FR2921689A1 - Exhaust gas heat energy recovery device for double-walled line of diesel engine of motor vehicle, has heat exchanger integrally housed between heat shield and exhaust line, and solenoid valve connecting exchanger to heating circuit - Google Patents

Abstract

The device has a heat exchanger (1) for recovering heat energy on an exhaust line (3) i.e. double-walled line, where the heat exchanger is in helical form with turns or in cylindrical envelope form. The exchanger is formed from a duct, where the heat-transfer liquid e.g. water, circulates. The exchanger is integrally housed between a heat shield (14) and the line. A solenoid valve (6) connects the exchanger to a heating circuit i.e. radiator, or to a coolant compensation circuit (4). The shield presents an aluminum sheet with a thermal insulation fiber layer.

Description

  The present invention relates to a thermal recovery device for an exhaust line with an integrated heat exchanger for recovering the thermal energy of the exhaust gas of an internal combustion engine. integrated heat exchanger for recovering the thermal energy of the exhaust gas of an internal combustion engine, and a motor vehicle comprising such a heat recovery device. More specifically, the present invention relates to a thermal recovery device for an exhaust line with a heat shield and heat exchanger integrated in this heat shield.

Exhaust lines comprising a heat shield are well known from the state of the art. In general, a heat shield of an exhaust line is in a form adapted to the tunnel which receives it in the motor vehicle, this heat shield being fixed on the exhaust line at least partially surrounding this line at a distance. Its role is to limit the heat energy radiation from the engine and especially the exhaust line on the mechanical parts, for example metal or plastic, located near this exhaust line. This heat shield is, for example, formed of an aluminum layer with, if necessary, a layer of insulation. An attachment directly to the exhaust line, involving contact with this line, can damage this heat shield and even tear it. Due to its role of thermal insulation, it is subjected to high temperatures which can also damage it. In both cases, this results in a rise in the temperature in the vicinity of the exhaust line by heat radiation which can cause a gradual melting of certain elements of the vehicle, including plastic elements located in the vicinity which may cause a fire hazard. The recovery of thermal energy generated during the operation of an internal combustion engine and the use of recovered thermal energy take a more and more place of motor vehicle design. However, in most recovered heat comes from the cooling circuit. One of the first examples is the use of cooling water for preheating fuel. Another source for recovering thermal energy is the exhaust system of an internal combustion engine. According to a known design, the exhaust gas passes through a heat exchanger which constitutes a bypass, or bypass, of the exhaust system. With regard to thermal heat recuperators, these are also well known in the state of the art. Such a thermal recuperator operates with the heat recovery of the exhaust gas and heats a heat transfer fluid passing through a heat exchanger, included in this recuperator. For example, the document FR-A-2 718 491 describes a device for recovering energy from a motor vehicle engine exhaust, comprising an annular boiler assembled on a section of flue gas discharge pipe, connected by a channeling to a recuperator condenser and an auxiliary capacity deformable under the effect of pressure, located at a low point of the liquid circuit, of sufficient capacity to receive under pressure stress all the heat transfer fluid contained in the system. The purpose of this document is to recover some of the energy dissipated in the exhaust of a large engine in the case, the thermal energy to use it, directly to supplement the heating of the passenger compartment, either rapid heating of the cooling circuit which is equipped with the engine. The technology of this document, however, is quite old and uses tare springs and a deformable capacity whose operation can be disturbed during the operation of the vehicle, for example by the vibrations caused during the journey of the vehicle. Such elements do not find application in the case of piloting a heat recovery device by electronic means as is currently used. Figure 1 illustrates another example of a heat recovery unit. This is arranged, for example after the particle filter FAP on a bypass line 1 'of the exhaust line 1 of the combustion gases and comprises an inlet e and an outlet f for a heat transfer fluid leaving the exchanger ET, a three-way valve v, for example disposed at the junction of the exhaust line 1 'of the heat exchanger with the main exhaust line 1 and a thermal decoupler disposed before the heat exchanger being also present. The operation of such an exhaust line with such a heat recovery device is composed of two cycles. In the first cycle, the exhaust line 1 'of the heat exchanger is not powered and the exhaust line 1 operates normally. When the exhaust line 1 'of the heat exchanger is energized, the heat recovery device recovers heat from the exhaust gas and heats a heat transfer fluid in the heat exchanger ET, for example water that leaves in the direction of the vehicle's water supply or BSE box to be returned to the air conditioning unit. This heat exchanger ET has, on the other hand, a length LE and a diameter DE proportional to the heat exchange that it is desired to have as a function of the existing motorization, the internal diameter D of the exhaust line 1 before derivation being also to take into account.

This heat recovery device, placed in bypass of the exhaust line, has many disadvantages. Firstly, since the heat recovery device is dependent on the motorization of the vehicle, this involves several heat recovery references and several diameters DE of the exhaust line 1 'of this heat recovery unit. It may also be necessary to modify the references of the exhaust line to ensure better heat exchange. There are therefore several references of exhaust systems and heat recovery systems to be managed in the production plant or at the equipment manufacturer, which is a disadvantage with repercussions on production costs. This also has implications for factory and supplier logistics and after sales service. Secondly, the thermal heat recovery device does not work continuously but only when its exhaust line is powered. This results in a loss of efficiency of this heat recovery. It is also obvious that a system with two exhaust lines causes heat loss that can be as harmful to the surrounding elements of the motor vehicle, especially when they are based on plastic.

The object of the invention is, on the one hand, to overcome these drawbacks by proposing a thermal recovery device from an exhaust line, with the heat exchanger of this thermal recovery device integrated into the exhaust line without the need for modification of the exhaust line references and, secondly, to obtain an improvement of the efficiency of the heat recovery unit in operation. This object is achieved with a thermal recovery device in association with an exhaust line for the exhaust of the combustion gases of the combustion engine of a motor vehicle, this exhaust line comprising, inter alia, a heat shield for its insulation with respect to the outside, this recovery device comprising a heat exchanger, able to recover the energy on this exhaust line, this heat exchanger being formed from a conduit in which circulates a coolant liquid, characterized in that the heat exchanger is housed integrally in the heat shield between it and the exhaust line.

According to additional features of the present invention: the duct of the heat exchanger is shaped to surround the exhaust line, and this heat recovery device comprises a solenoid valve intended to connect the heat exchanger alternately to a heat exchanger circuit; heating or a duct forming a cooling zone, this solenoid valve being four-way and two operating positions, the solenoid valve connecting the heat exchanger, in the first operating position, to the duct forming the cooling zone, and in the second position, to a duct short-circuiting the duct forming a cooling zone by connecting the heat exchanger directly to the heating circuit, - the duct of the heat exchanger is shaped to surround the exhaust line and this device heat recovery system comprises two solenoid valves for connecting the heat exchanger alternately a heating circuit or a duct forming a cooling zone, these two solenoid valves being three-way and two operating positions, the two valves connecting the heat exchanger, in the first operating position, to the duct forming the cooling zone and, in the second position, to a conduit short-circuiting the cooling zone duct and connecting the heat exchanger directly to the heating circuit, the heat exchanger has a helical shape with several turns, each of the turns surrounding the exhaust line or the heat exchanger has the shape of a cylindrical envelope obtained by a provision of the meandering conduit along the exhaust line, - the coolant comes from the cooling device of the engine and is directed towards the heating circuit by the service box of this coolant, said fluid being preferably water with, the if necessary, additives to improve its properties, - the heat recovery unit has its own independent heat transfer fluid circuit and comprises at least one pump in this circuit for effecting the flow of fluid, - the heat shield has an aluminum foil 25 with, if appropriate, a layer of thermally insulating fibers, - the heat exchanger extends in the heat shield only over a portion of it, - the heat exchanger is shaped not to enter directly into physical contact with the exhaust line and / or the heat shield and the exhaust line includes fixing means for attaching the heat exchanger and / or the heat shield to the vehicle body, or one of these two elements 35 comprises fastening means for fixing it to the vehicle body, the other element having fixing means for securing it to the first element, - the line The exhaust is a double-walled line, the heat exchanger and the heat shield being housed between these two walls of said line.

The present invention also relates to a motor vehicle, characterized in that it comprises such a thermal recovery device. The device according to the invention is therefore designed for recovery of thermal energy by connection. For this reason, the heat exchanger does not have a water jacket or any other body 15 conforming to the exhaust line. Furthermore, the heat exchanger surrounds the exhaust line and thus recovers thermal energy in all directions of emission. In addition, this heat exchanger can be located at a location close to the engine to benefit from the greatest thermal energy possible. The heat shield, incorporating the heat exchanger, prevents heat loss and increases the efficiency of this heat recovery unit.

Other features and advantages of the invention will emerge from the description of the two embodiments of the invention which is made with reference to the drawings in which: FIG. 1 represents a schematic diagram of a provision of FIG. a heat recovery unit on an exhaust line according to the state of the art; Figure 2 shows the arrangement of a heat exchanger of a thermal recovery device on an exhaust line according to a first embodiment of the invention; FIG. 3 represents the arrangement of FIG. 2 in a simplified perspective view; FIG. 4 shows the arrangement of a heat exchanger of a thermal recovery device on an exhaust line according to a second embodiment of the invention; and - Figure 5 shows the device of Figure 4 in a simplified perspective view.

Figure 1 has already been detailed in the introductory part of this description.

As can be seen in FIG. 2, the exhaust line 3 comprises, among others, a group 11, comprising, for example, a catalyst and a particulate filter and a muffler or muffler 12. On this exhaust line 3 , is mounted a heat exchanger 1 of the heat recovery device surrounding this exhaust line 3. The passage of the exhaust gas is in the direction of the arrow A at the bottom of this figure.

The heat shield may be, at least, symbolized by the dots 14 in this figure and includes all these elements 1, 11, 12. Indeed, the dashed lines illustrate the heat recovery zone that necessarily covers the heat shield but that it can extend further upstream or downstream of the exhaust line 3. The heat exchanger 1 of the thermal recovery device is formed from a conduit 2 for a coolant liquid. This duct 2 is part of a closed heating and cooling circuit and is shaped to surround an exhaust line 3, such as an intermediate line of the exhaust system of an internal combustion engine. In order to ensure thermal energy recovery by connection, and not by conduction, the heat exchanger 1 advantageously has a helical shape with several turns or the shape of a cylindrical envelope. In this case, the inner diameter of the turns is greater than the outer diameter of the exhaust line 3, when the exhaust line 3 and the heat exchanger 1 are hot. When the heat exchanger 1 has the shape of a cylindrical envelope, it is advantageously obtained by an arrangement of the conduit 2 in meanders or coils, with the elongate portions of the meanders along the exhaust line 3. The heat exchanger 1 is traversed by a heat transfer fluid from a reserve 9 of heat transfer fluid, for example, a water supply housing. The thermal recovery device comprises at least two heat transfer fluid circulation circuits, having at least some common parts, for directing the heat transfer liquid leaving the heat exchanger 1 to the cooling compensation circuit 4, for the first circuit, or to radiators for respectively heating the passenger compartment and the cooling of the engine 10, for the second circuit. The common part of these two circuits conducts the coolant from the outlet of the heat exchanger 1 to a solenoid valve 6 provided with its management device. This solenoid valve 6 orients the heat transfer liquid according to defined momentary needs according to temperatures measured at specific locations towards the independent parts of the first or second circuit. Thus, the coolant flow is directed to the cooler compensation circuit 4 or to the radiators via the solenoid valve 6. This solenoid valve 6 is controlled by a control module 8 taking into account signals representative of the temperature of the coolant. passing through the radiators.

These signals are sent by the coolant reserve 9 which also supplies and controls the air conditioner unit 10. Manual control or, at least, manual preselection is possible.

Figure 3 shows a first embodiment of the present invention. As can be seen in this figure, the heat exchanger 1 of the thermal recovery device, mounted around the exhaust line 3, is controlled by a four-way solenoid valve 6. This heat exchanger 1 of the thermal recovery device is thus connected to the chiller compensation circuit 4 when the solenoid valve 6 is in a position, and it is connected to the heating system of the passenger compartment when the solenoid valve 6 is in position. other two possible positions. The heat transfer fluid circulates in the heat exchanger entering into it according to the arrow E and out along the arrow S.

The second embodiment of the invention, which is shown in FIG. 4, differs from the first in that it comprises two solenoid valves 7, 7 'interconnected by a duct 13. The duct 13 connects the heat exchanger 1 of the heat recovery device directly to the heating circuit and thus bypasses the cooling compensation circuit 4. The heat exchanger 1 of the heat recovery device can be fixed on the exhaust line 3 by a flange or by any other means. another suitable means ensuring a spacing between the duct 2 of the heat exchanger 1 of the thermal recovery device and the exhaust line 3. The same applies to the heat exchanger 1 of the thermal recovery device and the Thermal screen.

Figures 4 and 5 also show in dotted lines 14 the minimum position in length of the heat shield relative to the elements of the exhaust line 3 and the heat exchanger 1 of the thermal recovery device. The heat shield may have the shape of the tunnel of the vehicle that receives it and cover the entire area of this tunnel. The heat exchanger 1 of the heat recovery device will have a length determined by the desired heat input and will extend for this reason over a greater or lesser length of this heat shield. Preferably, the heat exchanger 1 of the thermal recovery device can be put in several places where there is a lot of heat release. In the figures, these places have been limited to the tunnel zone, this zone being a confined zone and the tunnel making it possible to recover a large calorific potential. For example, for diesel engines, the particle filter 11 is advantageously surrounded by the heat shield, with the heat exchanger 1 included between the heat shield and the filter 11, this filter 11 being one of the hottest places of the underbody of the vehicle, in particular during the regeneration phases of the filter. Indeed, during the regeneration phases of the filter, the temperature thereof must rise sufficiently to cause the combustion of accumulated particles.

It must however be kept in mind that the exhaust line with the heat exchanger and the heat shield according to the invention can be applied to diesel or gasoline engines. The heat shield may be only a few millimeters thick being composed only of aluminum and / or having an insulation layer based on insulating fibers, for example thermocompressed fibers. This heat shield is fragile and the heat exchanger 1 of the thermal recovery device is advantageously maintained spaced therefrom. Thus, in addition to allowing an efficient heat input for heating the internal compartment of the vehicle, the heat exchanger, thus disposed on the exhaust line, allows at the same time a heat removal advantageous for the life of the vehicle. the heat shield, because the heat recovery performed by the heat exchanger helps to spare the heat shield by not subjecting it to too high temperatures by evacuation of heat inside the heat shield. It will be noted that the arrangement of the exchanger on the exhaust line, in accordance with the invention, ensures that at the location where the thermal energy is recovered, the temperature of the skin of the exhaust manifold does not exceed is not degraded. This is achieved by the fact that the heat transfer between the tubing and the duct is done by convection and radiation, and not by conduction. The fact that the heat exchanger conduit surrounds the exhaust manifold ensures that the engine does not lose power due to the presence of this exchanger. Thus, the energy taken from the exhaust gas does not cause overconsumption of fuel. In a possible alternative of the present invention, the exhaust line may be of the double wall type. In this case, the heat exchanger and the heat shield are housed between these two walls. In this case, the heat shield is advantageously composed of fibers of insulating materials.

Third and fourth embodiments of the invention are also possible.

In these two embodiments, the heat recovery unit has its own independent heat transfer fluid circuit. Otherwise, the third and fourth embodiments essentially take up respectively the characteristics of the first embodiment, that is to say the presence of a four-way solenoid valve with two operating positions, and the second embodiment of the invention. invention, that is to say the presence of two solenoid valves with three channels and two operating positions.

Figures 2 to 5 may be repeated to illustrate these two modes, with the proviso that the heat transfer fluid is independent of the engine cooling fluid and the reserve 9 heat transfer fluid can not be the water service box. The duct 2 is therefore part of a closed circuit heating and cooling independent. To achieve the circulation of the heat transfer fluid specific to the heat recovery device, the latter is provided with a pump. Many advantages derive from these two embodiments of the present invention.

Firstly, it is obtained a better efficiency of the heat exchanger of the heat recovery device, compared to those already known in the state of the art. Indeed, according to the present invention, the circuit of the thermal recovery device is no longer connected with the cooling circuit of the heat engine which allows for a simpler heat transfer liquid circuit with fewer mounting parts and therefore easier to manufacture. Mainly, this circuit has a smaller volume of heat transfer liquid than if it were connected to the engine cooling circuit which allows to have a more reactive thermal recovery circuit with a heat rise curve simpler to control and therefore a better performance. Regarding the air conditioning of the vehicle, the device is near its place of use which provides a gain in implantation space. In addition, this independent circuit is more reliable and more controllable than when connected with the motor circuit. Finally, the heat transfer liquid is less polluted in an independent circuit than for a circuit connected with that of cooling the engine.

Many advantages derive from the present invention. Among others, we can cite a better performance of the heat exchanger of the heat recovery device, compared to those already known in the state of the art. In addition, a greater heat dissipation of the heat shield is guaranteed by the function of this heat exchanger which reduces the risk of damage to this heat shield when it is subjected to high temperatures. The thermal recovery device provides a great improvement in terms of thermal comfort within the vehicle by allowing to quickly heat the cabin, which provides, in comparison with existing additional heating systems, a less expensive solution without overconsumption of energy and without emissions. Thus, it has been found that the housing of the thermal recuperator in the heat shield implies a synergistic effect with interactive effects resulting in a better functioning of these two elements. When the heat transfer liquid is the same as the coolant, that is to say when the two circuits are connected to each other, the effective connection between the two circuits is advantageously controlled by a service box d 'water. This manages the distribution of "hot water" to the different receivers according to predetermined priorities.

Since the heating of the passenger compartment and the other places of thermal energy operation are mainly fed by the coolant of the cooling system of the engine, the thermal energy recovered from the exhaust gases constitutes additional energy. At the same time, the thermal energy recovered from the exhaust gases is more rapidly available than the thermal energy of the cooling circuit, in particular after starting the vehicle when cold. Also, the recovery device is designed to perform heat recovery permanently, but this energy is made available only in a controlled manner.

Claims (11)

1. Thermal recovery device in association with an exhaust line for exhausting the combustion gases of the combustion engine of a motor vehicle, this exhaust line (3) comprising, inter alia, a heat shield (14). ) for its insulation with respect to the outside, this recovery device comprising a heat exchanger (1), able to recover the energy on this exhaust line (3), this heat exchanger (1) being formed to from a conduit (2) where a heat transfer liquid circulates, characterized in that the heat exchanger (1) is housed integrally in the heat shield between it and the exhaust line (3). 2. Thermal recovery device according to claim 1, characterized in that the duct (2) of the heat exchanger (1) is shaped to surround the exhaust line (3), and in that this recovery device thermal device comprises a solenoid valve (6) for connecting the heat exchanger (1) alternately to a heating circuit or to a duct forming a cooling zone (4), this solenoid valve (6) being four-way and two operating, the solenoid valve (6) connecting the heat exchanger (1), in the first operating position, to the cooling zone duct (4), and, in the second position, to a duct short-circuiting the duct forming the cooling zone (4) by connecting the heat exchanger (1) directly to the heating circuit. 3. Thermal recovery device according to claim 1, characterized in that the duct (2) of the heat exchanger (1) is shaped to surround the exhaust line (3), and in that this recovery device thermal comprises two solenoid valves (7, 7 ') for connecting the heat exchanger alternately to a heating circuit or to a duct forming a cooling zone (4), these two solenoid valves (7, 7') being three-way and two operating positions, the two valves (7, 7 ') connecting the heat exchanger (1), in the first operating position, to the cooling zone duct (4), and in the second position, to a conduit short-circuiting the cooling zone duct (4) and connecting the heat exchanger (1) directly to the heating circuit. 4. Thermal recovery device according to any one of the preceding claims, characterized in that the heat exchanger (1) has a helical shape with several turns, each of the turns surrounding the exhaust line (3) or in that that the heat exchanger (1) has the shape of a cylindrical envelope obtained by a provision of the conduit (2) meandering along the exhaust line (3). 5. Thermal recovery device according to any one of the preceding claims, characterized in that the coolant comes from the engine cooling device and is directed to the heating circuit by the service box (9) of the heat transfer fluid, said fluid being preferentially water with, if necessary, additives to improve its properties. 6. Thermal recovery device according to any one of claims 1 to 4, characterized in that it has its own independent heat transfer fluid circuit and comprises at least one pump in this circuit for effecting the flow of fluid. 7. Thermal recovery device according to any one of the preceding claims, characterized in that the heat shield has an aluminum foil with, if necessary, a layer of heat-insulating fibers. 8. Thermal recovery device according to any one of the preceding claims, characterized in that the heat exchanger (1) extends in the heat shield only on a portion thereof. 9. Thermal recovery device according to any one of the preceding claims, characterized in that the heat exchanger (1) is shaped not to come into direct physical contact with the exhaust line (3) and / or the heat shield and in that the exhaust line (3) comprises fixing means for fixing the heat exchanger (1) and / or the heat shield to the vehicle body, or that one of these two elements comprises fastening means for fixing it to the vehicle body, the other element having fastening means for securing it with the first element. 10. Thermal recovery device according to any one of claims 1 to 8, characterized in that the exhaust line (3) is a double-walled line, the heat exchanger (1) and the heat shield being housed between these two walls of said line (3). 11. Motor vehicle, characterized in that it comprises a thermal recovery device according to any one of claims 1 to 10.