Fluid flow regulation

Flow regulating apparatus comprises a turbulent-flow valve with a fluid supply connected at the upstream side thereof. A fixed pressure bias is applied to the fluid upstream of the valve whereby the mass flow rate of fluid through the valve is directly proportional to the pressure differential across the apparatus when these variations are within a selected pressure range. Such flow regulation may be used in a system for introducing a metered amount of liquid fuel into an air stream to provide a combustible air-fuel mixture having a substantially constant air-to-fuel ratio. With this system air is passed through a constricted zone to increase its velocity to sonic, and the area of the constricted zone is varied in correlation with operating demands imposed upon the engine for which the mixture is produced. A liquid fuel supply is under the influence of atmospheric pressure, and fuel is metered from the supply into the air stream by controlling a fuel valve of the turbulent-flow type in direct proportion to the area of the constricted zone, the fuel valve being exposed to the pressure of the air stream. The fixed pressure bias is applied to the liquid fuel supply so that the mass flow rate of fuel through the valve varies in direct proportion with variations in atmospheric pressure.

BACKGROUND OF THE INVENTION 
The present invention relates to fluid flow regulation, and also to method 
and apparatus for regulating the metering of liquid fuel as atmospheric 
pressure changes to thereby produce an air-fuel mixture having a 
substantially constant air-to-fuel ratio. 
U.S. Pat. No. 3,778,038, issued Dec. 11, 1973, describes a method and 
apparatus for producing a uniform combustible mixture of air and minute 
liquid fuel droplets for delivery to an internal combustion engine. The 
apparatus includes an intake air zone connected to a variable area 
constricted zone for constricting the flow of air to increase the velocity 
thereof to sonic. Liquid fuel is introduced into the air stream at or 
above the constricted zone to divide and uniformly entrain fuel as 
droplets in the air flowing through the constricted zone. Walls downstream 
of the constricted zone are arranged to provide an increasing 
cross-sectional area for efficiently converting a substantial portion of 
the kinetic energy of the high velocity air and fuel to static pressure. 
Through such conversion it is possible to maintain sonic velocity air flow 
through the constricted zone over substantially the entire operating range 
of the engine. 
The above U.S. patent further explains the well known phenomena that under 
sonic conditions, the pressure of the air at the constricted zone is 
approximately 53% of atmospheric pressure. Under sonic conditions and when 
the atmospheric pressure remains constant, it is possible to provide an 
air-liquid fuel mixture having a substantially constant air-to-fuel ratio 
by simply metering the amount of fuel delivered into the air stream in 
direct proportion to the area of the constricted zone. However, when 
atmospheric pressure varies, possibly due to altitude changes, the mass 
flow rate of air passing through the apparatus also varies. When this 
occurs it is necessary to adjust the amount of fuel introduced into the 
air stream in order to maintain a substantially constant air-to-fuel 
ratio. For example, when atmospheric pressure decreases, the air passing 
through the device has less mass density and less fuel is required to 
produce a mixture having the same air-to-fuel ratio as before the 
atmospheric change. A fuel metering system which relies solely upon the 
area of the constricted zone or the volume of air passing therethrough 
does not correct for such atmospheric fluctuations, and the air-to-fuel 
ratio varies depending upon varying atmospheric conditions. 
In order to accurately compensate for atmospheric pressure changes it is 
necessary that variations in the pressure differential across the fuel 
metering valve be accompanied by directly proportional variations in the 
mass flow rate of fuel through the valve. While laminar-flow metering 
valves meet such specifications, the mass flow rate of fuel through these 
valves is inversely dependent upon the kinematic viscosity of the liquid. 
For example, over a temperature range of 20.degree. to 100.degree. F., the 
kinematic viscosity of gasoline changes approximately by a factor of two 
which results in a system highly sensitive to fuel temperature. It is 
extremely difficult, if not impossible, or excessively expensive to 
compensate for such temperature dependence in producing a laminar-flow 
valve. Accordingly, even though the mass flow rate of fluid through a 
laminar-flow valve varies directly with the pressure differential across 
the valve, its inverse dependence on kinematic viscosity makes it totally 
unacceptable from the standpoint of corrective fuel metering for 
atmospheric pressure fluctuations. On the other hand, while turbulent-flow 
valves, such as needle valves, are not sensitive to the kinematic 
viscosity of liquids, the mass flow rate through such a valve does not 
vary directly with the pressure differential across the valve. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the present invention is to provide fluid flow 
regulation apparatus and method wherein the mass flow rate of fluid 
through a turbulent-flow valve varies directly with variations in the 
pressure differential across the apparatus when such changes are within a 
selected pressure range. 
Another object of the present invention is a simple and highly efficient 
method and apparatus that regulates fuel metering so that as atmospheric 
conditions change the air-to-fuel ratio of an air-fuel mixture remains 
substantially constant. 
In accordance with the present invention, flow regulating apparatus 
comprises a turbulent-flow valve with a fluid supply connected to the 
upstream side of the valve. A fixed pressure bias is applied to the fluid 
upstream of the valve so that the mass flow rate of fluid through the 
valve varies directly with variations in the pressure differential across 
the apparatus when these variations are within a selected pressure range. 
Moreover, in accordance with the present invention, method and apparatus 
are provided for producing a combustible air-liquid fuel mixture having a 
substantially constant air-to-fuel ratio over substantially the entire 
operating range of an engine to which the mixture is supplied. An air 
passageway includes a gradually converging air entrance zone, a variable 
area throat zone through which air and liquid fuel are passed at sonic 
velocity, and a gradually diverging downstream zone. A fuel supply is 
under the influence of atmospheric pressure, and fuel metering is provided 
for delivering a metered amount of fuel into the air stream flowing 
through the passageway at or above the throat zone. The fuel metering 
includes a valve exposed to the pressure of the air stream and connected 
to the fuel supply. A valve operator controls the rate of fuel delivered 
into the air stream in direct proportion to the area of the throat zone as 
the area of the throat zone is modulated. A fixed pressure bias is applied 
to the fuel supply whereby the mass flow rate through the valve varies 
directly with variations in atmospheric pressure to thereby adjust the 
liquid fuel metered in direct proportion to atmospheric pressure 
fluctuations so that the air-to-fuel ratio of the mixture is maintained 
substantially constant. 
Typically, the fuel metering valve is a needle valve, and the arrangement 
for applying the fixed pressure bias to the liquid upstream of the valve 
may include a connection from the intake mainfold to the fuel source of 
the supply with a pressure regulator in the connection. Alternatively, the 
fixed pressure bias may be applied to the liquid fuel at a location 
between the fuel source and the valve.

DETAILED DESCRIPTION OF THE INVENTION 
Referring in more particularity to the drawings, the present invention is 
best understood by initially referring to FIGS. 2A and 2B. FIG. 2A shows a 
typical orifice needle valve, and FIG. 2B is a plot of the mass flow rate 
(mass per unit time) of fluid flowing through the valve versus the 
pressure differential across the valve for three different valve settings. 
Other types of turbulent-flow valves have characteristics similar to FIG. 
2B with flow rate varying as a power of the pressure differential. As 
shown therein, the mass flow rate varies as the square root of pressure, 
and this valve is representative of turbulent-flow valves. The mass flow 
rate of fluid through the valve does not vary in direct proportion to the 
pressure differential across the valve, and it could not be utilized to 
accurately compensate fuel delivery in response to atmospheric pressure 
changes. However, in the present invention a fixed pressure bias is 
applied to the fluid upstream of the valve, and FIGS. 3A and 3B illustrate 
the characteristics of such an apparatus. By an appropriate choice of 
pressure bias, one can approximate a desired direct proportion relation 
between the mas flow rate of fluid passing through the valve and the 
pressure differential across the apparatus in a selected pressure range, 
and this relationship is shown in FIG. 3B as m/t = c.DELTA.P. Hence, over 
a selected pressure range the mass flow rate of the fluid varies directly 
with the pressure differential across the apparatus, as shown. In other 
words, regardless of the valve setting, when the pressure differential 
across the apparatus changes, the mass flow rate of fluid is adjusted in 
direct proportion to such changes. Once the varying pressure differential 
across the apparatus is determined, a fixed pressure bias is applied to 
the fluid entering the valve which provides a direct relationship between 
mass flow rate and pressure in the determined pressure range. 
While it is stated that the mass flow rate of fluid passing through the 
valve varies in direct proportion to the pressure differential across the 
apparatus of FIG. 3A, it should be noted that since the flow rate 
variations follow the curves of FIG. 3B, the direct relationship is only 
approximate. However, for all practical purposes, since the portions of 
the curves of FIG. 3B for the predetermined pressure range are 
substantially linear along lines passing through origin of the plot, the 
relationship between mass flow rate and pressure differential may be 
referred to as a direct proportion. 
When the pressure differential across the valve of FIG. 2A varies between 
point a and point b for the intermediate valve setting of FIG. 2B, the 
mass flow rate of fluid passing through the valve varies between point c 
and point d. However, the change in the mass flow rate from point c to 
point d varies as the square root of the pressure rather than directly. On 
the other hand, with the apparatus of FIG. 3A, when a fixed pressure bias 
is applied to the fluid upstream of the valve, the same variation in 
pressure differential across the apparatus between points a and b is 
accompanied by a directly proportional variation in the mass flow rate 
between points c' and d'. Through the selection of an appropriate fixed 
pressure bias the valve operates in a region where variations in pressure 
differential are accompanied by direct variations in the mass flow rate of 
fluid through the valve. 
FIG. 1 illustrates flow regulating apparatus 10 for delivering a metered 
amount of liquid fuel into an air stream. Generally, the air stream enters 
a mixing device 12 that includes a gradually converging air entrance 14 
connected to a variable area throat or constricted zone 16. A gradually 
diverging downstream zone 18 is connected to the throat zone, and the 
downstream zone is connected to an intake manifold 20. The area of the 
throat 16 is varied in accordance with operating demands upon the engine 
to which the device 12 is attached. The air stream enters at 14 and is 
accelerated to sonic velocity at the throat zone 16. Also, the kinetic 
energy of the high velocity air is efficiently converted to static 
pressure as the air flows through the diverging downstream zone 18. Such 
efficient conversion of kinetic energy to static pressure enables sonic 
flow to exist at the throat zone 16 over substantially the entire range of 
intake manifold conditions. 
The flow regulating apparatus 10 also has a liquid fuel supply 22 including 
a fuel source 23 under the influence of atmospheric pressure P.sub.o, and 
as shown in FIG. 1, the fuel source may be in the form of a float bowl. 
The supply 22 also includes a fuel line 24 connecting the source 23 to a 
needle valve 26 arranged to meter fuel, as explained below. The downstream 
end of the valve 26 is connected to the device 12 upstream of the throat 
zone 16 by line 27. Alternatively, the line 27 may be connected to the 
device 12 at the throat zone 16, if desired. The valve 26 is opened and 
closed in direct proportion to the cross-sectional area of the throat zone 
16, and a motivator 28 connected between the device 12 and the valve opens 
and closes the valve directly with respect to the cross-sectional area of 
the throat zone as that area is modulated in response to engine demands. 
A fixed pressure bias P.sub.B is applied to the liquid fuel upstream of the 
valve 26. The bias causes the valve 26 to operate in a region where the 
mass flow rate of fuel varies directly with variations in the pressure 
differential between atmosphere and the pressure at the fuel introduction 
point in the device 12 when these variations are within a selected 
pressure range. Such valve operation is utilized to compensate the amount 
of fuel delivered in direct proportion to atmospheric pressure variations. 
The arrangement for applying the fixed pressure bias may include a line 30 
extending from the intake manifold 20 to the fuel source 23 with a 
pressure regulator 32 in the line. 
The pressure regulator 32 is referenced to atmospheric pressure by a vent 
34, and as shown in FIG. 1, the back of the diaphragm 36 of the regulator 
is at atmospheric pressure. The fixed pressure bias P.sub.B may be 
adjusted by changing the tension on spring 38 through manipulation of the 
knob 40, as is well known. The regulator sets the air pressure in the 
float bowl 23 at P.sub.o -P.sub.B, the pressure bias P.sub.B being fixed 
and independent of P.sub.o. Hence, when the diaphragm 36 is in equiibrium 
each side thereof is acted upon by atmospheric pressure minus the pressure 
bias provided by the upward force of the spring 38. Since the lower half 
of the regulator is connected to the fuel source by a portion of line 30, 
the pressure above the fuel in the bowl 23 is equal to pressure in the 
lower half of the regulator which in turn is equal to atmospheric pressure 
minus the pressure bias. 
The air entrance zone 14 is designed so that the cross-sectional area 
thereof varies directly with the cross-sectional area of the throat. This 
is accomplished by providing a pair of opposite spaced apart walls 42, 44 
mounted for relative movement toward and away from one another to vary the 
area of the throat zone 16. The walls are flat and parallel to one another 
at least in the air entrance zone 14. As shown in the drawing, wall 42 
moves toward and away from stationary wall 44 to modulate the area of the 
throat. Wall 34 may be coupled to the throttle pedal of the engine to 
which device 12 is attached for direct movement therewith in response to 
operating demands imposed upon the engine. This wall arrangement also 
varies the area of the air entrance zone but such variation is directly 
related to the area of the throat. Hence, the pressure at the point of 
introduction of the fuel into the air intake zone 14 bears a predictable 
relationship to the pressure at the throat. As noted above, under sonic 
conditions, the pressure at the throat 16 is always approximately 53% of 
atmospheric pressure. Since the area ratio of the air entrance zone 14 to 
the throat zone 16 is constant, the pressure at the fuel introduction 
point in the entrance zone 16 will always be the same percentage of 
atmospheric pressure, and changes in atmospheric conditions are 
automatically reflected in the pressure at the fuel introduction location. 
It is desirable that the point of introduction of fuel into the air 
entrance zone 14 be located so that the pressure at that point is about 29 
inches Hg., when the atmospheric pressure is 30 inches Hg. This provides a 
desirable pressure for metering fuel into the air stream flowing through 
the device 12, and the pressure at the fuel introduction point will always 
be 29/30 of atmospheric pressure. 
In operation, air enters the device 12 at atmospheric pressure, for example 
30 inches Hg., and is accelerated to sonic velocity at the throat 16 by 
the action of the engine which functions as a downstream pump. The amount 
of air flowing through the device is governed by the location of the 
movable wall 42 which may be connected for movement with the throttle 
pedal. As the throat area is increased, for example, the motivator 28 
directly increases the opening of the needle valve 26 which allows 
additional fuel to enter into the increased air stream. The differential 
between the pressure acting upon the fuel source 23 (P.sub.o -P.sub.B) and 
the pressure at the point of introduction of the fuel into the device 12 
(about 29 inches Hg.) causes fuel to flow through the valve 26. With a 
fixed pressure bias P.sub.B of 0.5 inches Hg., the pressure of the fuel 
upstream of the valve is P.sub.o -P.sub.B or 29.5 inches Hg. and the 
downstream pressure is 29.0 inches Hg. The pressure differential across 
the valve is 0.5 inches Hg. Any change in atmospheric pressure is 
accompanied by a direct change in pressure at the point of introduction of 
the fuel into the device 12, as explained above. This results in a change 
in the pressure differential across the needle valve and an adjustment of 
the fuel flowing through the line 27 into the device 12. For example, if 
the atmospheric pressure drops to 24.0 inches Hg., the pressure of the 
fuel upstream of the valve (P.sub.o -P.sub.B) becomes 24.0 inches Hg.-0.5 
inches Hg. or 23.5 inches Hg. The downstream pressure being 29/30 P.sub.o 
drops to 23.2 inches Hg., and the pressure differential across the valve 
is 23.5 inches Hg.-23.2 inches Hg. or 0.3 inches Hg. With the fixed 
pressure bias P.sub.B applied to the liquid upstream from the needle valve 
26, the change in pressure differential across the valve from 0.5 inches 
Hg. to 0.3 inches Hg. is accompanied by a direct change of the mass flow 
rate of fuel through the valve which properly compensates the fuel 
metering for the decrease in atmospheric pressure. In other words, the 
mass flow rate of liquid through the valve varies directly with variations 
in the pressure differential across the valve so that the air-to-fuel 
ratio of the mixture produced remains constant. 
FIGS. 2B and 3B graphically illustrate the results of the applied fixed 
pressure bias of the present invention. Utilizing the same representative 
examples expressed above, the pressure differential across the valve of 
FIG. 2A becomes 30 inches Hg.-29.0 inches, Hg. or 1.0 inches Hg., and this 
pressure differential is shown in FIG. 2B as point e. When the atmospheric 
pressure drops to 24.0 inches Hg., the pressure differential across the 
valve of FIG. 2A drops to 0.8 inch Hg. (24 inches Hg.-29/30 24 inches 
Hg.), and the pressure variation from 1.0 inch Hg. to 0.8 inch Hg. is 
accompanied by a drop in the mass flow rate of the fuel which is not 
directly proportional thereto. On the other hand, when a fixed pressure 
bias P.sub.B of 0.5 inch Hg. is applied to the fuel upstream from the 
valve, a change in pressure differential from 1.0 inch Hg. to 0.8 inch Hg. 
between the atmospheric pressure and the pressure at the fuel introduction 
points is accompanied by a directly proportional change in the mass flow 
rates of fuel through the valve. Point e in FIG. 3B represents a pressure 
differential of 1.0 inch Hg. between the atmosphere and the fuel 
introduction point, and as clearly shown, a slight change in this 
differential in either direction is accompanied by a directly proportional 
change in the mass flow rate of fuel due to the applied fixed pressure 
bias P.sub.B. 
Another important aspect of the present invention is that the pressure bias 
P.sub.B is independent of the valve parameters of the needle valve 26 and 
is therefore substantially independent of the valve setting. Hence, fluid 
flow regulation for all settings of the valve is obtained with a single 
fixed pressure bias. Also, the fixed pressure bias P.sub.B may be applied 
between the fuel source 23 and the valve 26 rather than upstream from the 
source, if desired. 
FIG. 4 illustrates another fluid flow apparatus 50, according to the 
present invention. Fluid flows through an appropriate conduit 52 from an 
upstream source (not shown) to a turbulent-flow valve 54 in the form of a 
needle valve. As is well known, shifting movement of the needle 56 
relative to the orifice 58 changes the free cross-sectional area of the 
valve to thereby change the fluid flow rate. Immediately upstream from the 
valve 54 a pressure regulator 60 is positioned in the line 52. The 
pressure regulator is referenced to the upstream pressure P of the fluid 
flowing to the regulator by a line 62 connecting the upstream fluid to the 
back of the diaphragm 64. 
The pressure regulator 60 functions to apply a fixed pressure bias P.sub.B 
to the fluid upstream of the needle valve 54. As explained above, the 
application of a fixed pressure bias enables the mass flow rate of fluid 
passing through the valve 54 to vary directly with variations in pressure 
differential P-P.sub.2 when these changes are within a selected pressure 
range. The fixed pressure bias may be adjusted to a desired value by 
changing the tension on spring 66 through mainpulation of the operator 
knob 68. Once the operating range of pressure drop across the valve 54 is 
determined, an appropriate fixed pressure bias P.sub.B is selected to 
provide a direct proportional relationship between pressure differential 
and mass flow rate within the operating range. 
When the diaphragm 64 of the pressure regulator 60 is in equilibrium each 
side thereof is acted upon by the positive pressure P of the fluid minus 
the pressure bias P.sub.B provided by the upward force of the spring 66. 
Since the lower half of the regulator 60 forms part of the fluid conduit 
52, the pressure P.sub.1 on the fluid immediately upstream of the valve 54 
is equal to the pressure in the lower half of the regulator which in turn 
is equal to the pressure P of the fluid upstream of the regulator minus 
the pressure bias P.sub.B.