U.S. patent number 3,809,039 [Application Number 05/291,612] was granted by the patent office on 1974-05-07 for stratified charge spark ignition internal combustion engine with exhaust recycle.
This patent grant is currently assigned to Phillips Petroleum Company. Invention is credited to Henry E. Alquist.
United States Patent |
3,809,039 |
Alquist |
May 7, 1974 |
STRATIFIED CHARGE SPARK IGNITION INTERNAL COMBUSTION ENGINE WITH
EXHAUST RECYCLE
Abstract
A spark ignition system and a method for operating same by
passing a first fuel-air mixture into a precombustion chamber of
the engine and a second leaner fuel-air mixture into a primary
combustion chamber, igniting the first mixture for igniting the
second mixture, and controllably mixing about 5 to about 20 percent
of the exhaust gas resulting from the combustion of the fuel
mixtures with the second fuel-air mixture during operation of the
engine at greater than about 75 percent maximum power output with
the amount of exhaust gas being mixed with the second fuel-air
mixture varying directly with the power output of the engine.
Inventors: |
Alquist; Henry E.
(Bartlesville, OK) |
Assignee: |
Phillips Petroleum Company
(Bartlesville, OK)
|
Family
ID: |
23121027 |
Appl.
No.: |
05/291,612 |
Filed: |
September 25, 1972 |
Current U.S.
Class: |
123/274;
123/568.29; 123/DIG.4 |
Current CPC
Class: |
F02D
21/08 (20130101); Y10S 123/04 (20130101) |
Current International
Class: |
F02D
21/00 (20060101); F02D 21/08 (20060101); F02m
025/06 () |
Field of
Search: |
;123/119A,75B,32ST,127,DIG.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Burns; Wendell E.
Claims
1. A method for operating a spark ignition engine having a
precombustion chamber in communication with a primary combustion
zone and means for igniting a fuel-air mixture in the precombustion
chamber, comprising:
controllably passing a first fuel-air mixture into the
precombustion chamber;
controllably passing a second fuel-air mixture into the primary
combustion zone, said second fuel-air mixture being a leaner fuel
mixture relative to the first mixture;
igniting the first mixture in the precombustion zone for igniting
the second mixture in the primary combustion zone; and
controllably mixing about 5 to about 20 percent of the exhaust gas
resulting from the combustion of the first and second fuel-air
mixtures with the second fuel-air mixture during operation of the
engine at greater than about 75 percent maximum power output of the
engine, said amount of exhaust gas being mixed with the second
fuel-air mixture varying directly
2. A method, as set forth in claim 1, wherein the first fuel-air
mixture is in the range of about a 500 to about a 1000 percent
stoichiometric fuel.
3. A method, as set forth in claim 1, wherein the second fuel-air
mixture
4. A method, as set forth in claim 3, wherein the first fuel-air
mixture is in the range of about a 500 to about a 1,000 percent
stoichiometric fuel.
5. In a spark ignition system having a primary combustion zone,
mixing means for controllably mixing a primary fuel-air mixture,
and means for passing said primary fuel-air mixture into the
primary combustion zone, the improvement comprising:
a precombustion chamber being in fluid communication with the
primary combustion zone;
mixing means for controllably mixing another fuel-air mixture being
a richer fuel mixture relative to said primary fuel-air
mixture;
means for passing said other fuel-air mixture into the
precombustion chamber;
means for igniting the fuel-air mixture in the precombustion
chamber for igniting the primary fuel-air mixture in the primary
combustion zone;
exhaust means for directing the combustion gas resulting from
combustion of the fuel-air mixture from the engine;
measuring means for measuring a variable representative of the
power output of the engine and delivering a signal in response
thereto;
a conduit connected in fluid communication with the exhaust means
and the primary combustion chamber;
control means for passing about 5 to about 20 percent of the
exhaust gas resulting from the combustion of the first and second
fuel-air mixtures into the primary combustion chamber during
operation of the engine at greater than about 75 percent maximum
power output of the engine, said control means comprising a control
valve positioned in the conduit and connected to the measuring
means, said valve being in a closed position in response to a
signal from the measuring means representative of the output of the
engine being less than about 75 percent maximum power output and
said valve being controllably opened in response to a signal from
the measuring means representative of the output of the engine
being greater than about 75 percent maximum power output with the
opening of said valve
6. An apparatus, as set forth in claim 5, wherein the variable
measured by the measuring means is the manifold pressure of the
primary combustion
7. An apparatus, as set forth in claim 5, wherein the mixing means
for the primary fuel-air mixture is a carburetor adapted to provide
a fuel-air
8. An apparatus, as set forth in claim 5, wherein the mixing means
for the other fuel-air mixture is a carburetor adapted to provide a
fuel-air mixture in the range of about a 500 to about a 1,000
percent
9. An apparatus, as set forth in claim 8, wherein the mixing means
for the primary fuel-air mixture is a carburet0r adapted to provide
a fuel-air mixture less than about an 80 percent stoichiometric
fuel.
Description
It is desirable to provide a spark ignition system which will
operate with low pollution emissions while maintaining high power
output and efficiency.
This invention therefore resides in a spark ignition system and a
method of operating same by passing a first fuel-air mixture into a
precombustion chamber of the engine and a second leaner fuel-air
mixture into a primary combusiton chamber, igniting the first
mixture for igniting the second mixture, and controllably mixing
about 5 to about 20 percent of the exhaust gas resulting from the
combustion of the fuel mixtures with the second fuel-air mixture
during operation of the engine at greater than about 75 percent
maximum power output with the amount of exhaust gas being mixed
with the second fuel-air mixture varying directly with the power
output of the engine.
Other aspects, objects, and advantages of the present invention
will become apparent from a study of the disclosure, the appended
claims, and the drawings.
The drawings are diagrammatic views of the apparatus and data of
tests performed on the apparatus. FIG. 1 shows the apparatus of
this invention, FIG. 2 shows the combustion chambers, FIG. 2a shows
element 6 in more detail and FIGS. 3-8 show data of tests performed
on the engine.
Referring to FIGS. 1 and 2, a spark ignition engine 2 has a primary
combustion zone 4 and a precombustion zone 6 that are in fluid
communication one with the other. For simplicity, reference will be
made to the primary and precombustion zones in the singular. It
should be understood, however, that the engine can have a plurality
of primary combustion zones, preferably with each primary zone
having a precombustion zone with the associated elements as set
forth with reference to the singular zones.
Each of the combustion zones 4, 6 has a separate carburetor 8, 10
connected in fluid communication therewith which in turn is
connected to an air supply, a fuel supply, and a throttle for
controllably discharging fuel-air mixtures from the carburetors 8,
10 into their respective combustion zones 4, 6.
The carburetor 8 of the primary combustion zone or chamber 4 is
constructed to receive and mix fuel and air therein and discharge a
fuel-air mixture into the primary combustion zone 4 that is a
relatively lean fuel-air mixture, being less than about an 80
percent stoichiometric fuel.
The carburetor 10 of the precombustion zone or chamber 6 is
constructed to receive and mix fuel and air therein and discharge a
fuel-air mixture into the precombustion chamber 4 that is a richer
mixture relative to the other fuel mixture, preferably a fuel-air
mixture in the range of about a 500 to about a 1,000 percent
stoichiometric fuel.
A spark ignition system, generally referred to by numeral 12, is
associated with the precombustion chamber 6 for igniting the
fuel-air mixture therein, which in turn ignites the fuel-air
mixture in the primary combustion zone 4 for operating the engine
2.
An exhaust conduit 14 (FIG. 1) is connected to the exhaust outlet
of the primary combustion chamber 4 for directing the exhaust gas
resulting from combustion of the first and second fuel-air mixtures
from the engine 2.
An exhaust gas recirculating conduit 16 is connected in fluid
communication with the primary combustion zone 4 and the exhaust
conduit 14.
A measuring means, for example a pressure controller 18, is
associated with the engine 2 for measuring a variable
representative of the power output of the engine 2 and delivering a
signal representative thereof. For example, the measuring means can
measure the intake manifold pressure of the primary combustion zone
4 as shown in FIG. 1.
A control means, such as a control valve 20 for example, is
positioned in the exhaust gas recirculating conduit 16 and is
connected to the measuring means 18 for receiving a signal
therefrom and opening and closing the valve in response to said
signal. The valve 20 is constructed to be in the closed position in
response to a signal representative of the output of the engine
being less than about 75 percent maximum power output of the
engine. The valve 20 is open and controllably positioned in
response to a signal from the measuring means representative of the
output of the engine 2 being greater than about 75 percent maximum
power output with the opening of said valve 20 varying directly
with the power output of the engine 2 and passing exhaust gas in
the range of about 5 to about 20 percent of the total exhaust gas
passing through conduit 14.
FIGS. 3-8 show the results of tests on an engine of this
invention.
The precombustion chamber used in these tests had the following
characteristics:
Shape: cylindrical
Orifice: one-eighth in. square edge
Volume: 0.83 cu. in.
Intake valve location: rear of chamber
Spark gap location: rear of chamber
Length/Diameter: 3.80
The precombustion chamber was operated with a supply of fuel-air
mixture such that 88 percent of the precombustion chamber volume
was filled with mixture at the beginning of the compression stroke.
Fuel was present in the mixture supplied the precombustion chamber
in an amount 5 times that required for a stoichiometric mixture,
i.e., 500 percent stoichiometric fuel.
The engine used was a CFR, single cylinder unit similar in basic
configuration to the standard knock-test engine except for two
additional combustion chamber access holes. A sketch of the
arrangement of the precombustion chamber and the main CFR engine
combustion chamber is shown in FIG. 2. The fuel was a conventional
premium grade gasoline having a research octane number of 99 and
containing 2.5 ml TEL per gallon.
In lieu of an acceptable technique for the direct measurement of
noise, the effect of exhaust gas recirculation (EGR) to reduce
noise was documented in terms of the peak value of the first
time-derivative of cylinder pressure. The filtered output of the
standard D-1, magnetostrictive knock-test pickup furnished the
dP/dT signal. FIG. 3 presents peak dP/dT values on an arbitrary,
but linear, scale as functions of stoichiometry. Results of the
conventional engine, the precombustion chambered engine, and the
precombustion chambered engine with 8 percent EGR are included.
Objectionable combustion noise did not occur below a value of 6 on
the scale in FIG. 3. Thus, the data in that Figure showed that 8
percent EGR in the precombustion chambered engine extended
noise-limited operation to 103 percent stoichiometric fuel from 89
percent with no EGR. This is judged to be a significant expansion
of the useful operation range of the precombustion chambered
engine.
FIG. 4 presents exhaust NO.sub.x concentrations (as NO) plotted
against the percentage stoichiometric fuel. At all stoichiometries
richer than 70 percent stoichiometric fuel, 8 percent EGR reduced
NO.sub.x emission. At stoichiometrics leaner than 70 percent, the
presence of recirculated exhaust gas appeared to increase NO.sub.x.
Although the reasons for this increase are unknown, it is
unimportant since NO.sub.x values with the prechambered engine were
quite low at the stoichiometries where the increase occurred.
Hence, there would be no incentive for EGR application in this
stoichiometry range. Eight Percent EGR reduced NO.sub.x from the
precombustion chambered engine about 54 percent at 90 percent
stoichiometric fuel at constant power.
FIG. 5 shows that 8 percent EGR in the precombustion chambered
engine produced a 4 to 7 percent loss of power at constant
throttle. The prechambered engine without EGR resulted in a 5 to 9
percent decrease in power as compared to the conventional engine.
The total power decrease attributed to the simultaneous application
of the precombustion chambered combustion process and the 8 percent
EGR was about 12 percent. Although not desirable, this power loss
is certainly acceptable.
FIG. 6 shows that 8 percent EGR had only a mirror effect on exhaust
hydrocarbon concentrations. From 100 percent to 70 percent
stoichiometric fuel, which is the range where EGR is applied to the
precombustion chambered engine, 8 percent EGR increased hydrocarbon
emissions no more than 14 percent and as little as 6 percent.
FIG. 7 shows that the influence of 8 percent EGR on the carbon
monoxide emissions from a precombustion chambered engine is
negligible.
FIG. 8 compares the effectiveness of about the same amount of
exhaust gas recirculation (EGR) on NO formation from a conventional
engine and a prechambered engine. This figure shows that applying
EGR to the prechambered engine has about the same benefit on NO (at
a given stoichiometric mixture) as the application of EGR to the
conventional engine. However, with the conventional engine, the
application of EGR enrichens the lean misfire limit from about 74
percent stoichiometric fuel to about 89 percent stoichiometric fuel
(see FIG. 8) which limits the usefulness of EGR. With the
prechambered engine, the application of EGR has no deleterious
effect on lean misfire limit. In addition, EGR has the other
important benefit of substantially reducing excessive rates of
pressure rise (leading to noise) of the prechambered engine.
This invention therefore provides a spark ignition engine which
will operate with low pollution emissions while maintaining high
power output and efficiency.
Other modifications and alterations of this invention will become
apparent to those skilled in the art from the foregoing discussion
and accompanying drawings, and it should be understood that this
invention is not to be unduly limited thereto.
* * * * *