Abstrict A mass rate flow meter is provided having a universally-mounted
gyroscopic apparatus against which a fluid stream, the mass rate
of flow of which is to be measured, is directed. The fluid drives
the rotor of the gyroscopic apparatus at and angular velocity proportional
to the fluid stream velocity and impinges upon a pressure pad mounted
on the gyroscopic apparatus, such that the effective impingement
force is applied asymmetrically to the rotor, thereby applying a
torque to the gyroscopic apparatus proportional to the dynamic pressure
of the fluid stream and causing precessional rotation of the gyroscopic
apparatus. The resulting precessional rotation of the gyroscopic
apparatus is at a rate proportional to the mass rate of flow of
the fluid. Measurement of the precessional rotation of the gyroscopic
apparatus provides an indication of the mass rate of flow, and totalization
of the precessional rotations provides total mass flow indications.
Claims What is claimed is:
1. Apparatus for measuring the mass flow of a fluid in a flow stream
comprising:
a gyroscope having an impeller rotor;
means for directing a portion of said flow stream against said
impeller to spin said impeller at an angular velocity proportional
to the velocity of said flow stream;
means for deriving a force proportional to the momentum of fluid
in said flow stream and applying such force as a precessional force
on said gyroscope; and
means for sensing the resulting precessional movement of said gyroscope.
2. Apparatus as in claim 1 wherein said impeller rotor includes
peripheral vanes, and said vanes being formed with a centrally-disposed
circumferentially-extending groove.
3. Apparatus as in claim 1 wherein said gyroscope is disposed with
a conduit.
4. Apparatus as in claim 3 wherein said force deriving means includes
a flow deflection device disposed asymmetrically of said rotor for
deriving such precessional force by deflection of a portion of such
flowing liquid.
5. Apparatus as in claim 4 wherein said last-mentioned means is
a deflection plate.
6. Apparatus as in claim 4 wherein said last-mentioned means is
a flow diverting tube.
7. Apparatus as in claim 6 wherein the diversion portion of said
tube is spaced from the axis of rotation of said rotor.
8. Apparatuas as in claim 7 including a pair of oppositely-directed
diversion vanes normally in registry with the outlet of said diverting
tube, said diversion vanes being mounted such that as said rotor
is tilted out of its normal plane of rotation the relative registry
of said outlet with said vanes is altered to generate a corrective
precessional force on said rotor.
9. A method for measuring the mass flow of a fluid flowing in a
stream comprising:
impinging a portion of such flow stream on the rotor of a gyroscope
to spin said rotor at an angular velocity proportional to the velocity
of said flow stream;
deflecting a portion of said flow stream;
applying the force generated by such deflection to said gyroscope
as a precessional force; and
sensing the resulting precessional movement of said gyroscope.
10. Apparatus for measuring the mass flow of fluids comprising:
a housing having inlet and outlet ports and defining a flow path
for communication of fluid flowing therethrough between said ports;
a gyroscope mounted within said flow path for movements about at
least two mutually-perpendicular support axes, said gyroscope including
a rotor mounted for movements about a mutually-orthogonal spin axis;
first means responsive to said fluid flowing through said housing
for imparting rotary motion to said rotor of said gyroscope about
said spin axis in proportion to the velocity of said fluids;
second means responsive to said fluid flowing through said housing
for applying a torque about one of said perpendicular support axes
of said gyroscope in proportion to the momentum of said fluid; and
third means for sensing precessional movement of said gyroscope
about the other of said perpendicular support axes of said gyroscope.
11. The apparatus of claim 10 wherein said gyroscope is mounted
for unidirectional precessional rotation about said other of said
perpendicular support axes.
12. The apparatus of claim 11 wherein said housing defines an annular
orifice in said flow path, said rotor has a body presented to said
annular orifice and said first means comprises vanes disposed about
the circumference of said sphere, such that fluid exiting said annular
orifice impinges upon said vanes at all degrees of precessional
rotation of said gyroscope.
13. The apparatus of claim 12 wherein said second means comprises
a pressure pad asymmetrically mounted with respect to said one of
said perpendicular support axes of said gyroscope, such that fluid
exiting said annular orifice impinges upon said pressure pad at
all degrees of precessional rotation of said gyroscope.
14. The apparatus of claim 11 wherein said rotor body is spherical.
15. The apparatus of claim 10 further comprising fourth means for
sequentially reversing the direction in which said second means
applies torque about said one of said perpendicular support axes
and said gyroscope being mounted for oscillating precessional rotation
about said other of said perpendicular support axes.
16. The apparatus of claim 15 wherein said housing defines an arcuate
port in said flow path, said rotor has a disc-shaped body presented
to said arcuate port and said first means comprises vanes disposed
about the circumference of said disc, such that the fluid exiting
said arcuate port impinges upon said vanes over the entire breadth
of oscillatory precessional rotation of said gyroscope.
17. The apparatus of claim 16 wherein said second means comprises
a pressure pad symmetrically mounted with respect to said one of
said perpendicular support axes of said gyroscope and at least two
jets asymmetrically and oppositely mounted with respect to said
one of said perpendicular support axes, and said fourth means sequentially
causes fluid to flow through said jets to impinge upon said pressure
pad in an alternating asymmetrical manner with respect to said one
of said perpendicular support axes of said gyroscope.
Description The present invention relates generally to fluid flow measurement
and, more specifically, to improved apparatus for accomplishing
the measurement of mass of fluid flow. This invention is particularly
advantageous in measuring the mass flow of gases or fluids of high
gas content.
Mass measurement of fluid flow is extremely difficult because of
the critical relationship between mass flow and the fluid density
and viscosity, and because of the numerous factors causing variations
in these characteristics. Nevertheless, accurate measurement of
the mass flow of fluids is necessary as volumetric measurements
can belie the exact amount of fluid flowing in a fluid stream. This
is particularly true in the case of gases and fluids of high gas
content.
Information concerning mass rate of flow of fluids can be derived
in several known ways. Most commonly, devices coming under the general
heading of rate meters or obstruction meters are placed in the fluid
stream, such as orifices, flow nozzles, venturis, weirs, rotameters,
ultrasonic meters and electromagnetic meters to measure the velocity
of the flow stream. The velocity information is combined with known
or inferred information as to the cross-section of the flow stream
to determine volumetric flow rate. Mass flow may be readily inferred
therefrom if the density of the fluid is either known, as in the
instance of most liquids, or where a gas flow is under constant
conditions, or where density of the flow stream is otherwise determined.
However, if the density of the flow stream varies significantly,
e.g., as in the cases of gaseous fluids under varying conditions
of pressure and temperature, the volumetric flow rate obviously
does not fully represent the mass of product flow. In such instances,
some density or mass per unit volume determination must be added
to obtain an accurate measurement or calculation of mass flow. In
attempts to use those prior flow meter arrangements for measuring
mass flow, utilizing known methods for securing some form of output
signal responsive to the mass rate of fluid flow characteristic,
the output signal often is erroneous because of its unresponsiveness
to variations in fluid density and viscosity, whereupon appropriate
modification of the signal by complex correction equipment has been
required to afford a meaningful output. Further, external power
sources often are necessary to operate the sensing, compensating
or read-out equipment. Moreover, many such arrangements are primarily
of laboratory or complex stationary installation types, and do not
possess simplicity and ruggedness of construction, reliability of
operation and accuracy of indication under all conditions which
are required for general purpose applications.
It has been recognized that it would be desirable to measure mass
flow directly with a flow meter which automatically compensates
for density changes, and various such flow meters have been developed.
For example, in one such type of flow meter, the fluid is caused
to flow through a tortuous conduit, with some means being provided
to sense the forces generated by the change(s) of flow direction
as an indication of the mass flow. For example, the tortuous flow
path (conduit) section may be rotated or oscillated such that a
force is produced, by gyroscopic principles, from movement of the
fluid, which force is related to the mass rate of flow of the fluid.
In another type of mass flow meter, an impeller is placed in the
fluid stream and rotated at a constant speed to accelerate the metered
fluid to a predetermined angular velocity about the axis of impeller
rotation, and a resiliently restrained reaction turbine in downstream
relationship to the impeller is disposed such that the accelerated
fluid impinges upon it and occasions measurable angular deflection
related to mass rate of flow of the fluid. In general, however,
none of the prior art flow meters for measuring mass flow directly
have been sufficiently simple and independent of external power
sources to gain widespread acceptance.
It is an object of this invention to provide improved mass rate
flow meters.
A more particular object of this invention is to provide improved
mass rate flow meters which automatically compensate for density
change to yield output signals directly related to the mass rate
of flow of the metered fluid, and which obviate the need for correction
equipment.
It is another object of this invention to provide improved mass
rate flow meters which yield output signals which are a linear function
of the mass flow rate of the metered fluid and exhibit a zero reading
for conditions of zero flow such that no special totalization equipment
is required to sum mass flow units.
It is another object of this invention to provide improved mass
rate flow meters which accomplish the aforesaid objects without
necessitating the use of external power sources.
A further object of this invention is to provide improved mass
rate flow meters which meet the aforesaid objects and which are
economical to produce and are rugged and reliable in operation and
easy to maintain.
Further and additional objects and advantages of this invention
will appear from the description, the accompanying drawings and
the appended claims.
In carrying out this invention in one embodiment, a mass rate flow
meter is provided comprising a gyroscopic apparatus which is mounted
within the flow path of a fluid stream, the mass rate of flow of
which is to be measured, with freedom for movements of the gyroscopic
apparatus about at least two mutually perpendicular support axes.
The meter includes a rotor mounted for movements about a spin axis
mutually orthogonal to the support axes, and a pressure pad disposed
for the flowing fluid to impinge thereon and to apply an effective
impingement force to the rotor structure asymmetrically of the spin
axis. The flowing fluid imparts rotary velocity or spin to the rotor
proportional to the velocity of the fluid. The momentum of the flowing
fluid striking the pressure pad applies a torque about one of the
support axes, causing precessional rotation of the gyroscopic apparatus
about the other support axis. The precessional rotation is proportional
to mass flow rate and is determined by appropriate read-out methods.
For a more complete understanding of this invention, reference
should now be had to the embodiments illustrated in the accompanying
drawings and described below by way of examples of the invention.
In these drawings:
FIG. 1 is a perspective schematic view of a gyroscopic apparatus
against which a fluid stream, the mass rate of flow of which is
to be measured, is directed in accordance with teachings of the
present invention;
FIG. 2 illustrates, in an exploded, partly sectional and partly
perspective view, one embodiment of a mass rate flow meter constructed
in accordance with teachings of this invention, including a gyroscopic
apparatus mounted for oscillatory precessional rotation;
FIG. 3 is a slightly enlarged, partly sectional side view of the
mass rate flow meter of FIG. 2;
FIGS. 4 and 5 are slightly enlarged plan views of a jet valve and
jet housing of FIG. 2 the jet valve being shown in FIG. 4 in a
first extreme position relative to the jet housing whereat the orifices
of a first pair of jets in the jet housing are exposed and the orifices
of a second pair of jets in the jet housing are covered, and the
jet valve being shown in FIG. 5 in a second extreme position whereat
the orifices of the first pair of jets are covered and the orifices
of the second pair of jets are exposed;
FIG. 6 is a slightly enlarged, perspective view of the gyroscopic
apparatus and back-pressure outlets of FIG. 2 the length of the
arc .theta. between the back-pressure outlets defining the limits
of oscillatory precessional movement of the gyroscopic apparatus;
FIG. 6A is an enlarged schematic view of a compensating flow tube
as one alternative arrangement for applying precessional force to
the gyroscopic apparatus of FIG. 1;
FIG. 7 is a schematic of a fluidic amplifier control unit for the
oscillatory meter of FIG. 2;
FIG. 8 illustrates, in an exploded partly sectional and partly
perspective view, a presently preferred embodiment of a mass rate
flow meter constructed in accordance with teachings of this invention,
including a gyroscopic apparatus mounted for unidirectional precessional
rotation;
FIG. 9 is a slightly enlarged, partly sectional view of the mass
rate flow meter of FIG. 8 shown with an alternative nut and bolt
assembly and a read-out mechanism;
FIG. 10 is a slightly enlarged plan view of the gyroscopic apparatus
of FIG. 8 as seen from the right side of FIG. 8; and
FIG. 11 is a slightly enlarged plan view of the cylindrical and
frustoconical inserts of FIG. 8 illustrating an annular orifice
formed by these inserts for directing the flow of the metered fluid
against the gyroscopic apparatus.
Referring now to the drawings, FIG. 1 schematically illustrates
a gyroscopic apparatus 10 used for measuring the mass rate of flow
of a fluid through a conduit 8 in accordance with teachings of
this invention. The gyroscopic apparatus 10 comprises a sensing
rotor 12 journaled for rotation on an axle 13 in an annular ring
14 which is, in turn, supported for angular movement in a major
gimbal 16 by minor axis trunions 18. A bearing (not shown) fixed
upon a stationary support frame 19 mounted in the conduit passage
provides support for angular movement of a major gimbal trunion
20 therein. The rotor 12 is thus afforded angular freedom about
both a minor suspension axis y corresponding to the axis of trunions
18 and a major suspension axis z corresponding to the axis of trunion
20. The rotor spin axis x and both of the suspension axes are normally
mutually perpendicular. The rotor 12 comprises an impeller 22 including
vanes 24 about the circumference thereof. An arcuate shroud 26 extends
from the annular ring 14 about a portion of the circumference of
the impeller 22 covering the impeller 22 and thus the vanes 24
of the wheel in one upstream quadrant through an angle of approximately
90.degree.. The gyroscopic apparatus 10 further comprises a pressure
pad 28 affixed to the annular ring 14 at an asymmetrical position
relative to the minor suspension axis y. The component may be counterbalanced
as necessary for stability, such as by added weight to counterbalance
the asymmetrically-located pad 28 and the shroud 26.
The gyroscopic apparatus 10 is shown in FIG. 1 disposed in the
position required to meter the mass rate of flow of a fluid stream
flowing downwardly through the conduit 8 about the gyroscopic apparatus
as depicted by the large arrow at the top of FIG. 1. The moving
fluid acts upon the vanes 24 causing the sensing rotor 12 to spin
at an angular velocity .omega..sub.r proportional to the velocity
of the fluid passing about the gyroscopic apparatus 10. An effective
net force F.sub.1 is developed by impact of the flowing fluid on
the pressure pad 28. This force, acting on the x axis at an effective
radius r.sub.1 from the y suspension axis, creates a couple C tending
to rotate the annular ring 14 and rotor 12 of the gyroscopic apparatus
10 about the y axis. As is known to those skilled in the art of
gyroscopes, torques applied about a gyro minor axis, such as the
y axis here, results in precession of the gyro about the major axis,
i.e., about the z axis here, at an angular velocity .OMEGA.. Little
or no motion occurs about the y axis, because as precession occurs,
an equal and opposite couple is created which resists the effect
of force F.sub.1. The precession of the gyroscopic apparatus 10
caused by force F.sub.1 thus causes the major gimbal 16 and trunion
20 to turn at an angular velocity .OMEGA. on the bearing of the
stationary outer frame 19.
As is more fully set forth hereinafter, the speed of rotation of
the major gimbal 16 and trunion 20 has been found to be proportional
to the mass flow rate. Accordingly, through any one of a variety
of suitable transducer systems, the mass flow rate can be indicated
from the rate of precessional rotation of the major gimbal 16 or
trunion 20 and the total mass of fluid flowing through the meter
over an interval of time can be determined by counting or totalizing
this precessional motion.
One type of transducer system is illustrated schematically at 27
comprising a magnetic drive coupling 27m from trunion 20 to a register
shaft 27s which is connected to a register head 27h. The head 27h
may be a register or a further transducer to provide output signals
to a remote computer or read-out device, not shown. Such magnetic
coupling drives to registers are known in the fluid meter art, see
e.g., U.S. Pat. No. 3972233.
The nature of a gyroscopic apparatus is that it must react in quadrature
to any application of forces or torques. This requires that additional
provision be made to permit development of any output torque on
the major gimbal trunion 20. Referring to FIG. 1 the application
of the force F.sub.1 causes rotation of the major gimbal trunion
in the direction indicated. If resistance to rotation of the major
gimbal occurs, such as by the presence of bearing friction on the
trunion 20 viscious friction or loading by a transducer output
for indicating the rate and/or amount of precessional movement,
a couple is developed in the xy plane which will cause the gyroscopic
apparatus to precess in such a manner that the system will rotate
about the y axis in the direction of the torque F.sub.1 r.sub.1.
The result is an unloading of the force F.sub.1 and a serious rolling
of the spin axis such that no satisfactory output torque can be
developed.
A further problem is that it is necessary that the rotor 12 remains
in and turns symmetrically in the yz plane, and that the x axis
remains horizontal. Because it is possible for the gyroscope to
maintain any angle with the yz plane without tendency to "return
to the vertical position" if not disturbed, it is required
that some method be employed to cause the gyroscope to stabilize
itself in the yz plane and provide forces which automatically maintain
this orientation.
One design by which these problems can be solved is seen in FIG.
8. A groove or notch 30 is provided in the center of each of the
vanes 24 on the rotor 12. Although the theoretical explanation is
not fully understood, it has been discovered that the addition of
such notches in the rotor vanes stabilizes the rotor. Thus, although
there may be resistance to the rotation of the major gimbal trunion,
with such notches its effect apparently is negated and the hereinafter
assumption of negligible friction is appropriate.
As an alternative to the use of a pressure pad 28 to apply a momentum-derived
force F.sub.1 about the y axis, a flow tube may be used to generate
a precessional couple force proportionate to the mass flow, as generally
illustrated in FIG. 6A. For example, a flow tube 29 parallel to
the z axis and which is open at the upstream end 29a and closed
at the downstream end 29b and having a lateral discharge nozzle
30 in its side which is spaced from the y axis and opens in a direction
parallel to the x axis, may be fitted on the axle 13 or to the annular
ring of the minor gimbal 14 within an enlarged major gimbal. The
change in momentum of the fluid in the xy plane as it exits from
the discharge tube would result in a thrust, i.e., a precessional
force F.sub.1 (FIG. 6A), in a direction parallel to the x axis and
spaced from the y axis, creating a couple about the y axis. To stabilize
such a gyroscopic apparatus, a set of superposed deflector vanes
or conduits 31a and 31b are supported on the major gimbal and positioned
to normally be in register with the nozzle 30 for diverting the
flow from the discharge tube in two separate opposed discharge paths
normal to the xz plane. The deflector vanes will create equal and
opposite forces acting at a common radius from the x and z axes
as long as the gyroscopic apparatus remains in the "centered"
position. When the gyroscopic apparatus moves out of the "centered"
position, the nozzle 30 will move up or down relative to the two
deflectors whereby a greater proportion of the discharge from nozzle
30 would be intercepted by one deflector vane than by the other.
An imbalance in the amount of fluid diverted in each direction will
result, thereby creating a difference in the forces in the respective
directions about the z axis and, thus, a net correcting torque about
the z axis.
Referring now particularly to FIGS. 2 through 7 one specific embodiment
of a mass rate flow meter 32 according to this invention is shown.
The meter 32 includes a gyroscopic apparatus 34 mounted for oscillatory
precessional rotation at a rate directly and linearly proportional
to the mass flow rate of fluid passing through a conduit in or on
which the flow meter 32 is mounted. In addition to the gyroscopic
apparatus 34 the flow meter 32 includes an inlet assembly 36 a
jet assembly 38 an outlet assembly 40 and a fluidic amplifier control
unit 42 having back-pressure outlets 43a and 43b.
Referring particularly to FIGS. 2 and 3 the inlet assembly 36
includes a mounting plate 44 for spanning a conduit, a hollow open-ended
first cylinder 46 a plug 48 a second cylinder 50 and a collar
51. The plug 48 is inserted into one end 52 of the cylinder 46 and
includes a threaded inlet port 56 in a face 58 thereof disposed
externally of the cylinder 46 an outlet port 60 in a face 62 thereof
disposed internally of the cylinder 46 and a passage 64 communicating
the inlet port 56 with the outlet port 60. The cylinder 46 and plug
48 are mounted on the mounting plate 44 which has an opening 66
therethrough which is at least coextensive with the inlet port 56.
The second cylinder 50 is hollow and includes one closed end 68
and an open second end 70 secured to the face 62 of the plug 48
about the outlet port 60. The second cylinder 50 further includes
passages 72 (best seen in FIG. 3) in a side wall 74 thereof. The
collar 51 is mounted concentrically about the outside of the other
end 54 of the cylinder 46 and flush with the end 54.
The second cylinder 50 acts as a regulator, collecting the fluid
which is to be metered and maintaining a more uniform velocity profile
in the interior of the first cylindrical housing 46. In this manner,
turbulence of the metered fluid is elminated as well as problems
of directed velocity. Moreover, the fluid flow into the interior
of the first cylindrical housing is a uniform flow of a more homogeneous
density with time. While this regulatory feature is not necessary
to the performance of the apparatus, it contributes to a more accurate
operation of the apparatus. Obviously, the system provides greatest
accuracy under steady state conditions. While transient errors may
occur during dynamic changes, such errors will tend to be mutually
cancelling and average out, thereby being of little or no net effect
as in many other dynamic reaction metering systems.
The jet assembly 38 includes a plug 76 a jet valve 78 and a jet
housing 80. The plug 76 includes a solid first cylindrical body
portion 82 defined by a first wall 84 and a solid second cylindrical
body portion 86 defined by a second wall 88 of a lesser diameter.
The first cylindrical body portion 82 of the plug 76 fits within
the end 54 of the cylinder 46 such that the shoulder or seat 96
thereof is flush with the end 54 of the cylinder and the collar
51. Passages 98 are provided through the first cylindrical body
portion 82 having inlet ports 90 disposed internally of cylinder
46 and outlet ports 94 disposed in the seat 96. A pin-limit stop
102 protrudes from the seat 96.
As seen in FIG. 3 the second cylindrical body portion 86 extends
externally of the cylinder 46. A passage 108 (FIG. 3) extends through
the first and second cylindrical body portion and provides communication
between an inlet port 100 in the face 92 and outlet port 104 in
the forward face 106. The inlet port 100 is of an area substantially
greater than that of the outlet port 104 and the cross-sectional
area of the passage 108 is successively reduced therebetween to
form a throat, such that the velocity of fluid passing therethrough
is increased. An arcuate baffle 100 is provided at the outlet port
104 which baffle is defined by inner and outer lips 112 and 114.
The baffle 100 directs and concentrates the flow of the fluid toward
the vanes 24 as its exists the outlet port 104. The second cylindrical
body portion further includes a central recess or counterbore 116
in the forward face 106.
The jet valve 78 includes an annular ring 118 having first and
second arms 120 and 122 extending radially therefrom. The annular
ring 118 includes passages 124 for selective registration with
ports 94 and an arcuate channel 126 therethrough. The annular ring
is of an inner diameter to fit loosely over the second cylindrical
body portion 86 of the plug 76 and is adapted to be concentrically
positioned about the second cylindrical body portion of the plug,
resting upon the surface formed by the seat 96 the end 54 of the
cylinder 46 and the collar 51. The pin-limit stop 102 on the first
cylindrical body portion extends into the channel 126 in the annular
ring 118 when the jet valve 78 is positioned on the plug 76. The
pin 102 and channel 126 cooperate to permit limited relative angular
movement between the jet valve and the plug. In a first extreme
position of the jet valve relative to the plug, as in FIG. 4 i.e.,
when the pin 102 has engaged one end of the channel 126 a first
pair of the passages 124 in the jet valve and outlet ports 94 at
one side of the assembly 38 will be aligned, and the passages 124
at the other side are out of registry with the respective parts.
When the jet valve is in its second extreme position of FIG. 5
i.e., when the pin has engaged the other end of the channel 126
of the jet valve, the second pair of passages 124 in the jet valve
will be aligned with the pair of outlet ports 94 at the other side
of the assembly 38 and the first pair of passages and corresponding
pair of outlet ports will no longer be in alignment.
The movement of the jet valve is controlled by a fluidic amplifier
control unit 42 shown in FIG. 2 in block form. A pin 128 controlled
by the fluidic amplifier control unit engages within a slot in arm
122 and reciprocates linearly between first and second positions
to cause circumferential reciprocation of the jet valve between
the aforementioned first and second positions. The fluidic amplifier
control unit acts responsive to signals from sensing or back-pressure
outlets 43. The operation of the fluidic amplifier control unit,
back-pressure outlets 43 and pin 128 is depicted in the schematic
drawing of FIG. 7 and each will be described more fully hereinafter.
Referring further to FIGS. 2 and 3 the jet housing 80 comprises
an annular ring 130 including first, second and third body portions
132 136 and 140 formed with first, second and third annular surfaces
144 146 and 148 respectively. Radial openings 143 are provided
within the third cylindrical body portion 140 to accommodate the
arms 120 and 122 of the valve 118. The jet housing 80 further includes
jet nozzles 150 each having an inlet orifice 152 in the second annular
surface 146 and extending through the ring 130 in a parallel, coaxial
direction away from the inlet assembly 36.
When the components are assembled as in FIG. 3 the jet housing
80 engages the collar 51. The baffle 110 of the plug 76 extends
through the opening in the annular ring 130 of the jet housing 80.
Moreover, the opening through the forward end of the annular ring
130 is at least coextensive with the recess 116 in the second cylindrical
body portion 86. The annular ring 118 of the jet valve 78 fits within
the third cylindrical body portion 140 of the jet housing 80 and
is maintained between the body portion 82 of the plug 76 and the
body portion 136 of the jet housing 80. The arms 120 and 122 of
the jet valve 78 extend through the openings 143 as best seen in
FIGS. 4 and 5. The openings 143 need not limit circumferential reciprocation
of the jet valve 78 this function being accomplished as stated
heretofore by interaction of the pin-limit stop 102 and channel
126. The orifices 152 of the jets 150 are in coaxial registry with
the outlet ports 94 of the first cylindrical body portion 82. Movement
of the jet valve 78 as described above, will thus be seen to provide
selective communication between the outlet ports 94 and the orifices
152. Thus, when the jet valve is in the previously-defined first
extreme position (FIG. 4), a first set of passages 153 is provided
for the flow of fluid between the cylinder 46 and a pair of jet
nozzles 150 in one side of the assembly. Similarly, when the jet
valve is in the previously-defined second extreme position (FIG.
5), a second set of passages 155 is provided for the flow of fluid
between the cylinder 46 and the pair of jet nozzles 150 in the other
side of the assembly. The pairing of the jets is important, as will
be more fully discussed hereinafter.
The gyroscopic apparatus 34 is similar to that disclosed in FIG.
1. Where appropriate, identical numbers are used to indicate the
respective similar parts and, for purposes of expediency, the description
of those similar parts is not reiterated here. Unlike the pressure
pad 28 of the gyroscopic apparatus 10 the pressure pad of the gyroscopic
apparatus 34 consists of four wings 154 one in each of the four
quadrants defined by the impeller 22 and axle 13 as best seen in
FIG. 6. Thus, the overall pressure pad is symmetrically mounted
with respect to the support axes. Each of the four wings is located
in front of one of the jet nozzles 150 of the jet housing 80 (FIGS.
2 and 3). The gyroscopic apparatus is allowed a predetermined degree
of oscillatory precessional rotation about the y support axis, defined
by the arc .theta., between the back-pressure outlets 43 of the
fluidic amplifier control unit 42 (FIGS. 2 and 6), as more fully
explained hereinafter. During operation of the apparatus, as a result
of the operation of the jet valve, only two of the four jets 150
of the jet housing 80 which are located on the same side of the
wheel, i.e., on the same side of the y-z plane, are discharging
fluid toward their respective pressure pad wings 154 at any given
time. Accordingly, a torque is continually being applied about a
support axis y of the gyroscopic apparatus thereby causing precession
of the gyroscopic apparatus about the other support axis z. However,
the torque and hence, the direction of precession are reversed automatically
at each end of the arc .theta..
To effect the aforementioned reversal, by actuation of the valve
78 a rod 156 is mounted on the annular ring 14 of the gyroscopic
apparatus 34 and has mounted on the end thereof a plate 158 sandwiched
between two pads 160 (FIGS. 2 6 and 7). The plate and pad arrangement
oscillates between the back-pressure outlets 43. When the plate
and pad arrangements abuts against one of the back-pressure outlets,
a fluidic signal is sent to the fluidic amplifier control unit 42
whereby the pin 128 is moved linearly thereby causing circumferential
movement of the jet valve 78. The pair of jets 150 then operating
is shut down and the other pair of jets is caused to discharge fluid
toward their respective pressure pad wings. The gyroscopic apparatus
thereupon precessionally rotates in the opposite direction toward
the other back-pressure outlet.
Because of the permitted excursion of the pressure pad wings of
the gyroscopic apparatus 34 the fluid which is intended to impinge
upon the wheel 22 must be directed against only the vanes 24 of
the wheel. It is to this end that the baffle 110 is provided. The
arcuate shape of the port 104 and of the baffle directs the fluid
such that it impinges directly upon the vanes (and only the vanes)
over the entire breadth of the gyroscopic apparatus' oscillation.
The relationship of the baffle and wheel is best seen in FIG. 3.
It will be seen that the recess 116 provided in the second cylindrical
body portion 86 enables appropriate positioning of the wheel 22
in alignment with the port 104. Moreover, such positioning of the
gyroscopic apparatus in front of the jet assembly provides for registry
of the jets 150 with the wings 154.
The outlet housing 162 of the outlet assembly 40 collects the metered
fluid and is of any appropriate configuration to be joined with
an outlet conduit as would be well known to one skilled in the art
and, therefore, not shown in detail herein. The outlet assembly
includes in a side wall 164 thereof a fluid impermeable, flexible
membrane 166 through which the rod 156 extends. The flexible membrane
166 allows oscillatory movement of the rod 156 relative to the housing
162 while maintaining the fluid-tight integrity of the system.
The amplifier control unit 42 may be of any suitable design and
mode of operation. A fluidic logic system operated by fluid pressure
taps from the system being metered is preferred to avoid external
power requirements and thereby to maintain a fully self-contained
and operated metering unit. The control unit illustrated schematically
in FIG. 7 meets these parameters. Inlets 300 310 and 312 receive
fluid under pressure from the main system through suitable tubing
connections (not shown). Inlet 300 communicates through choke orifices
314 and 316 with two manifold passages 318 and 320 to which are
connected tubes 322 and 324 communicating with the back-pressure
outlets 43a and 43b. Tubes 326 and 328 communicate with signal outlets
326a and 328a of the manifolds and with signal inlets 330a and 332a
of two pressure diaphragm operator units 330 and 332. Connecting
rod assemblies 334 and 336 connect the respective diaphragms 338
and 340 to conical valve pistons or diffusers 342 and 344 which
control the pressure connections between the inlets 310 312 and
with the respective ends of a piston chamber 346 in a cylinder 347.
Compression springs 348 and 350 bias these valves to their closed
positions. A reciprocable free piston 352 in the chamber 346 carries
and drives the pin 128 for positioning the jet valve 78 as described
above. A small exhaust port is provided from each end of the chamber
346 as by providing a small notch in the respective sliding seal
of piston 352 as indicated at 354 and 356. Exhaust ports are provided
for the diaphragm units, as at 358 and 360.
In the operation of the logic unit of FIG. 7 the pressure supplied
to each manifold 318 and 320 escapes through the respective outlet
nozzle 43a or 43b, and valves 342 and 344 are closed, until the
plate and pad 158 160 engages one of the back-pressure outlets
43. At the moment of contact, flow from the contacted back pressure
outlet 43a and 43b is decreased because of blockage. This causes
the internal pressure in the respective back-pressure outlet circuit
to increase to a value near to that available at the main pressure
inlet 300 which is substantially greater than that of atmospheric
pressure. This pressure signal is transmitted through the respective
connecting tubing 322 and 324 to the pressure signal outlet 326a
or 328a and hence to the diaphragm unit 330 or 332. This pressure
signal can be transmitted only by the pressure signal outlet which
is blocked, due to the choke orifice bypass valves 314 and 316.
This pressure signal causes a deflection of the respective pressure
diaphragm 338 or 340 due to the difference in pressure from the
pressure signal inlet 330a or 332a to the atmospheric pressure relief
tap 358 or 360. The deflection of the pressure diaphragm moves the
respective deflection rod assembly 334 or 336 and thereby opens
the respective high pressure inlet port 310 or 312. This establishes
a pressure differential from the pressure inlet port to the atmospheric
pressure at the opening for the pin 128 on the respective face of
the movable piston 346. The pressure of this differential pressure
generates a force sufficient to move the piston 346 along the piston
barrel 346 and hence linearly moves the pin 128. When the plate
and pad arrangement ceases to block the back-pressure outlet, the
pressure on the respective pressure diaphragm is released and the
respective return spring 350 seats the respective valve 342 or 344
thereby once again blocking the respective pressure inlet port.
With the high pressure port blocked, the unbalanced pressure on
the piston face is allowed to dissipate through the respective orifice
354 or 356. However, the piston 346 remains in its displaced position
until the opposite pressure diaphragm is deflected.
The use and operation of the embodiment of the mass rate flow meter
of this invention depicted in FIGS. 2 through 7 is believed to
be apparent from the foregoing, but will be summarized. The mass
rate flow meter 32 is inserted into a line through which the fluid
which is to be measured is flowing. The fluid enters the inlet assembly
port 56 passing through the passage 64 and out the outlet port 60
into the cylindrical housing 50. The fluid emerges at a controlled
rate from the cylinder 50 through the passages 72 into the interior
of the cylinder 46. The fluid exits the cylinder 46 through the
passage 108 and is directed by the baffle 110 to impinge upon the
vanes 24 of the wheel 22 of the gyroscopic apparatus 34. The wheel
is caused to rotate at a speed proportional to the velocity of the
flowing fluid. The fluid also selectively exits through the jets
150 to impinge upon the wings 154 of the pressure pad of the gyroscopic
apparatus 34. Initially, a first pair of jets on one side of the
plane defined by the wheel 22 are open and the other pair of jets
on the other side of the plane defined by the wheel 22 are closed.
In this manner, a torque proportional to the momentum of the flowing
fluid is applied upon the annular ring 14 about the minor gimbal
trunion 18 in a first direction. By gyroscopic principles, the gyroscopic
apparatus precessionally rotates until the plate and pad arrangement
158 and 160 engages one of the back-pressure outlets 43 e.g., nozzle
43a. A signal is thereby sent to the fluidic amplifier control unit
42. The fluidic amplifier control unit responds as previously described
and linearly moves the pin 128 thereby causing circumferential
movement of the jet valve 78. Such movement of the jet valve shuts
off the flow of air through the first pair of jets and opens the
flow of air through the second pair of jets. A torque is thus applied
to the annular ring 14 about the minor gimbal trunion in a second,
reverse direction, thereby causing precessional rotation of the
gyroscopic apparatus about the major gimbal trunion in an opposite
direction. The gyroscopic apparatus precessionally rotates in the
opposite direction until the plate and pad arrangement engages the
other back-pressure outlet 43b, at which point an opposite signal
is sent to the fluidic amplifier control unit and the pin 128 is
shifted linearly in the reverse direction. This causes the jet valve
78 to be moved circumferentially in the reverse direction, closing
the second jets and opening the first pair of jets and causing the
gyroscopic apparatus to again precess in the first direction, whereupon
the cycle is repeated. This controlled reversal or reciprocation
continues throughout the operation of the meter of FIGS. 2-7. The
fluid discharged by the jets and the baffle is collected by the
housing 162 of the outlet assembly 40 for redelivery to the line
in which the mass rate flow meter has been inserted. The oscillatory
movements of the gyroscopic apparatus can be counted or otherwise
monitored by any one of a variety of methods such as electrical,
fluidic or photoelectric sensing and/or registering devices which
are well known to those skilled in the sensing metering and measuring
arts and, therefore, are not described further herein. The rate
of occurrence of the reversals is a direct indication of the mass
rate of fluid flow, and the summation is a measure of the total
mass flow for the period of the summing.
The constant sequential reversing of the precessional torque force
and the concomitant reversing of the direction of application of
any frictional or drag forces avoid or overcome extraneous precessional
movement that may arise from such forces. For example, if the impeller
begins to precess about the y axis because of friction or read-out
transducer forces while the apparatus is precessing about the z
axis in one direction, any such movement about the y axis will be
reversed during the next oscillation reversal about the z axis.
Referring now to FIGS. 8 through 11 a second and presently preferred
embodiment of a mass flow meter 168 according to this invention
is shown. A gyroscopic apparatus 170 is mounted for unidirectional
precessional rotation at a rate directly and linearly proportional
to the mass flow rate of fluid passing through the flow meter 168.
In addition, the flow meter 168 includes an inlet housing 172 a
jet assembly 174 an intermediate housing 176 and an outlet housing
178.
The inlet housing 172 includes a cylindrical portion 180 and a
transitional frustoconical portion 182. The cylinder 180 is hollow
and forms open end 184. The end 184 comprises a threaded inlet port
190 (threaded either internally, FIG. 8 or externally, FIG. 9)
for connection to a suitably threaded conduit. The frustoconical
portion 182 also is hollow and forms the outwardly flaring open
inner end 194.
The jet assembly 174 includes a web plate 196 a generally cylindrically-shaped
insert 198 and a generally frustoconical insert 200. The web plate
196 includes an annular ring 202 a circular central portion 204
and radial arms 206 extending between the annular ring 202 and the
central portion 204. The generally cylindrically-shaped insert 198
is solid, having one flat end 208 and a second end portion 210 which
is recessed in a concave manner to define a dished surface 212.
The flat end 208 of the insert 198 is affixed to the central portion
204 of the web plate 196 by any suitable means, e.g., by cementing
(FIG. 8) or bolting (FIG. 9).
The generally frustoconically-shaped insert 200 is hollow and open
at both ends 214 and 216. An annular recess 218 is provided in the
interior wall 220 immediately adjacent the end 214 to receive the
web plate 196 against the resulting inner annular shoulder. The
web plate is mounted within the recess by any suitable means, e.g.,
by cementing (FIG. 8) or bolting (FIG. 9). The outer diameter of
the end portion 210 of insert 198 is slightly less than the inner
diameter of the end portion 216 of the insert 200. When the web
plate and insert 198 are mounted in insert 200 the end portion
210 extends into the portion 216 and the ends 210 and 216 define
a narrow annular nozzle aperture 222 (see FIGS. 9 and 11). The end
portions 210 and 216 include inner annular surfaces 224 and 226
(FIGS. 8 and 9) of appropriate configuration to form the annular
nozzle 222 thereby concentrating and directing the fluid jet discharged
therethrough.
The gyroscopic apparatus 170 (FIG. 10) is also similar to that
disclosed in FIG. 1. Accordingly, where appropriate, as with the
first embodiment, identical numbers are used to indicate the respective
similar parts and, for purposes of expediency, the description of
those similar parts is not reiterated here. The sensing rotor 12
comprises a sphere 228 including vanes 24 about the circumference
thereof. The spherical shape assures good distribution of the gas
flow about the rotating body. A groove or notch 30 is provided in
the center of the vanes 24 to stabilize the gyroscopic apparatus,
as set forth hereinbefore. Unlike the pressure pad 28 of the gyroscopic
apparatus 10 the pressure pad of the gyroscopic apparatus 170 consists
of a spherically-shaped deflection tongue 230 which cups the sphere
without touching it, and a mounting tab 232 asymmetrically mounted
with respect to the y support axis on the annular ring 14.
The gyroscopic apparatus 170 is allowed complete rotational freedom
about the z support axis. Accordingly, the construction of the jet
assembly 174 and gyroscopic apparatus 170 is such that fluid is
continually directed against the vanes 24 and the pressure pad 28
for all positions of revolution of the apparatus 170. It is to this
end that the annular jet 222 is provided. Fluid exiting the annular
jet will concomitantly impinge upon the vanes 24 of the sphere 228
and the deflection tongue 230 of the pressure pad for all such positions.
A guard or shroud 26 is mounted on the annular ring 14 to shield
the leeward sides 236 of the vanes 24 from impingement by the fluid
being discharged from the annular jet.
The intermediate housing 176 encases the jet assembly 174 and the
gyroscopic apparatus 170. This housing is held in abutting relation
to the inlet housing 172 by cementing (FIG. 8) or a bolting arrangement
(FIG. 9). An "O"-ring 238 is inserted in a recess 239
provided in the intermediate housing to provide a seal between these
housings.
The outlet housing 178 confines the metered fluid and is threaded
or otherwise adapted, as is housing 172 for attachment of an outlet
pipe to the outlet port 240. The outlet housing 178 is held in abutting
relation to the intermediate housing 176 by cementing (FIG. 8) or
a bolting arrangement (FIG. 9). An "O"-ring 244 is inserted
in a recess 245 to provide a seal at this joint. A read-out mechanism
242 (FIG. 9) is mounted on the outlet housing. This mechanism is
coupled to the gyroscope major gimbal trunion 20 to provide an indication
of the rate of precessional rotation and/or to totalize the number
of precessional rotations. The coupling can be accomplished magnetically
as illustrated in FIG. 9 or mechanically, or photoelectrically,
or by any suitable technique known in the art and, therefore, is
not shown in detail herein.
In use and operation, the mass rate flow meter 168 of FIGS. 8-11
is inserted into a line through which the fluid which is to be measured
is flowing by suitable connection to the housings 172 and 178. The
fluid enters the inlet housing 172 and passes into the jet assembly
174 through the web plate 196 and emerges as a uniform annular
jet from the annular nozzle 222. This jet impinges upon the vanes
24 of the sphere 228 and the deflection tongue 230 of the pressure
pad. In this manner, the sphere is caused to rotate at a speed proportional
to the velosity of the flowing fluid and a torque proportional to
the momentum of the flowing fluid is applied upon the annular ring
14 about the minor gimbal trunion 18. By gyroscopic principles,
the gyroscopic apparatus precessionally rotates about the major
gimbal trunion at a rate proportional to the mass rate of flow of
the fluid. The rotational movement of the gyroscopic apparatus is
monitored by the mechanism 242 or in any of a variety of methods
in the art, and serves as a direct measurement of the mass rate
of flow of fluid through the meter.
The details of the theory and reasons for useful and satisfactory
operation of the subject invention are not now fully known or appreciated.
Certain particular problems or parameters and solutions thereto
are discussed above. However, the following is an example of a possible
basic theoretical outline currently believed to be applicable to
the overall operation of the aforedescribed invention and may be
helpful to understanding, using and practicing the invention and
in developing further embodiments of the basic invention.
For a flow meter detector unit such as those disclosed herein,
it is hereinbefore stated that, essentially
where,
M.sub.f =mass rate of flow,
.OMEGA.=angular velocity of the major gimbal trunion, and
K=constant related to the design of the system and the conduit
in which installed.
In the following paragraphs, the derivation of this relationship
will be shown.
The fundamental equation for the motion of a gyroscope is:
where,
T=impressed torque constituting the precession couple as defined
above,
I=moment of inertia of the rotating parts,
.omega.=angular velocity of the rotor, and
.OMEGA.=angular velocity of precession.
The impressed torque also may be expressed as
where,
and,
.gamma.=specific weight of the fluid
P=dynamic pressure of the fluid impinging on the pressure pad
g=gravitational constant,
V.sub.j =fluid velocity before impacting the pressure pad,
A.sub.P =effective area of the pressure pad, and
r.sub.p =effective radius at which the fluid impact force acts
on the pressure pad.
Therefore,
Also,
where,
Vn=fluid velocity at the nozzle
r.sub.r =effective radius of the rotor
Substituting in equation (2),
Assuming that V.sub.j is approximately and effectively equal to
Vn, then equation (7) reduces to
(.gamma./2g)V.sub.j A.sub.p r.sub.p =(1/r.sub.r)I.OMEGA. (8)
which may be regrouped as
Further, assuming that the cross sectional area of the jet (A.sub.j)
effectively equals the effective area of the pressure pad (A.sub.p),
equation (9) becomes:
However,
where,
M.sub.f.sbsb.j =mass flow rate through the jet, and
.rho.=density of the fluid.
Grouping constants,
and substituting equations (11) and (12) into equation (10)
Thus, as set forth above, in the steady state operating condition,
the angular rotation of the major trunion 20 is proportional in
speed to the mass flow rate of fluid passing through the gyroscopic
apparatus 10.
It has been found that the illustrated embodiments will provide
linear response curves over various flow rates, generally as indicated
by the foregoing basic response equation.
Each of the gyro assemblies should be balanced both dynamically
and statically.
It will be apparent, particularly to those skilled in the art,
that gyroscopic apparatus and assemblies as disclosed herein may
be embodied in a wide variety of mass rate flow meter designs. The
unit may be entirely self-contained and is operable to provide a
local or remote read-out of the metered flow. Accurate measurements
may be obtained without necessitating complex and expensive correction
equipment, special totalization equipment, or external power sources.
Operational energy is derived from the flowing fluid. Further, the
gyroscopic apparatus may be of a simple design, and one which is
economical to fabricate as well as being reliable, sturdy and accurate
in use.
It will be seen that improvements have been provided in mass rate
flow meters which meet the objects of this invention.
While particular embodiments of this invention have been shown,
it will be understood, of course, that the invention is not limited
thereto since modifications may be made by those skilled in the
art, particularly in light of the foregoing teachings. Therefore,
it is contemplated by the appended claims to cover any such modifications
as incorporate those features which may be said to constitute the
essential features of these improvements within the true spirit
and scope of the invention.
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