse effect on eciency, but any such leakage would not create a nuisance or aiect the atmosphere in any way around the boiler. However, where the gas pressure is at times above atmospheric, gas leaks cannot be permitted. In my construction each side of the heating chamber is made tight as above explained and the corners are tightly secured together.

The Venturi tube 28 which controls each downcomer 21 is positioned as shown in the drawing so that very little resistance is offered to the flow of water from the drum 24 to the boiler tubes I9, but much greater resistance is offered to the iiow of water, or towater and steam, back from the boiler tubes to the drum. The Venturi tube additionally is so proportioned that the iiow of water through the Venturi tube at normal rating to the boiler tubes will be only slightly in excess of the amount of steam generated thus tending to stabilize circulation. With this arrangement, therefore, the boiler tubes are supplied at all times with an adequate amount of water and even at low ratings reversal of direction of flow of water and steam is prevented.

I prefer to connect the steam connections 32 to the steam and water drum at the bottom thereof to provide a slight down flow of water on the surface of connections 32 against the upiiow of the steam generated which augments the normal supply to the generating tubes through connections 21, and because the steam ow bubbling up through the water in the steam and water drum maintains this water at steaming temperature so that when it is fed to the lower tubes it is ready toI flash into steam the instant any heat is added and no addition of sensible heat to the water in the tubes is necessary. This stabilizes the circulation through the boiler.

The economizer is placed at the exhaust gas outlet in order to reduce the temperature of the gases to a minimum and to act as a spark arrester by materially cooling down the gases. Diesel and other engines intermittently discharge sparks which settle on canvas and other inammable materials. By passing them over cold economizer tubes these sparks are cooled to the point where they will not set fire to material on which they light. l

The economizer by producing greater average mean temperature differences and what might be described as partial counterlow of gas and water through the muffler increases the heat absorbing capacity of the system. It will be noted that the greatest heat absorption is at the places of smallest area of gas travel whereby the heat absorption aids in the muflling effect.

Steam is taken off from the drum through connection 38 and may be put to any suitable use. When my invention is applied to ships, the steam may be used to drive auxiliaries and for heating,

cooking and other miscellaneous purposes. In the event it is found that additional muling effect is desired over that produced by the boiler disclosed, a known type of muilier not embodying a boiler may be added. Such muffler will be of smaller size than if no boiler were used by an amount determined by the eiectiveness of the boiler as a muffler.

With the boiler circulatory system of my invention, stability of circulation is provided at all ratings although horizontally disposed heating tubes are utilized and no pump or other device is employed to provide forced circulation.

Since changes may be made in the form, location and arrangement of the various parts of the boiler disclosed herein, without departing from the principles of the invention, it is understood that the invention is not to be limited except by the scope of the appended claims,

What I claim is:

l. A boiler comprising a heating zone, a plurality of rows of horizontally disposed heating tubes in the heating zone, connections between the ends of the tubes of each row and the tubes in the next higher row for the flow of steam and water therethrough, a steam and water drum above the highest row of heating tubes, a connection between said highest row of tubes and the steam and water drum, a downcomer connection between said steam and water drum and the lowest row of heating tubes and having no part at a substantially lower elevation than said lowest row of tubes, and a Venturi tube in said downcomer to provide stabilized natural circulation in the boiler.

2. A boiler comprising walls forming a heating zone, a plurality of horizontally disposed tubes in said heating zone arranged one above the other, connections between said tubes for flow of water and steam from each tube to the next .higher tube, a steam and water drum outside said heating zone and disposed above the highest of said tubes, a connection outside said heating zone between the highest of said tubes and the bottom part of said steam and water drum, a downcomer connection outside said heating zone between the water space of said steam and water drum and the iowest of said tubes and having no part at a substantially lower elevation than said lowest row of tubes, and a Venturi tube in said downcomer connection proportioned to supply water at normal rating to said tubes only slightly in excess of the amount of steam generated and to control circulation.

3. A boiler comprising walls forming a heating CII zone, a plurality of horizontally disposed tubes in said heating zone arranged one above the other, connections between said tubes outside said heating zone for flow of water and steam from each tube to the next higher tube, a steam and wat-er drum outside said heating zone and disposed above the highest of said tubes, a connection outside said heating zone between the highest of said tubes and the bottom part of said steam and water drum, a downcomer connection outside said heating zone between the Water space of said steam and water drum and the lowest ,of said tubes and having no part at a substantially lower elevation than said lowest row of tubes, and a Venturi tube in said downcomer connection'proportioned to supply water at normal rating to said tubes only slightly in excess of the amount of steam generated and to control circulation.

4. A boiler comprising walls forming a heating zone, a plurality of horizontally disposed tubes in said heating zone arranged one above the other, connections between said tubes for iiow of water and steam from each tube to the next higher tube, a steam and water drum outside said heating zone and disposed above the highest of said tubes, a connection outside said heating zone between the highest of said tubes and the bottom part of said steam and water drum, a downcomer connection outside said heating zone between the water space of said steam and Water drum and the lowest of said tubes and having no part at a substantially lower elevation than said lowest row of tubes, and a Venturi tube in said downcomer connection.

5. A boiler comprising walls forming a heating zone, a plurality of horizontally disposed tubes in said heating zone arranged one above the other, connections between said tubes for flow of Water and steam from each tube to the next higher tube, a steam and water drum outside said heating zone and disposed above the highest of said tubes, a connection outside said heating zone between the highest of said tubes and the bottom part of said steam and water drum, a downcomer connection outside said heating zone between the water space of said steam and water drum and the lowest of said tubes and having no part at a substantially lower elevation than said lowest row of tubes, and a Venturi tube in said downcomer serving to stabilize circulation.

6. A boiler comprising a heating chamber, a plurality of horizontally disposed tubes in the heating chamber, a steam and water drum disposed so that the normal water level therein is abo-ve said tubes, a connection between said tubes and said drum, a downcomer connection between said drum and the lowermost of said tubes and having no part at a substantially lower elevation than said lowest row of tubes, and a Venturi tube in said downcomer connection,

JOHN BIJZARD.

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