US2161031A - Vapor generator - Google Patents

Description

J. FLETCHER VAPOR GENERATOR June 6, 1939.

Filed Nov. 9, 1957 INVENTOR. Jameb" F/efc/ver Patented June 6, 1939 VAPOR GENERATOR James Fletcher, Akron, Ohio, assignor to The Babcock 62 Wilcox Company, Newark, N. 1., a corporation of New Jersey Application November 9, 1937, Serial No. 173,582

9 Claims.

and vapor separating chamber in which a liquid in pool is maintained. The liquid supply for the vapor generating tubes is drawn from the liquid space of the separating chamber and circulation maintained'either by natural circulation due to the dinerence in densities of the fluid in the downiiow and upflow portions of the circuit, or by a circulating pump, or by both pump and natural circulation. Regardless of the method in which fluid circulation is maintained, it is desirable that the liquid leaving the separating chamber through the'liquid discharge or downcomer tubes be as free from vapor bubbles as may be practicable, so that the vapor generatin tubes will have the least tendency to become dry andoverheat, particularly when the unit is operated at high vapor generating capacities. When the liquid and vapor mixture from the generating tubes is discharged into one side of the liquid and vapor separating chamber above the liquid level therein, the. entering velocity is normally high enough to cause the fluid streams or jets to flow across the vapor space of the chamher and to impinge with some violence on the opposite side wall of the chamber and then on the surface of the liquid pool or directly onto the pool surface, depending upon the initial direction of discharge and the liquid level. With such an arrangement I have discovered that the liquid in and adjacent to the area of impingement of the fluid jets is considerably agitated, and that a downward flow is set up in the pool towards the downcomer tubes. I have also found that a substantial amount of vapor is driven into the body of liquid in this area, so that vapor bubbles are present in the liquid stream flowing towards the downcomer tubes, which condition is undesirable.

Such undesirable separating chamber conditions can be prevented in accordance with my invention by the installation of a submerged 5o bailie along the side of the drum below the area of impingement 'ot the liquid and vapor discharge tubes, and arranged so as to resist downward motion of the fluid in that portion of the liquid space and to deflect the same upwardly away from the entrance to the downcomer tubes.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of' the invention, reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described several embodiments of my invention.

0f the drawing:

Fig; 1 is a sectional elevation of av steam and water drum of a water tube steam boiler of the Babcock 8t Wilcox crossdrum type incorporating my invention; and

Figs. 2, 3 and 4 are fragmentary views ofthe drum shown in Fig. 1 illustrating modlfled baifle l constructions.

In the drawing I have illustrated a horizontally extendingsteam and water drum It which is arranged in an elevated position relative to the main bank of steam generating tubes (not shown) of the steam boiler, and in which a normal water level is maintained slightly below the horizontal center line of the drum. As is well known, the steam generating tubes in boilers of the type described have their upper ends connected to the drum l0 through steam and water circulator tubes ll entering the drum along one side thereof slightly above the normal water level therein. Two rows of circulator tubes ll areillustrated, with the discharge ends of the upper row tubes inclined downwardly at a slightly greater angle than those of the lower row. Water is supplied to the lower end of the steam generating tube bank through downcomer tubes l2 radially connected to the bottom of the drum at opposite sides of its vertical center line. The drum I0 is also provided with steam washing and separating provisions of thezcharacter described in my prior application with L. Kooistra, Serial No. 7188', filed Feb. 19,-l935,-including a twin arrangement of corrugated plate separator sections I3 extending longitudinally of the drum in the upper portion of the steam space. The steam must pass through one or the other of the separator sections l2 before reaching the steam outlet tubes it. During the passage of the steam to the separator sections 13 it is washed by wash water, of greater purity than the moisture carried by the steam, discharged by a sprayer head l5, receiving boiler feed water through a pipe 16 and drainage from the separator section through pipes I! connected to an aspirating chamber in the feed water line. A substantially unobstructed space is thus provided across the drum in the flow path of the circulator tube discharge.

With the described arrangement of the circulator tubes H relative to the drum I0, streams or jets of steam and water will be discharged from the tubes at a relatively high velocity across the steam space of the drum. These streams either impinge directly upon the surface of the water pool along the opposite side of the drum, or indirectly by deflection from the opposite drum wall. I have found that this localized impingement of these. fluid streams causes violent agitation in the water pool of the drum, particularly in the portion adjacent the area of impingementand tends to create a downward fluid flow along the drum wall toward the-downcomer tubes l2. A substantial amount of steam bubbles has been found to be present in this circumferential stream, due to the presence of steam in the streams impinging on the drum water surface, and additional entrainment of steam by the streams from the steam space adjacent the area of impingement. The presence of a substantial amount of 'steam bubbles in the water passing to the downcomer tubes I2 disadvantageously affects the steam generation.

In accordance with my invention such operating difliculties are avoided bythe installation of a submerged baflle structure along substantially the entire length of the drum wall opposite the circulator tube connections at a level between the area of impingement on the water surface and the downcomer tube connections, such bafile means being arranged to obstruct any downward flow in the pool along the drum wall and deflect the same upwardly towards the surface of the pool. In Fig. 1 the baflie structure is formed by a flat baflie plate 20 arranged radially of the drum, with its lower end in contact with the drum wall. The baflle plate is held in position by spaced supporting brackets 2|, with the baffle plate and brackets preferably welded to the inner wall of the drumn F g. 2 t b fi e outlet above the normal water level therein, tubes plate 20 is provided with stepped parallel baiile plates 22 and 23 to provide for variations in the drum water level. The plates 22 and 23 are supported from the baffle plate 20 by spaced supporting clips 24, as illustrated. In Fig. 3 the inner end of the baflie plate 20 is curved upwardly as indicated at to increase the upward deflecting action of the baflle, while in Fig. 4 the bafile plate 20 is curved throughout its transverse extent.

All of the baflie constructions illustrated are of extremely simple form, easy to manufacture and install, and highly effective in operation. The

described baflle location in the drum also avoids interference with access to the circulator tubes II and downcomer tubes l2 for inspection or replacement of the same.

While in accordance with the provisions of the statutes I have illustrated and described herein the best forms of the invention now known to me, those skilled in the 'art will understand that changes may be made in the form of the baflles disclosed without departing from the spirit of the invention covered by my claims, and that my invention may be used to advantage in other vapor generators having separating chambers of the character described.

I claim:

1. In a vapor generator, a liquid and vapor separating receptacle having a vapor outlet above the normal liquid level therein, a conduit connected to said receptacle above said normal liquid level and having its discharge end arranged to discharge a fluid stream through the vapor space of said receptacle and so as to impinge upon the surface of the liquid therein, a submerged liquid discharge conduit connected to said receptacle, and a normally submerged baffle extending inwardly from the receptacle wall between the area of impingement on said liquid surface and said liquid discharge conduit and arranged to obstruct the passage of fluid downwardly along said geceptacle wall towards said liquid discharge conuit.

2. In a vapor generator, a liquid and vapor separating receptacle having a vapor outlet above the normal liquid level therein, a conduit connected to said receptacle above said normal liquid level and having its discharge end arranged to discharge a stream of liquid and vapor through the vapor space of said receptacle and so as to impinge upon the surface of the liquid therein at the opposite side of said receptacle, a liquid discharge conduit connected to the bottom of said receptacle, and a normally submerged baille extending along the receptacle wall at said opposite side between the area of impingement on said liquid surface and said liquid discharge conduit .and arranged to obstruct the passage of fluid downwardly along said receptacle wall at said opposite side towards said liquid discharge conduit.

3., In a water tube steam boiler having a steam and water separating chamber with a maintained water level, an entering connection from the gen-- crating tubes at the side and above the water level, a leaving connection to the generating tubes below the water line, and a submerged baffle attached to the side of the chamber opposite the entering connection arranged to resist downward motion of fluid by impact of the jet originating at the entering connection.

4. In a water tube steam boiler, a horizontally arranged steam and water drum having a steam connected to said drum along its length above charge ends arranged to discharge streams of steam and water through the steam space of said drum and so as to impinge upon the surface of the water therein, downcomer tubes connected to the bottom of said drum, and a normally submerged bafile extending along the drum wall between the area of impingement on said water surface and said downcomer tubes and arranged to obstruct the passage of fluid downwardly along said drum wall towards said downcomer tubes.

5. In a water tube steam boiler, a horizontally arranged steam and water drum having a steam outlet above the normal water level therein, tubes connected to one side of said drum along its length above said normal water level and having their discharge ends arranged to discharge streams of steam and water through the steam space of said drum and so as to impinge upon the surface of the water therein at the opposite side of said drum, downcomer tubes connected to the bottom of said drum, and a normally submerged baille extending along the drum wall at said opposite side between the area of impingement on said water surface and said downcomer tubes and arranged to obstruct the passage of fluid downwardly along said drum wall at said opposite side towards said downcomer tubes.

6. In a water tube steam boiler, a horizontally arranged steam and water drum having a steam outlet above the normal water level therein, tubes connected to one side of said drum along its length above said normal water level and having their discharge ends arranged to discharge streams of steam and water through the steam space of said drum and so as to impinge upon the surface of the water therein at the opposite side of said drum, downcomer tubes connected to the bottom of said drum, and a normally submerged fiat bailie plate extending radially of said drum along and in contact with the drum wall at said opposite side between the area of impingement on said water surface and. said downcomer I tubes and arranged to obstruct the passage of streams of steam and water through the steam space of said drum and so as ,to impinge upon the surface of the water therein at the opposite side of said drum, downcomer tubes connected to the bottom of said drum, and a normally submerged bafile extending along the drum wall at said opposite side between the area of impinge ment on said water surface and said downcomer tubes and arranged to obstruct the passage of fluid downwardly along said drum wall at said opposite side toward said downcomer tubes, said baille comprising a series of stepped parallel plates.

8. In a water tube steam boiler, a horizontally arranged steam and water drum having a steam outlet above the normal water level therein, tubes connected to one side of said drum along its length above said normal water level and having their discharge ends arranged to discharge streams of steam and water through the steam space of said drum and so as to'impinge upon the surface of the water therein at the opposite side of 'said drum, downcomer tubes connected to the bottom of said drum, and a normally submerged baflle plate extending along and in contact with the drum wall at said opposite side between the area of impingement on said water surface and said downcomer tubes and arranged to obstruct the passage of fluid downwardly along said drum Wall at said opposite side towards said downcomer tubes, said bafile plate having its inner end upwardly curved.

9. In a water tube steam boiler, a horizontally arranged steam and water drum having a steam outlet above the normal water level therein, a steam and water separator connected to said outlet and arranged within said drum above said normal water level, circulator tubes connected to one side of said drum along its length above said normal water level and having their discharge ends arranged to discharge streams of steam and water across said drum through a substantially unobstructed horizontal flow path extending to the Opposite side of said drum and between the bottom of said separator and said normal water level, downcomer tubes connected to the bottom of said drum, and a normally submerged baflle plate extending along the drum wall at said opposite side and arranged to obstruct the passage of fluid downwardly along said. drum wall at said opposite side towards said downcomer tubes.

J All/LES FLETCHER.

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