US3195871A - Steam expansion chamber - Google Patents

Description

July 20, 1965 J. B. PRATHER 3,195,871

STEAM EXPANSION CHAMBER Filed Aug. 16, 1961 2 Sheets-Sheet 1 July 20, 1965 J. B. PRATHER STEAM EXPANSION CHAMBER 2 Sheets-Sheet 2 Filed Aug. 16, 1961 INVENTOR John B. Prather United States Patent O 3,195,871 STEAM EXPANSION CHAMBER John B. Prather, Hastings on Hudson, N.Y., assigner to Gibbs & Hill, Inc., New York, N.Y., a corporation of New Jersey Filed Aug. 16, 1961, Ser. No. 131,932 6 Claims. (Cl. 261115) This invention relates to an apparatus for the expansion ofgases and more particularly to an apparatus for controlling the expansion of relatively large volumes of steam and especially to a chamber for dumping steam from a by-pass for a turbine into the exhaust for the turbine.

In the steam-electric industry it has become increasingly common practice, and in many cycles imperative, to furnish a means for by-passing steam around the turbine. Such steam is normally dumped into the turbine exhaust system. Even where by-passing steam is not essential, a by-pass adds greatly to the flexibility of operation of steam operated turbines. Thus by-pass systems serve a number of functions depending upon the type of power unit in which they are installed. In general, however, they may be classified under one of the following categories:

(a) By-pass to match steam and metal temperatures in a conventional fossil fuel cycle. This serves to avoid excessive thermal shock in the turbine at start-up.

(b) By-pass for start-up and trip-out when a oncethrough type boiler is used. By this me-ans water and steam are recycled until proper steam flow and steam temperature are established prior to starting and loading the turbine generator.

(c) By-pass for start-up and trip-out in a nuclear fuel cycle. In some nuclear power plants a by-pass may be required for starting a secondary steam cycle. This also provides a means for conserving valuable condensate when the electrical load is dumped and the residual reactor heat must be dissipated.

Although different purposes are served by each of the by-pass arrangements mentioned above, certain design criteria are common to all for, in each case, provision must be made for cooling and throttling a considerable quantity of superheated steam which is then dumped into the exhaust system for the turbine. Considerable data is available, and considerable work has been done, on throttling and cooling the by-pass steam before it reaches the exhaust for the turbine. For example, throttling is accomplished by expansion through reducing valves, pipl ing, and a series of orifices of increasing area and water sprays are used to cool the steam. Yet important unsolved problems are involved in dumping the steam from the by-pass conduit at several atmospheres, or as high as 100l50 p.s.i., and often at temperatures in excess of 175 F. which is the maximum temperature normally accepted by the industry. As stated the steam is normally dumped into the exhaust for the turbine, or into the main condenser, operating at a relatively low absolute pressure of a few p.s.i. For instance, systems devised heretofore for dumping steam at several atmospheres, or higher, to relatively low turbine exhaust temperatures and high vacuum have resulted in extreme noise, vibration (in some cases fatigue failure) and serious erosion.

It is an important object of this invention to provide Cil ice

a simple, compact, and low cost gas expansion device which will solve problem-s last mentioned above and related problems. It is a more specific object of the invention to provide an expansion chamber which will expand large quantities of by-pass steam and control its temperature so that it can be dumped, or exhausted, into the exhaust, or condenser, for the turbine without creating uncomfortable noise levels or damaging vibrations.

Other objects, advantages and features of the invention will be apparent from the more detailed description which follows.

The invention will be described by reference to a particular embodiment of the invention shown in the accompanying drawings.

In the drawings:

FIG. l is a vertical section of an expansion chamber from which by-pass steam can be dumped to the exhaust line of a turbine;

FIG. 2 is a perspective view of the expansion chamber of FIG. 1; and

FIG. 3 is a flow diagram of .a steam by-pass for a power plant utilizing the expansion chamber of FIGS. 1 and 2.

In the Various figures the same num-bers are used to represent like elements. As shown in FIGS. 1 and 2, the steam enters the dump chamber 11 through a pipe 12 located at the .axis of a series of alternately facing and nested semi-cylindrical diaphragms 13, 14, 15, 16 and 17 of progressively larger radii. Pipe 12 is provided with a series of holes 18 in the side facing the innermost diaphragm 13 constituting orifices through which steam can expand into the space between pipe 12 and diaphragm 13. To prevent spillover between cylinders, to provide means for supporting the cylinders and to hold them in spaced relationship, and to provide substantially rectangular nozzles 18, 19, 20, 21 and 22. through which the steam can expand the various cylinders are overlapped by 5 to 10 of arc and provided with supports 27 described in detail below. The steam also expands as it flows through the nozzle 23 formed between diaphragm 17 and the outer walls of the chamber 24. There is a further expansion when the steam flows through the outlet 25 into the exhaust system.

It will be seen from the flow line 26 that following each expansion between each diaphragm and between the outer diaphragm and the wall of the chamber the steam undergoes a path reversal of during which no work is done. The kinetic energy, therefore, is dissipated and the steam is reheated at constant pressure towards its original enthalpy. Thus, on a theoretical basis, the stages of expansion are isenthalpic. The expanding steam follows this pattern from stage to stage until it has reached condenser pressure. Nozzle 4areas formed by overlapping diaphragms are selected to avoid sonic steam velocities or at least objectionable noise levels.

The semi-cylindrical diaphragms are supported and held in spaced relation by lateral supports 27 and by longitudinal support 28. The support-s 27 are positioned to interfere as little as possible with the flow of steam while the support 28 serves the dual function of forming a partition, or dam, in the space between adjacent nested diaphr-agms whereby whirling of the steam is minimized and an even distribution of the steam is facilitated.

In order to control the enthalpy of the steam, water Y Y `is brought into a low pressure area of the expansion chamber throughconduit V29 andr branch conduit 30 and injected into the steam in the low pressure area through nozzles 31where it flashes into steam. In order to realize aV temperature of notV more than 175 F., it is seen the water should be introduced into a low pressureregion of the expansion chamber at which the pressure is that of tion of low cost material and simplicity of design makes it possible to provide the expansion Chambersatvery rea-l sonable costs.

The expansion chamber (actually two were used) has proven fully satisfactory-in `use in a by-pass for' a 150 mw. turbine in a steam-electric power plant using aoncethrough boiler. The steam-electric unit wasjdesigned Vto operate at 2400 p.s.i.g. kand 1000 F. with reheatto 1000 Althoughthe invention has beenldescribed with referenceto'the structural details of a particular embodiment illustrated in the drawings, it is to be appreciated Vthat the invention is not to be considered to be limited to all of the detailsthereof. The invention contemplates various combinations of structural features of the illustrative embodiment Within the spirit of the invention and the'scope ofthe invention as defined vin the appended claims. f Y

' What is claimed is: Y

1. A gas expansion chamber comprising: first, second Vand third diaphragms each having opposite ends, opposite edges, and a concave surface, the concave surface of said rst diaphragm facing the' concave surface of said second diaphragm Ywith the .edges` of said second diaphragm lstraddling said first diaphragm and overlapping and spaced P. This system is shown diagrammatically in 'FIG.3.

As shown in FIG. 3, steam from the superheater is expanded through valve 40gand is mixed with water spray at 41, after which, it enters separator d2.V The steam then flows through reheater'43 serving to protect the reheater against excessive temperatures. Thereafter the steam flows through `conduit 44'to spillover valve d5, which is adjusted so asV to limit the downstream pressure,

namely, that-enteringthe expansion chamber 11V to 100 Reduction in the enthalpy of the steam is accomf p.s.1. plished inVY the VVmixing chamber 45l located .between the spillovergvalve and the Vdump chamber. sion chamber 11, the temperatureis further reduced in the manner described before by'theaddition of a water spray at a point in the expansion chamber where the pressurev has been reduced'to that of saturated steam at 160 F. In this way, thesteam can be dumped into the exhaust of the turbine at a temperature `below the required 175"Y F. and at apressure which will not cause excessive vibration yand sonic disturbances even Ythough the pressure in the exhaust does not exceed several pounds or even )1.5 inches mercury'absolute, i.e., 28.5 inches vacuum.'

In the actual operation of the .steam-electric power plant two expansion chambers 11, as shown in'FIGS.` 1 and 2, were located on the fiat but slopingsides of the Va first distance from the .edgesrof said first diaphragm, the

concave surface kof said third diaphragm facing 'the ccncave surface ofsaid second diaphragm `withftheredges of said thirdfdiaphragm'- straddlingsaid second diaphragm and overlapping vand spaced a second distance from the edges of said second diaphragm, saidV second distance being greater than said first distance'fir,st (wall-forming means closing one endof said firstdiaphragm and the correspondingends of said second and third diaphragms except for an aperture locatedin said wall-forming means between said first and' second diaphragms, second wall-forming means closing the ends of said first, second and third diaphragms oppositethe ends closed by said first Wallfor'ming means, first nozzle-forming wall means extending between and attached between'one pair of overlapped edgesv of said first and second diaphragms, second nozzleforming wall means extending between and attached' between one pair of overlapped edges of said second and third diaphragms, one of said edges of each ot said pairs of edges being the same edge, said first and second nozzleforming wall-means assisting in conjunction with said In the expan- Y pairs of edges and said lfirst and second wall-forming means in channeling gas flow as well as supporting said first, second and Vthird diaphragms relative tok one another and permitting desired gas expansion.

2. The combination of claim 1i including a gas inlet pipe extending through said aperture and terminating between condenser neck 47. These dumprchambers were approximately 85" wide, 60'.y high, and 58 long. Theyv Y were made of carbon steel described above. f

It is obvious the gas expansion chamber of this invention is extremely versatile'in use and is notIlimited to use in the steam by-pass cycle of a .power plant. Y For inf.A

stance, it will'find wide usage for the expansion of gases and the reduction of temperature in the petroleumY indus-l try. It is Yapparent the number of diaphragms can'be increased at willr and that a series of orifices of increasing plates formed and welded asl areacan be 'provided solthat the velocities therethrough advantages inherently'resid'ein the use of semi-cylinders or substantially semi-cylinders, as baffles.. It is'apparent,

however, that the principles of the invention can be practiced with any type oftrough-like alternately facingrand` nesting overlapping elongated diaphragms and the e'xpresf Y sion substantially semicylindricalf' contemplates suchV devices. Y

said first and second diaphragms, the portion of said pipe between said 'first and' second diaphragms including at least one aperture facing said first diaphragm.

3. The Vcombination of claim 2 including first partition means extendingV .betweenY said pipe and said first diaphragm and second partition means extending between said pipe and said second vdiaphragrm'said first and secondpartition means being located substantially perpendicular to said first nozzle-forming wall means and assisting in providing mutual Vsupport for said pipe and said first and second diaphragms. Y

4. The combination of claim 3 including additional diaphragms,'each of rsaid additional diaphragms having a concave surfacejwhich faces and atleast'partially surrounds'said first, second and third diaphragms, and'means for introducing a fiuid other than said gas between at least two of said diaphragms. i

l5.The combination of claim v1 including a gas inlet pipe 'extending through said aperture and terminating between said first and'second diaphragms in a closed end, theY portion of said pipe-between saidy first and second diaphragms including a plurality of apertures opening toward said first-diaphragm. f

'6. vThe combination of claim 5 including rst partition means extending between said `pipe and said rst diaphragm, second'partition meansextending between said pipe andV said ksecond diaphragm, and third partition means extending between said first and third diaphragms, said first, second and .third partition means lyingsubstantially perpendicular to said-'first and vsecond nozzle-forming wall means, certain o f said plurality of apertures lying on opposite sides of said firstV partition means, whereby said 5 6 partition means provide mutual support for said pipe and 1,934,667 11/ 33 Harter 60--1 said rst, second and third diaphragms and further prO- 2,137,300 11/ 38 Allen 137-574 vide two flow paths for gas emitted from said pipe. 2,161,060 6/39 Kelsey 137-574 References Cited by the Examiner 5 FSOREIGN PATENTS 241,602 10/2 Great Britain. UNITED STATES PATENTS 477,269 1/53 Italy. 582,813 5/97 Dillon 55--441 B52? mmm-:m-

HARRY B. THORNTON, Primary Examiner. 1,044,208 11/ 12 Luhn 55-444 10 RONALD R. WEAVER, ROBERT R. BUNEVCH,

1,214,103 1/ 17 Williams 60--95 Examiners.

Claims (1)

1. A GAS EXPANSION CHAMBER COMPRISING: FIRST, SECOND AND THIRD DIAPHRAGMS EACH HAVING OPPOSITE ENDS, OPPOSITE EDGES, AND A CONCAVE SURFACE, THE CONCAVE SURFACE OF SAID FIRST DIAPHRAGM FACING THE CONCAVE SURFACE OF SAID SECOND DIAPHRAGM WITH THE EDGES OF SAID SECOND DIAPHRAGM STRADDLING SAID FIRST DIAPHRAGM AND OVERLAPPING AND SPACED A FIRST DISTANCE FROM THE EDGES OF SAID FIRST DIAPHRAGM, THE CONCAVE SURFACE OF SAID THIRD DIAPHRAGM FACING THE CONCAVE SURFACE OF SAID SECOND DIAPHRAGM WITH THE EDGES OF SAID THIRD DIAPHRAGM STRADDLING SAID SECOND DIAPHRAGM AND OVERLAPPING AND SPACED A SECOND DISTANCE FROM THE EDGES OF SAID SECOND DIAPHRAGM, SAID SECOND DISTANCE BEING GREATER THAN SAID FIRST DISTANCE, FIRST WALL-FORMING MEANS CLOSING ONE END OF SAID FIRST DIAPHRAGM AND THE CORRESPONDING ENDS OF SAID SECOND AND THIRD DIAPHRAGMS EXCEPT FOR AN APERTURE LOCATED IN SAID WALL-FORMING MEANS BETWEEN SAID FIRST AND SECOND DIAPHRAGMS, SECOND WALL-FORMING MEANS CLOSING THE ENDS OF SAID FIRST, SECOND AND THIRD DIAPHRAGMS OPPOSITE THE ENDS CLOSED BY SAID FIRST WALLFORMING MEANS, FIRST NOZZLE-FORMING WALL MEANS EXTENDING BETWEEN AND ATTACHED BETWEEN ONE PAIR OF OVERLAPPED EDGES OF SAID FIRST AND SECOND DIAPHRAGMS, SECOND NOZZLEFORMING WALL MEANS EXTENDING BETWEEN AND ATTACHED BETWEEN ONE PAIR OF OVERLAPPED EDGES OF SAID SECOND AND THIRD DIAPHRAGMS, ONE OF SAID EDGES OF EACH OF SAID PAIRS OF EDGES BEING THE SAME EDGE, SAID FIRST AND SECOND NOZZLEFORMING WALL MEANS ASSISTING IN CONJUNCTION WITH SAID PAIRS OF EDGES AND SAID FIRST AND SECOND WALL-FORMING MEANS IN CHANNELING GAS FLOW AS WELL AS SUPPORTING SAID FIRST, SECOND AND THIRD DIAPHRAGMS RELATIVE TO ONE ANOTHER AND PERMITTING DESIRED GAS EXPANSION.

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