U.S. patent application number 13/320412 was filed with the patent office on 2012-03-22 for method for operating an engine arrangement.
This patent application is currently assigned to RENAULT TRUCKS. Invention is credited to Nicolas Auffret, Romain Le Forestier.
Application Number | 20120067311 13/320412 |
Document ID | / |
Family ID | 41582031 |
Filed Date | 2012-03-22 |
United States Patent
Application |
20120067311 |
Kind Code |
A1 |
Auffret; Nicolas ; et
al. |
March 22, 2012 |
METHOD FOR OPERATING AN ENGINE ARRANGEMENT
Abstract
A method is provided for operating an internal combustion engine
having at least one cylinder, said engine operating according to a
four stokes cycle. The engine includes at least one controlled
intake port to control communication of the combustion chamber with
an intake line. The intake port is controlled to achieve a main
open phase mainly during the intake stroke. The intake port is
controlled to achieve an auxiliary open phase during the power
stroke in view of heating the engine at cold start.
Inventors: |
Auffret; Nicolas;
(Compertrix, FR) ; Le Forestier; Romain; (Lyon,
FR) |
Assignee: |
RENAULT TRUCKS
Saint Priest
FR
|
Family ID: |
41582031 |
Appl. No.: |
13/320412 |
Filed: |
June 2, 2009 |
PCT Filed: |
June 2, 2009 |
PCT NO: |
PCT/IB2009/006331 |
371 Date: |
November 14, 2011 |
Current U.S.
Class: |
123/90.15 ;
123/90.1 |
Current CPC
Class: |
Y02T 10/18 20130101;
F02M 26/01 20160201; F02D 2041/001 20130101; F02D 13/0273 20130101;
F02D 41/064 20130101; F02D 13/0223 20130101; F02B 37/00 20130101;
F02M 26/23 20160201; F02D 41/006 20130101; Y02T 10/12 20130101;
Y02T 10/40 20130101; F02D 41/0245 20130101; F02D 2013/0292
20130101; F02M 26/05 20160201; F02D 41/0002 20130101; Y02T 10/42
20130101 |
Class at
Publication: |
123/90.15 ;
123/90.1 |
International
Class: |
F01L 1/34 20060101
F01L001/34; F01L 1/00 20060101 F01L001/00 |
Claims
1. Method for operating an internal combustion engine having at
least one cylinder in which a piston connected to a crankshaft is
displaced between a top dead center position and a bottom dead
center position, thereby defining in the cylinder a variable volume
combustion chamber, the engine operating according to a four stokes
cycle including an intake stroke, a compression stroke, a power
stroke, and an exhaust stroke, wherein the engine comprises at
least one controlled intake port and at least one controlled
exhaust port to control communication of the combustion chamber
respectively with an intake line and with an exhaust line,
comprising controlling the intake port to achieve a main open phase
mainly during the intake stroke, controlling the exhaust port to
achieve a main open phase mainly during the exhaust stroke, and
controlling the intake port to achieve an auxiliary open phase
during the power stroke.
2. Method according to claim 1, wherein the auxiliary open phase
starts and ends during the power stroke.
3. Method according to claim 1, wherein the auxiliary open phase
starts. between 30 and 70 degrees of crankshaft revolution after
the top dead center position initiating the power stroke.
4. Method according to claim 1, wherein the auxiliary open phase
ends between 50 and 120 degrees of crankshaft revolution after the
top dead center position initiating the power stroke.
5. Method according to claim 1, wherein the auxiliary open phase
lasts between 15 and 50 degrees of crankshaft revolution.
6. Method according to claim 1, wherein the engine is a compression
ignition engine.
7. Method according to claim 1, wherein the intake port is
controlled through an intake valve
8. Method according to claim 1, wherein the intake valve is
controlled through a variable valve control system.
9. Method according to claim 1, wherein the routine of controlling
the intake port to achieve an auxiliary open phase during the power
stroke is performed in view of heating up the engine
arrangement.
10. Method according to claim 1, wherein the routine of controlling
the intake port to achieve an auxiliary open phase during the power
stroke is performed in view of heating the engine at cold
start.
11. Method according to claim 1, wherein the routine of controlling
the intake port to achieve an auxiliary open phase during the power
stroke is performed in view of heating up an exhaust
after-treatment system.
12. Method according to claim 1, wherein the routine of controlling
the intake port to achieve an auxiliary open phase during the power
stroke is performed at low engine loads.
13. Method according to claim 1, wherein the engine is a
multi-cylinder engine, in that the intake line comprise an intake
manifold having at least one distinct intake duct per cylinder so
that, during the routine of controlling the intake port to achieve
an auxiliary open phase during the power stroke for one cylinder,
post combustion gases are expelled through the intake port into the
corresponding intake duct of the cylinder.
Description
BACKGROUND AND SUMMARY
[0001] The invention relates to the field of methods for operating
an engine arrangement comprising a four stroke internal combustion
engine.
[0002] Four stroke internal combustion engines (ICEs) are well
known. In a reciprocating piston design, they have at least one
cylinder or several cylinders in each cylinder, a piston, which is
connected to a crankshaft, is displaced between a top dead center
position and a bottom dead center position, thereby defining in the
cylinder a variable volume combustion chamber. When such an engine
is operating according to a four strokes cycle, the four strokes
are usually theoretically defined as the periods of times between
two immediately consecutive dead center positions of the piston.
These strokes are the intake stroke, the compression stroke, the
power stroke, and the exhaust stroke. Such engines also comprise at
least one controlled intake port and at least one controlled
exhaust port to control communication of the combustion chamber
respectively with an intake line and with an exhaust line of the
engine arrangement. The opening and closing of the intake and
exhaust ports are usually performed through a corresponding poppet
valve. The intake port is controlled to achieve a main open phase
mainly during the intake stroke and the exhaust port is controlled
to achieve a main open phase mainly during the exhaust stroke. It
is of course well known that these main intake and exhaust opening
phases may start before or after the theoretical beginning and/or
end before or after the theoretical end of the corresponding
stroke.
[0003] It is also known that either the intake port or the exhaust
port can be controlled to achieve auxiliary opening phases to
modify the basic operation of the engine. For example, engine
braking can be enhanced by providing that the exhaust port is
opened at the end of the compression stroke. Also, it is known to
control a brief opening of the intake port, during the exhaust
stroke, or at least an early opening of the intake port at the end
of the exhaust stroke, to achieve so-called internal exhaust gas
recirculation.
[0004] Many ways of optimizing four strokes internal combustion
engines have been suggested already to enhance their performance in
view of often theoretically opposing requisites, and in particular
in view of minimizing consumption of fuel and production of harmful
emissions. One area of interest for engine arrangement designers is
the temperature management of the engine. Indeed, the engine cannot
always operate at its optimum temperature. One critical aspect is
the operation of the engine at start, before it has reached its
optimal temperature. It is then desirable to attain as quickly as
possible that optimal temperature. Another critical aspect has also
appeared more recently with the presence in the engine arrangement
of various exhaust after-treatment systems such as three-way
catalysts, particle filters or selective catalytic reduction
systems. Such systems often require that the exhaust gases passing
through them are comprised within a well defined temperature range,
either for their optimum functioning or, in the case of particulate
filters, for their regeneration. In such cases, it is sometimes
critical to enhance the temperature of the exhaust gases.
[0005] Another way to optimize the functioning of four stroke ICEs
is to achieve exhaust gas recirculation (EGR). Depending on how and
when EGR is performed, various results can be achieved, but a very
frequent reason to use of EGR, especially in Diesel engines, is to
lower the temperature of the combustion process in order to limit
the production of nitrogen oxides (NOx).
[0006] Document U.S. Pat. No. 6,347,619 discloses a way to achieve
EGR in a wide variety of engine operating conditions. The aim of
the system disclosed in this document is to capture exhaust gases
at a relatively high pressure. The system disclosed provides EGR in
a turbocharged diesel engine by adding a separate EGR manifold and
a secondary exhaust valve for each combustion chamber that permits
flow of exhaust gases from the combustion chamber to the EGR
manifold. The secondary exhaust valve is opened during the
expansion stroke of the engine cycle, after the combustion process
has been completed, while the pressure in the combustion chamber is
still greater than the pressure in the intake manifold. Therefore,
this system requires an additional manifold, an additional set of
ports and an additional system for controlling the additional
ports, and would therefore be quite costly.
[0007] It is desirable to provide a new method of operating a four
stroke ICE arrangement giving the possibility, at a minimal cost,
to ensure an enhanced thermal management of the engine and of the
exhaust gases.
[0008] The invention, according to an aspect thereof, therefore
provides for a method for operating an engine arrangement
comprising a four strokes internal combustion engine, characterized
in that said method includes the routine of controlling the intake
port to achieve an auxiliary open phase during the power
stroke.
DESCRIPTION OF FIGURES
[0009] FIG. 1 is a schematic view of the main components of an
engine arrangement which can be operated with the method according
to the invention.
[0010] FIG. 2 is a schematic diagram showing the control of the
intake port in an exemplary method of operating an engine
arrangement according to the invention, and the corresponding mass
flow rate through the intake port.
[0011] FIG. 3 is a schematic diagram showing the difference in
temperature in the cylinder which results from the use of the
method according to the invention.
DETAILED DESCRIPTION
[0012] On FIG. 1 is shown an engine arrangement 10 which comprises
a reciprocating piston internal combustion engine 12. Engine 12
comprises at least one cylinder 14, and, in the example shown,
comprises in fact six cylinders in an in-line configuration. Each
cylinder comprises a piston (not represented) which is connected to
a rotating crankshaft (not represented) of the engine through a
connecting rod (not represented). Following the rotation of the
crankshaft, the piston slides within the cylinder 14 between a top
dead center position and bottom dead center position, thereby
defining in the cylinder a variable volume combustion chamber. The
engine 12 is operated according to a four strokes cycle. The four
strokes are usually theoretically defined as the periods of times
between two immediately consecutive dead center positions of the
piston. These strokes are the intake stroke, the compression
stroke, the power stroke, and the exhaust stroke.
[0013] Each cylinder 14 is equipped with at least one intake port
16 and at least one exhaust port 18. As in many modern engines, the
engine on FIG. 1 has two intake ports 16 and two exhaust ports 18
per cylinder 14. Each port 16, 18 is controlled to permit or
inhibit fluid communication of the combustion chamber with an
intake line 20 or with an exhaust line 22 of the engine arrangement
10. Conventionally each port can be controlled by a poppet valve,
or any other suitable device. As will be seen hereunder, the.
engine is equipped with means for controlling the ports opening
phases according to the engine operating cycle. Such control means
can comprise a camshaft which mechanically controls poppet valves,
but such means can alternatively comprise camless means such as
electric-magnetic or electro-hydraulic valve actuators. In any
case, the control means are designed so that the intake port is
controlled to achieve at least a main open phase, mainly during the
intake stroke, and so that the exhaust port is controlled to
achieve at least a main open phase, mainly during the exhaust
stroke.
[0014] In the case of a multi-cylinder engine, the intake line is
preferably equipped with an intake manifold 21 through which it is
connected to each of the intake ports 16. The intake manifold 21
has preferably separate intake ducts for each individual intake
port 16, or at least preferably an individual intake duct 25 for
each cylinder. Similarly, the exhaust line is preferably equipped
with an exhaust manifold 23 having individual exhaust ducts for
each exhaust port or at least for each cylinder.
[0015] In the example shown, the engine 12 is a turbocharged engine
which comprises a turbo compressor 24 having its turbine 26 located
on the exhaust line 22 and its compressor 28 located on the intake
line 20. Also, the engine arrangement may be equipped, as
represented on FIG. 1, with an exhaust gas recirculation system
comprising for example an EGR conduit 30 having its inlet connected
to the exhaust line 22 upstream of the turbine 26 and its outlets
connected to the intake line 20 downstream of the compressor 28,
and an EGR valve 32 which controls the flow of exhaust gases which
can be circulated through the conduit 30 from the exhaust line to
the intake line. The EGR system can comprise a cooling system to
remove heat from the gases circulating in the conduit 30.
[0016] The engine 12 is for example a compression ignition engine,
known as a Diesel engine, but the invention could also be carried
out with a spark ignited engine. Also, the engine 12 may be of the
direct injection type, where fuel is injected directly in the
cylinder. In such a case, only air is admitted through the intake
line into the cylinders, but the invention could also be carried
out with an engine of the indirect injection type where the
injection is performed for example in the intake line or in a
pre-combustion chamber:
[0017] On FIG. 2 is shown a graph where it is represented how at
least one intake port of the engine is controlled in a method
according to the invention. On FIG. 2 can be seen curves VL
representing the intake port control, such as the valve lift, and
MFR representing the mass flow rate through the intake port,
expressed as a function of or the crank rotation angle, where the
top dead center position of the piston initiating the power stroke
is given the value 0. As can be seen on the diagram, the intake
port is controlled to achieve a main open phase which occurs mainly
during the intake stroke, said stroke occurring between 360 to 540
degrees of crankshaft revolution. In a Diesel direct injection
engine, this main open phase permits a certain quantity of gas
mixture to be admitted in the combustion chamber from the intake
line. This gas mixture is in most cases mainly composed of fresh
air, but as will be seen hereunder, it may also comprise
re-circulated exhaust gases. It can be seen that, during the main
open phase of the intake port, the curb representing the mass flow
rate of gases going through the intake port is on the positive
side, which signals indeed that the gases flow from the intake line
to the combustion chamber.
[0018] According to the invention, the method additionally includes
the routine of controlling the intake port to achieve an auxiliary
open phase during the power stroke, said stroke occurring between 0
to 180 degrees of crankshaft revolution. Preferably the auxiliary
open phase is controlled to start after the end of the combustion
process. In most engine operating conditions, at least for a diesel
direct injection engine, the auxiliary open phase can therefore
start between 30 and 70 degrees of crankshaft revolution after the
top dead center position initiating the power stroke. In the
example shown, it starts at approximately 50 degrees of crankshaft
revolution after the top dead center position initiating the power
stroke. Despite being started after the end of the combustion
process, one can therefore note that the auxiliary open phase
starts quite early in the power stroke, before the piston has gone
halfway down to its bottom dead center position. At that point in
time, the pressure within the cylinder is still quite high,
typically more than 10 bars, and in some cases superior to 50 bars,
which is much higher than the pressure in the intake line, even in
the case of a turbocharged engine. As a consequence, the opening of
the intake port results in a flow of gases from the cylinder to the
intake line, as evidenced by the negative values of the mass flow
rate through the intake port represented on FIG. 2. The gases which
flow out of the cylinder through the intake port are those
resulting from the prior combustion process and are therefore
comparable in their composition to exhaust gases which would
conventionally be expelled from the combustion chamber to the
exhaust line during the exhaust stroke.
[0019] Nevertheless, at that point in time corresponding to the
start of auxiliary open phase of the intake valve, the temperature
of the gases in the combustion chamber are still very high,
especially if compared to the temperature of exhaust gases which
are expelled to the exhaust line in the exhaust strokes. One reason
for this is that these gases have only undergone a very partial
expansion, because the piston has yet only traveled less than 20 to
40% of its displacement towards the bottom dead center, and
therefore they have undergone only a very partial corresponding
temperature drop. Another reason is that, during this very short
period of time between the end of the combustion and the start of
the auxiliary open phase, very little heat has been transferred
from the gases to the cylinder parts.
[0020] As a result, the gases which are expelled to the intake line
are at a very high temperature. Such gases can be up to 1500 C
hotter than exhaust gases expelled at the end of the exhaust
stroke.
[0021] Of course, opening of one of the ports of the cylinder so
early in the power stroke is detrimental to the amount of work
which can be retrieved by the piston, which has adverse
consequences on the engine output and on its efficiency.
[0022] Therefore, the auxiliary open phase of the intake valve
should be short in time. The duration of the auxiliary open phase
is preferably within 15 to 50 degrees. In other words, the
auxiliary open phase preferably ends between 50 and 120 degrees of
crankshaft revolution after the top dead center position initiating
the power stroke. In the example shown on FIG. 2 the duration of
the auxiliary open phase is of approximately 30 degrees of
crankshaft rotation, so that it ends at approximately 80 degrees of
crankshaft rotation after the top dead center in the power stroke.
In any case, the end of the auxiliary open phase will occur before
the end of the power stroke, i.e. before the piston reaches the
bottom dead center position. In the example shown, the auxiliary
open phase is entirely contained within the first half of the power
stroke.
[0023] Also, it can be noticed on FIG. 2 that the degree of opening
of the intake port during the auxiliary open phase, as represented
for example by the valve lift in the case of a poppet valve, can be
much smaller than the degree of opening of the intake port during
the main open phase. Also, in the case of an engine having several
intake ports, not all the ports of a given cylinder, and possibly
only one of them, are opened during an auxiliary open phase, to
limit the overall degree of opening of the intake ports during said
auxiliary open phase. Nevertheless, that port which is opened for
performing an auxiliary open phase can also be opened to perform a
main open phase, so that it is not a port dedicated to said
auxiliary open phase.
[0024] As a result of this auxiliary opening phase, a certain
quantity of combustion products is expelled directly to the intake
line. More particularly, in the configuration of the engine
arrangement of FIG. 1, the combustion products are stored in the
intake manifold, and more specifically in the duct or ducts which
correspond to the intake port(s) which have been controlled to
achieve such an auxiliary open phase. Those combustion products can
be qualified as direct high temperature EGR gases, as opposed to
indirect EGR gases which are typically re-circulated through the
conduit 30.
[0025] It is to be mentioned that, although not represented on the
example of FIG. 1, the intake manifold could be equipped with a
valve system for isolating the intake ducts corresponding to
different cylinders. Such valve system can comprise one way
check-valves for each duct, so that combustion products expelled
from one cylinder to the intake line during an auxiliary open phase
can not reverse flow further in the intake line beyond those
valves. Thereby, the combustion products would be surely confined
to the intake ducts corresponding to that cylinder.
[0026] In any case, the combustion products which have been
expelled to the intake line, the so-called direct high temperature
EGR gases, are for the most part re-admitted in the cylinder at the
following main open phase of the intake port(s), together with
fresh air. As a result, the gases which are admitted in the
cylinder for the next combustion process are a mixture of fresh air
and of combustion products which have been expelled to the intake
line directly through the intake port in the auxiliary open phase.
The temperature of such a mixture is of course higher than the
temperature of the fresh air typically provided through the intake
line. The increase of temperature is of course dependent on the
proportion between the fresh air and the combustion products which
are present in the mixture. This proportion can be varied by
varying the duration of the auxiliary open phase of the intake
valve, and/or by varying the degree of opening of the intake
port.
[0027] Of course, during this following main open phase of the
intake port(s), it could be provided that indirect EGR gases, which
have been re-circulated through the EGR conduit 30, are also
admitted in the cylinder, together with some fresh air and with
direct high temperature EGR gases. Such an option would enable to
adjust the temperature of the mixture for a given ratio of EGR
gases compared to fresh air.
[0028] When the routine of having an auxiliary open phase of the
intake valve is carried out for a cylinder during a certain number
of consecutive cycles of the cylinder, it can be seen on FIG. 3
that the temperature inside the cylinder is expected to be higher
than the temperature during a conventional cycle. On FIG. 3 can be
seen curves VL representing the intake port control, Tref
representing the reference temperature inside the cylinder without
use of the auxiliary open phase routine, and T representing the
temperature in the cylinder when such routine is implemented,
expressed as a function of or the crank rotation angle, where the
top dead center position of the piston initiating the power stroke
is given the value 0. This increased temperature of the gases
inside the cylinder will inevitably result in a higher heat
transfer towards the cylinder parts, and therefore a higher and
quicker temperature increase of the global engine temperature. This
will also result in a higher temperature of the exhaust gases which
are expelled to the exhaust line during the exhaust stroke.
Computer simulations have shown that, upon exit of the cylinder,
exhaust gases can have a temperature increase of more than 1000 C
when the auxiliary open phase is implemented, compared to when it
is not implemented.
[0029] Of course, as stated above, practicing the method of
according to the invention with the auxiliary open phase will bring
a penalty in terms of engine efficiency, so that this method may
only be desirable on specific instances. In most cases, the method
will be desirable only where, at specific times, additional heat
generation in the engine would be desirable, for example at engine
cold-starting or when it is desired to regenerate a particulate
filter, or for accurately controlling operating conditions of
after-treatment systems. Therefore, the invention will be
preferable used in connection with an engine arrangement where the
intake port control means are capable of controlling the
corresponding intake ports with or without the routine of
controlling the intake port to achieve an auxiliary open phase
during the power stroke, depending on the instant engine operating
conditions. Of course, if the engine is of a camless type, having
for example electronically piloted electric or electro-hydraulic
valve actuators, it will be easy for the skilled man in the art to
develop a proper electronic control unit capable of controlling the
ports with or without the routine. If the engine is equipped with
cam driven valves, there are numerous known devices which can
achieve at least two control laws for a same valve. Such devices
are already implemented to selectively drive the exhaust valves
according to at least two controls laws, depending on whether or
not it is desired to provide one or several additional open phases
of the exhaust port during the compression stroke for enhancing the
engine braking. Examples of such devices are described in documents
U.S. Pat. No. 5,193,497 and U.S. Pat. No. 5,890,469. The skilled
man in the art can rely on the disclosure of these documents to
devise a corresponding system for controlling the intake valves of
an engine arrangement which is to be controlled according to the
invention.
[0030] The method according to the invention will advantageously be
performed in view of heating up the engine arrangement, especially
at cold start. The method can also be performed in view of heating
up an exhaust after-treatment system. Preferably, it will be
performed at low engine loads.
* * * * *