US2062481A - Book support - Google Patents

Description

E. R. STONE GRATE STRUCTURE Dec. 1, 1936.

Filed Aug. 28, 1934 3 Sheets-Sheet 1 FIG-21.1.

- INVENTOR EARLLRbToNE.

- BY awn, ATTORNEY Dec.1,1936. R; NE 2,062,481

GRATE STRUCTURE v Filed Aug. 28, 19:54 IS SheetS-Sheet 2 \IHIMIIIIH IMIM-HIIIUHIIIIHIM All I llllllllllllllfl INVENTOR WITNESSES:

7 BY 75 --M (g ATTORNEY ,3 EARLLRSTONE Dec. 1, 1936.

E. R/STONE GRATE STRUCTURE s Sheets- Sheet :5

Filed Aug. 28, 1934 i I INVENTOR EHRLL. E. STONE wqspvawq ATTORNEY Patented Dec. 1, 1936 UNITED STATES QRATE STRUCTURE Earll R. Stone, Lansdowne, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 28, 1934, Serial No. 741,772

4 Claims.

My invention relates to fuel-supporting structure for combustion apparatus and it has for an object to provide for improved air admission with variable conditions of the fuel bed.

5 Heretofore, the fuel-burning grate of combustion apparatus has frequently consisted of fuelsupporting members with holes extending therethrough or therebetween for the admission of air into the fuel bed for supporting combustion. The 10 draft, in natural draft furnaces, or the air pressure, in forced draft apparatus, causes flow of air through such holes and through the fuelbed.

Usually, the holes have been either straight or slightly tapered, the resistance to flow of air increasing as the holesare decreased in size. In any fuel bed, it is well known that the resistance to flow, or drop in pressure through the fuel bed is not uniform throughout its area and heretofore the straight or tapered holes or passages 30 have ofiered but little change in pressure drop with increased flow, in consequence of which the sections of the fuel bed, which offer decreased resistance to flow, either because of the character or thinness of that section of the fuel bed, 25 would be supplied with an excess amount of air, thereby increasing the combustion rate in such sections and resulting in burning out ofthe fuel bed on such sections relatively'faster than on other sections,

In order to overcome the aforementioned irregularity in combustion, grates with pin holes have been used. However, the holes are usually so small that high resistance to air fiow therethrough results, thereby making the pressure drop through the holes the predominating resistance. In other words, the holes'being of small area, the pressure drop through the grate is large compared to that of the fuel bed and variation in character or thickness of the fuel bed have but little effect on air fiow. With this type of grate, in order to secure necessary air flow higher differential pressures are required, making it essential to provide higher stacks, or, in the case of forced draft, larger blowers and increased 0 power for driving the latter.

In accordance with my invention, I provide a fuel-supporting structure wherein the air pas sages are constructed and arranged to give a variable resistance. to air flow therethrough with- 0 out the necessity of providing high differential pressures. This and other advantages are obtained by having the elements forming the fuelsupporting surfaces provided with means of securing a series of orificesin each air passage with chambers between adjacent orifices, the air passing through the orifices at high velocities and having the velocity energy largely transformed into static pressure in the chambers following the orifices.

In order that air may be sufiicient for suppo'rting combustion, there must be enough pressure difference between the space underneath the grate and the space above the fuel bed to overcome resistance to air fiow through the air passages of thegrate and through the fuel bed. 10 Ordinarily, the grate air passages offer little resistance, with the result that irregularities in fuel bed resistance may cause undesired irregularities in air fiow. For example, excess flow may occur in a region of small fuel bed resistance, thereby l5 increasing the combustion rate at such region and bringing about lessened pressure difference and consequent lessened flow through regions having greater fuel bed resistance. As hereinbefore already pointed out, an attempt to meet this objection has been made by providing very small air passages, but such small air passages are undesirable because of the consequent high pressure required to secure necessary air flow. It is well known that the-flow through an orifice is a function of the square root of the pressure difference across the orifice. Accordingly, instead of accomplishing increased resistance to air flow through a grate provided with relatively small passages, I provide a labyrinthine arrangement consisting of orifices with chambers between adjacent orifices. In other words, I provide for abrupt changes in area of flowfrom a chamber to an orifice and vice versa in each passage, the eflect of the abrupt flow area being to decrease the quantity of air flowing compared to a plain passage. The air has maximum velocities through the orifices, but, due to abrupt changes in area, large losses occur incident to changes of velocity energy into. pressure energy and 4 vice versa, and also definite energy losses due to conversions, with the result that, should there be a decrease in resistance at the discharge end of the passage, such decrease is compensated for by the increased effective resistance of the passage with very little increase inflow therethrough. This arrangement of orifices with chambers between adjacent orifices in the air passage causes the flow to increase at a lesser rate in case of diminishing fuel bed resistance than with, other types of air admitting grates. In other words, in accordance with my invention, grate resistance to air flow due to the losses from the changes in air velocity in passing through the alternate orifices and chambers is increased thus producing a choking effect against excessive air fiow without substantially increasing the air pressure required to secure the normal fiow. This choking effect increases the grate resistance to air fiow and tends to counteract the lower pressure drop through sections of the fuel bed of low resistance. This arrangement of air passage is more effective than the ordinary grate in equalizing the rate of air fiow through the various sections of high and low resistance in the fuel bed, thus securing more uniform combustion over the entire fuel bed area.

Accordingly, it is a more specific object of my invention to provide the air admitting passages of grate members each with a series of orifices and chambers between adjacent orifices, this arrangement functioning to prevent substantial irregularities of combustion with irregularities in fuel bed resistance.

These and other objects are effected by my invention, as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a transverse sectional view of a single retort stoker having my improvement applied thereto;

Fig. 2 is a sectional view taken along the line II-H of Fig. 1;

Fig. 3 is a fragmentary view of a chain grate having my improvement applied thereto.

Fig. 4 is a fragmentary detail view showing my improvement applied to tuyre plates of an underfeed stoker;

Fig. 5 is a bottom plan view of one of the tuyere plates shown in Fig. 4;

Figs. 6 and '7 show a further embodiment of the improvement applied to tuyre plates;

Figs. 8 and 9 are detail views of stoker grate bar elements embodying a second form of my invention;

Figs. 10 and 11 are sections taken along the lines X-X and XI-XI, respectively, of Fig. 9:

Fig. 12 is a view similar to Fig. 8 and showing a modified mode of securing variation in air fiow; Figs. 13, 14, and 15 are sectional views taken along the lines X[IIXI1I, IUVXIV, and XVXV, respectively, of Fig. 12;

Fig. 16 is a fragmentary view of a tuyre plate incorporating the second form of my invention; 'm

Figs. 17, 18, and 19 are detail views of side-wall tuyres incorporating my improvements, Fig. 19 being a sectional view taken along the lines XIXX[X of Fig. 18.

Referring now to the drawings more in detail, in Fig. 1, I show a structure including a retort, at l0, having sets of grate bars ll extending laterally therefrom, this being a well-known type of single retort underfeed stoker and which necessitates no further description in detail.

As is well known, fuel is supplied to the retort and fiows laterally over either side thereof onto the grate bars I I, the fuel advancing downwardly on the grate bars at either side of the retort and being consumed.

' Air for the combustion of fuel flows through the grates and fuel bed due to the pressure difference existing between the space I2 below the structure and the space l3 in the combustion chamber.

In order that a choking effect may be secured in the air passages between adjacent grate bars I I, in Figs. 1 and 2, I show the bars provided with ribs l4, l5, l3, and I! cooperating to provide first, second, third and fourth stage orifices l8, I9, 20, and 2| with chambers 22, 23, and 24 between adjacent orifices l8 and l9, l9 and 20, and and 2|, respectively, it being understood that, any suitable number of orifices arranged in series may be provided. In these figures, as well as the others hereinafter described, each air passage consists of one or more chambers and orifices leading to and from each chamber. This arrangement provides for 'abrupt changes in flow area where the orifices and chambers connect. The abrupt change in area is productive of inefficient conversion of velocity energy into pressure energy and vice versa and the effect thereof is to reduce the quantity of air discharged compared to a plain passage. With passages of this type, if the fuel bed is uneven, or if the resistance thereof varies, the differences in air fiow that would otherwise be induced by such variation tends to be equalized by the effect of the passages. While a decrease in resistance at the discharge end of a passage tends to increase the flow of air through the passage, because, of the abrupt area changes and consequent inefficient energy conversions, very little increase in fiow is required to compensate for the diminished resistance. Accordingly, with my improved grate surface, the tendency of air to fiow through thin places, or places of lesser resistance, with an undesirable loss in air and impaired combustion efficiency is overcome. With my arrangement,

. due to the inherent choking effect of each passage, variations in fuel bed resistance are largely compensated for by the operating efiect of the passages in consequence of which variations in fuelbedresistance are not accompanied by proportionate variations in air flow, to the regions of the fuel bed inconsistent with the actual requirements of the latter.

In Fig. 3, showing my improvement applied to a chain grate, the links 25 have ribs 26 at their sides which cooperate to define passages of varying area in the direction of fiow, as in Fig. 1.

Also the ends of the links have ribs 21 serving the same purpose.

In Figs. 4 and 5, I show my invention as applied to a series of tuyere plates 29 of an underfeed stoker, these plates being arranged in stacked relation and providing for the admission of air horizontally therebetween. The air passing from a region, at l2, at higher pressure to the combustion space, at l3, at lower pressure. The horizontal passages between adjacent tuyere plates are provided with a series of orifices and chambers to accomplish the effect already pointed out. To this end, referring to Fig. 5, I show the bottom side of the tuyere plate provided with a series of ribs 30, 3|, 32, and 33 which are notched as indicated at 34, 35, 38, and 31, respectively, the notches being suflicient in number and size in each'rib row to secure the desired orifice area. With the tuyere plates in position, as shown in Fig. 4, the rib rows 30, 3|, 32, and 33 rest on the fiat top surface of the tuyre plate immediately below, and the notches 34, .35, 36, and 31 are effective as first, second, third, and fourth stage orifices to secure the aforementioned choking efiect.

Instead of having notched ribs provided on the under surfaces of the tuyere plates, asshown in Figs. 4 and 5, each of such ribs may be made continuous and spaced from the top surface of the tuyere plate immediately below, the spacing of the respective ribs being such as to secure the desired orifice area. For-example, in Figs. 6 and 7 I show ribs 38, 39, 40, and H disposed in the direction of air fiow and arranged successively closer to the top surface of the tuyere plate immediately below so as to afford the desired first, second, third, and fourth stage orifice areas, the tuyere plates being supported in properly spaced relation by the projections la.

' To compensate for varying fuel bed resistance, the choking effect of the air passages may be varied along the fuel-supporting surface, this feature being illustrated in Figs. 8 to 15, inclusive.

In Figs. 8 to 11, inclusive, I show grate bars of the type illustrated in Fig. 1 and having lateral ribs 42, defining orifices, or air passages .of

varying area in the direction of fiow, as already pointed out in connection with Fig. 1; however, instead of having orifices or restricted passage portions of uniform widths from end to end of the grate bars, as in Fig. 1, such portions, in Figs. 8 to 11, inclusive, vary in width so as to compensate for variation in fuelbed resistance, the fiow resistance of the passages being less where the resistance of the fuel bed is a maximum and vice versa. To this end, it will be seen that the ribs 42 are not continuous but are divided into a plurality. of sections considered lengthwise of the grate bars, the sections being shown at 42a, 42b, and 420, adjacent sections, preferably, being separated by mating ribs 43 and 44.

The ribs 42a define orifices 45 of maximum width, the ribs 42b define orifices 45 of intermediate width, and the ribs 420 define orifices 41 of minimum width, the orifice width depending upon the fuel bed resistance.

Obviously, with the type of stoker shown in Fig. l, the fuel bed will be of maximum depth, and, therefore, resistance, at theforward ends of the bars, this maximum fuel bed resistance being at the sections 42a where the width of the orifices 46 is at a maximum. The fuel bed depth diminishes along the bars, being of inter mediate depth at the section 42b where the orifices 45 are of intermediate width, and being of minimum depth at the discharge ends of the bars, i. e., at the rib section 420, which define the orifices 41 of minimum width.

With this modification of the rib structure on the grate bars, it will be apparent that variation in the fuel bed resistance is compensated for by variation in passage resistance so that the tendency of air to flow excessively through the grate where the fuel bed is thin, is minimized.

Instead of varying the orifice width from end to end on the grate bars, as in Figs. 8 to 11, inclusive, the same result may be secured by varying the number of orificesat different sections along the bars. To this end, in Figs. 12 to 15, inclusive, I show grate bars having rib sections 48a, 48b, and 480 defining orifices 49a, 49b, and 490, respectively, the sections Ila being separated from the sections 481) by transverse mating ribs 50 and sections 48!) being separated from the sections 48c by ribs 5i. As the orifices 49d, 49!), and 490 are of uniform width, variation in reshown in Figs. 6 and '7, having lower ribs divided into sections 53a and itbadjacent'sections being separated by ribs 54, and the sections 53b being at the noses or tips of the tuyere plates. The rib sections 53a and 53b extend downwardly from the lower sides of the tuyre plates to cooperate with the upper horizontal surface of the next lowermost plate, as in Fig. 6. The rib sections 53a define orifices with respect to the upper horizontal' surface of the next lowermost plate which are wider than the orifices defined by the rib sections 531) at the tip or nose of the tuyere plate, whereby less resistance to fiow is afforded by the rib'sections 53a than the sections 53b, the fuel bed being, obviously, thicker above the lateral sections 53a than above the nose or tip rib sections 53b. Also, it will be apparent'that the ribs constitute spacing supports for the tuyere plates when the latter are disposed in assembled stack relation.

Thev general principles of my invention may also be applied to other types of structures used with combustion apparatus. 1 In Fig. 17, I show a sidewall tuyere 55 incorporating my invention,

each of the air passages 56 having. one or. more chambers 51 so that the portions of the passages to either side of the chambers serve as orifices. Here again, eaclr air passage has varying areas in the direction of flow so as to secure the effect already pointed out.

v 1 In Fig. 18, I show a modified form of sidewall sistance is secured by varying the number of orifices, the number of orifices being at a maxi mum where the fuel bed is thinnest and at a minimum where the fuel bed is thickest.

With an underfeed stoker, it is obvious that the fuel bed immediately above the tips or noses of the tuyere plates is at a minimum, for, if one views a tuyere row in the plane of the tuyeres, it will appear as a convex surface. Accordingly, in Fig. 16, I show tuyere plates similar to that tuyeres, where, instead of having an extensive or large casting such as indicated at 55 in Fig. 17, the tuyere device includes a'plurality of vertical sections or bars 58 disposed side by side. The sections have mating ribs 55 defining orifices 60, the

orifices being separated by chambers 6i. In this form, it will be apparent that each of the air passages has varying area in the direction of fiow for the purpose already pointed out.

From the foregoing, it will be apparent that I have provideda fuel-supporting or fuel-contacting surface through which air is supplied and wherein the air passages are so formed that variation in fuel bed resistance does not cause a large difference inflow of air through the different passages, that is', the passages prevent excessive flow of air to portions of the fuel bed where the fuel bed resistance is a minimum. While passages of uniform character for the entire bed are effective for this purpose, I may modify the' passages to suitthe varying character of the fuel bed. For example, if the fuel bed is normaly thicker at certain regions than in others, then the orifices may be arranged to afford less resistance to flow of air where the fuel bed is thickest and greatest resistance where the fuel bed is thinnest, the effect of the arrangement being that the variation in the air passages compensates for variation in fuel bed resistance. Variation in the air passages to compensate for variation in fuel bed resistance may be secured by either varying the number of orifices at different sections of the fuelsupporting surface, or by varying the sizes of the orifices at different sections, or by both.

While I have shown my invention in several forms, it wil be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is: I 1. In combustion ,apparatus, a grate including a a plurality of bars arranged side-by-side to provide vertical passages between adjacent bars for supplying air from the space below the grate to the space thereabove,'sald bars having spaced lateral ribs extending longitudinally thereof, the ribs providing orifices extending longitudinally of the bars and the spaces between adjacent ribs providing enlarged chambers extending longitudinally of the bars, each passage including a plurality of chambers and orifices with the chambers arranged between successive orifices,

2. In combustion apparatus, a grate including a plurality of bars arranged side-by-slde to provide vertical passages between adjacent bars for supplying air from the space below the grate to the space thereabove, said bars having spaced lateral ribsat each side and extending longitudinally thereof, similar and opposed ribs on adjacent bars forming a plurality of orifices separated by enlarged chambers formed by the spaces between adjacent ribs, whereby each passage includes a plurality of oriflceslwith the chain '5 arranged between successive orifices.

3. In combustion apparatus, a grate providing a fuel supporting surface having air admission openings and means cooperating with the grate to provide a multiplicity of chambers arranged in series in the direction of air flow, said means and the grate providing a plurality of spaced walls extending transversely of the direction of air fiow and defining and separating the chambers and to provide three or more spaced orifices in the v pasage between the elements, the spaces between adjacent ribs providing expansion chambers between successlve orifices.

EARLL R. STONE.

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