U.S. patent application number 11/871743 was filed with the patent office on 2008-02-07 for fuel utilization.
This patent application is currently assigned to VAPOR FUEL TECHNOLOGIES, LLC. Invention is credited to Raymond Bryce Bushnell, Anthony Dean, Marcus DeHaas, Danny Robert Lewis.
Application Number | 20080032245 11/871743 |
Document ID | / |
Family ID | 40226769 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080032245 |
Kind Code |
A1 |
Bushnell; Raymond Bryce ; et
al. |
February 7, 2008 |
FUEL UTILIZATION
Abstract
Embodiments of the present invention provide a fuel supply
system for combustion engines, whereby the temperatures of an
oxidizer and fuel may be increased so that the temperatures
approach but do not achieve an auto-ignition temperature for the
fuel charge. The fuel charge may result in substantial improvements
in fuel efficiency.
Inventors: |
Bushnell; Raymond Bryce;
(Beavercreek, OR) ; Dean; Anthony; (Golden,
CO) ; Lewis; Danny Robert; (Beavercreek, OR) ;
DeHaas; Marcus; (Oregon City, OR) |
Correspondence
Address: |
SCHWABE, WILLIAMSON & WYATT, P.C.;PACWEST CENTER, SUITE 1900
1211 SW FIFTH AVENUE
PORTLAND
OR
97204
US
|
Assignee: |
VAPOR FUEL TECHNOLOGIES,
LLC
25023 S. Beeson Rd.
Beavercreek
OR
97004
|
Family ID: |
40226769 |
Appl. No.: |
11/871743 |
Filed: |
October 12, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10578693 |
May 9, 2006 |
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PCT/US04/14146 |
May 7, 2004 |
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11871743 |
Oct 12, 2007 |
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11817785 |
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PCT/US05/35218 |
Sep 30, 2005 |
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11871743 |
Oct 12, 2007 |
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10706507 |
Nov 11, 2003 |
6907866 |
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11817785 |
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60947623 |
Jul 2, 2007 |
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Current U.S.
Class: |
431/11 |
Current CPC
Class: |
F23D 11/402 20130101;
F23N 5/022 20130101; F23D 11/44 20130101; F23N 2221/08 20200101;
F23C 2202/20 20130101; F23N 2221/12 20200101; F23N 2221/04
20200101; F23N 2227/02 20200101; F23N 5/184 20130101 |
Class at
Publication: |
431/011 |
International
Class: |
F23K 5/20 20060101
F23K005/20 |
Claims
1. A method, comprising: adjusting the temperature of a fuel charge
so that the temperature approaches, but does not achieve, an
auto-ignition temperature; inducting the fuel charge into a
combustion chamber; and initiating a combustion event to
substantially auto-ignite the fuel charge.
2. The method of claim 1, wherein the fuel charge includes an
oxidizer component and a fuel component; and adjusting the
temperature of the fuel charge comprises heating the oxidizer
component and/or the fuel component prior to inducting the fuel
charge into the combustion chamber.
3. The method of claim 2, further comprising controlling the
heating of the oxidizer component and/or the fuel component to
maintain a desired oxidizer-to-fuel ratio.
4. The method of claim 1, wherein the adjusting the temperature of
the fuel charge comprises increasing the temperature of the fuel
charge to dilute the fuel charge.
5. The method of claim 1, wherein the fuel charge includes a vapor
fuel component.
6. The method of claim 1, wherein initiating the combustion event
comprises initiating a spark to substantially auto-ignite the fuel
charge.
7. The method of claim 1, further comprising adjusting the timing
of the initiation of the combustion event to substantially
auto-ignite the fuel charge at a desired crank angle based at least
on characteristics of the fuel charge.
8. The method of claim 7, wherein the characteristics of the fuel
charge include homogeneity, temperature, combustion duration,
and/or flame speed of the fuel charge.
9. A method comprising: during a first mode of operation: inducting
an amount of preheated fuel into a combustion chamber; and
combining an amount of exhaust-gas-recirculation with the amount of
preheated fuel to substantially ignite the amount of preheated of
fuel; and during a second mode of operation: inducting an increased
amount of preheated fuel into the combustion chamber; combining a
decreased amount of exhaust-gas-recirculation with the increased
amount of preheated fuel, the decreased amount of
exhaust-gas-recirculation incapable of substantially igniting the
increased amount of preheated fuel; and performing a spark to
substantially ignite the increased amount of preheated fuel.
10. The method of claim 9, wherein the first mode of operation
further comprises performing an initiation spark in addition to
combining the amount of exhaust-gas-recirculation with the amount
of preheated fuel to substantially ignite the amount of preheated
fuel.
11. The method of claim 9, wherein the second mode of operation
further comprises, advancing the performing of the spark to occur
sooner in a compression cycle of the combustion chamber.
12. The method of claim 9, wherein the preheated fuel has been
fractionated.
13. The method of claim 9, wherein the amount of preheated fuel and
the increased amount of preheated fuel are both mixed with an
oxidizer, and the oxidizer-to-fuel ratio is maintained at
approximately 14.7-to-1.
14. A system comprising: a vaporization chamber including a heating
source to vaporize fuel; an air conduit adapted to supply and mix
air with the vaporized fuel; and a controller to control the
mixture of air and fuel to maintain a desired carbon level in an
amount of combustion exhaust.
15. The system of claim 14, wherein the controller further controls
the mixture of air and fuel to maintain a desired air-to-fuel
mixture.
16. The system of claim 14, wherein: the heating source is adapted
to fractionate the fuel and/or increase the temperature of the
fractioned fuel; the air conduit includes an air heater adapted to
increase the temperature of the air; and the controller is adapted
to control the increase in temperatures of the fractionated fuel
and/or the intake air to maintain a desired air-to-fuel ratio.
17. The system of claim 16, further comprising: a mixer to combine
the heated intake air and the heated fractionated fuel to form a
fuel charge; a combustion chamber to combust the fuel charge; and a
spark plug to perform a spark to substantially ignite the fuel
charge, wherein the controller further controls a timing of the
performance of the spark.
18. The system of claim 16, wherein the controller further controls
the mixture of the heated intake air and the heated fractionated
fuel to maintain an air-to-fuel ratio of the fuel charge.
19. The system of claim 16, further comprising a sensor to monitor
at least one of oxygen content, temperature, ignition temperature,
carbon content, air-to-fuel ratio, and/or density of the
fractionated fuel and/or intake air.
20. A method of combusting a fuel charge comprising: inducting a
prepared fuel charge into a combustion chamber; initiating a flame
front to ignite a first portion of the prepared fuel charge to
increase the temperature and pressure inside the combustion
chamber; initiating auto-ignition of a second portion of the
prepared fuel charge, as a result of the increase in temperature
and pressure inside the combustion chamber; and initiating
subsequent flame fronts and/or subsequent auto-ignitions of the
remaining portions of the prepared fuel charge to cooperatively and
substantially combust the fuel charge.
21. The method of claim 20 further comprising adjusting the timing
of the initiating of the flame front to cooperatively and
substantially combust the fuel charge at a desired crank angle.
22. The method of claim 20 wherein the prepared fuel charge is
fractionated.
23. A method comprising: diluting a fuel charge to be combusted in
a combustion cylinder; and adjusting the combustion of the diluted
fuel charge to generate a desired power output based at least in
part on characteristics of the diluted fuel charge.
24. The method of claim 23, wherein diluting the fuel charge
comprises increasing the temperature of an amount of fuel and an
amount of oxidizer to generate a diluted fuel charge having an
oxidizer-to-fuel ratio of approximately 14.7-to-1.
25. The method of claim 23 wherein adjusting the combustion of the
diluted fuel charge comprises substantially combusting the diluted
fuel charge at a desired crank angle.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a non-provisional application of
Provisional Application No. 60/947,623, filed on Jul. 2, 2007, and
claims priority to said provisional application. The present
application is also a continuation-in-part of Non-Provisional
application Ser. No. 10/578,693, filed May 9, 2006, and claims
priority to said application. application Ser. No. 10/578,693 is
the U.S. National Entry of a PCT that claims priority to now issued
U.S. Pat. No. 6,907,866, having a filing date of Nov. 11, 2003. The
present application is also a continuation-in-part of application
Ser. No. 11/817,785, filed Sep. 4, 2007, and claims priority to
said application. application Ser. No. 11/817,785 is the U.S.
National Entry of a PCT application that claims priority to now
issued U.S. Pat. No. 7,028,675, with a filing date of Mar. 4, 2005,
which is a continuation-in-part of now issued U.S. Pat. No.
6,907,866, having a filing date of Nov. 11, 2003.
TECHNICAL FIELD
[0002] Embodiments of the present invention relate to the field of
providing vaporized or liquid fuel to engines, and more
particularly to vapor and liquid fuel systems where various
parameters of the fuel mixture may be varied to increase the
efficiency of a given fuel charge.
BACKGROUND AND BRIEF DESCRIPTION
[0003] Vaporizing fuel prior to its entrance into the cylinder can
lead to improved performance, particularly with respect to
substantially improved fuel economy. Applicants have discussed the
advantages and various inventions surrounding vapor fuel systems in
many of their current patents and pending applications (See, U.S.
Pat. Nos. 6,681,749; 6,907,866; 6,966,308; 7,028,675; and
application Ser. Nos. 11/465,792 and 11/421,698). While some of
these patents and applications teach advantages of running an
engine "lean" (i.e., at an air to fuel ratio of greater than about
15 to 1), they also teach improving fuel economy in conventional
systems that are designed to operate at current stoichiometric
conditions, such as an air to fuel ratio around 14.7 to 1.
[0004] More recently, systems have been focused on increasing the
temperature of a fuel charge once it enters the combustion chamber
to a point where the mixture of air and fuel spontaneously ignite.
The low end temperature at which typical grade gasoline begins to
ignite, in such a manner, is around 500.degree. F. Most systems are
achieving this necessary temperature through increased compression
ratios. Examples of such systems include Controlled Auto Ignition
(CAI) and Homogeneous Charge Combustion Ignition (HCCI). These
systems have disadvantages and are not well suited for dealing with
transients, such as periods of acceleration or deceleration. One of
the disadvantages that may stem from the wide ranges and diversity
of temperatures required for the spontaneous ignition of a given
fuel charge (e.g. 500.degree.-1100.degree. F.). For example, these
systems attempt to ignite the entire charge at one moment in time.
Because of this, their temperatures are generally elevated towards
the higher end of the temperature range. This wide range of
ignition temperatures combined with elevated ignition temperatures
may allow a fuel charge to prematurely ignite, for example before
the piston reaches top dead center, and may result in a decrease in
efficiency and possible engine damage. Conversely, ignition
temperatures that are not elevated may contribute to an environment
conducive to longer combustion durations, where components having
lower ignition temperatures ignite first and then propagate, like a
forest fire, through the components requiring higher ignition
temperatures.
[0005] Additionally, various ones of these systems may also require
substantially steady state conditions to function efficiently. For
example, in an HCCI mode, there is no sparking device to trigger
the combustion event. Rather, combustion is dependent solely upon
the conditions within the cylinder, i.e., temperature, pressure,
air-to-fuel ratio ("AFR"), fuel state, and exhaust gas
recirculation ("EGR"). These conditions are typically varied to
control when auto-ignition, and consequently, combustion occurs. If
there is a rapid change in any one of these conditions, for example
during periods of rapidly increasing loads, then the combustion
event becomes unpredictable. As an example, when an engine
increases its revolutions per minute ("RPMs") there is less time
for the fuel charge to change states within the cylinder. This
effectively reduces the likelihood of matching the density of the
fuel with the density of the induced air, thereby resulting in an
AFR mismatch. This density mismatch may lead to premature ignition,
possible engine damage, and unacceptable emissions.
[0006] Applicants have developed techniques to improve combustion
such that fuel economy may be improved in both vapor and liquid
charged systems. In various embodiments, the fuel (liquid or vapor)
and air may be independently heated and the densities of each
controlled. Upon mixing the air and fuel, an air to fuel ratio of
14.7-1 may be maintained at elevated temperatures prior to entrance
into a combustion chamber or within the combustion chamber. In
various embodiments, elevating the pre-combustion temperature so
that it approaches, but does not achieve, an auto-ignition
temperature for a given fuel charge may result in more efficient
combustion and a system that is better able to handle transitions.
Such may be attributable to several factors including the
homogeneity of the fuel charge, increased flame speed, increased in
cylinder temperature, and/or the multiple flame fronts encountered.
In further embodiments, fuel economy may be improved by altering
various other parameters which allow for better control of the
combustion of the fuel charge. Such parameters may improve
efficiency by also increasing the flame speed and decreasing the
combustion duration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Embodiments of the present invention will be readily
understood by the following detailed description in conjunction
with the accompanying drawings. Embodiments of the invention are
illustrated by way of example and not by way of limitation in the
figures of the accompanying drawings.
[0008] FIG. 1 illustrates a block diagram in accordance with
various embodiments of the present invention;
[0009] FIG. 2 illustrates a graphical representation of a
relationship between diluting an amount of fuel and the need for
improved combustion in accordance with various embodiments of the
present invention;
[0010] FIG. 3 illustrates graphical representations of the various
combustion durations with respect to top dead center of various
combustion events;
[0011] FIG. 4 illustrates graphical representations of the
in-cylinder pressures ("ICP") of the various combustion events
illustrated in FIG. 3, respectively;
[0012] FIG. 5 illustrates a flow diagram depicting a combustion
operation in accordance with various embodiments of the present
invention; and
[0013] FIG. 6 illustrates a flow diagram depicting a combustion
operation in accordance with various embodiments of the present
invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0014] In the following detailed description, reference is made to
the accompanying drawings which form a part hereof, and in which
are shown by way of illustration embodiments in which the invention
may be practiced. It is to be understood that other embodiments may
be utilized and structural or logical changes may be made without
departing from the scope of the present invention. Therefore, the
following detailed description is not to be taken in a limiting
sense, and the scope of embodiments in accordance with the present
invention is defined by the appended claims and their
equivalents.
[0015] Various operations may be described as multiple discrete
operations in turn, in a manner that may be helpful in
understanding embodiments of the present invention; however, the
order of description should not be construed to imply that these
operations are order dependent.
[0016] The description may use perspective-based descriptions such
as up/down, back/front, and top/bottom. Such descriptions are
merely used to facilitate the discussion and are not intended to
restrict the application of embodiments of the present
invention.
[0017] The terms "coupled" and "connected," along with their
derivatives, may be used. It should be understood that these terms
are not intended as synonyms for each other. Rather, in particular
embodiments, "connected" may be used to indicate that two or more
elements are in direct physical or electrical contact with each
other. "Coupled" may mean that two or more elements are in direct
physical or electrical contact. However, "coupled" may also mean
that two or more elements are not in direct contact with each
other, but yet still cooperate or interact with each other.
[0018] For the purposes of the description, a phrase in the form
"A/B" means A or B. For the purposes of the description, a phrase
in the form "A and/or B" means "(A), (B), or (A and B)". For the
purposes of the description, a phrase in the form "at least one of
A, B, and C" means "(A), (B), (C), (A and B), (A and C), (B and C),
or (A, B and C)". For the purposes of the description, a phrase in
the form "(A)B" means "(B) or (AB)" that is, A is an optional
element.
[0019] The description may use the phrases "in an embodiment," or
"in embodiments," which may each refer to one or more of the same
or different embodiments. Furthermore, the terms "comprising,"
"including," "having," and the like, as used with respect to
embodiments of the present invention, are synonymous.
[0020] In various embodiments, fuel efficiency may be improved by
causing the fuel charge to be more homogeneous in nature, i.e., the
vapor makeup of a given charge has a higher concentration of like
components, and correspondingly, more similar ignition
temperatures. It has been found that as the fuel vapors become more
homogeneous in nature their combustion duration becomes more
uniform and, consequently, it becomes easier to find and maintain
an optimal temperature for increasing the overall efficiency of the
system. Increasing the temperature of the fuel charge to the
optimal temperature may, for instance, increase the effective flame
speed. By optimizing the temperature of a fuel charge and the
timing of a spark assist to initiate ignition of a particular fuel
charge, the combustion duration may be more efficient, i.e., a
shorter and more uniform combustion duration closer to TDC and at a
more optimal crank angle. In various embodiments a variety of fuels
may be utilized, including but not limited to, ethanol based fuels,
fossil fuels including their derivatives, and hybrid fuels. The
invention is not to be limited in this regard.
[0021] In various embodiments, efficiency may be improved for fuel
charges having a range of ignition temperatures by initiating a
chain reaction within the combustion cylinder. For example, given a
fuel charge having a range of components, combustion may be
initiated via a spark which ignites a portion of the fuel charge
and creates a flame front. The flame front and combustion of a
portion of the fuel charge may increase the temperature and
pressure inside the combustion chamber causing components having
lower ignition temperatures to auto-ignite. This auto-ignition may
create more flame fronts and consequently further increase the
temperature and pressure within the cylinder. The further increases
of temperature and pressure may then ignite the components having
higher ignition temperatures. This chain reaction may continue
until substantially all of the charge has been cooperatively
combusted. In various embodiments, as the fuel charge becomes more
homogeneous the number of steps in the chain reaction may decrease
and resultantly may decrease the combustion duration, which in turn
may allow better optimization of the timing and other parameters.
In various other embodiments, such a chain reaction may be
instigated without the use of a spark, for instance by inducting
EGR into the combustion cylinder.
[0022] Combustion duration generally refers to the period of time
it takes for a given fuel charge to combust. Alternatively, and for
the purpose of this explanation, flame speed generally refers to
the rate at which the fuel is burned. Theoretically, for maximum
efficiency, all of the fuel would burn at exactly the same moment.
For example, if the entire fuel charge had a spontaneous ignition
temperature of 500.degree. F., when that temperature is reached in
the combustion chamber all of the fuel would substantially
instantaneously ignite thereby transferring the maximum amount of
energy possible for that given fuel charge. This, however, is not
realistic as fuel contains various components which necessitate
different ignition temperatures, and consequently, ignition at
different times, i.e., a longer combustion duration. For instance,
in current systems, the various components in a charge vary greatly
which can cause the ignition temperature of such a charge to vary,
often times, by several hundred degrees. Thus to burn a charge
having such greatly varied ignition temperatures, more flame fronts
are encountered and a significant amount of energy is expended over
a longer period of time which in turn decreases fuel efficiency. In
various embodiments, improving the homogeneity of the feed stream
such that there is a significantly reduced range of ignition
temperatures within a given fuel charge, thereby reducing flame
fronts and allowing for a more optimal temperature and timing,
substantially improves fuel efficiency.
[0023] In various embodiments, the vapor and/or liquid fuel, prior
to being mixed with air or another oxidizer, may be separated into
generally like components so that the fuel charge is more
homogeneous. Such homogeneity can improve the combustion duration
in the situations where the temperature is below or at the
temperature required for auto ignition of the similar components in
the combustion chamber. In various embodiments, liquid fuel may be
viewed as being comprised of fractions that may vaporize at
different temperatures. This vaporization can be achieved, for
example, by initial heating of liquid fuel at a first temperature
(e.g. 70.degree. F.) and subsequently increasing the temperature as
the differing fractions of the liquid fuel are vaporized and/or
decreased vaporization of the fuel is detected. Referred to herein
as fractionation, applicants have learned that generally
sequentially supplying fractions of vapors to the combustion
chamber will improve efficiency by allowing a more predictable and
uniform combustion duration which may be adjustably triggered to
maximize the energy transfer.
[0024] Though not essential, in various embodiments, fractionation
may help to decrease the combustion duration by reducing the
variation of ignition temperatures within a fuel charge. For
example, while various standard ignition engines may utilize a fuel
charge having ignition temperatures which may vary between
500.degree.-1100.degree. F., fractionation may produce a first
fraction of vapor in which the ignition temperatures may vary
between approximately 500.degree. F.-700.degree. F., and a second
fraction in which the ignition temperatures may vary between
approximately 700.degree.-1100.degree. F. In various embodiments,
the more homogeneous bands may be narrower or wider. Therefore,
when the fuel charge is ignited, the "forest fire" effect mentioned
earlier may be reduced, i.e., the combustion duration is decreased.
With the combustion duration decreased, in various embodiments, the
timing of the spark may be adjusted to place the shortened
combustion duration substantially just past TDC. This also improves
thermal efficiency of the system, as the thermal losses associated
with combustion across different ignition temperatures (which occur
in systems having wide ranging spontaneous ignition temperatures
(e.g. from 500.degree. F., to 1100.degree. F.)), are reduced.
[0025] Heating the fuel and vapor, however, may alter the density
of the fuel vapors. Therefore, to maintain a balance the oxidizer
may also be heated to alter its density. The heating of the
oxidizer may, in various embodiments, work to maintain an AFR that
is compliant with emissions standards and/or maintain currently
accepted AFR. This AFR, in various embodiments, may be controlled
during operation by a density balance control strategy and
implemented by a controller. In various embodiments, the density
balance control strategy may control the varying densities of both
the oxidizer and the fuel vapors by the use of sensors upstream
from the combustion event. These sensors may monitor, for example,
oxygen, temperature, hydrocarbons, and/or vapor density. Through
this monitoring, the sensors may control the heating and/or mixing
events, for both the oxidizer and the fuel vapors, to maintain a
14.7 to 1 AFR. By maintaining this ratio, the quantity of the fuel
charge may be varied, i.e., diluted relative to the cylinder
volume, to achieve efficiency as well as allowing for adjustments
to constantly changing combustion strength. In various embodiments,
sensors may also or alternatively be employed downstream from the
combustion event, and adjustments may be made based on emissions
content.
[0026] In various other embodiments, it has also been found that
increasing the temperature of both the fuel and the oxidizer may
generate additional benefits for combustion engines. Applicants
have discovered that as the vaporized fuel that is being conveyed
to the engine's combustion chamber is mixed with air, condensation
may appear. This can happen, for example, as a result of the air
having a temperature below that of the liquid fuel vaporization
temperature. As the air is mixed with the fuel vapors to achieve
the desired air-to-fuel ratio, the cooler temperature of the air
reduces the temperature of the vaporized fuel and returns it to
liquid form, i.e., it condenses. This condensation may alter the
combustion characteristics and/or homogeneity of the fuel charge,
thus decreasing efficiency and/or flame speed. Accordingly, in
various embodiments, the temperature of the air, vapor, and/or the
mixture may be elevated to a point above that required for
vaporization so the fuels will remain in vaporized form,
homogenously mixed to a desired ratio, and substantially devoid of
condensation. Such heat treatment, i.e., the creation of a higher
temperature, vapor/air mixture may help achieve improved
performance.
[0027] Further such heating of the air supply, vaporized fuel,
and/or air-vaporized fuel mixture may also further enhance the
flame speed of the fuel/air mixture and shorten the combustion
duration. This in turn can extend the "lean limit" (i.e., the
highest air-to-fuel ratio where the engine can perform
satisfactorily, without excessive loss of power, misfire, and/or
unacceptable hydrocarbon emissions). This extension of the lean
limit may have several advantages, including, but not limited to:
(1) improving fuel economy and (2) decreasing the amount of NOx
produced. This pre-heating may also help to achieve some of the
benefits that improve engine performance, including not only
preventing condensing of the fuel, but also increasing the flame
speed.
[0028] In various embodiments, the Exhaust Gas Recirculation
("EGR") amount may be increased, which in turn may increase
efficiency and fuel economy. EGR, effectively, recirculates a
portion of the engine's exhaust (which can be over 1000 F) back to
the engine cylinders. Mixing the incoming fuel charge with EGR
serves to help raise the temperature of the charge in the
combustion chamber to thereby increase the flame speed and decrease
the combustion duration. It also fills the volume of the chamber
with inert gases, mostly nitrogen, carbon dioxide, and steam which
not only reduces the amount of fuel charge used while being diluted
to match the load requirements, but it allows the air to fuel
mixture to remain at a desired stoichiometric ratio (e.g. about
14.7 to 1). In one embodiment, the EGR may be between 15% and
30%.
[0029] In another embodiment, the temperature of the fuel charge
may be raised or lowered by varying both the temperature of the
oxidizer mixed with the fuel and/or the amount of EGR allowed into
the combustion chamber. In effect, the diluted density due to the
increase in temperature of the fuel charge may act as the coarse
adjustment to enable a faster flame speed, while the EGR makes
finer adjustments that may react to quick changes in
conditions.
[0030] These temperatures, in another embodiment, may allow for
increased efficiency when acceleration is needed, and consequently,
the spark plugs (or other ignition source) may be employed to
initiate ignition. In one embodiment, the temperature of the fuel
vapor may be increased to a temperature just below that which is
required to spontaneously ignite the fuel charge, a spark plug may
then initiate ignition of the fuel charge just prior to or at TDC,
and thus create the necessary increased pressure and temperature to
substantially auto-ignite the fuel charge. The increased
temperature of the fuel charge combined with the generally
homogeneous nature of the fuel charge, in accordance with various
embodiments, may lead to a faster flame speed, shorter combustion
duration, increased efficiency, and better control.
[0031] In various other embodiments, the fractionation discussed
above may apply to liquid fuel injected systems, in that the
homogeneity of the fuel charge may improve efficiency. In one
example embodiment, the liquid fuel may be vaporized, or separated
by other methods, and condensed such that the fuel is not
thoroughly mixed, but rather separated by generally like components
having similar vaporization, auto ignition, condensation
temperatures, and/or flame speeds. Such fractions may then be
injected into the combustion chamber for combustion. The
homogeneity of fuel charge allows the temperature of the fuel
charge to be increased so that it approaches, but does not achieve,
a substantially similar auto-ignition temperature for the entire
fuel charge prior to a spark. Consequently, when the spark is
initiated, the decreased combustion duration is allowed to transfer
more energy closer to TDC, thereby allowing for improved
efficiency.
[0032] Additionally, it has been observed that standard onboard
computer systems may further enhance the benefits discussed above.
For example, in standard onboard computer systems, upon periods of
acceleration the amount of EGR is decreased while the timing of the
spark plug is advanced. In one embodiment, the reduction of EGR
necessitates that more fuel be added to the cylinder, therefore
allowing for acceleration. Additionally, the advanced ignition
timing causes the spark to occur sooner in the compression cycle,
which may be prior to the fuel charge meeting the required ignition
temperature and spontaneously combusting. Therefore, in various
embodiments, the reduced EGR and the advanced ignition timing may
have the effect of decreasing the temperature of the fuel charge
and returning the engine to a standard spark initiated ignition
mode. This would not be possible if the fuel charge operated at the
increased temperatures required for auto-ignition, as is done in
current systems (e.g. HCCI). In fact, it might lead to premature
ignition of the fuel charge, and consequently, damage to the
engine. Furthermore, even in a standard ignition mode, a fuel
mixture having a decreased but higher than ambient temperature may
still have the effect of decreasing the combustion duration in
comparison to non-vaporized and/or non pre-heated fuel.
[0033] In an example embodiment, it may be known that vaporizing
fuel at 70.degree. F. generates a more homogeneous vapor which may
substantially spontaneously ignite within a known band of
temperatures (e.g. 500.degree. F.-788.degree. F.). Consequently, a
vapor fuel system in accordance with various embodiments may
vaporize a first fraction of gas and adjust the operating
conditions to heat the vapor and/or an oxidizer so that the mixture
is in a ratio of 14.7-1 and approaches a temperature of 450.degree.
F., a temperature which approaches but does not achieve spontaneous
ignition. Accordingly, in various embodiments, an internal
combustion engine having a combustion chamber may then induct the
homogenous fuel charge (e.g. fractionized fuel vapors) into the
combustion chamber. Thereafter a spark from a spark plug may be
used to initiate ignition of the fuel charge. In such an instance,
the rate at which the entire fuel charge is expended may be
substantially increased thereby increasing the overall efficiency
of the engine. As the combustion duration continually decreases,
the timing may be changed to position the combustion closer to TDC
in order to maximize the energy transfer.
[0034] In various embodiments, as thermal efficiency increases, the
pressure due to combustion will increase while the duration of the
combustion event will decrease. As the combustion duration
decreases, the ignition timing may be adjusted to move ignition
closer toward TDC, and when the fastest flame speed and shortest
combustion duration is reached (e.g. at or near auto ignition),
ignition may occur at or close to TDC. In various embodiments, a
sensor or sensors and logic may recognize the increased pressure
and, in addition to the aforementioned timing change, increase the
amount of EGR so the combustion pressure can match the power that
would be produced by a normal combustion. The additional EGR will
act as filler and substantially dilute the quantity of fuel and air
within the cylinder thereby reducing the quantity of fuel consumed,
thus improving efficiency while matching the power consumed by
standard methods. Moving the ignition timing to a point closer to
TDC and diluting the fuel and air quantity by heating the charge,
which thus changes the density, and adding EGR are critical
elements to matching the power requirement, protecting the engine
and improving fuel economy.
[0035] Reference is made to FIG. 1, which provides a block diagram
of the components of a system in accordance with embodiments of the
present invention. A combustion chamber 110 may be coupled to a
mixer 108 which combines heated air from air intake 104 and air
heater 106 with vaporized and/or fractionated fuel from fuel tank
100 and vaporization chamber 102. Additionally, in various
embodiments an exhaust system 112 may be coupled to the combustion
chamber 110 and/or a mixer 108. The exhaust system 112 allows for
recirculation of exhaust, i.e., Exhaust Gas Recirculation ("EGR").
In various embodiments exhaust system 112 may be coupled, directly
or indirectly, to other components. The invention is not to be
limited in this regard.
[0036] In various embodiments, the air (or other oxidizer) mixed
with the fuel vapor may be heated by a dedicated heat source (e.g.
heating coils disposed within the air flow) or via passive heating
from engine or other vehicle components. Further, the air may be
heated (e.g. by the engine) prior to air intake 104. In one
embodiment a heat source 106 may control the temperature of the air
flow and elevate the temperature of the air supply as deemed
necessary based on the content of the emissions and/or vaporization
temperature of the fractionated fuel vapors. In various
embodiments, the air inflow may be controllably elevated in
temperature from, for example, a range of about 60.degree. F. to
80.degree. F. to a temperature of about 100.degree. F. to
120.degree. F., or higher. Again, the temperature of the air supply
may vary depending on the emission content and/or the temperature
required for vaporizing and mixing with the instant fraction of
fuel, and may be controlled based thereon. In various embodiments,
the air and/or oxidizer may be controllably heated in order to
maintain a desired oxidizer-to-fuel ratio. In various other
embodiments, the intake air need not be heated.
[0037] In various embodiments, the liquid fuel in fuel tank 100 may
be vaporized in vaporization chamber 102. The vaporization chamber
102 may include a number of heating sources (not shown) to
controllably heat the liquid fuel including but not limited to
engine component proximity, engine fluids, electrical circuits,
independent heating devices, and/or heated air from intake 104 or
air heater 106. In various embodiments, the vaporization chamber
102 may vaporize the fuel by fractionation, i.e., heating the fuel
in increments so as to improve the homogeneous nature of the fuel
vapors. More specifically, in one embodiment, fuel may be
transferred from fuel tank 100 to vaporization chamber 102. The
fuel may occupy the lower half of the tank, and a heating element
and temperature sensor (not shown) may be set to incrementally
increase the temperature settings for heating the fuel in the
vaporization chamber 102 thereby causing fractionation of the fuel.
As mentioned previously, the fractionized fuel is more homogeneous
in nature which improves the combustion duration, and consequently,
efficiency. In various embodiments, a sensor may monitor various
characteristics of the created vapor, and control the further
vaporization of the fuel to maintain a desired mixture density
and/or homogeneity range.
[0038] In one embodiment, the air heater 106 may be coupled to the
vaporization chamber 102 to facilitate conveyance of the fuel
vapors to the mixing chamber 108 and subsequently to the combustion
chamber 110. While the air-fuel mixture is being conveyed, however,
as previously discussed, there may be the possibility that a part
of the mixture may condense to liquid form prior to entering the
mixing chamber 108 and/or the combustion chamber 110. In one
embodiment, to prevent condensation from taking place, the air
heater 106 may establish a temperature of the air at or above the
temperature of the of the fractionated fuel vapors. In another
embodiment, the fuel vapors carried by the heated air to the mixer
108 may be heated again to a temperature above that which the
fractionated fuel was vaporized. This may help to improve burning
efficiency as well as prevent condensation in the mixing chamber
itself. In various embodiments the mixer 108 may combine the heated
intake air and the heated fractionated fuel to form a fuel charge.
This mixture may be controlled, by a controller (not shown), in
order to maintain a desired oxidizer-to-fuel ratio.
[0039] In one embodiment, after the fuel vapors and/or fuel charge
have been passed to the combustion chamber 110, a spark plug (not
shown) may perform a spark to substantially ignite the fuel charge.
The timing of the spark may be adjusted, by a controller, so
combustion of a fuel charge may occur after and/or at an optimal
crank angle. In other embodiments, the adjustment of the spark may
be based on at least the characteristics of the fuel charge/fuel
vapors.
[0040] After combustion, the exhaust may then be transferred to an
exhaust system 112. The exhaust system, in various embodiments, may
dispose of the exhaust or recirculate the exhaust gas back to the
combustion chamber 110 or the air vapor mixture that is to be
combusted. In one embodiment, Exhaust Gas Recirculation ("EGR") may
be used to improve efficiency and fuel economy. In various other
embodiments, the amount of EGR that is circulated may be determined
and controlled by onboard computers and a series of valves (not
shown). The optimal percentage of EGR varies and is limited by the
fuel characteristics such as the fuel charge's auto-ignition
temperature, and the amount of fuel required for various load
conditions. Additionally, in other embodiments, the EGR may be
circulated to the mixer 108 to increase the temperature of the fuel
and/or oxidizer prior to the fuel charge entering the combustion
chamber 110.
[0041] In various embodiments, one or more sensors may be disposed
in the feed stream for the combustion chamber 110, and adapted to
sense a characteristic of the fuel charge, such as hydrocarbon
content, temperature, density, ignition temperature, air to fuel
ratio, etc. The sensors may be coupled to an onboard computer,
which may in turn adjust various parameters to improve the
combustion of the particular charge. For example, if the amount of
hydrocarbons in the sensed fuel charge is out of balance, which
could result in an incorrect ignition, the amount of EGR may be
increased or decreased, the timing may be advanced or retarded,
and/or the temperature of the fuel charge may be otherwise
increased or decreased. In another example, the density or the
temperature of the charge could be sensed and corrected as desired
in order to achieve more optimal combustion at normal
stoichiometric conditions.
[0042] FIG. 2 is a graph illustrating a relationship between
diluting an amount of fuel to be combusted in a cylinder and the
need for more efficient combustion of the fuel to maintain an
acceptable level of performance. In various embodiments this may be
achieved by adjusting the combustion of the diluted fuel charge
based on various characteristics of the fuel charge.
[0043] In various embodiments, dilution of a fuel charge may result
from vaporizing an amount of fuel and/or mixing the fuel with a
heated oxidizer. For example, as an amount of fuel changes phase
from a liquid to a gas its density will be reduced. Mixing the fuel
with a heated oxidizer may also or additionally reduce the fuel's
density. In various embodiments, the fuel and/or oxidizer may be
diluted in order to maintain a desired oxidizer-to-fuel ratio, such
as for example, about 14.7-to-1. This may allow for the
optimization of power and fuel economy while avoiding known NOX
issues if a standard catalytic converter is used. With the fuel
and/or oxidizer having reduced densities, due to their increased
temperatures, the result may be less fuel and oxidizer, by weight,
required to fill the combustion cylinder. In this manner, less fuel
may be consumed thereby increasing efficiency.
[0044] In various embodiments, another effect of the increased
temperatures of the fuel and/or oxidizer may be a shorter and more
efficient combustion duration. Improved combustion duration may
allow a diluted fuel charge to provide acceptable levels of
performance by combusting the diluted fuel at an optimized crank
angle (e.g. 3 to 15 degrees past TDC). In this manner, increasing
the temperature of the fuel and/or oxidizer may not only serve to
dilute the fuel charge, but also provide a mechanism for increasing
the efficiency of a combustion event to maintain an acceptable
performance level. As previously mentioned, in various other
embodiments, EGR may also be used to dilute and increase the
temperature of a fuel charge.
[0045] As shown in FIG. 2, a performance line 204 is illustrated.
This may represent an acceptable level of performance for a given
fuel charge. At line 212, a fuel charge may be diluted by any of
the methods previously discussed. At line 212, because the fuel
charge has been diluted, there is a need for increased efficient
combustion of the fuel charge to produce the desired amount of
performance. Similarly, at line 208 a fuel charge is represented as
being further diluted with respect to line 212. Therefore, to
maintain the same level of performance with respect to line 212, a
further increase in temperature and/or efficient combustion may
also be needed. Consequently, FIG. 2 illustrates that as a fuel
charge becomes further diluted, there is a need for a more
efficient combustion of the diluted fuel charge to maintain a
desired level of performance. As illustrated, line 208 produces the
same performance with less fuel being utilized. This relationship
is more fully described with reference to FIGS. 3 and 4.
[0046] It should be understood that FIG. 2 is provided only for the
purpose of demonstrating a general relationship between fuel
dilution and a need for efficient combustion of the diluted fuel.
FIG. 2 is not intended to be an exact representation of the
illustrated relationship as those of skill in the art will readily
recognize. It is merely provided for ease of understanding.
Furthermore, the figure may only illustrate a portion of the
relationship.
[0047] Referring now to FIGS. 3 and 4, a series of graphs 1-4
illustrate the effect of increased flame speed on the time required
to completely combust (combustion duration) an identical quantity
of fuel. Graphs 5-8 of FIG. 4 illustrate the corresponding in
cylinder pressure ("ICP") of the combustion events in FIG. 3,
respectively.
[0048] Referring first to Graph 1, a typical, slower flame
propagation event is illustrated. The flame front begins at the
spark plug and continues until the fuel has been combusted or the
next cycle begins. The combustion lasts well past the optimal crank
angle (e.g. 45-50 degrees past TDC). Because the combustion
duration is long, i.e., the fuel is still combusting as the piston
moves away from TDC, the ICP is also relatively low as seen in
graph 5 of FIG. 4.
[0049] Referring now to Graph 2, a more ideal combustion event is
illustrated. Graph 2, demonstrates a nearly spontaneous ignition,
or auto-ignition, of the same quantity of fuel as combusted in
graph 1. As shown, the combustion duration is much faster, i.e.,
the entire quantity of fuel is consumed faster. This fast
combustion duration places most of the combustion just passed TDC.
This leads to an increase in pressure at TDC as seen in FIG. 4,
graph 6. In comparing graph 6 with graph 5, it can be seen that as
the combustion duration is decreased and the timing optimized at
TDC, the same amount of fuel creates a greater amount of pressure
over a smaller change in crank angle, and consequently, the engine
power is increased.
[0050] Graphs 3 and 4 illustrate a spark assisted auto-ignition as
discussed above with reference to various embodiments. In the
graphs, the conditions within the cylinder are very close to those
needed to support auto-ignition when the spark plug ignites prior
to TDC. In graph 3, the resulting flame front quickly raises the
temperature and pressure to a point where the remaining fuel
substantially auto-ignites. In graph 4 the combustion event
requires more fuel be burned as a result of the flame in order to
achieve the conditions required to support auto-ignition, increased
pressure and temperature. Graph 4 is therefore, not as efficient as
graph 3. This becomes apparent when comparing the ICPs, graphs 8
and 7. Because the combustion duration of graph 4 is slightly
longer than that of graph 3, the ICP of graph 8 is slightly less
than that of graph 7, and consequently, slightly less efficient.
While graph 8 is slightly less efficient than graph 7, it can be
seen that both Graphs 8 and 7 have ICPs greater than that of graph
5, the slow flame propagation event.
[0051] The increases of ICP in graphs 6, 7, and 8, relative to
graph 5, illustrate an increase in efficiency that may be possible.
More specifically, in graphs 6, 7, and 8, the fuel may be diluted
to match the ICP of graph 5. This translates into less fuel
accomplishing the same amount of work as the typical flame
propagation event.
[0052] These graphs are not intended to be exact illustrations of
the occurrences but rather a general illustration of the effect of
various combustion durations/flame speeds.
[0053] Referring now to FIG. 5, a flow diagram of a combustion
operation 500 is illustrated in accordance with various embodiments
of the present invention. The operation may begin at block 502, and
progress to block 504 where the temperature of the fuel charge is
adjusted. In various embodiments, adjusting the temperature of the
fuel charge may comprise heating both an oxidizer component and/or
a fuel component prior to inducting the fuel charge into the
combustion chamber. In various embodiments, this heating may be
accomplished by combining exhaust-gas-recirculation with the
oxidizer and/or fuel component.
[0054] At block 506, in accordance with various embodiments,
adjustments to the temperature and/or amounts of oxidizer and/or
fuel may be monitored and controlled to maintain a desired
oxidizer-to-fuel ratio. If the desired ratio is not achieved, the
operation may return to block 504 for further adjusting of the fuel
charge. In various embodiments the fuel component may be
fractionated prior to being heated, or the fuel component may be
fractionated and then condensed back into liquid form. In such a
manner the fuel charge may include a liquid fuel component or a
vapor fuel component.
[0055] In various embodiments, after the desired oxidizer-to-fuel
ratio is achieved, the operation may continue to block 508 where
the fuel charge is inducted into the combustion chamber. Once
inside the combustion chamber, the timing of the combustion event
may be adjusted to substantially auto-ignite the fuel charge based
at least on characteristics of the fuel charge 510. In various
embodiments the characteristics of the fuel charge may include the
homogeneity of the fuel charge, the temperature of the fuel charge,
the combustion duration and/or flame speed of the fuel charge.
These characteristics may allow the timing of the initiation of the
combustion event to be adjusted so that the fuel charge
substantially auto-ignites after a piston reaches top-dead-center
in the combustion chamber.
[0056] In various embodiments, after the timing of the combustion
event has been adjusted to maximize efficiency, the operation may
initiate the combustion event in block 512. The initiating of the
combustion event, in one embodiment, comprises initiating a spark
to substantially auto-ignite the fuel charge. The operation may
then end at block 514.
[0057] Referring now to FIG. 6, a flow diagram of a combustion
operation 600, in accordance with various embodiments, is
illustrated. The operation may begin at block 602 and proceed to
block 604 where a decision is made as to whether the combustion
engine is operating in a first mode of operation or a second mode
of operation. If the combustion engine is operating in a first mode
of operation, the method may continue to block 606 where an amount
of preheated fuel is inducted into a combustion chamber. In various
embodiments, the amount of preheated fuel may be mixed with an
oxidizer and have an oxidizer-to-fuel ratio of approximately
14.7-1. Subsequently, at block 608, an amount of
exhaust-gas-recirculation is combined with the amount of preheated
fuel. At block 616, the amount of fuel may be ignited. In various
embodiments this may be due to the increase in temperature provided
by the EGR, or in other embodiments a spark may be used in
combination with EGR to ignite the fuel. The timing of the
combining of the exhaust-gas-recirculation may be adjusted based at
least on characteristics of the amount of preheated fuel. In other
embodiments, a spark may be used in conjunction with the amount of
exhaust-gas-recirculation to substantially ignite the amount of
preheated fuel, as stated above. In such a manner, the first mode
of operation may include the spontaneous ignition of a fuel charge.
The method may then loop back to decision block 604 where it may be
decided, once again, whether a first mode operation or a second
mode of operation is desired.
[0058] If a second mode of operation is desired, the method may
continue to block 610 where an increased amount of preheated fuel
is inducted into the combustion chamber. The increased amount of
fuel may be needed, in various embodiments, for increased loads,
such as during periods of acceleration. After the increased amount
of fuel is inducted into the combustion chamber, the method may
continue to block 612 where a decreased amount of
exhaust-gas-recirculation is combined with the increased amount of
preheated fuel. In various embodiments, the combination of an
increased amount of preheated fuel and a decreased amount of
exhaust-gas-recirculation may substantially reduce the occurrence
of a spontaneous ignition, e.g., the decreased amount of
exhaust-gas-recirculation may be incapable of substantially
igniting the increased amount of preheated fuel. The method may
then continue to block 614 where a spark may be performed to
substantially ignite the fuel charge. In various embodiments, the
spark may be advanced to occur sooner in a compression cycle. In
one embodiment the advancement of the spark may be controlled by
standard onboard computer systems. After ignition of the fuel
charge, the method may loop back to decision block 604.
[0059] Therefore, in various embodiments, a method of operating an
internal combustion engine comprises; creating a generally
homogenous vapor or liquid fuel stream (e.g. by fractionizing the
fuel); mixing the fuel vapors with heated air to increase the
temperature of the air fuel mixture; inducting the air fuel mixture
into a combustion chamber; and combusting the air fuel mixture to
generate energy has been shown and described. Embodiments may
maintain the pre-combustion temperature of the mixture at or near
the auto-ignition temperature of a given charge, as well as improve
overall efficiency by increasing the flame speed and reducing the
overall combustion duration. Coupled with being able to control the
timing of the combustion further improves efficiency and the
ability of the system to respond to transient conditions.
[0060] Although certain embodiments have been illustrated and
described herein for purposes of description of the preferred
embodiment, it will be appreciated by those of ordinary skill in
the art that a wide variety of alternate and/or equivalent
embodiments or implementations calculated to achieve the same
purposes may be substituted for the embodiments shown and described
without departing from the scope of the present invention. Those
with skill in the art will readily appreciate that embodiments in
accordance with the present invention may be implemented in a very
wide variety of ways. This application is intended to cover any
adaptations or variations of the embodiments discussed herein.
Therefore, it is manifestly intended that embodiments in accordance
with the present invention be limited only by the claims and the
equivalents thereof.
* * * * *