Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENT ON
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This invention relates generally to gaseous fuel
internal combustion engines. More particularly, this
invention concerns a novel stratified charge combustion
apparatus and method for use in such engines.
Conventional liquid fuel internal combustion engines
burn a homogeneous mixture of air and fuel supplied Jo the
combustion chamber from a mixing device, such as a car-
barter. To achieve ignition of this homogeneous mixture,
the air-to-fuel ratio must be maintained within a rota-
lively narrow range, which prevents optimum combustion
of the air/fuel mixture over the full range of operating
levels. For example, if the engine is operating at a low
power output, the air intake must be throttled to reduce
the amount of air taken into the combustion chamber,
thereby maintaining the air to-fuel ratio within the
ignitable range. Throttling the air intake, however,
20 results in increased friction horsepower and increased
pumping losses, thereby reducing engine efficiency.
In contrast, by concentrating fuel in the vicinity of
the ignition source, stuffed charge internal combustion
25 engines maintain the air-to-fuel ratio near the ignition
source within the ignitable range. Combustion is thus
possible in a stratified charge combustion system even
though the overall artful ratio may run well outside
the ignitable limits. The resulting oxygen-rich environ-
30 mint of the combustion chamber produces more complete
r combustion of the fuel. The stratified charge liquid fuel
combustion engine thus can run more efficiently and also
exhaust less emissions than conventional liquid fuel
internal combustion engines.
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Additionally, because the air-to-fuel ratio is high
in those portions of the combustion chamber remote from
¦ the ignition source, stratified charge liquid fuel come
bastion systems alleviate the problem of detonation. This
permits the utilization of higher compression ratios
compared to compression ratios of standard homogeneous
mixture internal combustion engines. Higher compression
ratios, in turn, yield lower fuel consumption, and thus
will lower engine operating costs and conserve energy.
The advantages of stratified charge internal combs-
lion have long been known and practiced in liquid fuel
internal combustion engines. Different methods have been
used to create a fuel rich mixture in the vicinity of the
ignition source. For example, United States Patent No.
3,318,292 to Hide discloses various embodiments of a
liquid fuel stratification awry system. Particularly,
- several of the described embodiments illustrate a fuel
injector thaw directs the liquid fuel against a wall of
the combustion chamber where it is vaporized and subset
quaintly transported to the ignition source by the turbo-
- lent motion of combustion air in the combustion chamber.
In another embodiment, a liquid fuel is injected against
at least one surface of an air intake port, intake passage,
or intake valve where it is vaporized and carried into the
combustion chamber by the incoming air
Another method of creating fuel charge stratification
j is shown in US. Patent No 3,911,873 to Dave. This
1 30 method involves a variable internal combustion engine
valve operating system, one embodiment of which illustrates
a shrouded valve or directing the flow of a corroborated
fuel/air mixture toward a spark plug A further example
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is shown in US. Patent No. 3,154,059 to Witzky et at.,
which discloses an injection system in which liquid fuel
I is injected near the periphery of swirling air in the
_ combustion chamber to create a rich fuel/air mixture near
the ignition source.
US. Patent NO. 3j809,039 to Alquist also directed to
stratified charge liquid fuel internal combustion engines,
discloses a park ignition system in which a rich fuel/air
mixture is passed into a precombustion chamber where it is
spark ignited. The ignited rich fuel/air mixture then .
Jo induces ignition of a lean fuel/air mixture in the main
combustion chamber.
In present commercial gaseous fuel internal cowboys-
lion engines, the gaseous fuel is introduced into the
combustion chamber in one of two ways. First, the combs-
lion air and gaseous fuel may enter the combustion chamber
together through either intake valves or intake ports.
Second, the combustion air may be admitted separately
J through either intake valves or intake ports. The gaseous
fuel is then separately injected into the combustion
chamber by a gaseous fuel injection YalveO Typically,
the valve is non-directional; that is, the gaseous fuel is
injected 360~ around the valve, creating a roughly cone
shaped dispersion of the gaseous fuel in the combustion
chamber. occasionally, a directional fuel injection valve
is used to inject the gaseous fuel at less than 1803
around the valve.
on
Dual chamfer combustion systems, illustrated by the
Fairbanks Morse MYOPIA. Model 8-1/8 Spark Ignited Energy
Cell Gaseous Fuel Engine, have been used in gaseous fuel
internal combustion engines A rich homogeneous fuel/air
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mixture is spark ignited in a precombustion chamber. This
ignited rich fuel/air mixture then induces ignition of a
1 lean fuel/air mixture in the main combustion chamber.
This type of combustion system is sometimes referred to as
5 a stratified charge system.
In all these commercially available gaseous fuel
engines, however, the fuel injection system is designed to
achieve a homogeneous mixture of the gaseous fuel and the
10 combustion air in the main combustion chamber at the time
of ignition. Even when a separate gaseous fuel injection
valve is used r location of valves in the combustion
chamber, the directional orientation of the valves, and
the angle of the valves is designed to direct the gaseous
15 fuel toward the center of the combustion chamber. Thus,
present gaseous fuel internal combustion engines possess
many of the disadvantages of homogeneous charge liquid
fuel internal combustion engines, including inefficient
fuel con5umptionc which results in higher fuel costs and
20 produces greater amounts of air pollutants.
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SUMMARY OF THE INVENTION
By means of the present invention there is provided
25 a combustion system for use in gaseous fuel internal
combustion engines that is substantially free of the
7 disadvantages of the prior art The stratified charge
combustion system of the present invention includes
i a hollow cylinder having an inside surface and two sun-
30 faces opposed to each other and in spaced relationship
along the longitudinal axis of the cylinder. At least one
of these opposed surfaces is the top surface of a piston
that is positioned in the cylinder to move reciprocatingly
along the longitudinal axis of the cylinder. The two
35 opposed surfaces and the inside surface of the cylinder
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define a combustion chamber. In communication with the
combustion chamber is an ignition source and a gaseous fuel
injection valve assembly which is in spaced relationship from
the ignition source. A portion of the surfaces defining the
combustion chamber extend between the valve assembly and the
ignition source. The valve assembly has a directing means
adjacent to the combustion chamber for inducing an injected
gaseous fuel to aerodynamically cling to and follow the contour
of the portion of the surfaces, which define the combustion
chamber extending between the valve assembly and the ignition
source, as the gaseous fuel flows to the ignition source.
The present invention thus provides for the first time
a combustion system which produces a controlled stratified
charge in a single combustion chamber a gaseous fuel internal
combustion engine. Therefore, the twin advantages of low fuel
consumption and low pollutant emissions which have been
obtained utilizing a stratified charge combustion system in
liquid fuel internal combustion engines will now be available
in gaseous fuel internal combustion engines.
In one embodiment of the invention, one of the opposed
surfaces is the top surface of a piston, and the other opposed
surface is the generally concave inside surface of a cylinder
head. Both the ignition source and the valve assembly are
mounted in the cylinder head. When the valve assembly is opened,
the directing means preferably induces the gaseous fuel to
strike a curved transitional surface, which is integral with
the inside surface of the cylinder head and adjacent the valve
assembly, at such an angle and speed that the gaseous fuel
aerodynamically clings to the inside surface of the cylinder
head as the gaseous fuel flows to the ignition source. The
directing means is preferably a shrouded seat.
Because the gaseous fuel is induced to follow the inside
surface of the cylinder head, it is only minimally affected
by air turbulence within the combustion chamber. More
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specifically, the portion of gaseous fuel flow nearest to the
inside surface of the cylinder head will provide a much richer
fuel/air ratio and the portion of the gaseous fuel flow which
is further from that surface will result in a much leaner fuel/
air ratio. Thus, the limited diffusion of the gaseous fuel
stream as it flows toward the ignition source, combined with
the limited natural mixing of the combustion air and the gaseous
fuel in the cylinder, produces a gradient of mixture strength
which is very rich near the ignition source and very lean in
those portions of the combustion chamber where there is no
gaseous fuel flow.
In another aspect of the invention, the directing means
induces the gaseous fuel to impinge on the inside surface of
the cylinder head at such an angle that following initial
impingement the gaseous fuel flows along the inside surface
of the cylinder head to the ignition source. In a further
aspect of the invention, the directing means induces the gaseous
fuel to flow in a substantially direct line across the combustion
chamber to the ignition source.
A method aspect of this invention relates to the manner
of injecting a gaseous fuel into the combustion chamber of
a gaseous fuel internal combustion engine. This is accomplished
by injecting gaseous fuel into the combustion chamber and then
inducing the gaseous fuel to aerodynamically cling to and follow
the contour of the portion of surfaces, which define the come
bastion chamber and extend between the valve assembly and the
ignition source, as the gaseous fuel flows to the ignition
source.
Some of the more important features of the present
invention have thus been summarized rather broadly in
order that the detailed description thereof that follows
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may be better understood, and in order that the contribu-
lion to the art may be better appreciated. There are, of
i course, additional features of the invention that will be
; described hereinafter and which will also form the subject
of the claims appended hereto.
BRIEF Description OF THE DRAWINGS
Figure 1 is a vertical cross-sectional view of one
embodiment of the gaseous fuel stratified charge combs-
lion system of the present invention.
Figure 2 is a detailed cutaway view of one embody-
mint of the gaseous fuel injection valve assembly of the
present invention.
Figure 3 is a cross-sectional view of the valve
assembly of Figure 2, taken along line 3--3.
Figure 4 is a top view of the valve guide of the
valve assembly of Figure 2, taken along line 4 4.
Figure 5 is a horizontal cross-~ectional view ox the
combustion chamber of the embodiment of Figure 1, taken
along line 5-5.
Figure 6 it a detailed cutaway view of an alternative
! gaseous fuel injection valve assembly of the present
invention having a shrouded teat.
! 30
- Figure 7 is a detailed cutaway view of an alternative
gaseous fuel injection valve assembly of the present
invention having a capped seat.
- 9 -
Figure 8 it a fragmentary cross-sectional view of an
alternative embodiment of the gaseous fuel stratified
3 charge combustion system of the present invention in which
the gaseous fuel it induced to impinge on the inside sun-
5 face of the cylinder head, appearing with Figures 1-4 & 9.
Figure 9 is a fragmentary cross-sectional view of an
alternative embodiment of the gaseous fuel stratified
charge combustion system of the present invention in which
the gaseous fuel is induced to flow directly across the
lo combustion chamber to the ignition source, appearing with
Figures l-4 and I
Figure 10 is a vertical cross-sectional view of an
alternative embodiment of the gaseous fuel stratified
_ charge combustion system of the present invention having
a flat cylinder head.
Figure 11 is a horizontal cross-sectional view of
the alternative embodiment of Figure 10, taken along line
1 1 -I 1 .
Figure 12 is a vertical Ross sectional view of an
alternative embodiment of the gaseous fuel stratified
charge combustion system of the present invention having
two opposed pistons.
Figure 13 is a horizontal cross-sectional view of
the alternative embodiment of Figure 12, taken along line
3 25 13-13.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
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throughout the following description, similar refer-
once numerals refer to similar emanate in all figures of
the drawing.
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As used throughout this application, the term "gaseous
fuel is intended to include all elements, compounds, and
mixtures thereof that exist substantially completely in
the gaseous state under the conditions existing at the
injection valve at the time of fuel injection Such
elements and compounds would include, but no be limited
to, hydrogen, carbon monoxide, methane ethanes propane,
butane, and heavier hydrocarbon fuels.
Referring to Figure 1, there is shown one embodiment
of a gaseous fuel stratified charge combustion system 10
of the present invention incorporated into a two cycle
internal combustion engine. the stratified charge combs-
lion system 10 comprises a cylinder 12 having an inside
surface 13, a piston 14 reciprocatingly positioned in
cylinder 72 and having a top surface 16, and a cylinder
head 18 enclosing the end of cylinder 12 and having a
concave inside surface 20. Inside surface 13 of cylinder
12~ top surface 16 of piston 14, and concave inside sun-
face 20 of cylinder head 18 define a combustion chamber
22. An ignition source 24 is centrally mounted in Solon-
don head 18 and communicates with combustion chamber 22.
As shown, ignition source 24 is a spark plug, although
either a pilot injection of liquid fuel oil ignited by
the heat of compression or a precombustion chamber which
en utilizes its own fuel supply and ignition source could
also be used. A fuel injection valve assembly 26 is
mounted in cylinder head 18 adjacent cylinder 12 and is
in communication with combustion chamber 22.
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Referring now to the detail sectional view of figure
2, one embodiment of gaseous fuel injection valve assembly
26 includes a valve cage 28 adapted for mounting in
cylinder head 18 by inserting a cylindrical. lower portion
30 ox valve cage 28 into a cylindrical bore 32 that
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extends through cylinder head 18 and into combustion
chamber 22. A curved and flared transitional surface 34
,' communicates between bore 32 and inside surface 20 of
cylinder head 18 to provide a smooth transition prom bore
.: 5 32 into combustion chamber 22. Anchoring means 35, such
as the nut and bolt shown in Figure 2, Sirius valve cage
28 to cylinder head 18.
A fuel intake passage 36 which extends through valve
cage 28, has an entrance port 38 at its upstream end
adapted to receive a gaseous fuel manifold OWE At the
downstream end of intake passage 36 is an inlet port 42
which opens into combustion chamber 22 and through
which gaseous fuel slow into the combustion chamber is
controlled by a valve 44. Inlet port 42 his a straight
cylindrical wall portion 46 of circular cross-section that
terminates at an annular valve seat 48 which is oonven-
tonally beveled at a suitable angle such as 4$) to the
axis of inlet port 42.
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Valve 44 includes a valve head 50 which is convent
tonally generally frustoconical in shape. Valve head 50
has a valve face 52 on one side which faces combustion
chamber 22 and a valve back 54 on its opposite wide. An
annular valve seating portion 56 is formed on valve
~2C~ 54 to cooperate with valve seat 48 whereby valve head
50 is adapted to engage tightly valve sea 48. Extending
from and integral with valve back 54 is an elongated valve
stem 5B which is concentric with the axis of valve head 50
and reciprocatingly positioned in a valve guide bore 60.
Valve guide bore 60, which extends through valve cage 28
to inlet port 42, is coaxial with the axis of inlet port
42. An upper portion 62 of valve stem 58 protrudes beyond
valve guide bore 60. Projecting from valve back 54 is
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a valve shroud 64 concentric to the axis of valve 44 and
extending around a predetermined circumferential extent of
valve head 50. -
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:¦ 5 As more clearly shown in Figure 3, valve shroud 64
extends about 180~ around valve head 50. Referring once
again to Figure 2, when valve 44 is in an open position
shroud 64; valve stem 58, valve back 54, valve seat I
and transition surface 34 cooperate to form a fuel flow
lo passage 56 from inlet port 42 into combustion chamber 22.
As best seen in Figures 2 and I gaseous fuel inject
lion valve assembly 26 includes a valve guide 68 having a
circular portion 70 and an arm portion 72 extending from
.. 15 circular portion 70. A cord truncated circular hole 74 in
circular portion 70 engages a guide portion 76 of upper
portion 62 of valve stem 58, also of truncated circular
cross-sectiont to align valve shroud 64 circumferential
away from ignition source 24. A threaded portion 78 of
valve stem 58 extends above valve guide 6B and has a
diameter smaller than that of guide portion 76 in order to
pass freely through truncated circular hole 74 of valve
owe
25, Still referring to Figures 2 and 4, a valve guide
retainer 80 is an angled plate having a horizontal leg 82
j which is abutted against and secured to valve cage 28.
1 Extending upward from horizontal leg 82 is a vertical
leg 84 which is slotted at its upper end to form a yoke
8b. Yoke 86 horizontally retain arm portion 72 of valve
guide 68 and permits limited vertical movement of valve
guide 68. Wright it, the bottom of yoke By defines the isle
open position so valve 44. A seen in Figure 2, a coil
spring 88 bear against circular portion 70 of valve guide
I and against horizontal leg 82 of guide retainer 80 to
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bias valve 44 into the closed position (not shown). A nut
90 is threaded onto threaded portion 78 of valve stem So
to retain coil spring 88 and valve glide 68~
Referring now to Figures 1 and I operative of this
embodiment is shown at the time of fuel injection in a two
cycle gaseous fuel internal combustion engine. Gaseous
fuel injection is timed to begin near the closing of he
exhaust ports trot shown) by piston 14 on the compression
stroke. Injection of gaseous fuel is timed to end before
compression pressure in combustion chamber 22 exceeds the
gaseous fuel supply pressure First; valve 44 is opened
to permit a gaseous fuel 92 to enter combustion chamber
22. As gaseous fuel 92 passes through fuel passage 66, it
_ 15 trikes transitional surface 34 at an angle and speed such
that gaseous Eel go aerodynamically clings to the contour
of transitional surface 34 and inside surface 20 of
cylinder head 18 as it flows to ignition Bounce 24. A
shown in Figure 5, limited diffusion of gaseous fuel
92 occurs as it flows along inside surface 20. This
limited diffusion along with the limited natural mixing
of gaseous fuel 92 with air in the combustion chamber,
produces a gradient ox fuel/air mixture strength. That
is, the portion of gaseous fuel flow nearest to the inside
surface 20 produces a richer fuel/air ratio, and the
portion of the gaseous fuel flow remote from the inside
, surface 20 yields a leaner fuel/air ratio. During the
! remaining portion of the compression stroke and before
ignition occurs, stratification of the fuel/air mixture
Jo 30 will continue, producing in the area of ignition source 24
a pocket of rich fuel/air mixture suitable for easy, felt-
able and consistent ignition. At points in combustion
amber distant from ignition source 24, the fuel/air
mixture is Weaner.
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inures 6 and 7 depict alternative directional valve
designs that can be used in place of the shrouded valve
! shown in the embodiment of Figures 1, 2 and JO In
Figure 6, the directing means is a seat shroud 94 project-
; 5 in below valve seat 48 a distance greater than the maxim
mum open position of valve 44. As shown, seat shroud 94
extends about 180 around the circumference of valve head
50. A capped seat configuration is illustrated in Figure
I in which a cap 96 encloses valve 44. An orifice 98 in
cap 96 opens toward transitional surface 34 to induce
proper flow of gaseous fuel OWE
Referring now to Figures 8 and 9, shown are alterna-
live gaseous fuel flow streams that may be produced in
_ 15 directing gaseous fuel 92 to flow toward ignition source
24. Although a capped seat is shown, it can be apprise-
axed that either a shrouded seat, as shown in Figure 6, or
a shrouded valve, as shown in Figure 2, could also be used
simply by locating valve seat 48 at or inside the contour
) pa of inside surface 20 of cylinder head 18.
In Figure it gaseous fuel 92 is directed just
inside and generally tangential to inside surface 20 of
cylinder head 18. Thus, a transitional surface 34 is not
required in this embodiment gaseous fuel 92 then flows
along the curvature of inside surface 20 until it reaches
ignition o'er 24.
Again, in Figure 9, transitional surface 34 is
not needed. Instead, gaseous fuel 9X is induced to flow
directly across combustion chamber 22 to ignition Bounce
24 without relying on inside surface 20 of cylinder head
18 to direct it there.
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Figures 10 and 11 illustrate an alternative to the
combustion chamber embodiment shown in Figure 1. This
design utilizes a cylinder head 18 having a substantially
flat inside surface 20 with four valves 100, 102, 104 and
06 and a piston 14 having a Mexican hat-shaped top sun-
face 16 or a flat top surface 16 (not shown). If valves
100~ 102, 104 and 106 are exhaust valves with the system
utilizing air intake ports (not shown) in cylinder 12 the
system is a two cycle combustion system. If, on the other
hand, valves 100 and 102 are air intake valves end valves
104 and 106 are exhaust valves, the system is a four cycle
combustion system. Gaseous fuel injection it timed to
begin on the compression stroke near the closing of intake
valves 100, 102 on the four cycle system and near the
closing of exhaust valves 1001 102r 104 and 106 on the two
cycle system. Ignition source 24 is centrally mounted on
cylinder head 18, and injection valve assembly 26 is also
mounted in cylinder head 18 adjacent the cylinder 12.
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Each of the three flow streams depicted in Figures 1,
8 and 9 can else be used in this design of the combustion
J chamber. That is, gaseous fuel 92 may be induced to
aerodynamically cling to inside surface 20 of cylinder
head 18 as gaseous fuel 92 flows to ignition source 24;
gaseous fuel 92 may be induced to impinge on inside
surfs of cylinder head 18 at such an angle that,
following initial impingement, gaseous fuel 92 flows along
I; inside surface 20 of cylinder head to to ignition source
24; or guises fuel 92 may be induced to slow in a sub Stan-
i 30 tidally direct line across combustion chamber 22 to ignition
source 24. Further, the directing means may be zither a
shrouded valve, a shrouded seat, or a capped seat.
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Figures 12 and 13 illustrate another embodiment of
the gaseous fuel stratified charge combustion system of
. the present invention having a pair of opposed piston 14
operating on a two strove cycle. Although piston 14
as shown have Mexican hat top surfaces 16, a flat surface
may also be used. Valve assembly 26 and ignition source
24 are mounted in cylinder 12 an appropriate distance
apart, here shown as approximately 90. A redundant
ignition source 108 may be present in this embodiment if
an existing gaseous fuel internal combustion engine is
retrofitted with a valve assembly 26 according to the
present invention. Figure 13 illustrates a flow stream in
which gaseous fuel 92 is induced to aerodynamically cling
to inside surface 13 of cylinder 12 as gaseous fuel 92
flows to the ignition source 24. However the flow
streams illustrated in Figures 8 and 9 are also both
applicable to this embodiment. Likewise although the
directing means illustrated in Figures 12 and 13 is a
shrouded seat, a shrouded valve or a capped seat could
also be used
.
The foregoing description has been directed to
particular embodiments of the invention in accordance with
the requirements of the patent statutes for the purposes
of illustration and explanation. It will be apparent,
however, to those skilled in this art what many modifica-
lions and changes in the apparatus and procedures set
forth will be possible without departing from the scope
and spirit of the invention. It is intended that the
following claims be interpreted to embrace all such
modification and changes.
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