EP2795089B1 - Heat exchanger for gases, in particular for the exhaust gases of an engine - Google Patents

Description

The present invention relates to a heat exchanger for gas, in particular for the exhaust gas of an engine.

The invention relates in particular to the exhaust gas recirculation exchangers of an engine (EGRC).

BACKGROUND OF THE INVENTION

The main function of the EGR exchangers is to exchange the heat between the exhaust and the coolant for the purpose of cooling the gases.

At present, EGR heat exchangers are widely used in diesel applications to reduce emissions, as well as in petrol applications to reduce fuel consumption.

The market trend is to reduce the size of the engines and to install EGR heat exchangers, not only in high pressure (HP) applications, but also in low pressure (LP) applications. These two types of application have an impact on the design of the EGR heat exchangers. Vehicle manufacturers are demanding EGR heat exchangers with higher efficiencies, but at the same time, the space available for installing an exchanger and its components is getting smaller and more difficult to install. to integrate.

In addition, in many applications, the flow rate of coolant for cooling the exhaust gas tends to decrease despite the increase in efficiency of the exchanger.

The current configuration of the EGR exchangers on the market is a metal heat exchanger, usually made of stainless steel or aluminum.

Basically, there are two types of EGR heat exchanger: a first type consisting of a carcass inside which is disposed a bundle of parallel tubes for the passage of gases, the coolant circulating in the carcass around the tubes ; and the second type comprising a series of parallel plates which constitute the heat exchange surfaces, so that the Exhaust gas and coolant circulate between two plates, in alternating layers, and may include fins to improve heat exchange.

In the case of tube bundle heat exchangers, the junction between the tubes and the carcass can be of different types. Generally, the tubes are fixed at their ends between two support plates coupled to each end of the carcass, the two support plates having a plurality of orifices for the introduction of the respective tubes.

These support plates are in turn attached to connection means to the recirculation pipe, which may consist of a V-shaped connection or a peripheral flange connection or flange, according to the design of the recirculation pipe where is assembled the exchanger. The peripheral rim may be either assembled with a gas reservoir, such that the gas reservoir is an intermediate piece between the carcass and the rim, or assembled directly to the carcass.

In both types of EGR exchangers, most of the components are metallic, so they are mechanically assembled and then oven or arc welded to provide the required level of sealing for this application. .

One type of known exchanger comprises a tube bundle of substantially rectangular section distributed over two adjacent columns and several rows, the height of the tubes being less than their width. Said tube bundle is housed in a substantially rectangular carcass, with the inlet and the outlet of the gases located at opposite ends of the carcass.

This type of exchanger also comprises two pipes, respectively for the inlet and the outlet of the coolant, connected to the carcass. The coolant must circulate around the tubes and cool well especially the support plate located at the gas inlet, due to the higher temperature of this plate. In this case, it is necessary to ensure a good circulation of the coolant in the gas inlet zone in order to avoid the formation of low flow zones which would involve a local increase in the temperature of the coolant by exchange with the input gases at high temperature.

The distribution of the coolant in the carcass between the gas tubes depends on the size of the carcass and the position of the coolant pipes. In certain specific configurations, boiling problems associated with poor distribution of coolant near the gas inlet support plate occur. Therefore, the coolant distribution is good in the said area contiguous to the support plate In the case of the gas inlet, the problem of boiling due to the high temperature of the tubes in said zone will be overcome.

In a known configuration, the coolant inlet pipe is connected to one side of the carcass, near the bottom and the outlet of the gases, while the coolant outlet pipe is connected to the top of the carcass, in the center and near the gas inlet. This configuration thus allows a countercurrent circulation of the coolant. In this case, the coolant outlet pipe is located above the space separating the two columns of tubes, said space between the tubes being relatively small, which makes the exit of the coolant difficult.

It should be emphasized that when the exchanger is used with a parallel flow, that is, when the coolant inlet pipe is disposed near the gas inlet, said boiling problems occur. also.

In another known configuration with countercurrent circulation, the coolant inlet pipe is connected to the bottom of the carcass near the gas outlet, while the coolant outlet pipe is connected to one side. carcass, near the gas inlet. In this case, the coolant outlet pipe occupies several spaces between rows of tubes, because the height of the tubes is less than their width. The passage surface of the coolant is thus greater between the tubes to the outlet.

Therefore, in this latter configuration, the problem of boiling is improved, firstly because the flow of the coolant is greater in the exit zone, and secondly because its distribution between the tubes is more homogeneous. However, this configuration is not feasible in the case of certain arrangements and sizes of the engine space, where the orientation of the connection sleeve to the coolant outlet pipe is not satisfactory.

The document DE 10 2005 037 156 A1 discloses an EGR heat exchanger comprising a tube bundle according to the preamble of claim 1.

The document EP 1 795 850 A1 discloses an EGR heat exchanger comprising a series of parallel plates and a plate which improves the distribution of the coolant.

DESCRIPTION OF THE INVENTION

The purpose of the gas heat exchanger, in particular for the exhaust gas of an engine, of the present invention is to overcome the drawbacks of the exchangers known in the art, so as to provide a more homogeneous distribution. and effective coolant, especially in the gas entry zone where the temperature is higher, with the consequent decrease the problem of boiling, and so as to further allow a better fit between the connecting coupling of the vehicle manufacturer and the outlet pipe or coolant inlet.

The gas heat exchanger, in particular for the exhaust gas of an engine, of the present invention is of the type which comprises a bundle of tubes arranged inside a carcass defining an inlet and an outlet of the gas, said tubes being intended for the circulation of gases for heat exchange with a cooling liquid and said tubes being distributed in at least one column of several rows defining several spaces between the rows, and which comprises a pipe of inlet and a coolant outlet pipe connected to the carcass, said exchanger of the present invention being characterized in that it comprises a bypass channel integrated into the carcass capable of communicating the defined spaces between the rows of tubes located opposite said channel with one of the coolant pipes, so as to improve the distribution of the coolant.

Preferably, the height of the tubes is less than their width, and one of said coolant pipes is located opposite the widest side of the tubes.

Advantageously, one of said coolant pipes is disposed near the gas inlet, thereby improving the distribution of the coolant in the area near the gas inlet.

In this way, the bypass channel makes it possible respectively to obtain an outlet or a coolant inlet, depending on whether the circulation is countercurrent or in parallel, on one side of the carcass where the outlet flow passes through the defined space. between rows of tubes, and not the space opposite the widest side of the tubes as in the case of the state of the art.

Therefore, the coolant pipe located near the gas inlet can be disposed on any side of the carcass, no matter where the vehicle manufacturer's sleeve is for connecting the said liquid pipe. cooling.

This results in a channel for the passage of coolant whose trajectory can be adapted to the needs and configuration of the engine space.

Furthermore, said coolant pipe disposed near the gas inlet can be assembled on the carcass and at one end of the channel so that usual.

Preferably, the bypass channel is manufactured by a stamping process, and its configuration causes it to protrude to the outside of the carcass. According to the invention, the bypass channel is associated with a closure plate coupled to the carcass in the interior space facing said channel, said closure plate comprising at least one passing orifice intended to allow the controlled passage of the liquid. cooling between the inside of the carcass and the bypass channel.

Therefore, the coolant flows through the channel through one or more holes in the closure plate, the number or size of which can be varied to provide optimum coolant distribution according to the needs of the coolant manufacturer. vehicles.

According to a preferred embodiment, the inner closure plate comprises two lateral passage orifices.

According to another preferred embodiment, the inner closure plate comprises a set of lateral orifices each associated with a space located every two rows of tubes, and at least one upper orifice situated in front of the coolant outlet pipe. .

In addition, the bypass channel may have various configurations depending on the flow rate of the coolant and the characteristics of the engine environment.

In a preferred embodiment, the bypass channel includes a side port for connecting a second coolant outlet pipe.

In another preferred embodiment, two bypass channels are disposed respectively on opposite sides of the carcass.

In another preferred embodiment, the branch channel comprises a variable cross section along its entire length.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 est une vue en perspective d'un échangeur de chaleur connu dans l'état de la technique, qui illustre une configuration possible des tuyaux d'entrée et de sortie de liquide de refroidissement ;
• la figure 2 est une section longitudinale de l'échangeur de chaleur de la figure 1, qui illustre schématiquement les lignes de répartition du liquide de refroidissement ;
• la figure 3 est une vue de face partielle de l'échangeur de la figure 1, qui illustre le tuyau de sortie de liquide de refroidissement et sa position par rapport aux tubes de gaz ;
• la figure 4 est une vue schématique d'une section transversale du tuyau de sortie de liquide de refroidissement de l'échangeur de la figure 1, qui indique sa position au-dessus de l'espace entre deux colonnes de tubes ;
• la figure 5 est une vue en perspective partielle de l'échangeur de chaleur selon l'invention, qui illustre le canal estampé dans une paroi latérale de la carcasse ;
• la figure 6 est une vue en perspective de la plaque de fermeture intérieure de l'invention, selon un premier mode de réalisation ;
• la figure 7 est une vue en perspective partielle de l'échangeur de chaleur selon l'invention, avec la plaque de fermeture intérieure assemblée sur le canal estampé ;
• la figure 8 est une section transversale de l'échangeur de l'invention de la figure 7, qui illustre la répartition du liquide de refroidissement à travers la plaque de fermeture et le canal vers le tuyau de sortie correspondant ;
• la figure 9 est une vue en perspective partielle de l'échangeur de chaleur selon l'invention, qui illustre un deuxième mode de réalisation de la plaque de fermeture intérieure ;
• la figure 10 est une section transversale de l'échangeur de l'invention de la figure 9, qui illustre la répartition du liquide de refroidissement à travers la plaque de fermeture et le canal vers le tuyau de sortie correspondant ; et
• les figures 11 à 13 sont des sections transversales de l'échangeur de chaleur de l'invention, qui illustrent respectivement des modes de réalisation du canal de dérivation.

In order to facilitate the description of what has been explained above, drawings are enclosed in which are shown, in schematic form and only by way of non-limiting example, practical examples of embodiment of the gas heat exchanger, in particular for the exhaust gas of an engine, of the present invention. In these drawings:

• the figure 1 is a perspective view of a heat exchanger known in the state of the art, which illustrates a possible configuration of the coolant inlet and outlet pipes;
• the figure 2 is a longitudinal section of the heat exchanger of the figure 1 which schematically illustrates the distribution lines of the coolant;
• the figure 3 is a partial front view of the exchanger of the figure 1 which illustrates the coolant outlet pipe and its position relative to the gas tubes;
• the figure 4 is a schematic view of a cross-section of the coolant outlet pipe of the heat exchanger of the figure 1 , which indicates its position above the space between two columns of tubes;
• the figure 5 is a partial perspective view of the heat exchanger according to the invention, which illustrates the stamped channel in a side wall of the carcass;
• the figure 6 is a perspective view of the inner closure plate of the invention, according to a first embodiment;
• the figure 7 is a partial perspective view of the heat exchanger according to the invention, with the inner closure plate assembled on the stamped channel;
• the figure 8 is a cross section of the exchanger of the invention of the figure 7 , which illustrates the distribution of the coolant through the closure plate and the channel to the corresponding outlet pipe;
• the figure 9 is a partial perspective view of the heat exchanger according to the invention, which illustrates a second embodiment of the inner closure plate;
• the figure 10 is a cross section of the exchanger of the invention of the figure 9 , which illustrates the distribution of the coolant through the closure plate and the channel to the corresponding outlet pipe; and
• the Figures 11 to 13 are cross sections of the heat exchanger of the invention, which respectively illustrate embodiments of the bypass channel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The Figures 1 to 4 illustrate a type of heat exchanger 1 'known in the state of the art, which comprises a bundle of tubes 2 disposed inside a carcass 3 defining an inlet 4 and an outlet 5 of the gases, said tubes 2 being intended for the circulation of gases for heat exchange with a coolant. The inlet flow 4 and outlet 5 of the gases is illustrated by means of respective arrows, as shown in FIG. figure 2 . In addition, the tubes 2 are fixed at their ends between two support plates 6, 6 'connected to each end of the carcass 3.

In this case, the tubes 2 are of substantially rectangular section and are distributed over two contiguous columns and several rows. Said tubes 2 thus define a space 7 between the columns and several spaces 8 between the rows, the height of said tubes 2 being less than their width. The carcass 3 has a quadrangular section.

The exchanger 1 'also comprises an inlet pipe 9 and a coolant outlet pipe 10 connected to the carcass 3. The inlet and outlet flow of the cooling liquid is represented by means of respective arrows, as shown in FIG. show it Figures 1 and 2 . In this case it is a circulation of the countercurrent coolant. The coolant inlet pipe 9 is connected to a side 3b of the carcass 3, close to the underside 3c and the outlet 5 of the gases, while the outlet pipe 10 of the coolant is connected to the top 3a. of the carcass 3, in the center and near the inlet 4 of the gases.

As shown by Figures 3 and 4 , the coolant outlet pipe 10 is located above the space 7 which separates the two columns of tubes 2. However, said space 7 between two tubes 2 is relatively small, which makes the exit of the liquid difficult. cooling. In this case, as shown by the curved lines on the figure 2 it is necessary to direct the coolant to the inlet zone 4 of the gases and with a high flow rate, because the temperature of the gases is high. The better the distribution of the coolant in said zone 4 contiguous to the support plate 6 of the gas inlet, the more the boiling problem due to the high temperature of the tubes 2 in said zone 4 will be controlled.

The Figures 5 to 13 refer to the heat exchanger 1 of the invention, whose reference numerals 2 to 10 coincide with those of the exchanger 1 'known previously described.

As shown by Figures 5 to 8 , the heat exchanger 1 of the invention further comprises a bypass channel 11 integrated in a side 3b of the carcass 3 near the inlet 4 of the gases, said bypass channel 11 being capable of communicating the lateral space 8 defined between rows of tubes 2 located opposite said channel 11 with the outlet pipe 10 of coolant disposed on the top 3a of the carcass 3. This structural arrangement significantly improves the distribution of coolant in the area near the inlet 4 of the gases.

The bypass channel 11 makes it possible to obtain a coolant outlet in a side 3b of the carcass 3, where said outlet flow passes through the spaces 8 defined between rows of tubes 2, and not the space 7 defined between columns as in the case of the state of the art, and no matter where is the sleeve of the vehicle manufacturer for the connection of said outlet pipe 10 coolant.

In this way, a channel 11 is obtained for the passage of the coolant whose trajectory can be adapted to the needs and configuration of the engine space.

In this case, the bypass channel 11 is manufactured by a stamping process, and its configuration makes it protrude towards the outside of the carcass 3, as shown by the figures 5 and 8 .

Furthermore, the outlet pipe 10 of coolant is assembled to the carcass 3 and to one end of the channel 11 in the usual way (see figure 8 ).

Similarly, the bypass channel 11 is associated with a closure plate 12 coupled to the carcass 3 in the interior space facing said channel 11, said closure plate 12 comprising at least one through hole 13 provided to allow the controlled passage of the cooling liquid from the interior of the carcass 3 to the bypass channel 11.

Therefore, the coolant enters the channel 11 through one or more orifices 13 in the closure plate 12, the number or size of which can be varied to obtain optimum distribution of the coolant as needed. from the vehicle manufacturer.

According to a first embodiment of the closure plate 12 illustrated on the Figures 6 to 8 said closure plate 12 comprises two lateral passage orifices 13. On the figure 8 the coolant outlet is shown by means of two arrows, respectively through the orifices 13 to the bypass channel 11 and then to the outlet pipe 10.

According to a second embodiment of the closure plate 12 illustrated on the Figures 9 and 10 , said closure plate 12 comprises a set of small diameter lateral orifices 13 each associated with a space 8 located every two rows of tubes 2, and a plurality of upper orifices 13a situated opposite the outlet pipe 10 of coolant. Similarly, on the figure 10 the coolant outlet is shown by means of two arrows, respectively through the openings 13, 13a to the bypass channel 11, and then to the outlet pipe 10.

It should be noted that until now, the heat exchanger has been described with a circulation of countercurrent coolant, but it is obvious that the circulation can also be parallel, that is to say with the coolant inlet on the side near the gas inlet.

On the other hand, although there is shown a bundle of tubes with two columns and several rows, there may be other embodiments, for example with a single column and several rows.

Likewise, other types of geometries may be used for the bypass channel 11, depending on the flow rate of the coolant and the characteristics of the engine environment. Three embodiments are described below.

According to a first embodiment illustrated on the figure 11 , the bypass channel 11 comprises a lateral orifice provided for connecting a second outlet pipe 10a of coolant.

According to a second embodiment illustrated on the figure 12 two bypass channels 11, 11a are used with their respective closing plates 12, 12a respectively disposed on opposite sides 3b of the carcass 3.

According to a third embodiment illustrated on the figure 13 , the bypass channel 11 comprises a variable cross section over its entire length.

Claims (9)

1. Heat exchanger (1) for gas, particularly for exhaust gases from an engine, comprising a core bundle of tubes (2) arranged inside a shell (3) defining a gas inlet (4) and outlet (5), the said tubes (2) being intended for the circulation of the gases with a view to an exchange of heat with a cooling liquid and the said tubes (2) being distributed in at least one column of several rows defining several spaces (8) between the rows, and comprising an inlet pipe (9) and an outlet pipe (10) for cooling liquid which are connected to the shell (3), the said exchanger (1) comprising a bypass duct (11) incorporated into the shell (3) and capable of making the spaces (8) defined between the rows of tubes (2) situated facing the said duct (11) communicate with one of the cooling liquid pipes (10), so as to improve the distribution of the cooling liquid, the exchanger comprising at least one through-orifice (13) intended to allow controlled passage of the cooling liquid between the inside of the shell (3) and the bypass duct (11),
   characterized in that the said duct is associated with a shut-off plate (12) coupled to the shell (3) in the interior space situated facing the said duct (11), the said shut-off plate (12) comprising the said through-orifice (13).
2. Exchanger (1) according to Claim 1, in which the height of the tubes (2) is less than the width thereof, and in which one of the said cooling liquid pipes (10) is situated facing the widest side of the tubes (2).
3. Exchanger (1) according to Claim 1 or 2, in which one of the said cooling liquid pipes (10) is arranged near the gas inlet (4), thus improving the distribution of the cooling liquid in the zone situated near the gas inlet (4).
4. Exchanger (1) according to Claim 1, in which the bypass duct (11) is produced by a stamping process, and its configuration means that it extends towards the external part of the shell (3).
5. Exchanger (1) according to Claim 1, in which the interior shut-off plate (12) comprises two lateral through-orifices (13).
6. Exchanger (1) according to Claim 1, in which the interior shut-off plate (12) comprises a collection of lateral orifices (13) each associated with one space (8) situated every two rows of tubes (2), and at least an upper orifice (13a) situated facing the cooling liquid pipe (10) situated near the gas inlet (4).
7. Exchanger (1) according to Claim 1, in which the bypass duct (11) comprises a lateral orifice intended for connecting a second outlet pipe (10a) for cooling liquid.
8. Exchanger (1) according to Claim 1, which comprises two bypass ducts (11, 11a) arranged respectively on the opposite sides (3b) of the shell (3) .
9. Exchanger (1) according to Claim 1, in which the bypass duct (11) has a cross section that varies along its entire length.

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