JP2002332920A - Exhaust heat exchanging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent cooling water from locally boiling at a corresponding part of a cooling water passage to the inlet side of an exhaust passage. SOLUTION: A finless range α where fins 111 are not provided is provided close to an exhaust inlet 110a. Heat exchange between EGR gas and cooling water is thus restricted close to the exhaust inlet 110a at least, and EGR gas is roughly uniformly distributed roughly along the whole range of the exhaust passage 110. Cooling water is thus prevented from locally boiling. Heat conductivity as the whole body of an EGR cooler 100 is improved, and heat exchange can be efficiently conducted in the whole body of the EGR cooler 100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust heat exchanger for performing heat exchange between exhaust gas generated by combustion and a cooling fluid such as water, and cools exhaust gas for an EGR (exhaust gas recirculation device). This is effective when applied to an EGR gas heat exchanger (hereinafter, referred to as an EGR cooler).

[0002]

2. Description of the Related Art FIG.
Is the exhaust passage 1 of the EGR cooler studied by the inventors.
FIG. 10 is a view showing a fin (in this example, an offset type in this example) for increasing a heat transfer area with exhaust gas in an exhaust passage (exhaust tube) in order to promote heat exchange between exhaust gas and cooling water. Fins) 111 are provided.

Incidentally, in general, a gas (compressible fluid) has a smaller heat transfer coefficient than a non-compressible fluid such as water (see heat transfer engineering (published by the University of Tokyo), etc.). Is desirably provided in the exhaust passage.

However, in the above-mentioned prototype, a portion of the cooling water passage corresponding to the inlet side of the exhaust passage is provided.
The cooling water boils locally, causing thermal damage to the member (cooling water tube or exhaust tube) that separates the exhaust passage and the cooling water passage at the local portion, and the internal pressure suddenly rises instantaneously Therefore, the durability of the EGR cooler may be deteriorated.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention to prevent the cooling water from being locally boiled in a portion of the cooling water passage corresponding to the inlet side of the exhaust passage.

[0006]

In order to achieve the above object, according to the present invention, an exhaust passage (110) through which exhaust flows and a fluid passage (120) through which fluid flows are provided. And a fin (111) disposed in the exhaust passage (110) for promoting heat exchange between the exhaust gas and the fluid. The fin (111) is provided near the exhaust inlet (110a) of the exhaust passage (110). 111) is not provided, and a finless region (α) is provided.

As a result, at least the exhaust inlet (110)
a) Exhaust inlet (110a) in which local boiling easily occurs because heat exchange between the exhaust and the fluid is suppressed in the vicinity.
Boiling of cooling water in the vicinity can be prevented.

According to the second aspect of the present invention, the exhaust passage (110) through which the exhaust flows, the fluid passage (120) through which the fluid flows in opposition to the exhaust flow, and the exhaust passage (11).
0), and a fin (111) for promoting heat exchange between the exhaust gas and the fluid. A fin (111) is provided near the exhaust inlet (110a) of the exhaust passage (110). The finless region (α) that is not provided is provided.

Thus, at least the exhaust inlet (110)
a) In the vicinity, since heat exchange between the exhaust gas and the fluid is suppressed, the exhaust inlet (110a) where local boiling easily occurs.
Boiling of cooling water in the vicinity can be prevented.

According to a third aspect of the present invention, there is provided an exhaust heat exchange apparatus for exchanging heat between an exhaust gas discharged from a heat engine and a fluid, comprising: an exhaust passage (110) through which the exhaust gas flows; Fluid passage (120) through which fluid flows in the same direction as
And a fin (111) disposed in the exhaust passage (110) for promoting heat exchange between the exhaust gas and the fluid. The fin (111) is provided near the exhaust inlet (110a) of the exhaust passage (110). 111) is not provided, and a finless region (α) is provided.

Thus, at least the exhaust inlet (110)
a) Exhaust inlet (110a) in which local boiling easily occurs because heat exchange between the exhaust and the fluid is suppressed in the vicinity.
Boiling of cooling water in the vicinity can be prevented.

It is to be noted that the finless region (α) is defined in claim 4.
In the exhaust passage (110), it is desirable to provide it along the outer edge (110c) near the exhaust inlet (110a).

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
An exhaust heat exchanger according to the present invention is applied to an EGR gas cooling device for a diesel engine (internal combustion engine),
FIG. 1 is a schematic diagram of an EGR (exhaust gas recirculation device) using an EGR gas cooling device (EGR cooler) 100 according to the present embodiment.

In FIG. 1, reference numeral 200 denotes a diesel engine (hereinafter abbreviated as engine), and 210 denotes an engine 20.
This is an exhaust recirculation pipe that recirculates a part of the exhaust gas discharged from the exhaust pipe to the intake side of the engine 200.

A reference numeral 220 is provided in the exhaust gas recirculation pipe 210 in the middle of the exhaust gas flow.
It is a well-known EGR valve for adjusting a GR gas amount.
The R cooler 100 is disposed between the exhaust side of the engine 200 and the EGR valve 220 to exchange heat between EGR gas and engine cooling water (hereinafter, abbreviated as cooling water).
Cool the GR gas.

Next, the structure of the EGR cooler 100 will be described.

FIG. 2 is a front view of the EGR cooler 100, FIG. 3 is a side view of the EGR cooler 100, and FIG. 4 is a sectional view taken along line AA of FIG.

3 and 4, reference numeral 110 denotes an exhaust passage through which EGR gas flows, and 120 denotes a cooling water (fluid) passage through which cooling water (fluid) flows. Here, as shown in FIG. 4, the cooling water passage 120 is formed by laminating two laminated plates (partition members) 131 and 132 formed into a predetermined shape in a thickness direction (vertical direction on the paper). The EGR gas and the cooling water are heat-exchanged by alternately laminating the laminated plates 131 and 132 and the inner fins (hereinafter, abbreviated as fins) 111 that constitute this set. The heat exchange core 130 is configured.

The fins 111 are provided in the exhaust passage 110 to increase the heat transfer area with the EGR gas. In this embodiment, as shown in FIG. This is a so-called offset fin in which plate-like segments 111a parallel to the direction (vertical direction in FIG. 4) are arranged in a staggered manner with respect to the exhaust passage 110.

Incidentally, as described above, it is desirable that the segment 111a be substantially parallel to the minor diameter direction of the exhaust passage 110. However, the actual fins 111 may have a draft angle of a roller or a press molding machine due to manufacturing problems. Therefore, being parallel to the minor axis direction of the exhaust passage 110 does not mean that the exhaust path 110 is completely parallel to the minor axis direction, but includes a gradient of a draft angle. That is the meaning.

The exhaust passage 110 has an exhaust inlet 110a.
A finless area α where no fin 111 is provided is provided in the vicinity, and the finless area α is provided along an outer edge 110c of the exhaust passage 110 near the exhaust inlet 110a.

The fins 111 are not provided in the vicinity of a vertical cooling water passage 120a, which will be described later, but this is for avoiding interference with the vertical cooling water passage 120a.
This is a region different from the finless region α described in this specification.

Incidentally, in FIG. 5, 130a is the cooling water passage 1.
The projection 130a protrudes toward the side 20. The projection 130a secures the distance between the laminated plates 131 and 132 (the height (the dimension in the minor diameter direction) of the cooling water passage 120).

In FIG. 4, reference numeral 140 denotes a heat exchange core 130.
Is a box-shaped core tank that accommodates the heat exchange cores 141 formed in the core tank 140. Here, the core cap 141 is joined to (fitted into) the core tank 140 so as to contact the inner wall of the core tank 140.

For this reason, the exhaust passage 110 is constituted by a space defined by the laminated plates 131 and 132 and the core tank 140 which constitute the cooling water passage 120, so that the exhaust gas flows around the cooling water passage 120 and the exhaust passage As well as the configuration of the exhaust passage 110, the cross section of the exhaust passage 110 (a surface substantially perpendicular to the EGR gas flow) also becomes substantially flat.

In this embodiment, the laminated plate 13
1, 132, core tank 140 and core cap 141
Are made of stainless steel with excellent corrosion resistance.
132, 140, and 141 are brazed and joined with a Ni-based brazing material.

In FIGS. 2 and 3, reference numeral 151 denotes an inlet-side connecting pipe through which the cooling water flows into the cooling water passage 120, and 152 denotes a flow through which the cooling water having undergone heat exchange in the EGR cooler 100 flows out. As shown in FIG. 3, each of the cooling water passages 120 is a connection pipe 151,
At a position corresponding to 52, the cooling water is communicated with a vertical cooling water passage 120a extending in the short diameter direction (vertical direction in FIG. 3).

In this embodiment, the cooling water passage 120
a and the EGR in the exhaust passage 110a.
The inlet connection pipe 151 is provided on the exhaust outlet 110a side, and the outlet connection pipe 152 is provided on the exhaust outlet 110b side so that the gas flow is in the same direction (parallel flow).

Next, the features (effects) of this embodiment will be described.

According to the present embodiment, the finless area α in which the fin 111 is not provided is provided in the vicinity of the exhaust inlet 110a.
In the vicinity of a, the heat exchange between the EGR gas and the cooling water is suppressed, so that the exhaust inlet 110 where local boiling easily occurs.
Boiling of the cooling water in the vicinity of a can be prevented.

In the prototype shown in FIG. 7, the fins 111 are provided over substantially the entire area of the exhaust passage 110, and the fins 111 (segments 111a) flow into the exhaust passage 110 from the exhaust inlet 110a due to the presence of the fins 111 (segments 111a). E
The cross section of the exhaust passage 110 (E
It is difficult to uniformly distribute the gas in substantially the entire length direction (vertical direction in FIG. 7) of the GR gas flow (the cross section substantially perpendicular to the flow direction), that is, substantially the entire exhaust passage 110.

On the other hand, in the vicinity of the exhaust inlet 110a, the finless area α where no fin 111 is provided is provided.
Is provided, the finless region α functions as a distribution space for distributing the EGR gas flowing into the exhaust passage 110 from the exhaust inlet 110 a to substantially the entire region of the exhaust passage 110.

Therefore, it is possible to prevent the high-temperature EGR gas from being intensively circulated to a specific portion, so that the EG
The R gas can be distributed substantially uniformly over substantially the entire area of the exhaust passage 110, and the cooling water can be prevented from boiling locally.

As a result, the heat transfer coefficient of the entire EGR cooler 100 is improved, and the entire EGR cooler 100 can efficiently exchange heat. 1
00 can be prevented from being thermally damaged locally.

According to examinations conducted by the inventors, the EGR cooler 100 according to the present embodiment has a temperature efficiency improved by about 8% and a pressure loss (passage resistance) as compared with the prototype shown in FIG. Was reduced by about 4%. The temperature efficiency is (inlet gas temperature−outlet gas temperature) / (inlet gas temperature−
(Inlet water temperature).

Since the flow of the cooling water in the cooling water passage 120a and the flow of the EGR gas in the exhaust passage 110a are in the same direction (parallel flow), at the exhaust outlet 110a where the EGR gas temperature is the highest, Since the cooling water temperature is the lowest, it is possible to reliably prevent the cooling water from boiling locally.

(Second Embodiment) The above-described embodiment (FIG. 5)
Then, the finless region α is located near the vertical cooling water passage 120a.
However, in this embodiment, as shown in FIG.
The finless region α is provided near the vertical cooling water passage 120a.

Thus, the EGR gas can be distributed substantially uniformly also in the vicinity (on the downstream side) of the vertical cooling water passage 120a, so that the heat exchange efficiency of the EGR cooler 100 is improved while the EGR cooler 100 is Local thermal damage can be prevented beforehand.

(Other Embodiments) In the above-described embodiment, the exhaust heat exchange device according to the present invention is applied to the EGR cooler 100. However, the heat exchange device is disposed in the muffler and recovers the heat energy of the exhaust gas. It may be applied to other heat exchangers such as a heat exchanger.

Further, in the above-described embodiment, the cooling water flow and the EGR gas flow are parallel flows. However, the present embodiment is not limited to this. Good.

The connection direction of the connection pipes 151 and 152 is not limited to the direction shown in the above-described embodiment (FIG. 3), but may be, for example, the direction perpendicular to the plane of FIG.

The shape of the filletless region α is shown in FIG.
The shape is not limited to the shape shown in FIG. 6, and for example, when the vertical cooling water passage 120a is substantially at the center in the major axis direction (vertical direction on the paper surface) in FIGS. And a symmetrical shape.

[Brief description of the drawings]

FIG. 1 is a schematic view of an EGR.

FIG. 2 is a front view of the EGR cooler according to the embodiment of the present invention.

FIG. 3 is a side view of the EGR cooler according to the embodiment of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a front view showing an exhaust passage (exhaust tube) in the EGR cooler according to the first embodiment of the present invention.

FIG. 6 is a front view showing an exhaust passage (exhaust tube) in an EGR cooler according to a second embodiment of the present invention.

FIG. 7 is a front view showing an exhaust passage (exhaust tube) in the EGR cooler according to the study of the prototype.

[Explanation of symbols]

110: exhaust passage (exhaust tube), 111: fin,
110a: exhaust inlet, α: finless area.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G062 ED08 3L103 AA27 BB39 CC02 CC27 DD15 DD34 DD62

Claims (4)

[Claims] An exhaust heat exchange device for exchanging heat between an exhaust gas discharged from a heat engine and a fluid, comprising: an exhaust passage (110) through which the exhaust gas flows; and a fluid passage (120) through which the fluid flows. And fins (111) disposed in the exhaust passage (110) for promoting heat exchange between the exhaust gas and the fluid. Near the exhaust inlet (110a) of the exhaust passage (110), An exhaust heat exchanger comprising a finless region (α) in which the fins (111) are not provided. 2. An exhaust heat exchanging device for exchanging heat between an exhaust gas discharged from a heat engine and a fluid, comprising: an exhaust passage (110) through which the exhaust gas flows; A fluid passage (120) through which a fluid flows; and a fin (111) disposed in the exhaust passage (110) for promoting heat exchange between the exhaust and the fluid. An exhaust heat exchange device, wherein a finless region (α) in which the fins (111) are not provided is provided near the exhaust inlet (110a). 3. An exhaust heat exchange device for exchanging heat between an exhaust gas discharged from a heat engine and a fluid, comprising: an exhaust passageway (110) through which the exhaust gas flows; The flowing fluid passage (12
0), and fins (111) disposed in the exhaust passage (110) for promoting heat exchange between the exhaust gas and the fluid, near the exhaust inlet (110a) of the exhaust passage (110). A finless region (α) in which the fins (111) are not provided is provided. 4. The finless region (α) is provided along an outer edge (110c) of the exhaust passage (110) near the exhaust inlet (110a). 3. The exhaust heat exchange device according to any one of 3.