Note: Descriptions are shown in the official language in which they were submitted.
ll~8~3~1
As used herein, the word "air" or the words "dry air" ; *
include any combustion-supporting or oxygen containing gas, and ;
the word "gas" includes any combustible gas or gaseous mixture
containing one or more combustible gases. ~ ;
The basic method of this invention includes the follow-
ing steps: `
(1) combustible gas is mixed with dry air or other
combustion-supporting or oxygen-containing gas;
(2) mixture is burned in a pair o~ flames; ;
(3) temperatures of these flames or burned gases are
monitored;
(4) volume ratio of the gases is adjusted so as to
maintain the average of said temperatures at substantially maxi-
mum;
(5) said volume ratio of said gases which produces ;
said maximum average temperature is measured and is substantially
proportional to the calorific value. -
" The flow rates of these gases may be measured by a
single flow sensing system which is, preferably, of the turbine ~;~
flowmeter type whereby a measured ratio of said flow rate if
obtained and is substantially proportional to the calorific
value. Alternately, the volumetric flow rate of the air or
combustion-supporting gas may be regulated at a constant value
with the volumetric flow rate of the combustible gas being
measured.
In accordance with the present invention, the employ-
ment of a single flow sensing system is of great advantage. At
the pressures and flow rates typically involved in a calorific
measuring device, turbine meters have been found to be superior
to other types of flowmeters. But because of inevitable manu-
, , , ,;, , , ~ , , " , ,, " ~,, , , " :,", , :" ,, , . , , "
~ 108338~ -
~ .,
facturing variances between flowmeters, it is difficult to find
a "matched pair" suitable for use together in a single apparatus,
thus necessitating complex compensating circuits in the electric -
signal processing equipment which monitors the flowmeters. When
all flow measurements are made with a single flowmeter, as in
the present invention, the need for matching flowmeters or com-
pensating for their mismatch is avoided.
The aforesaid measured volume ratio is referred to ~ -I
hereinafter as "critical combustion ratio" and may be defined
..
as that volume ratio of the gases which produces maximum average
10 flame temperatures when said gases are premixed and burned. It -
has been found that the critical combustion ratio of these gases -~
varies substantially directly with the calorific value of the ;~
combustible gas and that a very accurate indication of calorific
value can be obtained by measuring said critical combustion ratio.
: ," .
As set forth in the aforesaid Clingman, Jr. patent, `
it is well-known that the adiabatic temperature of a flame that `
is produced by burning a mixture of combustible and combustion-
supporting gases is a function only of the initial temperature, `~
pressure and chemical composition of the mixture and that said
20 adiabatic tempsrature is reached in the combustion zone of the ;~ ;
flame only if there are no heat losses from the burning gases. -
Also, if the ratio of combustion-supporting gas to combustible ~ ~
~ :.
gas is varied in the initial mixture, the adiabatic flame
temperature varies and a critical ratio between the gases exists
at which said adiabatic flame temperature is at maximum. If
the initial mixture contains less combustion-supporting gas when
required to achieve this critical ratio, the adiabatic flame -~
temperature is lower and this is generally due to insufficient
oxygen being present to achieve complete combustion whereby less !;
: ~8;~381
heat is released. In the event that the initial mixture contains
combustion-supporting gas in excess of that required to achieve
the critical ratio, the adiabatic flame temperature is again
lower and is generally due to the necessity of heating such
excess. Thus, the critical ratio between the gases is equal to
the critical combustion ratio defined hereinbefore.
Objects of the invention include the provision of an ;`
improved method of and means for measuring the calorific value -
of combustible gases which are not dependent upon measuring the ;
amount of heat released in combustion, which utilize a single
,~ .
flow sensing system, preferably, of the turbine flowmeter type,
to measure the flow rates of both combustible and combustion-
supporting gases or said flow rate of said combustible gas may
be so measured while said flow rate of said combustion-supporting
gas is maintained at a constant value, which are not affected
by the turbine calibration factor of the sensing system, which
are relatively simple, which are capable of continuous simple
operation, which are not affected by ambient temperature and
other varying environmental factors and which are adaptable to -
automatic calibration.
FIG. 1 is a diagrammatic view illustrating an apparatus
for carrying out one of the methods of this invention,
FIG. 2 is a diagrammatic view of the controller of
FIG. 1,
FIG. 3 is a diagrammatic view showing a modified
apparatus for carrying out another method of the invention.
FIGS. 4-6 are diagrammatic views showing other embodi-
- ments of the invention; and
FIG. 7 is a diagrammatic view of the controller of
FIG. 6.
- . . : , . . . ... .
~83381
In the drawings, the numeral 1 schematically deslgnates
an apparatus for accurately measuring the critical combustion
ratio or caloric value of a combustible gas which comprises a
pair of burners 2, 3 respectively communicating with an air inlet
4 and a combustible gas inlet 5. A ~luid conductor or main air ;
line 6 connects the base of the burner 2 to the air inlet 4, and
said burner base communicates with the gas inlet 5 through a `
fluid conductor or main gas line 7. The main air and gas lines
6, 7 are connected to the base of the burner 3 by branch fluid ~-
conductors or lines 8, 9, respectively, said gas line 7 having
an egress portion 11 of extended length. It is noted that the
base of each burner is so constructed that it functions as a
mixing chamber for the gas and air conducted thereto by the
lines 6, 7, 8, 9. As will be described more fully hereinafter,
a forked or Y-shaped fitting 10 is mounted in the ingress portion
of the main air line or conductor 6 adjacent and downstream of
the air inlet 4.
A suitable control or servo valve 13 is mounted in the ~'
main gas line 7 adjacently downstream of the gas inlet 5 for
accurately regulating flow therethrough. This valve is adapted
to be actuated electrically by a controller or servo 15 in such -,
manner as to keep at a predetermined value the electrical signal -
emanting from thermocouples 16, 17 connected in electrical
opposition to each other and disposed within carbon monoxide
flames 18, 19 of the burners 2, 3, respectively. Reference to
FIG. 7 and accompanying description of the Clingman, Jr. patent
is made for an illustration of the structure and operation of
a suitable controller capable of actuating the gas control valve
in accordance with the present invention. As will be apparent,
30 the gas control valve 13 is actuated in such manner that the ~
~'
--4--
~833~
temperature difference between the burner flames 18, 19 is
maintained constant; also, the air to gas ratio is always hi~her
in burner 3 than in burner 2 due to a flow restrictlon orifice
30 being mounted in the air line 6. Thus, the sign of the
temperature difference between the flames depends on whether
the ratio of total air flow to total gas flow is richer or leaner
than the flow required to maximize the temperatures of said
flames. Usually, one of the thermocouples 16, 17 is set at a
different position in its flame than the other flame whereby the
temperature difference between said thermocouples is a constant
plus the temperature difference between the flames.
As set forth in connection with the two burner embodi-
ment (FIG. 3) of the Clingman, Jr. patent, the thermocouple
temperature difference is maintained at a value corresponding
to substantially maximum average temperatures of the flames by
the coaction of the valve 13 and controller 15 which keeps the
gas flow in that proportion which maximizes flame temperature.
A pair of forked or Y-shaped fittings 21, 23 are
-inter-posed in the main gas line 7 between its egress portion
. ~
20 11 and control valve 13, with the first and second arms of the ~ ~;
upstream fitting 21 spaced from and extending downstream toward
the respective first and second upstream extending arms of the
downstream fitting 23. The respective first arms of the pair
of fittings are connected to each other by a branch line or
secondary conductor 25, while a parallel line or secondary
conductor 27 joins the respective second arms of said fittings.
The upstream fitting 21 divides or splits the gas flow evenly
between the secondary conductors, and the downstream fitting
23 returns both streams to the egress portion 11 of the main gas ~ ;
line. A flow restriction orifice or capillary tube 29, 31 is
:. .
~ 83381
mounted in each secondary conductor 25, 27, respectively, so as
to maintain the same flow of gas through each conductor. For ..
measuring the flow of gas therethrough, the secondary conductor
27 has a flowmeter 33 of the turbine type connected therein
downstream of the capillary tube 31.
The forked or Y-shaped fitting 10 mounted in the large :~
~A;
ingress portion of the main line or conductor 6 adjacent and
downstream of the air inlet 4 has its arms extending downstream.
One of the arms of the itting 10 forms a part of the main air i.
,. :
line, while the other arm communicates with a branch line or
secondary conductor 12. A flow restriction orifice or capillary :..
tube 14, 20 is connected in each conductor or line 6, 12 down-
stream of the Y-shaped fitting for maintaining the flow of air :i
through conductor 12 in constant proportion of the air flow llne ~: ~
15 6. The ratio between the flow orifices or capillary tubes 14, ~ .
20 is such that only approximately 5% to 10~ of the total flow
of air through the air inlet passes through the secondary con-
:., - , .
ductor 12. A solenoid valve 22 is mounted in the latter, down- -
stream of its capillary tube 20, and has a pair of egress con-
ductors 24, 26 communicating with the secondary conductors 25,
27, respectively, of the main gas line 7 downstream of the
respect~ve capillary tubes 29, 21. The solenoid valve 22 is
adapted to be actuated by a controller 28, of the sequential or
step type, which is electrically connected thereto and to the
turbine-type flowmeter as well as to a recorder 32 which may be
of the chart type.
As will be more fully described hereinafter, the -:
controller 28 comprises diyital electronic circuit for switching
the valve 22 between (to and from) two positions, for sensing ..
the spin of the turbine of the flowmeter 33 and, at the end of
i
3381 ~:
each measurement cycle, transmits the ratio of air to gas for -
that cycle to memory. In a complete measurement cyale, the ;
solenoid valve is placed by the controller in a first position
adding air from the inlet 4 -- through the secondary air con-
ductor 12, capillary tube 20 and egress conductor 24 -- to the
secondary gas conductor 25. In the first position of the valve
22, the rate o~ spin of the turbine of the flowmeter is pro-
portional to (G2) the flow of gas through secondary gas con-
ductor 27. After the solenoid valve is switched to its second `~
position by the controller 28, the flowmeter turbine 33 requires ~-
about sixty (60) to ninety (90) seconds to commence to spin at
a steady rate.
Each time the solenoid valve is switched, starting of
the next step is delayed for approximately ninety (90) seconds.
15 Also, approximately ninety (90) seconds after the valve 22 ~
switches to its first position, the controller initiates counting ~'
of the revolutions of the flowmeter turbine and, in most in-
stances, the number of counts per revolution equals the number
of turbine blades. In any event, the controller 28 measures (Nl) :
20 the number of counts per second and stores this number in a ;
suitable memory register (not shown). The number (Nl) is pro-
portional to (G2) th~ gas flow through secondary gas conductor 27. -
Then, the controller 28 switches the solenoid valve
to its second position and waits approximately ninety (90) seconds ;
before commencing the count of turbine revolutions. The con-
troller measures (N2) the number of counts per second, which is
- proportional to (G2 + A2) the gas flow through secondary gas
conductor 27 plus the flow of air through said secondary con-
ductor from secondary air conductor 12 by means of egress con-
ductor 26. Then, the controller produces an output signal to
1~83381 ~
the recorder 32 in proportion to (N2-N1)/ (N1~, thereby com-
pleting the cycle.
Preferably, the pressure drops across the solenoid
valve 22, flowmeter turbine 29 and burners 2, 3 at the flow rates
re~uired for stable flames are of the order of one (1") inch of ~i
water or less. The flow orifices or bores of the capillary tubes
14, 20, 29, 31 are of such diameters that the pressure drop
thereacross is at least ten pounds per square inch (10 psi).
As a result under these conditions, the flows of fluids through ;
.~
capillary 14 of the main air line 6, through capillary 20 of `~
the secondary air conductor 12 and through capillaries 29, 31
. . .
of the secondary gas conductors 25, 27 are substantially constant
and independent of the position of the solenoid valve.
Since the gas flow orifices or capillary tubes 29, 31
15 are of the same size, the flow of gas through each of the con- ;;
ductors 25, 27 is equal whereby Gl equals G2 and whereby G2 is
in a constant ratio to the total gas flow. To a first approxi~
mation, the flow rates through the air flow orifices or capillary
tubes are proportional to the pressure differences thereacross
and the pressure differences are the same for both, the upstream
..... ..
and downstream pressures being constant. Thus, the air flow
(A2) through the secondary air conductor 12 is in a constant
ratio to the total air flow, and the coaction of the servo valve `~
13 and the controller 15 keeps the ratio of total air to total ``
gas flow in proportion to the calorific value of the gas whereby
(N2-Nl)/(Nl) is proportional to said calorific value.
As shown in FIG. 2, the controller 28 may comprise ~`
a sequence controller 34, a pair of counters 35, 36 connected `
by a pair of electrical leads 38 to the turbine flowmeter 33 of ~ `~
the secondary gas conductor 27, and a divider 37 connected by
.
-8~
~C~833~
electrical leads 39, 40, respectively, to the counters 35, 36. ;
A pair of electrical leads 41 connects the sequence controller
34 to the solenoid valve 22, electrical leads 42, 43 connect the
first counter 35 to said sequence controller, and the latter is
connected to the second counter 36 by an electrical lead 44 and
to the divider 37 by an electrical lead 45. The recorder 32 is
connected to the divider by a pair of electrical leads 46. A
series of electrical voltage pulses is adapted to be produced
by ~he flo~meter 33 and transmitted by the leads 38 to the first
and second counters 35, 36 of the controller 28, the frequency
of these pulses being in proportion to the flow of gases through
said flowmeter.
The sequence controller 34 is a timing circuit which -
operates the solenoid valve 22 and the components of the con- ;-
troller 28 in accordance with the aforesaid electrical pulses.
At the beginning of each cycle, no power is transmitted by leads
41 to the solenoid valve until after ninety (90) seconds, at
~hich time, the sequence controller activates the first counter
35 by means of a voltage signal transmitted by lead 42. This `
first counter records each pulse conveyed thereto by leads 38
from turbine flowmeter 33. After approximately ten tlO) seconds, `
this voltage signal is removed and electrical power is applied
to leads 41 so as to activate solenoid valve 22. After ninety
(90) seconds, the second counter 36 is activated by a voltage
signal through lead 44. Then, the first counter 35 is reactivated
in a reverse direction by a voltage signal applied through lead 43.
At the end of about another ten (10) seconds, both counters are
deactivated. The number of counts of turbine revolutions remain-
ing on the first counter is then proportional to the air flow -
(A2) and the number of counts on the second counter is proportional
~1~833~
,...
to the gas flow (G2). Next, the lead 45 conducts a voltage
pulse or signal from the sequence controller 34 to the divider
37 so as to activate the latter. Voltage pulses conducted
through the respective leads 39, 40 from the first and second ~ .
S counters 35, 36 to the divider are in proportion to the number
of counts remaining on said respective counters and said divider
produces an output signal that is in proportion to said voltage ;
pulses conducted by said leads. This output signal is displayed r'~`~
by the recorder 32 and is in proportion to the calorific value.
10 Then, the cycle of operation is repeated. ~ ;~
In the above description of the method of measurement
the roles of combustible gas and combustion supporting gas can
be reversed. That is the gas whose calorific value is to be
measured can enter at 4 and the air can enter at 5. In this
embodiment the calorific value would be in proportion to
Nl/(N2-Nl), which Nl and N2 are determined as described above.
FIG. 3 shows an alterate embodiment of the invention;
parts corresponding to those in the embodiment of FIG. 1 are
given corresponding reference characters with primes (') appended.
20 Like the embodiment of FIG. 1, that of FIG. 3 utilizes only a -
single flowmeter, preferably a turbine flow meter, and hence
provides the same advantage of avoiding the problems of comparing
.; .
measurements from two meters, each of which has its own mechanical ~
: . .
idiosyncracies that affect accuracy of flow measurement.
In the embodiment of FIG. 3 a pair of burners 2', 3',
are provided in which fuel-air mixtures are burned in a manner
so that the average temperatures of the two flames are maximized,
as discussed above. Air is supplied through inlet 4' to main
air line 6' which delivers part of the air to the burner 2' `
through one of the legs of a Y-fitting 10' connected in the main -
'.,'
-10- ;, ~
~ 333~
air line. Gas is delivered through inlet 5' to main gas line
7' where its flow rate is measured by turbine flowmeter 33'.
Egress portion 11' of the main gas line delivers a portion of
the gas through one leg of a Y-fitting 23' to the burner 3' and
5 has a branch line 9' connected to the other leg of the aforesaid
Y-fitting 10' for directing the remainder of said gas to the
burner 2'. Upstream of the latter fitting, a branch line 8'
extends from the main air line 6' to the other leg of the afore-
said Y-fitting 23' for delivering the remainder of the air to
10 the burner 3'. Due to this flow arrangement, separate mixtures 3
of air and gas are provided for separate burning.
The air to gas ratio in burner 2' will always be higher
than that in burner 3' by reason of a flow restriction orifice
50 in egress portion 11' in the main gas line.
Gas flow to burners 2', 3' is controlled through the
loop consisting of thermocouples 16', 17', located respectively
in flames 18', 19', controller or servo 15' and servo operated
valve 13', susbstantially in the manner described above in `
connection with FIG. 1.
ao In accordance with the invention, the embodiment of `~
FIG. 3 is provided with equipment for regulating the air flow
through line 6' so that the volumetric flow rate is constant
notwithstanding variations in ambient temperature and pressure,
and consequent variations in the temperature and pressure of
the air entering inlet 4'. This equipment includes control
valve 51 in ingress portion of line 6', capillary 52 in line 6'
downstream from valve 51, a pressure sensor 53 positioned to
sense the pressure in capillary 52 at a selected point 53a there-
along, a pressure sensor 54 downstream from capillary 52, a
comparator 55, a signal processor 56, a signal input means 57 to
--11--
1~833~3~
processor 56, and a thermocouple 58, exposed to the ambiént air.
Signal conducting lines connect the pressure and temperature
sensors and the comparator 55 and processor 56. The equipment
just identified collectively comprises a constant volume flow `
regulator.
The regulator delivers air to the burners at a pressure
substantially equal to ambient pressure.
The dimensions of capillary 52 are selected so that
the air flow through it is laminar, at least from the selected -~
point 53a to the exit end thereof. Selected point 53a is so
located that the pressure drop between it and downstream pressure
sensor 54 is small compared to the magnitude of the downstream
pressure, which is substantially ambient.
The mode of operation of the regulator is as follows:
Two inputs (voltages) are delivered to the signal processor 5~.
One of these is generated by thermocouple 58, and reflects the -`
ambient temperature. The other is an externally supplied
constant input (voltage), which may be conveniently provided
by a selectably variable voltage source, delivered through means
57. The magnitude of the externally supplied input at 57
determines the flow rate through line 6', and in equations set
forth below is designated B.
Signal processor 56 may be a simple analogue computing
device of known character that multiplies the externally supplied
input by the square root of the absolute temperature (represented
by the thermocouple-supplied input) to produce an output or
product signal which is delivered to the comparator 55. The
output signal of the signal processor thus varies with variations
in the ambient temperature. It varies with the externally supplied
input only when the latter is deliberately changed for the purpose
-12-
1~833~3~
of changing the ~olume flow rate in air in line 6'.
Comparator 55, as has been pointed out, receives the
output signal of signal processor 56. In accordance with the
invention, it also receives pressure signals from pressure sensors ~`
53 and 54. Comparator 55 first creates a pressure differential
signal by subtracting signal 54 from signal 53. The so-created ~ `'
pressure differential signal is then compared in comparator 55
with the product signal from the signal processor and an output
or central signal is sent from the comparator to control valve 51
for opening or closing it to bring the product signal and the
pressure differential signal into equality. -~
The flow of fluid considerations which underlie this
control arrangement for providing an automatically regulated
constant volume flow ratio of air are as follows: Because the
flow through the capillary 52 is laminar, the volumetric flow
. ,
rate, F, is given by the following expression:
A(p2 p2) (1)
F = 1 o
T \ 1/2
U o P ':.
1 T o
where-
A = a constant depending on dimensions of the capillary.
Ul = viscosity of air at temperature Tl in OK.
To = ambient temperature in K.
Tl = a constant (selected) reference temperature in K.
Pl = pressure at sensor 53 in capillary.
PO = pressure at sensor 54 donwstream of capillary.
~5
13
., .. . . . -- . . .. -... . ... : ... . ..
1~33~
Since, as was pointed out above, (Pl - PO) is much smaller
than PO, by reason of the selection of points 53 and 54,
equation (l) can be rearranged as follows:
; .
l o [2Po + (Pl - Po)] (2)
~To~ O
Ul ~ T J
,''~`' "
Furthermore, when Pl - P = To B, as occurs in the
control system as outlined above (B being the selected constant
input to signal processor 56), and (Pl -~PO) is small, equation
(2) can be simplified to:
''', ~
F=2AB
1 ( 1 )1/2 (3)
.
all of whose terms are constants. One constant, B, is manually ;~-~
10 variable, as explained above, and the flow rate F varies ;
directly with it.
In connection with the foregoing development of -
equations, it should be noted that to a first approximation, `
the viscosity of air varies with the square root of the tempera- -
l~ ture and is independent of the pressure, and these facts have
been exploited in the control arrangement described above.
Since, in the embodiment of FIG. 3, the volumetric flow
rate is constant and controlled, there is no need to measure it
in the course of determining the calorific value of the gas. As
20 has been outlined above, the servo 15' automatically adjusts the
volumetric flow of gas through valve 13i so that it is in the
i
-14-
1~8338~
same proportion to the constant volumetric air flow as the
inverse calorific value of ~he gas. Gas flow alone is measured -~
by turbine 33' and counter 36'. The signal from counter 36' is
processed in divider 37' where it is converted to convenient
analogue form for driving recorder 32'. The output from divider
37' is in inverse proportion to the signal from counter 36'. `- -
In the apparatus of FIG. 3 the roles of combustion-
supporting gas and combustible gas can be reversed provided the
combustible gas is always of the same type so as to have the
same viscosity. In this case the air would enter conduit 5' and `
the combustible gas would enter conduit 4'. The output from `
divider 37' is in proportion to the signal from counter 36'.
The embodiment of the invention illustrated in FIG. 4
is capable of operation in two different modes, one of which
is essentially the same as that described in connection with
FIG. 1 above, and the other of which is quite similar to that
described in connection with FIG. 3. In addition, the equip-
ment is arranged to conveniently be placed in two test modes,
one of which permits checking on the presense of and character `
of oscillations in the turbine meter, and the other of which
permits checking of the effectiveness of the solenoid operated ;
valve which plays a key role in the operation of the equipment
in one mode.
In FIG. 4, the apparatus designated generally as
60 includes a pair of burners 61, 62; a fuel inlet 63; an air
inlet 64; various lines, capillaries, valves, etc. described
below for delivering fuel and air from the inlets to the burners;
and control equipment, also described below.
~15-
83381
1 The fuel delivery system includes a line 65 contain-
ing a filter 66, which is pxeferably of a type adequate to
remove particulates down to 0.3 micron, and a pressure regu-
lator 67, preferably of the nonventing type, since it handles ; -
flammable gas. Line 65 also contains servo valve 68, which
is operated ~y control equipment discussed below to establish `~
a gas flow which maximizes the average flame temperature in
burner 61, 62.
Downstream of servo valve 68, line 65 is split into ;:
two branches, line 70 leading to burner 61 and line 71 leading ;
to burner 62. Lines 70 and 71 contain capillaries 72, 73
respectively, which serve to divide the gas flows between
lines 70 and 71 in substantially fixed ratio throughou~ the .
operating range of the unit. Preferably capillaries 72, 73
,.. ~.
are sized with respect to each other so that the flow through
line 70 is about twenty percent greater than the flow through ~ `
.: .
lin~ 71. A turbine flow meter 74 is mounted in line 70 where
only the fuel gas being delivered to burner 61 passes through
,.
it. An advantage of the foregoing arrangement (which is
shared by the device of FIG. 1 but not by that of FIG. 3) is
that less gas is passed through the turbine in a given period
, .:. .
of operation, resulting in less wear on the parts of the meter.
The air delivery means of the apparatus of FIG. 4
includes a line 75 containing filter 76, which, like fuel
gas filter 66, is preferably of a type adequate to remove
particles down to 0.3 microns. Downstream of filter 76 is a
pressure regulator 77, which is preferably of the vented type,
which establishes and maintains a substantially constant ;
pressure in line 75 just downstream of regulator 77 by more or
less continually venting a small amount of air through vent 78.
-16~
~08;~381
1 At its left hand end, as FIG. 4 is drawn, line 75
is split into two branches, line 79 leading to burner 61 and
line 80 leading to burner 62. Lines 79 and 80 contain capil~
laries 81, 82 respectively, which are equal in dimensions so
5 that the air flows through lines 79 and 80 are equal sub- ;
stantially throughout the operating range of the unit.
Between regulator 77 and the point where line 75
splits into burner lines 79, 80, another branch line 83 is ` ~
included in the air delivery system. Branch line 83 contains ~ -
a capillary 84 which is sized with respect to capillaries 81, 82,
so that only a small fraction of the air passing through regulator `
77 passes through line 83. Branch line 83 terminates in a
solenoid valve 85, which has two output lines, 86 and 87.
Output lin~ 86 delivers air passing through line 83 and solenoid
valve 85 into gas line 70 upstream of tu~bine flow meter 74.
Qùtput line 87 is provided with a blocking valve
88 and a side vent valve 89. With vent valve 89 closed and
blocking valve 88 open, line 87 delivers air from solenoid
valve 85 into gas line 70 downstream of turbine meter 74. On
the other hand, with the blocking valve closed and the vent
valve open, air is vented to the atmosphere through valve 89.
Operation of the apparatus and the processing of
flow measurements to yield calorific value data are accomplished
through controller 90, whose operation may best be understood
from a consideration of FIG. 2 above, and FIG. 7 below, to-
gether with their accompanying descriptions. The apparatus
associated with controller 90 includes thermocouples 91, 92,
positioned in the flames of burners 61, 62, as discussed above,
servo valve 68, flow meter 74, solenoid valve 85, and recorder
93.
1083381
1 In one of its operational modes, the apparatus of
FIG. 4 flows gas through lines 65, 70, and 71 to burners 61,
62. Air is flo~ed to the burners through lines 75, 79 and 80. i
Air is also bled into gas line 70, through branch line ~3 and `-
solenoid valve 85. In this mode of operation vent valve 89 ~;
is closed and valve 88 is open. The controller 90 cycles
solenoid valve 85 so that part of the time air is bled into
gas line 70 upstream of turbine meter 74, and part of the time
it is bled into line 70 downstream of the meter. Flow meter
10 data is processed under each condition after a time delay to -~
permit the meter to stabilize to the new flow rate.
Since the mixture in burner 61 always has more air ;~
in it~than the mixture in burner 62, the flame temperatures
of the burners will always differ. Thermocouples 91, 92 detect -
.
this difference, and act through controller 90 and servo valve
68 to adjust the fuel flow rate to maximize the average flame `
, . .:
temperature. The flow meter readings under the alternate air -
bleed conditions are processed to produce a ratio between air
flow and fuel flow, which ratio is proportional to calorific
value. The ratio is displayed and recorded on recorder 93.
In its other operational mode the apparatus of FIG. 4 -
again flows fuel to the burners through lines 65, 70 and 71.
The flow rates through lines 70 and 71 differ by reason of
the difference in sizes of capillaries 72, 73. In this mode ~
25 of operation, solenoid valve 85 is maintained by controller - ~-
90 in position to feed air into line 87. Blocking valve 88
is closed, and vent valve 89 is open. EIence the air passing
through solenoid valve 85 is not fed into gas line 70, but
rather is vented through valve 89.
-18-
.. . .. ., , .. , . . . .. . . , . . , .-.- . .. .. ... ,. . . . -
3338~ ::
;
1 In this mode of operation, air is flowea to the
burners through lines 75, 79 and 80. Because of the dimension-
ing o capillaries 81, 82, the air flow rates to the burners
are substantially identical. In addition, the arrangement
of regulator 77 tpreferably vented) and capillar-es 81, 82,
has been found to produce an extremely uniform air flow rate.
This circumstance is exploited in accordance with the inven- -
tion to eliminate air flow measurement in the second mode of `~
operation.
In the memory of controller 90, a constant for air
10w rate is stored. This value is processed with turbine
meter data to produce an air flow to fuel flow ratio which is
. .
proportional to calorific value, and which is displayed and
recorded. Again, fuel flow rate is continually adjusted to
maximize flame temperatures.
The apparatus of FIG. 4 can be arranged into two
test modes for trouble-shooting and evaluative purposes. In
the first of these, the fuel and air flows are the same as
just described in connection with the second operational mode,
but the fuel flow rate is held constant by controller 90.
This permits oscillations and perturbations of the turbine -~
meter, if any, to be isolated and observed. Any oscillations ' ~
which occur are not due to variations in fuel flow rate, and `-
must be attributed to, and traced to, other causes, such as
mechanical defects.
In the other test mode, vent valve 89 is closed,
blocking valve 88 is open, and solenoid valve 85 feeds the
bleed airstream into line 87, and thus into uel line 70 down-
stream of meter 74. Thus air10w is not measured in this
test mode, but the flow rates are otherwise similar to those
,~
', -.~ . .
-19- . ~
-" ~083381
. ~
1 obtaining in the first operational mode discussed above,
-~ assuming that the califoric value of the fuel gas is holding
fairly constant. By alternately operating the apparatus in
this test mode, and in the first operational mode, and compar-
ing results, one can obtain an indication of how satisfactorily
solenoid valve 85 is operating. If the califoric value readings
; differ significantly between the two modes of operation, then
the valve is not switching flow between lines 86 and 87 properly.
` The form of apparatus shown in FIG. 5 is much like
10 that shown in FIG. 4, and the parts which are the same are
` given the same reference numbers with primes added. Basically,
the equipment of FIG. 5 iS arranged to operate in the second
of the two operational modes discussed above in connection ;
with FIG. 4, that is, with the air flow rate held constant
15 but unmeasured, and with the fuel flow rate varied to maximize
flame temperature.
In accordance with the invention, the apparatus of
FIG. 5, provision is made to alternately feed the fuel gas
of interest (the "unknown gas"~ and a standard gas of known
20 calorific content (the "knowledge") into fuel line 65 in
order to automatically calibrate the system. Thus, fuel inlet
63' has a solenoid valve 100 at its entrance. Known gas is
introduced through line 101, and unknown gas is introduced
through line 102 . Controller 90' switches solenoid valve 100 ;
25 periodically to direct first one gas and then the other into ~`
fuel inlet line 63.
In operation, air flow to the burners is constant
. !,
and equal, as discussed above in connection with FIG. 4, second
operational mode. Fuel flow is automatically adjusted in
30 response to the thermocouple measurements to maximize flame
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83381
1 temperature, no matter which of the gases, known or unknown,
is flowing at the time.
One of the electrical factors employed by controller
90' to process turbine meter measurements into a direct
indication of calorific value is a proportionality constant
(which is preferably stored in the memory of a microprocessor
within the controller, but which may be otherwise handled
therein in accordance with the state of the art).
The operator of the unit, by manipulation of a
dial on controller 90', inserts a value into the unit related
to the calorific value of the known gas. This value is used
by the sequence controller to adjust the proportionality ~-
constant stored within the controller when the known gas is `
flowing through the unit to a value such that the display at
recorder 93' reports a calorific value which is equal to
that of the known gas. The value so dialed into the controller
is maintained during the next interval of operation, when -
the unknown gas is flowed through the unit. The proportionality
constant may again be adjusted when solenoid 100 next switches
known gas into the unit. Simple, quick, and substantially
automatic calibration is thus continuously provided in
accordance with the invention. Because the equipment of the
invention has the characteristic of a fast response time to
changes in califoric value, the intervals when the standard
or known gas is passed through the unit may be relatively
short, thereby minimizing consumption of known gas.
The form of the invention shown in FIG. 6 includes
all of the features of FIG. 4, together with the automatic
calibration feature of FIG. 5. For this reason corresponding
parts are given the same reference characters with double
primes. From the discussion above it can be seen that the
equipment of FIG. 6 thus has two primary operational modes:
.
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333~
1 one in which part of the air is periodically fed through the
turbine meter for measurement purposes; and one in which the
air flow is maintained constant but unmeasured. In the later
mode, the option is provided for continuous and substantially
automatic calibration against a known gas, in accordance with
the discussion of FIG. 5. Furthermore, the equipment of
FIG. 6 can be switched into the two test modes of FIG. 4 for
evaluating turbine oscillations and solenoid valve operation., -
FIG. 7 shows in simplified schematic form control ;
equipment forming part of the apparatus of FIG. 6. With
suitable simplifications to delete functions not performed,
this control equipment may also be used with the units of
FIG. 4 or FIG. 5. ~ ~
The controller 9Q" may comprise a sequence controller ; ;
110, a pair of counters 111, 112, connected by a pair of
electrical leads 113 to the turbine flow meter 74" in line
70", and a divider 114 connected by electrical leads 115,
116, respectively, to the counters 111, 112. A pair of elec~
trical leads 117 connects the sequence controller 110 to the
solenoid valve 85"; electrical leads 118, 119 connect the
first counter 111 to said sequence controller; and the
latter is connected to the second counter 112 by an electrical
lead 120, and to the divider 114 by an electrical lead 121.
The recorder 93" is connected to the divider by a pair of
electrical leads 122.
The equipment of FIG. 7 described thus far is -
substantially the same as the equipment of FIG. 2, and it
operates in the manner described in connection with that FIG. ~o
opreate the device of FIG. 6 in the mode in which air is
periodically bled into line 70" upstream of turbine meter 74".
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- - - .... , . . - , : - - . . : :.. ,.. . .. : . .. .. .. , . :
1~83381 :~
:" :
1 Controller go" al90 includes a servo controller 123 as
a part thereof. Its structure and function are substantially -
the same as the separate servo controller 15 of FIG. 1. `~
For controlling operations and measurements in the
5 modes of operation in which air flow is held constant but ~-
unmeasured, controller 90" has a reference input device 124,
which is connected by electrical lead l25 to sequence con-
troller 110. In the modes of operation in which air flow is
not measured, counter 112 is not used to record revolutions ;~
of turbine meter 74. Instead, a fixed number of counts is
,.,.., ~,
stored in counter 112. The number of counts is input to the
counter by manually setting a number on reference input device
124, which may be a set of ten-position switches connected `
in a logic circuit. The sequence controller 110 adjusts counter
112 until the number st~red therein is equal to that set on
the reference input device 124, which number is a substitute
for or equivalent of an actual air 10w measurement for use `
in further processing turbine meter data.
The sequence controller periodically activates counter
20 111 for a fixed period of time ~hile fuel gas is passing ~;
through the turbine meter. Counter 111 counts turbine meter
revolutions during each such time interval. The count so
obtained is divided into the number stored in counter 112 by ;~
divider 114, and the result obtained is displayed and recorded
at recorder 93".
During the intervals when counter 111 is not
activated, sequence controller 110 activates servo controller
123 so that it can operate servo valve 68" to adjust fuel
flow to maximize flame temperature in response to data sensed
:"
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1~833~1 :
l by the thermocouple.
The device is manually calibrated in the fixed-
but-unmeasured air flow mode of operation by substituting a
gas of known calorific value for the gas of interest and
manually changing the number input at the reference input
device until the value displayed at recorder 93" is that of
the known gas.
As explained above, solenoid valve 100" provides ~;
for automatic calibration of the unit against a known gas.
An input related to the known calorific value of the standard
gas is manually set at the reference input device 124. Most `~
of the time the unit operates with unknown gas passing
through it. Periodically, however, the sequence controller ~
activates solenoid valve lOO" to switch known gas into the ~ ;
unit, and small adjustments can then be made if needed in ~:
the number input at the reference input device to maintain
the instrument accurately calibrated.
,; , '
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