U.S. patent application number 11/247561 was filed with the patent office on 2007-04-12 for gas filling system.
Invention is credited to Joseph Perry Cohen, David John Farese.
Application Number | 20070079892 11/247561 |
Document ID | / |
Family ID | 37715460 |
Filed Date | 2007-04-12 |
United States Patent
Application |
20070079892 |
Kind Code |
A1 |
Cohen; Joseph Perry ; et
al. |
April 12, 2007 |
Gas filling system
Abstract
A system and method for supplying a gas from a supply of
compressed gas to a receiving vessel by measuring the pressure of
gas being directed into the receiving vessel in successive selected
time intervals to determine the actual ramp rate of gas being
directed into the receiving vessel and providing means for
comparing the actual ramp rate with a desired ramp rate and
controlling the gas flow rate in response to that comparison. In a
preferred embodiment the pressure of the gas at an upstream end of
the system is monitored and directed into a controller and this
latter pressure is employed in determining the mass flow of gas
into the receiving vessel.
Inventors: |
Cohen; Joseph Perry;
(Bethlehem, PA) ; Farese; David John;
(Riegelsville, PA) |
Correspondence
Address: |
AIR PRODUCTS AND CHEMICALS, INC.;PATENT DEPARTMENT
7201 HAMILTON BOULEVARD
ALLENTOWN
PA
181951501
US
|
Family ID: |
37715460 |
Appl. No.: |
11/247561 |
Filed: |
October 10, 2005 |
Current U.S.
Class: |
141/105 |
Current CPC
Class: |
F17C 2221/033 20130101;
F17C 13/025 20130101; F17C 5/007 20130101; F17C 2225/036 20130101;
F17C 5/06 20130101; F17C 7/00 20130101; F17C 2223/036 20130101;
G05D 16/204 20130101; F17C 2250/043 20130101; F17C 2260/023
20130101; F17C 2270/0168 20130101; F17C 2270/0139 20130101; F17C
2250/0626 20130101; F17C 2250/032 20130101; F17C 2221/017 20130101;
F17C 2225/0123 20130101; F17C 2260/025 20130101; Y02E 60/32
20130101; F17C 2223/0123 20130101; F17C 2221/012 20130101 |
Class at
Publication: |
141/105 |
International
Class: |
B65B 3/04 20060101
B65B003/04 |
Claims
1. A gas filling system for supplying a gas from a supply of
compressed gas to a receiving vessel, said filling system
including: a. a source of compressed gas; b. a receiving conduit
communicating the source with a plurality of gas transmission lines
in parallel with each other; c. a delivery conduit communicating
with a receiving vessel and with said plurality of gas transmission
lines; d. a control valve in each of a plurality of said gas
transmission lines upstream of said delivery conduit for
communicating said each of said plurality of gas transmission lines
with said delivery conduit when in an opened condition; at least
some of said gas transmission lines having differing orifice
coefficients for transmitting gas at different flow rates
therethrough; e. a flow controller for opening and closing selected
control valves to control the flow rate of gas to said receiving
vessel and having a desired ramp rate communicating therewith; f. a
pressure monitor downstream of the control valves for measuring the
pressure of gas being directed into the receiving vessel in
selected time intervals and continuously transmitting said pressure
of gas to said flow controller, said flow controller comparing the
desired ramp rate communicating therewith with said pressure of gas
and controlling the flow rate of gas through the transmission lines
to said receiving vessel based upon the comparison of the desired
ramp rate with said pressure of gas.
2. The gas filling system of claim 1, wherein said flow controller
is a programmable logic controller having the desire ramp rate
programmed therein.
3. The gas filling system of claim 1, wherein the desire ramp rate
is transmitted to the flow controller from another source.
4. The gas filling system of claim 1, wherein said pressure monitor
measures pressure of gas in said delivery conduit in selected time
intervals.
5. The gas filling system of claim 1, wherein each gas transmission
line has an orifice coefficient different from the orifice
coefficient in every other gas transmission line.
6. The gas filling system of claim 5, wherein each orifice
coefficient differs from the next smallest orifice coefficient by a
factor of substantially 2.
7. The gas filling system of claim 1, wherein said pressure monitor
measures an increase in pressure in successive selected time
intervals, which constitutes an actual ramp rate of gas being
directed into said receiving vessel, said flow controller comparing
the actual ramp rate with the desired ramp rate and controlling the
flow rate of gas through the transmission lines to said receiving
vessel based upon the difference between the actual ramp rate and
the desired ramp rate.
8. The gas filling system of claim 7, wherein said flow controller
increases the flow rate of gas when the actual ramp rate is lower
than the desired ramp rate and decreases the flow rate of gas when
the actual ramp rate is higher than the desired ramp rate.
9. The gas filling system of claim 1, including a second pressure
monitor upstream of said transmission lines for measuring gas
pressure upstream of said transmission lines and transmitting data
representative of said gas pressure upstream of said transmission
lines to said flow controller; said flow controller including data
representative of the size of orifices in transmission lines
communicating with said delivery conduit through opened control
valves, said flow controller including means for processing data
representing said gas pressure upstream of said transmission lines
and data representative of the size of orifices in transmission
lines communicating with said delivery conduit through opened
control valves for determining the mass flow of gas into said
receiving vessel.
10. The gas filling system of claim 1, including a second pressure
monitor upstream of said transmission lines for measuring gas
pressure upstream of said transmission lines and transmitting data
representative of said gas pressure upstream of said transmission
lines to said flow controller; said flow controller determining the
ratio of the pressure measured downstream of said transmission
lines to the pressure measured upstream of said transmission lines
and determining the mass flow of gas into said receiving vessel
based upon said ratio.
11. A method of filling a receiving vessel from a source of
compressed gas employing a system including a receiving conduit
communicating with said source of compressed gas and with a
plurality of transmission lines in parallel with each other; a
deliver conduit downstream of said plurality of transmission lines
communicating with said receiving vessel, a control valve in each
of a plurality of said gas transmission lines upstream of said
delivery conduit for communicating said each of said plurality of
gas transmission lines with said delivery conduit when in an opened
condition; at least some of said gas transmission lines having
differing orifice coefficients for transmitting gas at different
flow rates therethrough and a flow controller for opening and
closing selected control valves to control the flow rate of gas to
said receiving vessel, said flow controller having a desired ramp
rate communicating therewith, said method including the steps of
measuring the pressure of gas being directed into the receiving
vessel in successive selected time intervals to determine actual
ramp rate of gas being directed into the receiving vessel;
comparing the actual ramp rate with the desired ramp rate and
controlling gas flow through said plurality of transmission lines
in response to said comparison.
12. The method of claim 11, including the step of monitoring the
pressure of gas upstream of said control valves, determining the
size of orifices in transmission lines communicating with said
receiving conduit through opened control valves and calculating the
mass flow of gas into said receiving vessel based upon said
pressure of gas upstream of said control valves and the size of
orifices in transmission lines communicating with said receiving
conduit through opened control valves.
13. The method of claim 11, including the step of monitoring the
pressure of gas upstream of said control valves, determining the
ratio of the pressure of gas being directed into the receiving
vessel to the pressure of gas upstream of said control valves and
based upon said ratio calculating the mass flow of gas into said
receiving vessel.
14. A method of filling a receiving vessel from a source of
compressed gas including the steps of measuring pressure of gas
being directed into the receiving vessel in successive selected
time intervals to determine actual ramp rate of gas being directed
into the receiving vessel; comparing the actual ramp rate with a
desired ramp rate and controlling gas flow rate into said receiving
vessel in response to said comparison.
15. The method of claim 14, wherein the step of controlling gas
flow rate is carried out by increasing the gas flow rate when the
actual ramp rate is lower than the desired ramp rate and be
decreasing the gas flow rate when the actual ramp rate is higher
than the desired ramp rate.
16. The method of claim 14, including the steps of measuring gas
pressure between said source and a plurality of transmission lines
in parallel with each other and including control valves therein,
said control valves being operable between opened and closed
conditions, transmission lines with opened valves therein
communicating said source with a delivery conduit communicating
with said receiving vessel downstream of said transmission lines,
determining the size of orifices in transmission lines
communicating with said delivery conduit through opened control
valves and calculating the mass flow of gas into said receiving
vessel based upon said pressure of gas upstream of said control
valves and the size of orifices in transmission lines communicating
with said delivery conduit through opened control valves.
17. The method of claim 14, including the steps of measuring gas
pressure between said source and a plurality of transmission lines
in parallel with each other and including control valves therein,
said control valves being operable between opened and closed
conditions, transmission lines with opened valves therein
communicating said source with a delivery conduit communicating
with said receiving vessel downstream of said transmission lines,
determining the ratio of the pressure of gas being directed into
the receiving vessel to the pressure of gas between said source and
said plurality of transmission lines and based upon said ratio
calculating the mass flow of gas into said receiving vessel.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a system and method for filling a
receiving vessel or tank from a source of compressed gas, and more
specifically to a system and method for filling a receiving tank or
vessel, e.g., a receiving tank in a vehicle, in a manner that aids
in preventing excess heating of the tank and also in eliminating
excess fill time, particularly when filling large receiving
tanks.
[0002] In a system for filling a receiving tank or vessel with
compressed gas it is necessary to control the flow rate of the gas
so that the receiving tank does not overheat. Overheating occurs as
a result of both adiabatic compression of the gas, and, when the
gas is hydrogen or helium, by the reverse Joule-Thompson effect.
The heat of compression is partially offset by the isentropic
expansion cooling within the storage vessel. Moreover, for gases
other than hydrogen and helium, a conventional Joule-Thompson
effect takes place, which can further mitigate against overheating
resulting from the impact of adiabatic compression of gas in the
receiving tank. However, even when charging a receiving tank or
vessel with gases other than hydrogen and helium, the adiabatic
compression of gas in the receiving tank does create an overheating
concern.
[0003] For various fueling operations, such as in the delivery of
gaseous hydrogen to a receiving tank in a vehicle, it is necessary
to provide some form of flow control in order to avoid excess
heating of the receiving tank and also to avoid excess fill time,
particularly when filling a large receiving tank, e.g., a receiving
tank in a large vehicle.
[0004] U.S. Pat. No. 6,786,245, assigned to Air Products &
Chemicals, Inc., the assignee of the present application, discloses
a programmable logic controller (PLC) that can receive information
on pressure in the receiving tank, e.g., from the supply hose,
which indirectly measures or reflects the pressure in the receiving
tank, and on ambient temperature, and regulates the set point of
the programmable pressure regulator using an I/P controller based
upon these latter two parameters. The system can be seen best in
FIG. 5 of the '245 patent. This latter system is believed to lack
desired reliability, due to the potential for malfunctions
associated with the control valve, the PLC, and/or the I/P
controller.
[0005] Mickeet al., U.S. Pat. No. 5,826,632 discloses different
options for controlling the flow of gas during a filling process,
including the use of variable orifices, control valves and a fixed
orifice in combination with a valve.
[0006] Kitayama et al., U.S. Pat. No. 6,210,482 discloses a system
for feeding gases for use in a semiconductor system in which
multiple orifices of the same or different size are employed to
supply one or more of the gases.
[0007] Togasawa et al., U.S. Pat. No. 6,598,624 describes the
effect of orifice diameter and upstream pressure on the fill rate
to a hydrogen tank.
[0008] Petro, U.S. Pat. No. 4,487,187 discloses a system of
parallel lines with solenoid valves and orifices supplying a
compressible fluid such as methane or propane to an internal
combustion engine; the orifice sizes being proportional to
successive powers of 2.
[0009] Although the prior art does disclose various techniques for
attempting to control flow rate of gases, none of the systems have
recognized the benefit of controlling, or the desire to control the
ramp rate of the gas to limit the temperature rise in a receiving
tank, or vessel, and also, to avoid prolonged fill times,
particularly when filling large tanks or vessels. It is to this
latter-type of system that the present invention is directed.
BRIEF SUMMARY OF THE INVENTION
[0010] In accordance with both the system and process of this
invention the flow rate of compressed gas from a source to a
receiving vessel or tank is controlled to achieve a desired ramp
rate. "Ramp rate" is a change in pressure with time, e.g., either
an increase or decrease in pressure with time.
[0011] In a gas filling system in accordance with this invention a
receiving conduit communicates a source of compressed gas with a
plurality of gas transmission lines that are in parallel with each
other. A delivery conduit communicates with a vessel intended to
receive compressed gas and also with the plurality of gas
transmission lines. A control valve in each of a plurality of the
gas transmission lines upstream of the delivery conduit
communicates those gas transmission lines with the delivery conduit
when in an opened condition. At least some, and preferably all of
the gas transmission lines have differing orifice coefficients for
transmitting gas at different flow rates therethrough.
[0012] A flow controller has a desired ramp rate communicating with
it, and the flow controller operates to open and close selected
control valves to thereby control the flow rate of gas to the
receiving vessel. A pressure monitor downstream of the control
valves measures the pressure of gas being directed into the
receiving vessel in selected time intervals, to essentially monitor
the actual ramp rate of the gas flowing into the receiving vessel.
The pressure of gas measured by the pressure monitor is directed
continuously to the flow controller, and the flow controller
compares the desired ramp rate that communicates with it with the
pressure of gas being monitored downstream of the control valves
and controls the flow rate of gas through the transmission lines to
the receiving vessel based upon that comparison.
[0013] In the preferred embodiments of this invention the flow
controller increases the flow rate of gas when the actual ramp rate
is lower than the desired ramp rate and decreases the flow rate of
gas when the actual ramp rate is higher than the desired ramp
rate.
[0014] Reference throughout this application to the desired ramp
rate "communicating" with the flow controller includes programming
the desired ramp rate directly into the flow controller (e.g., when
the flow controller is a programmable logic controller or similar
device), or feeding the desired ramp rate into the controller
through another source, such as a remote computer system or other
customer interface.
[0015] In the preferred embodiment of this invention the pressure
monitor downstream of the control valves monitors the pressure of
gas in the delivery conduit, which directly communicates with the
receiving vessel or tank.
[0016] In the most preferred embodiments of this invention each gas
transmission line has an orifice coefficient different from the
orifice coefficient in every other transmission line. Most
preferably each orifice coefficient differs from the next smallest
orifice coefficient by a factor of substantially 2, to thereby
permit a wide degree of control over the flow rate of gas through
the gas filling system.
[0017] In a preferred system of this invention the mass flow of gas
into the receiving vessel is determined to thereby determine the
volume of gas employed to fill the vessel. This is particularly
desirable when the receiving vessel is a gas tank in a vehicle, and
actually is necessary in order to determine the volume of gas
employed to fill the vessel, to thereby establish the selling price
for the gas.
[0018] Specifically, in the preferred embodiment of this invention
a second pressure monitor is employed upstream of the transmission
lines for measuring the gas pressure upstream of the transmission
lines and transmitting that gas pressure to the flow controller.
The flow controller includes data regarding the size of orifices in
the transmission lines that actually are communicating with the
delivery conduit through opened control valves, and the flow
controller functions to determine the mass flow of gas into the
receiving vessel based upon the input from the second pressure
monitor and the data representing the size of orifices in
transmission lines is communicating with the delivery conduit
through opened control valves.
[0019] In another embodiment of this invention for determining the
mass flow of gas into the receiving vessel, the second pressure
monitor upstream of the transmission lines is employed, in the same
manner as in the above-described embodiment. However, in this
embodiment the flow controller determines the ratio of the pressure
measured downstream of the transmission lines, preferably by a
pressure monitor in the delivery conduit, to the pressure measured
upstream of the transmission lines by the second pressure monitor
and then determines the mass flow of gas into the receiving vessel
based upon that ratio.
[0020] In accordance with the broadest method of this invention a
receiving vessel is filled from a source of compressed gas by the
steps of measuring pressure of gas being directed into the
receiving vessel in successive selected time intervals to determine
the actual ramp rate of gas being directed into the receiving
vessel, comparing the actual ramp rate with a desired ramp rate and
controlling gas flow rate in response to that comparison.
[0021] Most preferably, the gas flow rate is increased when the
actual ramp rate is determined to be lower than the desired ramp
rate, and the gas flow rate is decreased when the actual ramp rate
is determined to be higher than the desired ramp rate. Thus, in the
preferred embodiment of this invention the gas flow rates are
established and/or varied during the filling cycle to achieve, or
approach, the desired ramp rate.
[0022] In a preferred method of filling a receiving vessel from a
source of compressed gas in accordance with this invention, a gas
filling system as described earlier herein is employed, and the
method includes the steps of measuring the pressure of gas being
directed into the receiving vessel in successive selected time
intervals to determine the actual ramp rate of gas being directed
into the receiving vessel; comparing the actual ramp rate with the
desired ramp rate and controlling gas flow through the plurality of
transmission lines in response to that comparison.
[0023] In accordance with a preferred method of this invention the
mass flow of gas into the receiving vessel is determined by
monitoring the pressure of gas upstream of the control valves
employed in the transmission lines, determining the size of
orifices in the transmission lines communicating with the receiving
conduit through opened control valves and calculating the mass flow
of gas into the receiving vessel based upon these latter two
parameters.
[0024] In an alternate method for determining the mass flow of gas
into the receiving vessel the pressure of gas upstream of the
control valves is monitored, the ratio of the pressure of gas being
directed into the receiving vessel to the pressure of gas upstream
of the control valves it is determined, and based upon that ratio
the mass flow of gas into the receiving vessel is calculated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention will be described by way of example with
reference to the accompanying FIGURE which is a schematic view
showing a representative gas filling system in accordance with this
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] Referring to the FIGURE, a gas filling system for supplying
a gas from a supply of compressed gas 12 to a receiving tank or
vessel 14 is schematically illustrated at 10. The gas filling
system 10 can be employed to fill a receiving vessel or tank 14
with a variety of different gases, e.g., hydrogen, helium, or
natural gas. A particularly desirable use of the filling system 10
is for filling a receiving tank or vessel 14 with hydrogen, and in
particular, to a system for filling a receiving tank or vessel of a
vehicle with hydrogen.
[0027] Still referring to the FIGURE, the gas filling system 10
includes a supply of gas, e.g., hydrogen, from a pressurized source
12. A variety of pressurized sources can be employed, such as a
single storage tank, a number of storage tanks, a pipe line supply,
or a supply from a compressor. The gas is directed from the
pressurized source 12 to a receiving tank 14 through a plurality of
gas transmission lines in parallel with each other. In the
illustrated system five transmission lines are shown at 16,
18,20,22 and 24. However, in accordance with the broadest aspects
of this invention the number of transmission lines can be varied
within wide limits, and the number of such transmission lines does
not constitute a limitation on the broadest aspects of this
invention.
[0028] The source 12 of compressed gas communicates with the
plurality of transmission lines l6, 18, 20, 22 and 24 through a
receiving conduit 26. The downstream ends of each of the
transmission lines communicate with the receiving tank or vessel 14
through a delivery conduit 28.
[0029] Control valves, which preferably are solenoid valves 16a,
18a, 20a, 22a and 24a, are located in the transmission lines 16,
18, 20, 22 and 24, respectively.
[0030] Still referring to the FIGURE, orifice plates, schematically
illustrated at 16b, 18b, 20b, 22b and 24b are provided in each of
the transmission lines 16, 18, 20, 22 and 24, respectively, and
these orifice plates include passages of different dimensions,
whereby the orifice coefficient (Cv) of each of the transmission
lines is different from the orifice coefficient in every other
line.
[0031] In a preferred embodiment of this invention the orifice
coefficients Cv of the passages in the orifice plates successively
increase by a factor of 2. In particular, assuming that orifice
plate 16a has a relative orifice coefficient of 1, then orifice
plate 18b has an orifice coefficient of substantially 2; orifice
plate 20b has an orifice coefficient of substantially 4; orifice
plate 22b has an orifice coefficient of substantially 8 and orifice
plate 24b has an orifice coefficient of substantially 16.
[0032] As illustrated, the system 10 includes a pressure monitor
30, preferably monitoring pressure in the delivery conduit 28 at
predetermined, selected time intervals, and continuously feeds the
pressure measurements (which increase over time) to controller 32,
which preferably is a programmable logic controller (PLC). The
programmable logic controller 32 preferably includes a desired ramp
rate programmed into it. However, it is within the scope of this
invention to actually feed or direct a signal into the programmable
logic controller 32 from a separate source or interface, such as a
suitable customer computer interface schematically illustrated at
34. Based upon the required or desired ramp rate, either as
programmed into the PLC 32 or inputted into the PLC from a separate
source or interface 34, the PLC functions to open one or more of
the control valves 16a, 18a, 20a, 22a and 24a to establish the
desired flow of gas.
[0033] For example, the PLC may open valve 20a to establish a flow
rate through orifice plate 20b for a predetermined period of time,
e.g., 5 seconds, while measuring the pressure rise during that
period of time. That specific rise in pressure provides an estimate
of the size of the receiving tank, which, in turn, provides a
baseline for selecting the valves to be opened initially to
establish the desired, proper ramp rate.
[0034] As the gas is flowing through the delivery conduit 28 into
the receiving tank 14, the pressure within the tank will
continuously increase. The pressure increase over preselected
periods of time is monitored by pressure monitor 30, which feeds a
signal indicative of the pressure increase to the PLC 32. The
pressure increase that continuously is directed to the PLC during
the preselected period of time represents the actual ramp rate of
the gas flow into the receiving tank 14. This ramp rate is compared
to the desired ramp rate that either is programmed into the PLC 32
or directed to the PLC through a separate interface 34, to
determine whether the actual ramp rate is either lower or higher
than the desired ramp rate.
[0035] If the actual ramp rate is lower than the desired ramp rate
the PLC will operate selected control valves 16a through 24a to
increase the flow rate through the transmission lines 16, 18, 20,
22 and 24, and thereby increase the actual ramp rate.
[0036] If the actual ramp rate is determined to be higher than the
desired ramp rate then the PLC 32 will function to control the
valves 16a through 24a in a manner to reduce the flow rate of gas
through the transmission lines 16 through 24, and thereby lower the
actual ramp rate of gas into the receiving tank 14.
[0037] In order to prevent a rapid change in flow rate, thereby
creating an undesired pressure pulse of gas to the receiving tank
14, the various solenoid valves 16a through 24a can be sequenced in
a manner to minimize the change in total orifice coefficient. For
example, if solenoid valve 20a is opened and the flow rate needs to
be increased to maintain the proper ramp rate, valve 16a would be
opened to increase the total orifice coefficient from 4 to 5, i.e.,
a change of only one unit. If additional flow is required, valve
16a would be closed and valve 18a would be opened so that the total
orifice coefficient is increased to 6, i.e., an additional increase
of only one unit. Thus, by providing different orifice coefficients
in the various transmission lines, such that each orifice
coefficient differs from the next smallest orifice coefficient by a
factor of substantially two, the system can be controlled in a
manner to gradually increase (or decrease) the total orifice
coefficient communicating with the receiving tank 14 in single
units.
[0038] From the above explanation it should be apparent that the
gas filling system 10 in accordance with this invention functions
to selectively control flow rates through one or more of the
transmission lines 16 through 24 during the filling cycle to
achieve, or approach, a desired ramp rate. As stated earlier, this
desired ramp rate either is programmed into the PLC 32 or is
directed to the PLC from a separate interface 34.
[0039] Still referring to the FIGURE, the gas filling system 10
also is designed to determine the mass flow of gas into the
receiving tank 14. In this manner, the quantity of gas directed
into the receiving tank can be monitored, e.g., in order to
determine the proper amount to be charged for the gas.
[0040] In order to measure the mass flow of gas into the receiving
tank the gas filling system 10 is provided with a second pressure
monitor 36 located upstream of the transmission lines 16 through
24. More preferably, the second pressure monitor 36 is connected to
the receiving conduit 26 to monitor the pressure within that line.
The absolute pressure level in line 26 is dependent upon the number
of valves 16a through 24a that are opened, to thereby communicate
the compressed gas with orifices having varying orifice
coefficients.
[0041] By including a second pressure monitor 36 in the receiving
conduit 26 the mass flow of gas into the receiving vessel can be
determined, preferably by one of two methods. In both methods the
pressure measured by the monitor 36 is directed into the PLC 32 and
is employed in the determination of the mass flow of the gas.
[0042] In one of the two methods for determine the mass flow of gas
into the receiving vessel, the PLC 32 includes data representative
of the size of the orifices in the transmission lines that are in
communication with the delivery conduit 28 through opened control
valves, and the PLC 32 processes both data representing the gas
pressure measured by the monitor 36 and data representative of the
size of orifices in the transmission lines 16-24 communicating with
the delivery conduit 28 through opened control valves for
determine, or calculating, the mass flow of gas into the receiving
vessel 14. This gas flow can be displayed visually on a read out
screen or panel, or in other ways known to individuals skilled in
the art.
[0043] It should be noted that people skilled in the art fully
understand how the PLC 32 is capable of processing pressure data
determined by pressure monitor 36 and data representative of the
size of the orifices in the transmission lines communicating with
the delivery conduit through the open control valves to thereby
calculate the mass flow of gas into the receiving vessel.
Therefore, no further explanation is believed to be necessary.
[0044] In accordance with a second method for determining the mass
flow of gas into the receiving vessel the flow controller 32
determines the ratio of the pressure measured downstream of the
transmission lines by the pressure monitor 30 to the pressure
measured upstream of the transmission lines by the pressure monitor
36, and based upon that ratio, employs the appropriate formula for
determining the mass flow of gas into the receiving vessel.
[0045] In particular, when the ratio of the downstream pressure
measured by the monitor 30 to the upstream measured by monitor 36
is less than 0.5, choked flow exists. That is, the gas flowing
through the system is flowing at the speed of sound through the
various orifices, and based upon this condition; the mass of
material flowing through the system can be calculated using the
appropriate equation employed for choked flow. It should be
understood that measuring the choked flow has no effect on the flow
rates of the gas, but rather is used to measure the mass of
material flowing through the system. It also should be understood
that people skilled in the art clearly know and can select the
appropriate equation to use when choked flow exists.
[0046] If the ratio of the pressure measured by the pressure
monitor 30 to the pressure measured by the pressure monitor 36 is
greater than 0.5 then choked flow does not exist, and a different
equation is utilized by the PLC 32 to determine the mass flow of
gas through the system 10. As in the previous systems, the
determined gas flow can be displayed on a visually observable
monitor, or can be displayed in other ways known in the art. It
also should be understood that people skilled in the art clearly
know and can select the appropriate equation to use when choked
flow does not exist.
[0047] The gas filling system 10 of this invention is extremely
effective in avoiding excess heating of a receiving tank receiving
a charge of compressed gas, in particular, either hydrogen or
helium. Both of these latter gases tend to heat up as a result of
adiabatic compression of the gas and the reverse Joule-Thompson
effect. This problem of overheating exists even though the heat of
compression is partially offset by isentropic expansion cooling
within the storage vessel 12.
[0048] An additional benefit achieved by the present invention is
that the filling time for both small and large receiving tanks can
be maintained the same, by simply employing the same ramp rate in
both filling operations. This is not the case when other methods
are employed to control the fill rate, such as controlling the flow
rate of gas based on the absolute pressure increase in the
receiving vessel, as is disclosed in the Togasawa et al '624
patent, which was identified earlier in this application.
[0049] Although illustrated and described herein with reference to
certain specific embodiments, the present invention is nevertheless
not intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope and range
of equivalents of the claims and without departing from the spirit
of the invention.
* * * * *