U.S. patent application number 09/262921 was filed with the patent office on 2001-06-14 for fuel injection.
Invention is credited to YANG, JIALIN.
Application Number | 20010003280 09/262921 |
Document ID | / |
Family ID | 22999642 |
Filed Date | 2001-06-14 |
United States Patent
Application |
20010003280 |
Kind Code |
A1 |
YANG, JIALIN |
June 14, 2001 |
FUEL INJECTION
Abstract
A stratified charge is formed in an engine by injecting fuel at
an impingement surface adjacent an outlet of the injector. The
injected fuel thereby forms a cloud shallowly penetrating the
combustion chamber so as to float therein to reduce wall-wetting
and subsequent soot formation. A substantially flat top piston
urges the cloud upwardly during a compression stroke of the engine.
The cloud remains substantially unmixed with the inducted air,
thereby producing the stratified charge. The continued motion of
the piston causes the cloud to move toward the spark plug for
ignition.
Inventors: |
YANG, JIALIN; (CANTON,
MI) |
Correspondence
Address: |
LYON & ARTZ PLC
28333 TELEGRAPH ROAD
SOUTHFIELD
MI
48034
|
Family ID: |
22999642 |
Appl. No.: |
09/262921 |
Filed: |
March 5, 1999 |
Current U.S.
Class: |
123/295 |
Current CPC
Class: |
F02M 51/08 20190201;
F02B 17/005 20130101; F02M 69/045 20130101; F02B 2075/125 20130101;
Y02T 10/12 20130101; Y02T 10/123 20130101; F02M 69/044 20130101;
F02M 61/18 20130101; F02B 23/101 20130101 |
Class at
Publication: |
123/295 |
International
Class: |
F02B 017/00 |
Claims
1. A method of forming a combustible fuel mixture for a spark
ignition internal combustion engine, the engine having a cylinder
block with a plurality of cylinder bores formed therein, the
cylinder bore defining a longitudinal axis, a plurality of
substantially flat top pistons each reciprocally housed within a
cylinder bore, a cylinder head attached to the block and closing
top ends of the bores to form a plurality of combustion chambers,
an intake port formed in the cylinder head and communicating with
the combustion chamber via an intake valve for introducing air into
the combustion chamber, a fuel injector, defining an axis and
communicating with the combustion chamber, for supplying fuel into
the combustion chamber, and an ignition source communicating with
the combustion chamber for igniting fuel within the combustion
chamber, with said method comprising the steps of: injecting fuel
from the fuel injector having an outlet into the engine at a
predetermined velocity and forming said injected fuel with spray
jet having a predetermined initial cone angle, with said injected
fuel impinging on a surface adjacent the outlet of said injector
thereby forming a cloud shallowly penetrating the combustion
chamber so as to float therein to reduce wall wetting; urging said
cloud upwardly in said combustion chamber with said substantially
flat top piston during a compression stroke of the engine.
2. A method according to claim 1 wherein said predetermined
velocity is between about 60 m/s and about 100 m/s along the axis
of the fuel injector.
3. A method according to claim 1 wherein said predetermined initial
cone angle is between about 30.degree. and about 60.degree..
4. A method according to claim 1 wherein an amount of fuel
vaporized into said cloud relative to the amount of fuel injected
is greater than about 95%.
5. A method according to claim 1 wherein said mixture comprises a
stratified mixture and said cloud defines a relatively rich region
and the remainder of the volume of the combustion chamber defines a
lean region, with said fuel remaining substantially unmixed with
said inducted air, thereby producing said stratified charge and
said piston moves said cloud toward said ignition source.
6. A method according to claim 5 wherein said engine comprises a
direct injection engine.
7. A fuel injected, spark ignition internal combustion engine
comprising: a cylinder block; a cylinder bore formed in said
cylinder block, with said bore defining a longitudinal axis and
having a top end; a cylinder head attached to said block and
closing said top end of said bore to form a combustion chamber; an
intake port formed in said cylinder head and communicating with
said combustion chamber via an intake valve for inducting air into
said combustion chamber; a fuel injector, defining an axis, for
injecting fuel into said combustion chamber, said injector having
an outlet for injecting said fuel at a predetermined velocity and
formed into a cone having a predetermined initial cone angle; an
impingement surface provided adjacent said outlet of said injector,
with said injected fuel striking said impingement surface thereby
forming a fuel cloud for shallowly penetrating into said combustion
chamber so as to float therein to reduce wall wetting; and a
substantially flat top piston reciprocally housed within a said
bore.
8. An engine according to claim 7 wherein said fuel is formed into
a droplet size is between about 6 .mu.m and about 12 .mu.m after
striking said impingement surface.
9. An engine according to claim 8 wherein said predetermined
initial cone angle is between about 30.degree. and about
60.degree..
10. An engine according to claim 9 wherein said predetermined
velocity is between about 60 m/s and about 100 m/s along said axis
of said fuel injector.
11. An engine according to claim 7 wherein an amount of fuel
vaporized into said cloud relative to the amount of fuel injected
is greater than about 95%.
12. An engine according to claim 7 wherein said fuel remains
substantially unmixed with said inducted air, thereby producing a
stratified charge and wherein said cloud defines a relatively rich
region and the remainder of the volume of the combustion chamber
defines a lean region, with said substantially flat top piston
urging said cloud upwardly during a compression stroke of the
engine and an ignition source communicates with said combustion
chamber, with said cloud engulfing said ignition source so that
said fuel is ignitable by said ignition source.
13. An engine according to claim 12 further comprising an engine
controller, with said engine controller being responsive to a
plurality of engine operating parameters, with said controller
causing a switch between a stratified charge and a homogeneous
charge formed within the combustion chamber, with said switch
occurring at an engine load of greater than about 50% of full
engine load.
14. An engine according to claim 7, wherein said impingement
surface comprises a substantially spherical surface positioned
adjacent the outlet of said injector so substantially all of said
jet strikes said surface.
15. An engine according to claim 14, wherein said impingement
surface is positioned approximately 1.25 mm from said injector
outlet.
16. An engine according to claim 15, wherein said impingement
surface has a spherical diameter of approximately 3 mm.
17. An engine according to claim 16, wherein said impingement
surface has a recess formed thereunder.
18. An engine according to claim 17, wherein said engine comprises
a direct injection engine.
19. An engine according to claim 18, wherein said engine operates
with a stratified charge.
20. An engine according to claim 17, wherein said engine comprises
a port injection engine.
21. An engine according to claim 20, wherein said engine operates
with a substantially homogeneous charge.
22. A stratified charge, direct injection, spark ignition internal
combustion engine comprising: a cylinder block; a cylinder bore
formed in said cylinder block, with said bore defining a
longitudinal axis and having a top end; a cylinder head attached to
said block and closing said top end of said bore to form a
combustion chamber; an intake port formed in said cylinder head and
communicating with said combustion chamber via an intake valve for
inducting air into said combustion chamber; a fuel injector,
defining an axis, for injecting fuel directly into said combustion
chamber at a predetermined velocity and having a spray jet exiting
an outlet of the injector; an impingement surface positioned
adjacent said outlet of said injector, said impingement surface
having a size and positioned in close proximity to said outlet so
substantially all of said jet strikes said surface, with said
injected fuel thereby shallowly penetrating into said combustion
chamber so as to form a cloud and float therein to reduce wall
wetting; a substantially flat top piston reciprocally housed within
said bore, with said substantially flat top piston causing said
injected fuel to move upwardly during a compression stroke of the
engine, with said fuel remaining substantially unmixed with said
inducted air, thereby producing said stratified charge; and, an
ignition source communicating with said combustion chamber, with
said cloud engulfing said ignition source so that said fuel is
ignitable by said ignition source.
23. An engine according to claim 22, wherein said impingement
surface comprises a substantially spherical surface.
24. An engine according to claim 23, wherein said impingement
surface has a diameter of approximately 2.5 mm and is positioned
approximately 1.25 mm from said outlet.
25. An engine according to claim 24 wherein said impingement
surface is provided on said engine head.
26. An engine according to claim 24 wherein said impingement
surface is provided on said injector.
27. An engine according to claim 24, wherein said impingement
surface has a recess formed thereunder.
28. An engine according to claim 24 wherein said fuel is injected
at approximately 100 degrees after intake.
29. An engine according to claim 24 wherein an amount of fuel
vaporized into said cloud relative to the amount of fuel injected
is greater than about 95%.
30. An engine according to claim 24 further comprising an engine
controller, with said engine controller being responsive to a
plurality of engine operating parameters, with said controller
causing a switch between a stratified charge and a homogeneous
charge formed within said combustion chamber, with said switch
occurring at an engine load between about 60% and about 70% of full
engine load.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to fuel injection in an
internal combustion engine and more particularly to forming a cloud
of fuel in such engines.
BACKGROUND OF THE INVENTION
[0002] Direct injection engines are aimed at improving fuel economy
at low engine loads by providing a stratified charge in the
combustion chamber. A stratified charge engine is one in which the
combustion chamber contains stratified layers of different air/fuel
mixtures. The strata closest to the spark plug contains a mixture
slightly rich of stoichiometry, and subsequent strata contain
progressively leaner mixtures. The overall air/fuel mixture within
the combustion chamber is lean of stoichiometry, thereby improving
overall fuel economy at low loads. At high engine loads, typically
greater than 50% of full engine load, a homogeneous air-fuel
mixture is provided in the combustion chamber.
[0003] Conventional direct injection engines typically include a
piston having a depression in the top face thereof (typically
referred to as a bowl) and a swirl or tumble control valve located
in the intake port to produce a swirl or tumble of the air entering
the combustion chamber. As fuel is injected into the combustion
chamber, the fuel impinges against the bottom of the bowl and
cooperates with the motion of the air in the chamber to produce the
stratified charge, with the richest portion of the charge moving
toward the ignition source.
[0004] The inventors of the present invention have recognized
certain disadvantages with these prior art engines. For example,
because the fuel sprayed from the fuel injector is directed toward
the piston bowl, it is likely that a portion of the fuel will stick
to the piston surface causing an undesirable wall-wetting
condition. As the remainder of the fuel is burned, the flame
propagating toward the piston surface is unable to completely burn
the liquid fuel film on the piston surface. This results in
undesirable soot formation during combustion.
[0005] In addition, because the design of these engines relies on
the fuel impinging against the bowl and subsequently directed
toward the spark plug, fuel injection timing is of a major concern.
In direct injection engines, fuel injection is a function of time
whereas the motion of the piston is a function of crank angle. In
port injected engines, fuel entering the chamber is a function of
crank angle because the opening of the intake valve is a function
of crank angle. As a result, it is imperative to control the timing
of fuel injection in a direct injection engine so that the injected
fuel may impinge on the bowl at the proper time and the fuel cloud
may move toward the spark plug. In other words, if the fuel is
injected too early, the spray may miss the bowl entirely, thereby
not deflecting toward the spark plug. If the fuel is injected too
late, then excess wall-wetting may occur.
[0006] Further, the inventors of the present invention have found
that with bowl-in-piston engines, switching between a stratified
charge and a homogeneous charge occurs at part loads ranging
between 30% to 40% of full engine load. As the engine load
increases, more fuel is required. However, because of the physical
limitations of the bowl (i.e. the size of the bowl relative to the
size of the combustion chamber), the amount of fuel that can be
placed in the bowl and still attain a stratified charge is limited.
Otherwise, the potential for wall wetting and subsequent soot
formation may increase. As a result, above about 40% of full engine
load, fuel economy is compromised.
[0007] Other disadvantages with prior art engines results in a
heavier piston, increased engine height to accommodate the larger
piston, a larger combustion chamber surface to volume ratio, more
heat loss, and increased charge heating during the intake and
compression strokes, which increases the tendency for engine
knocking.
[0008] Furthermore, with port injection, the fuel impinges on the
valve and intake port. At cold startup, the valve and port may be
cool and the fuel will not vaporize as desired, causing high HC
emissions and soot. During transient conditions, valve and port
wetting by the fuel results in a longer response tome from the
change of fuel injection pulse width to the change in fuel that
enters the cylinder. This increases the difficulty in fuel metering
control, fuel consumption, and HC/CO emissions.
[0009] In copending application, Ser. No. 08/925,131, ('131
application) assigned to the assignee of the present invention, and
which is incorporated herein by reference in its entirety, a fuel
cloud is directly injected into a combustion chamber. The present
invention is directed, in part, at improving the formation of a
cloud of fuel in the combustion chamber.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to provide a direct
injection spark ignition engine which overcomes the disadvantages
of prior technology. This object is achieved, and disadvantages of
prior art approaches overcome, by providing a method of forming a
fuel cloud in the combustion chamber using an impingement target
immediately adjacent the fuel outlet of the fuel injector. The fuel
strikes the target at a high velocity and forms a cloud of fuel
thereabout. The fuel then remains suspended in the combustion
chamber creating a relatively rich strata near the spark plug.
[0011] An advantage of the present invention is that wall-wetting
on the piston surface is reduced.
[0012] Another, more specific, advantage of the present invention
is that a near complete combustion occurs with little or no soot
formation with low HC and NO.sub.x formation.
[0013] Yet another advantage of the present invention is that a
less complex engine is provided in that no bowl is required for the
piston.
[0014] Still another advantage of the present invention is that
regulated emissions may be reduced.
[0015] Another advantage of the present invention is that the
engine load range in which a stratified charge may be produced is
extended.
[0016] Other objects, features and advantages of the present
invention will be readily appreciated by the reader of this
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The invention will now be described, by way of example, with
reference to the accompanying drawings, in which:
[0018] FIGS. 1 and 2 are a diagrammatic cross-sectional
representations of a direct injection engine according to the
present invention;
[0019] FIG. 3 is a diagrammatic cross-sectional representations of
a port injection engine according to the present invention;
[0020] FIGS. 4-5 are diagrammatic cross-sectional representations
of a fuel injector according to the present invention; and,
[0021] FIG. 6 is a diagrammatic representations of alternative fuel
injector mounting according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] An internal combustion engine 10 according to the present
invention, as shown in FIGS. 1-3, includes a cylinder block 12,
having a cylinder bore 14 formed therein and a piston 16
reciprocally housed within the bore 14. The piston 16 has a
substantially flat top 18, i.e. without a substantial piston bowl
formed therein. A cylinder head 20 is attached to the block 12 and
encloses a top end 22 of the bore 14 to form a combustion chamber
24. The engine 10 is preferably a multi-valve engine having, for
example, two intake ports and two exhaust ports. For the sake of
clarity, only one intake port 26 is shown and is formed within the
cylinder head 20 and communicates with the combustion chamber 24
through an intake valve 28.
[0023] An intake port 26 provides intake air within the combustion
chamber 24. In a preferred embodiment, the intake port 26 comprises
a conventional intake port providing little or no swirl or tumble,
although deactivation of one of the intake valves may produce some
swirl motion. One skilled in the art appreciates that the intake
port may be modified in a known manner to provide tumble and/or
swirl motion as desired to promote flame propagation and
combustion. Furthermore, a particular combustion chamber may work
better with tumble and/or swirl motion to properly locate the cloud
80--near the spark plug 30 for ignition.
[0024] The engine 10 includes a spark plug 30 communicating with
the combustion chamber 24 for igniting an air/fuel mixture within
combustion chamber 24. The engine 10 further includes a fuel
injector 32 defining an axis 34 for injecting fuel directly into
the combustion chamber 24 in FIGS. 1-2 and into the intake port in
FIG. 3. In the example of FIG. 1, the injector 32 is generally
located along axis 36 of the cylinder 14. However, the injector 32
need not be coincident with the axis 36. In fact, the injector 32
may be mounted on the side of cylinder bore 14, typically referred
to as a side mounted injector, as shown in the example illustrated
in FIG. 2. Likewise, an injector 32 may be provided in an intake
port as illustrated in FIG. 3 for a port fuel injected engine.
[0025] As shown in FIG. 4, the injector 32 includes tip 36 having
an orifice 38 for injecting fuel from a fuel system (not shown) to
the combustion chamber 24. The injector 32 further includes an
impingement surface 70 provided adjacent the orifice 38. Preferably
the impingement surface comprises a convex surface as illustrated
in FIG. 4. In a further embodiment illustrated in FIG. 5, the
convex impingement surface 70' has a recess 72 formed thereunder,
forming a "mushroom-shaped" impingement surface 70'. The
embodiments of FIGS. 4 and 5 illustrate the impingement surface
provided on the injector 32 itself. One skilled in the art
appreciates the impingement surface 70 may be formed in the engine
itself, such as on the head (not shown), or provided in an insert
74 mounted to the engine, and preferably threadably engaged
thereto. The injector 32' is engaged with the insert 74, preferably
through a second threaded attachment.
[0026] The engine 10 further includes a controller 40 (see FIG. 1)
having a memory storage device 42. A plurality of sensors 44 sense
numerous engine operating parameters such as engine speed, engine
load, spark timing, EGR rate, fuel delivery rate, engine air charge
temperature, engine coolant temperature, intake manifold absolute
pressure, the operating position of the throttle, vehicle gear
selection, vehicle speed, intake manifold air mass flow rate,
accelerator position, and other parameters known to those skilled
in the art and suggested by this disclosure.
[0027] As described above, the impingement surface 70 is preferably
convex in cross section and preferably has a substantially
spherical shape. One skilled in the art appreciates that the shape
of the impingement surface may be altered to include substantially
flat or concave or conical, etc. surfaces and yet achieve some of
the beneficial effects described herein, but the inventor has found
the spherical shape, especially using the recess 74, provides the
most beneficial operation by minimizing wetting and maximizing fuel
droplet dispersion and achieve the desired fuel penetration.
[0028] The principle under which my invention works is as follows.
The fuel is injected from the injector tip 36 at high speed. The
impingement surface 70 is provided as close to the orifice 38 as
possible to maximize the velocity at which the fuel strikes the
surface 70. As one positions the surface further from the orifice
38, the fuel slows prior to striking the surface 70 due to the air
resistance met within the combustion chamber 24 and more fuel may
be inclined to wet the surface 70 at lower reflex velocities.
[0029] The inventor has found empirically that a commercially
available fuel injector 32 having a 45 degree coangle injecting
fuel at approximately 70 bar will properly strike a surface 70
positioned approximately 1.5 mm from the orifice 38. At this
distance, the fuel cone angle is such that almost all of the fuel
stream strikes the surface 70 and is deflected thereby.
Furthermore, the surface 70 is close to the injector, so the
velocity of the stream is not significantly reduced before striking
the surface 70. Preferably the fuel leaves the injector 32 at
approximately 60-100 m/s. Upon deflection, the fuel breaks into
small droplets, promoting fast vaporization. The velocity of the
deflected droplets is decreased from the injected velocity. The
fuel is deflected into a cloud 80, and the velocity of the fuel is
reduced. This promotes a cloud 80 of small fuel droplets and vapor.
If the surface 70 is positioned too close to the orifice 38, the
fuel will be deflected back toward the injector. If positioned too
far from the orifice 38, the fuel stream will not all strike the
surface 70 as described above and a desired cloud 80 will not be
formed, plus the velocity of the stream will be reduced prior to
impacting the surface 70 and not deflect as desired.
[0030] One skilled in the art appreciates that a Port Fuel
Injection (PFI) application may use a similar system, preferably
including an injector having a smaller injector coangle than a DI
application, and therefore the cone angle may be significantly
smaller than the 45 degrees described in the example above, perhaps
as small as 10 or 15 degrees, and, depending on the distance the
impingement surface is placed from the injector, the injector
coangle may be as wide as 40 degrees or more. Likewise, the
velocity of the fuel from the injector in a PFI application is
likely to be lower than the DI velocity, dependent again upon many
factors. Initial tests show that a PFI injector may operate with a
velocity range as low as about 20-40 m/s, and depending upon other
factors as described above, this range may be expanded.
[0031] One skilled in the art appreciates that a number of variable
affect the stream coming from the injector and therefore the
numbers described above are representative for a particular
embodiment. For example, if the pressure in the combustion chamber
is increased, the diameter of the stream may be reduced (this
effect is less as one is closer to the injector). Likewise, all
other things being equal, a lower injector angle will produce a
narrower stream. In this case, one skilled in the art appreciates
the surface 70 may be smaller or further positioned from the
orifice 38, depending on several variables, including those
described above.
[0032] An advantage of the present invention is that the fuel cloud
80 does not substantially strike the piston surface 18, if at all.
Thus, air is entrapped between the piston 16 and the cloud 80,
thereby forming a lean mixture above the piston. This enables lower
hydrocarbon (HC) and soot production from the combustion process.
Similarly, the cloud 80 is pushed upwardly by the piston 16 during
the compression stroke, and therefore a rich mixture is formed near
the spark plug 30, thereby enabling proper ignition and combustion.
And this stratified operation enables lean operation in some
instances. Furthermore, the injection may occur later in the cycle
because the lower penetration will enable proper fuel mixture at
the spark plug 30. This also promotes lower levels of NO.sub.x
production.
[0033] The present invention, when used in a DI application, does
not require the fuel to be directed toward the spark plug 30 with
the piston surface 18, and therefore the location of the piston
relative to the plug 30 is not critical to position fuel near the
plug 30. This is contrary to the applications where the fuel is
injected onto the top of the piston and reflected by the shape of a
bowl formed in the piston, as utilized for example in U.S. Pat. No.
5,553,588. The present invention therefore enables one to inject
fuel later in the compression stroke, as it is not necessary to
position the piston in the proper position to reflect the fuel, and
the present invention may still also may eliminate piston wetting
at such late injection. Furthermore, at high load, a direct
injection engine is preferably run at approximately homogeneous
charge. In such a case, fuel is injected after about 100 crank
angle degrees after top dead center of the intake stroke. A nearly
homogeneous charge may thereby be formed in the combustion chamber,
but the cloud will result in a leaner mixture near the bottom of
the combustion chamber. This reduces hydrocarbon loading at the
piston/linear crevices and thereby improves emissions.
[0034] Similarly, in a Port Fuel Injection system (PFI), emissions
are improved. In the PFI engine, the charge is substantially
homogeneous under most operating conditions. The impingement
improves the fuel penetration and valve wetting is reduced or
eliminated. Therefore, the engine may employ open-valve injection
to improve cold start and transient operation.
[0035] According to the present invention, fuel injector 32 injects
fuel into the combustion chamber 24 at a predetermined velocity
along axis 34 of injector 32 and at a predetermined initial cone
angle. In one embodiment, fuel is injected during the compression
stroke at about 60.degree. before top dead center. The fuel strikes
the impingement surface 70 and forms a cloud 80. Consequently, the
injected fuel shallowly penetrates into combustion chamber 24 so as
to float therein to reduce wall-wetting. As piston 16 progressively
compresses the air within combustion chamber 24 during the
compression stroke, the cloud is urged toward the top 22 of the
combustion chamber by the action of the substantially flat top
piston 16. The fuel thereby remains substantially unmixed with air
inducted through intake port 26, thereby producing the stratified
charge in combustion chamber 24. Further, the piston motion causes
the cloud 80 to engulf the spark plug 30 so that the fuel may be
ignited.
[0036] In a preferred embodiment, the droplet size for an
undeflected fuel stream, as measured by the Sauter Mean Diameter
method, is between about 15 .mu.m and about 25 .mu.m approximately
45 mm away from the tip of the injector 32 with the surface 70
removed. The injection velocity of the fuel entering into the
combustion chamber is between about 60 m/s and about 100 m/s, as
measured along axis 34 of injector 32. Also, the initial cone angle
.theta. of fuel cone is between about 30.degree. and about
60.degree., and preferably 45.degree.. After deflection, the fuel
droplet size is between approximately about 6 .mu.m and about 12
.mu.m.
[0037] The effects of having such a shallowly penetrating fuel
injected from fuel injector 34 is clearly shown in the graphs of
FIGS. 3-5 of the '131 application. In the '131 application, the
benefits of vaporization and formation of a stratified charge are
discussed in detail and therefore not presented here.
[0038] According to the present invention, controller 40 controls a
switch point for switching between a stratified charge produced in
combustion chamber 24, as described above, and a homogeneous
charge. Those skilled in the art will recognize in view of this
disclosure that changing between a stratified charge and a
homogeneous charge may be accomplished by changing injection timing
from the compression stroke to the intake stroke, for example. The
switch point occurs at a point greater than about 50% of full
engine load, and, more desirably, at a point between about 60% and
about 70% of full engine load. This is due to the fact that a
stratified charge may be produced in combustion chamber 24, as
described above, with a relatively large amount of fuel being
delivered therein without the potential for wall wetting and
subsequent soot formation because the charge is not constrained by
a bowl formed in piston surface 18 of a limited volume, but rather
is constrained by the entire volume of combustion chamber 24.
[0039] While the best mode for carrying out the invention has been
described in detail, those skilled in the art to which this
invention relates will recognize various alternative designs and
embodiments, including those mentioned above, in practicing the
invention that has been defined by the following claims.
* * * * *