US1349869A - Marine boiler - Google Patents

Description

J. E. BELL, MARINE BOILER. APPLICATION FILED NOV. 23, 1918.

1,349,869. I Patented Aug. 17,1920.

3 SHEETS-SHEET 1.

J. E. BELL.

MARINE BOILER. APPLICATION FILED NOV. 23, 1918.

Patented Aug. 17, 1920.

3 SHEETS-SHEET 3.

UNITED STATES PATENT OFFICE.

JOHN E. BELL, OF BROOKLYN, NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

FOSTER MARINE BOILER CORPORATION,

NEW YORK.

OF NEW YORK, N. Y., A CORPORATION OF MARINE BOILER.

Application filed November 23, 1918.

. zen of the United States, residing at Brooklyn, county of Kings, and State of New York, have invented certain new and useful Improvements in Marine Boilers, of which the following is a full, clear, and exact descri tion.

7 On arch 1, 1918, I filed in the United States Patent Oflice an application for improvements in marine boilers, Serial No. 219,924, in which, among other features of invention, was shown a novel arrangement of boiler tubes, which is now made in part the subject of this application. The practical use of this boiler and exhaustive tests of its operation have demonstrated the existence of certain very important characteristics and possibilities which I have taken advantage of and the improved constructions and combinations which I have found that it permits, are also included in this application.

The application, therefore, is based upon a novel plan of boiler tube spacing, upon a system of bathing used in connection there with, and upon the combination with the said boiler tubes of a superheater arranged in certain novel and very effective relations therewith.

In the accompanying drawings which illustrate the above-named features of novelty Figure 1 is a cross-sectional view of the boiler structure as a whole.

Fig. 2 is a vertical cross-section at right angles to Fig. 1.

Fig. 3 is a part sectional front elevation of a portion of the banks of tubes, and

Fig. 4e is a similar view of a modification of the tubes.

The boiler to which-this invention will be shown and described as applicable is one of the marine type designed by me, and WhlCll, for purposes of the present case, may be described as comprising a suitable setting 1, the walls of which are built up in any proper manner, containing a fire boa: 2, which may also be of the usual character. The boiler proper is composed of continuous box-shaped headers connected by straight tubes 3 which, as usual, should be inclined Specification of Letters Patent.

Patented Aug. 17, 1920.

Serial No. 263,828.

pipes, and usually with a superheater 5, and a special arrangement of bafiles which will be more fully described hereinafter. In the outer wall 6 of the headers are hand-holes in line with the boiler tubes, and these are closed with suitable nut drawn plugs 7 As 1s also customary in such boilers, the header plates are connected by stay bolts 8, which in this instance are hollow, to permit of the introduction of a steam or air lance into the boiler for cleaning the tubes.

As shown in Fig. 3, every other boiler tube 3 is omitted from the second row and every other alternate row, at the points occupied by the stay bolts, by which means each hollow stay bolt is at the center of a cluster of six boiler tubes and affords a very effective and convenient means for cleaning or dusting the tubes by means of an introduced steam or air lance.

This specific arrangement of tubes is not essential provided the advantages which it secures are still retained. For example, in Fig. 4:, considering for the moment the general plan of spacing, the boiler tubes 3 are disposed in double rows, spaced so as to admit of stay bolts between each two rows. The tubes of one row of each pair are placed opposite spaces in the accompanying row, and the stay bolts occupy a like relative position to the tubes of adjacent rows. By this arrangement the same provision for cleaning the boiler tubes is afforded, each hollow stay bolt being at the center of a cluster of four boiler tubes.

The boiler tubes in the closely-spaced'rows are very close together so that the gas velocity is high and bafiling largely dispensed with. It will also be observed that the streams of hot gas passin between the tubes of the closely-spaced rows expand and mix before they impinge directly upon the tubes in the next succeeding row, owing to the position of the widely-spaced tubes, while fit) gases .in a sinuous path through the bank of tubes, the direction of travel, in the main, being at right angles to all the tubes and over the superheater.

The tube arrangement described, in effect, consists of a number of banks of screens formed by closely spacing the tubes with open spaces between them. The gases of combustion pass through the bank of tubes at high velocity and the temperature gradient along the sides of the tubes is that usually met with in boilers of the cross-pass type. In the open spaces the gas streams intermingle, due to the creation of eddies and the lowering of the velocity of flow so that the temperature gradient is destroyed and the gases are at a uniform temperature and contact with the next succeeding row with this temperature established. Thus a very steep temperature gradient actson the lower sides of the tubes, or the points of first contact, which results in a more rapid transfer of heat than is obtainable from a uniform flow with the attendant temperature gradient. The difference between the ordinary and this new means of heat transmission is somewhat analogous to the action in mechanics of an ordinary force and a force due to impact.

Primarily, the omission of every-other boiler, tube in every-other row, or its de scribed equivalent, is of great advantage, because the vacant space may be occupied by the hollow stay bolts. This enables me to space the boiler tubes as closely together as the metal of the end plates of the header permits, with the result of greatly increased efficiency and a marked reduction in the space occupied by a boiler of given capacity. It would be impossible to get a steam lance into the boiler from either side with this close spacing of the tubes, but the close tubespacing, together with the stay bolts, affords a ready means of cleaning.

The special arrangement of close spacin of the boiler tubes, it may be further stated has certain peculiar advantages. It is weli known that the rate at which heat is absorbed from a hot gas by a cooler surface is almost directly proportional to the velocity of the gas over that surface, or, more strictly speaking, to the product of the velocity and the density, or what is known as the mass flow. To secure this high velocity, it has been customary to insert in boilers, baflies which have a tendency to in.-

crease the length of the path of gases from the furnace to the gas outlet. It has, moreover, been demonstrated by experiment, that when the gas passes over the tubes in a direction at right angles to their axes, the absorption of heat is at a greater rate for a given velocity than when the gas travels along the tubes. As a result, in the most eflicient form of boiler the baflies are arranged to secure a transverse passage of the gases, but this usually involves the forcing of the gas to make two or three complete and abrupt turns, and is accompanied by a loss of draft. If this loss be too high, the capacity of the boiler is reduced, so that the ideal arrangement of baffling is that which gives the maximum of heat absorption with the minimum of draft loss.

In the boiler herein shown and described, a high velocity of gas travel is secured by spacing the boiler tubes close together rather than through the use of the more ordinary systems of baffiing. The sharp turns in the gas path around the usual baflies will not therefore occur, so that the draft loss is low, and in the main the gases travel across the tubes and not along them.

In this boiler also the peculiar spacing of the tubes adopted, together with the special bathing shown, results in a better distribution of the furnace gases over the heating surface, and forces them into the spaces under and over the baffles, and in particular preserves a general flow transversely to the tube length through the narrow spaces between the tubes, the flow longitudinally to the tubes being to a large extent through the wide spaces. That such is the ease has been demonstrated by experiment and is otherwise proven from the con sideration that to obtain a high velocity through the narrow spaces there must be an excess of gas pressure at the point of maximum velocity on the entrance side of the narrow space or a negative pressure on the outlet side. In the first instance the excess pressure would cause a gas current to flow longitudinally with respect to the boiler tubes, away from the points of higher velocity, which would eventually tend to equalize the velocity of the transverse flow.

In the second instance assumed, a longitudinal flow of gas toward the points where the gases left the narrow spaces high velocity would be caused and this would therefore choke such flow and again tend to equalize the transverse velocities.

In other words, the combination of nar row and wide spaces is such that for practical purposes the gas stream can be said to be cut and the different layers shifted, and the special baffling used takes full advantages of this.

Boilers of this general type have in the past been constructed with a horizontal cen ter to center spacing of the tubes from one and three-quarters to more than twice the tube diameter, but the spacing I recommend is less than one and one-quarter times the diameter, a difference that has a marked effect upon the performance of the boiler.

It may also be stated that I prefer locating the baflles over a row of tubes with narrow spacing so as to increase to a maximum the area of contact between the tubes and battles, and I have found as a result that it is possible to use metal plate bafiies throughout, which are kept from attaining too high a temperature by reason of the conduction of heat to the cooler surfaces of the tubes through this large area of contact, and hence they do not burn out as they otherwise would.

A special feature of improvement has also been found possible in this boiler which is illustrated in Fig. 4. The lower baffles 12 are placed above the first row of closelyspaccd tubes which are not at the bottom of the bank, as below such row are at least two rows of wide or doul. lc-spaced tubes. These two rows prevent the closing of the spaces between the tubes by crust of ash and clinkers and afford a free and enlarged passage up to and between the baffles for the flow of hot gases to the boiler tubes. This has been found to be a most desirable arrangement.

Having now described my invention what I claim is:

1. In a boiler of the kind described, the combination with transverse rows of boiler tubes, alternate rows being very closely and widely spaced respectively, whereby longitudinal channels will be formed between the rows of closely spaced tubes, of short battles in contact with a row of closely spaced tubes at each end of the same in the upper and lower parts of the bank of tubes, and a wider intermediate central bafiie with gas passages at both ends, whereby the hot gases will be caused to flow horizontally through the channels and more equally upward between the closely spaced tubes.

2. In a boiler of the kind described, the combination with rows of tubes, some of which are closely spaced with intermediate rows of widely-spaced tubes, whereby a lateral flow of gases in the wider spaces will cause said gases to pass more equally through the narrow spaces and transversely to the tubes, of short end bafiles between the rows of tubes, and a wider central baffle above the same with gas passages at both ends.

3. In a boiler of the kind described, the combination of a bank of tubes with a space between the upper and lower portions of said bank for a superheater with its tubes at right angles to the boiler tubes, the tubes in said portions being in rows spaced closely together and having wide spaces between tubes in adjacent rows, of central baffles and short side baffles both above and below the superheater space, for the purpose herein set forth.

In testimony whereof I hereunto aflix my signature.

JOHN E. BELL.

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