U.S. patent application number 11/892418 was filed with the patent office on 2009-02-26 for spark-ignited gas engine.
Invention is credited to Hans Mathews, James J. McCoy, JR., Peter Steinruck.
Application Number | 20090050084 11/892418 |
Document ID | / |
Family ID | 40380992 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090050084 |
Kind Code |
A1 |
Mathews; Hans ; et
al. |
February 26, 2009 |
Spark-ignited gas engine
Abstract
Conventional spark-ignited gas engines with a mechanically
controlled fuel feed valve have several disadvantages in terms of
operation, expensive control, irregular combustion or unstable and
unreliable operation, which in turn can lead to operational and
mechanical problems. In order to eliminate these disadvantages it
is suggested, according to the invention, that a controlled valve
is installed in the fuel line upstream of the fuel feed valve so
that in the fuel line between fuel feed valve and controlled valve
a defined intermediate volume is created and gaseous fuel is fed
via the controlled valve into the intermediate volume.
Inventors: |
Mathews; Hans; (Magnolia,
TX) ; McCoy, JR.; James J.; (Spring, TX) ;
Steinruck; Peter; (Hallstatt, AT) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
FRANKLIN SQUARE, THIRD FLOOR WEST, 1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Family ID: |
40380992 |
Appl. No.: |
11/892418 |
Filed: |
August 22, 2007 |
Current U.S.
Class: |
123/90.15 |
Current CPC
Class: |
F02D 41/0027 20130101;
Y02T 10/32 20130101; F02D 41/008 20130101; F02M 21/0251 20130101;
F02D 19/024 20130101; Y02T 10/30 20130101; F02M 21/0239 20130101;
F02M 21/0269 20130101 |
Class at
Publication: |
123/90.15 |
International
Class: |
F01L 9/04 20060101
F01L009/04 |
Claims
1. A spark-ignited gas engine with a number of cylinders (z),
wherein on each cylinder (z) a mechanical fuel feed valve (11) for
the direct feeding of gaseous fuel into the cylinder (Z) and a fuel
line (2) opening into the cylinder (Z) are provided and the fuel
line (2) can be closed by the mechanical fuel feed valve (11) in
the direction of the cylinder (Z), wherein the fuel line (2)
upstream of the fuel feed valve (11) includes a controlled valve
(10), so that in the fuel line (2) between fuel feed valve (11) and
controlled valve (10) a defined intermediate volume (12) is created
and in via the controlled valve (10) gaseous fuel can be fed to the
intermediate volume (12).
2. The spark-ignited gas engine according to claim 1, wherein the
controlled valve (10) is a solenoid valve.
3. The spark-ignited gas engine according to claim 1, including a
control unit (20) for controlling the controlled valves (10) is
connected to each controlled valve (10) via a control output
(S).
4. A method for controlling a spark-ignited gas engine with a
number of cylinders (Z), wherein on each cylinder (Z) a mechanical
fuel feed valve (11) for the direct feeding of gaseous fuel into
the cylinder (Z) and a fuel line (2) opening into the cylinder (Z)
are provided and the fuel line (2) is closed by the mechanical fuel
feed valve (11) in the direction of the cylinder (Z), including
positioning a controlled valve in the fuel line (2) upstream of the
fuel feed valve (11) so that in the fuel line (2) between fuel feed
valve (11) and controlled valve (10) a defined intermediate volume
(12) is created and the amount of fuel fed to the cylinder (Z) is
set in that a defined amount of fuel is supplied to the
intermediate volume (12) through the controlled valve (10).
5. The method according to claim 4, including opening the
controlled valve (10) after the fuel feed valve (11) is opened and
closing the controlled valve before the fuel feed valve (11) is
closed.
6. The method according to claim 4, including opening the
controlled valve (10) before the fuel feed valve (11) is
opened.
7. The method according to claim 6, including closing the
controlled valve (10) before the fuel feed valve (11) is
opened.
8. The method according to claim 4, comprising feeding different
amounts of fuel into different cylinders (Z).
9. The method for converting a gas engine with a number of
cylinders (Z), wherein on each cylinder (Z) a mechanical fuel feed
valve (11) for the direct feeding of gaseous fuel into the cylinder
(Z) and a fuel line (2) opening into the cylinder (Z) are provided
which can be closed by the mechanical fuel feed valve (11) in the
direction of the cylinder (Z), including inserting a controlled
valve (10) in the fuel line (2) upstream of the fuel feed valve
(11) so that a defined intermediate volume is created between fuel
feed valve (11) and controlled valve (10).
10. The method according to claim 9, wherein a fuel chamber is
arranged between cylinder (Z) and fuel line (2).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a spark-ignited gas engine
with a number of cylinders, wherein on each cylinder a mechanical
fuel feed valve for direct feeding of gaseous fuel into the
cylinder and a fuel line opening into the cylinder are provided and
the fuel line can be closed by the mechanical fuel feed valve in
the direction of the cylinder. The invention also relates to a
method for controlling such a gas engine and a method for
converting a gas engine to such a gas engine.
[0003] 2. The Prior Art
[0004] In spark-ignited gas engines, e.g., large-volume gas engines
operated with natural gas in natural gas extraction and transport
or in the chemical industry, the gaseous fuel (natural gas,
liquefied gas, hydrogen, etc.) is metered at low pressure directly
into the cylinders when a mechanical fuel feed valve is opened.
When the fuel feed valve is open, gaseous fuel flows through the
mechanical fuel feed valve, then through the fuel line and into the
cylinder. Because of the low pressure the gas feed takes place at
low cylinder pressure, e.g., during the initial compression phase.
The fuel feed into the cylinder is discontinued once the fuel feed
valve is closed again. The mechanical fuel feed valve is generally
controlled by a camshaft and therefore opens for a predetermined
crank angle range or a period of time as a function of the speed.
Since this determines the opening time, the mount of fuel amount
fed to the cylinder depends largely on the prevailing pressure in
the fuel line. In order to control such a gas engine, for example
when the load varies, the pressure in the fuel line must
consequently be controlled. However, such control is expensive and
under certain conditions causes irregular combustion and unstable
and unreliable operation of the gas engine, which in turn can lead
to operational and mechanical problems. Another problem of such
mechanical control of a two-stroke gas engine is that unburnt fuel
from the cylinder can flow into the intake manifold and/or exhaust
pipe when the speed of the gas engine is reduced, which can lead to
dangerous explosions in the intake manifold or exhaust pipe, high
hydrocarbon emissions and higher fuel consumption. In addition,
mixture is consequently forced back into the gas system t, leading
to poor metering accuracy and thus misfiring.
[0005] In order to avoid these problems, individually controlled
gas valves, e.g., hydraulically and/or electromagnetically
controlled valves which inject a predeterminable gas amount into
the cylinder during the intake stroke, can be employed instead of
the mechanical fuel feed valves. However, in order to be able to
feed sufficient fuel into the cylinder despite the very short
injection times and the small available opening cross sections,
fuel at high pressure is required in these systems, which increases
expenditures. Such a gas valve results is disclosed in AT 413 136
B, for example.
[0006] It is likewise possible in four-stroke engines to feed the
gaseous fuel directly into the intake line in which the mixing of
air and gaseous fuel then takes place. However, ignitable mixture
is then present in the intake manifold, which can lead to
undesirable backfiring.
[0007] A spontaneously igniting gas engine is disclosed in from JP
08-028 268 A, where through a controlled valve a defined gas amount
is introduced into an auxiliary combustion chamber. At the end of
the compression phase a mechanical valve is opened so that hot
compressed air is able to flow into the auxiliary combustion
chamber through which the gas mixture present in the auxiliary
combustion chamber is ignited. The ignited gas mixture then expands
into the cylinder and brings about the power stroke. However,
nothing with regard to metering of gaseous fuel directly into the
cylinder of a spark-ignited gas engine may be deduced from JP
08-028 268 A.
[0008] It is an object of the invention to provide a spark-ignited
gas engine and a method for controlling such a gas engine which
allows accurate, flexible metering of gaseous fuel into the
cylinder and hence accurate, flexible control of the gas
engine.
SUMMARY OF THE INVENTION
[0009] This object is achieved for the gas engine according to the
invention in that a controlled valve is arranged in the fuel line
upstream of the fuel feed valve so that in the fuel line between
the fuel feed valve and the controlled valve a defined intermediate
volume is created and gaseous fuel can be fed via the controlled
valve into the intermediate volume. This object is achieved for the
method according to the invention in that a controlled valve is
arranged in the fuel line upstream of the fuel feed valve so that a
defined intermediate volume is created in the fuel line between the
fuel feed valve and controlled valve, and in that the amount of
fuel fed into the cylinder is set by feeding a defined amount of
fuel into the intermediate volume through the controlled valve.
With the invention it is possible to admit a defined amount of
gaseous fuel into each individual cylinder of the gas engine, thus
allowing accurate, flexible control of the gas engine. In addition,
the contribution of the individual cylinders to the total output of
the gas engine can be easily adjusted. The invention enables
gaseous fuel to be fed at a constant pressure to the cylinder for a
certain time (or crank angle), thus enabling accurate setting of
the amount of fuel for each cylinder to achieve uniform combustion
and stable operation of the gas engine. Moreover, no fuel or less
fuel can be supplied to one cylinder or a plurality of cylinders by
the individual and independent feeding of each cylinder, which,
particularly in the partial load range, allows stable operation of
the engine which is optimized in terms of pollutant emissions.
[0010] The controlled valve is designed particularly advantageously
as a solenoid valve to allow simple, accurate control of the amount
of fuel fed.
[0011] Particularly advantageously a certain amount of gaseous fuel
is initially pre-stored in the intermediate volume by the
controlled valve in that the controlled valve upstream of the fuel
feed valve opens and closes before the fuel feed valve opens. When
the fuel feed valve opens, a clearly defined amount of fuel (volume
of the intermediate volume) is thus fed into the cylinder. Because
of this, the influence of the cylinder pressure on the feeding of
the fuel into the cylinder is largely eliminated. Moreover, the
influence of the control and the size of the mechanical valve is
also largely eliminated. In another embodiment of the invention,
however, it is also possible to keep the controlled valve open only
during the opening time of the fuel feed valve or to open the
controlled valve upstream of the fuel feed valve but to close it
only during the opening time of the fuel feed valve.
[0012] A further object of the invention lies in a simple method of
converting an existing gas engine with a mechanically controlled
fuel feed valve to a gas engine that can be flexibly, accurately
and easily controlled. This object is achieved in that a controlled
valve is inserted in the fuel line upstream of the fuel feed valve
on the cylinder so that a defined intermediate volume is created
between the fuel feed valve and the controlled valve.
[0013] The invention is described in the following by means of the
diagrammatic, non-limiting embodiments shown in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 shows a representation of a gas engine according to
the invention with a number of cylinders, and
[0015] FIG. 2 shows a detailed view of one of the cylinders of the
gas engine.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] FIG. 1 shows a spark-ignited gas engine 1, e.g., a
large-volume natural gas engine for the compression of natural gas
during natural gas transport or of process gases in the chemical
industry, which drives a load 3, e.g., a pump, a compressor, or a
generator. The gas engine 1 has, in the known manner, a number of
cylinders Z.sub.1 . . . Z.sub.n in which a respective piston 13
(see FIG. 2) is moved by the combustion of a gaseous fuel. Here,
the gas mixture in the cylinder Z is ignited by a spark plug 19 at
the end of the compression stroke. Each piston 13 is connected in
the known manner by a connecting rod to a crankshaft, not shown
here, via which the generated torque is transmitted to the load 3.
Here, the gas engine 1 can be designed as a two or four-stroke
engine. The fundamental design of such a spark-ignited gas engine
is sufficiently known, and not discussed further here.
[0017] In FIG. 2 shows by way of example a cylinder Z of the
spark-ignited two-stroke gas engine 1. The cylinder Z has an inlet
port into which an air feed line 17 opens, forcing air into the
cylinder Z. An exhaust port which leads into an exhaust pipe 16 is
likewise provided on the cylinder Z. In the upper region 18 of the
cylinder Z is arranged a mechanical fuel feed valve 11 which is
connected to the fuel line 2, opens into the cylinder Z and via
which the fuel can be fed to the cylinder Z. To this end, the fuel
feed valve 11 is controlled in the known manner by a camshaft 14
and by pushrods and rocker arms 15. The opening of the fuel feed
valve 11 consequently takes place as a function of the speed of the
gas engine 1 and for a given crank angle range. Here, the gaseous
fuel is supplied with low pressure at low cylinder pressure, e.g.,
at the start of the compression phase. To this end, each cylinder Z
is connected to a fuel line 2 through which the gaseous fuel is fed
to the gas engine 1.
[0018] In the flow direction of the gaseous fuel upstream of the
fuel feed valve 11 a controlled valve 10, e.g., a solenoid valve,
is arranged in the fuel line 2 according to the invention, into
which the fuel line 2 opens. Thus, a defined intermediate volume
12, which is able to accommodate a defined amount of fuel, is
created between fuel feed valve 11 and controlled valve 10. Such an
intermediate volume 12 can also obviously be created or enlarged by
providing a separate or additional fuel chamber between fuel feed
valve 11 and controlled valve 10. When the fuel feed valve 11 is
opened, e.g., at the start of the compression phase, the defined
amount of fuel present in the intermediate volume 12 is fed to the
cylinder Z.
[0019] Here, the feeding of gaseous fuel into the cylinder Z can be
controlled in different ways:
1) Fuel feed valve and controlled valve are open simultaneously
[0020] To this end the fuel feed valve 11 opens before the
controlled valve 10, which is again closed before the fuel feed
valve 10. However, the maximum amount of gaseous fuel that can be
supplied is determined only by the size and the opening time of the
controlled valve.
2) Fuel feed valve and controlled valve are partially open at the
same time
[0021] The controlled valve 10 in this case opens for a defined
period before the fuel feed valve 11 in order to pre-store a
defined amount of fuel in the intermediate volume 12 before the
fuel feed valve 11 opens. The controlled valve 10 can be closed
after or simultaneously with the fuel feed valve 11. Here, a
defined amount of fuel can be stored in the intermediate volume 12
before the fuel feed valve 11 opens.
3) Fuel feed valve and controlled valves open in a staggered
manner
[0022] The controlled valve 10 opens when the fuel feed valve 11 is
closed in order to pre-store a defined amount of fuel in the
intermediate volume 12. Before the fuel feed valve 11 is opened by
the cam control, the controlled valve 10 is closed. The two valves
thus operate in a staggered manner relative to each other. Thus, a
precisely defined amount of fuel can be fed to the cylinder Z.
[0023] In order to suitably control the controlled valve 10, a
control unit 20 can be provided which has a control input C via
which a control objective can be set, e.g., a certain speed, a
certain output or a certain torque. The control unit 20 has a
separate control output S.sub.1 . . . S.sub.n, for each cylinder Z
or for each controlled valve 10, via which the appropriate control
signals are transmitted to the controlled valves 10, e.g.,
indicating when the valve opens and closes and which opening cross
section is exposed (e.g., the stroke in the case of a solenoid
valve). To this end the control unit 20 can have additional inputs
such as for instance an input for the current speed n or the
current torque T, crank angle signal, pressure in the fuel line PG,
etc. Appropriate sensors can be arranged on the gas engine 1 for
this purpose.
[0024] Although the invention is described above taking the example
of a 2-stroke spark-ignited gas engine, the invention is obviously
also applicable to 4-stroke engines.
[0025] An existing spark-ignited gas engine 1 with a mechanical
fuel feed valve 11 can also be converted with little effort. For
this purpose, it is merely required for a controlled valve 10 to be
installed on each cylinder Z between the fuel line 2 and the fuel
feed valve 11. To do so, the fuel line 2 is removed, the controlled
valve 10 arranged upstream of the fuel feed valve 11 and the fuel
line 2 connected to the controlled valve 10. If required, a
separate or additional fuel chamber for creating or enlarging the
intermediate volume 12 can be arranged in the flow direction
upstream of the cylinder Z to create a larger intermediate volume
12.
* * * * *