U.S. patent application number 14/062398 was filed with the patent office on 2015-04-30 for fuel separation via fuel vapor management systems.
This patent application is currently assigned to Ford Global Technologies, LLC. The applicant listed for this patent is Ford Global Technologies, LLC. Invention is credited to James Eric Anderson, Thomas G. Leone.
Application Number | 20150114370 14/062398 |
Document ID | / |
Family ID | 52010907 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150114370 |
Kind Code |
A1 |
Leone; Thomas G. ; et
al. |
April 30, 2015 |
FUEL SEPARATION VIA FUEL VAPOR MANAGEMENT SYSTEMS
Abstract
Systems and methods for separating higher octane fuel from a
fuel mixture are presented. In one example, fuel vapors may be
limited or constrained from migrating to fuel tanks storing lower
octane fuels. The systems may vent fuel vapors from a plurality of
fuel tanks to a single fuel vapor storage canister. Alternatively,
the systems may vent fuel vapors from the plurality of fuel tanks
to a plurality of fuel vapor storage canisters.
Inventors: |
Leone; Thomas G.;
(Ypsilanti, MI) ; Anderson; James Eric; (Dearborn,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies, LLC |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies,
LLC
Dearborn
MI
|
Family ID: |
52010907 |
Appl. No.: |
14/062398 |
Filed: |
October 24, 2013 |
Current U.S.
Class: |
123/575 ;
123/519; 123/520 |
Current CPC
Class: |
F02D 41/0025 20130101;
F02M 37/0088 20130101; F02D 19/081 20130101; F02D 41/02 20130101;
F02M 25/089 20130101; F02D 13/0265 20130101; F02D 19/084 20130101;
Y02T 10/30 20130101; F02D 19/0665 20130101; Y02T 10/36 20130101;
F02D 19/0649 20130101; F02M 43/00 20130101; F02M 69/044 20130101;
F02D 41/0032 20130101; Y02T 10/16 20130101; F01N 5/02 20130101;
F02D 19/0668 20130101; F02D 41/0042 20130101; F02M 25/0854
20130101; Y02T 10/12 20130101; F02M 25/0836 20130101 |
Class at
Publication: |
123/575 ;
123/519; 123/520 |
International
Class: |
F02D 19/08 20060101
F02D019/08; F02D 41/02 20060101 F02D041/02; F02M 25/08 20060101
F02M025/08 |
Claims
1. A fuel storage system, comprising: a first fuel tank; a second
fuel tank; a first fuel vapor storage canister; a second fuel vapor
storage canister; a first conduit coupled to the first fuel tank
and the first fuel vapor storage canister; a second conduit not
coupled to the first conduit, the second conduit coupled to the
first fuel tank and the second fuel vapor storage canister; and a
valve positioned along the second conduit.
2. The fuel storage system of claim 1, where the first fuel tank
stores a fuel having a higher octane number than a fuel stored in
the second fuel tank, and where the first conduit provides fluidic
communication between the first fuel tank and the first fuel vapor
storage canister, and where the second conduit provides fluidic
communication between the first fuel tank and the second fuel vapor
storage canister.
3. The fuel storage system of claim 1, further comprising a third
conduit coupled to the second fuel tank and the second fuel vapor
storage canister.
4. The fuel storage system of claim 3, further comprising a valve
positioned along the third conduit.
5. The fuel storage system of claim 4, further comprising a fourth
conduit, the fourth conduit coupled to an engine intake system and
the second fuel vapor storage canister.
6. The fuel storage system of claim 1, further comprising a
controller including executable instructions stored in
non-transitory memory for limiting return of fuel vapors from the
second fuel vapor storage canister to the second fuel tank.
7. The fuel storage system of claim 1, further comprising a conduit
coupled to an engine waste heat exchanger and one or more of the
two or more fuel tanks.
8. A fuel storage system, comprising: two or more fuel tanks, a
first fuel tank of the two or more fuel tanks storing a fuel having
a higher octane number than a remainder of the two or more fuel
tanks; a conduit coupled to the first fuel tank and one of the
remainder of the two or more fuel tanks; and a check valve
positioned along the conduit biased to limit flow from the first
fuel tank to the remainder of the two or more fuel tanks.
9. The fuel storage system of claim 8, further comprising a fuel
vapor storage canister and a conduit coupled to the fuel vapor
storage canister and the first fuel tank, and where the conduit
coupled to the fuel vapor storage canister is a sole conduit
coupled to the fuel vapor storage canister and the two or more fuel
tanks.
10. The fuel storage system of claim 9, further comprising a
conduit coupled to an engine waste heat exchanger and one or more
of the two or more fuel tanks.
11. The fuel storage system of claim 9, further comprising a fuel
pump in fluidic communication with the first fuel tank and a first
fuel injector.
12. The fuel storage system of method of claim 11, further
comprising a fuel pump in fluidic communication with one of the two
or more fuel tanks other than the first fuel tank and a second fuel
injector.
13. A fuel storage system, comprising: a first fuel tank storing a
first fuel; a second fuel tank storing a second fuel, the second
fuel including a lower octane number than the first fuel; a first
fuel vapor storage canister in fluidic communication with the first
fuel tank; and a controller including executable instructions
stored in non-transitory memory for limiting flow of fuel vapors
from the first fuel tank to the second fuel tank.
14. The fuel storage system of claim 13, further comprising a
valve, and where limiting flow of fuel vapors is achieved via
closing the valve.
15. The fuel storage system of claim 13, further comprising a first
conduit coupled to the first fuel vapor storage canister and the
first fuel tank, and a second conduit coupled to the first fuel
vapor storage canister and the second fuel tank.
16. The fuel storage system of claim 13, further comprising a
second fuel vapor storage canister, the second fuel vapor storage
canister in fluidic communication with the second fuel tank and not
in fluidic communication with the first fuel tank outside of an
engine intake.
17. The fuel storage system of claim 16, further comprising two
fuel vapor purge valves, a first fuel vapor purge valve of the two
fuel vapor purge valves in fluidic communication with the first
fuel vapor storage canister and the engine intake.
18. The fuel storage system of claim 17, further comprising a
second fuel vapor purge valve of the two fuel vapor purge valves in
fluidic communication with the second fuel vapor storage canister
and the engine intake.
19. The fuel storage system of claim 13, further comprising
additional controller instructions for allowing flow of fuel vapors
from the second fuel tank to the first fuel tank during diurnal
cooling of the fuel vapor storage system.
20. The fuel storage system of claim 13, further comprising
additional controller instructions to inject condensed fuel in the
first fuel tank to an engine, and where the condensed fuel
originated from the second fuel tank.
Description
FIELD
[0001] The present description relates to a system and methods for
separating a higher octane fuel from a lower octane fuel mixture
and maintaining separation of the higher and lower octane fuels in
the presence of fuel system diurnal heating and cooling. The
systems may be particularly useful for vehicles that include two or
more fuel tanks
BACKGROUND AND SUMMARY
[0002] An engine may be supplied different types of fuel during
different engine operating conditions to enhance engine performance
and/or fuel economy. For example, an engine may be supplied
gasoline via a first fuel injector and ethanol via a second fuel
injector. The two fuels may be supplied from a fuel mixture that is
separated into two fuels or via filling different fuel tanks with
different fuels.
[0003] United States of America Patent Publication 2008/000633
describes systems to handle fuel tank vapors for multiple fuel
tanks However, in the systems described by publication 2008/000633
fuel vapors of higher octane fuels may condense in fuel tanks
holding or storing lower octane fuel, and vice versa. Consequently,
the higher octane fuel may not be best utilized, or alternatively,
the higher octane fuel may have to be separated from the lower
octane fuel so that it may be utilized. However, parasitic losses
may increase due to energy being lost from separating the higher
octane fuel from the lower octane fuel.
[0004] The inventors herein have recognized the above-mentioned
disadvantages and have developed a fuel storage system, comprising:
a first fuel tank; a second fuel tank; a first fuel vapor storage
canister; a second fuel vapor storage canister; a first conduit
coupled to the first fuel tank and the first fuel vapor storage
canister; a second conduit not coupled to the first conduit, the
second conduit coupled to the first fuel tank and the second fuel
vapor storage canister; and a valve positioned along the second
conduit.
[0005] By not allowing fluidic communication between fuel tank
vapor paths, it may be possible to prevent higher octane fuel
vapors from condensing and mixing with lower octane fuel in a fuel
tank storing lower octane fuel. Further, fuel tank vapor paths may
be constructed such that fuel vapors originating from fuel tanks
storing fuel having a lower octane number may be directed to a fuel
tank storing fuel having a higher octane number. In this way, high
octane fuel vapors that were produced via diurnal fuel system
heating may be captured in a fuel tank storing a fuel having a
higher octane number so that higher octane fuel vapors may condense
into a higher octane liquid fuel. Additionally, parasitic losses
associated with separating higher octane fuel from a lower octane
fuel mixture may be reduced by taking advantage of diurnal heating
so that separating higher octane fuel from a lower octane fuel
mixture may not require engine work.
[0006] The present description may provide several advantages. In
particular, the systems described may reduce parasitic engine
losses that decrease engine fuel economy. Additionally, the systems
may provide for more efficient use of fuel vapors. Further still,
the systems described may be applied to systems that include more
than two fuel tanks and two types of fuel.
[0007] The above advantages and other advantages, and features of
the present description will be readily apparent from the following
Detailed Description when taken alone or in connection with the
accompanying drawings.
[0008] It should be understood that the summary above is provided
to introduce in simplified form a selection of concepts that are
further described in the detailed description. It is not meant to
identify key or essential features of the claimed subject matter,
the scope of which is defined uniquely by the claims that follow
the detailed description. Furthermore, the claimed subject matter
is not limited to implementations that solve any disadvantages
noted above or in any part of this disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The advantages described herein will be more fully
understood by reading an example of an embodiment, referred to
herein as the Detailed Description, when taken alone or with
reference to the drawings, where:
[0010] FIG. 1 is a schematic diagram of an engine;
[0011] FIGS. 2-6 show example vehicle fuel systems; and
[0012] FIGS. 7 and 8 show an example method for operating a fuel
system of a vehicle.
DETAILED DESCRIPTION
[0013] The present description is related to controlling fuel
vapors of a vehicle. The fuel vapors may be used in an engine as
shown in FIG. 1. The engine may be supplied fuel from one or more
fuel tanks as shown in the fuel systems of FIGS. 2-6. Component
fuels may be separated from a fuel mixture comprising two or more
fuels via diurnal heating and cooling of vehicle fuel systems. The
vehicle fuel systems may be arranged to allow higher octane fuel
vapors to condense only in fuel tank storing a higher octane fuel
so that the possibility of unintended fuel mixing may be reduced.
The method of FIGS. 7 and 8 operates the vehicle fuel system in a
way that reduces the possibility of mixing fuels via the
evaporative emissions section of the vehicle fuel system.
[0014] Referring to FIG. 1, internal combustion engine 10,
comprising a plurality of cylinders, one cylinder of which is shown
in FIG. 1, is controlled by electronic engine controller 12.
Electrical connections between controller 12 and the various
sensors and actuators are indicated by dashed lines.
[0015] Engine 10 includes combustion chamber 30 and cylinder walls
32 with piston 36 positioned therein and connected to crankshaft
40. Flywheel 97 and ring gear 99 are coupled to crankshaft 40.
Starter 96 includes pinion shaft 98 and pinion gear 95. Pinion
shaft 98 may selectively advance pinion gear 95 to engage ring gear
99. Starter 96 may be directly mounted to the front of the engine
or the rear of the engine. In some examples, starter 96 may
selectively supply torque to crankshaft 40 via a belt or chain. In
one example, starter 96 is in a base state when not engaged to the
engine crankshaft. Combustion chamber 30 is shown communicating
with intake manifold 44 and exhaust manifold 48 via respective
intake valve 52 and exhaust valve 54. Each intake and exhaust valve
may be operated by an intake cam 51 and an exhaust cam 53. The
position of intake cam 51 may be determined by intake cam sensor
55. The position of exhaust cam 53 may be determined by exhaust cam
sensor 57. Intake cam 51 and exhaust cam 53 may be moved relative
to crankshaft 40.
[0016] Fuel injector 66 is shown positioned to inject fuel directly
into cylinder 30, which is known to those skilled in the art as
direct injection. Alternatively, fuel may be injected to an intake
port, which is known to those skilled in the art as port injection.
Fuel injector 66 delivers liquid fuel in proportion to the pulse
width of signal from controller 12. Fuel is delivered to fuel
injector 66 by a fuel system 175 shown in greater detail in FIGS. 2
and 3. In addition, intake manifold 44 is shown communicating with
optional electronic throttle 62 which adjusts a position of
throttle plate 64 to control air flow from air intake 42 to intake
manifold 44. In one example, a low pressure direct injection system
may be used, where fuel pressure can be raised to approximately
20-30 bar. Alternatively, a high pressure, dual stage, fuel system
may be used to generate higher fuel pressures. In some examples,
throttle 62 and throttle plate 64 may be positioned between intake
valve 52 and intake manifold 44 such that throttle 62 is a port
throttle.
[0017] Distributorless ignition system 88 provides an ignition
spark to combustion chamber 30 via spark plug 92 in response to
controller 12. Universal Exhaust Gas Oxygen (UEGO) sensor 126 is
shown coupled to exhaust manifold 48 upstream of catalytic
converter 70. Alternatively, a two-state exhaust gas oxygen sensor
may be substituted for UEGO sensor 126.
[0018] Converter 70 can include multiple catalyst bricks, in one
example. In another example, multiple emission control devices,
each with multiple bricks, can be used. Converter 70 can be a
three-way type catalyst in one example.
[0019] Controller 12 is shown in FIG. 1 as a conventional
microcomputer including: microprocessor unit 102, input/output
ports 104, read-only memory 106 (e.g., non-transitory memory),
random access memory 108, keep alive memory 110, and a conventional
data bus. Controller 12 is shown receiving various signals from
sensors coupled to engine 10, in addition to those signals
previously discussed, including: engine coolant temperature (ECT)
from temperature sensor 112 coupled to cooling sleeve 114; a
position sensor 134 coupled to an accelerator pedal 130 for sensing
force applied by driver 132; a measurement of engine manifold
pressure (MAP) from pressure sensor 122 coupled to intake manifold
44; an engine position sensor from a Hall effect sensor 118 sensing
crankshaft 40 position; a measurement of air mass entering the
engine from sensor 120; brake pedal position from brake pedal
position sensor 154 when driver 132 applies brake pedal 150; a
measurement of ambient temperature via temperature sensor 137; and
a measurement of throttle position from sensor 58. Barometric
pressure may also be sensed (sensor not shown) for processing by
controller 12. In a preferred aspect of the present description,
engine position sensor 118 produces a predetermined number of
equally spaced pulses every revolution of the crankshaft from which
engine speed (RPM) can be determined.
[0020] In some examples, the engine may be coupled to an electric
motor/battery system in a hybrid vehicle. Further, in some
examples, other engine configurations may be employed, for example
a diesel engine.
[0021] During operation, each cylinder within engine 10 typically
undergoes a four stroke cycle: the cycle includes the intake
stroke, compression stroke, expansion stroke, and exhaust stroke.
During the intake stroke, generally, the exhaust valve 54 closes
and intake valve 52 opens. Air is introduced into combustion
chamber 30 via intake manifold 44, and piston 36 moves to the
bottom of the cylinder so as to increase the volume within
combustion chamber 30. The position at which piston 36 is near the
bottom of the cylinder and at the end of its stroke (e.g. when
combustion chamber 30 is at its largest volume) is typically
referred to by those of skill in the art as bottom dead center
(BDC). During the compression stroke, intake valve 52 and exhaust
valve 54 are closed. Piston 36 moves toward the cylinder head so as
to compress the air within combustion chamber 30. The point at
which piston 36 is at the end of its stroke and closest to the
cylinder head (e.g. when combustion chamber 30 is at its smallest
volume) is typically referred to by those of skill in the art as
top dead center (TDC). In a process hereinafter referred to as
injection, fuel is introduced into the combustion chamber. In a
process hereinafter referred to as ignition, the injected fuel is
ignited by known ignition means such as spark plug 92, resulting in
combustion. During the expansion stroke, the expanding gases push
piston 36 back to BDC. Crankshaft 40 converts piston movement into
a rotational torque of the rotary shaft. Finally, during the
exhaust stroke, the exhaust valve 54 opens to release the combusted
air-fuel mixture to exhaust manifold 48 and the piston returns to
TDC. Note that the above is shown merely as an example, and that
intake and exhaust valve opening and/or closing timings may vary,
such as to provide positive or negative valve overlap, late intake
valve closing, or various other examples.
[0022] Referring now to FIG. 2, a first example fuel system 175 is
shown in detail. The fuel system of FIG. 2 may supply fuel to
engine 10 shown in detail in FIG. 1. The system of FIG. 2 may be
operated according to the method of FIG. 7. Fuel system components
and fluidic conduits are shown as solid lines and electrical
connections are shown as dashed lines. The conduits represented by
solid lines in FIGS. 2-6 provide fluidic communication between
devices linked by the conduits. Further, the conduits are coupled
to the devices from which and to which they lead.
[0023] Fuel system 175 includes a fuel vapor storage canister 202
for storing fuel vapors. Fuel system 175 includes carbon 203 for
storing and releasing fuel vapors. Fuel vapors stored in fuel vapor
storage canister 202 may have a higher octane number than liquid
fuel stored in one or more fuel tanks that supply fuel vapors to
fuel vapor storage canister 202. Fuel vapor storage canister 202 is
shown including atmospheric vent 205 which allows air to flow into
and out of fuel vapor storage canister 202. Fuel vapors may be
supplied to fuel vapor storage canister 202 via conduit 208 and
fuel tanks 230, 232, and 234. Although three fuel tanks are shown,
alternative examples may include fewer or additional fuel tanks
without departing from the scope or intent of this description.
Fuel vapors may be purged via purge valve 204 which allows fluidic
communication between fuel vapor storage canister 202 and engine
intake manifold 44 or intake 42 via conduit 207. Fuel system
connections between fuel tanks 230, 232, 234 and fuel vapor storage
canister 202 are minimized between fuel tanks 230, 232, 234 and
conduit 208.
[0024] Engine 10 includes a first fuel rail 220 that supplies fuel
to direct fuel injector 66. Engine 10 also includes a second fuel
rail 221 that supplies fuel to port fuel injector 67. Fuel vapors
may be inducted into intake manifold 44 or intake 42 when intake
manifold pressure is below atmospheric pressure. In some examples,
engine coolant or exhaust gases from exhaust manifold 48 may
transfer heat energy to a fluid via heat exchanger 275. The fluid
may be directed to fuel tanks 230, 232, and 234 via conduit 240 and
pump 250. The heated fluid may increase the temperature of fuels
231, 233, and 235 to increase a rate of vapor separation from the
respective fuels.
[0025] In one example, fuel tank 230 is a fuel tank that holds a
higher octane fuel. Fuel tank 232 holds a middle level octane fuel
that has an octane number between the fuel stored in fuel tank 230
and the fuel stored in fuel tank 234. Fuel tank 234 holds a lower
level octane fuel that has an octane number that is less than the
fuels stored on fuel tanks 230 and 232. Fuel tank 230 supplies fuel
liquid 231 to fuel rail 220 and direct injector 66 via fuel pump
252. Fuel tank 232 supplies liquid fuel 233 to fuel rail 220 and
direct injector 66 via fuel pump 253. Fuel tank 234 supplies liquid
fuel 235 to fuel rail 221 and port injector 67 via fuel pump
254.
[0026] Fuel vapors from fuel tank 230 may be directed to fuel vapor
storage canister 202 from fuel tank 230 via conduit 208. Fuel
vapors from fuel tank 232 may be directed to fuel vapor storage
canister 202 from fuel tank 232 via conduit 208. Fuel vapors from
fuel tank 234 may be directed to fuel vapor storage canister 202
from fuel tank 234 via conduit 208. Thus, fuel vapors from fuel
tanks 230, 232, and 234 may flow to fuel vapor storage canister 202
via conduit 208.
[0027] Controller 12 may receive inputs from the sensors described
in FIG. 1 as well as sensors 241. In one example, sensors 241 may
be temperature sensors. Alternatively, sensors 241 may be pressure
sensors. Controller 12 also activates and deactivates purge valve
204 in response to fuel system and engine operating conditions.
Additionally, controller 12 selectively operates pump 250 to
increase the production of fuel tank vapors.
[0028] In one example, the system of FIG. 2 operates according to
the method of FIG. 7 via executable instructions stored in
non-transitory memory of controller 12. While engine 10 is
operating, fuel vapors from fuel tanks 230, 232, and 234 may be
stored in fuel vapor storage canister 202 in response to
temperatures in the fuel tanks increasing, which motivates fuel
vapor flow from each of fuel tanks 230, 232, and 234 to fuel vapor
storage canister 202.
[0029] Fuel vapors from fuel tanks 230, 232, and 234 push air out
of atmospheric vent 205 and are stored by carbon 203 when
temperature and/or pressure in fuel tanks 230, 232, and 234 is
increasing. If engine 10 is operating while vapors are being
directed to fuel vapor storage canister 202, fuel vapor purge valve
204 may be opened so that fuel vapors are drawn into and combusted
in engine 10. If engine 10 is not operating or if fuel vapor purge
valve 204 is closed, fuel vapor may flow into fuel vapor storage
canister 202 if temperature and/or pressure in one or more of fuel
tanks 230, 232, and 234 increases such that fuel vapors flow to and
are stored in fuel vapor storage canister 202.
[0030] On the other hand, if engine 10 is not operating or if fuel
vapor purge valve is closed while temperature and/or pressure in
fuel tanks 230, 232, and 234 are decreasing, fuel vapors from fuel
vapor canister 202 may condense in each of fuel tanks 230, 232, and
234. Thus, the fuel system shown in FIG. 2 provides minimal
connections between fuel tanks 230, 232, and 234; however, the
configuration of FIG. 2 may allow higher octane fuel vapors to
condense in fuel tanks holding or storing lower octane fuel.
Consequently, diurnal fuel separation that may occur during fuel
system heating may be made less efficient by diurnal fuel mixing
that may occur during fuel system cooling. Similarly, higher octane
fuel that may be separated via engine waste heat may be remixed in
fuel tanks storing lower octane fuels.
[0031] Referring now to FIG. 3, an alternative example fuel system
175 is shown in detail. The fuel system of FIG. 3 may supply fuel
to engine 10 shown in detail in FIG. 1. The system of FIG. 3 may be
operated according to the method of FIG. 7. Fuel system components
and fluidic conduits that allow fluidic communication are shown as
solid lines while electrical connections are shown as dashed lines.
Fuel system devices and components shown in FIG. 3 that have the
same numerical identifiers as devices and components shown in FIG.
2, are equivalent and operate as described in FIG. 2. For example,
fuel tank 230 stores a higher octane fuel than fuel tanks 232 and
234. Therefore, the descriptions of fuel system components that are
described in FIG. 2 are omitted for the sake of brevity.
[0032] In this example, fuel tanks 230, 232, and 234 are not
coupled to a lone conduit that communicates with fuel vapor storage
canister 202. Rather, fuel tanks 230, 232, and 234 are coupled in a
cascaded one coupling after the other coupling configuration. In
particular, fuel tank 234 is coupled to only to fuel tank 232 via
conduit 330 and conduit 322. However, in some examples fuel tank
234 may be coupled to only fuel tank 230 via conduit 330 and
optional conduit 321. Further, conduit 330 includes check valve 312
which limits and/or stops flow of fuel vapors from fuel tank 232 to
fuel tank 234, but allows fuel vapors to flow from fuel tank 234 to
fuel tank 232. The fuel system of FIG. 3 also includes conduit 332
which couples only fuel tank 232 to fuel tank 230. Conduit 332 also
includes check valve 310, which limits and/or stops flow of fuel
vapors from fuel tank 230 to fuel tank 232, but allows fuel vapors
to flow from fuel tank 232 to fuel tank 231. Conduit 308 solely
couples fuel tank 230 to fuel vapor storage canister 202.
[0033] Thus, fuel vapors separated from fuel tank 234 during
diurnal fuel system heating or via engine waste heat may be routed
to fuel tank 232, or optionally fuel tank 230, without fuel vapors
being returned to fuel tank 234. Likewise, fuel vapors separated
from fuel tank 232 and fuel vapors from fuel tank 234 during
diurnal fuel system heating or via engine waste heat may be routed
to fuel tank 230 without fuel vapors being returned to fuel tank
232. Fuel vapors may flow back and forth between fuel tank 230 and
fuel vapor storage canister 202 during diurnal heating and cooling.
In this way, fuel vapors from fuel tanks of a fuel system may be
limited or restricted from returning to a fuel tank from which the
fuel vapors originated after the fuel vapors leave the fuel tank
from which they originated.
[0034] Referring now to FIG. 4, another alternative example fuel
system 175 is shown in detail. The fuel system of FIG. 4 may supply
fuel to engine 10 shown in detail in FIG. 1. The system of FIG. 4
may be operated according to the method of FIG. 7. Fuel system
components and fluidic conduits that allow fluidic communication
are shown as solid lines while electrical connections are shown as
dashed lines. Fuel system devices and components shown in FIG. 4
that have the same numerical identifiers as devices and components
shown in FIG. 2, are equivalent and operate as described in FIG. 2.
For example, fuel tank 230 stores a higher octane fuel than fuel
tanks 232 and 234. Therefore, the descriptions of fuel system
components that are described in FIG. 2 are omitted for the sake of
brevity.
[0035] In this example, fuel system 175 includes three fuel vapor
storage canisters 402, 406, and 416; however the number of fuel
vapor storage canisters may increase or decrease if the number of
fuel tanks is increased or decreased as is mentioned in the system
of FIG. 2. Each fuel vapor storage canister includes carbon 403 for
storing fuel vapors. First fuel vapor storage canister 402 includes
an atmospheric vent 405. Additionally, fuel vapor storage canisters
406 and 416 include respective atmospheric vents 407 and 417. First
fuel vapor storage canister 402 is shown in direct fluidic
communication with fuel tank 230 via conduit 488.
[0036] Fuel vapor storage canister 402 may be purged of fuel vapors
via opening purge valve 404 to allow fluidic communication between
fuel vapor storage canister 402 and engine intake manifold 44 via
conduit 485. Similarly, fuel vapor storage canister 406 may be
purged of fuel vapors via opening purge valve 408 to allow fluidic
communication between fuel vapor storage canister 406 and engine
intake manifold 44 via conduit 486. Likewise, fuel vapor storage
canister 416 may be purged of fuel vapors via opening purge valve
418 to allow fluidic communication between fuel vapor storage
canister 416 and engine intake manifold 44 via conduit 487. Thus,
fuel vapors from each of fuel tanks 230, 232, and 234 are isolated
from the other fuel tanks in fuel system 175.
[0037] In one example, the system of FIG. 4 operates according to
the method of FIG. 7 via executable instructions stored in
non-transitory memory of controller 12. While engine 10 is
operating, fuel vapors from fuel tank 230 may be stored in fuel
vapor storage canister 402. Fuel vapors from fuel tank 232 may be
stored in fuel vapor storage canister 406, and fuel vapors from
fuel tank 234 may be stored in fuel vapor storage canister 416.
Fuel vapors may be stored in fuel vapor storage canisters 402, 406,
and 416 when the engine is operating at conditions where fuel
vapors are not being accepted by the engine (e.g., during
deceleration fuel cut-out). When fuel vapors may be combusted by
the engine, vapor purge valves 404, 408, and/or 418 may be opened
to allow fuel vapors to flow to engine intake manifold 44 from the
respective fuel vapor storage canisters 402, 406, and 416.
[0038] In one example, fuel vapors from one or more of fuel vapor
storage canisters 402, 406, and 416 may be allowed to flow to
engine 10 only during conditions where higher octane fuel is
supplied to the engine in response to engine speed and load
conditions or when engine knock is determined present. However, if
it is determined that one or more of canisters 402, 406, and 416
has stored more than a predetermined threshold hydrocarbon storage
capacity (e.g., 85% of the canister's hydrocarbon storage
capacity), the purge valve corresponding to the fuel vapor storage
canister at the threshold hydrocarbon storage capacity may be
opened to allow the fuel vapor storage canister to be purged. For
example, if fuel vapor storage canister 406 is determined to have
stored an amount of hydrocarbons above the predetermined threshold
hydrocarbon storage capacity, vapor purge valve 408 may be opened
to reduce the amount of stored fuel vapor in fuel vapor storage
canister 406. Further, vapor purge valve 408 may be opened when
engine speed and load are in a range where a higher octane fuel is
supplied to the engine to limit the possibility of engine
knock.
[0039] If engine 10 is off (e.g., not rotating) or not accepting
fuel vapors (e.g., purge valve 408 is closed), and if temperature
and/or pressure is increasing in fuel tank 232 fuel vapors exit
fuel tank 232 and enter fuel vapor storage canister 406, thereby
reducing fuel system vapor pressure. Similarly, if engine 10 is off
or not accepting fuel vapors (e.g., purge valve 418 is closed), and
if temperature and/or pressure is increasing in fuel tank 234 fuel
vapors exit fuel tank 234 and enter fuel vapor storage canister
416, thereby reducing fuel system vapor pressure. Increasing fuel
temperature and/or pressure in fuel tank 230 causes fuel vapors
from fuel tank 230 to enter fuel vapor storage canister 402. Purge
valves 404, 408, and 418 may be operated independently or at the
same time.
[0040] On the other hand, if engine 10 is not operating or
accepting fuel vapors while temperature and/or pressure in fuel
tanks 230, 232, and 234 are decreasing, fuel vapors stored in each
fuel vapor storage canister 402, 406, and 416 may return to the
fuel tank from which they originated. Air may be drawn into fuel
vapor storage canisters 402, 406, and 416 via their respective
atmospheric vents 405, 407, and 417 when fuel system cooling
reduces the amount of vapor in the fuel system.
[0041] In this way, higher octane fuel vapors that have separated
from fuel 233 and fuel 235 may condense in the fuel tanks from
which they originated without condensing in other fuel tanks in
fuel system 175. Thus, higher octane fuel vapors that may be
produced via diurnal temperature increases in the fuel system may
be recovered in the tank from which the fuel vapors originated.
Although, recovering fuel vapors in the fuel tank from which the
fuel vapors originated may not always be desired, fuel vapors from
fuel tanks storing higher octane fuel are prevented from entering
fuel tanks storing lower octane fuels. Therefore, fuel in the fuel
tank storing the higher octane fuel may provide the benefits of
combusting a higher octane fuel without a reduced possibility of
creating engine knock because the octane number of the fuel in the
fuel tank storing higher octane fuel may not be reduced as much as
if the higher octane fuel vapors were permitted to condense in a
fuel tank holding or storing lower octane fuel. Fuel vapors that
condense in each of fuel tanks 230, 232, and 234 may be injected to
engine 10 as liquid fuel.
[0042] Further, fuel vapors may enter fuel vapor storage canister
402 only from fuel tank 230. Fuel vapors may enter fuel vapor
storage canister 406 only from fuel tank 232. Fuel vapors may enter
fuel vapor storage canister 416 only from fuel tank 234. Fuel
vapors may exit fuel vapor storage canister 402 and flow only to
the engine via purge valve 404 and engine vacuum or to fuel tank
230 via diurnal cooling of fuel in fuel tank 230. Fuel vapors from
fuel vapor canister 402 are prevented from entering fuel tanks 232
and 234 since there is no fluidic communication between vapor
canister 402 and fuel tanks 232 and 234. Closing purge valves 404,
408, and 418 prevents fuel vapors from entering engine intake
manifold 44 during diurnal cooling of fuel in the fuel system.
[0043] Referring now to FIG. 5, another alternative example fuel
system 175 is shown in detail. The fuel system of FIG. 5 may supply
fuel to engine 10 shown in detail in FIG. 1. The system of FIG. 5
may be operated according to the method of FIG. 7. Fuel system
components and fluidic conduits that allow fluidic communication
are shown as solid lines while electrical connections are shown as
dashed lines. Fuel system devices and components shown in FIG. 5
that have the same numerical identifiers as devices and components
shown in FIG. 2, are equivalent and operate as described in FIG. 2.
Therefore, the descriptions of fuel system components that are
described in FIG. 2 are omitted for the sake of brevity.
[0044] Fuel system 175 includes a fuel vapor storage canister 202
for storing fuel vapors. Fuel vapors may be supplied to fuel vapor
storage canister 202 via conduits 505, 504, and 502 which are in
fluidic communication with fuel tanks 230, 232, and 234. Although
three fuel tanks are shown, alternative examples may include fewer
or additional fuel tanks without departing from the scope or intent
of this description. Fuel vapors may be purged via purge valve 204
which allows fluidic communication between fuel vapor storage
canister 202 and engine intake manifold 44.
[0045] Fuel vapors from fuel tank 230 may be directed to fuel vapor
storage canister 202 from fuel tank 230 via fuel vapor valve 506.
Fuel vapors from fuel tank 232 may be directed to fuel vapor
storage canister 202 from fuel tank 232 via fuel vapor valve 508.
Fuel vapors from fuel tank 234 may be directed to fuel vapor
storage canister 202 from fuel tank 234 via fuel vapor valve
510.
[0046] Controller 12 may receive inputs from the sensors described
in FIG. 1 as well as sensors 241. In one example, sensors 241 may
be temperature sensors. Alternatively, sensors 241 may be pressure
sensors. Controller 12 also activates and deactivates fuel vapor
valves 506, 508, and 510 in response to fuel system and engine
operating conditions. Controller 12 also activates and deactivates
fuel vapor purge valve 204 in response to fuel system and engine
operating conditions. Additionally, controller 12 selectively
operates pump 250 to increase the production of fuel tank
vapors.
[0047] In one example, the system of FIG. 2 operates according to
the method of FIG. 7 via executable instructions stored in
non-transitory memory of controller 12. While engine 10 is
operating, fuel vapors from fuel tanks 230, 232, and 234 may be
stored in fuel vapor storage canister 202 via opening fuel vapor
valves 506, 508, and 510. Fuel vapor valves 506, 508, and 510 may
be opened in response to temperatures within fuel tanks 230, 232,
and 234 exceeding individual threshold temperatures that are based
on the fuel type stored in the respective fuel tanks Alternatively,
fuel vapor valves 506, 532, and 534 may be opened in response to
pressures within fuel tanks 230, 232, and 234 exceeding individual
threshold pressures that are based on the fuel type store in the
respective fuel tanks.
[0048] Fuel vapors from fuel tanks 230, 232, and 234 push air out
of atmospheric vent 205 and are stored by carbon 203 when
temperature and/or pressure in fuel tanks 230, 232, and 234 is
increasing. If engine 10 is operating while vapors are being
directed to fuel vapor storage canister 202, fuel vapor purge valve
204 may be opened so that fuel vapors are drawn into and combusted
in engine 10. If engine 10 is not operating or if fuel vapor purge
valve 204 is closed, fuel vapor valves 506, 508, and 510 may be
opened if temperature and/or pressure in fuel tanks 230, 232, and
234 are increasing so that fuel vapors may be stored in fuel vapor
storage canister 202.
[0049] On the other hand, if engine 10 is not operating or if fuel
vapor purge valve is closed while temperature and/or pressure in
fuel tanks 230, 232, and 234 are decreasing, fuel vapor valves 508
and 510 may be closed so that fuel vapors stored in fuel vapor
storage canister 202 may be released to fuel tank 230. In this way,
higher octane fuel vapors that have separated from fuel 233 and
fuel 235 may condense and be stored in fuel tank 230. Fuel vapors
from fuels 233 and 235 may have higher octane numbers than fuels
233 and 235. Thus, higher octane fuel vapors that may be produced
via diurnal temperature changes in the fuel system may be recovered
and stored to a fuel tank that holds higher octane fuel so that
higher octane fuel components remain separated from lower octane
fuels during fuel system heating and cooling. Higher octane fuel
vapor that condenses in fuel tank 230, which stores higher octane
fuel, may also be injected to engine 10 via fuel injector 66.
[0050] Further, fuel vapors may enter fuel vapor storage canister
202 only from fuel tanks 230, 232, and 234. Fuel vapors may exit
fuel vapor storage canister 202 and flow only to the engine via
purge valve 204 and engine vacuum or to fuel tank 230 via diurnal
cooling of fuel in fuel tank 230 when vapor valve 230 is open. Fuel
vapors from fuel vapor canister 202 are prevented from entering
fuel tanks 232 and 234 during diurnal cooling via closing vapor
valves 508 and 510. Closing vapor valves 508 and 510 also prevents
fuel vapors from fuel tank 232 from entering fuel tank 234 and
vise-versa during diurnal cooling of fuel in the fuel system.
[0051] Referring now to FIG. 6, another alternative example fuel
system 175 is shown in detail. The fuel system of FIG. 6 may supply
fuel to engine 10 shown in detail in FIG. 1. The system of FIG. 6
may be operated according to the method of FIG. 7. Fuel system
components and fluidic conduits that allow fluidic communication
are shown as solid lines while electrical connections are shown as
dashed lines. Fuel system devices and components shown in FIG. 6
that have the same numerical identifiers as devices and components
shown in FIGS. 2 and 4, are equivalent and operate as described in
FIGS. 2 and 4. Therefore, the descriptions of fuel system
components that are described in FIGS. 2 and 4 are omitted for the
sake of brevity.
[0052] In this example, fuel system 175 includes three fuel vapor
storage canisters 402, 406, and 416; however the number of fuel
vapor storage canisters may increase or decrease if the number of
fuel tanks is increased or decreased as is mentioned in the system
of FIG. 2. Each fuel vapor storage canister includes carbon 403 for
storing fuel vapors. First fuel vapor storage canister 402 includes
an atmospheric vent 405. Additionally, fuel vapor storage canisters
406 and 416 include respective atmospheric vents 407 and 417.
Second fuel vapor storage canister 406 may be in fluidic
communication with fuel tank 230 via conduit 684 when fuel vapor
valve 610 is open. Third fuel vapor storage canister 416 may also
be in fluidic communication with fuel tank 230 via conduit 683 when
fuel vapor valve 620 is open. Fuel vapors produced in fuel tank 232
may be routed to fuel vapor storage canister 406 via conduit 481
when fuel vapor valve 612 is in an open state so as to allow
fluidic communication between fuel tank 232 and fuel vapor storage
canister 406. Similarly, fuel vapors produced in fuel tank 234 may
be routed to fuel vapor storage canister 416 via conduit 482 when
fuel vapor valve 622 is in an open state so as to allow fluidic
communication between fuel tank 234 and fuel vapor storage canister
416. First fuel vapor storage canister 402 is shown in direct
fluidic communication with fuel tank 230 via conduit 488.
[0053] Fuel vapor storage canister 402 may be purged of fuel vapors
via opening purge valve 404 to allow fluidic communication between
fuel vapor storage canister 402 and engine intake manifold 44 via
conduit 485. Similarly, fuel vapor storage canister 406 may be
purged of fuel vapors via opening purge valve 408 to allow fluidic
communication between fuel vapor storage canister 406 and engine
intake manifold 44 via conduit 486. Likewise, fuel vapor storage
canister 416 may be purged of fuel vapors via opening purge valve
418 to allow fluidic communication between fuel vapor storage
canister 416 and engine intake manifold 44 via conduit 487.
[0054] In one example, the system of FIG. 6 operates according to
the method of FIG. 4 via executable instructions stored in
non-transitory memory of controller 12. While engine 10 is
operating, fuel vapors from fuel tank 230 may be stored in fuel
vapor storage canister 402. Fuel vapors from fuel tank 232 may be
stored in fuel vapor storage canister 406, and fuel vapors from
fuel tank 234 may be stored in fuel vapor storage canister 416.
Fuel vapors may be stored in fuel vapor storage canisters 402, 406,
and 416 when the engine is operating at conditions where fuel
vapors are not being accepted by the engine (e.g., during
deceleration fuel cut-out). When fuel vapors may be combusted by
the engine, vapor purge valves 404, 408, and/or 418 may be opened
to allow fuel vapors to flow to engine intake manifold 44 from the
respective fuel vapor storage canisters 402, 406, and 416.
[0055] In one example, fuel vapors from one or more of fuel vapor
storage canisters 402, 406, and 416 may be allowed to flow to
engine 10 only during conditions where higher octane fuel is
supplied to the engine in response to engine speed and load
conditions or when engine knock is determined present. However, if
it is determined that one or more of canisters 402, 406, and 416
has stored more than a predetermined threshold hydrocarbon storage
capacity (e.g., 85% of the canister's hydrocarbon storage
capacity), the purge valve corresponding to the fuel vapor storage
canister at the threshold hydrocarbon storage capacity may be
opened to allow the fuel vapor storage canister to be purged. For
example, if fuel vapor storage canister 406 is determined to have
stored an amount of hydrocarbons above the predetermined threshold
hydrocarbon storage capacity, vapor purge valve 408 may be opened
to reduce the amount of stored fuel vapor in fuel vapor storage
canister 406. Further, vapor purge valve 408 may be opened when
engine speed and load are in a range where a higher octane fuel is
supplied to the engine to limit the possibility of engine
knock.
[0056] If engine 10 is off (e.g., not rotating) or not accepting
fuel vapors, and if temperature and/or pressure is increasing in
fuel tank 232 fuel vapor valve 612 may be opened to allow fuel
vapors to exit fuel tank 232 and enter fuel vapor storage canister
406, thereby reducing fuel system vapor pressure. Similarly, if
engine 10 is off or not accepting fuel vapors, and if temperature
and/or pressure is increasing in fuel tank 234 fuel vapor valve 622
may be opened to allow fuel vapors to exit fuel tank 234 and enter
fuel vapor storage canister 416, thereby reducing fuel system vapor
pressure. Increasing fuel temperature and/or pressure in fuel tank
230 causes fuel vapors from fuel tank 230 to enter fuel vapor
storage canister 402 since no purge valve is positioned along
conduit 488. Fuel vapor valves 610, 620, 612, and 622 may be
operated independently or at the same time. Likewise, purge valves
404, 408, and 418 may be operated independently or at the same
time.
[0057] On the other hand, if engine 10 is not operating or
accepting fuel vapors while temperature and/or pressure in fuel
tanks 230, 232, and 234 are decreasing, fuel vapor valves 612 and
622 may be closed. Further, fuel vapor valves 610 and 620 may be
opened so that fuel vapors stored in fuel vapor storage canisters
406 and 416 may be released to fuel tank 230. Opening vapor valve
610 and closing vapor valve 612 allows air to be drawn into fuel
vapor storage canister via atmospheric vent 407 when fuel system
cooling reduces the amount of vapor in the fuel system. Likewise,
opening vapor valve 620 and closing vapor valve 622 allows air to
be drawn into fuel vapor storage canister via atmospheric vent 417
when fuel system cooling reduces the amount of vapor in the fuel
system.
[0058] In this way, higher octane fuel vapors that have separated
from fuel 233 and fuel 235 may condense and be stored in fuel tank
230. Fuel vapors from fuels 233 and 235 may have higher octane
numbers than fuels 233 and 235. Thus, higher octane fuel vapors
that may be produced via diurnal temperature changes in the fuel
system may be recovered and stored to a fuel tank that holds higher
octane fuel so that higher octane fuel components remain separated
from lower octane fuels during fuel system heating and cooling.
Higher octane fuel vapor that condenses in fuel tank 230, which
stores higher octane fuel, may also be injected to engine 10 via
fuel pump 202 and fuel injector 66.
[0059] Further, fuel vapors may enter fuel vapor storage canister
402 only from fuel tanks 230, 232, and 234. Fuel vapors may exit
fuel vapor storage canister 402 and flow only to the engine via
purge valve 404 and engine vacuum or to fuel tank 230 via diurnal
cooling of fuel in fuel tank 230. Fuel vapors from fuel vapor
canister 402 are prevented from entering fuel tanks 232 and 234
during diurnal cooling via closing vapor valves 612 and 622.
Closing vapor valves 612 and 622 also prevents fuel vapors from
fuel tank 232 from entering fuel tank 234 and vice-versa during
diurnal cooling of fuel in the fuel system. Likewise, closing vapor
valve 612 during diurnal cooling prevents fuel vapors from passing
from fuel vapor canister 406 into fuel tank 232. Closing vapor
valve 622 during diurnal cooling prevents fuel vapors from passing
from fuel vapor canister 416 to fuel tank 234.
[0060] In some examples, fuel vapor valve 610 may be replaced with
a check valve that limits or prevents flow of fuel vapors from fuel
tank 230 to fuel vapor storage canister 406 and that allows fuel
vapors to flow from fuel vapor storage canister 406 to fuel tank
230. Similarly, fuel vapor valve 620 may be replaced with a check
valve that limits or prevents flow of fuel vapors from fuel tank
230 to fuel vapor storage canister 416 and that allows fuel vapors
to flow from fuel vapor storage canister 416 to fuel tank 230.
[0061] Thus, the fuel systems of FIGS. 2-6 may provide for a fuel
storage system, comprising: a first fuel tank; a second fuel tank;
a first fuel vapor storage canister; a second fuel vapor storage
canister; a first conduit coupled to the first fuel tank and the
first fuel vapor storage canister; a second conduit not coupled to
the first conduit, the second conduit coupled to the first fuel
tank and the second fuel vapor storage canister; and a valve
positioned along the second conduit. The fuel vapor system where
the first fuel tank stores a fuel having a higher octane number
than a fuel stored in the second fuel tank, and where the first
conduit provides fluidic communication between the first fuel tank
and the first fuel vapor storage canister, and where the second
conduit provides fluidic communication between the first fuel tank
and the second fuel vapor storage canister.
[0062] In another example, the fuel system further comprises a
third conduit coupled to the second fuel tank and the second fuel
vapor storage canister. The fuel vapor storage system further
comprises a valve positioned along the third conduit. The fuel
storage system further comprises a fourth conduit, the fourth
conduit coupled to an engine intake system and the second fuel
vapor storage canister. The fuel storage system further comprises a
fuel vapor purge valve positioned along the fourth conduit. The
fuel storage system, further comprises a controller including
executable instructions stored in non-transitory memory for
limiting return of fuel vapors from the second fuel vapor storage
canister to the second fuel tank.
[0063] The systems of FIGS. 2-6 may also provide a fuel vapor
storage system, comprising: two or more fuel tanks, a first fuel
tank of the two or more fuel tanks storing a fuel having a higher
octane number than a remainder of the two or more fuel tanks; a
conduit coupled to the first fuel tank and one of the remainder of
the two or more fuel tanks; and a check valve positioned along the
conduit biased to limit flow from the first fuel tank to the
remainder of the two or more fuel tanks The fuel storage system
further comprises a fuel vapor storage canister and a conduit
coupled to the fuel vapor storage canister and the first fuel tank,
and where the conduit coupled to the fuel vapor storage canister is
a sole conduit coupled to the fuel vapor storage canister and the
two or more fuel tanks. The fuel storage system further comprises a
conduit coupled to an engine waste heat exchanger and one or more
of the two or more fuel tanks The fuel storage system further
comprises a fuel pump in fluidic communication with the first fuel
tank and a direct fuel injector. The fuel storage system further
comprises a fuel pump in fluidic communication with one of the two
or more fuel tanks other than the first fuel tank and a port fuel
injector.
[0064] Additionally, the systems of FIGS. 2-6 provide for a fuel
vapor storage system, comprising: a first fuel tank storing a first
fuel; a second fuel tank storing a second fuel, the second fuel
including a lower octane number than the first fuel; a first fuel
vapor storage canister in fluidic communication with the first fuel
tank; and a controller including executable instructions stored in
non-transitory memory for limiting flow of fuel vapors from the
first fuel tank to the second fuel tank. The fuel vapor storage
system further comprises a valve, and where limiting flow of fuel
vapors is achieved via closing the valve.
[0065] In some examples, the fuel vapor storage system further
comprises a first conduit coupled to the first fuel vapor storage
canister and the first fuel tank, and a second conduit coupled to
the first fuel vapor storage canister and the second fuel tank. The
fuel vapor storage system further comprises a second fuel vapor
storage canister, the second fuel vapor storage canister in fluidic
communication with the second fuel tank and not in fluidic
communication with the first fuel tank outside of an engine intake.
The fuel vapor storage system further comprises two fuel vapor
purge valves, a first fuel vapor purge valve of the two fuel vapor
purge valves in fluidic communication with the first fuel vapor
storage canister and an engine intake. The fuel vapor storage
system further comprises a second fuel vapor purge valve of the two
fuel vapor purge valves in fluidic communication with the second
fuel vapor storage canister and the engine intake. The fuel vapor
storage system further comprises additional controller instructions
for allowing flow of fuel vapors from the second fuel tank to the
first fuel tank during diurnal cooling of the fuel vapor storage
system. The fuel vapor storage system further comprises additional
controller instructions to inject condensed fuel in the first fuel
tank to an engine, and where the condensed fuel originated from the
second fuel tank.
[0066] Referring now to FIG. 7, a method for operating a fuel
system of a vehicle is shown. The method of FIG. 7 may be stored as
executable instructions in non-transitory memory a controller of a
system as shown in FIG. 1. The method of FIG. 7 may be applied to
the example fuel systems shown in FIGS. 2-6 as well as other fuel
systems.
[0067] At 702, method 700 judges whether or not the engine is
stopped. In one example, the engine may be judged to be stopped
rotating if engine speed is zero. If method 700 judges that the
engine is stopped, the answer is yes and method 700 proceeds to
720. Otherwise, the answer is no and method 700 proceeds to
704.
[0068] At 704, method 700 judges whether or not more than one fuel
vapor storage canister is present in the fuel system (e.g., the
fuel systems shown in FIGS. 4 and 6). In one example, method 700
may judge whether or not more than one fuel vapor storage canister
is present in the fuel system based on a variable stored in
controller memory that indicates the number of fuel vapor storage
canisters in the vehicle fuel system. If method 400 judges that
more than one fuel vapor storage canister is present in the fuel
system, the answer is yes and method 700 proceeds to 706.
Otherwise, the answer is no and method 700 proceeds to 710.
[0069] At 706, method 700 judges whether or not conditions are
present for purging fuel vapors from fuel vapor storage canisters.
The fuel system may include two or more fuel tanks and one or more
fuel vapor storage canisters as shown in FIGS. 2-6. In one example,
method 700 may judge that conditions are present for purging fuel
vapors from fuel canisters when the engine is combusting air-fuel
mixtures (e.g., one or more cylinders are activated), and when the
amount of fuel vapors stored in a fuel vapor storage canister
exceeds a threshold level of fuel. Alternatively, or in addition,
conditions for fuel vapor purging may be judged to be present when
temperature and/or pressure in one or more fuel tanks is greater
than a threshold temperature or pressure, pressure in the intake
manifold is below a threshold, etc. If method 700 judges that
conditions are present for purging fuel vapors from the fuel vapor
storage canisters, the answer is yes and method 700 proceeds to
708. Otherwise, the answer is no and method 700 proceeds to
712.
[0070] At 712, method 700 closes fuel system purge valves (e.g.,
purge valve 204 of FIGS. 2, 3, and 5, and purge valves 404, 408,
and 418 of FIGS. 4 and 6). The fuel system purge valves may be
closed to reduce the possibility of drawing fuel vapors into an
engine that is not combusting an air-fuel mixture or during
conditions where the engine may not operate as is desired if the
purge valves are at least partially opened. Method 700 proceeds to
exit after fuel vapor purge valves are closed.
[0071] At 708, method 700 selects fuel vapor purge valves in
response to engine fuel consumption at the present engine speed and
load conditions. U.S. patent application Ser. No. 14/019,362, filed
on Sep. 5, 2013, titled VAPOR PURGING OCTANE SEPARATION SYSTEM, the
entire contents of which are hereby incorporated by reference for
all intents and purposes includes examples of purging fuel vapors
from multiple fuel vapor storage canisters. In one additional
example, fuel vapor purge valves are selected to be opened based on
the amount of fuel vapor estimated stored in each of the fuel vapor
storage canisters and engine fuel consumption. In particular, the
number of fuel vapor purge valves opened is a number less than a
number of open purge valves that will provide an amount of fuel
less than is being consumed at the present engine operating
conditions. For example, if the engine is consuming 8.0 Kg/hr of
fuel, the fuel system has three fuel vapor storage canisters, and
each fuel vapor storage canister has the capacity to output 3.0
Kg/hr for a period of time, method 700 opens two fuel vapor purge
valves to provide 6.0 Kg/her to the engine. The additional 2.0
Kg/hr is injected to the engine in liquid form. In some examples,
where the fuel vapor purge valves may be adjusted to a partially
open state, the fuel vapor purge valves may be adjusted to provide
the amount of fuel consumed by the engine at the present operating
conditions. In other examples, the method of FIG. 7 may provide a
desired fractional amount of fuel consumed by the engine at the
present operating conditions. For example, if the engine is
consuming 6 Kg/hr of fuel, the fuel vapor valves may be adjusted to
provide 2 Kg/hr of fuel or thirty three percent of fuel consumed by
the engine at present operating conditions. The number of fuel
vapor valves opened corresponds to the number of fuel vapor valves
that when opened provide the desired percentage of fuel supplied to
the engine at present operating conditions. Method 700 proceeds to
710 after the number of fuel vapor purge valves to be opened is
determined.
[0072] At 710, method 700 selects fuel vapor purge valves according
to engine fuel octane requirements at the present engine speed and
load. If a group or number of fuel vapor purge valves were selected
at 708, method 700 selects fuel vapor purge valves from the group
of fuel vapor purge valves selected at 708. Further, if the fuel
system has more than one purge valve (e.g., FIGS. 4 and 6), a
number of fuel purge valves less than the full complement of fuel
purge valves may be opened in response to the amount of higher
octane fuel the engine uses to while operating at the present
engine speed and load.
[0073] For example, if the engine uses only a small amount of
higher octane fuel at the present engine speed and load to limit
the possibility of engine knock, only one of three fuel purging
valves may be opened. The fuel flow rate through the selected purge
valves is less than or equal to the amount of higher octane fuel
determined to be used at the present engine operating conditions
based on engine speed and load. If the engine does not use higher
octane fuel at the present operating conditions, the fuel vapor
purge valves are not opened unless fuel pressure and/or temperature
in one of the fuel system fuel tanks is greater than a threshold
pressure or temperature. However, if the engine uses a greater
amount of higher octane fuel than all the fuel vapor purge valves
may provide at the present engine operating conditions, all fuel
vapor purge valves may be opened to fuel the engine and reduce the
possibility of engine knock. In this way, higher octane fuel vapors
may be conserved for engine operating conditions where use of
higher octane fuel may be more beneficial (e.g., higher engine
speeds and loads). The engine octane number requirement may
increase as engine speed and/or load increase. Method 700 proceeds
to 712 after fuel vapor purge valves are opened and closed in
response to engine speed and load conditions.
[0074] At 712, method 400 opens selected fuel vapor purging valves
to purge fuel vapors from the fuel system. The number of fuel vapor
purge valves opened is based on engine fuel consumption at the
present engine speed and load as well as engine fuel octane
requirements at the present engine speed and load. Method 700
proceeds to exit after selected fuel vapor purging valves are
opened.
[0075] At 720, method 700 judges whether or not temperature and/or
pressure (e.g., fuel vapor temperature or fuel vapor pressure) in
one or more of the fuel system fuel tanks is increasing.
Temperature and/or pressure within a fuel system may be measured
via sensors or estimated. If method 700 judges that temperature
and/or pressure in one or more fuel tanks is increasing, the answer
is yes and method 700 proceeds to 722. Otherwise, method 700
proceeds to 730.
[0076] Alternatively, method 700 may increase temperature and/or
fuel pressure in one or more fuel tanks in response to a low amount
of higher octane fuel or a low amount of fuel vapors stored in fuel
vapor storage canisters at 720. The fuel tank temperature may be
increased via circulating a fluid heated via engine exhaust gases
or engine coolant to one or more fuel tanks. Method 700 proceeds to
722 if fuel tank heating is activated. Otherwise, method 700
proceeds to 730.
[0077] At 722, method 700 opens vapor valves. In particular, vapor
valves that are in fluidic communication or associated with a fuel
tank that is rising in temperature and/or pressure are opened.
Vapor valves that are in fluidic communication or associated with
fuel tanks where temperature and/or pressure are not rising may
remain in a closed state.
[0078] For example, for the system of FIG. 5, if temperature in
fuel tank 232 is increasing, fuel vapor valve 508 may be opened
while fuel vapor valves 506 and 510 may remain closed when fuel
temperature and/or pressure is not increasing in fuel tanks 230 and
234. Similarly, for the system of FIG. 6, if temperature in fuel
tank 232 is increasing, fuel vapor valves 612 may be opened to
allow fuel vapors into fuel vapor storage canister 406 while fuel
vapor valves 610, 622, and 622 remain closed. On the other hand, if
temperature and/or pressure is increasing in fuel tanks 230, 232,
and 234, fuel vapor valves 612 and 622 may be opened while fuel
vapor valves 610 and 620 are in a closed state so that fuel vapor
from fuel tank 230 does not enter fuel vapor canisters 406 and 416.
For the system shown in FIG. 3, check valves 310 and 312 open in
response to increasing temperature and/or pressure in fuel tanks
232 and 234.
[0079] Thus, fuel vapor valves may be commanded to open depending
on whether or not temperature and/or pressure is increasing in fuel
tanks associated with the respective fuel vapor valves. Further,
opening vapor valve 612 while fuel system temperature is increasing
allows fuel vapors to flow from fuel tank 232 to fuel vapor
canister 406 without fuel from fuel tanks 230 and 234 or fuel vapor
canisters 416 and 402 from entering fuel tank 232. Likewise,
opening vapor valve 622 while fuel system temperature is increasing
allows fuel vapors to flow from fuel tank 234 to fuel vapor
canister 416 without fuel from fuel tanks 230 and 232 or fuel vapor
canisters 402 and 406 from entering fuel tank 234. Method 700
proceeds to exit after fuel vapor valves associated with fuel tanks
where temperature and/or pressure are increasing are opened.
[0080] At 730, method 700 judges whether or not temperature and/or
pressure are decreasing in one or more fuel tanks of the fuel
system. The temperature and/or pressure within each of the fuel
tanks in the fuel system may be inferred or measured via a sensor.
If temperature and/or pressure in one or more fuel tanks in the
fuel system is determined to be decreasing, the answer is yes and
method 700 proceeds to 732. Otherwise, the answer is no and method
700 proceeds to 736.
[0081] At 732, method 700 opens a vapor valve that is positioned in
a conduit between a fuel tank storing a higher octane fuel as
compared to other fuel tanks in the fuel system and a fuel vapor
storage canister that is storing fuel vapors from the fuel tank
storing higher octane fuel. In systems where no vapor valve is
positioned along a conduit between the fuel tank storing the higher
octane fuel and the fuel vapor storage canister that is storing
fuel vapors from the fuel tank storing higher octane fuel, no vapor
valve along a conduit between the fuel tank storing higher octane
fuel and the fuel vapor storage canister that is storing fuel
vapors from the fuel tank storing higher octane fuel is opened at
732.
[0082] For example, vapor valve 506 is opened in the fuel system
shown in FIG. 5 since vapor valve is positioned along a conduit
that allows fluidic communication between fuel tank 230 and fuel
vapor storage canister 202. Since no vapor valve is shown along
conduit 488 of FIG. 4 which allows fluidic communication between
fuel tank 230 and fuel vapor storage canister 402, no vapor valve
along a conduit between the fuel tank storing higher octane fuel
and the fuel vapor storage canister that is storing fuel vapors
from the fuel tank storing higher octane fuel is opened at 732 for
the system shown in FIG. 4.
[0083] However, vapor valves that allow fuel vapors into the fuel
tank storing higher octane fuel from fuel vapor storage canisters
storing fuel vapors from fuel tanks holding lower octane fuels are
opened. For example, vapor valves 610 and 620 of FIG. 6 may be
opened when temperature and/or pressure in one or more fuel tanks
is decreasing. In particular, vapor valves 610 and 620 may be
opened and vapor valves 612 and 622 may be closed when temperature
and/or pressure is decreasing in fuel tank 230. By opening vapor
valves that allow fluidic communication between fuel vapor storage
canisters and the fuel tank storing higher octane fuel, it may be
possible to transfer higher octane fuel components from fuel tanks
storing lower octane fuels to a fuel tank storing higher octane
fuel (e.g., from tanks 232 and 234 to tank 230). The fuel vapors
may condense into liquid fuel within the fuel tank storing the
higher octane fuel. In this way, component fuels may be separated
with reduced parasitic losses.
[0084] At 734, method 700 closes vapor valves for fuel tanks in
fuel systems that hold lower octane fuels. For example, in the fuel
system of FIG. 5, vapor valves 508 and 510 are closed to reduce the
possibility of transferring higher octane fuels to fuel tanks
holding lower octane fuels. In the fuel system of FIG. 6, method
700 closes vapor valves 612 and 622 to reduce the possibility of
transferring higher octane fuels to fuel tanks holding lower octane
fuels. In other examples, check valves may replace vapor valves 408
and 410 in the system of FIG. 4. Similarly, check valves may
replace vapor valves 612 and 622 in the system of FIG. 6, if
desired. Method 700 proceeds to exit after the vapor valve
positions are adjusted.
[0085] At 736, method 700 closes vapor valves after a predetermined
amount of time has passed since temperature and/or pressure in the
fuel tanks has increased or decreased. By closing the vapor valves,
it may be possible to limit fluidic communication between fuel
tanks and fuel vapor storage canisters when conditions in the fuel
system are static.
[0086] In this way, method 700 allows operating states of fuel
system valves to be adjusted while the engine is stopped so that
fuel separation may occur without recombining higher octane fuels
with lower octane fuel during diurnal heating and cooling that
often occurs each day. Further, method 700 may use engine waste
heat to increase the production of higher octane fuel vapors. Once
higher octane fuel components are separated and stored in fuel
vapor storage canisters, the higher octane fuel components remain
separated from the lower octane fuels stored in the fuel tanks. The
higher octane fuel vapors stored in fuel vapor storage canisters
may be condensed in a fuel tank holding higher octane fuel before
being injected to the engine.
[0087] As will be appreciated by one of ordinary skill in the art,
method described in FIG. 7 may represent one or more of any number
of processing strategies such as event-driven, interrupt-driven,
multi-tasking, multi-threading, and the like. As such, various
steps or functions illustrated may be performed in the sequence
illustrated, in parallel, or in some cases omitted. Likewise, the
order of processing is not necessarily required to achieve the
objects, features, and advantages described herein, but is provided
for ease of illustration and description. Although not explicitly
illustrated, one of ordinary skill in the art will recognize that
one or more of the illustrated steps or functions may be repeatedly
performed depending on the particular strategy being used. Further,
the described actions, operations, methods, and/or functions may
graphically represent code to be programmed into non-transitory
memory of the computer readable storage medium in the engine
control system.
[0088] This concludes the description. The reading of it by those
skilled in the art would bring to mind many alterations and
modifications without departing from the spirit and the scope of
the description. For example, I3, I4, I5, V6, V8, V10, and V12
engines operating in natural gas, gasoline, diesel, or alternative
fuel configurations could use the present description to
advantage.
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