US2126248A - Steam generator with forced passage of the operating medium - Google Patents

Description

Aug. 9, 1938. M. EULE 2,126,248

STEAM GENERATOR WITH FORCED PASSAGE OF THE OPERATING MEDIUM Filed March 12, 1937 2 sheets-sheet 1 0f wafer *deo/77 Wafer Wafer* I cab/aci j I' F fr@ 'f2' i LI C ATTORNEY.

STEAM GENERATOR WITH FORCED PASSAGE OF THE OPERATING MEDIUM 42 sheets-sheet 2 M, EULEA Filed March 12, 1957 FUEL und Ffm Aug. 9, 1938.

MJ FUR.

INVENTOR Mam-:N EULE .1

a @www ATTORNEY Patented ug. 9, 193s wie@ i UNITED NsrATes PATENT orsi-cs- Y 2,126,248.j v I f v STEAM GENERATOR wrm Foiaoni)` pas'` SAGE THE OPERATING MEDIUM Y Martin Eule, Berlin-Spandau, Germany, assigner to Siemens-Schuckertwerke Aktiengesellschaft, Berlin-Siemensstadt, Germany, a corporation of Germany Application March 12, 1937,` Serial No. 130,477

In Germany November 23, 1934 3 claims. (ci. 1272-443) My invention relates to steam generators of the forced-flow tubular type and it has for an object to provide a control system therefor wherein elTec'ts of lag, so far as the temperature impulse `is concerned, are substantially avoided. This application is a continuation in part of application Serial No. 50,860, led by me on November 21, 1935 for Steam generators with forced passage of the operating medium.

A further and more particular object of my invention is to modify the steam-producing conditions of one ofthe tubes of a plurality of parallel-connected tubes so that said tube will `have a region of variable temperature overlapping a portion of the evaporation zone of the remaining tubes, or within the physical limits of the latter, whereby there is provided a tube region of Variable temperature within the main evaporation zone and which region may be used to provide a temperature impulse for the controlling apparatus.

In steam. generators of the above character, the supply of the operating medium and the fuel must be varied in such a manner as to ap- `proximately maintain a. predetermined ratio of both operating mediaif in the case of variations of load the condition of the steam produced is tolremain unchanged. This may be also accomplished by the two regulating methods which, as a rule, have hitherto been employed. By one of the regulating methods the operating medium `and the fuel is simultaneously supplied Ain a greater or smaller amount depending upon the desired output, in which case a Correction impulse is caused to be transmitted in response to the steam temperature for ensuring a reliable regulation thereof, which impulse in addition acts upon the supply of fuel. According to the other method the supply of the operating medium and the fuel is not varied simultaneously, but in succession; that is tosay, the supply of the operating medium is at rst adjusted to the vdesired new value and then the supply of fuel is regulated by an impulse, derived in response to a variation of the temperature of the steam produced. In both regulating methods, the derivation of an impulse in response to the temperatureof the steam produced plays an important part. For the transmission ofthis temperature impulse only two'points of the heating surface of the steam generator had hitherto been taken into consideration; viz. the superheater and the preheater. The derivation of the impulse from these parts of the heating surface is, however,

not fully satisfactory. An impulse derived. from It is thus possible to` derive `the `temperature impulses to a'sufcient extent from a heating sur- `heating surface. complished in the simplest manner by reducing tube withfrespect to the other tubes. i case, it is only necessary to insert in this tube the superheater arrives, as a rule, too late. The regulation effected by this impulse, consequently,

-lags considerably, whereas the derivation of the impulse at the preheater is effected so prematurely that considerable variations of the operv yating conditions may again occur at the end of vne'cted'in parallel and forming the heating sur- 4`face is so regulated with respect to the-other Ttubes that in this partiulartube the preheating terminates later or the superheating begins earlier than in the other tubes and that the temperature impulseis derived frcmthis tube from a `point wherethe preheating terminates or the 'superheating begins.

NvIf the impuls-e in response to the temperature fof the superheatedsteam is to be transmitted,

in due time, ther-tube destined for the supply'of `the impulse must experience with respect to the `other tubes a decreased supply of the operating f medium or an increased supply of heat. Dependingiupon the extent, `to which the decrease or p increase of thefsupply of beth mentioned oper- `ating vmedia isbrought about, the superheating Vin the tube supplyingthe impulse, measured ,ac- :cording to the length of the tube, will commence correspondinglyearlier than in the other tubes.

face part which normally forms the evaporating In practice, this `may be acthe supply of operating medium tothe measuring In 'this' in the path of flow at a suitable point, preferably inthe zone in which the operating medium is still liquid, a resistance correspondingly rated.

Dependent upon the magnitude of this resist-V ance, theppoint at which the superheating begins, ,willydisplace itself in the measuring tube more i or :less oppositeto the` direction of flow of the! Y to operating medium with respect to the other tubes.

It has hitherto been customary in steam generators with forced passage of the operating medium to arrange at least one part of the heating surface, in which under normal operation the conversion of liquid into steam is effected, as contact heating surface in the path of the fuel in order to prevent a burning out of the tubes due principally in this phase of production of steam to salts depositing from the operating medium. Since, with a measuring tube having means providing for its superheating Zone being displaced forwardly relatively to the superheating zone of the othertubes, the other phases or zones of steam production of the measuring tube are also displaced to more or less extent in the direction opposite to flow of working fluid, with vthe result that the salt deposit zone of the measuring tube may not remain Within the contact or convection heating region of the generator Ybut be shifted into the radiant heat zones; and, in consequence, it may happen that the measuring tube, because of the wandering of the phases of steam production and creeping of the salt deposit zone into the radiant heat zone, -or zone of high heat intensity, may have salt deposited in portions of the surface thereof subject to such high temperatures and give rise to burning out of the measuring tube, this objection having already been lavoided by the intentional displacement of the saltdeposit zone of the remaining tubes into the contact or convection heating surface where such a relatively low temperature normally obtains as to avoid burning out of tubes, even though depositsrof salt should occur.

The other solution, as above generally stated, of the probleml upon which the invention is based prescribes that at least' one of the parallel connected tubes should experience an increased sup- Vply of operating medium or decreased supply of heat with respect to the other tubes and Vthat the temperature impulse should be derived from this particular tube at the point, at which the preheating ends.

It may be further stated that the invention has a particular importance for such steam generators which are fed with an excess of operating medium, and in which the steam before the beginning of its superheating hows into a drum, in which the excess of water is separated from the steam produced up to that moment and is carried off from the generator. For such steam generators it was hitherto not possible rto derive for the boiler a temperature impulse suitable for regulating purposes before the separating drum.Y If the invention is to be 'applied for these steam generators two methods are possible according to the invention. In accordance with one method, the preheating zone is displaced, as above described, toward the boiler outlet, that is, in this case, toward the separating drum, and the temperature impulse is taken at a point along the measuring tube within 'the nal region of the preheating Zone of the measuring'tube which overlaps the initial portion ofthe evaporation Zone of the remaining tubes. In the other method, the measuring tubeis soV arranged and Vsteamproducing media are so supplied thereto that the initial portion of the superheating zone thereof overlaps a portion of the evaporation Zone ofthe remaining tubes; and, as before, the initial overlapping portion of the superheating zone of the measuring tube is used to give 'la temperature impulse for controlling purposes. The temperature impulse necessary for the regulation of the generator may be then derived from this heating surface point, at which the superheating begins. It suffices if the supply of the operating medium or the supply of heat for this measuring tube is so regulated that the steam flowing from this vtube into the salt separating drum is only slightly superheated.

Thus, it will be seen that, in all applications of the invention, a plurality of parallel tubes are arran'ged'to have at least one thereof serve as a measuring tube in order to provide a controlling temperature impulse so that lag may be minimized. Any suitable means may be employed to secure offsetting of the zones of steam production of the measuring tube with respect to such zones of the Vremaining tubes, the essential feature being to provide for the temperature impulse being taken at a point of variable temperature along the measuring tube and falling Within the physical limits of the evaporation zone of the remaining tubes.

In the drawings, Figs. 1 to 5, inclusive, are diagrammatic views` illustrating the essential feature orcharacteristic of the present invention;

Fig. 6 is 'a diagrammatic view showing the application of the principle of Figs. l, 3, and

Fig. '7 is a diagrammatic view showing the application of the principle of Figs. 2 and 4.

Y Figs. 8 and 9 are diagrammatical sectional views of ilow control or throttling devices for the tubes.

The present invention is illustrated in diagrammatic form in Figs. 1 to 5. VThe tubes forming the heating surfaces are diagrammatically represented in the form of heavy lines. The ends of the tubes enter collecting or distributing vessels. The direction of flow of the operating medium is indicated by the arrows as shown. Flow control or throttle points in the tubes are indicated by cross lines intersecting the tubes, whereas the temperature points are indicated by small Ycircles drawn on the tube lines. Insofar as the flowfcontrol or throttle points are cut oft" or the temperature measuring points are not used for the regulation the corresponding symbols are shown in all figures in dashes. In all figures the lowest of the three tubes serves for the reception of the impulse which as above described may alternately be derived from the one or the `other of the tubes shown by the use of change-over 'devices not shown. The diagrammatical representation which shows only three tubes is to be considered only as an example; the number of the tubes may vary at will.

Figs. l and 3 show the conditions for the case, in which the impulse is transmitted in response `to the temperature of the superheated steam, the time at which the superheating begins being displaced towards the operating medium inlet point. In these views, short lines intersecting vthe tubes indicate flow control or throttling devices, the heavy short lines, at t, indicating a throttling or resistance setting of the devices and the light lines, at o, an open or non-throttling setting thereof.

Figs'. 2 and 4 show the derivation of the impulse from a point lying at the end 'or near the As beforefthe resistance or throitling'set 75 ting of the flow control devices is indicated in each instance by a heavy cross-line and by the reference character t and the non-throttling settings thereof are indicated by the light crosslines and the reference character o.

In Figs. 6 and 7, there are shown diagrammatic arrangements employing the principle of control already described; and, in each of these views there are shown parallel connected tubes I0 and II supplied with feedwater by a pump I2 and with heat by means of any suitable combustion apparatus connected generally at I3. Superheated steam is supplied from the tubes to the prime mover I5.

The tubes I0 are so arranged and steam-producing media are so supplied, thereto that the heating surface is divided into a preheating zone A, an evaporating zone B, and a superheating zone C; however, the measuring tube II is arranged, by any suitable means, to have its corresponding Zones offset so as to provide regions of the heating surface thereof, preheatingor superheating, overlapping or falling within the physi- `cal limits of the evaporation zone B, whereby such overlapping portion of the measuring tube provides a region of variable temperature within the limits of the evaporation Zone B and which may be used to give a temperature controlling impulse. l

In Fig. 6, by restricting the flow, for example, in the measuring tube II relatively to the flow in each of the remaining tubes II), it will be seen that the superheating zone C extends further back so that the initial portion b-cV falls within the physical limits of the main evaporation Zone B of the tubes III, and this initial or overlapping portion of the measuring tube is, therefore, subject to rise and fall of temperature dependent on operating conditions and may be usedto provide a temperature impulse for the controlling apparatus.

Any suitable means may be used to secure differential throttling of flow in the measuring tube with respect to the remaining tubes. Accordingly, in Fig. 6, the heavy cross-line I Ii at the left hand end of the measuring `tube indicates a greater resistance to fiow therein than through the remaining tubes I0, the resistance of the latter being indicated by the relatively light crosslines I1. In this view, a temperature responsive device I8 is shown associated with the overlapping portion b--c of the measuring tube and provides an impulse for the control system, as will be immediately pointed out.

Fig. '7 shows a diagrammatic arrangement which is similar to Fig. 6 except that the resistances are reversed, greater flow occurring through the measuring tube I I than through the .remaining tubes II), with the result that the preheating, evaporation, and superheating zones A2, B2, and C2 are displaced toward the outlet, whereby there is provided a final portion a--b of the preheating Zone A2 which overlaps the initial in the measuring tube with respect to the remaining tubes, any suitable flow control or throttling devices being associated with the tubes for this purpose. In Figs. 1 to '7, inclusive, the throttling or resistance setting of these devices is indicated in each instance by a heavy cross-line and the reference character t and the non-throttling setting is indicated by a light cross-line o. Figs. 8 andV 9 show, by wayy of example, iiow control or throttling devices capable of being placed in the throttling position, t, or in the non-throttling or open position o. In these views, the resistance or throttling condition, t, is secured by adjusting the valve 22 so that ow occurs through the upper branch of the passage having the orifice 23 While the open or non-throttling condition is secured by adjustment of the valve so that ow occurs through the lower branch of the passage.

As hereinbefore described, the load effect of the prime mover may be used to supply a controlling impulse to either or both of the steam-producing media, feedwater and heat, supplied to the boiler. In Figs. 6 and 7, `this impulse is indicated diagrammatically as originating with the prime mover governor and going to motors I9 and 20, whichdetermine or control the operation of the feed pump and of the fuel and air supply. In addition, the temperature impulse coming from the device I8 in Fig. 6 is shown as being superimposed upon the main impulse in order to exercise a corrective effect, whereby a desired outgoing superheated steam temperature may be maintained. Inv Fig. 7, instead of the governor impulse being used to control both the feedwaterA and the heat supply means, this impulse is exerted only on the feed water supply means, the temperature responsive device I8 operating to control the fuel and air supply means. Accordingly, therefore, so far as the present invention is concerned, it is only essential that the control system shall use a temperature impulse and it is immaterial specically how this impulse is utilized.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of Vvarious 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 specically set forth in the appended claims. f

What I claim is:

1. In a steam generator, a plurality of parallelconnected tubes, means for supplying feedwater as working medium and heat to the tubes so that the Working medium is preheated, vaporized and superheated in successive Zones; means providing for offsetting of said zones in one tube with respect to the zones of the remaining tubes, so that said first tube constitutes a measuring tube, whereby the measuring tube has a region of variable temperature which partially overlaps the evaporation Zone of said remaining tubes; and

means for deriving a temperature impulse fromv said overlapping region of the measuring tube and for utilizing the impulse to control said supply means.

2. The combination as claimed in claim 1 wherein the means providing for oifsetting of the zones in the tubes are adjusted so that the initial portion of the superheating Zone of the measuring tube is overlapped by the nal portion of the evaporation Zone of the remaining tubes and evaporation zone of the remaining tubes and wherein the means for deriving the temperature impulse from the measuring tube is associated with said lnal overlapped preheating portion thereof.

Y Y MARTIN EULE.

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