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Патент USA US2412739

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Dec. 17, 1946. ‘ ~ I
' J, D. MCCRACKEN
APPARATUS FOR STEAM GENERATOR CONTROL
Filed May 7, 1943
2,412,739
Patented Dec. 17,1946
2,412,739
UNITED STATES PATENT OFFICE
2,412,739
APPARATUS FOR STEAM GENERATOR
'
CONTROL
James D. McCracken, Chicago, 111., assignor to
Askania Regulator Company, Chicago, 111., a
corporation of Illinois
Application May 7, 1943', Serial No. 486,050
1
4 Claims.
The invention relates generally to apparatus
for steam generator control, and more particu
larly to the control of combustible material flow
to the steam generator.
Modern, high pressure, steam generators or
boilers are designed to generate steam at very high
rates and to have relatively small capacity for
(Cl. 236-14)
2 in
supplying means. Next there is the time lag
in the controls which are responsive to the supply
of combustion air and which govern the means
supplying the fuel. Inasmuch as these time lags
are all additive, a very substantial time lag exists,
resulting in numerous undesirable conditions, in-.
cluding hunting and initial, considerable excess
storing heat energy. As a result, such generators
supply of combustion air with an- increase in
or boilers are highly responsive to the energy
load and, conversely, an initial excess fuel supply
input, that is, the supply of fuel and combustion 10 for
a large decrease in load.
'
air and are, therefore, capable of following rel~
It
is
an
object
of
this
invention,
therefore,
to
atively rapid changes in load or steam demand.
provide a new and improved apparatus for steam
An ideal method of controlling such a steam gen
generator control.
‘
7
erator would be to change the supply of fuel and
Another object of the invention is to obtain
of combustion air concurrently with load. Such
increased stability of control and to obtain such
an ideal control might be approximated by having
increa'sedstability by a simple method and appa
the means for supplying fuel and the means for
ratus.
supplying combustion air both directly respon
A further object is to provide a method of
sive to or controlled by the load. Such a method
controlwhereby a condition to be satis?ed by
of control will hereinafter be referred to as the
adjustment of two variables calls for or governs
“parallel” method or system. This method of
directly all of a ?rst variable and simultaneously
control, however, has one particular disadvantage,
part only of a second variable, the remainder of
namely, the possibilityof feeding straight fuel
the second variable being‘ called for or governed
to the boiler in the absence of combustion air
by the ?rst variable.
.
.
7
should there be a failure of the combustion air *
Another
object
is
to
provide
a
new
apparatus
supply equipment or its control. The results of
for steam generator control which attains to a
such feeding of fuel without combustion air are
degree the simultaneity of response of the “par
su?iciently disastrous in these modern steam gen
erators that a second type or method of control
has heretofore been employed.
This second method or type of control will here
inafter be referred to as the “series” method and
consists in having the load call for the required
combustion air and the air flow in turn call for
the corresponding fuel. In this way, no fuel is
supplied to the boiler without the required
amount of combustion air being available. This
method, therefore, eliminates the particularly
serious disadvantage of the “parallel” method, but
allel” system without, however, incurring the risk
of disastrously excessive fuel supply over com—_
30 bustion air supply, an inherent disadvantage of
the “parallel” system.
,
Still another object is to provide a new appa.—
ratus for steam generator control which assures
operation of the combustion air control and supply
means before the fuel supply means can respond
in full to an increase in load, but at the same time
attains a moreprompt response of the fuel supply
than can be obtained by the “series” system.
‘
has its own disadvantages, some of which will 40 Other objects and advantages will become ap
parent from the following detailed description
presently be mentioned.
‘
taken
in connection with the accompanying
Though controls have been perfected until, in
some instances, they operate substantially simul
taneously with the change in load or demand,
there is inherently in such control devices some
element of time lag, and as one control device acts
on another, and that one in turn on still another,
this time lag accumulates and builds up until
it is substantial. There is even a greater time
lag in the devices that are governed by the con
trols as, for example, the combustion air supply
ing means in a boiler. Thus in the case of the
"series” method, there is, ?rst, the time lag in
the controls responsive to the change in load.
There is next the time lag in the combustion air
drawing, composed of a single, diagrammatic ?g
ure.
.
The method of this invention has a great
' ‘variety of applications andmay be practicedby
different types of apparatus. It is, however, par
ticularly well adapted for the control of a steam
generator and will, for purposes of disclosure, be
described hereinafter as adapted to such control
of a steam generator and as practiced by a pre
_ ferred apparatus.
It is not intended, however,
.that the invention is to be limited to the particu
lar disclosure. On the contrary, it is intended to
cover all adaptations of the method and all modi
?cations or alternative constructions of therap
2,412,739
3
paratus falling within the scope and spirit of the
invention as de?ned by the appended claims.
In its broad aspects, the invention provides a
method of control whereby a condition to be sat
is?ed by the adjustment of two variables calls for
or governs directly all of a ?rst variable and
4
times, and translates that demand into an ap
propriate and proportional supply of fuel and of
combustion air. To that end, there is provided a
?rst or master regulator 8 which translates the
steam header pressure into a measure of steam
demand, a second regulator 9 which will herein
after be referred to as the load regulator or the
combustion air controller regulator, and a third
simultaneously part only of a second variable, the
remainder of the second variable being called for
regulator II] which will hereinafter be known and
or governed by the ?rst variable. In a steam
referred to as a combustion or fuel regulator.
10
generator the condition to be satis?ed is, of course, . The regulators are each “Askania” regulators
the steam demand or the load on the generator.
embodying the well known “Askania” jet pipe
The two variables are fuel and combustion air
principle.
which must be supplied in such quantities as to
More particularly, the master regulator 8 com
?ll the demand for steam and also, of course, in
prises a weight ll selected to maintain a desired
such ratio as to insure proper combustion of the
pressure in the drum of the steam generator or
fuel.
.
boiler. Opposing the action of this weight is a
In a modern steam generator, the supply of
pressure responsive device I2 connected by a con
combustion air for any considerable length of
duit 13 to the steam header 2. The weight H
time without a supply, or at least an adequate
and the pressure responsive device l2, through
supply, of fuel is, undesirable and harmful but not
an appropriate lever system It, act on an
disastrous. However, the feeding of fuel in the
“Askania” jet pipe l5 through which air‘ under
absence of combustion air produces results which
pressure is ?owing. Disposed opposite the nozzle
not only are undesirable and harmful but which
of the jet pipe I5 is an ori?ce l6 forming one
may be classed as disastrous. Accordingly, in the
terminus of a conduit H which is connected to a
method of this invention as applied to the control . .
pressure responsive device [8' arranged to act on
of a steam generator, the combustion air is the
the jet pipe [5 in opposition to the weight II. It
variable which is governed directly and com~
will
be seen from the foregoing that the primary
pletely by the condition to be satis?ed and the
impulse for the masterregulator is the pressure in
fuel is made the variable which is partially gov
erned directly by the condition to be satis?ed and 30 the steam header 2 as modi?ed by the weight H,
while the secondary impulse is the ‘pressure
partially governed by or made responsive to the
supply of combustion air, so as to assure that an
excessive supply of fuel in the absence of com
bustion air does not occur.
In‘ the drawing, there is shown diagrammat
ically a preferred apparatus for practicing the
method of this invention. As shown, I represents
a boiler or steam generator having a steam head
created in the pressure responsive device IS, the
regulator reaching a state of balance when’ the
two impulses equally affect the jet pipe 15. The
regulator 8' may thus be said to be an equilibrium
device.
.
,
,
The second or load regulator 9 comprises an
“Askania” jet pipe 20 through which a fluid under
pressure, preferably oil, is flowing. Disposed op
er 2, a combustion air intake or supply conduit 3,
a fuel supply conduit 4, here shown as project 40 posite the nozzle of the jet pipe 20 are a pair of
ori?ces 2|. The right hand one of these is by
ing‘ into and discharging in the direction of the
a conduit 22 connected to one port of a hydraulic
combustion air supply conduit, and an up-stack
motor 23, whilethe other of the, ori?ces is by
or exhaust conduit 5- for the products of com
a. conduit 24 connected to the other port of the
bustion. Thecontroller for the combustion air
hydraulic motor. The motor 23 is here shown
supply is herein shown diagrammatically as a
as a piston and cylinder device and is operatively
damper 6 located in the up-stack 5. It is to be
connected to govern the combustion air supply
understood that this is a purely symbolic show
controller represented by the damper 5. The
ing intended to represent any type of controller
regulator 9 receives its primary impulse from the
for the combustion air, supply. In actual prac
tice, such controllers take a variety of forms, in-' 50 master regulator 8, and to that end is provided
with a ?rst pressure responsive device ‘25 which is
cluding exhaust fans, blowers or other devices
by a conduit 28 connected to the conduit ll to
which may be driven by electric motors or by
be subjected to the pressure in that conduit,
steam turbines, directly or through hydraulic
which is a measure of the steam demand or load
couplings or various other media in an attempt
on the boiler. The pressure responsive device 25
to attain regulation without hunting. All of
is, of course, so arranged as to tend to move the
such controllers, whether complicated or simple,
jet pipe 23 in such direction ‘as to cause an in
director indirect, have some time lag in their op
crease of ?ow through the up-stack 5, that is,
eration. The fuel supply, likewise, is diagram
an increase in the quantity of combustion air sup.
matically shown as controlled by a damper ‘I
located in the fuel supply conduit 4. This again (ii) plied. 'In order to maintain a metered relation
ship between the steam demand and the com
is intended purely as a symbolic showing, repre
bustion air flow which in turn, under proper oper
sentative of any type of controller for the fuel
ation and after initial adjustments made, is pro
supply, whether that be one adapted for the con
portional to the energy supplied to the boiler, the
trol ofgas, liquid fuel, powdered coal, or a stoker.
These control means, likewise, have an inherent
time lag.
It is known that the vpressure in the header 2 is
a measure of the load or the steam demand on
_
or steam generator I and when prop
boiler
‘the
erly utilized and interpreted may be employed to
‘control the supply of fuel and combustion air to.
the steamgenerator. Herein the control appa
' secondary impulse on the load regulator 9 is the
combustion air flow. To that end the reguluator
has a second pressure responsive device 21 acting
in opposition to the ?rst device 25; Herein the'
combustion air flow is. measured by the pressure
drop across the boiler and, accordingly, ‘the
pressure responsive device 27 has opposite sides
thereof connected by conduits 2'8 and 29‘; ‘re
spectively, to appropriate points- of‘ the boiler.
The combustion or fuel regulator llli comprises
indication of the load or steam demand, that is,
an
“Askania” jet pipe 30 through which, as in'the
ofthe changing condition to bev satis?ed at all 75
ratus utilizes this steam header pressure as an
2,412,739
case of the regulator 9, a ?uid under pressure,
preferably oil, is flowing. Disposed opposite the
nozzle of the jet pipe are a pair of ori?ces 3|,
the right hand one of which is by a conduit 32
connected to one port of a hydraulic motor 33,
while the other ori?ce is, through a conduit 34,
connected to the opposite port of the motor 33.
Herein the motor 33 is shown as a piston and
cylinder device operatively' associated to govern
tions, the pressure in the header 2 will drop and
this pressure change will, through the conduit
I3, be [transmitted ‘to the pressure responsive de
vice l2. As a consequence, weight I I will over~
come the pressure responsive device l2 and,
through the lever system M, will pivot the jet
pipe H3 in such direction that the jet of air dis
charged therefrom will strike more directly upon
the fuel supply controller, herein symbolically 10' the ori?ce l6. This movement of the jet pipe I5
continues until the pressure in the conduit l'l,
illustrated as the damper 1.
acting through the pressure responsive device
‘ In order to obtain a more immediate response
I3, is su?cient ,to equalize the force exerted by
than is obtainable by the “series” method of regu
the lever system I 4 thereby bringing ‘the jet pipe
lation and yet eliminate the hazards and dis
astrous results of the “parallel” system of regula 15 It? to rest in this new equalized position. The
pressure in the conduits 26 and 36 is thus pro
tion, the'fuel supply in this invention is, as above
portional ‘to the steam demand and through the
stated, governed partially directly by the steam
pressure responsive device 25 acts as the primary
demand and partially by the ?ow of combustion
impulse on the regulator ,9 and causes thev jet
air. To that end the regulator In is supplied with
pipe 20 thereof to be pivoted in a direction to
two primary impulses; one the steam demand, the
cause movement of the controller 6 in such direc
other the combustion air flow. Accordingly, the
regulator is provided with a ?rst pressure re
sponsive device 35 which is by a conduit 35 con
nected to the conduit 23 and hence is subjected to
the air pressure generated in the conduit I‘! of the .
master regulator, which air pressure is propor
tional to the steam demand or load. The device
35 is, of course, arranged to urge the jet pipe 30
in such direction as to cause an increase in the
supply of fuel. A second pressure responsive de
vice 3‘! has its opposite sides connected by conduits
38 and 39 to the conduits 28 and 25, respectively,
so as to be responsive to the combustion air flow
through the boiler I. The second pressure re
sponsive device 37 is connected to act in the same
direction as the pressure responsive device 35
and the two are so adjusted that an appropriate
variation in the fuel supply is obtained for each
variation in the steam demand. It will also be
understood that the percentage of control which
each of the devices 35 and 3'! exercises may be
varied so that the fuel supply may be made ten
per cent directly responsive to the steam demand
and ninety per cent responsive to the combus
tion air ?ow, or the fuel supply may be made
twenty per cent, thirty per cent, and so forth,
directly responsive to steam demand, and cor
respondingly less responsive to combustion air
?ow to ?t any desired condition.
‘ The secondary impulse of the combustion regu
tion as to increase the flow of combustion air.
The movement of the jet pipe 20 under this pri
mary impulse is arrested and eventually stabi
lized by the pressure responsive device 21 which
receives [the secondary impulse to which the reg
ulator is subjected, namely, a measure of the
combustion air flow through the boiler.
.
Simultaneously with this increase in steam de
mand, or at least as nearly so as sensitive con
30 trols can make it, and without waiting for the
increased combustion air flow to take place,
which is delayed not only by the ‘time lag in the
controls but also in the means for producing the
increased supply of combustion air, a partial in
;-= crease in [the supply of fuel is obtained. This
results because of the partially direct control of
the fuel regulator Ill by the steam demand. This
steam demand is directly re?ected on the regu
lator ll) through the conduit 36 and the pressure
40 responsive device 35, and functions to pivot the
jet pipe 30 in a direction to bring about an in
creased fuel supply. The regulator I ii in response
to [this impulse directly from the master regula
tor 8 is, of course, adjusted to bring about a por
tion only of the total increase in fueLnecessary
to satisfy the increase in steam demand. While
the percentage of the increased fuel supply thus
obtained in direct response to the increase in
steam demand may be varied to satisfy different
conditions, this percentage in steam generators
is preferably something less than ?fty per cent.
Large steam generators are, for economic reasons,
usually not; operated onlow loads. Furthermore,
at the loads at which large steam generators are
operated a partial increase in fuel supply without
a corresponding increase in the combustion air
supply can take place without disastrous results.
lator ii! is, of course, the actual fuel supply, and
to that end the regulator ID has a third pressure
responsive device 43 intended to receive an im
pulse proportional to the actual fuel supply. The
manner in which this actual fuel supply is
measured may take a variety of forms depending
upon the character of the fuel. Therefore, the
measuring means illustrated in the drawing is
As a. consequence, a portion of the fuel supply
again but symbolic of any suitable measuring
means; Herein a restriction 4| in the fuel supply 60 may be under the direct control of the steam
demand to gain the advantage of more prompt
conduit 4 is shown with conduits t2 and 43 con
response without the possibilities of disastrous
nected at one of their ends to the conduit ll on
results should the controls not function to bring
opposite sides of the restriction and at their re
“about an increased combustion air supply.
maining ends to opposite sides of the pressure
responsive ‘device so to indicate, by the pressure -'
differential on opposite sides of the restriction,
‘the quantity of fuel supplied. The regulators 9
and it, like the regulator 8, may appropriately be
described as, equilibrium devices.
As an aid [to a better understanding of the
method andof the. function of the apparatus, the
operation thereof for a typical example will be
described brie?y. Let it be assumed, therefore,
that there has been an increase in the steam de
mand or load on the boiler. Under those condi
‘ The balance of the fuel supply is under the
control of combustion air ?ow, and to, that end
receives its impulse from the difference in air
pressure on the opposite sides of the boiler. The
pressure responsive device 37 which receive this
second primary impulse aids the device 35‘ and
between the two a full increase in the fuel supply
commensurate with the increased steam‘ demand
is obtained. The actual fuel supply createsthe
secondary impulse imparted to the regulator Hi
and, through the pressure responsive device 40,
arrests the movement of the jet pipe 30 when the
2,412,739
full increase in fuel supply called for has been
met.
‘
It is believed apparent from the foregoing that
I have provided a vastly improved method of and
8
ond device; means for measuring thecombus- '
tion air flow through the steam generator; 9. sec
ond signal generator connected to control the
power means for said ?rst device including a?rst
means connected and responsive to said master
signal generator to receive the signal generated
thereby and a second means acting in opposition
apparatus for the control of two variables, and
particularly a method of and apparatus for con
trolling the supply of fuel and combustion air in
to said ?rst means and connected to said com
a steam generator. My invention, among other
bustion air ?ow measuring means; and a third
things, decreases hunting and it does so not by
10 signal generator connected to control the power
a suppression of the oscillations, but by elimina
‘means for said second device including a ?rst
tion of ‘the cause for'such oscillations. It is the
' means connected and responsive to said master
time lag between a change in demand and the
signal generator to receive the signal generated
ful?llment of the conditions ‘satisfying that
thereby and partially to regulate the fuel supply
changed demand which causes hunting, and this
directly in accordance with the load on the steam
time leg'is reduced by at least partially increas
generator, and a second means connected di
ing or decreasing the energy input to the, steam
rectly and only to said combustion air flow meas
generator substantially concurrently with the
uring means partially to regulate the fuel supply
change in demand. This, moreover, is accom
in accordance with combustion air flow.
plished without the possibility of disastrous re
3. Control apparatus for a steam generator or
sults in the event of combustion air supply failure.
the like having a header comprising, in combina
I claim as my invention:
tion, a master signal generator responsive to the
1. Control apparatus for a steam generator or
pressure in the header and operable to generate
the like comprising, in combination, a master
a signal representative of the load on the steam
regulator responsive to the pressure of the steam
generator; a ?rst device for controlling the com
of the steam generator and operable to generate
bustion air supply to the steam generator; power
a fluid pressure signal proportional to the steam
means for adjusting said ?rst device; a second
pressure; a ?rst device for controlling the com
device for controlling the fuel supply to the steam
bustion air supply to the steam generator; a ?rst
generator; a power means for adjusting said sec
fluid actuated power means for adjusting said
ond device; means for measuring the combustion
?rst device; a, second device for controlling the 30 air ?ow through the steam generator; a'seoond
fuel supply to the steam generator; 2. second ?uid
signal generator including an equilibrium device
actuated power means for adjusting said second
device; combustion air flow measuring means; a
second regulator for translating the signal of said
master regulator into a fluid pressure signal ap
plied to said ?rst power means, said second reg
ulator being connected to said ?rst power means
to permit of the supply of fluid pressure thereto
and including a ?rst pressure responsive means
connected to said master regulator to receive the
signal generated thereby and a second pressure
responsive means acting in opposition to said ?rst
means and connected to said combustion air flow
measuring means; and a third regulator operable
to translate the signal of said master regulator
and a signal generated entirely by combustion air
flow through the steam generator into a ?uid
pressure signal governing a portion of the fuel
supply in direct response to the master signal
and the balance of the fuel supply in response to
the combustion air flow only, said third regulator
being connected to said second power means to
supply fluid thereto and including a ?rst pressure
responsive means connected to said master regu
lator to receive the signal generated thereby, a
second means connected directly and only to said
combustion air flow measuring means, and a
third means connected to be responsive to the
rate of fuel supply adapted to balance said last
named ?rst and second means when the fuel
supply equals the combined demand of the mas
ter regulator and the combustion air ?ow.
2. Control apparatus for a steam generator or
the like having a header comprising, in combina
tion, a master signal generator responsive to the
pressure in the header and operable to generate
a signal representative of the load on the steam
generator; a ?rst device for controlling the com
bustion air supply to the steam generator; power 7
means for adjusting said ?rst device; a second
device for controlling the fuel supply to the steam
generator; a power means for adjusting said sec
connected to control the power means for said
?rst device and connected to be responsive to said
master regulator to adjust the air supply entirely
and proportionally in response to the load; and
a third signal generator connected to control the
power means for said second device and con
nected to said master regulator and to said com
bustion air flow measuring means to regulate the
fuel supply partially directly in accordance with
the load on the steam generator and partially
directly in accordance with the combustion air
flow only.
a
4. In a control apparatus for a steam genera
terror the like, a master regulator connected to
be responsive to a primary impulse indicative of
the load on the steam generator and to a sec
ondary impulse generated by the regulator in re
sponse and proportional to the primary impulse
to which it is subjected; a combustion air sup
ply controller; a second regulator connected to
govern said combustion air supply controller and
connected to be responsive to the secondary im
pulse of said master regulator actingv as a pri4
mary impulse and to an impulse proportional to
the ?ow of combustion air through the steam
generator acting as a secondary impulse whereby
the supply of air is varied in direct proportion to
the load; a fuel supply controller; and a regula
tor connect-ed to govern said fuel supply con
troller, said last named regulator being connected
tosaid master regulator to be responsive to the
secondary impulse or? said master regulator to
control a portion or the fuel supply directly and
immediately in response to the load on the steam 7
‘generator and also connected to‘be responsive
directly to an impulse constituting
a measure of '
the combustion air supply exclusively, to govern
the balance of the fuel supply in accordance with
the combustion air supply only.
JAMES D. MCCRACKEN.
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