US2323013A - Means for controlling the operation of vapor generators - Google Patents

Description

, June 29 1943. G 'DEYCKER 2,323,013

MEANS FOR CONTROLLING THE OPERATION OF VAPOR GENERATORS Filed March 20, 1939 /n ventor: a: Mfleolzr *Patented June 29, 1943 ElNT ori ice mmvs roa CONTROLLING m orann- TION or VAPOR oannns'roas Gustav Decker, Berlin, Germany; vested in the Custodian Alien Property March 20, 1939, Serial No. 262,975

Application In Germany March 22, 1938 Claims.

This invention relates to a means for controlling the operation of vapor generators having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the otherend. As is wellknown in the art, controlling means are provided in such apparatus for regulating the combustion and the liquid inflow in accordance with the vapor outflow.

The primary object of our invention is to improve such control apparatus by developing a new method for deriving a measuring value for a vapor outflow. Formerly, the vapor outflow was derived from the diiferential pressure existing at an orifice plate provided in the vapor conduit.

I have found that it is advantageous to measure the vapor outflow as pressure diiierence existing between a point of measurement at the vapor part of the passage and a second point of measurement taken at the liquid part of the passage near the zone of evaporation. In this manner the additional flow resistance created by the orifice plate is avoided.

Further aims, objects and advantages of this invention are more fully explained in the following specification with reference to the accompanying drawing illustrating one embodiment of the invention by way of example only.

Referring :to the drawing, the figure is a schematic illustration of one embodiment of the invention. A once-through passage system I of the drumless boiler type is connected to a water feeding pump 2. In the feeding conduit a variable valve 3 and an auxiliary valve 4 are provided. By means of a regulator system 5 adjusting the auxiliary valve 4 the pressure difference existing at the valve 3 is maintained constant, said system 5 being a wellknown Askania jet pipe relay and need, therefore, not be more fully explained. As the pressure difference is maintained constant, as already explained, the position of the lever 6 is directly a measure for the water-inflow to the passage I.

The quantity of liquid passing through valve 3 is dependent not only on the position of this valve but likewise on the pressure drop at the valve 3.

Therefore, as long as the pressure drop at 3 can vary, the quantity of liquid entering the passage i is not only determined by the position of the valve lever 6. By maintaining constant the pressure drop at 3 by means of the'auxiliary valve 4 the liquid inflow is proportional to the position of the valve lever 6.

If for instance the inflow increases, the pressure drop at 3 increases likewise so that the jet pipe I wil1 be deflected counter-clockwise. Ac-

cordingly the cross section controlled bythe valve I will be decreased and therefore the Pressure behind the valve 3 will be increased as long as the pressure drop at I has reached its previous value in spite of the pressureincrease in front of the valve 3, so that the inflow has the same value provided the crosssection of the valve 3 has remained the same. x

As soon as the cmss'section of th valve 3 is varied by rocking the lever 8, the inflow varies accordingly. In this event an increase of the valve cross section at 3 results in a pressure increase behind the valve 3 so that the jet pipe 5 is deflected clockwise and the cross section of the valve 4 is likewise increased in order to reduce the pressure behind the valve 3 so as to return the pressure drop at 3 to its previous value.

Under normal conditions the water fed to the passage evaporates at the point I of said passage,

shortly before the water starts to evaporate. Be-

tween the points 9 and I there is a water column of a predetermined length. The measuring conduit l0 leads to a pressure regulating system H, comprising a wellknown Askania iet pipe actuating by means of a servo-motor I2 a valve i3 inserted in the vapor part of the passage. By means of this arrangement the pressure at the point 9 is maintained at a. predetermined value determined by the spring l4. Another measuring conduit l6, connected to the vaporpart of the passage at. a point 15, leads to an impulse system ll of a jet pipe regulator l8 actuating the supply control valve 3. A weight i9 corresponding to the pressure existing at the point 9 is provided at a regulator system I8 for counteracting the pressure existing in the impulse system I1. By means of this arrangement it is achieved that an impulse is effective on the regulator l8 corresponding to the pressure difference between 9 and I5. Another impulse corresponding to the water inflow operates in oppositionto this impulse in a manner to be more fully explained. Therefore, by means of the regulator is the water inflow through the valve 3 is adjusted in accordance with the pressure difference existing between points 9 and i5.. This pressure difference between 9 and I5 arises, as is wellknown, due to the flow resistance created by the part of the passage bemuch water is fed, this difference also varies in spite of equal vapor outflow if the water column between 9 and 1 varies. Provided that there is a constant vapor outflow, if the water column increases, the pressure diflerence between 9 and I5 water inflow so that the water column returns to its original length.

In the reversed case the water column between 9 and 1 decreasing, the pressure difference between 9 and l5 increases so that the regulator l8 increases so as to return the water column to its original length. By measuring the vapor outflow as pressure difference between 9 and '15, according to the invention, it is achieved that the zone of evaporation 1 is maintained at a predetermined position of the passage, the length of the superheater 9 thus remaining constant. It is an essential advantage of the present arrangement that this described regulating process takes place immediately before the temperature of the vapor can change due to variations in the length of the superheater.

A servo-motor adjusting the valve 3 and actuated by the regulator i8 is provided. The

piston rod 2i of this servo-motor bears a restoring curve 22. Said curve 22 puts a spring 23 in tension which in accordance with the position of the curve 22 creates a variable force influencing the jet pipe relay l8. Provided that the valve 3 has a linear characteristic and the curve has a true parabolic shape, the force exerted by the spring 23 would be in each position of the curve 22 a measuring value of the water inflow. By constructing the curve 22 non-parabolic, respectively constructing same adjustable, the possibility exists to correct deviations from the linear characteristic of the valve 3 and at the same time measuring deviations of the vapor outflow arising in case of changes in load. These measuring deviations are due to the fact that a part of the passage is used as flow resistance for measuring 'the pressure drop. In case of such a tube-like resistance the measurement depends on the tenacity and the velocity of flow so that the vapor outflow passing through the tube is not in true quadratic relation to the pressure drop. As these deviations from the quadratic flow rule are a function of the load and the movement of the curve is also dependent on the load, these deviations may be corrected by the choice of a certain shape of the curve 22 deviating from the true parabolic form.

A so called ratio slider 24 well known in the art is provided for changing the ratio of the impulses of the vapor outflow and the liquid inflow impulses acting on the relay [8. This slider 24 is moved by a regulating system 25 which is actuated by a temperature impulse system 23 connected to the vapor part of the passage.

A further regulating system 21 is provided for regulating the fuel supply. An electric motor 28 actuates a wandering'grate 29 of a wellknown pulverize-flring system. A measuring turbine 30 connected to a motor 28 creates in the conduit 3i a pressure proportional to the fuel quantity. This measuring pressure is conducted to 9. diaphragm chamber 32 of the regulator system 21. A further measuring conduit 33 connects a measuring point 34 at the vapor part of the passage to a pressure impulse system 35. A weight 33, corresponding to the weight l9, counteracts the pressure in the impulse system 35 so that an impulse is effective on the regulator 21 in accordance with the pressure difference existing between the measuring point 9 and, said impulse should be a measure for the vapor outflow, but it is not correct because within the measuring path a variable resistance is inserted, i. e. a valve l3. In order to receive a true measuring value for the vapor outflow an impulse system 31 is provided which createsin a wellknown manner a pressure impulse in the conduit 38 proportional to the pressure difference existing on both sides of the valve l9. This correcting impulse additionally actuates the combustion regulating systern 21, the conduit 38 being connected for this purpose to a diaphragm chamber 39 of the regulator 21.

The measuring point 34 from which the vapor outflow impulse for the combustion regulator system is derived lies behind the valve l3, whilst the measuring point i5 from which the vapor outflow impulse for the liquid supply is derived lies in 'front of said valve l3. It is not possible to connect the measuring conduit 33 in front of the valve l3, because in this case the vapor outflow impulse actuating the combustion regulator 27 would remain uninfluenced due to the operation of the valve l3 bythe conditions of vapor consumption. However, these condition are essential for the combustion regulation as the combustion is then readjusted in accordance with the increase or decrease of the vapor need, whilst the water inflow is readjusted in accordance with the true quantity of vapor created in the passage. The fuel supply is immediately increased, if a greater vapor need is indicated by a pressure drop behind the valve i3, whilst the liquid supply is enlarged only after the increase in the fuel supply has already become effective and has supplied a greater quantity of vapor.

The arrangement of the measuring point 34 behind the valve l3 necessitates the correction of the vapor outflow impulse by meansof the impulse system 31 as described above. Obviously, such a correction must take place in all cases in which within the measuring range 9-34 a variable flow resistance is inserted or connected parallel. This may be the case, for instance if a variable shunt is provided parallel to the superheater 9 for regulating the temperature of the vapor.

Having thus described my invention and one embodiment thereof, I desire to be distinctly understood that I am not to be limited thereby except as to the claims in view of .prior art.

I claim:

1. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other end comprising in combination means for supplying liquid to said passage, liquid supply control means, a pressure impulse system connected to be in response to the vapor pressure in said passage and to actuate the said supply control means, a pressure regulating system connected to be responsive to the liquid pressure in said passage at a point near the zone of evaporation for keeping a predetermined pressure constant at this point.

2. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other end comprising in combination a liquid supply control valve arranged in the liquid part of said point in the liquid part of such passage near the zone of evaporation, a restoring cam operatively connected to said servo-motor, an adjustable ratio slider arranged between said cam and said jet pipe, and means for automatically adjusting said ratio slider in response to the temperature in the vapor part or said passage.

3. Apparatus for automatically controlling the operation oi a vapor generator having a oncethrough fiuid passage receiving liquid at one end and delivering superheated vapor at the other end and heated by elements of combustion, comprising in combination, means for supplying liquid to said passage, liquid supply control means and an impulse system for actuating said control means, said system including first means for producing an impulse in response to the pressure at a point in the vapour part of the passage and second means for producing a predetermined counter-impulse corresponding to the intended pressure at a second point in the liquid part of said passage near the zone of evaporation, said supply control means being connected to be actuated by said impulse means.

4. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering superheated vapor at the other end and heated by elements of combustion, comprising in combination, means for supplying liquid to said passage, liquid supply control means, a pressure impulse system connected to e responsive to the vapor pressure in said passage and actuating said liquid supply control means, and a pressure regulating system connected to be responsive to the liquid pressure in said passage at a point near the zone of. evaporation, a valve arranged in the vapor part of said passage connected to be adjusted by said pressure regulating system so as to maintain a predeter-' mined pressure constant at this point.

5. Apparatus for automatically controlling the operation of a vaporgenerator having a oncethrough passage receiving liquid at one end and delivering vapor at the other end and heated by elements of combustion, comprising in combination, means for supplying liquid to said passage, liquid supply control means and an impulse system for actuating said control means, said system including liquid supply responsive means and counteracting load responsive means including first means for producing an impulse in response to the pressure at a point in the vapour part 01' the passage and second means for producing a predetermined counter-impulse corresponding to the intended pressure at a second point in the liquid part of said passage near the zone of evaporation, said supply control means being connected to be actuated by said impulse means.

6. An apparatus for automatically controlling the operation or a vapor generator having a once-through passage receivingliquid at one end and delivering superheated vapor at the other end and heated by elements of combustion, comvalve, a servo-motor connected to adjust said valve, a relay for controlling said servo-motor, an' impulse system for actuating said control valve including'liquid supply responsive means and counteracting load responsive means including first means for producing an impulse in response to the pressure at a point in the vapour part of the passage and second means for producing a predetermined counter-impulse corresponding to the intended pressure at a second point in the liquid part of said passage near the zone of evaporation, said supply control means being connected to be actuated by said impulse means.

7. An apparatus for automatically controlling the operation of a vapor generator having a oncethrough passage receiving liquid at one end and delivering superheated vapor at the other end and heated by elements of combustion, comprising in combination, a liquid supply control valve, means for maintaining a predetermined pressure drop at said valve, a servo-motor connected to adjust said valve, a jet pipe relay for controlling said servo-motor, a load responsive impulse system for actuating said jet pipe relay, said system including first means for producing an impulse in response to the pressure at a point in the vapour part of the passage and second means for producing a predetermined counter-impulse corresponing to the intended pressure at a second point in the liquid part of said passage near the zone of evaporation, and restoring means operated by said servo-motor for restoring said jet pipe relay.

8. An apparatus for automatically controlling the operation of a vapor generator having a oncethrough passage receiving liquid at one'end and delivering superheated vapor at the other end and heated by elements of combustion, comprising in combination, a liquid supply control valve, means for maintaining a. predetermined pressure drop at said valve, a servo-motor for actuating said valve, a relay for actuating said servomotor, a load responsive impulse system for actuating said relay, said system including first means for producing an impulse in response to the pressure at a point in the vapour part of the passage and second means for producing a predetermined counter-impulse corresponding to the intended pressure at a second point in the liquid part of said passage near the zone of evaporation, a restoring cam operatively connected to said servo-motor for varying the ratio of the liquid supply and said pressure difierence in dependence on the generator load, and spring means arranged between said relay and said cam for yieldingly transmitting the restoring impulse to said relay.

9. An apparatus for automatically controlling the operation of a vapor generator having a once-through passage receiving liquid at one end and delivering superheated vapor at the other end and heated by elements of combustion, comprising in combination, a liquid supply control valve, means for maintaining a. predetermined pressure drop at said valve, a servo-motor for controlling said valve, a relay for actuating said servo-motor, a load responsive impulse system for actuating said relay, said system including first means for producing an impulse in response to the pressure at a point in the vapour part of the passage and second means for producing a predetermined counter-impulse corresponding to the intended pressure at a second point in the liquid part or said passage near the zone of evaporation, a restoring cam operatively connected to said servo-motor for varying the ratio of I 10. Apparatus for automatically controlling the operation of a vaporgenerator having a oncethrough fluid passage receiving liquidat one end and delivering superheated vapor at the other end and heated by elements of combustion, comprising in combination, means for supplying liquid to said passage, liquid supply control means,

asaaois' an impulse system for actuating said control means, said system including liquid supply responsive means and counteracting load responsive means, including first means for producing an impulse in response to the pressure at a point inthe vapour part oi the passage and second I means fpr producing a predetermined counterimpulse corresponding t the intended pressure at a second point in the liquid part oi! said passage near the zone of evaporation, a ratio slider for varying the ratio between the liquid supply and the load, and means for automatically adjusting: said slider in response to the temperature'in the vapour part or said passage.

GUSTAV DECKER.

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