JPH11193992A - Multitubular egr gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make uniform the flow rate of an EGR gas and to improve cooling performance by forming a group of heat transfer pipes by making smaller the pipe diameter of a group of heat transfer pipes at the high-speed inflow part of the EGR (exhaust recirculation) gas than that of the low-speed inflow part of the EGR gas. SOLUTION: A suction port 5 and an exhaust port 5' of a cooling medium such as a cooling liquid of an engine are provided near the both edge parts of a drum pipe 1, and are fixed between partitions 3 of both side edge parts inside the drum pipe 1, which forming a row with the both edge parts of a group of heat transfer pipes 2 by welding or the like. Further, a bonnet member 4 with an inflow port 4' and an outflow port 4" is fixed to the outside of both side edge parts of the drum pipe 1 similarly by welding or the like. Then, with the arrangement of a group of heat transfer pipes 2, the pipe diameter of a group of heat transfer pipes 2 near a central part where the EGR gas flows in speedily is set smaller than that of the low-speed inflow part of the EGR gas when an EGR pipe is connected and fixed to the bonnet member 4 on a straight line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a cooling device for cooling an EGR gas by a cooling liquid for an engine, a refrigerant for an intercooler, a refrigerant for a car air conditioner, or cooling air.

[0002]

2. Description of the Related Art A part of exhaust gas is taken out of an exhaust system,
To return to the intake system of the engine and add it to the mixture,
EGR (Exhaust Gas Recircula)
Tion: exhaust gas recirculation). EGR suppresses the generation of nitrogen oxides, reduces pump loss, reduces heat dissipation loss to the cooling medium due to a decrease in the temperature of combustion gas, and increases the specific heat ratio due to changes in the working gas amount and composition, and the cycle efficiency associated therewith. It is said to be effective in improving the thermal efficiency of the engine because many effects such as improvement of the engine can be obtained. However, in general, when the temperature of the EGR gas rises, the fuel efficiency is reduced due to the rise of the intake air temperature, and the heat effect thereof deteriorates the durability of the EGR valve and causes early breakage. E depending on the cooling medium by the heat exchanger
An apparatus for cooling the GR gas is used.

As a cooling device in this case, for example, as shown in FIG. 5, a group of heat transfer tubes (12) arranged and fixed in a honeycomb shape inside a body tube of the device is composed of heat transfer tubes having the same diameter.
Further, the heat transfer tube (12) group is formed with substantially the same density (that is, the heat transfer tubes are spaced at substantially the same pitch or the number of heat transfer tubes in a unit area is fixed). (13) is a partition.

[0004]

However, in the prior art, the arrangement of a group of heat transfer tubes (12) having the same diameter and the same density causes the EGR gas flowing in the group of heat transfer tubes to have a high speed. Differences in flow rate and flow velocity between the inflow section and the low-speed inflow section were caused. That is, FIG.
As shown in (a), when the EGR pipe (17) on the inflow side of the EGR gas is connected to the bonnet member (16) in a straight line, it can be understood from the flow velocity distribution on the lines aa and bb. The flow velocity near the center just before the partition wall (13) is faster than the flow velocity near the outer part, while the EGR pipe (17) on the inflow side of the EGR gas is bent at a substantially right angle as shown in FIG. When connected to the bonnet member (16), the flow velocity near the outer side of the bent portion immediately before the partition wall (13) indicates the flow rate near the inner side of the bent portion as can be seen from the flow velocity distribution on the cc and dd lines. It will be faster than the flow velocity. On the other hand, the heat transfer per unit heat transfer area of the heat transfer tube is better when the flow rate of the EGR gas is faster, and when the heat transfer tube diameter is smaller, the number of installations increases and the heat transfer area increases. It has been known. Therefore, in particular, if there is a difference in the flow rate of the EGR gas in the inflow portion of the EGR gas, there is a tendency that there is a difference in the heat transfer effect in each of the heat transfer tubes and the cooling performance of the entire apparatus cannot be improved.

[0005] The present invention has been made in view of the above-mentioned problems of the prior art, and has been developed in advance in accordance with the EGR pipe shape.
By measuring the flow velocity of the GR gas at the inflow portion, the flow resistance near the high-speed EGR gas inflow portion is increased with respect to the flow of the EGR gas in the body tube, and the flow of the EGR gas is reduced by the heat transfer tube near the low-speed inflow portion. EG flowing through the heat transfer tube group as a whole by increasing the flow rate of EGR gas in
A multi-tube EGR that makes the flow rate of the R gas as uniform as possible, enhances the cooling performance of the entire apparatus by a smooth flow, and effectively exerts the cooling of the temperature of the EGR gas.
It is an object to provide a gas cooling device.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a heat transfer tube group in which the vicinity of both ends is arranged between partition walls at both ends of a body tube provided with a cooling medium inlet and a discharge outlet. An EGR gas cooling apparatus comprising: a bonnet member fixedly arranged in a row and further provided with mounting flange walls on both sides of the body tube and having an inlet and an outlet for EGR gas. The heat transfer tube group may be formed such that the diameter of the heat transfer tube group in the high-speed inflow portion of the EGR gas is smaller than that of the low-speed inflow portion of the EGR gas, and / or the arrangement density of the high-speed inflow portion is smaller than that of the low-speed inflow portion. Multi-tube E configured to be lower than array density
The gist is a GR gas cooling device, and the heat transfer tube group is
The diameter of the tube is gradually reduced from the low-speed inflow portion toward the high-speed inflow portion, and the arrangement density thereof is also gradually reduced.

According to the present invention, the heat transfer tube group is formed such that the diameter of the heat transfer tube group near the high-rate inflow portion of the EGR gas is smaller than that near the low-speed inflow portion of the EGR gas. And / or a structure in which the arrangement density is reduced near the high-speed inflow portion, so that the E density near the high-speed inflow portion is reduced.
The flow resistance of the GR gas is increased to induce a flow into the heat transfer tube group located near the low-speed inflow portion of the heat transfer tube group, and the flow rate in the heat transfer tube group near the low-speed inflow portion is increased to increase the flow rate of the heat transfer tube. The flow rate of the EGR gas can be made as uniform as possible throughout the group,
By generating a smooth flow, it is possible to enhance the cooling performance of the entire apparatus, and it is possible to effectively exhibit the cooling of the temperature of the EGR gas.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partially cutaway side view of a multi-tube EGR gas cooling device of the present invention, and FIG. FIG. 3 is a plan view schematically showing one embodiment of an arrangement state of heat transfer tube groups according to a main part of the present invention, FIG. 3 is a partially cutaway plan view schematically showing another embodiment, and FIG. FIG. 2 is a view corresponding to FIG. 2 schematically showing an embodiment, wherein (1) is a body pipe, and a supply port of a cooling medium for an engine or a cooling medium such as a refrigerant for an intercooler or a car air conditioner is provided near both ends thereof. (5) and a discharge port (5 '). Further, the heat transfer pipes (2) are fixed to the inside of the body pipe (1) by brazing, welding, or the like in a row with both ends of the heat transfer pipe (2) group between the partition walls (3) at both ends. A bonnet member (4) having an inflow port (4 ') and an outflow port (4 ") for the EGR gas at the outside of the end is similarly fixed by brazing, welding, or the like. It is connected and fixed via the flange (6).

In the present invention, when the arrangement of the heat transfer tubes (2) is arranged and the EGR piping is connected and fixed linearly to the bonnet member (4) as shown in FIG. As described above, the diameter of the heat transfer tube group near the central portion into which the EGR gas flows at a high speed is made smaller than that near the outer portion, or the arrangement density of the tube group near the central portion is made lower than that near the outer portion (that is, the central portion). It is important to increase the pitch interval between the heat transfer tube groups in the vicinity of the section, or to reduce the number of heat transfer tube groups in the unit area near the center section. Alternatively, it is preferable that the arrangement of the heat transfer tube (2) group is configured such that the tube diameter is gradually reduced toward the central portion as shown in FIG.

Further, when the EGR pipe is bent and connected and fixed so as to be substantially perpendicular to the bonnet member (4) as shown in FIG. 6 (b), the arrangement of the heat transfer pipe (2) group is shown in FIG. 4, the diameter of the heat transfer tube group near the outside of the bent portion and having a high flow velocity is smaller than that near the inside, or the arrangement density of the heat transfer tube group near the high speed inflow portion is closer to the low speed inflow portion. The arrangement of the heat transfer tubes (2) group may be configured to be smaller, and the tube diameter may be gradually reduced toward the vicinity of the high-speed inflow portion of the EGR from the vicinity of the low-speed inflow portion, and the arrangement density may be sequentially reduced. Is preferred.

The distribution of the flow rate of the EGR gas is, for example, E
Since it may fluctuate depending on the flow rate of GR gas, the diameter of the EGR pipe, the angle of expansion of the bonnet member (4), the diameter of the body tube (1), etc., a model EGR gas cooling device is manufactured in advance and actually It is preferable to determine the arrangement of the heat transfer tubes (2) after measuring the flow rate of the EGR gas.

According to the present invention, the EG of the heat transfer tube (2) group inside the body tube (1) is constructed by the above configuration.
EG is introduced into the heat transfer tube group located near the low-speed inflow portion of R gas.
Inducing the flow of R gas, increasing the flow rate of the low-speed inflow section, and making the flow velocity uniform in each heat transfer tube as much as possible,
By generating a smooth flow of the EGR gas, it is possible to enhance the cooling performance of the entire apparatus, and to effectively exert the cooling of the temperature of the EGR gas.

[0013]

As described above, in the multi-tube type EGR gas cooling device according to the present invention, the diameter of the group of heat transfer tubes (2) is reduced near the high-speed inflow portion of the EGR gas and / or near the high-speed inflow portion. By adopting a structure having a low array density, EG
EG is introduced into the heat transfer tube group located near the low-speed inflow portion of R gas.
The flow of the R gas is induced, the flow rate of the low-speed inflow portion is increased, and the speed of the flow of the EGR gas flowing through the heat transfer tube group as a whole can be made as uniform as possible. Cooling performance can be increased,
This is a very useful multi-tube type EGR gas cooling device, for example, capable of effectively exhibiting a temperature decrease of the EGR gas.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view of a multi-pipe EGR gas cooling device according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing an embodiment of the arrangement of the heat transfer tube group according to the main part of the present invention in FIG.

FIG. 3 is a partially cutaway plan view schematically showing another embodiment.

FIG. 4 is a diagram corresponding to FIG. 2, schematically showing still another embodiment.

FIG. 5 is a partially cutaway plan view showing an arrangement of heat transfer tube groups showing a conventional example.

6A and 6B are explanatory diagrams showing a state of inflow of EGR gas and a flow velocity distribution thereof in a conventional example, in which FIG. 6A shows a state in which the EGR gas is connected to an EGR pipe in a straight line, and FIG. It is a figure showing the state where it was bent and connected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body pipe 2 Heat transfer tube group 3 Partition wall 4 Bonnet member 4 'Inlet 4 "Outlet 5 Supply port 5' Discharge port 6 Flange

Claims (2)

[Claims] 1. A heat transfer tube group having both ends thereof fixed in a row between partition walls at both ends of a body pipe provided with a cooling medium inlet and a discharge port, and furthermore, both sides of the body tube In the EGR gas cooling device having a bonnet member fixedly provided with an inlet and an outlet for the EGR gas having a mounting flange wall on the outside of the portion, the heat transfer pipes (2) group is provided with a high-speed EGR gas The diameter of the heat transfer tube group in the inflow portion is formed to be smaller than the low-speed inflow portion of the EGR gas, and / or the arrangement density of the high-speed inflow portion is made lower than the arrangement density of the low-speed inflow portion. Multi-tube type EGR gas cooling device. 2. The heat transfer tube (2) group is characterized in that the diameter of the heat transfer tubes (2) group is gradually reduced from the low speed inflow portion toward the high speed inflow portion, and the arrangement density thereof is also gradually reduced. The multi-pipe EGR gas cooling device according to claim 1.