US2222348A - Apparatus for desuperheating vapor - Google Patents

Description

Nov. 19, 1940. l H. H, GQRR'IE 2,222,348

APPARATUS FOR DESUPERHEATING ,VAPOR Filed July l5, 1936 Patented Nov. 19, 1940 UNITED STATES APPARATUS FOR DESUPERHEATING VAPOR Harvard H. Gorrie, Cleveland Heights, Ohio, as-

signor to Bailey Meter Company, a corporation of Delaware Application July 15., 1936, Serial No. 90,695

9 Claims.

This invention relates to apparatus for partially or completely desuperheating vapor.

It is well known to desuperheat a flowing stream of vapor, such as steam for example, by

providing a spray ring or nozzle having a plurality of fine openings through which water flows in an atomized or broken up condition into the steam. Such a system is satisfactory when the pressure drop across the fine openings corre- 10 sponds to that for which they were designed.

However, if used on a variable steam flow, necessitating throttling ofthe water supply in order to maintain a constant temperature of the desuperheated steam, the arrangement is not satis- R5 factory as the water then is not atomized or broken up but leaves the openings in a solid stream so that intimate mixing with the steam is not obtained. It has been found in commercial practice that a desuperheater designed to properly desuperheat a given maximum steam flow will not operate satisfactorily if the steam" flow is reduced below 50% of the said maximum.

It is therefore one object of my invention to provide apparatus for desuperheating vapor whereby a nely atomized spray is obtained over a wide range in output.

Further, in accordance with my invention changes in the temperature of. the desuperheated vapor are anticipated and the output of the desuperheater modied accordingly before such changes in temperature actually occur.

My invention further provides for con-trolling the output of a desuperheater conjointly from the temperature of the desuperheated Vapor and `the rate of flow thereof.

My invention further provides for varying the output of a desuperheater, both proportionately to changes in the temperature of the desuperheated vapor and to the amount of deviation of the temperature from a predetermined or desired magnitude.

It should be understood that the term desuperheated vapor or desuperheated steam as used in this specification applies to vapor 'or steam which may be only partially desuperheated and not necessarily to zero degrees of superheat.

In the drawing:

Fig. 1 illustrates diagrammatically an embodiment of my invention.

Fig. 2 is an elevation view to larger scale of the spray nozzle shown in Fig. 1.

Fig. 3 is a cross sectional View of the spray nozzle along the lines 3-3 of Fig. 2 in the direction of the arrows.

u In accordance with the present invention there is provided a conduit I to which superheated vapor is admitted so that it flows through the conduit in the direction indicated by the arrow.

Extending into the conduit is a water jet or spray nozzle 3 pointing upstream with respect to 5 its discharge end II, although the direction of discharge may be reversed if desired. Water is supplied the nozzle 3 under a pressure greater than that of the vapor to be desuperheated,

through a pipe 5 leading from any suitable m source, such as the discharge conduit 6 of a centrifugal pump I to which Water is admitted through an inlet 8. It will be understood that the arrangement I have shown for providing desuperheating fluid to the nozzle 3 is merely illus- 15 trative and that any suitable source may be used.

The nozzle 3 as shown in Figs. 2 and 3 comprises a circular chamber ,9 provided with an axially located aperture or orice I0 through which the desuperheating fluid, such as water, 20 is discharged into the stream of vapor to be desuperheated. Water is admitted to the chamber 9 from the pipe 5 through an inlet connection II and port I2 tangentially with respect to the circular wall of the chamber 5. Water enter- 25 ing the chamber 9 and not discharged through the orifice ID is Withdrawn through an axially located secondary outlet connection I3 leading to a source of relatively low pressure, which may be for example the inlet 8 of the pump l. 30

The port I2 is arranged so that water passes therethrough at high Velocity and sets up in I.the chamber 9 a rapid rotary motion which causes the water to be discharged through the orice I0 in the form of a spray or nely atom- 35 ized condition. The rate of discharge through the orifice I 0 may be varied by throttling the flow through the secondary connection I3. With the secondary connection closed, all the water admitted through the port I2 is discharged through the orice I0. With the secondary connection partially restricted some of the water will be discharged therethrough, decreasing the discharge through the orice I0 proportionately. Variations in the rate of discharge through the sec- 45 ondary connection I3 does not, howeverylaiect the velocity through the tangential port I2 or the rapidity of the rotary motion set up in the chamber 9. Inasmuch as the quality of the spray produced by the orice I0 depends substantially 50 entirely upon the rate of rotation of the mass of Water within the chamber 9 it follows that Variations in the discharge through the secondary outlet I3 and'corresponding variations in the discharge to the orice I0 will in no way affect the 55 chamber 9, which remains substantially constant a decrease in fluid pressure the diaphragm motor 'temperature of the desuperheated steam may u superheated steam temperature from the prede- .;f.. i free end of the Bourdonl tube I'I in an upward quality of the spray established. In other words, the neness or quality of the spray is determined by the vrotary motion of the water within the Pivotally connected to the free end of the of a pilot valve 20 preferably of the type forming the subject matter of a United States patent `to Clarence Johnson, Patent No. 2,054,464, dated September 15,1936. Suitable iiuid under pressure, such as compressed air, is admitted to the pilot through an inlet port 2| and is conducted at al1 times, whereas the rate of discharge into the conduit lI is determined by the pressure drop across the orifice I0, which in turn is controlled by the throttling of Ethe secondary outlet I3. I have found-that the water will leave the nozzle to waste ports at either end of the pilot valve 'eiciently atomized, from a maximum flow obthrough an axially located cylindrical passagetained with the secondary outlet I3 closed down Way extending longitudinally -through the pilot to' approximately 10% or less of that maximum. valve. Vertical positioning of the valve mem- It is apparent from the foregoing that the ber I9, which carries suitable lands, modifies the magnitude of the fluid pressure effective at be held at some predetermined desired value regardless of changes in the rate of flow thereof by varying the iiow through the secondary outlet in accordance with deviations in the temperavalve member there is a pressure of denite magnitude, Which for convenience term aloading pressure, established at the outlet port. With ture from the predetermined or desired value. y the valve member I9 at the lowest position within its range of movement a loading pressure of minimum magnitude is established at the outlet It is further apparent that the throttling of the flow through -the secondary outlet vwill have n o` effect upon the eilcient atomizing of the water spray, so that the steam will be uniformly desuperheated to the predetermined or desired temperature.

In Fig. 1 I show a valve I4 connected in the secondary outlet I3 for throttling the ow therethrough. The valve I4 is arranged to be Variations in loading pressure established at actuated by a pressure sensitive diaphragm the outlet port 22 are effective for actuating the motor I5. As shown, upon an increase in uid diaphragm motor I5 to cause prOPOrtiOrlate pressure of given amount the diaphragm motor mOVementS 0f the valve |4 Accordingly, upon acts to position the valve I4 in a closing direc# an increase in the temperature of the desupertion a proportionate amount. Conversely, upon heated steam the valve member I9, through the agencyfof the Bourdon tube I'I, will be positioned upwardly a proportionate amount eiecting a like Iposition within its operating range a loading pressure of maximum magnitude is established.

sure will vary proportionately ywith the axial positioning of the valve member.

acts to position the valve a proportionate amount in an opening direction. change in thev loading pressure at the outlet In one particular aspect my invention conport 22. This Change in loading pressure transtemplates4 establishing a fluid pressure varying mitted t0 the diaphragm motor l5 through deboth in accordance with changes in temperature vices later to be described actuate the motor to of the desuperheated steam and the amount of position the valve Iii in a closing direction an deviation of the actual temperature from the amount proportional to the increase in desuperdesired or predetermined temperature, and heated Steam temperatura A greater proporutilizing the fluid pressure to position the tion of the water transmitted to the nozzle 3 will diaphragm motor I5. Accordingly, upon a, then be discharged through the orifice I0 tending change in temperature d the desuperheated to restore the temperature of the desuperheated steam, regardless of whether the change is to- Steam i0 the desired Value. If 110W the tem ward or away from the predetermined value, an perature of the desuperheated steam should deimmedlate and proportionate change is made Grease, the loading pressure transmitted t0 the in the flow through the secondary outlet lain diaphragm motor i5 will decrease proportiona sense to produce a temperature change of aiely, eie'ting a movement 0f the Valve I4 in the desuperheated steam in opposite direction. an Opening direCtiOn, thus decreasing the diS- Continuously, however, the ow through the Charge 0f Water irltO the COIlduit It iS apsecondary outlet I3 is modified at a rate propor- Parent that the aDDaratuS S far described Will tiona1 to the amount of deviation of the deact to maintain a denite rate of discharge of water for every temperature of the desupertermined value so that the temperature is main- .heated Steamtained substantially at the predetermined value T0 P/llovide an .ample Supply of pressure uid without overshooting or hmm gr/rgafggfnfor operating the diaphragm motor I5 and changes in thefr-,ofiy/fsteam t be`de further to provide means for producing a consuperheated or changes 1n the degree of supertinuous change in the rate of ilow through the heat thereof. secondary outlet I3 at a rate proportional to the I will now describe the apparatus provided for amount of deviation of the actual value of the producing the uid pressure for actumm'lgv the desuperheated steam temperature from the predlaphragm motor l5, The temperature of the determined value I preferably interpose between desuperheated steam is measured by a therthe outlet port 22 and the diaphragm motor I5 a mometric system comprising a bulb IB extending standardizing relay 23 0f the type flming the into the conduit l beyond the nozzle 3 and consubject matter of my copending application, neoted t0 a Bourdon tube I1 by a capillary I8. Serial No. 8047, filedin the United States Patent An increase in temperature of the desuperheated Olce February 25, 1935. steam eiects a proportionate movement of the Within the relay 23, hich is shown in cross section, is a chamber 24 separated by a pressure sensitive diaphragm 25 from a chamber 26 open to the atmosphere through a port 21. Below a pressurel tight partition 28 is a further pair of direction. Conversely, a decrease in A superheated steam temperature effects a proportionate positioning of the Bourdon tube in a downward direction.

Bourdon tube I1 is the movable valve member I9 an outlet port 22 so that for every position of the port. With the valve member at the highest Between these two extremes the loading pressitive diaphragm 3|, and connected with each other through a passageway 32 in which is located an adjustable throttling valve 33 for controlling the rate at which pressure iiuid will 5 bleed from one chamber to the other. Secured to the diaphragms 25 and 3| is a movable member 32 engaging at its lower end a fulcrumed normally horizontal member 33A carrying depending extensions for operating a normally closed pressure iiuid admission valve 34 when displaced from the horizontal in one direction, and a normally closed pressure fluid exhaust valve 35 when displaced in the opposite direction. The pressure fluid, such as compressed air, admitted through the valve 34 may be derived from any suitable source (not shown) .Secured to the upper end of the movable member 32 is a manually adjustable tension spring 36 for urging the lmember 32 upwardly.

The outlet port 22 of the pilot 20 is connected to the chamber 24 through a pipe 31 so that loading pressures established by the pilot valve are immediately effective therein and produce a proportionate downwardly acting force on the di- 25 aphragm 25.

Now assuming for the moment that the throttling valve 33 is closed, the force acting against the diaphragm 25 will position the member 32 downwardly opening the admission valve 34 and permitting the pressure fluid to enter chamber 30. As the pressure within the chamber 3U increases the force acting upwardly against the diaphragm 3| will increase, and when it is equal to or stands in predetermined relation to the 35 force acting on the diaphragm 25 the member 32 will move upwardly closing the admission valve 34. Conversellhupon a decrease in pressure Within the chamber 24 the member 32 will move upwardly opening the exhaust valve 35, permitting pressure fluid to escape from the chamber 3D until the force acting upwardly on the diaphragm 3| is again equal to that acting downwardly on the diaphragm 25. Thus for every pressure within the chamber 24 there will be a corresponding pressure Within the chamber 30. While a change ,in pressure of given amount Within the chamber 24 will result in an equal change in pressure within chamber 30, the absolute value of the pressure within the chamber 30 may be diierentfrom that within chamber 24 and is controlled by the adjustment of the spring 36.

If now the throttling valve 33 is partially opened so that pressure fluid may pass at a relatively slow rate between chambers 29 and 3U, up-

on a change in pressure within the chamber 24 a proportionate change will immediately occur in chamber 30. Thereafter, however, in place of the valves 34 and 35 remaining closed and the pressure within chamber 30 constant, pressure uid will pass between the chambers destroying the equilibrium forces acting upon the diaphragms 25 and 3| and occasioning a further change in pressure within the chamber 30. Such further change will cause a further passing of uid between the chambers 29 and 3| and result in a still further change in pressure within the chamber 30. While I have described the operation and steps, it is apparent that the change in pressures within the chambers 29 and 30 will be gradual and continuous.

In operation the spring 36 is initially adjusted so that with the loading pressure existing within the chamber 24 corresponding to that produced when the temperature of the desuperheatedl steam is at the predetermined value, and the throttling valve 33 open so that equal pressures will exist in chambers 29 and 30, the valves 34 and 35 are closed. The throttling valve is then moved to a partially closed position, the exact position being determined by the constants of the system, such as speed of response, lag, etc. Thereafter upon a change in loading pressure Within the chamber 24 an immediate and proportionate change will occur in chamber 30, which will be followed by a continuing secondary change due to the regenerative action between chambers 29 and 30 as hereinbefore described. It is apparent that therate of the secondary change will be proportional to the diierence in pressure between chambers 29 and 30, which will in turn be proportional to the deviations in temperature from the desired value. It is further' apparent that only when the temperature is at the predetermined value will the pressure within the chamber 30 remain constant. When at any other value the pressure therein will continually change, and in sense dependent upon the direction of deviation of the temperature from the predetermined value.

The pressure within the chamber 30 is transmitted through a pipe 38 to a chamber 39 of an averaging relay 40 somewhat similar to the standardizing relay 23. Changes in `pressure within the'chamber 39 produce proportionate changes in pressure within the chamber 4| connected to the diaphragm motor |5 by a pipe 42.

In operation, assuming the desuperheated steam temperature to be at the predetermined value, upon a change in temperature of given amount, for example an increase, a proportionate change in loading pressure within the chamber 24 will occur which will produce an immediate and proportionate change in the pressure within the chamber 30, which will be transmitted through the relay 40 to the diaphragm motor I5. The diaphragm motor will operate the valve I4 in a closing direction to decrease the flow through the secondary outlet, thus increasing .the valve |4, -or in other words in a direction tending to prevent such return. However, the secondary continuing response will still act to close the Valve so `that the return of the temperature to the predetermined value will be asymptotically and overshooting or hunting will be avoided.

Upon a decrease in temperature below the desired value the converse action will occur, the valve I4 rst being positioned in an opening direction an` amount proportional to the decrease in temperature, and thereafter continuously -positioned in an opening direction at a rate proportional to the amount the temperature is below the predetermined value. It is apparent that in general the control responds upon a change in temperature to give an immediate and proportionate correction in a direction to prevent the change, and to give a continuing correction in a direction to restore the temperature to the desired value. The rst or immediate response is nary operating conditions give satisfactory results. It is to be noted, however, that it is necessary for a deviation 'in temperature of the desuperheated steam to occur before a correction is made to restore the temperature to the predetermined value. Under widely varying rates of steam flow resulting vin sudden and extreme changes in desuperheated steam temperature the allowable limits of temperature deviation from the predetermined value may be exceeded. To prevent such an occurrence my invention further contemplates anticipating changes in temperature andcorrecting the rate of discharge of water into the superheated steam before such changes actually occur. In general, the control acts to vary the discharge through the orice I0 in proportion to changes insteam flow. If due to valve or nozzle characteristics or other causes the change in Water discharge so made is not exactly correct to maintain the desuperheated steam temperature at the predetermined value then the control sensitive to the temperature of the desuperheated steam will continually modify the water discharge until the predetermined temperature is restored.

To position the valve I4 to vary the rate of discharge through the orifice I0 in accordance with changes in steam ow I introduce into a chamber 43 of the averaging relay 40a loading pressure proportional to the rate of' steam flow.

-Thus upon an increase in steam flow, for example, the loading pressure within the chamber 43 is increased proportionately, causing a like'increase in pressure within the chamber 4|, which is transmitted to the diaphragm motor l5 and serves to position the valve I4 in a closing direction, thereby increasing the discharge' of water into the conduit l. Upon a decrease in the rate of steam flow the reverse action takes place, the loading pressure within the chamber 43 decreasing proportionately, causing a like movement of the valve i4 in an opening direction, thereby decreasing the rateof discharge of water through the orifice l 0.

If correct correspondence has been maintained during and after `such changes, between water discharge and rate of steam ow, and there has been no change in superheated-steam tempera'- ture, then the desuperheated steam temperature will remain at the predetermined value. If, however, such correspondence is not exactly maintained, then a relatively small change in desuperheated steam temperature will occur, which will readily be corrected by the control sensitive to desuperheated steam temperature 'as hereinbefore described. g

The loading pressure ,established Within the chamber 43 and varying in accordance with' changes in steam ow is produced by a pilot valve 44 havingv a valve member 45 vertically positioned by an indicator arm 46 of a rate of iiow meter 4].

The flow meter 41 may be of the type shown and described in United States Patent 1,123,164 to Bailey, and comprises essentially 'a bell 48 sealed ina liquid such as mercury indicated at 49 and vertically positioned therein in accordance with the differential pressure produced by a restriction such as an orice 50 in the conduit l. As known, the differential pressure produced by a device such as the orifice bears a quadratic relation to the rate of ow. In order that the indicator arm 46 will be positioned directly proportional to changes in ow rather than differential pressure the bell 48 may be provided as shown with a wall of varying thickness, so that it will be positioned proportional to the square root of the differential pressure rather than in direct proportion.

The pilot valve 44 is similar to the pilot 20, in-

asmuch however as the loading pressure pro-` duced thereby should progressively increase as the valve member 45 moves downwardly, con-A nection from the chamber 43 is made to an outlet port' 5| located below the inlet port 52. Thus What I claim as new, and desire to secure by Letters Patent of the United States is:

1. A desuperheater comprising a chamber, an orifice of constant area located in said chamber for discharging desuperheating iiuid directly into a :lowing stream of vapor to be desuperheated,.a

discharge connection tov said chamber for withdrawing desuperheating uid therefrom, and means for controlling the rate of ow of uid through said discharge connection conjoitly responsive to the rate of ow of the vapor to be desuperheated and the temperature of the desuperheated vapor.

2. A desuperheater comprising a chamber, an orice located in said chamber for discharging desuperheatng fluid into a owing stream of vapor to be desuperheated, a discharge connection to said chamber for withdrawing desuperheating fluid therefrom, regulating :means of the rate of flow through said discha-rge connection, and control means for said regulating means'comprising means for establishing a first uid pressure in accordance with the temperature of the desuperheated vapor, means responsive to changes in said rst fluid pressure for establishing immediate proportional changes in a second. fluid pressure and continuing changes therein upon departure of the first fluid pressure from a predetermined value,

-and means actuated by said'second fluid pressure for controlling said regulating means.

3. A desuperheater comprising a chamber, an orice in a .wall of said chamber for discharging desuperheating uid into a flowing stream of the vapor to be desuperheated, a discharge connection to said chamber for withdrawing desuperheating fluid therefrom, means responsive to the temperature of the desuperheated vapor, and means actuated by said last named means for producing immediate changes in the rate of flow of fluid through said ldischarge connection in proportion to changes in the `temperature of the desuperheated vapor and continuous changes proportional to the deviation of the temperature of the desuperheated vapor from a predetermined value.

4. A desuperheater comprising a chamber, an orifice in a wall of said chamber for discharging desuperheating fluid into a flowing stream of vapor to be desuperheated, a discharge connection to said chamber for withdrawing desuperheating fluid therefrom, means for producing a first fluid pressure in accordance with the temperature of the desuperheated vapor, means for establishing a second fluid pressure in accordance with the rate of flow of the vapor to be desuperheated, means for establishing a third uid pressure in accordance with the algebraic sum of the first and second fluid pressures, and regulating means of the rate of flow of fluid through said discharge connection under the control of said third fluid pressure.

5. A control system for a de-superheater comprising in combination, means for establishing a first fluid pressure in accordance with the rate of flow of vapor to the desuperheater, means for establishing a second fluid pressure in accordance with the temperature of the de-superheated vapor, means under the control of the first fluid pressure to regulate the rate of `flow of the desuperheating fluid in direct ratio to the rate of flow of the vapor to be de-superheated, and means under the control of the second fluid pressure for varying the ratio between the rate of flow of vapor and desuperheating fluid.

6. In a control system for a desuperheater in combination, regulating means of the rate of flow of desuperheating fluid, control means for said regulating means comprising means for establishing a first fluid pressurev in accordance with the temperature of the desuperheated vapor, means responsive to changes in said first iluid pressure for establishing immediate proportional changes in a second fluid pressure and continuing changes therein upon departure of the first fluid pressure from a predetermined value, and means actuated by said second iluid pressure for controlling said regulating means.

'7. In a control system for a desuperheater, wherein a desuperheating fluid is used to desuperheat a flowing uid to be desuperheated, in

pressure corresponding to the temperature of the desuperheated vapor, means for establishing a second fluid pressure corresponding to the rate of flow of `vapor to be desuperheated, means for establishing a third fluid pressure corresponding to the algebraic sum of the first and second fluid pressures, and regulating means of the desuperheating-fluid actuated by the third fluid pressure.

8. lIn a, control system for a desuperheater wherein a desuperheating fluid is used to desuperheat a flowing fluid to be desuperheated, in combination, means for establishing a first fluid pressure corresponding to the temperature ofthe desuperheated vapor, means for establishing a second fluid pressure corresponding to the rate of flow of desuperheating fluid, means under the control of the first fluid pressure for-producing changes in the second fluid pressure proportional to changes in the rst fluid pressure, and regulating means of the desuperheating fluid actuated by the second fluid pressure.

9. In a control system for a desuperheater wherein a desuperheating fluid is used to desuperheat a flowing fluid to bedesuperheated, in combination, regulating meansl of the rate of flow of the desuperheating fluid comprising means for establishing immediate and proportional changes in a fluid pressure in accordance with changes in the temperature of the desuperheated vaporl and continuing changes in the fluid pressure in accordance with the departure of the temperature of the desuperheated vapor from a predetermined Value, and regulating means of the desuperheating fluid under the control of said fluid pressure.

HARVARD H. GORRIE.

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