Note: Descriptions are shown in the official language in which they were submitted.
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GASEOUS FLUID SUPPLY SYSTEM WITH SUBSYSTEM FOR ISOLATING A
STORAGE VESSEL FROM AN END USER
Technical Field
[0001] The present disclosure relates to a gaseous fluid supply system which
comprises a
subsystem for isolating the storage vessel from an end user when the end user
is not
operating. The disclosed system and method is particularly beneficial in a
gaseous fuel
supply system for an internal combustion engine when the engine is shut down
and fuel
remains in the fuel system.
Background
[0002] Natural gas or other gaseous fuels have been used to fuel vehicle
engines for
many years. The gaseous fuel in such fuel systems can be any fuel which is in
a gaseous
phase at standard pressure and temperature conditions (an absolute pressure of
1 bar (14.5
psig) and 0 C (32 F)). By way of example, typical gaseous fuels that can be
stored in
liquefied form include, among others, natural gas, propane, hydrogen, methane,
butane,
ethane, or mixtures comprising at least one of these fuels. Natural gas is in
itself a
mixture of gases and is often chosen as a fuel for internal combustion engines
because,
compared to conventional liquid fuels like diesel and gasoline, it is cleaner
burning,
abundant, and usually less expensive.
[0003] When natural gas is the selected fuel, it can be stored in a liquefied
form, as
liquefied natural gas (LNG) or in a gaseous form, as compressed natural gas
(CNG).
LNG is normally stored in a cryogenic storage vessel at temperatures between
about
-150 C and -115 C (between about -240 F and -175 F) and at pressures of
between
about 1 bar and 14 bar (between about 15 psig and 200 psig). An advantage of
storing a
gaseous fuel in liquefied form is higher energy density, which means that less
storage
space is needed to store the same amount of fuel. By way of example, LNG has
an
energy density that is about four times that of CNG.
[0004] Engines fuelled with gaseous fuels, such as natural gas, can operate by
injecting
the gaseous fuel into the engine's air intake manifold or by injecting the
fuel directly into
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the engine's combustion chamber. When the gaseous fuel is injected into the
engine's air
intake system the required fuel supply pressure is relatively low, typically
around 7 bar
(about 100 psig), whereas in systems which inject the fuel directly into the
engine's
combustion chamber, the fuel injection pressure needs to be higher than the in-
cylinder
pressure, and typically the fuel injection pressure is at least 200 bar (3000
psig) to enable
injection late in the compression cycle (when the engine piston is near top
dead center).
Both types of gaseous fuelled internal combustion engine systems can comprise
a fuel
pump located inside the storage vessel, or an external fuel pump located
outside of the
storage vessel to ensure that fuel is delivered to the engine at the required
injection
pressure at all times and during different engine operating modes, including
during
transients.
[0005] In such gaseous fuelled internal combustion engine systems, when the
engine is
not operating, for example during servicing, a fuel shut-off valve, positioned
downstream
of the fuel storage vessel, is closed to stop any fuel flow to the engine and
thereby fluidly
isolate the storage vessel, as described, for example, in applicant's co-
pending Canadian
patent application number 2,796,794. During engine shut down, some gaseous
fuel can
remain in the fuel system, and the pressure within the fuel supply line can
increase, for
example, as a result of heat transfer from the surrounding environment to the
fuel trapped
in the supply line. Fuel systems are designed with safety measures which
protect against
over-pressurization of the fuel systems, and if the pressure within the fuel
supply line
increases over a predetermined limit, a pressure relief valve will operate to
vent gaseous
fuel until the fuel pressure is reduced. Vented gaseous fuel can be captured,
burned or
otherwise oxidized, but if the gaseous fuel is vented to atmosphere or
consumed in a non-
productive way, venting even small amounts of fuel is undesirable and
wasteful.
[0006] Similarly, in other gaseous fluid supply systems which store a gaseous
fluid in
liquefied form and supply it in gaseous form to an end user, during the time
when the end
user is not operating, some gaseous fluid can remain in the supply system and
the
pressure in the fluid supply line can increase. Such gaseous fluid supply
systems have to
be provided with safety measures to protect the system from over-
pressurization and at
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the same time to reduce fluid losses by reducing the amount of fluid vented
from the
system.
[0007] Accordingly, there is a need for an improved gaseous fluid supply
system and
method of operating same to isolate the storage vessel from the end user when
the end
user is not operating and to better manage pressure and reduce the times when
gaseous
fluid is vented from the system.
Summary
[0008] A gaseous fluid supply system is disclosed having a subsystem for
isolating a
storage vessel from the end user. The gaseous fluid supply system comprises a
fluid
storage vessel, a fluid discharge line fluidly connected with the storage
vessel, wherein
one-way fluid flow is permitted out from the storage vessel, and a supply line
in fluid
communication with the fluid discharge line for supplying fluid to an end
user. The
subsystem for isolating the storage vessel from the end user comprises a
recirculation
loop fluidly connecting the fluid discharge line with the storage vessel, and
a switching
device operable between two positions. When the switching device is in a first
position,
associated with the time when the end user is shut down, fluid is stopped from
flowing
from the fluid discharge line to the supply line, and the fluid discharge line
is in fluid
communication with the recirculation loop and when the switching device is in
a second
position, associated with the time when the end user is running, the fluid
discharge line is
in fluid communication with the supply line and fluid is stopped from flowing
from the
fluid discharge line to the recirculation loop.
[0009]
The switching device can be a three-way valve which can be a manual
valve or an automatically controlled valve. Alternatively, the switching
device can
comprise a first two-way valve disposed on the supply line and a second two-
way
valve disposed on the recirculation loop. The first and second two-way valves
can be
automatic valves controlled by a system controller.
[0010]
The recirculation loop comprises a recirculation line that is fluidly
connected to the storage vessel. In some embodiments the recirculation loop
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comprises a recirculation line and a portion of a pressure relief line which
is fluidly
connected to the storage vessel such that the recirculation line is fluidly
connected to
the storage vessel through that portion of the pressure relief line. The
pressure relief
line is provided with a pressure relief valve which opens when a preset
pressure
threshold is exceeded. The preset pressure threshold is determined as a
function of a
maximum design pressure limit associated with the storage vessel.
[0011] In some embodiments, the recirculation loop is in direct fluid
communication with a vapor space within the storage vessel.
[0012] The gaseous fluid supply system can further comprise a vapor
supply line
in fluid communication with a vapor space of the storage vessel for delivering
fluid in
a gaseous state from the vapor space to the fluid discharge line when certain
predetermined conditions are met.
[0013] In preferred embodiments, the gaseous fluid supply system
comprises a
heat exchanger placed in the fluid discharge line or in the supply line for
increasing
the temperature of the fluid being supplied to the end user and converting it
into
gaseous form.
[0014] In preferred embodiments, the gaseous fluid supply system
comprises a
pump which supplies fluid from the storage vessel to the end user through the
fluid
discharge line and the supply line. The pump can be actuated by a hydraulic
drive or
by an electric motor. The pump can be disposed within a cryogenic space of the
storage vessel.
[0015] In preferred embodiments, the present system is a system for
supplying a
gaseous fuel to an internal combustion engine. The engine can be the prime
mover for
a vehicle.
[0016] In some embodiments, the gaseous fluid supply system can further
comprise a backpressure generating device located in the recirculation loop,
and
sensors for detecting the pressure in the supply line and for detecting the
pressure in
the fluid discharge line or, in preferred embodiments, for detecting at least
one
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parameter indicative of the activation status of a pump which supplies fluid
from the
storage vessel to the end user through the fluid discharge line and the supply
line. The
system further comprises a controller which receives signals from the sensors
and is
programmed to compare the received signals to signal characteristics of a
normal
operation of the end user to determine if the switching device is in a
position that
allows fluid communication between the fluid discharge line and the
recirculation
loop when the end user is started.
[0017] In some embodiments, the backpressure generating device is a
spring
loaded valve which is set to open at a predetermined pressure. The
predetermined
pressure can be set to be the difference between the maximum allowable
pressure in
the supply line and the maximum allowable pressure in the storage vessel.
[0018] In some embodiments, the pump supplying fluid to the end user
from the
storage vessel is a hydraulically actuated pump and the parameter indicative
of the
activation status of the fluid pump is a pressure in a hydraulic circuit of
the pump.
[0019] In some other embodiments the pump is actuated by an electric motor.
In
this case the parameter indicative of the activation status of the pump is the
current
and/or the voltage of the electric motor.
[0020] A method is disclosed for fluidly isolating a storage vessel
from an end
user in a fluid supply system comprising a fluid discharge line and a supply
line for
supplying fluid from the storage vessel to the end user when the end user is
operating,
a recirculation loop for recirculating fluid to the storage vessel, and a
switching
device operable to fluidly connect or to stop fluid flow between the fluid
discharge
line, the supply line and the recirculation loop. The method comprises:
when shutting down, the end user setting the switching device to a position
that
prevents fluid from flowing from the fluid discharge line to the supply line
and allows
fluid flow from the fluid discharge line through the recirculation loop to the
storage
vessel; and
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directing fluid from the fluid discharge line through the recirculation loop
to the
storage vessel when pressure within the recirculation loop is higher than
pressure
within the storage vessel.
[0021]
The method can further comprise detecting an operation state of the
switching device when the end user is started. The step of detecting the
operation
state of the switching device comprises:
a) measuring the pressure in the supply line;
b) measuring the pressure in the fluid discharge line or measuring a
parameter characteristic of an activation circuit of a pump which
supplies fluid to the end user through the fluid discharge line and
supply line;
c) sending signals of the measured pressure in the supply line and of the
measured pressure in the fluid discharge line or of the measured
parameter characteristic of the activation circuit to a controller;
d) determining
that the switching device is in a position that allows fluid
flow from the fluid discharge line through the recirculation loop to the
storage vessel when the end user is started by detecting an increase in
value of the pressure in the fluid discharge line or of the parameter
indicative of the actuation state of the pump and no increase in
measured pressure in the supply line; and
e)
indicating the position of the switching device through an alarm
system.
[0022]
In this method the parameter indicative of the actuation state of the pump
can be a pressure within a hydraulic circuit of a hydraulic pump which
actuates the
pump which supplies fluid to the end user or it can be the current and/or the
voltage
in an electric motor which actuates the pump.
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Brief Description of the Drawings
[0023] Figure 1 is a schematic diagram of a first embodiment of a gaseous
fluid supply
system comprising a subsystem for isolating the storage vessel from the end
user.
[0024] Figure 2 is a schematic diagram of a second embodiment of a gaseous
fluid
supply system comprising a subsystem for isolating the fluid storage vessel
from the end
user.
[0025] Figure 3 is a schematic diagram of a third embodiment of a gaseous
fluid supply
system comprising a subsystem for isolating the fluid storage vessel from the
end user.
[0026] Figure 4 is a schematic diagram of a fourth embodiment of a fluid
supply system
comprising a subsystem for isolating the fluid storage vessel from the end
user.
Detailed Description
[0027] Figure 1, schematically illustrates a first embodiment of fluid supply
system 100
for delivering a gaseous fluid to an end user (not shown). Gaseous fluid
supply system
100 comprises storage vessel 102 which stores gaseous fluid in liquefied form
and pump
105, which in the illustrated embodiment is shown disposed inside liquid space
114 of
storage vessel 102. An advantage of this arrangement is that the pump is
immersed in the
liquefied gas where it is always primed and kept at the same temperature as
the fluid
being pumped, so that there is no delay associated with cooling it to
cryogenic
temperatures before it is able to do useful work. Pump 105 delivers fluid from
storage
vessel 102 to the end user through fluid discharge line 103, which extends
from the
discharge outlet of pump 105 to an inlet of flow switching device 110, and
from flow
switching device 110, on to the end user through supply line 104. Check valve
112 allows
fluid flow in only one direction, to prevent back flow of fluid towards the
discharge outlet
of pump 105. Pump 105 can be actuated by hydraulic drive 115, as illustrated
by the
embodiment shown in Figure 1, or can be driven by other known actuators, such
as an
electric motor. The illustrated embodiment further comprises heat exchanger
116 and
check valve 118 located along fluid discharge line 103 to vaporize and deliver
the fluid
that is pumped from storage vessel 102 in gaseous form to the end user.
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[0028] Gaseous fluid supply system 100 further comprises a subsystem for
isolating
storage vessel 102 from the end user when the end user is shut down and this
subsystem
comprises a switching device 110 and a recirculation loop to connect fluid
discharge line
103 with storage vessel 102. The recirculation loop comprises fluid
recirculation line
108, which in this first embodiment extends from an outlet of switching device
110 to a
junction with pressure relief line 120. Pressure relief line 120 is fluidly
connected to a
location near the top of storage vessel 102 which is normally filled with
vapor, and
referred to in this disclosure as vapor space 122.
[0029] In a preferred embodiment, switching device 110, is a three-way valve,
which can
be a manually actuated valve or a valve with an electronically controlled
actuator that is
commanded by a controller to switch between different operating positions,
under
predetermined operating conditions, for example, when the end user is being
shut down
or started. Switching device 110 receives gaseous fluid through an inlet
connected to
fluid discharge line 103, and is operable to fluidly connect fluid discharge
line 103 with
either supply line 104 (to deliver gaseous fluid to the end user), or with
recirculation line
108 so that fluid discharge line 103 is fluidly connected to storage vessel
102 by way of
recirculation line 108 and a portion of pressure relief line 120. The volume
of storage
vessel 102 is much larger than the volume defined by fluid supply system 100,
so storage
vessel 102 is able to receive the relatively small quantities of gaseous fluid
from the
fluidly connected portion of fluid supply system 100 until the vapor pressure
in the
storage vessel exceeds the predetermined pressure threshold that triggers the
opening of
pressure relief valve 124. The method of isolating the storage vessel from the
end user
when the end user is shut down is described in more detail with respect to the
embodiment shown in Figure 1.
[0030] When the end user is operating, fluid is delivered through fluid
discharge line 103
and switching device 110 is operated to a first position that stops fluid flow
from fluid
discharge line 103 and supply line 104 to recirculation line 108 and that
fluidly connects
fluid discharge line 103 and supply line 104 so that all of the fluid
delivered from storage
vessel 102 flows to supply line 104. When the end user is shut down, switching
device
110 is operated to a second position that fluidly isolates storage vessel 102
and fluid
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discharge line 103 from the end user and from supply line 104 and fluidly
connects fluid
discharge line 103 to recirculation line 108. When switching device 110 is in
the second
position, and the end user is shut down for a prolonged period of time, heat
transfer from
the ambient environment to the fluid remaining in fluid discharge line 103 and
recirculation line 108 can cause the pressure of this gaseous fluid to
increase, in which
case, instead of being immediately vented, it will flow through a portion of
pressure relief
line 120 towards storage vessel 102 where the pressure is usually lower, and
where the
larger volume of stored liquefied fluid normally has some capacity to absorb
small
quantities of warmer higher pressure gas without elevating storage pressure
within the
storage vessel above the predetermined pressure threshold for opening pressure
relief
valve 124.
[0031] The first embodiment described above can be implemented in a gaseous
fuelled
internal combustion engine where fuel, for example, natural gas, is stored in
liquefied
form (LNG) in storage vessel 102 and delivered to the engine through fluid
discharge line
103 and supply line 104.
[0032] LNG fuel storage vessels used to store fuel on board a vehicle are
normally
required to satisfy the local safety standards for the jurisdiction where the
storage vessel
is deployed. Such safety standards normally prescribe tests for surviving
impacts of a
severity reasonably expected, for example, as a result of a vehicle crash.
Accordingly,
such fuel storage vessels are often manufactured with a shrouded space at one
end of the
vessel to protect the piping, valves and other fixtures associated with the
storage vessel
and fuel system. The elements of the presently disclosed system are located
inside the
protective shroud of the associated storage vessel, illustrated as dashed
outline 126 in
Figure 1.
[0033] The first embodiment can further comprise additional features for
detecting the
operation state of switching device 110 when the end user is started, namely
backpressure
device 140, located on recirculation line 108, pressure sensor 142, which
measures the
pressure in supply line 104, and pressure sensor 144, which measures the
pressure in the
hydraulic circuit of hydraulic drive 115. The measurement signals from sensors
142 and
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144 are sent to system controller 130, which is programmed to detect the
operation state
of switching device 110 when the end user is started, as explained below. In
the
illustrated embodiment, backpressure device 140 is a spring loaded valve which
opens at
a predetermined pressure. In other embodiments the backpressure device can be
another
device which opens at a predetermined pressure, for example an electrically
controlled
valve. In the illustrated embodiment, the predetermined pressure for opening
spring
loaded valve 140 is determined to be the difference between the maximum
allowable
pressure in supply line 104 and the maximum allowable pressure in storage
vessel 102, to
ensure that backpressure device 140 opens before the pressure in supply line
104 reaches
the maximum allowable limit while at the same time generating some
backpressure in the
recirculation line when the valve is closed.
[0034] The method of detecting the operation state of the switching device
involves
determining if switching device 110 is in a position that allows fluid
recirculation through
recirculation line 108 and that stops fluid flow from the storage vessel to
the end user
when the end user starts to operate. In such cases, the presence of
backpressure device
140 creates a backpressure when fluid flows through recirculation line 108,
which
triggers a pressure spike in the hydraulic circuit of hydraulic drive 115 if
pump 105 is
activated and if switching device 110 is in the position that blocks fluid
from flowing into
supply line 104, and diverts it to recirculation line 108. If system
controller 130
determines through pressure sensor 144 that there is an increase in the
pressure in the
hydraulic circuit of hydraulic drive 115 and at the same time it records no
change in value
of the pressure in supply line 104, system controller 130 is able to determine
that
switching device 110 is set in the wrong position for starting the end user,
and system
controller 130 can activate an alarm system, for example through the OBD (on-
board
diagnostics) system to alert the operator to set switching device 110 to the
position that
allows fluid flow from the storage vessel to the end user (and that blocks
fluid flow
through recirculation line 108). When switching device 110 is a manually
operated valve
the operator will know to stop the start-up sequence for the end user, until
the position of
switching device 110 is changed. If the alarm system is activated and
switching device
110 is one that is normally electronically operated, then the operator will
need to
troubleshoot the automatic control of the switching device.
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[0035] In some other embodiments, pressure sensor 144 can be replaced by a
pressure
sensor placed in fluid discharge line 103, for example downstream of check
valve 118,
which can have the same function as pressure sensor 144 and can sense a
pressure spike
in the fluid discharge line indicating that fluid is supplied from storage
vessel 102 to fluid
discharge line 103 when the end user is started but that switching device 110
is set to a
wrong position allowing fluid communication between fluid discharge line 103
and
recirculation line 108 and stopping fluid communication between fluid
discharge line 103
and supply line 104.
[0036] Other embodiments of the present apparatus are illustrated in Figures
2, 3 and 4.
These embodiments have many elements that are functionally equivalent to like
elements
of the first embodiment presented in Figure 1, and such "like elements" are
identified by
like-numbered reference numbers.
[0037] With reference now to the second embodiment, shown in Figure 2, fluid
supply
system 200 comprises storage vessel 202 which stores a gaseous fluid in liquid
form and
pump 205 which is immersed in liquid space 214 of the storage vessel and which
supplies
fluid through fluid discharge line 203 and supply line 204 to an end user. In
this
embodiment, pump 205 is actuated by an electric motor 215 as illustrated.
Similar to the
system illustrated in the first embodiment, the fluid supply system of Figure
2 comprises
a heat exchanger 216 and one-way check valves 212 and 218 which have the same
function as in the embodiment illustrated in Figure 1. The supply system in
Figure 2
further comprises a vapor supply line 228 provided with a one-way check valve
232.
Through this vapor supply line fluid can be supplied from vapor space 222 of
the storage
vessel to fluid discharge line 203 when the pressure in the vapor space meets
the
demands required by the operation of the end user. As illustrated, vapor
supply line 228
is fluidly connected to storage vessel 202 through a portion of pressure
relief line 220.
[0038] The subsystem for isolating the storage vessel from the end user
comprises a
recirculation loop which in the present embodiment comprises recirculation
line 208 and
a switching device which in this embodiment is illustrated as three-way valve
210 which
is operable to connect fluid discharge line 203, supply line 204 and
recirculation line 208.
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In this embodiment, recirculation line 208 is connected directly to vapor
space 222 of
storage vessel 202. Pressure relief line 220 is also connected to storage
vessel 202 to
allow fluid to be vented through pressure relief valve 224 when the pressure
within the
storage vessel exceeds a predetermined allowable limit. Fluid vented from the
system can
be vented to the atmosphere, but it is preferably captured, burned or
otherwise oxidized.
The elements of the second embodiment of the present system can be located in
a
protective shroud of the storage vessel illustrated with dashed outline 226.
[0039] For the embodiment illustrated in Figure 2, the method of isolating the
storage
vessel from the end user when the end user is shut down is similar with the
method
described for the first embodiment, whereby at shut-down, three-way valve 210
is set to a
position which blocks fluid flow from fluid discharge line 203 to supply line
104 and to
the end user, thereby fluidly isolating the storage vessel from the end user,
and allowing
fluid flow between fluid discharge line 203 and recirculation line 208 such
that fluid
remaining in fluid discharge line 203 and in recirculation line 208 when the
end user is
shut down can be returned directly to vapor space 222 of storage vessel 202
when the
fluid pressure in recirculation line 208 becomes higher than the pressure in
the storage
vessel. Similar to the first embodiment, fluid is vented to the atmosphere or
is preferably
redirected elsewhere through pressure relief line 220 only when the pressure
within the
storage vessel rises over an admissible predetermined limit. Vented fluid can
be captured
in a separate vessel to be used later or can be burned or otherwise oxidized.
[0040] The second embodiment can further comprise additional optional features
for
detecting the operation state of switching device 210 when the end user starts
to operate.
Backpressure device 240 is located on recirculation line 208 and allows fluid
flow from
fluid discharge line 203 to storage vessel 202 when the pressure within
recirculation line
208 is higher than the pressure within the storage vessel. Pressure in supply
line 204 is
monitored by pressure sensor 242 which sends the measurement signals to system
controller 230. Current and voltage feedback from electric motor 215 of pump
205 are
collected and communicated through sensor 244 to system controller 230. The
current
and voltage of electric motor 215 represent parameters which are
characteristic of the
activation status of pump 205.
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[0041] The method of detecting the operation state of switching device 210 in
this second
embodiment is similar with the method described in relation with the
embodiment
illustrated in Figure 1. System controller 230 receives signals from pressure
sensor 242
and from sensor 244 regarding the pressure in the supply line and,
respectively, regarding
the current and/or voltage of the electric motor. The presence of backpressure
device 240
creates a backpressure when fluid flows through recirculation line 208, which
triggers a
spike in the voltage and/or current of electric motor 215 if pump 205 is
activated when
the end user is started and if switching device 210 is in the position that
blocks fluid from
flowing into supply line 204 and diverts it to recirculation line 208. If
system controller
230 determines that there is an increase in current and/or voltage of electric
motor 215
and at the same time it records no pressure increase in supply line 204,
system controller
230 is able to determine that switching device 210 is set in the wrong
position for starting
the end user. This operation state is indicated to an operator, who can then
set the
switching device 210 to the desired position manually or can troubleshoot the
automatic
control of the switching device to remedy the situation.
[0042] Another embodiment of the present gaseous fluid supply system is
illustrated in
Figure 3. As in the previous embodiments, in this third embodiment the
subsystem for
isolating storage vessel 302 from the end user comprises recirculation line
308 and a
switching device illustrated as three-way valve 310. The gaseous fluid supply
system 300
further comprises fluid discharge line 303 connected to the discharge outlet
of an external
pump 305 and supply line 304. When the end user is operating, three-way valve
310 is set
in a first position and fluid is supplied to the end user from liquid space
314 of storage
vessel 302 through fluid discharge line 303 provided with one way check valve
312
connected to the discharge outlet of external pump 305 and through fluid
supply line 304.
In this embodiment, pump 305 is an external pump placed outside of storage
vessel 302
which is activated by hydraulic drive 315. Vapor can also be supplied from
vapor space
322 inside storage vessel 302 to fluid discharge line 303 through vapor supply
line 328,
provided with one way check valve 332. During the operation of the end user,
fluid in a
gaseous state can be supplied from the vapor space 322 to the end user through
vapor
supply line 328 and through fluid discharge line 303 when the pressure within
vapor
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space 322 meets the required operation pressure of the end user as determined
by the
system controller.
[0043] Recirculation line 308 is fluidly connected to three-way valve 310 and
to pressure
relief line 320 which is provided with pressure relief valve 324. The
recirculation loop in
this embodiment comprises recirculation line 308 and a portion of pressure
relief line 320
which fluidly connects recirculation line 308 to storage vessel 302.
[0044] In this third embodiment, heat exchanger 316 and one-way check valve
318
which prevents any fluid backflow to the heat exchanger are placed in fluid
supply line
304 and therefore some of the system components located upstream of the heat
exchanger, for example switching device 310, have to be compatible to work in
cryogenic conditions corresponding to the temperature of the fluid being
delivered from
the cryogenic space of storage vessel 302.
[0045] The components to the supply system can be enclosed in a shroud 326 of
the
storage vessel.
[0046] The operation of this third embodiment is similar to the operation of
the other
embodiments described herein. When the end user is shut-down, three-way valve
310 is
set to a second position which isolates the storage vessel from the end user
and at the
same time allows fluid communication between fluid discharge line 303 and
recirculation
line 308 such that fluid from the supply line can be returned to storage
vessel 302 when
the pressure of the fluid in the recirculation line increases and becomes
higher than the
pressure in the storage vessel. Similar to the first embodiment, fluid is
vented through
pressure relief line 320 only when the pressure within the storage vessel
rises over an
admissible predetermined limit. In this embodiment, a relatively large portion
of the fluid
returned to the storage vessel can be in liquid state. Three-way valve 310 can
be a manual
valve which is switched by an operator between the two positions, or it can be
an
automatic valve which is switched between the two positions by the system
controller.
[0047] Similar to the other embodiments, the system illustrated in Figure 3
can comprise
some additional components for detecting the position of switching device 310.
The
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system can comprise a backpressure device 340, illustrated as a spring loaded
valve,
pressure sensor 342 for measuring the pressure in supply line 304, and
pressure sensor
344 which monitors the pressure within the hydraulic drive 315 which actuates
pump
305. Controller 330 receives the measured signals from sensors 342 and 344.
[0048] The method of detecting the operation state of switching device 310
when the end
user is started in the system illustrated in Figure 3 is similar to the method
described in
relation to Figure 1. When pump 305 strokes and switching device 310 is set to
a position
that allows fluid flow from fluid discharge line 303 to recirculation line
308, spring
loaded valve 340 generates a backpressure in recirculation line 308.
Controller 330
monitors the signals received from sensors 342 and 344. If, when the end user
is started,
there is a spike in pressure in the hydraulic circuit of hydraulic pump 315
and at the same
time there is no pressure increase in supply line 304, controller 330
determines that
switching device 310 is set in a position which stops fluid flow from fluid
discharge line
303 to the end user and allows fluid flow through recirculation line 308. This
operation
state is indicated to the vehicle driver, for example through an OBD (on-board
diagnostics) system and the situation can be corrected.
[0049] Figure 4 illustrates yet another embodiment of the present system.
Gaseous fluid
supply system 400 comprises some similar components to the previously
described
embodiments, having similar reference numbers which will not be described here
entirely, if at all. The difference between this fourth embodiment and the
previous
embodiments is that the switching device which is operable to connect fluid
discharge
line 403, supply line 404 and recirculation line 408 comprises two-way valves
406 and
407. Two-way valve 406 is positioned on supply line 404 and two-way valve 407
is
positioned on recirculation line 408. These two two-way valves can be actuated
manually
or by the system controller 430.
[0050] When the end user is started, two-way valve 406 is opened to allow
fluid flow
from liquid space 414 of storage vessel 402 and pump 405 to the end user
through fluid
discharge line 403 provided with check valve 418 and through supply line 404.
The
storage vessel can be isolated from the end user as further explained here.
When the end
CA 02860682 2015-01-22
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user is shut down, two-way valve 406 is closed to stop fluid flow from storage
vessel 402
to the end user, and two-way valve 407 is opened to allow fluid flow from
fluid discharge
line 403 to recirculation line 408. Similarly to the previous embodiments,
fluid from fluid
discharge line 403 and from recirculation line 408 can be returned to vapor
space 422 of
storage vessel 402 through a portion of pressure relief line 420 when the
pressure in
recirculation line 408 is higher than the pressure in the storage vessel.
Fluid is vented
through pressure relief line 420 and pressure relief valve 424 only when the
pressure
within the storage vessel rises over an admissible predetermined limit. Vented
fluid can
be captured in an auxiliary vessel or can be oxidized or burned.
[0051] The system illustrated in Figure 4 further comprises heat exchanger 416
positioned on fluid discharge line 403 and vapor supply line 428 and one way
check
valve 432 through which vapor can be supplied from vapor space 422 to fluid
discharge
line 403 under predetermined conditions. All the elements of the fluid supply
system can
be enclosed in shroud 426 of the storage vessel for better protection.
[0052] In all the described embodiments, the system can be a fuel supply
system of a
gaseous fuelled internal combustion engine which can be the prime mover for a
vehicle.
The gaseous fuel can be natural gas which is stored in liquefied form in a LNG
tank.
[0053] The present invention has been described with regard to a plurality of
illustrative
embodiments. However, it will be apparent to persons skilled in the art that a
number of
variations and modifications can be made without departing from the scope of
the
invention as defined in the claims.
