US2088456A - Express boiler - Google Patents

Description

EXPRESS BOILER Filed Dec. 13, 1934 5 sheets-sheet 1 W/LFRE R. Woon.

ATTORN EY W. R. WOD

July 27, 1937.

EXPRESS BOILER 5 Sheets-Sheet 3 Filed Deo. 13, 1934 IINVENTOR W/LF/EED 1. Woon, y BY 7.-

ATTORNEY W. R. WOOD EXPRESS BOILER July 27, 1937.

Filed Dec. 15, 1934 5 Sheets-sheet 4 lNvreNToR M//LFEED E. wooo. BY

ATTORNEY Patented July 27, 1937 UNITED STATES EXPRESS nonna Wilfred R. Wood, New York, N. Y., assigner to l Combustion Engineering Company, Inc., New

York, N. Y.

Application December 13, 1934; Serial No. 757,337

6 oiaims. (C1. 1225-236) f My invention relates to steam boilers and `aims to provide a boiler having high output per pound and per cubic foot as well as good efliciency over a wide range of load.

5'# A suitable arrangement for putting the invention into practice will now be described in detail in connection with the accompanying drawings and further objects and advantages l of theinvention will be apparent to those skilled i? in the art from such detailed description and drawings. In the drawings,

Fig. l is a vertical sectional view on the line I-I of Fig. 2 looking in the direction of the arrows.

l Fig. 2 is a central horizontal section on the line 2 2 ofFig. 1*.

Fig. 3 is a central vertical sectional view of the boiler shown in Fig. 1 on a plane at right angles to that of Fig. 1.

Fig. 4 is a vertical sectional view on the line 4-'4 of Fig. 2 looking in the direction of the arrows.

Fig. 5 is a front elevation of the boiler shown in Figs. 1 4.

`Fig. 6 is a fragmentary view on an enlarged scale of a portion of the generating bank, superheater'and economizerappearing in Fig. 2,

The boiler 8 illustrated in the drawings, comprises'an upper drum I for steam and water and a lower water or mud drum l2 together with two banks I4,A I4 of oppositely bowed generating tubes extending between such drums in planes at right Aangles to the axes ofv said drums and arranged to take water' from the lower drum I2 andfto deliver steam and water to the upper drum lll by thermosyphonie circulation. Each of banks I4 is divided into two groups, Ida, and

two banks of tubes I4 are two smaller groups of tubes IS, I6, the tubes in groups I6 being shown as having larger diameters than those of banks I4. Tubes in groups I6 are parallel to banks I4' and the inner faces of such groups bound a central rounded or somewhat cylindrical combustion chamber I8, one group I6 and bank I4 lying on each side of such chamber. The tubes in groups I 6 are staggered in the direction of gas flow which is in general radially outward from the center of chamber I8 along the length of groups I6 and banks I4. The group I4a comprising the first seven rows of transverse tubes in a bank I4 are also staggered, being arranged on relatively close centres, but the remainingv tubes in such bank comprise a group I4by and are arranged in rows which lie parallel to the direction of the boiler.

Immediately adjacent andbetween thev gas ow in vertical' planes transverser to the axis of chamber I8, such rows being spaced apart transversely to the gas flow a somewhat greater distance than the diameter of one of the superheater tubes so as to form lanes I 9 (Fig.l 6). It will be seen from Figs. 2 and 6 that the lgenerating tubes in group I4b of each bank I4 are spaced closer in the direction of` gas flow than they are in the direction transverset-hereto, the centres of each group-'of four adjacent generating tubes of the group dening the corners of 'a rectangle longer in the axial than the radial One such group is indicated by crossed broken lines X, X in Fig. 6.

The lanes I9` in banks I4 are occupied by units ZI), 2U of a superheater, the individual tubes of units 20 being, however, of greater diameters than the tubes of banks I4 and nearly as Wide as lanes I9. As is clear from the drawings, the center of each superheater tube lies I at the intersection of the diagonals of a given y rectangle whose corners are determined by the centres of four'adjacent tubes. Consequently,

the individual tubes of the superheater units have the same spacing as the generating tubes both in the direction'of gas ow and in the direction transversely thereto and the li'low vof gases between and around the tubes of the en tire assembly of generating tubes and units 2i) in groups I4b of banks `I4 is thesamey as if the space within such banks were entirelyoccupied by generating tubes of the same diameter throughout, but on closer centres. The transverse distance between the rows of generating tubes being only slightly greater Ithan the diameter of the tubes of units 2Q the flow of gases is much the same as.` though the tubes were staggered, giving a high rate of heat pick-up.

Having the tubes of units ZIB of greater diameter than those of the tubes in bank I4 has several advantages. Not only does such Yfeature in the described arrangement increase the massilow factor and thereby the rate of heat absorption per unit oi area, but it gives wide lanes be! tween adjacentrows of boiler tubes in bank I4, so that by removing a unit 2B ample space is provided for the removal of `a'give'n generating tube in bank I4 whenever it is desired todo so. Also, I have shown the tubes in bank I4 as spaced farther apart in the direction axiallyy of drums I0 and I2, that is longitudinally land axially of chamber I8, than inthe direction circumferentially of such drums and radially of chamber I8 with the result that the ligaments between tubes in drums I and I2 in the axial direction of such drums are greater than the ligaments in the circumferential direction, thereby permitting the drums to be thinner and lighter than otherwise. Furthermore, the relatively large tubes in units 20 have the advantage of reducing the pressure drop through the superheater. In the boiler illustrated kit is. assumed that the generating tubes in bank I4 are of one inch diameter, this being common practice in naval boilers, while the tubes in units 20 are of 1% inches diameter. If the latter also were of one inch diameter, it is estimated that it would require a three hundred pound pressure kdrop merely to overcome the resistance to flow of the superheater at full load on the boiler.

Next to and radially outside the spaces occupied by the banks I4 and superheater units 28 are two economizer sections composed of arcuate units 22, 22. In the arrangement illustrated, units 22 closely surround banks I4, the tubes in units 22 preferably being of the same size as the tubes in banks I4 and preferably having the same centrer of curvature so as to utilize the available space to the best advantage. The units 22 lie in vertical planes transverse to the axis of the chamber I8. There are more than` twice as many units 22 in the direction transverse to the gas now, that is axially of the boiler, as there are units 20, some of the units 22 lying in the same transverse vertical planes with the units 2O and others of the units 22 lying in the same transverse vertical planes as the rows of generating tubes in banks I4. Both the units 28 and the units 22 have breakable joints at their ends so that, by first ,removing the proper unit 22, any unit 20 may be removed from the boiler without disturbing any generating tube. Furthermore, by taking 'out any pair vof units 28 and 22 in a given plane, a lane is provided whereby any given generating tube I 4bmay be removed from the boiler without disturbing more than the tube which is to be removed. They units 28 receive steam directly from drum I and deliver it to an outlet header 23 for superheated steam and have breakable joints 20a. and 2Gb at the ends near such drum and such header respectively. Units 22 receive feed water from a header 24 and deliver it to `drum I0. Units 22 have breakable joints at 22aand 22h respectively near header 24 and drum I0. As appears in Fig. l, gases which have passed from chamber I8 outwardly through a bank I4 and economizer section 22 reach one of the collecting chambers 25 from which they pass into the uptake 25a..

The groups of large staggered generating tubes I6 and banks I4 do not extend the entire length of the chamber I8, it being preferred to utilize only a portion of the length of such chamber for the outlowof gases therefrom in order to maintain a high gas Velocity and thereby obtain a high rate of heat absorption per unit area of the generating tubes. The portion of the oombustion chamber I8 outlined by the spaced tubes I6 may be considered the rear portion thereof, the spray nozzles 26, 26 for liquid fuel being placed in an oval ring (Fig. in the front transverse wall 28 of combustion chamber I8. The front portion of the chamber I8, that is the part nearer the wall 28, is bounded by two groups of large generating tubes 30, 30 which are set close togetherso as to prevent the passage of gases therebetween. Furthermore, I prefer to place the tubes 30 'at a greater distance from the center of the chamber I8 than the tubes I6 so as t'o have chamber I8 as large as practicable. Preferably the gap between the tubes 30 and the tubes I6 transversely of the boiler is closed by a wall formed primarily of a row of closely set generating tubes 32.

Outside of each row of bent generating tubes 38, I provide preferably several rows 34, 34 of unheated downcomer tubes. However, for a certain space lengthwise of the drums I8 and I2, I provide an axial gap on each side of the boiler in the rows 3U and 34 which I utilize for the introduction of air into chamber I 8. Such gap therefore is filled by air ducts 36, 36 which extend somewhat at an angle to the radii of the chamber I8 in the vertical plane through the ducts whereby air entering through such ducts is given a whirling motion in order to increase the turbulence in the chamber I8 and promote efficiency of combustion. This arrangement has a further advantage in that, altho the inner ends of the ducts 36 necessarily extend to the edge 'of the combustion chamber, they nevertheless do not become overheated because they are cooled at several points along their lengths by cold downcomers 34 while their inner edges are against tubes in row 30.

Dampers 38, 38 are provided for the ducts 36, such dampers being pivoted at the outer ends of the ducts and preferably arranged in sets in such a way that alternate dampers are in one set and alternate dampers in another.

The air ducts 36 on one side of the vertical plane through drums I0 and I2 have two sets of dampers associated therewith and those ducts on the other side of such plane have two additional sets of dampers associated therewith. The dampers of each set are shown as linked together so as to operate synchronously and the two sets on one side of the boiler are shown as controlled by two wheels on a single standard 39. By closing certain dampers, the air velocity thru the ducts 36 being used is maintained so that a good whirling action of the gases in chamber I8'is obtained even at part loads.

Preferably the front wall 28 and the rear'wall 39 of chamber I8 are covered in large measure by transverse rows of generating tubes 40 and- 4I respectively.

The boiler illustrated in the drawings is of the single pass type, but the tubes are in vertical planes and the gas outlet is above the upper ends of the tubes. There would be therefore, unless means were provided to offset it, a tendency for a part of the gases to by-pass the heating'surface in the lower part of the boiler. I have therefore provided two sets of dampers 42, 42 one on the upper portion of each of the economizer sections. As is clear from the drawings, closing dampers 42 more or less forces more or less of the gases of combustion over the tubes in the lower half of the boiler.

It has been customary to provide a number of steam jet blowers for blowing the soot off the generating tubes in express boilers but the arrangements adopted have customarily required the provision of spaces between groups of tubes for the insertion of such blowers. I have intentionally avoided providing spaces for this purpose as I have desired to employ-'all the available space for generating or heating tubing. I find, however, that the required cleaning of the tubes can be provided by a single soot blower 44 set on the axial line of` the chamber I8 and i having an inclined delivery` nozzle 'arranged to project a blast of steam covering the entire axial length of the group of tubes I6. The blower 42 is arranged to be rotated on its axis and the entire surface needing to be blown can be cleaned by the single blower 44.

Design computations show that a boiler in accordance with my invention will have a high output. In part, such result is attributableito the economizer design and its arrangement relative to the remainder of the boiler. The use of economizers is not new in marine practice, but their use has not become general largely because such use has involved greater weight and greater space. Weight with space is the very essence of a successful marine boiler. There is no increased weight chargeable to the economizer in the design shown herein because the economizer tubes are of like diameter and of like pitch as the tubes in bank I4. Thus there is no increased weight in substituting economizer tubes for boiler tubes except for the economizer headers. The Weight of such headers is more than compensated for by the greater heat head to which the economizer tubes are subjected as compared to generating tubes in the same location, such increased heat head being due to the fact that the Water in the economizer tubes travels in the opposite direction to the heating gases instead of at right angles to such gases as in the case of generating tubes. In other words, a given amount of heat is absorbed in the economizer section by less surface than would be required by boiler tubes in contact with gases at the same temperature. Also since the economizer tubes are of a like pitch and size to the replaced convection tubes and since there is no gap between the convection tubes used and the economizer tubes not only has no space been lost, but some space has been saved, owing to the great heat absorbing capacity of the economizer tubes.

It appears from the drawings also that each economizer section fits closely around the outside of one of the banks I4 of generating tubes so as to eliminate waste of space between the two sections, thereby promoting the space eiliciency of the boiler. Nevertheless, the removable units of the economizer sections permit ready removal of the generating tubes and the superheater units.

It is evident further that the relative arrangement of air ducts and nozzles creates a rapid swirling of the air and fuel to cause a thorough mixture of the two thereby giving rapid and eif1- cient combustion. I estimate that a given Combustion chamber can eiciently burn one third more fuel with my arrangement than with the usual one. A feature promoting such result is that all the air is introduced into chamber I8 through air ducts 36 and therefore in a plane.

at right angles to the discharge of fuel atomizers 26. The whirling action is therefore a maximum for a given amount of air. Such whirling action assures, moreover, that flame will be carried outward until stopped by tubes 30 which bound the front portion of the chamber I8, whereby the flame and combustion utilize the entire portion of the chamber I8 in front of the bank I4. The fact, however, that the front end of the chamber I8 is enlarged of itself promotes the thorough mixing of the air and fuel with the consequent completion of the burning before the fuel reaches the tubes of the convection bank. I therefore do not limit myself in all cases to the arrangement for causing a whirling of the air for combustion. As shown, chamber I8 has 50% greater volume in its front portion than in its rear. l

It' will be understood that Fig. 2 is partly diagrammatic in that it is on so small a scale the tube lay-out cannot be accurately shown therein. The actual lay-out appears in Fig. 6, although I do not limit myself to the lay-out of Fig. 6.

A feature of my invention is that I arrange all the tubes which absorb heat from the gases by convection in groups which are narrow axial- 1y of the combustion chamber whereby a high rate of gas flow over the tubes and a high rate of heat absorption per cubic foot is obtained. It is a peculiarity of the two drum boiler illustrated, that the tubes are long in proportion to the height of the space available for the boiler. The gases, however, leave the combustion chamber along the entire lengths of the tubes, so that if the heat absorption per square foot of gas touched surface is to be high, the velocity of the gases must be maintained by narrowing the outlet for gases in the axial direction. I nd it necessary, to obtain a rate of heat absorption greater than that now obtained in other marine boilers, to make the axial length of each bank I4 not substantially more than 40% of the length of the average tube in such banks. The type of boiler shown however, having only two drums, does not permit increasing the depth of banks I4 in the direction of gas flow a corresponding amount to cool the gases enough to maintain the efficiency of the boiler as high'as desired. I have therefore placed the arcuate economizer units 22 immediately beyond each bank I 4 to cool'the gases and maintain both the output per cubic foot and the overall efliciency at a given load.

In many installations, especially marine installations the space for a boiler is limited in the direction axially of the combustion chamber I8 as Well as vertically. By arranging the tubes 3l) on a larger radius than that of the tubes I6, the volume for combustion is very greatly increased for a given extension of the boiler axially beyond the convection bankr and large quantities of fuel may be burned per unit of time without adversely affecting the efficiency of the boiler, I find that ample volume for efcient combustion at high rates of i'lring is obtained by extending the combustion chamber outwardly, or radially at its forward portion 50% of the axial length of the convection banks. Thus, where the axial length of the forward portion of the chamber is approximately the same as that of the rear portion, as illustrated, and the radius of the latter substantially equals itsaxial length, the volume of the forward portion of the chamber is approximately 50% greater than. that of its rear portion.

The feature of the relatively short convection bank cooperates with the feature of the relatively long purely radiant section of the combustion chamber to` maintain high over-all efficiency at' high output. The combustion thereby is completed before any ofthe gases strike tubes I6 and I4 and the efficiency of combustion is independent of the rate of firing over a very wide range.

There are recognized limits to the air pressure in so-called closed Stoke holds, the locations in which my boilers will commonly be used.

Some of this pressure is used in passing the air into the combustion chamber and largely the remainder in passing the gases through the convection bank. The arrangement now in common use requires that far the greater part of' the total be expended in passing the air into combustion chambers. In my design by far the greater part of the total pressure is available at the intakes of the convection banks. Obviously a design which reduces the amount of draught used in passsing the air into the combustion chamber enables the use of a greaterv mass flow through the convection tubes. This increase results in a betterheat absorption.

While I have disclosed a particular arrangement, I wish it understood that the terms of each of the following claims are to be taken broadly.

What I claim is:

1. A boiler having a combustion chamber rounded with respect to an interior axis, two groups of closely set generating tubes spaced axially of said chamber and bounding portions thereof, radially deep air ducts fitted between said groups and having their inner ends outside the inner edges of said groups, and downcomer tubes arranged to cool said ducts.;

2. The combination in a boiler having top and bottom drums of two sets of oppositely'bowed generating tubes connecting said drums so as to enclose a portion of a combustion chamber and arranged so as to prevent passage of gases therebetween; two additional sets of oppositely bowed heat absorbing tubes, some of such additional sets connecting the said drums and arranged so as to enclose another portion of said combustion chamber and all of said additional tubes being arranged to permit gases to flow therebetween away from the combustion chamber, said last mentioned sets of tubes extending outwardly from the axis of the combustion chamber beyond the rst mentioned sets of tubes, and two sets of unheated downcomers connecting the said drums and outside of said first two sets of tubes, said downcomers extending outwardly from the axis of the combustion chamber no farther than said second mentioned sets. v

3. A boiler having a combustion chamber composed of rounded front and rear portions that are approximately coaxial, said front portion having a greater cross-sectional area than the rear portion and communicating freely therewith; generating tubes dening the side walls of the forward portion and arranged to prevent passage of gases therebetween; generating tubes surrounding the rear portion of said chamber at the sides thereof and arranged to permit free ow of gases therebetween radially outward from said chamber; fuel injecting means in the front wall of the larger, forward portion of said chamber and arranged to introduce fuel into said chamber in a direction axially thereof; a circumferential air inlet in the side wall of the forward portion of said chamber adjacent the front wall thereof through which fuel is injected; and means for producing a whirling motion of the inwardly moving air about the axis of said chamber to cause it to strike the axially injected fuel substantially tangentially and produce a turbulent, swirling motion of the burning gases in and through said chamber.

4. A two-drum boiler having a generally cylindrical combustion chamber composed of freely communicating, approximately coaxial, forward and rear portions, the forward portion of said chamber extending for approximately 50% of the total axial length of said chamber and being of materially larger diameter than'the rear portion; means for introducing fuel and air into the larger portion of said chamber; and banks of oppositely bowed generating tubes on each side of said rear portion connected into said drums and arranged to permit the flow of all the gases therebetween in a direction radially outward from said chamber, the width of said banks axially of said chamber being approximately 40% of the length of the average tube in said bank, whereby a relatively large'mass gas flow at high velocity is attained through said banks.

5. In a boiler, a combustion chamber composed of rounded front and rear approximately coaxial portions,` said front portion occupying approximately 50% of the axial length of said chamber and having a volume not less than 50%' greater than that of 'said rear portion and communicating freely therewith; means for introducing fuel and air into the larger portion of said chamber; a steam drum disposed centrally above said chamber; a water drum disposed below saidsteam drum and parallel thereto; two sets of oppositely bowed generating tubes connected to said drums and defining the sides Vof the forward portion of said chamber and arranged to prevent passage of gases therebetween; two sets of unheated downcomers connecting said drums and arranged outwardly of said sets of generating tubes; two'banks of oppositely bowed generating tubes at the sides of the rear portion of said chamber arranged to permit the free flow of gases therebetweenradially outward from said chamber, said banks ofA tubes having a width, axially of said chamber, that is approximately 40% of the length of the average tube in said banks; and sets of Yserpentine economizer tubes, connected at one end to a feed header and at their other end to said steam drum, enclosing said banks of tubes with the outermost economizer tubes substantially aligned with the outermost downcomers surrounding the forward portion of said chamber.

6. In a closed stoke hold; a boiler having a rounded combustion chamber; a pair of banks of generating tubes that are arranged to receive gases from said chamber and which are relatively narrow in a direction transverse to the gas flow and relatively deep in the direction of said ow; means for injecting fuel into said chamber; and an air inlet in the wall of said chamber having a cross-sectional area such that only a minor pofrtion of the total pressure drop through said chamber and tube banks is absorbed by the admission of air through said inlet. WILFRED R. WOOD.

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