JP2006118425A - Hood for egr gas cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hood structure body having a bend structure connected to an inlet side of an EGR gas cooling device and introducing EGR gas into the EGR gas cooling device while keeping uniform flow velocity distribution. <P>SOLUTION: This hood for EGR gas cooling device having the bend structure connected to the EGR gas cooling device and introducing high temperature EGR gas to the EGR gas cooling device is provided with a rough surface part having surface roughness for disturbing flow of gas on an inner surface in a larger curvature radius side of the bend part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bonnet structure in an EGR gas cooling device, and more specifically, is connected to an EGR gas introduction side in a heat exchange type EGR gas cooling device, and a high temperature EGR gas as a cooling medium is supplied to the EGR gas cooling device. The present invention relates to a bonnet for an EGR gas cooling device having a vent structure of various angles for introduction with a uniform flow velocity distribution.

  A method of taking a part of the exhaust gas from the exhaust system of the diesel engine, returning it to the intake system of the engine again, and adding it to the air-fuel mixture is called EGR (Exhaust Gas Recirculation). Many effects such as suppression of generation, reduction of pump loss, reduction of heat dissipation loss to coolant due to lowering of combustion gas temperature, increase of specific heat ratio due to change of working gas amount and composition, and improvement of cycle efficiency associated with it Therefore, it is widely adopted as an effective method for purifying exhaust gas from diesel engines and improving thermal efficiency.

However, when the temperature of the EGR gas rises and the amount of EGR gas increases, the durability of the EGR valve deteriorates due to the thermal action, and there is a possibility that the EGR valve will be damaged at an early stage. There is a need for a structure, and as the intake air temperature rises, the charging efficiency is lowered and the fuel consumption is reduced. In order to avoid such a situation, a device for cooling EGR gas with engine coolant, car air-conditioner refrigerant or cooling air is used, and in particular, gas-liquid that cools EGR gas, which is a gas, with engine coolant. Many heat exchange type EGR gas cooling devices have been proposed. For example, a double pipe type in which an outer pipe through which a liquid is passed is disposed outside an inner pipe through which a gas passes, and a metal corrugated plate is inserted as a fin in the inner pipe in an exchanger for exchanging heat between the gas and the liquid. A heat exchanger (see, for example, Patent Document 1), an inner pipe for circulating a medium to be cooled inside, an outer pipe provided so as to surround and surround the outer circumference of the inner pipe, and an inside of the inner pipe A double-pipe heat exchanger (for example, refer to Patent Document 2) composed of a radiating fin having a thermal stress relaxation function, an inner pipe for circulating a medium to be cooled, and an outer periphery of the inner pipe A double-pipe heat exchanger (for example, see Patent Document 3) composed of an outer tube provided so as to surround and be separated and a cross fin disposed inside the inner tube has been proposed. Yes.
Japanese Patent Laid-Open No. 11-23181 (pages 1-6, FIGS. 1-2) JP 2000-1111277 A (pages 1 to 12, FIGS. 1 to 12) JP 2003-21478 A (pages 1-8, FIGS. 1-7)

  In each of the prior arts described above, in the case of the double-tube type EGR gas cooling device disclosed in Patent Documents 1 to 3, the corrugated fins and the cross fins are provided so as to trickle the gas flow and make contact with the fins. In terms of increasing the area, although some results are expected, the inner surface of the pipe constituting the EGR gas flow path has a smooth inner peripheral surface over the entire length. In many cases, the heat transfer near the center of the pipe becomes insufficient, and the gas flow flows straight along the EGR gas pipe, so that the turbulence of the gas flow becomes insufficient and the boundary layer of the heat transfer surface is sufficient. There was a problem that the heat transfer performance was slightly insufficient without being thinned.

  By the way, an EGR gas cooling device for improving exhaust gas recirculation (EGR) efficiency of a diesel engine is installed in a limited space such as an engine room of an automobile equipped with a diesel engine. In general, a bonnet having a substantially right-angled vent structure is used. FIG. 4 exemplifies the EGR gas cooling device and the right angle vent structure. The bonnet 12-1 and the bonnet 12-2 of the right angle vent structure on the upstream side and the downstream side of the EGR gas cooling device 10 respectively correspond to the EGR gas. With respect to the tube plates 15-1 and 15-2 of the cooling device 10, the EGR gas inlet g1 and the outlet g2 are formed with curved surfaces (vent portions) that change to 90 °, and one end thereof is connected to the shell 11. In addition, high-temperature EGR gas is introduced into the individual heat transfer tubes 13-1 of the heat transfer tube array 13 that is built in the shell 11 and constitutes the cooler body. In this case, the bent portion of the bonnets 12-1 and 12-2 having a large radius of curvature is the bent portion having the larger radius of curvature, and the bent portion having the smaller radius of curvature is the bent portion having the smaller radius of curvature. Called.

In the EGR gas cooling apparatus having the above-described configuration, the high-temperature EGR gas introduced from the EGR gas inlet g1 is introduced into the bonnet 12-1 having a right-angled vent portion, and at the same time, the radius of curvature of the bonnet 12-1 is large. Advancing along the inner surface of the radial side vent portion 16 without receiving a pressure loss of the fluid, entering the cooling device body 10 constituted by the heat transfer tube group 13 and the like while maintaining a fast flow velocity distribution, Heat is exchanged with the cooling water that flows in an orthogonal state with respect to the heat transfer tube row group 13, and is discharged from the EGR gas outlet g2 provided in the downstream bonnet 12-2 and circulated. At this time, the high-temperature EGR gas introduced from the EGR gas inlet g1 has a flow velocity along the inner surface of the bent portion 16 on the large radius side of the bent radius portion of the bonnet 12-1, as shown in FIG. Proceeding early, the flow velocity becomes extremely slow on the inner surface of the bent portion 17 having a small radius of curvature. Such a deviation in the flow rate distribution of the EGR gas is generated without being corrected by its inertia once it occurs as long as there is no change in the conditions. Therefore, in the EGR cooling device in FIG. Since an excessive amount of EGR gas flows through the heat transfer tube array 13 on the upper side), it is impossible to cool to a desired temperature range, while the heat transfer tube array on the smaller radius of curvature side (lower in the figure). In the group 13, since the EGR gas flow rate is lower than the design value, the cooling of the EGR gas proceeds, but the predetermined flow rate is insufficient, and as a result, the exchange heat quantity is reduced. As described above, due to the bonnet having the vent structure of various angles, the distribution of the high temperature EGR gas introduced into the EGR gas cooling device is not uniform, and the flow velocity is unevenly distributed, resulting in the heat exchange efficiency. There remains an unresolved issue of significantly lowering the This tendency becomes more prominent as the vent angle increases.
The present invention is intended to solve such a problem, and in spite of its simple structure, various angles can be used to distribute and introduce EGR gas to the EGR gas cooling device evenly. A bonnet for an EGR gas cooling device having a vent structure is provided.

  A bonnet for an EGR gas cooling device according to the present invention for solving the above-mentioned problems is connected to the EGR gas cooling device, and is a bonnet having vent structures of various angles for introducing high-temperature EGR gas into the EGR gas cooling device. An EGR gas characterized in that a rough surface portion provided with a surface roughness for inhibiting the flow of gas is provided on a part or the entire inner surface of the bent portion on the large radius side of curvature radius. The gist of the bonnet for the cooling device is as follows.

  Further, in the bonnet for the EGR gas cooling device according to the present invention, the rough surface portion of the inner surface on the curvature radius large diameter side of the vent portion is a press working or other mechanical working method for the portion or a chemical working method by etching or the like. It is characterized by comprising the unevenness | corrugation given by either.

  Furthermore, in the bonnet for an EGR gas cooling device according to the present invention, it is preferable that the rough surface portion of the inner surface on the large radius side of curvature of the vent portion is provided by an interior of a separate fin structure with respect to the portion. It is what.

  In the bonnet for an EGR gas cooling device according to the present invention, the fin structure is made of a plate material made of a metal thin plate, and is preferably formed by forming corrugations and irregularities on the plate material.

  The said fin structure in the said EGR gas cooling device which concerns on this invention makes it a preferable aspect to provide many protrusions in the plate board which consists of metal thin plates.

  In the bonnet for an EGR gas cooling device according to the present invention, the interior means to the inner radius side surface of the radius of curvature of the vent portion of the fin structure is appropriately selected from bonding, welding, brazing and other joining means, It is a preferred embodiment that they are joined together.

  According to the bonnet for an EGR gas cooling device according to the present invention, in the bonnet having a vent structure having various angles connected to the EGR gas inlet side of the EGR gas cooling device, the large radius side of the curvature radius in the vent portion of the bonnet By forming a surface roughness for inhibiting the gas flow, specifically, a rough surface portion having irregularities on the inner surface of the gas, the gas flow rate can be reduced at that portion, so that in the vent portion The flow velocity distribution can be made uniform. A fluid such as EGR gas has a property of flowing in a direction in which pressure loss is originally small, and once the flow path is determined, the fluid flows down in the same direction due to inertia unless the condition is changed. Therefore, also in the EGR gas cooling device, in the cooling device shown in FIG. 4, a large amount of EGR gas flows upward, and an excessive amount of gas flows with respect to the design value, so that it is not cooled to a predetermined temperature range. On the other hand, in the cooling device shown in FIG. 4, sufficient cooling proceeds because only a small amount of hot EGR gas flows downward in the cooling device shown in FIG. Since it is not satisfied, the heat of exchange is greatly reduced.

  As described above, the bonnet of the vent structure according to the present invention previously imparts surface roughness such as unevenness to the inner surface on the large radius side of the curvature radius of the vent portion where gas flows easily by the action of the uneven pressure distribution and centrifugal force. By providing a rough surface part, frictional resistance is generated in the flow of the fluid and the flow is obstructed. As a result, the EGR gas introduced into the EGR gas cooling device is evenly distributed and maintains a uniform flow velocity distribution. Therefore, the heat exchange performance of the EGR gas cooling device can be maximized and excellent cooling efficiency can be obtained. The bonnet for the EGR cooling device according to the present invention can be manufactured by extremely simple processing, and the obtained effect is remarkably excellent. Therefore, the EGR cooling device can be reduced in size and weight at low cost, and can save energy. A great contribution can also be expected in the field.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.
FIG. 1 is a side view schematically showing a bonnet having a right-angle vent structure according to an embodiment of the present invention, and a flow velocity distribution of EGR gas flowing through the bonnet, and FIG. 2 is a diagram showing another embodiment according to the present invention. FIG. 3 is a partially enlarged side view of a fin structure built in the inner surface on the large diameter side of a bonnet having a right-angle vent structure. FIG. 3 is a view showing a radius of curvature of a bonnet having a right-angle vent structure according to another embodiment of the present invention. It is a partially expanded side view of the fin structure housed on the inner surface on the large diameter side.
[Example]

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited thereto, and can be freely modified within the scope of the gist of the present invention, including the vent angle.

  As shown in FIG. 1, the bonnet 2 having a right-angled vent structure according to the first embodiment of the present invention is high and low by pressing only the inner surface of the bent portion 3 having a large radius of curvature R at the bent portion. A rough surface portion 3-2 having a surface roughness having unevenness 3-1 having a maximum difference of about 2.5 mm was formed. The bonnet 2 having a right-angled vent structure obtained in this way is connected to a multi-tube heat exchanger body to constitute an EGR cooling device as shown in FIG. 4 and incorporated into a gas flow path in the EGR gas cooling system. As a result of the cooling performance test, the high-temperature EGR gas that flowed into the bonnet 2 from the gas inlet G1 was formed on the inner surface of the bent portion 3 with a large radius of curvature, as shown in FIG. When the surface roughness of the rough surface portion 3-2 having 1 acts and the flowing gas tries to flow along the inner surface of the bent radius side 3 of the bent portion, a frictional resistance is caused. As a result, the flow rate and distribution of the EGR gas are made uniform, and are distributed evenly through many heat transfer tubes in the cooler body 1 so that the heat exchange to the cooling jacket on the outer periphery of the heat transfer tubes is performed. Effectively promoted, the bonnet on the exit side It was confirmed that the EGR gas discharged from the reactor was cooled to a predetermined temperature range.

  The manufacturing method of the bonnet 2 having a right-angled vent structure according to the present embodiment is not particularly limited, and is usually manufactured by a draw vent using a specific mold using a steel pipe as a raw material, or a compression vent, a hydraulic bulge, etc. The rough surface portion 3-2 due to the unevenness 3-1 is formed at the same time as pressing or hydraulic bulging. The bonnet 2 is connected to the cooler main body by welding in this example. However, a flange is provided on the cooler side of the bonnet, and the connection to the flange preliminarily attached to the cooler main body or brazing can be performed. Preferably employed. In addition, although the said rough surface part 3-2 in a present Example employ | adopted formation of the uneven | corrugated surface 3-1 by press work, or a hydraulic bulge, as a formation processing method of this rough surface part 3-2, it cuts mechanically. Further, it is possible to form the steel pipe material subjected to predetermined masking by etching by chemical means in a corrosive solution. On the other hand, in the case of a cast bonnet, the rough surface portion can be formed simultaneously with casting.

  Further, as a method of forming the uneven surface 3-1 shown in FIG. 1 in the bonnet having a right angle vent structure, as shown in FIG. 2, a separate corrugated fin 3a-1 made of a plate material made of a metal thin plate is welded or the like. A method of attaching by means can be used. As a result of incorporating the bonnet with the corrugated fins 3a-1 into the gas flow path in the EGR gas cooling system and subjecting it to the same cooling test as in Example 1, it is possible to obtain a cooling efficiency substantially equal to that in the Example. confirmed.

  Further, as a method of forming the rough surface portion 3-2 on the inner surface of the bent portion 3 with a large radius of curvature in the right-angle vent structure bonnet, the method shown in FIG. 3 can be employed. In this method, a separate plate plate 3b-2 made of a thin metal plate material provided with a large number of protruding fins 3b-1 on the inner surface of the bent portion 3b with a large radius of curvature in the bonnet is welded or the like. The bonnet according to the present example, in which the plate plate 3b-2 to which the protruding fins 3b-1 are attached is installed, is incorporated in the gas flow path in the EGR gas cooling system, and the same cooling test as in Example 1 is performed. As a result, it was confirmed that substantially the same cooling efficiency as in Example 1 was obtained.

  As is clear from the above embodiments, the bonnet for the EGR gas cooling device having vent structures of various angles according to the present invention has a vent portion in which the gas easily flows due to the pressure distribution in the flow and the centrifugal force. By providing a rough surface portion with surface roughness such as irregularities on the inner surface on the large radius side of the curvature radius, a frictional resistance is generated in the gas flow to inhibit the flow, and as a result, EGR gas Since the EGR gas introduced into the cooling device is distributed evenly and is introduced into the cooling device main body in a state of maintaining a uniform flow velocity distribution, the heat exchange performance of the EGR gas cooling device is maximized, Since excellent cooling efficiency can be obtained, it contributes greatly in terms of energy saving. Further, the bonnet for the EGR cooling device according to the present invention can be manufactured by extremely simple processing, and the obtained effect is remarkably excellent, so that the EGR cooling device can be reduced in size and weight at low cost. Therefore, it is expected to be widely adopted as a bonnet structure in the technical field.

It is a side view which shows typically the flow rate distribution of the EGR gas which flows through the bonnet of the right angle vent structure which concerns on one Example of this invention, and this bonnet. In another Example which concerns on this invention, it is a partially expanded side view of the fin structure internally equipped by the curvature radius large-diameter side inner surface of the bonnet of a right angle vent structure. FIG. 6 is a partially enlarged side view of a fin structure that is internally mounted on the inner surface on the large-diameter side of the radius of curvature of a bonnet having a right-angled vent structure in yet another embodiment according to the present invention. It is a side view which shows one Example of the conventional EGR gas cooling device made into the object of this invention, and a right angle vent structure. It is a side view which shows typically the flow rate distribution of the bonnet of the right angle vent structure in the EGR gas cooling device shown in FIG. 4, and the EGR gas which flows through the inside of the bonnet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10 EGR gas cooling device 2, 12-1, 12-2 Bonnet 3, 3a, 3b Curvature radius large diameter side vent part 3-1 Concavity and convexity 3-2 Rough surface part 3a-1 Corrugated fin 3b-1 Protruding fin 3b -2 plate plate 4 curvature radius small diameter side vent portion 5, 15-1, 15-2 tube plate 6 welded portion 7 flange portion 11 shell 13, heat transfer tube array 13-1 flat heat transfer tube 16 outer peripheral side vent portion 17 inner periphery Side vent part g1 EGR gas inlet g2 EGR gas outlet C1 Cooling water inlet C2 Cooling water outlet

Claims (6)

In a bonnet having a vent structure that is connected to an EGR gas cooling device and introduces high-temperature EGR gas into the EGR gas cooling device, a gas is formed on a part or the entire inner surface of the bent radius side of the bent portion. A bonnet for an EGR gas cooling device, wherein a rough surface portion provided with a surface roughness for inhibiting flow is provided. The rough surface portion of the inner surface on the large-diameter side of the curvature radius of the vent portion is configured by unevenness applied by any one of press processing, other mechanical processing methods, or chemical processing methods such as etching. The bonnet for an EGR gas cooling device according to claim 1. 2. The hood for an EGR gas cooling device according to claim 1, wherein the rough surface portion on the inner surface on the large radius side of the bent portion is provided by an interior of a separate fin structure for the portion. The hood for an EGR gas cooling device according to claim 3, wherein the fin structure is made of a plate material made of a metal thin plate, and is formed by forming corrugations and irregularities on the plate material. The hood for an EGR gas cooling apparatus according to claim 3, wherein the fin structure is configured by providing a plurality of protrusions on a plate plate made of a thin metal plate. The interior means for the inner radius side surface of the bent portion of the fin structure of the fin structure is appropriately selected from bonding, welding, brazing and other joining means, and is integrally joined. Item 6. The hood for an EGR gas cooling device according to any one of Items 3 to 5.

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