US3154057A

US3154057A - Regulating system for dividing a stream of fluid into at least two subsidiary streams

Info

Publication number: US3154057A
Application number: US293579A
Authority: US
Inventors: Brunner Alfred
Original assignee: Sulzer AG
Current assignee: Sulzer AG
Priority date: 1963-07-03
Filing date: 1963-07-03
Publication date: 1964-10-27
Anticipated expiration: 1981-10-27

Description

Oct. 27, 1964 'A. BRUNNER 3,154,057

REGULATING SYSTEM FOR DIVIDING A STREAM OF FLUID INTO AT LEAST TWO SUBSIDIARY STREAMS 5 Sheets-Sheet 1 Filed July 3, 1963 Oct. 27, 1964 A. BRUNNER 3,154,057

REGULATING SYSTEM FOR DIVIDING A STREAM OF FLUID INTO AT LEAST Two SUBSIDIARY STREAMS Filed July 3, 1965 5 Sheets-Sheet 2 Fig. 2

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Oct. 27, 1964 A. BRUNNER 3,154,057

REGULATING SYSTEM FOR DIVIDING A STREAM OF FLUID INTO AT LEAST TWO SUBSIDIARY STREAMS 5 Sheets-Sheet 3 Filed July 3, 1963 fm emon' flz. FEED BE uzwvEE.

A. BRUNNER 3, 54,057 M FOR DIVIDING A STREAM OF FLUID Oct. 27, 1964 REGULATING SYSTE INTO AT LEAST TWO SUBSIDIARY STREAMS 5 Sheets-Sheet 4 Filed July 3, 1963 5 MSN [fire/7601': 4L Peso Beam NEE! B x4 Afton/ray.

Oct. 27, 1964 A. BRUNNER 7 REGULATING SYSTEM FOR DIVIDING A STREAM OF FLUID INTO AT LEAST TWO SUBSIDIARY STREAMS Filed July 3, 1963 5 Sheets-Sheet 5 tin v fi m 1 t m $3 g w llv w 2 w l D. A as mi I L i 1 J .NMT w ww aw mm? mm .3 QM I Fm: IL \Q :U 5 F 11 J: 9% W b K um x INVENTOR. flLfRm BRll/VA/[R BY 4% flrromvey- United States Patent 3,154,057 REGULATING SYSTEM FOR DIVIDING A STREAM 0F FLUID INTO AT LEAST TWO SUBSIDIARY STREAMS Alfred Brunner, Winterthur, Switzerland, assignor to Sulzer Fret-es, S.A., Winterthur, Switzerland, a corporation of Switzerland Filed July 3, 1963, Ser. No. 293,579 4 Claims. (Cl. 122-406) This invention relates to a regulating system for dividing a stream of fluid into at least two partial or subsidiary streams by means of throttling devices which control the flow in the partial streams.

It is an object of the invention to provide a system for splitting a stream of a fluid into at least two partial streams by controlling the rate of flow of each stream by means of valves or other rate of flow controlling means whereby at least one of the valves is always fully open in order to keep throttling losses as low as possible.

The division, i.e. the control of the means regulating the flow rate of the individual streams, may be effected in response to conditions prevailing in the particular application of the invention.

According to the invention a regulator is provided for each flow control means and a signal is fed to each regulator corresponding to a variable which must be controlled and which is dependent on the flow of the respective partial stream. At any time, the flow control means of at least one of the controlled partial streams is held fully open by the respective regulator so that it does not cause any appreciable resistance to the flow of the respective stream. The set point of each regulator is adjusted according to a desired portion of the sum of all signals corresponding to the controlled variables of the streams and according to the signal controlling the fully open flow rate control means.

The invention can be applied, for example, if a stream of a medium is to be distributed among a plurality of heat exchangers in such manner that the partial streams leaving the heat exchangers have equal temperatures or have certain temperature differences in relation to one another. The distributed medium may be the medium that is heated in the heat exchangers or the medium from which heat is transferred to another medium. The last mentioned arrangements are useful in combination with nuclear reactors.

The regulating system according to the invention can also be used in combination with steam generators including, for example, a plurality of parallel-connected superheating sections whose end temperature is regulated by water injection. In this case it may be desirable, for example, to so modify the regulating system that the amount of steam supplied to each superheating section is so adjusted that the amounts of water injected into the diiferent sections are equal.

When speaking of a fully open" throttling element in this specification the flow area of the throttling element or valve may be somewhat smaller than the maximum flow area, i.e., the valve spindle may not be quite at the end of its travel so that it can move at least slightly in either direction. This is desirable because, if a disturbance occurs in the plant, the regulating oscillations of the system subside more rapidly than would be the case if the valve spindle were at the end of its travel and abutting against an abutment limiting the valve opening stroke of the spindle.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be 3,154,057 Patented Oct. 27, 1964 understood from the following description of embodiments thereof when read in connection with the accompanying drawing wherein:

FIG. 1 is a diagrammatic illustration of a regulating system according to the invention whereby a stream of a medium is divided into three subsidiary streams, each of which is heated, and whereby the division of the stream is such that predetermined temperatures of the partial streams are maintained.

FIG. 2 illustrates a modification of a detail of the system shown in FIG. 1.

FIG. 3 illustrates another modification of a detail of a regulating system illustrated in FIG. 1.

FIG. 4 is a diagrammatic illustration of a control sys tem according to the invention as applied to a steam superheating plant wherein the final superheat temperature is controlled by coolant injection.

FIG. 5 is a diagrammatic illustration of a modification of the system shown in FIG. 3.

FIG. -1 shows a regulating system employing electrical components and wherein the mean value of the temperatures of the fluid forming the subsidiary streams is used for adjusting the set points of the valve regulators. A conduit 131 supplying the medium to be distributed branches into three

subsidiary conduits

132, 132 and 132" containing

valves

133, 133' and 133", respectively. Part of each subsidiary conduit forms a

heat exchanger

134, 134 and 134", respectively, wherein the subsidiary conduits are divided into groups of parallel-connected tubes situated in a suitable zone of a furnace or flue for heating the medium flowing through the tubes as is indicated by

arrows

135, 135' and 135", respectively. Downstream of each

heat exchanger

134, 134' and 134" an

electrical resistance thermometer

136, 136' and 136", respectively, is provided which produces the regulated value signal. Each of the

resistance thermometers

136, 136 and 136" is connected in a Wheatstone bridge circuit including three

resistors

137, 138, 139; 137, 138', 139 and 137", 138", 139", respectively. The

resistors

136 and 137 are connected in series and receive a reference alternating current voltage E, while the primary winding of a transformer 140 is connected at the points a and b between the

resistors

136 and 137 and between 138 and 139, respectively. The secondary windings of the

transformers

140, 140 and 140" are connected in series by a conductor 141 for averaging the signals corresponding to the temperatures at 136, 136 and 136". The voltages between a and b, a and b, and a" and b" are proportional to the temperatures of the medium flowing through the

subsidiary conduits

132, 132' and 132", respectively, and are compared with an opposing set point voltage across the

conductors

141 and 142 at the points 0 and d, c and d, and c" and d", respectively. Any deviation resulting from this comparison is fed as an input voltage to

regulators

143, 143' and 143", respectively. For the sake of simplicity, only the regulator 143 will be described in detail. The

regulators

143 and 143" are like the regulator 143. The regulators are conventional. A conductor 30 connected to point a and a conductor 37 branching off from the conductor 142 are connected in the usual manner to the driver coil of a Ferraris induction motor 41 whose driving pinion 42 rotates at a speed corresponding to the input voltage. The pinion 42 adjusts the position of a movable coil 38 of an inductive sender by way of a rack 43, the stationary coils 39 of the sender being connected to a source of a reference alternating current voltage E. The coil 38 is interposed in a conductor 44 branching off from the conductor 30, the voltage induced in the coil 38 being dependent on the position of the coil and hence on the period of time during which a voltage acts on the driver coil of the motor 41. The voltage of the coil 38 provides the time integral of the input voltage at the driver coil and is superimposed on the input voltage acting on a conductor 36 and connected to 37 and on the conductor 44 and forming the proportional component.

The output voltage of the regulator at the conductors 36 and 44 resulting from this transformation and forming an adjusting signal for the throttling element 133 is fed to an amplifier 144 whose output voltage is fed to the driver coil of a servomotor 145 which is constructed on the same principle as the induction motor 41. The pinion f the servomotor 145 drives a rack 146 which adjusts the flow area of the valve 133. The rack 146 carries a movable coil 152 of an inductive sender whose fixed coils are connected to a source of reference alternating current voltage E.

The output voltage of the regulator 143 is fed by a pair of conductors 143 to the primary winding of a transformer 149 which constitutes part of a selector unit, the secondary Winding of the transformer 149 being con nected by diodes or other rectifiers to a transformer 150. The

conductors

141 and 142 are connected to a set point signal sender 151.

The operation of the regulating system shown in FIG. 1 is such that the rates of flow of medium in the

subsidiary conduits

132, 132' and 132" are always so adjusted that the temperatures of the medium downstream of the

heat exchangers

134, 134' and 134" are equal and one of the

valves

133, 133' and 133" is always fully open. If, for example, the valve 133 is fully open and if the heat supply 135 is intensified so that the temperature of the medium emerging from the heat exchanger 134 rises relative to the temperature of the medium emerging from the heat exchangers 134' and 134", the regulator 143 receives a higher voltage corresponding to the greater deviation between the actual value and the desired value. At the same time, the set point voltage at the points 0', d and c", d is reduced so that the regulators 143' and 143" receive a lower voltage since the voltage at the points a, b and a, b" has not been changed. The higher output voltage of the regulator 143 and the lower output voltage of the regulators 143' and 143" are fed to the

amplifiers

144, 144' and 144", respectively. The output voltages of the amplifiers 144' and 144" influence the

servomotors

145 and 145" in such manner that the flow areas of the valves 133' and 133" are reduced. The output voltage of the amplifier 144 tends to actuate the servomotor 145 to increase the flow area of the valve 133. This, however, cannot be done because this valve is already fully open. The higher output voltage of the regulator 143 now acts through the pair of conductors 148 on the transformer 149 inducing in the secondary winding of the transformer 150 a voltage which opposes the voltage induced in the secondary windings of the

transformers

140, 140 and 140 and which further reduces the voltage between 0, d, c, d, and c, d. This reduced set point voltage results in a lower input voltage of the regulators 143' and 143" and in a lower output voltage of these regulators. The

servomotors

145 and 145" are actuated by way of the amplifiers 144' and 144" to further reduce the flow areas of the valves 133' and 133" whereby the supply of medium to the

heat exchangers

134 and 134" is reduced and the temperatures downstream of these heat exchangers rise. These temperatures continue to rise until they are equal to the temperature downstream of the heat exchanger 134. The valve 133 remains fully open in these circumstances.

Whereas equal temperatures are maintained in the subsidiary conduits with the regulating system shown in FIG. 1, the modification of the regulating system shown in FIG. 2 affords maintenance of predetermined different temperatures in the individual subsidiary conduits. For the sake of simplicity, FIG. 2 shows only the part of the system which differs from that shown in FIG. 1, and only 4 in connection with the subsidiary conduit 132. The control systems for the other subsidiary conduits are like the one illustrated in FIG. 2. The resistance thermometer 136 is connected to three

resistors

137, 138 and 139 to form a bridge circuit. The

resistors

136 and 137 are in series with the reference alternating current voltage E and the point b is connected to one end of the primary Winding of the transformer 140. Stationary coils 155 of an inductive sender 156 are interposed in the conduit between the second end of the primary winding of the transformer 140 and the point a. The movable coil 157 of the sender 156 is connected to a manually operated spindle 158 and is at the reference alternating current voltage E. The voltage which is induced in the coils may be influenced by moving the coil 157 and may be positive or negative according to the position of the coil 157 The voltage at the points a and b, which is dependent on the temperature at the resistance thermometer 136, is increased or reduced by the voltage across the coils 155. A false temperature is thus simulated between the points b and e and is compared with the set point voltage between the points 0 and d of the

conduits

141 and 142 so that the input voltage of the regulator 143 is changed and, in the event of a temperature increase at 136 and of a positive voltage delivered by the sender 156, the associated valve 133, not shown, opens farther than if the true temperature measured by the resistance thermometer 136 were operative. Therefore, the temperature of the medium drops more than it would drop without the influence of the additional voltage produced by the sender 156. With this arrangement it is thus possible, for example, for the medium at 136 to have a temperature lower by 20 C. than the medium at 136 and for the latter to have a temperature lower by 20 C. than the medium at 136". In this case the sender 156' is set to a voltage of zero while the sender 156 is set to a positive supplementary voltage and the sender 156" to a negative supplementary voltage equal to the positive supplementary voltage. In other respects the regulating operation of the system is the same as was explained in connection with the system shown in FIG. 1.

The modification shown in FIG. 3 prevents dropping of the temperature below a predetermined value, in the systems according to FIG. 1 or FIG. 2. For the sake of simplicity, FIG. 3 shows only the

subsidiary conduits

132 and 132 with the associated regulators of the system according to FIG. 1, and, in addition, the arrangement for preventing the undesired temperature drop. In the sysstem according to FIG. 3, the set point signal sender 151 of FIG. 1 is replaced by a set point signal sender 160. A movable coil161 is interposed in the conductor 141 and is connected to a rack 162 of a servomotor 163. A manually operated spindle 164 is provided at the end of the coil 161 remote from the rack. The stationary coils 165 are at the reference alternating current voltage E. At the points 1 and g, which are at voltage corresponding to the sum of the three temperatures measured, a pair of conductors 166 is connected which is also connected to the input of an amplifier 167, the output of the amplifier being connected to the servomotor 163. The amplifier 167 also receives by way of a pair of conductors 168 a Voltage representing the desired value for the minimum temperature. This voltage comes from a set point signal producer, not shown, which is constructed in the same way as the'set point signal producer 151 in FIG. 1.

When the voltage at the pair of conductors 166 is higher than the set point voltage at the pair of conductors 168, the movable coil 161 abuts against the spindle 164 and the regulating system operates in the same way as explained in connection with the regulating system according to FIG. 1. The spindle 164, which is operated only when setting up the plant, is so adjusted that the voltage induced in the coil 161 abutting the end of the spindle permits the maximum flow areas, i.e. full opening, of the

valves

133, 133' and 133". If, on the other hand, the voltage at the pair of conductors 166 becomes lower than the set point voltage at the pair of conductors 168, the servomotor 163 begins to rotate in counterclockwise direction and moves the movable coil 161 to the lefit. As a result, the induced voltage in the coil 161 and the maximum flow areas of the valves are also reduced. This operation assures that one of the

valves

133, 133 and 133" is always farther open than the other two, but its maximum opening is so limited that the temperature at 136, 136' and 136" does not drop below the minimum temperature determined by the voltage at the pair of conductors 168. Upon reduction of the maximum flow areas of the

valves

133, 133' and 133 the rate of medium flow through the

subsidiary conduits

132, 132' and 132" is reduced and the temperature downstream of the

heat exchangers

134, 134' and 134" rises. When the voltage in the pair of conductors 1665 again becomes greater than the set point voltage in the pair of conductors 168, the servomotor 163 moves the coil 161 to the right so that the increasing voltage in this coil effects an increase of the maximum possible flow areas of the valves.

In the system shown in FIG. 4 steam from an evaporator, not shown, is fed through a pipe 201 to the superheater of a steam generator. The pipe 201 divides into four

subsidiary conduits

202, 202, 202", 202', each of which is provided with a

valve

203, 203', 203", 203", respectively. Each of the tour subsidiary conduits includes a

first superheater section

204, 204', 204", 204'", respectively, wherein steam is superheated to an intermediate temperature. Each first 'superheater section comprises a plurality of tubes connected in parallel between inlet and outlet headers. The outlet headers are individually connected by

conduits

205, 205', 205", 205" to

second superheaters

206, 206', 206", 206'", respectively, wherein the steam is superheated to the desired end temperature. Each of the

superheaters

206, 206', 206", 206" comprises a plurality of parallel connected tubes. The

superheaters

206, 206, 206", 206" discharge into

conduits

207, 207', 207", 207', respectively, which may be joined to one conduit for supplying superheated steam to a consumer, not shown. each

conduit

207, 207, 207", 207" is provided with a temperature measuring element connected to a

control signal producer

208, 208, 208', 208', respectively, which is connected by a

signal conduit

209, 209', 209", 209", respectively, to a

regulator

210, 210', 210", 210', respectively, having a proportional integral characteristic. Each of these

regulators

210, 210', 210", 210" is connected by a

control signal co-nduit

211, 211, 211", 211", respectively, to a

valve

212, 212', 212", 212", respectively, interposed in a coolant supply line 213 213, 213", 213'", respectively, leading to the

conduit

205, 205', 205", 205', respectively, for injecting cooling water for cooling the steam flowing through the conduits 2'05, 205, 205", 205". In each of the

conduits

213, 213', 213", 213" a

restrictor

214, 214, 214", 214" is provided which is connected by

pressure lines

215, 215, 215", 215", respectively, to rate of

flow signal producers

216, 216, 215", 216'. The

conduits

213, 213', 213", 213" receive cooling water from a common supply pipe 217.

Each of the rate of

flow signal producers

216, 216', 216", 216" is connected by a signal conduit 21%, 218', 218", 218', respectively, to a regulator 219, 21?, 219", 219", respectively, having a proportional integral characteristic and producing a signal fed by a

signal conduit

220, 220, 220", 220'", respectively, to a

servomotor

221, 221', 221" and 221" for actuating the

valves

203, 203', 203 and 203", respectively. The signal conduits 218, 218', 218, 213' are conducted

byv signal conduits

222, 222', 222" and 222" to a conventional device 223 wherein a signal is produced corresponding to the arithmetic mean value of the sum of the four rate of flow signals. The output signal of the device 223 is transmitted by a signal 'conduit 224 to an addition point 225 to which a conduit 226 is connected which divides into four

signal conduits

227, 227', 227", 227" which are connected at 235, 235', 235" and 235", respectively, to the signal conduits 218, 218', 218' and 218", respectively. Each of the

signal conduits

220, 220", 220", 220" is connected by a

signal conduit

228, 228', 228" and 228", respectively, to a selector unit 229 wherein the greatest of the four control signals produced by the regulators 219, 219, 219" and 219" is selected and fed by a signal conduit 230 to a point 231 which also receives through a conduit 232 a set point signal defining the desired value for the highest control signal. The point 231 is connected to the addition point 225 by a signal conduit 233.

The regulating system shown in FIG. 4 distributes the flow of steam fed through the conduit 201 into the four

subsidiary conduits

202, 202', 202", 202' in such manner that the quantities of water supplied per time unit through the

injection lines

213, 213, 213" and 213" are equal, the rates of water flow varying in dependence on the temperature of the steam emerging from the second superheaters.

Assuming that the valve 203 is fully open and there is a temperature increase at the outlet of the superheatcr 206' the temperature signal producer 208 passes a signal through the conduit 20) to the regulator 210 which causes opening of the valve 212' in the injection conduit 213 so that a greater quantity of water is injected into the conduit 205 per time unit. The increased rate of water fiow is detected by the restrictor 214 and the associated rate of flow signal producer 216 feeds a correspondingly increased signal to the conduit 218'. This increased rate of flow signal reaches the device 223 by way of the signal conduit 222' branching off from the conduit 218', whereby an increased mean value signal is formed corresponding to the increased greater signal sum and is fed by the conduit 22 to the addition point 225 from which this mean value signal is fed as a set point signal through the

conduits

227, 227', 227", 227" to the signal conduits 218, 218, 218" and 218" at the

points

235, 235', 235" and 235", respectively. A subtraction is performed between the actual value and the set point value in each

point

235, 235', 235", 235'. The regulators 219, 219" and 219" thus receive a reduced signal while the regulator 219' receives a considerably increased signal.

The

servomotors

221, 221" and 221'" thus receive through each of the

lines

220, 220" and 220" decreased signals effecting a reduction of the flow areas of the

valves

203, 203" and 203", respectively, whereas the flow area of the valve 203 is increased. A decreased signal, although still the greatest in relation to the signals in the conduits 228', 228 and 228', is now fed through the signal conduit 228 to the selector device 229 which delivers a decreased signal through the conduit 230 to the point 231. Since here the negative set point signal in the line 232 predominates, a negative signal forms in the conduit 233 and causes a reduction of the set point signal in the conduit 226. The reduced set point signal is fed through the

conduits

227, 227', 227" and 227" and 218, 218', 218" and 218" to the regulators 219, 219', 219" and 219", so that in the

signal conduits

220, 220', 220 and 220" the signals are increased eliecting some opening of the

valves

203, 203" and 203', while the valve 203' is opened still further by means of the servomotor 221'. The opening movements of the

valves

203, 203 and 203" thus compensate the previous closing movements so that the flow areas of these valves are returned to the original flow areas. As a result of the increased flow area of the throttling element 203 the portion of the total quantity of steam flowing through the subsidiary conduit 2022' increases whereby the amount of water supplied per time unit by the injection line 213' is reduced and equal quantities of water now again flow per time unit 7 through all

injection lines

213, 213', 213" and 213", the valve 2% again being fully open.

This regulating system has the advantage that a smaller range of adjustment is needed for the throttling

elements

212, 212', 212", 212", and a smaller quantity of injected Water is sufiicient than if the quantities of steam flowing per time unit through the subsidiary conduits 2-02, 202', 216 2", 292" were adjusted independently of one another. This advantage has a particularly favorable effect on thermodynamic efficiency. Moreover, the temperatures at the outlets of the superheaters 2%, 2%, 2%", 2% are substantially equalized so that the material of the tubes can safely be subjected to greater thermal stresses than Was hitherto permissible.

In another embodiment of the invention, not illustrated, the rates of flow in the four injection water conduits are not added to form a mean value, but, instead, the total quantity of injection water flowing through the pipe 21.7 per time unit is measured and divided by four.

Instead of the continuous regulators used in the described examples, it is possible to use discontinuous regulators or combinations of continuous and discontinuous regulators.

In the examples illustrated in FIGURES 1 and 3 the

conductors

148, 148' and 148 are connected to the conductors connecting the

regulators

143, 143' and 143" to the input of the

amplifiers

14 i, 144 and 144". The signals transmitted by the

conductors

148, 148' and 148" correspond to the control signals, the greatest of which is selected by the

devices

149, 149', 149". In the arrangements shown in FIGURES l and 3 the adjustment of the

valves

133, 133, 133 is proportional to the output signal of the

regulators

143, 143', 143". It is possible, however, that the apparatus interposed between the outputs of the

regulators

143, 143' and 143" and the

valves

133, 133' and 133", respectively, have an integral characteristic instead of a proportional characteristic. In this case the aforesaid control signals are not taken from the inputs of the amplifiers 1 M4 and 144/ but from the

coils

152, 152, and 152", respectively, and correspond to the position of the

valves

133, 133 and 133". This arrangement is illustrated in FIG. 5 in connection with the system shown in FIG. 3.

This application is a continuation-in-part application of my copending application Serial No. 89,032, filed February 13, 1961.

I claim:

1. A regulating system for dividing a stream of a medium into a plurality of partial streams, each stream being provided with heating means for heating the medium in the stream, comprising:

a flow rate controlling means interposed in each stream,

a temperature sensitive means in each stream down stream of the respective heating means,

a control signal producer connected to each of said temperature sensitive means for producing a control signal corresponding to the respective temperature,

actuating means connected to each of said flow rate controlling means,

a regulator operatively connected to each of said actuating means for feeding a regulating signal thereto for regulating the operation of said actuating means,

said control signal producers being individually connected to said regulators pertaining to the same streams as said control signal producers for feeding control signals from said control signal producers to said regulators,

a signal averaging device connected to said control signal producers for producing a signal corresponding to the arithmetic mean value of said control signals,

selector means operatively connected to said regulators for receiving said regulating signals and selecting the greatest of said regulating signals,

means for Producing a set point signal corresponding to the maximum desired opening of said flow rate controlling means, and

a signal comparing device operatively connected to said selector means and to said set point signal producing means for comparing the selected regulating signal with said set point signal and producing a signal corresponding to the result of the comparison,

said signal averaging device and said signal comparing device being operatively connected to said regulators for superimposing the signals produced in said devices on said control signals for producing the regulating signals regulating the operation of said actuating means for actuating said flow rate controlling means to maintain predetermined relative temperatures in all partial streams downstream of said heating means and for holding at least one of said flow rate controlling means in the predetermined maximum opening position.

2. A regulating system as defined in claim 1 including adjusting means for adjusting the control signals fed to said regulators to correspond to predetermined temperatures of the medium of said streams downstream of said heating means.

3. A regulating system as defined in claim 1 including adjusting means for adjusting the minimum value of said control signals to maintain the temperatures of the medium of said streams downstream of said heating means above a predetermined minimum value.

4. In a vapor generator having a plurality of superheaters arranged in parallel with respect to the flow of the vapor therethrough, each of said superheaters including two superheater sections arranged in series with respect to the flow of the vapor through said sections; a system for maintaining the temperature of the vapor at the outlet of the second superheater sections at a predetermined value, the system comprising:

a flow rate controlling means placed in the inlet of each of said superheaters,

a coolant supply pipe terminating in each of said superheaters between the two sections thereof for injecting a coolant into the vapor passing from the first sections to the second sections,

a valve interposed in each of said supply pipes,

regulating means connected with each of said valves,

a flow rate measuring device in each of said supply temperature responsive means connected to the outlet of each of said superheaters,

a control signal producer connected to each of said temperature responsive means for producing a control signal corresponding to the respective temperature and connected to the regulating means of the valve in the supply pipe connected to the superheater to Whose outlet temperature the control signal corresponds for maintaining a predetermined temperature at the superheater outlets,

a control signal producer connected to each of said flow rate measuring devices for producing a control signal corresponding to the respective flow rate,

an actuating means connected to each of said flow rate controlling means,

said last mentioned control signal producers being individually connected to said regulators pertaining to the same superheaters as said last mentioned control signal producers for feeding control signals from said last mentioned control signal producers to said regulators,

an averaging device operatively connected to said last mentioned control signal producers for producing a signal corresponding to the arithmetic mean value of said last mentioned control signals,

said signal averaging device and said signal comparing device being operatively connected to said regulators for superimposing the signals produced in said devices on said last mentioned control signals for producing the regulating signals regulating the operation 10 of said actuating means for actuating said flow rate controlling means to afford substantially equal flow rates of the coolant in said coolant supply pipes and for holding at least one of said flow rate controlling means in the predetermined maximum opening position.

References Cited in the file of this patent UNITED STATES PATENTS 2,800,887 Profos July 30, 1957 FOREIGN PATENTS 1,055,167 Germany Apr. 16, 1959 1,221,280 France Jan. 11, 1960

Claims

1. A REGULATING SYSTEM FOR DIVIDING A STREAM OF A MEDIUM INTO A PLURALITY OF PARTIAL STREAMS, EACH STREAM BEING PROVIDED WITH HEATING MEANS FOR HEATING THE MEDIUM IN THE STREAM, COMPRISING: A FLOW RATE CONTROLLING MEANS INTERPOSED IN EACH STREAM, A TEMPERATURE SENSITIVE MEANS IN EACH STREAM DOWNSTREAM OF THE RESPECTIVE HEATING MEANS, A CONTROL SIGNAL PRODUCER CONNECTED TO EACH OF SAID TEMPERATURE SENSITIVE MEANS FOR PRODUCING A CONTROL SIGNAL CORRESPONDING TO THE RESPECTIVE TEMPERATURE, ACTUATING MEANS CONNECTED TO EACH OF SAID FLOW RATE CONTROLLING MEANS, A REGULATOR OPERATIVELY CONNECTED TO EACH OF SAID ACTUATING MEANS FOR FEEDING A REGULATING SIGNAL THERETO FOR REGULATING THE OPERATION OF SAID ACTUATING MEANS, SAID CONTROL SIGNAL PRODUCERS BEING INDIVIDUALLY CONNECTED TO SAID REGULATORS PERTAINING TO THE SAME STREAMS AS SAID CONTROL SIGNAL PRODUCERS FOR FEEDING CONTROL SIGNALS FROM SAID CONTROL SIGNAL PRODUCERS TO SAID REGULATORS, A SIGNAL AVERAGING DEVICE CONNECTED TO SAID CONTROL SIGNAL PRODUCERS FOR PRODUCING A SIGNAL CORRESPONDING TO THE ARITHMETIC MEAN VALUE OF SAID CONTROL SIGNALS, SELECTOR MEANS OPERATIVELY CONNECTED TO SAID REGULATORS FOR RECEIVING SAID REGULATING SIGNALS AND SELECTING THE GREATEST OF SAID REGULATING SIGNALS, MEANS FOR PRODUCING A SET POINT SIGNAL CORRESPONDING TO THE MAXIMUM DESIRED OPENING OF SAID FLOW RATE CONTROLLING MEANS, AND A SIGNAL COMPARING DEVICE OPERATIVELY CONNECTED TO SAID SELECTOR MEANS AND TO SAID SET POINT SIGNAL PRODUCING MEANS FOR COMPARING THE SELECTED REGULATING SIGNAL WITH SAID SET POINT SIGNAL AND PRODUCING A SIGNAL CORRESPONDING TO THE RESULT OF THE COMPARISON, SAID SIGNAL AVERAGING DEVICE AND SAID SIGNAL COMPARING DEVICE BEING OPERATIVELY CONNECTED TO SAID REGULATORS FOR SUPERIMPOSING THE SIGNALS PRODUCED IN SAID DEVICES ON SAID CONTROL SIGNALS FOR PRODUCING THE REGULATING SIGNALS REGULATING THE OPERATION OF SAID ACTUATING MEANS FOR ACTUATING SAID FLOW RATE CONTROLLING MEANS TO MAINTAIN PREDETERMINED RELATIVE TEMPERATURES IN ALL PARTIAL STREAMS DOWNSTREAM OF SAID HEATING MEANS AND FOR HOLDING AT LEAST ONE OF SAID FLOW RATE CONTROLLING MEANS IN THE PREDETERMINED MAXIMUM OPENING POSITION.