Abstrict A turbine flow meter used as a vapor flow meter in a vapor recovery-equipped
fuel dispenser. The turbine flow meter measures the vapor recovered
by the fuel dispenser during a fueling operation that is returned
back to the underground storage tank. The turbine flow meter measurements
may be ignored when fuel is no longer flowing through the fuel dispenser
since the turbine rotors in the turbine flow meter may continue
to rotate even after vapor is no longer being recovered.
Claims What is claimed is:
1. A vapor recovery-equipped fuel dispenser that dispenses fuel
from a storage tank to a vehicle and recovers vapor from the vehicle
during refueling, comprising: a fuel conduit that carries the fuel
from the storage tank; a vapor return line that carries the vapor
from the vehicle back to the storage tank; a hose and nozzle combination
fluidly coupled to said fuel conduit and said vapor return line
wherein said hose and nozzle receives the fuel and delivers the
fuel to the vehicle, and wherein said hose and nozzle receives the
vapor recovered from the vehicle to return to said vapor return
line; a fuel flow control valve located inline to said fuel conduit,
wherein a control system controls the opening and closing of said
fuel flow control valve to control fuel flow through said fuel conduit;
a fuel meter located inline to said fuel conduit that measures the
amount of fuel received from the storage tank, and communicates
a fuel flow signal to said control system; and a turbine vapor flow
meter located inline to said vapor return line that measures the
amount of recovered vapor, and communicates a vapor flow signal
to said control system; said control system adapted to ignore said
vapor flow signal when said fuel is no longer being dispensed to
the vehicle.
2. The fuel dispenser of claim 1 wherein said control system ignores
said vapor flow signal when said fuel flow signal is no longer received
by said control system.
3. The fuel dispenser of claim 2 wherein said fuel flow signal
is a pulse stream and said control system converts said pulse stream
into a volume.
4. The fuel dispenser of claim 1 wherein said control system generates
a fuel flow control valve signal that controls the opening and closing
of said fuel flow control valve, wherein said control system ignores
said vapor flow signal when said fuel flow control valve signal
indicates closing said fuel flow control valve.
5. The fuel dispenser of claim 4 wherein said fuel flow control
valve is a proportional flow control valve.
6. The fuel dispenser of claim 1 wherein a second control system
generates a vapor pump signal that controls a vapor pump located
inline to said vapor return line that generates a vacuum inside
said vapor return line, wherein said control system ignores said
vapor flow signal when said vapor pump signal indicates closing
said fuel flow control valve.
7. The fuel dispenser of claim 6 wherein said control system and
said second control system are the same control system.
8. The fuel dispenser of claim 6 wherein said vapor pump is a
variable speed vapor pump, and wherein said vapor pump signal is
a signal proportional to the speed of said vapor pump, wherein said
control system ignores said vapor flow signal based on the speed
of said vapor pump passing below a threshold value.
9. The fuel dispenser of claim 1 wherein said fuel flow meter
is a turbine fuel flow meter and flow switch wherein said flow switch
indicates when fuel is no longer flowing through said turbine fuel
flow meter, and wherein said control system ignores said vapor flow
signal when said flow switch indicates fuel is not longer flowing
through said turbine fuel flow meter.
10. The fuel dispenser of claim 1 wherein said hose and nozzle
combination contains a vapor valve communicatively coupled to said
control system wherein said vapor valve opens to allow recovered
vapor to enter said hose and vapor return line when fuel is delivered,
and wherein said control system ignores said vapor flow signal when
said vapor valve is closed.
11. The fuel dispenser of claim 1 wherein said vapor return line
contains a vapor valve communicatively coupled to said control system
wherein said vapor valve opens to allow recovered vapor to enter
said vapor return line when fuel is delivered, and wherein said
control system ignores said vapor flow signal when said vapor valve
is closed.
12. The fuel dispenser of claim 2 wherein said control system
uses said fuel flow signal to determine the volume of fuel delivered
to the vehicle, and said control system uses said vapor flow signal
to determine the volume of vapor recovered from the vehicle during
refueling.
13. The fuel dispenser of claim 12 wherein said control system
calculates a vapor to fuel ratio by dividing said volume of vapor
recovered by said volume of fuel delivered.
14. The fuel dispenser of claim 13 wherein said control system
communicates said vapor to fuel ratio to a system in the group consisting
of a site controller, a tank monitor, and a remote system.
15. A method for measuring the amount of vapor recovered by a vapor
recovery-equipped fuel dispenser during refueling of a vehicle,
comprising the steps of: receiving a fuel flow signal from a fuel
meter that measures the amount of fuel dispensed to the vehicle;
receiving a vapor flow signal from a turbine vapor flow meter that
measures the amount of vapor recovered during refueling of the vehicle;
and ignoring said vapor flow signal when fuel is no longer being
dispensed to the vehicle.
16. The method of claim 15 further comprising the step of converting
said vapor flow signal into a volume of vapor recovered.
17. The method of claim 15 wherein said step of ignoring comprises
ignoring said vapor flow signal when said fuel flow signal is no
longer received.
18. The method of claim 17 further comprising the step of converting
said fuel flow signal into the fuel volume.
19. The method of claim 15 further comprising the steps of: controlling
the fuel flow using a fuel flow control valve; and generating a
fuel flow control valve signal that controls the opening and closing
of said fuel flow control valve; wherein said step of ignoring comprises
ignoring said vapor flow signal when said fuel flow control valve
signal indicates closing said fuel flow control valve.
20. The method of claim 15 further comprising the steps of: controlling
the amount of vapor recovered using a vapor pump; and generating
a vapor pump signal that controls said vapor pump; wherein said
step of ignoring comprises ignoring said vapor flow signal based
on said vapor pump signal indicating that said vapor pump is deactivated.
21. The method of claim 20 further comprising the step of: adjusting
the speed of said vapor pump using a vapor pump signal; wherein
said step of ignoring comprises ignoring said vapor flow signal
based on the speed of said vapor pump passing below a threshold
value.
22. The method of claim 15 further comprising the step of: indicating
when fuel is no longer flowing through said fuel flow meter using
a flow switch; wherein said step of ignoring comprises ignoring
said vapor flow signal when said flow switch indicates when fuel
is no longer flowing through said turbine fuel flow meter.
23. The method of claim 15 further comprising the step of: controlling
the amount of vapor recovered using a vapor valve; wherein said
step of ignoring comprises ignoring said vapor flow signal when
said vapor valve is closed.
24. The method of claim 15 further comprising the steps of: determining
the volume of fuel delivered to the vehicle using said fuel flow
signal; and determining the volume of vapor recovered from the vehicle
during refueling using said vapor flow signal.
25. The method of claim 24 further comprising the step of calculating
a vapor to fuel ratio by dividing said volume of vapor recovered
by said volume of fuel delivered.
26. The method of claim 25 further comprising the step of communicating
said vapor to fuel ratio to a control system in the group consisting
of a site controller, a tank monitor, and a remote system.
Description FIELD OF THE INVENTION
The present invention relates to a device, system, and method of
using a turbine flow meter to measure recovered vapor in a vapor
recovery-equipped fuel dispenser.
BACKGROUND OF THE INVENTION
Many fuel dispensers in a service station environment are now equipped
with vapor recovery in order to meet governmental regulations. As
fuel is being dispensed into a vehicle fuel tank, vapors that are
present in the vehicle fuel tank exit out of the vehicle's fuel
tank fill neck. Vapor recovery-equipped fuel dispensers are designed
to recover all or substantially all of the vapor that would otherwise
escape into the atmosphere at the fuel tank fill neck. The nozzle
and hose on the fuel dispenser are specially equipped with a vapor
return path wherein vapors that exit the fuel tank fill neck during
refueling enter into the nozzle and hose and are returned back to
the underground storage tank. If the nozzle is not sealed with the
vehicle fuel tank fill neck during refueling, an assisted system
may be used wherein a vacuum is created in the vapor return line
to draw vapors into the vapor return line. An example of such an
assist vapor recovery system is described in U.S. Pat. No. 5040577
entitled "Vapor recovery system for fuel dispenser," now
Reissue Pat. No. RE35238. An example of a non-assisted vapor recovery
system wherein a seal is created between the vapor return path in
the nozzle and the vehicle fuel tank filler neck is illustrated
in U.S. Pat. No. 5636667 entitled "Conversion of fuel dispensers
to provide for vacuum assisted vapor recovery." This system
is commonly referred to as a "balance system."
There are several reasons why a vapor flow meter may be desired
in a vapor recovery-equipped fuel dispenser. When vapor recovery-equipped
fuel dispensers were first introduced into the marketplace, there
was no method of determining whether vapor was actually being recovered.
For example, in an assisted system, the vapor pump that creates
a vacuum in the vapor return line may be inoperable or not operating
properly. In an unassisted system, such as the balance system, the
vapor return line may contain a leak such that recovered vapors
escape through the leak before reaching the underground storage
tank. Fuel dispenser manufacturers have contemplated placing a vapor
flow meter in the vapor return line of fuel dispensers in order
to measure recovered vapor as one method of verifying that vapors
are actually being recovered and returned to the underground storage
tank. If the vapor flow meter registers a vapor flow, then vapors
are being recovered. The fuel dispenser can analyze the amount of
vapor recovered, as measured by the vapor flow meter, to determine
if the anticipated amount of vapor is being recovered in relation
to the flow rate of fuel being dispensed since vapors are pushed
out of the vehicle fuel tank filler neck at a rate proportional
to the fuel flow rate being placed inside the vehicle fuel tank.
One example of a vapor flow meter incorporated into an assisted
vapor recovery-equipped fuel dispenser is described in U.S. Pat.
No. 6347649 entitled "Pressure sensor for a vapor recovery
system." In this system, the recovered vapor enters into the
vapor return line and enters into a vapor flow meter inline to the
vapor return line. The vapor measurements measured by the vapor
flow meter are communicated to a control system. The control system
verifies that vapors are being recovered when expected using the
measurements received from the vapor flow meter. Also, if it is
desired to calculate the vapor-to-liquid (V/L) ratio of the fuel
dispenser, which is used to determine the fuel dispenser's vapor
recovery efficiency, a vapor flow meter is needed to measure the
amount of vapor being recovered for the "V" value in the
"V/L" ratio calculation.
Any number of different types of meters may be used to provide
the vapor flow meter. Some meters are inferential meters, meaning
that the actual displacement of the liquid or gaseous material is
not measured. An inferential meter uses some other characteristic
other than actual displacement to measure flow rate or volume of
recovered vapor. Inferential meters sometimes have advantages over
positive displacement meters, including smaller size. One example
of an inferential meter that may be used as a vapor flow meter is
known as a turbine flow meter, like that described in U.S. Pat.
No. 5689071 entitled "Wide range, high accuracy flow meter."
The turbine flow meter described in this patent measures the flow
rate of a fluid or gaseous material by determining the number of
rotations of a turbine rotor located inside the flow path of the
meter.
As vapor enters the inlet port of the turbine flow meter in the
aforementioned '071 patent, the vapor passes across two turbine
rotors inside the meter's housing. The vapor causes the turbine
rotors to rotate. The rotational velocity of the turbine rotors
is sensed by pick-off coils. The pick-off coils are excited by an
a-c signal that produces a magnetic field. As the turbine rotor
rotates, the vanes on the turbine rotors pass through the magnetic
field generated by the pick-off coils thereby superimposing a pulse
on the carrier waveform of the pick-off coils. The superimposed
pulses occur at a repetition rate (pulses per second) proportional
to the rotors velocity and hence proportional to the measured rate
of vapor flow.
However, a problem occurs when using a turbine vapor flow meter
such as the one described in the aforementioned '071 patent. When
the fuel dispenser nozzle is disengaged and fuel is no longer flowing
into the vehicle fuel tank, vapor is no longer being pushed out
of the vehicle fuel tank and into the vapor return line. However,
the previous rotational momentum of the turbine rotors inside the
turbine flow meter causes the turbine rotors to continue to rotate
even after vapor is no longer flowing into the vapor return line.
This causes the turbine vapor flow meter to continue generating
measurement signals as if vapor was still flowing since the turbine
rotors continue to rotate for a certain amount of time after vapor
flow stops. The control system that receives the measurement signals
from the pick-off coils of the turbine flow meter continues to register
vapor flow falsely.
A solution to the aforementioned problem must be found in order
to use a turbine flow meter as an accurate vapor flow meter in a
vapor recovery-equipped fuel dispenser. The present invention provides
a solution to this problem.
SUMMARY OF THE INVENTION
The present invention relates to a turbine flow meter used as a
vapor flow meter in a vapor recovery-equipped fuel dispenser. The
vapor flow meter measures that amount of vapor recovered by the
fuel dispenser and thereafter returned to the underground storage
tank during a fueling operation. It may be desireable to measure
the amount of vapor returned to the underground storage tank as
an indication that the vapor recovery system in the fuel dispenser
is properly operating, a leak is not present in the vapor return
path, and/or calculation of the vapor-to-liquid (V/L) ratio of the
fuel dispenser for performance monitoring and/or measurement.
The turbine flow meter is used as the vapor flow meter. The turbine
flow meter is an inferential meter that is small in size and highly
accurate. The turbine flow meter contains one or more turbine rotors
on a shaft inside the turbine flow meter. As vapor passes through
the turbine flow meter, the vapor causes the turbine rotor(s) to
rotate. The turbine rotor(s) contains a plurality of vanes made
out of a magnetic material. A pick-off coil is placed on the meter
in close proximity to the turbine rotor(s). The pick-off coil generates
an a-c carrier signal that generates a magnetic field around the
vanes of the turbine rotor(s). As the turbine rotor(s) rotates,
the vanes superimpose a pulse signal on the pick-off coil carrier
signal that is detected by the pick-off coil. The pick-off coil
communicates the carrier signal with pulses superimposed to a control
system inside the fuel dispenser. The pulses are counted to determine
the rotational speed of the turbine rotor(s) and thereby to determine
the vapor flow rate.
Because the turbine rotor(s) may continue to rotate due to their
rotational momentum for some period of time after vapor discontinues
flowing through the turbine flow meter, the pulse-encoded carrier
signal from the pick-off coil continues to indicate pulses even
after vapor recovery has stopped thereby yielding an inaccurate
measurement. The present invention involves determining when fuel
flow is inactive and has stopped as an indication of when to ignore
the pulses on the carrier signal from the pick-off coil. When fuel
is no longer flowing, vapor is not being recovered and returned
through the vapor flow meter since vapor is only pushed out of the
vehicle fuel tank when fuel is being delivered to the vehicle fuel
tank.
There are several different techniques to determine when fuel is
no longer flowing in a fuel dispenser. In one embodiment, the control
system that determines when to ignore the pulses on the vapor flow
meter carrier signal uses the pulse stream from the fuel flow meter
as an indication that fuel is either flowing or is not flowing.
In another embodiment, the control system that determines when
to ignore the pulses on the vapor flow meter carrier signal uses
a signal from a flow switch located on the outlet side of the fuel
flow meter as an indication that fuel is either flowing or is not
flowing. The flow switch generates a signal that indicates whether
fuel is flowing or not flowing.
In another embodiment, the control system that determines when
to ignore the pulses on the vapor flow meter carrier signal uses
a signal that controls the fuel flow control valve located in the
fuel flow path. The fuel flow control valve is opened when fuel
is allowed to flow, and is closed when fuel is not allowed to flow.
The fuel flow control valve signal status indicates whether fuel
is flowing or not flowing.
In another embodiment, the control system that determines when
to ignore the pulses on the vapor flow meter carrier signal uses
a signal that controls the vapor pump for vapor recovery. The vapor
pump is activated when vapor is to be recovered, and is deactivated
when vapor recovery is no longer required. The vapor pump is activated
when fuel flow is allowed and/or begins. Therefore, the vapor pump
signal status indicates whether fuel is flowing or not flowing.
In another embodiment, the control system that determines when
to ignore the pulses on the vapor flow meter carrier signal uses
a signal that controls the vapor valve inline to the vapor return
line. The vapor valve is open when vapor is to be recovered, and
is closed when vapor recovery is not required. The vapor valve is
opened when fuel flow is allowed and/or begins. Therefore, the vapor
valve signal status indicates whether fuel is flowing or not flowing.
Those skilled in the art will appreciate the scope of the present
invention and realize additional aspects thereof after reading the
following detailed description of the preferred embodiments in association
with the accompanying drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawing figures incorporated in and forming a
part of this specification illustrate several aspects of the invention,
and together with the description serve to explain the principles
of the invention.
FIG. 1 illustrates a typical service station environment in the
prior art;
FIG. 2 illustrates a fuel dispenser according to an embodiment
the present invention;
FIG. 3 is a schematic diagram of a turbine vapor flow meter that
may be used as the vapor flow meter according to the present invention;
FIG. 4 illustrates an embodiment of a fuel dispenser internal component
diagram illustrating the communication and interrelation of fuel
dispenser components of the present invention; and
FIG. 5 is a flow chart illustrating the operation of one embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments set forth below represent the necessary information
to enable those skilled in the art to practice the invention and
illustrate the best mode of practicing the invention. Upon reading
the following description in light of the accompanying drawing figures,
those skilled in the art will understand the concepts of the invention
and will recognize applications of these concepts not particularly
addressed herein. It should be understood that these concepts and
applications fall within the scope of the disclosure and the accompanying
claims.
Fueling environments come in many different designs. Before describing
the particular aspects of the present invention (which begins at
the description of FIG. 2), a brief description of a fueling environment
follows. A conventional exemplary fueling environment 10 is illustrated
in FIG. 1. Such a fueling environment 10 may comprise a central
building 12 a car wash 14 and a plurality of fueling islands 16.
The central building 12 need not be centrally located within the
fueling environment 10 but rather is the focus of the fueling environment
10 and may house a convenience store 18 and/or a quick serve restaurant
20 therein. Both the convenience store 18 and the quick serve restaurant
20 may include a point-of-sale (POS) 22 24 respectively. The central
building 12 may further house a site controller (SC) 26 which in
an exemplary embodiment may be the G-SITE.RTM. sold by Gilbarco
Inc. of Greensboro, N.C. The site controller 26 may control the
authorization of fueling transactions and other conventional activities
as is well understood. The site controller 26 may be incorporated
into a POS, such as POS 22 if needed or desired. Further, the site
controller 26 may have an off-site communication link 28 allowing
communication with a remote location for credit/debit card authorization,
content provision, reporting purposes or the like, as needed or
desired. The off-site communication link 28 may be routed through
the Public Switched Telephone Network (PSTN), the Internet, both,
or the like, as needed or desired.
The car wash 14 may have a POS 29 associated therewith that communicates
with the site controller 26 for inventory and/or sales purposes.
The car wash 14 alternatively may be a standalone unit. Note that
the car wash 14 the convenience store 18 and the quick serve restaurant
20 are all optional and need not be present in a given fueling environment.
The fueling islands 16 may have one or more fuel dispensers 30
positioned thereon. The fuel dispensers 30 may be, for example,
the ECLIPSE.RTM. or ENCORE.RTM. sold by Gilbarco Inc. of Greensboro,
N.C. The fuel dispensers 30 are in electronic communication with
the site controller 26 through a LAN or the like.
The fueling environment 10 also has one or more underground storage
tanks 34 adapted to hold fuel therein. As such, the underground
storage tank 34 may be a double-walled tank. Further, each underground
storage tank 34 may include a tank monitor (TM) 36 associated therewith.
The tank monitors 36 may communicate with the fuel dispensers 30
(either through the site controller 26 or directly, as needed or
desired) to determine amounts of fuel dispensed and compare fuel
dispensed to current levels of fuel within the underground storage
tanks 34 to determine if the underground storage tanks 34 are leaking.
The tank monitor 36 may communicate with the site controller 26
and further may have an off-site communication link 38 for leak
detection reporting, inventory reporting, or the like. Much like
the off-site communication link 28 off-site communication link
38 may be through the PSTN, the Internet, both, or the like. If
the off-site communication link 28 is present, the off-site communication
link 38 need not be present and vice versa, although both links
may be present if needed or desired. As used herein, the tank monitor
36 and the site controller 26 are site communicators to the extent
that they allow off site communication and report site data to a
remote location.
Now turning to the aspects of the present invention in providing
an accurate turbine flow meter as a vapor flow meter, a typical
fuel dispenser 30 in a service station environment according to
one embodiment of the present invention is illustrated in FIG. 2.
Fuel 44 from the underground storage tank 34 is fluidly coupled
to a fuel dispenser 30 via a fuel supply conduit 50. A submersible
turbine pump (not shown) creates a negative pressure inside the
fuel supply conduit 50 to draw the fuel 44 up into the body of the
fuel dispenser 30. Whenever fuel 44 is to be dispensed, a control
system 52 in the fuel dispenser 30 causes a flow control valve 54
inline to the fuel supply conduit 50 to open to allow fuel 44 to
flow past the flow control valve 54 upward and through a fuel meter
56. The control system 52 may be any type of electronics, micro-controller,
or micro-processor.
The fuel meter 56 measures the amount of fuel 44 flowing through
the fuel supply conduit 50. The fuel 44 goes up to the top of the
fuel dispenser 30 in a canopy area 58. Thereafter, the fuel 44 enters
into a hose 60 and onward to a nozzle 62 and out of the spout 64
of the nozzle 62 until the fuel 44 reaches a vehicle fuel tank 72
inside a vehicle 70 being refueled.
For further information on how elements of a fueling environment
10 may interact, reference is made to U.S. Pat. No. 5956259 which
is hereby incorporated by reference in its entirety. Information
about fuel dispensers may be found in commonly owned U.S. Pat. Nos.
5734851 and 6052629 which are hereby incorporated by reference
in their entireties. An exemplary tank monitor 36 is the TLS-350R
manufactured and sold by Veeder-Root. For more information about
tank monitors 36 and their operation, reference is made to U.S.
Pat. Nos. 5423457; 5400253; 5319545; and 4977528 which
are hereby incorporated by reference in their entireties.
Before describing the particular aspects of the vapor flow meter
of the present invention, a general description of a vapor recovery-equipped
fuel dispenser follows.
A typical vapor recovery-equipped fuel dispenser 30 is illustrated
in FIG. 2. As fuel 44 is delivered into the vehicle fuel tank 72
vapor 78 present in the fuel tank 72 is pushed outward through a
vehicle fuel tank filler neck 73 in an equal volume exchange since
the only escape path for the vapor 78 is the vehicle fuel tank filler
neck 73. The fuel dispenser 30 is vapor equipped such that the spout
64 nozzle 62 and hose 60 contain a vapor return line 76 for vapor
78 to be recovered. If the fuel dispenser 30 contains an assisted
vapor recovery system, a vapor pump 80 is usually placed inline
and fluidly coupled to the vapor return line 76 to create suction
in the vapor return line 76. The control system 52 activates the
vapor pump 80 and opens an optional vapor valve 59 inline in the
vapor return line 76 when fuel 44 begins flowing, and vapor 78 is
being pushed out of the vehicle fuel tank 72. The suction in the
vapor return line 76 substantially captures the vapor 78 at the
spout 64 of the nozzle 62.
The vapor 78 returns through the vapor return line 78 inside the
nozzle 62 and hose 60 and up to the canopy 58 of the fuel dispenser
30. As the hose 60 enters the canopy 58 the vapor return line 76
and fuel supply conduit 50 are separated into two separate conduits.
The vapor 78 is returned through the vapor return line 76 back to
the ullage area 46 of the underground storage tank 34. In this manner,
vapors 78 are recovered and returned back to the underground storage
tank 34 instead of being released to atmosphere at the filler fuel
neck 73. Even if the fuel recovery-equipped fuel dispenser 30 is
equipped with some other type of vapor recovery system, the principle
of returning recovered vapors to the underground storage tank 34
remains the same. For more information on vapor recovery systems,
see aforementioned U.S. Pat. Nos. 5040577 and RE35238 in addition
to U.S. Pat. Nos. 6170539; 6386246; 5038838; and 5195564
all of which are hereby incorporated by reference in their entireties.
According to the present invention, a vapor flow meter 86 is placed
inline to the vapor return line 76 so that the amount of vapor 78
being returned is measured and confirmed by the control system 52
to detect leaks and/or measure the V/L ratio of the fuel dispenser
30. If too much pressure builds up inside the underground storage
tank 34 the vapor 78 in the ullage area 46 can be released through
a vent pipe 82 coupled to the ullage area 46 to atmosphere. A
pressure relief valve 84 is placed on the vent pipe 82 and the
pressure relief valve 84 opens when a threshold pressure in the
vent pipe 82 and ullage area 46 is exceed a threshold pressure like
described in U.S. Pat. No. 5464466 entitled "Fuel storage
tank vent filter system," which is hereby incorporated by reference
in its entirety.
In the present invention, the vapor flow meter 86 is a turbine
flow meter. An example of a turbine flow meter is illustrated in
FIG. 3 and is like that described in U.S. Pat. No. 5689071 entitled
"Wide range, high accuracy flow meter," which is hereby
incorporated by reference in its entirety. The turbine vapor flow
meter 86 is an inferential meter, and therefore can be small in
size and conveniently located in any desired location in the vapor
return line 76.
As illustrated in FIG. 3 a turbine vapor flow meter 86 is comprised
of a shaft 88 surrounded by a cylindrical, hollow housing 90. One
or more turbine rotors 92A, 92B are mounted on the shaft 88. Each
of the turbine rotors 92A, 92B contains vanes 94 that are made out
of a magnetic material. As the vapor 78 enters into the inlet 93
of the turbine vapor flow meter 86 the vapor 78 flows into the
vanes 94 causing the turbine rotors 92A, 92B to rotate. As the
turbine rotors 92A, 92B rotate, pick-off coils 96A, 96B detect each
of the vanes 94 as they rotate. Shaft 98A, 98B are located so that
an electrical connection can be made to pick-off coils 96A, 96B
contained inside the shafts 98A, 98B. The pick-off coils 96A, 96B
generate an a-c signal to generate a magnetic field inside the meter
86 at a given carrier frequency. As the turbine rotors 92A, 92B
rotate, their vanes 94 cause a pulse to be superimposed on the carrier
waveform generated by the pick-off coils 96A, 96B. This pulse encoded
carrier signal is communicated to the control system 52 via its
coupling to the pick-off coils 96A, 96B. The vapor 78 flow rate
is proportional to the rotational speed of the rotors 92A, 92B.
In this manner, the control system 52 can determine the rotational
speed of the turbine rotors 92A, 92B to determine the rate of vapor
78 entering the vapor flow meter 86 and exiting out of the vapor
flow meter via the outlet 99 and thereafter returning to the underground
storage tank 34.
Even after the vapor 78 discontinues flowing inside the turbine
vapor flow meter 86 the rotors 92A, 92B will continue to rotate
for a period of time due to their previous rotational momentum.
This could cause inaccurate measurement of vapor 78 rate, because
the rotors 92A, 92B will continue to rotate and superimpose pulses
on the pick-off coil 96A, 96B carrier signals even after vapor 78
flow has stopped. It is this problem that the present invention
solves so that a turbine vapor flow meter 86 may be used to accurately
measure recovered vapor 78.
FIGS. 4 and 5 illustrate the solutions to this problem according
to the present invention. The present invention solves this problem
generally by ignoring measurements made by the vapor flow meter
86 when fuel 44 is not flowing, and acknowledging measurements made
by the vapor flow meter 86 when fuel 44 is flowing. This is because
vapor 78 is not pushed out of the vehicle fuel tank 72 unless fuel
44 is being delivered into the vehicle fuel tank 72. There are several
different methods and indicators that can be used to determine when
fuel 44 is flowing and when it is not, all of which can be used
in the present invention.
FIG. 4 illustrates a fuel dispenser 30 component diagram related
to how the fuel dispenser 30 determines the rate of vapor 78 being
recovered and returned to the underground storage tank 34 through
the vapor return line 76. Fuel 44 begins flowing through the fuel
conduit 48 and encounters a fuel flow control valve 54. The control
system 52 controls the opening and closing of the fuel flow control
valve 54 depending on when fueling is desired. When dispensing is
activated, the dispenser electronics 106 sends a fuel flow control
valve signal 103 to the fuel flow control valve 54 to open, thereby
allowing fuel 44 to pass therethrough. The fuel 44 then enters the
fuel meter 56 to be measured.
The fuel meter 56 may be an inferential meter or positive displacement
meter. In the example illustrated in FIG. 4 the fuel meter 56 is
a positive displacement meter. As the fuel 44 enters the fuel meter
56 a pulser 100 generates a fuel flow meter pulser signal 102 that
is inputted into the dispenser electronics 106. The fuel flow meter
purser signal 102 is a pulse stream indicative of the fuel 44 flow
volume through the fuel meter 56. For example, a thousand fuel flow
meter pulser signals 102 may equal one gallon of fuel 44. The vapor
flow meter 86 also communicates a vapor flow meter pulser signal
112 to the control system 52 so that the control system 52 can measure
the rate of vapor 78 being recovered. When the dispenser electronics
106 receives the fuel flow meter pulser signal 102 the dispenser
electronics 106 communicates to the vapor recovery electronics 108
to activate the vapor recovery system of the fuel dispenser 30 in
this embodiment.
As the fuel 44 exits the fuel meter 56 the fuel 44 passes through
a flow switch 104 located on the outlet side of the fuel meter 56.
The flow switch 104 is optional, and is one method of determining
when pulses from the vapor flow meter 86 are being generated falsely
even though the turbine rotors 92 continue to rotate. After the
fuel 44 exits the flow switch 104 the fuel 44 is delivered to the
hose 60 and nozzle 62 to be delivered to the vehicle fuel tank 72.
The fuel switch 104 opens and closes based on the force of the
fuel 44 flowing out of the fuel meter 56. When fuel 44 is flowing
at a rate above a certain threshold, the flow switch 104 opens.
When fuel 44 is no longer flowing and/or at a rate below a threshold
value, the flow switch 104 closes. A flow switch signal 105 indicates
when the flow switch 104 is open and closed. This flow switch signal
105 is inputted into the dispenser electronics 106.
The vapor recovery electronics 108 outputs a vapor pump signal
109 to the vapor pump 80 to be activated when the dispenser electronics
106 receives fuel flow meter pulser signals 102 from the pulser
100. If a vapor valve 59 is provided, the control system 52 also
generates a vapor valve signal 111 to open the vapor valve 59 to
allow vapor 78 to pass through the vapor return line 76. The vapor
pump 80 causes a vacuum to be created inside the vapor return line
76 such that vapor 78 escaping from the vehicle fuel tank 72 is
drawn into the vapor return line 76. As the vapor 78 returns in
the vapor return line 76 back to the underground storage tank 34
the vapor 78 passes through the turbine vapor flow meter 86 which
may be like that illustrated in FIG. 3. As the turbine rotors 92A,
92B rotate, the pick-off coil 96 generates a pulse stream by emitting
a vapor flow meter pulser signal 112 that is input into the dispenser
electronics 106. In this manner, the volume of vapor 78 passing
through the vapor return line 76 and passed back to the underground
storage tank 34 can be measured and recorded by the dispenser electronics
106.
In FIG. 4 the dispenser electronics 106 and vapor recovery electronics
108 are shown as separate subsystems of the control system 52; however,
these control electronics may be incorporated into one system.
The turbine vapor flow meter 86 may continue to generate a vapor
flow meter pulser signal 112 even after vapor 78 has stopped flowing
through the vapor return line 76 due to the forward momentum of
the turbine rotors 92. Therefore, the present invention provides
for the control system 52 to be able to ignore the vapor flow meter
pulser signal 112 when vapor 78 is no longer flowing through the
vapor return line 76 so that vapor 78 flow measurements discontinue
to occur after fuel 44 flow stops. This is because vapor 78 is not
pushed out of the vehicle fuel tank 72 when fuel 44 is not being
delivered to the vehicle fuel tank 72. The present invention encompasses
ignoring the vapor flow meter pulser signal 112 when fuel 44 is
not flowing, and acknowledging the vapor flow meter pulser signal
112 when fuel 44 is flowing.
FIG. 5 illustrates a flow chart of how the control system 52 determines
when to acknowledge and to ignore the vapor flow meter pulser signal
112 to provide an accurate accounting of vapor 78 being returned
to the underground storage tank 34.
The process starts (step 200) and the fuel dispenser 30 receives
a dispensing command to begin dispensing (step 202). The fuel dispenser
30 opens the fuel flow control valve 54 to allow fuel 44 to flow
through the fuel conduit 48 (step 204). The control system 52 begins
to count pulses from the fuel flow meter pulser signal 102 (step
206). The control system 52 converts the fuel flow meter pulser
signal 102 into fuel volume (step 208). If after this point fuel
44 is flowing as indicated by fuel flow meter pulser signal 102
(decision 210), the control system 52 counts pulses from the vapor
flow meter pulser signal 112 (step 212) and converts the vapor flow
meter pulser signal 112 to a vapor volume (step 214).
The control system 52 may perform the optional step of calculating
a volume to liquid ratio (V/L) by dividing the vapor volume by the
fuel volume, as performed in steps 208 and 214 respectively (step
216). The V/L ratio may also be reported to any number of systems
including the site controller 26 the tank monitor 36 and off-site
using off-site communication links 28 38. An alarm may be generated
if the V/L ratio is not within predesigned limits. For more information
on determination of V/L ratios for vapor recovery-equipped fuel
dispensers 30 and related performance, see U.S. Pat. No. 6460579
entitled "Vapor flow and hydrocarbon concentration sensor for
improved vapor recovery in fuel dispensers," incorporated herein
by reference in its entirety.
After the V/L ratio is calculated, if desired (step 216), the process
repeats by returning back to step 206 whereby the fuel dispenser
30 continues to count pulses from the fuel flow meter pulser signal
102.
If in decision 210 fuel 44 is not flowing, the control system 52
inherently knows that vapor 78 is also no longer flowing through
the vapor return line 76 since vapor 78 is only pushed out of the
vehicle fuel tank 72 if fuel 44 is being dispensed into the vehicle
fuel tank 72. The control system 52 thereafter ignores the vapor
flow meter pulser signal 112 received from the vapor flow meter
86 (step 218). The control system 56 next determines if fuel 44
is no longer flowing because the fueling transaction is complete
(decision 220). If the fueling transaction is complete, typically
because the nozzle 60 is returned back to the fuel dispenser 30
and/or the nozzle 60 lift handle (not shown) is placed back down
in its resting position, the control system 56 closes the fuel flow
control valve 54 (step 222) and the fueling transaction ends (step
224). If the fueling transaction is not completed (decision 220),
the process returns back to step 206 to continue counting any pulses
101 from the pulser 100.
Although FIGS. 4 and 5 describe generally the present invention
of ignoring vapor flow meter pulser signals 112 when fuel 44 is
no longer flowing to arrive at an accurate vapor 78 flow recovery
measurement, there are several different methods and techniques
in which the control system 52 can choose to determine when fuel
44 is flowing or not. Although the present invention is not limited
to these specific methods and techniques, specific methods and techniques
are described below.
Flow Switch
One method of the control system 52 determining when to ignore
and when to acknowledge vapor flow meter pulser signals 112 from
the vapor flow meter 58 encompasses use of a flow switch. As illustrated
in FIG. 4 as the fuel 44 exits the fuel meter 56 the fuel 44 passes
through a flow switch 104 located on the outlet side of the fuel
meter 56. The flow switch 104 is optional, and is one method of
determining when pulses from the vapor flow meter 86 are being generated
falsely even though the turbine rotors 92 continue to rotate. After
the fuel 44 exits the flow switch 104 the fuel 44 is delivered
to the hose 60 and nozzle 62 to be delivered to the vehicle fuel
tank 72.
The fuel switch 104 opens and closes based on the force of the
fuel 44 flowing out of the fuel meter 56. When fuel 44 is flowing
at a rate above a certain threshold, the flow switch 104 opens.
When fuel 44 is no longer flowing or is flowing at a rate below
a threshold value, the flow switch 104 closes. A flow switch signal
105 indicates when the flow switch 104 is open and closed. This
flow switch signal 105 is inputted into the dispenser electronics
106. In one embodiment of the present invention, the dispenser electronics
106 ignores the vapor flow meter purser signal 112 when the fuel
flow switch signal 105 indicates that fuel 44 is no longer flowing
or is flowing at a significantly low flow rate. This is because
vapor 78 cannot be recovered if fuel 44 is not flowing to the vehicle
fuel tank 72.
Fuel Meter Pulser Signal
Another method for the control system 52 to determine when to ignore
and when to acknowledge vapor flow meter pulser signals 112 from
the vapor flow meter 58 is by use of the fuel meter pulser 100.
When the fuel meter pulser 100 generates a pulser signal 101 fuel
44 is flowing through the flow meter 56. When fuel 44 is flowing
through the flow meter 56 at more than a nominal rate, fuel 44 is
being delivered to the vehicle fuel tank 72 via the hose 60 and
nozzle 62. Therefore, the control system 52 can choose to acknowledge
or ignore vapor flow meter pulser signal 112 based on when fuel
meter pulse signals 101 are received and not received, respectively.
Fuel Flow Control Valve
Another method for the control system 52 to determine when to ignore
and when to acknowledge vapor flow meter pulser signals 112 from
the vapor flow meter 58 is by detection of the fuel flow control
valve control signal 103. When the control system 52 desires to
allow fuel 44 to be delivered to a vehicle fuel tank 72 the control
system 52 generates a fuel flow control valve signal 103 to open
the fuel flow control valve 54. When the control system 52 desires
to discontinue fuel 44 delivery to a vehicle fuel tank 72 the control
system 52 generates a fuel flow control valve signal 103 to close
the fuel flow control valve 54. The control system 52 may use the
output of the fuel flow control valve signal 56 to determine when
to ignore (when fuel flow control valve 54 is closed) and when to
acknowledge (when fuel flow control valve 54 is opened) vapor flow
meter purser signals 112. This embodiment may be particularly of
value for the unillustrated embodiment of the control system 52
that receives fuel flow meter pulser signal 102 being a different
system from the control system that determines when to ignore and
when to acknowledge the vapor flow meter pulser signal 112 since
the "Fuel Meter Pulser Signal" embodiment, described above,
cannot be used for such a separate control system 52 architecture.
Vapor Pump Signal
Another method for the control system 52 to determine when to ignore
and when to acknowledge vapor flow meter pulser signals 112 from
the vapor flow meter 58 is by use of the vapor pump signal 109.
When the control system 52 generates a vapor pump signal 109 to
activate the vapor pump 80 this means that the control system 52
is receiving a fuel flow meter pulser signal 102 indicative of fuel
44 flow. The control system 52 may use the output of the vapor pump
signal 109 to determine when to ignore (when vapor pump signal 109
is not active) and when to acknowledge (when vapor pump signal 109
is active) vapor flow meter pulser signals 112.
Vapor Valve
If the fuel dispenser 30 contains a vapor valve 59 as illustrated
in FIG. 2 the control system 52 opens the vapor valve 59 once fuel
44 begins flowing so that recovered vapors 78 can return through
the vapor return line 76 back to the underground storage tank 34.
The vapor valve 59 is closed when the fuel dispenser 30 is not operational
so that air is not pulled into the underground storage tank 34 during
idle times. When the control system 52 generates a vapor pump signal
109 to activate the vapor pump 80 this means that the control system
52 is receiving fuel flow meter pulser signal 102 indicative of
fuel 44 flow. The control system 52 may use the output of the vapor
valve signal 111 to determine when to ignore (when vapor valve signal
111 is not active) and when to acknowledge (when vapor valve signal
111 is active) vapor flow meter pulser signals 112.
Those skilled in the art will recognize improvements and modifications
to the preferred embodiments of the present invention. All such
improvements and modifications are considered within the scope of
the concepts disclosed herein and the claims that follow. |