U.S. patent application number 10/245891 was filed with the patent office on 2003-03-20 for fuels for homogeneous charge compression ignition engines.
This patent application is currently assigned to SOUTHWEST RESEARCH INSTITUTE. Invention is credited to Erwin, Jimell, Ryan, Thomas W. III, Stanglmaier, Rudolf H..
Application Number | 20030052041 10/245891 |
Document ID | / |
Family ID | 23256267 |
Filed Date | 2003-03-20 |
United States Patent
Application |
20030052041 |
Kind Code |
A1 |
Erwin, Jimell ; et
al. |
March 20, 2003 |
Fuels for homogeneous charge compression ignition engines
Abstract
A fuel for a homogeneous charge compression ignition engine
having a 95 V% distilled temperature by boiling point measurement
in the range of about 35.degree. C. to about 350.degree. C., a
cetane number in the range of about 2 to about 120, and an octane
number in the range of 10 to about 110. The invention also relates
to a method of operating a homogeneous charge compression ignition
engine of mixing a fuel with air and feeding the fuel into a
combustion chamber
Inventors: |
Erwin, Jimell; (San Antonio,
TX) ; Ryan, Thomas W. III; (San Antonio, TX) ;
Stanglmaier, Rudolf H.; (San Antonio, TX) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
SOUTHWEST RESEARCH
INSTITUTE
San Antonio
TX
|
Family ID: |
23256267 |
Appl. No.: |
10/245891 |
Filed: |
September 18, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60322757 |
Sep 18, 2001 |
|
|
|
Current U.S.
Class: |
208/15 |
Current CPC
Class: |
C10L 1/08 20130101; F02B
1/12 20130101 |
Class at
Publication: |
208/15 |
International
Class: |
C10L 001/04 |
Claims
What is claimed is:
1. A fuel for a homogeneous charge compression ignition engine
having a 95% ASTM D 86 boiling point of about 35.degree. C. to
about 350.degree. C., a cetane number in the range of about 2 to
about 170, and an octane number in the range of about 2 to about
110.
2. The fuel according to claim 1, wherein the 95% ASTM D 86 boiling
point is about 180.degree. C. to about 350.degree. C.
3. The fuel according to claim 2, wherein the 95% ASTM D 86 boiling
point is about 225.degree. C. to about 350.degree. C.
4. The fuel according to claim 1, wherein the cetane number is from
about 47 to about 170.
5. The fuel according to claim 1, wherein the cetane number is from
about 20 to about 70.
6. The fuel according to claim 1, wherein the cetane number is from
about 2 to about 20.
7. The fuel according to claim 4, wherein the octane number is from
about 2 to about 24.
8. The fuel according to claim 5, wherein the octane number is from
about 12 to about 82.
9. The fuel according to claim 6, wherein the octane number is from
about 63 to about 110.
10. A fuel for a homogeneous charge compression ignition engine
having an elevated pressure autoignition temperature, or an
equivalent measure, of about 400.degree. C. to about 800.degree.
C.
11. A method of operating a homogeneous charge compression ignition
engine comprising mixing a fuel with air and feeding the fuel into
a combustion chamber of the homogeneous charge compression ignition
engine, wherein the fuel comprises a 95% ASTM D 86 boiling point of
about 35.degree. C. to about 350.degree. C., a cetane number in the
range of about 2 to about 170, and an octane number in the range of
about 2 to about 110.
12. The method according to claim 11, wherein the 95% ASTM D 86
boiling point is about 180.degree. C. to about 350.degree. C.
13. The method according to claim 12, wherein the 95% ASTM D 86
boiling point is about 225.degree. C. to about 350.degree. C.
14. The method according to claim 11, wherein the cetane number is
from about 47 to about 170.
15. The method according to claim 11, wherein the cetane number is
from about 20 to about 70.
16. The method according to claim 11, wherein the cetane number is
from about 2 to about 20.
17. The method according to claim 14, wherein the octane number is
from about 2 to about 24.
18. The method according to claim 15, wherein the octane number is
from about 12 to about 82.
19. The method according to claim 16, wherein the octane number is
from about 63 to about 110.
20. The method according to claim 11, having an elevated pressure
autoignition temperature, or an equivalent measure, in the range of
400.degree. C. to 800.degree. C.
21. The method according to claim 11, wherein the fuel is
controlled by one or more special purpose integrated circuits.
22. A method of operating a homogeneous charge compression ignition
engine comprising mixing a fuel with air and feeding the fuel into
a combustion chamber of the homogeneous charge compression ignition
engine, wherein the fuel comprises a 95% ASTM D 86 boiling point of
about 185.degree. C. to about 350.degree. C., a cetane number in
the range of about 2 to about 160, and an octane number in the
range of 2 to about 103.
23. The method according to claim 16, wherein the feeding of the
fuel is controlled by one or more integrated circuits selected from
the group consisting of programmable logic devices PLDs,
programmable logic arrays PLAs or special purpose control devices.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates generally to an internal combustion
engine fuel that is used in homogenous charge compression ignition
(HCCI) engines, and more particularly to materials that constitute
useful fuels for use in HCCI engines and variations for controlling
the efficient use of the fuel in the HCCI engines.
[0003] 2. Description of Related Art
[0004] Air pollution has become one of the more serious problems
affecting the United Sates and other countries, especially in some
large urban areas where air pollution has reached critical levels.
In the United States, the primary responsibility for setting and
maintaining air quality standards rests on the Environmental
Protection Agency (EPA). Once the standards are set, the state and
local governments are responsible for determining the means of
achieving the air pollution standards.
[0005] In the last century, transportation relied primarily upon
the internal combustion engine to provide power for mobility. This
reliance developed into a mature and well known science in the
field of engineering related to the internal combustion engine.
Rarely are there "new" concepts for the internal combustion engine
because of the advanced stage of engine development, but
alternative models are emerging. For instance, an increase in
engine power or reduced size/weight may be desired, but may require
both increased cost and decreased fuel efficiency of the
engine.
[0006] The challenge is to balance the demands of the government in
achieving higher fuel efficiency and emissions standards with
consumers' demands for high engine power. The traditional vehicle
engines are not able to be easily manipulated to achieve a
cost-efficient balance of the competing demands. Thus, the search
is now to develop new efficient engines that are able to balance
new government standards with consumer demand at a cost-effective
level.
[0007] The traditional combustion engines have been either the
Diesel or the Otto engines. Although each engine has similar basic
structures and workings, the operating properties of each differ
greatly.
[0008] The Diesel engine, also known as a reciprocating piston,
compression ignition engine, controls the start of combustion by
timing the fuel injection. The Otto engine, also known as a rotary
internal or spark ignition combustion engine, controls the start of
combustion by timing the spark.
[0009] There are advantages and disadvantages of each type of
engine or cycle. For example, an Otto cycle system is able to
achieve much lower NO.sub.x and particulate emissions level than a
diesel engine. These low levels are possible because the Otto cycle
engines can take advantage of exhaust gas after treatment systems
that will not work on diesel engines. However, Otto cycle engines
typically have lower efficiencies than comparable diesel
engines.
[0010] The diesel cycle, on the other hand, has a much higher
thermal efficiency than the Otto cycle. The diesel cycle uses
higher compression ratios than the Otto cycle (which are kept low
to avoid "knocking"). The diesel cycle controls the power output
without a throttle, therein eliminating throttling losses and
achieving higher efficiency at part load. Usually diesel cycle
engines do not achieve low NO.sub.x and particulate emissions. The
diesel cycle requires a mixing control at a very fuel rich
equivalence ratio, thereby resulting in typically higher
particulate emissions.
[0011] Considering the disadvantages of each of the traditional
combustion cycles, interest is now turning to a type of engine
utilizing premixed charge compression ignition (PCCI), also known
as homogeneous charge compression ignition (HCCI), active
thermo-atmosphere combustion (ATAC), Toyota-Soken (TS), and
compression-ignited homogeneous charge (CIHC). PCCI engines
initiate combustion using a well premixed fuel/air mixture that is
mixed in the intake port or the cylinder before actual
autocompression ignition of the mixture. The actual mixture may
vary from being homogeneous to less than homogeneous with some
degree of stratification.
[0012] What is desired is a method and system for producing useful
and efficient fuels for use in HCCI cycles. It is further desired
to have a system for the efficient use of the fuel in a HCCI cycle
and therein lower emissions, especially of NO.sub.x and particulate
matter.
SUMMARY OF THE INVENTION
[0013] This invention concerns fuels for engines that operate in a
homogenous charge compression ignition (HCCI) mode, methods for
defining such fuels, for the combustion of these fuels, and for
regulating that combustion that engenders the successful and
satisfactory operation of HCCI engines.
[0014] The ability of the HCCI engine to develop useful rotary
power and to do so with lowered emissions of partially oxidized
fuel and soot, and lowered emissions of nitrogen oxides than
comparable displacement Otto cycle or diesel cycle depends on a
suitably produced fuel. Furthermore, the Otto cycle and the diesel
cycle require fuels that exclusively limit the fuel preparation
process by relegating available blendstocks to one use or the other
thereby restricting the optimal use of available fuel sources. The
HCCI engines may use fuels from sources otherwise incompatible if
assigned to fuel blends designed for Otto cycle and diesel cycle
engines.
[0015] The present invention is directed to overcoming the problems
set forth above. This invention sets forth the range of fuel
properties for use in HCCI engines and variations for their
efficient use as fuel in HCCI engines. Based upon the observations
made in numerous experiments of the inventors, specific properties
and relations among the properties were discerned and are set forth
herein.
[0016] In particular, over 500 engine experiments were performed
using a wide variety of fuels in a successful effort to determine
the important fuel properties and to define the limits for these
properties as specified in this patent.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0017] The fuels, deriving from the various exemplary embodiments
of the present invention, leave the liquid phase upon introduction
into the appropriate locations in the intake manifold or the
combustion chamber and become vapor (or gas), or nearly totally
vaporize, before the onset of the combustion event. Once exposed
through elevation of temperatures and pressure to the conditions
required for the onset of autoignition, the air-fuel mixture begins
to react and completes combustion before extreme temperatures are
reached that lead to greater formation of nitrogen oxides. At the
same time, the air-fuel mixture resists the overly rapid combustion
that produces premature ignition that is counterproductive and
damaging to the engines.
[0018] While there are several different names for this type of
process and several different methods available to control and
initiate this type of reaction, they all share the common features
of premixing some, or all, of the fuel and compression heating
initiation of the reaction. This type of reaction will be referred
to herein as HCCI irrespective of other names by which it might be
called such as Premixed Charge Compression Ignition (PCCI or
PMCCI), Controlled Auto Ignition (CAI), Premixed Charge Compression
Reaction Engines (PCCRE), and other names. The distinguishing
feature of these combustion modes is that a fraction of the fuel is
introduced into the combustion chamber prior to the start of
combustion, and that this fuel-air mixture is ignited by
compression. That is, ignition is achieved without the aid of a
spark plug or other active ignition sources (although the use of
passive ignition aides such as glow-plugs, surface heaters, or
catalytic coatings are covered within the scope of these combustion
modes). The fuel can be introduced either upstream of the intake
valves (through carburetors, port-fuel injectors, mixers, etc.), or
directly in cylinder through the use of direct fuel injectors.
[0019] The fundamental HCCI characteristics are that a large
majority of the fuel is premixed with the air to form a combustible
mixture throughout the combustion chamber, and combustion initiates
by compression.
[0020] U.S. Pat. No. 6,273,076 to Beck et al. (hereinafter "Beck"),
incorporated herein in its entirety, describes the general concept
of homogeneous charge compression ignition engines and an improved
performance by optimizing an excess air ratio and/or intake air
charge temperature. However, Beck does not describe or suggest any
particular fuels for homogeneous charge compression ignition
engines other than identifying that the fuel should be compression
ignitable.
[0021] U.S. Pat. Nos. 6,276,334 and 6,286,482, both to Flynn et al.
and both incorporated herein in their entirety, describe some of
the hardware aspects of homogeneous charge compression ignition
engines. The Flynn patents also describe a limited number of fuel
characteristics and the possible reactivity control achieved by
mixing fuels. However, the Flynn patents do not teach any
particular fuel properties for homogeneous charge compression
ignition engines.
[0022] The HCCI cycle is not greatly affected by the fuel timing
delivery as compared to a diesel cycle. The well mixed and nearly
homogeneous fuel/air mixture of the HCCI delivers fewer emissions
as opposed to the diesel cycle, and offers a potentially excellent
fuel efficiency.
[0023] Both the Otto and diesel cycles require fuels exclusively
designed for use in their respective engines. HCCI engines,
however, require fuels coming from otherwise incompatible fuel
blends if designed for Otto or diesel cycles.
[0024] The description of the various exemplary embodiments of the
present invention herein are intended to describe the preferred
novel fuels for running an HCCI engine at an optimum level of
efficiency and practicality. However, fuels typically fed into Otto
cycle engines such as gasoline, having ignition qualities of octane
numbers centered on the range of antiknock index 83 to 97
associated with a usual boiling point range of 30.degree. C. to
225.degree. C. and diesel cycle engines such as a diesel fuel
having ignition qualities of cetane numbers centered on the range
of 30 to 48 associated with the approximate boiling point range of
175.degree. C. to 340.degree. C. may also be fed into HCCI engines.
However, feeding conventional Otto and diesel cycle fuels into an
HCCI engine typically will decrease efficiency of the engine and
increase emissions outputs of pollutants. Thus, feeding
conventional Otto or diesel cycle fuels into a HCCI cycle engine is
not optimal for efficiency and environmental concerns, but can
nonetheless be performed.
[0025] Further, various exemplary embodiments of the invention
comprise engine cycles wherein there is a single combustion event
and multiple combustion events wherein at least one of them can be
exemplified as HCCI.
[0026] For the optimum use of the HCCI fuels, the orderly operation
of the HCCI engines may depend on which engine configuration is
selected. For example, through the careful regulation of the
incoming fuel-air charge, including temperature and pressure, an
efficient match of the engine operation with the fuel constitution
is achieved. Consistent with fuels chosen and operating mode, other
governors of combustion may be used including, for example,
ignition initiators, auxiliary fuel injectors, compression ratio
variation, exhaust gas recirculation (EGR) or inert gas
introduction, or variable valve timing strategies to enhance the
HCCI engine operation.
[0027] In accordance with various exemplary embodiments of the
invention, the properties of the preferred novel HCCI fuels are so
arranged to minimize the engine-out or vehicle-out emissions of
pollutants including, for example, CO, various hydrocarbons,
carbon-containing particles, nitrogen oxides, and the like.
Further, the boiling point range, boiling point distribution,
volatility, and ignition indices may be configured to
simultaneously minimize the production of the designated
pollutants. The engine operating mode to befit these fuel
compositions includes, for example, increased intake charge
temperature, fuel-air ratio, speed, and intake charge temperature,
wherein each is selected to control the onset of combustion and to
produce more complete combustion at lower adiabatic flame
temperatures.
[0028] In accordance with other various exemplary embodiments of
the present invention, the properties of the fuels are so arranged
to allow for maximizing the total efficiency of energy production,
considering the intrinsic efficiency of the fuels combusting in the
engine and the production of the fuels themselves. The specified
properties include, for example, but are not limited to, the
boiling point range, boiling point distribution, volatility, and
ignition indices chosen to incorporate a variety of blendstocks
including, for example, petroleum-derived stocks like straightrun
naphtha, dehexanizer effluents, cracked stocks, distillate stocks,
polymer and other gasoline, and other refinery stocks, whether
directly derived from the refinery source or the object of further
processing. For example, these may include isomerization and other
composition-altering steps; and hydrocarbon stocks like natural
gasoline, gasifier liquids, synthesized components whether from
degradatory processing, e.g., destructive distillation of natural
products or wastes or synthetic processing, e.g., Fischer-Tropsch
synthesis or other synthetic processes; non-petroleum sources like
alcohols, various oxygenates, and other stocks having more atomic
species than carbon and hydrogen; and additive compounds like
octane number altering constituents and cetane number changing
constituents.
[0029] According to exemplary embodiments of the invention, an
internal combustion engine fuel suitable for use in an HCCI mode
preferably comprises one or more of the properties listed
hereafter.
[0030] The engine fuel can have an evaporative nature or
characteristic, sufficient to allow essentially all the fuel in
each intake charge to convert to a vapor phase before the onset of
combustion. The fuel can have an ignition delay sufficiently long
that the onset of combustion shall be achieved by the engine fuel
after the moving piston has exceeded the point of maximum
mechanical compression in the movement cycle. Further, the engine
fuel may have an ignitability sufficiently high that uniform
continuous combustion is achieved throughout the fuel-air charge
filling the piston cylinder once ignition commences.
[0031] The preferred engine fuel used in accordance with the
exemplary embodiments of the present invention preferably comprises
a fuel having:
[0032] (1) a boiling temperature range such that the 95% ASTM D 86
boiling points are about 35.degree. C. to about 350.degree. C.,
preferably about 180.degree. C. to about 350.degree. C., more
preferably about 225.degree. C. to about 350.degree. C.;
[0033] (2) a cetane number as measured by ASTM D 613 or similar
measurement of ignition characteristics, of about 2 to about 170,
preferably 2 to about 70, more preferably 20-70, wherein the cetane
number is based on a mixture of hydrocarbons, oxygenates, and/or
other major blending components. Further, the cetane number can be,
but is not necessarily, influenced by the addition of one or more
minor components and/or additives that can change the cetane
number;
[0034] (3) an octane number as measured by antiknock index defined
in ASTM D 4814 or similar measurement of ignition characteristics,
of about 10 to about 110, preferably 12 to about 110, more
preferably about 12 to 82, wherein the octane number is based on a
mixture of hydrocarbons, oxygenates, and/or other major blending
components.
[0035] An alternative method for measuring the ignition
characteristics of the fuel embodied in this invention, the
elevated pressure autoignition temperature (EPAIT), may also be
used to characterize the possible and preferred fuels for HCCI
engines. The method is described by Ryan and Matheaus (Ryan, T. W.,
III and Matheaus, Andrew C., "Fuel Requirements for HCCI Engine
Operation", Thiesel 2002, Valencia, Spain, Sep. 11-14, 2002),
incorporated herein in its entirety, in its details leading to the
present invention. The important characteristics for an HCCI fuel
are ignition delay time and temperature at the start of reaction.
Both characteristics are measured in the process of determining
EPAIT. The fuels of the invention possess EPAIT in the range of
400.degree. C. to 800.degree. C.
[0036] In various exemplary embodiments of the present invention,
when the cetane number of the fuel is from about 47 to about 170,
the octane number is preferably from about 2 to about 24. In other
various exemplary embodiments of the present invention, when the
cetane number of the fuel is from about 20 to about 70, the octane
number is preferably from about 12 to about 82. In yet other
various exemplary embodiments of the present invention, when the
cetane number of the fuel is from about 2 to about 20, the octane
number is preferably from about 63 to about 110.
[0037] According to exemplary embodiments of the invention, the
engine fuel can be utilized to work in combination with one or more
engine control and design features including, for example, an
engine equipped with variable compression ratio, an engine equipped
with variable valve timing, a variable or fixed exhaust gas
recirculation (EGR), a variable intake mixture temperature and a
variable fuel temperature.
[0038] The systems for controlling the efficient use of the engine
fuel can be implemented as a programmed general purpose computer in
accordance with exemplary embodiments of the invention. It will be
appreciated by those skilled in the art that the controller can be
implemented using a single special purpose integrated circuit, for
example, an application specific integrated circuit (ASIC), having
a main or central processor section for overall, system-level
control, and separate sections dedicated to performing various
different specific computations, functions and other processes
under control of the central processor section. The controller can
be a plurality of separate dedicated or programmable integrated or
other electronic circuits or devices, e.g., hardwired electronic or
logic circuits such as discrete element circuits, or programmable
logic devices (PLDs) or the like.
[0039] While the exemplary embodiments of the invention have been
described with reference to preferred aspects thereof, it is to be
understood that the invention is not limited to the preferred
aspects or constructions. To the contrary, the invention is
intended to cover various modifications and equivalent
arrangements. In addition, while exemplary aspects of the invention
are described, other combinations and configurations are also
within the spirit and scope of the invention.
* * * * *