U.S. patent application number 11/816223 was filed with the patent office on 2008-10-23 for device for thermal control of recirculated gases in an internal combustion engine.
This patent application is currently assigned to Peugeot Citroen Automobiles SA. Invention is credited to Emmanuel Boudard, Pierre Dumoulin, Armel Le Lievre.
Application Number | 20080257526 11/816223 |
Document ID | / |
Family ID | 34954563 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257526 |
Kind Code |
A1 |
Le Lievre; Armel ; et
al. |
October 23, 2008 |
Device for Thermal Control of Recirculated Gases in an Internal
Combustion Engine
Abstract
The invention relates to a device for thermal control of
recirculated gases in an internal combustion engine, comprising a
liquid coolant circuit (1), connected to an internal combustion
engine (2). The circuit (1) comprises first thermal coolant/air
heat exchanger means (3), such as a radiator, arranged in a first
loop (13), connected to the engine (2), second thermal
coolant/recirculated exhaust gas heat exchanger means (4) arranged
in a second loop (14), connected in parallel to the first loop
(13), in order to permit the supply of the second thermal heat
exchanger means (4) with coolant from the first thermal heat
exchanger means (3), characterized in that the ends of the second
loop (14) are directly connected to the body of the first thermal
exchanger means (3).
Inventors: |
Le Lievre; Armel;
(Montesson, FR) ; Boudard; Emmanuel; (Voisins Le
Bretonneux, FR) ; Dumoulin; Pierre; (La Garenne
Colombes, FR) |
Correspondence
Address: |
NICOLAS E. SECKEL;Patent Attorney
1250 Connecticut Avenue, NW Suite 700
WASHINGTON
DC
20036
US
|
Assignee: |
Peugeot Citroen Automobiles
SA
Velizy Villacoublay
FR
|
Family ID: |
34954563 |
Appl. No.: |
11/816223 |
Filed: |
February 7, 2006 |
PCT Filed: |
February 7, 2006 |
PCT NO: |
PCT/FR06/50105 |
371 Date: |
August 14, 2007 |
Current U.S.
Class: |
165/51 |
Current CPC
Class: |
F02M 26/28 20160201;
F01P 2005/105 20130101; F01P 2060/08 20130101 |
Class at
Publication: |
165/51 |
International
Class: |
F01N 5/02 20060101
F01N005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 14, 2005 |
FR |
0550416 |
Claims
1. Device for thermal control of recirculated gases of an internal
combustion engine, comprising a circuit of liquid coolant connected
to an internal combustion engine, the circuit comprising first
coolant/air heat exchanger means, arranged in a first loop
connected to the engine, second coolant/recirculated exhaust gases
heat exchanger means arranged in a second loop connected in
parallel to the first loop to enable supplying the second heat
exchanger means with coolant from the first heat exchanger means,
wherein the ends of the second loop are directly connected to the
body of the first heat exchanger means.
2. Thermal control device according to claim 1, wherein the ends of
the second loop are connected to an inlet and an outlet,
respectively, of the first heat exchanger means distinct from the
inlet and outlet connecting the first heat exchanger means to the
engine.
3. Thermal control device according to claim 1, wherein the ends of
the second loop are connected to the first heat exchanger means so
as to connect the inlet and outlet of the second heat exchanger
means with an outlet and an inlet, respectively, of the first heat
exchanger means.
4. Thermal control device according to claim 1, wherein the first
heat exchanger means comprise at least one heat exchanger core
connected to a fluid inlet assembly and a fluid outlet assembly,
and the ends of the second loop are directly connected to the fluid
inlet and outlet assemblies, respectively.
5. Thermal control device according to claim 1, wherein the second
loop comprises controlled means for activating the coolant flow
rate.
6. Thermal control device according to claim 2, which comprises
means for controlling the coolant flow rate allowed to circulate in
the first loop.
7. Thermal control device according to claim 6, wherein the means
for controlling the flow rate comprise a valve of the proportional
type.
8. Thermal control device according to claim 6, wherein the means
for controlling the flow rate comprise a pump.
9. Thermal control device according to claim 6, wherein the second
loop comprises controlled means for activating the coolant flow
rate, and wherein the means for activating the flow rate in the
second loop and the means for controlling the flow rate in the
first loop are independent, so as to enable starting or stopping
the means for activating the flow rate in the second loop whatever
the flow rate of coolant allowed to circulate in the first
loop.
10. Thermal control device according to claim 1, wherein the first
coolant/air heat exchanger means comprises a radiator.
11. Thermal control device according to claim 5, wherein the means
for activating the coolant flow rate is a pump.
12. Thermal control device according to claim 7, wherein the valve
of the proportional type is a thermostat.
Description
[0001] The invention relates to a device for thermal control of
recirculated gases of an internal combustion engine.
[0002] In order to increase the efficiency of the recirculation of
a portion of the exhaust gases into the fresh intake gases of an
engine, with a view at reducing in particular emissions of NOx
gases, a heat exchange is usually provided between these
recirculated exhaust gases and the liquid coolant of the engine. To
this effect, a recycled gases/coolant heat exchanger is supplied
with coolant from the exit of the engine by a branch pipe on the
water outlet assembly of the engine, upstream of the
thermostat.
[0003] However, these known systems are not satisfactory in certain
operating situations of the engine, as the temperature of the
recirculated exhaust gases is not well controlled. In particular,
when the temperature of the engine increases, the coolant reaches
high temperatures detrimental to the efficiency of the exhaust
gases recycling for reducing nitrogen oxides.
[0004] FIG. 1 illustrates a device for thermal control of
recirculated gases of an internal combustion engine according to
the prior art, comprising a circuit 1 of coolant connected to an
internal combustion engine 2, the circuit comprising first
coolant/air A heat exchanger means A, such as a radiator, arranged
in a first loop 13 connected to the engine 2, second
coolant/recirculated exhaust gas GB heat exchanger means 4 arranged
in a second loop 14 connected in parallel to the first loop 13, to
enable supplying the second heat exchanger means 4 with coolant
from the first heat exchanger means 3.
[0005] Such a construction, conform to the preamble of the main
claim, is described in particular in the document FR2752440A1.
[0006] The flow rate of the coolant allowed to circulate in the
first loop 13 is controlled, for example, by a thermostat 7
arranged in the water outlet assembly 16.
[0007] However, in this type of hydraulic construction using a
radiator, there is a risk that the fluid flow rate will fluctuate
among its components.
[0008] Indeed, when the thermostat 7 is completely open to let the
coolant circulate in the first loop (arrow 23 on FIG. 1), an
parasitic inversion (arrow 24 on FIG. 1) of the circulation
direction of fluid can occur in a portion 14 of the circuit 1.
[0009] A first pump 10, for example, a mechanical pump, linked to
the engine 2, performs the activation of the fluid flow rate in the
cooling circuit 1. At high engine speeds, it can happen that a
portion of the fluid exiting the engine 2 in the area of the
thermostat 7 enters directly into the second exchanger 4
(coolant/recirculated gases exchanger) instead of passing first
quasi-exclusively through the radiator 3. This flow rate inversion
occurs even when a second pump 5 arranged in the loop 14 of the
second exchanger 4 operates in a direction opposed to this
inversion.
[0010] For a given circuit, when the engine speed is in the order
of 3300 rev/min, for example, the mechanical pump 10 of the engine
generates a flow rate in the radiator 3 in the order, for example,
of 8000 l/hr. In these conditions, a conventional radiator causes a
pressure drop in the order of 300 mbar.
[0011] When the flow rate is zero, an electrical pump 5 of standard
type ensures a counter-pressure in the second loop of about 200
mbar, i.e., lower than the pressure drop in the radiator 3.
[0012] As a result, in some operating conditions, there is an
inversion of the circulation direction of the fluid in the second
exchanger 4 (this parasitic circulation direction is shown by the
arrows 24 on FIG. 1). This circulation inversion is preceded by an
operating point during which the flow rate is zero or quasi-zero in
the second exchanger 4. This zero-flow rate operating point can
occur, for example, at an engine speed in the order of 2700
rev/min.
[0013] This type of defective operation causes a drop in the
efficiency of the radiator and of the second exchanger 4. In case
of a zero or low flow rate in the second exchanger 4, there is, in
addition, a risk that the coolant will boil in this second
exchanger 4.
[0014] Further, these degraded operating points can coincide with
states of the engine or of other parts in which the thermal control
is crucial. Accordingly, it is necessary, on the one hand, to
detect the flow rate of fluid circulating in the second exchanger
4, and on the other hand, to provide a complex control strategy for
the pump 5.
[0015] To solve these problems, one solution consists in providing
a check valve 17 in the second branch 14, so as to reduce the flow
rate in this branch in a cooling phase of the engine (see FIG. 1).
This solution is generally satisfactory for the inverted parasitic
flow rate, but it causes a high cost increase in the context of
mass production. In addition, the use of a check valve generates an
additional pressure drop in the hydraulic circuit and requires the
calibration of a leak to maintain a minimum flow rate in the
exchanger 4.
[0016] Another solution consists in increasing the power of the
electrical pump 5 arranged in the second loop 14. This solution has
the same drawbacks in terms of costs, requires a complex control
strategy for the pump 5, and triggers excess fuel consumption.
[0017] An objective of the present invention is to remedy all or
part of the drawbacks of the prior art mentioned above.
[0018] To this effect, the device for thermal control of
recirculated gases of an internal combustion engine according to
the invention, otherwise conform to the generic definition given in
the preamble above, is characterized essentially in that the ends
of the second loop are directly connected to the body of the first
heat exchanger means.
[0019] Further, the invention can have one or several of the
following characteristics: [0020] the ends of the second loop are
connected to an inlet and an outlet, respectively, of the first
heat exchanger means distinct from the inlet and outlet connecting
the first heat exchanger means to the engine, [0021] the ends of
the second loop are connected to the first heat exchanger means so
as to connect the inlet and outlet of the second heat exchanger
means with an outlet and an inlet, respectively, of the first heat
exchanger means, [0022] the first heat exchanger means comprise at
least one heat exchanger core connected to a fluid inlet assembly
and a fluid outlet assembly, the ends of the second loop being
directly connected to the fluid inlet and outlet assemblies,
respectively, [0023] the second loop comprises controlled means for
activating the coolant flow rate, such as a pump, [0024] the device
comprises means for controlling the coolant flow rate allowed to
circulate in the first loop, [0025] the means for controlling the
flow rate comprise a valve of the proportional type, such as a
thermostat, [0026] the means for controlling the flow rate comprise
a pump, [0027] the means for activating the flow rate in the second
loop and the means for controlling the flow rate in the first loop
are independent, so as to enable starting or stopping the means for
activating the flow rate in the second loop whatever the flow rate
of coolant allowed to circulate in the first loop.
[0028] Other specificities and advantages will appear by reading
the following description, made in reference to the Figures in
which:
[0029] FIG. 1 is a schematic view of a cooling circuit of an
internal combustion engine according to the prior art,
[0030] FIG. 2 is a schematic view of a cooling circuit of an
internal combustion engine according to an exemplary embodiment of
the invention,
[0031] FIG. 3 is a schematic front view of a detail of FIG. 2,
illustrating an exemplary embodiment of the heat exchanger means
such as a radiator, in accordance with the invention,
[0032] FIG. 4 is a schematic cross-section view along line AA of
the heat exchanger means of FIG. 3,
[0033] FIG. 5 is a schematic view of a graph illustrating
comparative coolant fluid flow rates in the second loop 14 of the
circuit as a function of the engine speed.
[0034] In addition to the characteristics described above, the
device for thermal control according to the prior art shown on FIG.
1 also comprises an optional third loop 19 connected in parallel to
the first 13 and second 14 loops of the circuit 1. The third loop
19 comprises a coolant/air exchanger 18 such as an air heater
intended, for example, to yield calories to a volume such as a
passenger compartment of a vehicle.
[0035] Such an internal combustion engine 2 comprises, in a
standard manner, intake conduits (not shown) supplying fresh gases
to the cylinders of the engine 2. The burned gases GB generated by
the combustion in the cylinders are collected by the exhaust
conduits (not shown). In a standard manner, a derivation makes it
possible to recirculate a portion of the exhaust gases into the
intake. To this effect, the derivation can comprise a valve
controlled so as to regulate the flow rate of the recirculated
gases.
[0036] The device according to the invention will now be describe
by reference to FIG. 2. For concision purposes, the elements
identical to those described above are designated by the same
reference numerals and will not be described in details a second
time.
[0037] The circuit 1 according to the invention is different from
that described previously in that the second loop 14 which contains
the coolant/recirculated exhaust gases GB exchanger 4 is connected
in parallel to the first loop 13 directly to the body of the first
heat exchanger means 3. Further, this second loop 14 can operate
without check valve 17, and in this case, it includes only a pump
5, preferably an electrical pump.
[0038] According to the invention, a very high reduction of the
pressure drops at the ends of the second loop 14 is observed, as
compared to the solutions of the prior art.
[0039] For example, the two ends of the second loop 14 are directly
connected to the radiator 3, so as to connect the inlet 11 and
outlet 12 of the coolant/recirculated exhaust gases exchanger 4 to
an outlet 6 and an inlet 5, respectively, of the radiator 3.
[0040] The radiator 3 can comprise a heat exchanger comprising at
least one tube/fins core 7 whose ends are connected to a fluid
inlet assembly 8 and a fluid outlet assembly 9, respectively (FIGS.
3 and 4). The two ends of the conduits of the second loop 14 can be
directly connected to the fluid inlet assembly 8 and fluid outlet
assembly 9, respectively, of the radiator 3.
[0041] Thus, the invention makes it possible to minimize the
hydraulic pressure drops at the terminals of the circuit 14, in
particular within the fluid inlet 8 and outlet 9 assemblies, as
compared to the system according to the prior art in which the
second loop 14 is connected to the conduits or hoses of the first
loop 13.
[0042] Thus, the invention makes it possible, for a same type of
pump 5 arranged in the second loop 14, to postpone the risky
operating points (zero or inverted flow rate in the second loop 14
of the coolant/recirculated exhaust gases exchanger) until higher
engine speeds. The device according to the invention even makes it
possible, in some cases, to eliminate these risky operating modes.
The use of a check valve on the second loop 14 can thus be
avoided.
[0043] FIG. 5 illustrates on a same graph the variation of the flow
rate D of coolant in the coolant/recirculated exhaust gases
exchanger 4 in liters by minute (in ordinates) as a function of the
engine speed N in revolutions per minute (in abscissa). The graph
represents this flow rate for a circuit according to the prior art
(curve 20) and for a circuit modified in accordance with the
invention (curve 21).
[0044] This is to say that, for a hydraulic circuit according to
the prior art (conform to FIG. 1), it is observed that the flow
rate in the second loop 14, and thus in the coolant/recirculated
gases exchanger 4, becomes zero and is inverted beginning at about
2700 rev/min.
[0045] In contrast, for an identical circuit where only the
connection of the second loop 14 has been modified according to the
invention (branch pipe directly onto the radiator 3 in accordance
with FIG. 2), the flow rate D in the second loop 14 remains above
about 8 liters per minute.
[0046] The invention enables an optimal thermal control (cooling)
of the engine while avoiding the risk that the fluid would boil in
the coolant/recirculated exhaust gases exchanger 4 and the risk
that the efficiency of this exchanger 4 would become degraded.
[0047] As shown on FIGS. 3 and 4, the ends of the second loop 14
can be connected to an inlet 5 and an outlet 6, respectively, of
the radiator 3, which are distinct of the inlet 15 and outlet 16
for connecting the radiator 3 to the engine 2.
[0048] In particular, the device according to the invention makes
it possible to ensure, with a simple and inexpensive structure, an
optimal temperature of the recirculated exhaust gases.
[0049] In addition, the flow rate increase in the exchanger 3
generated by the pump 5 makes it possible to obtain an increase in
efficiency of this exchanger for cooling the engine.
[0050] The nominal efficiency of the coolant/recirculated exhaust
gases exchanger 4 is maintained over a very large operating range
of the engine (including the usage points currently defined in this
exchanger). In particular, the invention makes it possible to
ensure a minimum flow rate of 5 to 6 l/min in a standard exchanger
4 when this exchanger must be operational.
[0051] According to other specificities, the circulations of the
coolant in the first 13 and second 14 loop can be controlled
independently from each other. The circulation of the coolant in
the third loop 19 is also independent form the circulation in the
other loop 14.
[0052] When the engine 2 is very hot, the circuit 1 according to
the invention makes it possible to supply the coolant/recirculated
exhaust gases exchanger 4 with coolant cooled by the radiator
3.
[0053] When the thermostat 7 controlling the natural circulation of
the coolant in the radiator 3 is closed, the coolant circulating in
the coolant/recirculated exhaust gases exchanger 4 remains at a
temperature close to the ambient temperature. This way, the
efficiency of the exchanger 4 is improved, which promotes the
reduction of the pollutants in the exhaust gases of the engine (in
particular NOx).
[0054] The electrical pump 5 of the second circuit 4 can be started
to increase the heat exchange between the coolant and the
recirculated exhaust gases.
[0055] The stopping of this electrical pump 5 also makes it
possible to eliminate the circulation of coolant in the
coolant/recirculated gases exchanger 4 in the starting phase of the
engine, i.e., at a time when the start of a catalysis system has
not yet been triggered (in general when the temperature of the
exhaust gases is lower than a threshold temperature comprised
between 100 and 250.degree. C., in general about 150.degree. C.).
This arrangement makes it possible to reduce the pollutants, in
particular of the CO and HC type, and thus, it makes it possible to
eliminate the standard by-pass on the coolant or on the exhaust
gases.
[0056] Means for measuring the temperature of the exhaust gases,
such as a sensor, can be provided to this effect in the area of the
exhaust.
[0057] In the same way, if the circuit 14 comprises a check valve,
when the recirculation of the exhaust gases is interrupted by the
corresponding valve, the pump 5 arranged in the second loop 14 is
not started. Preferably, the pump 5 is stopped with a determined
delay after the recycling is stopped. Thus, preferably, the pump 5
arranged in the second loop 14 is supplied only when the exhaust
gases are recirculated and their temperature has reached a
threshold value (catalyst started).
[0058] When the operating mode of the engine requires simultaneous
cooling of the engine 2 and of the recirculated exhaust gases, the
thermostat 7 is opened and the pump 5 arranged in the second loop
14 is started. The coolant cooled in the radiator 3 is divided
between the engine 2 and the coolant/recirculated exhaust gases
exchanger 4. Similarly, the radiator 3 is supplied by a mixture of
liquid from the engine 2 and from the coolant/recirculated exhaust
gases exchanger.
* * * * *