JP4386215B2 - EGR gas cooling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus that cools EGR gas using engine coolant, a car air conditioner refrigerant, cooling air, or the like.
[0002]
[Prior art]
A method in which a part of the exhaust gas is taken out from the exhaust system, returned to the engine intake system, and added to the air-fuel mixture is called EGR (Exhaust Gas Recirculation). EGR suppresses the generation of NOx (nitrogen oxide), reduces pump loss, reduces heat dissipation loss to the coolant due to lowering of combustion gas temperature, and increases specific heat ratio due to changes in working gas amount / composition. Since many effects such as improvement of cycle efficiency can be obtained, it is an effective method for improving the thermal efficiency of the engine.
[0003]
However, when the temperature of the EGR gas is increased and the amount of EGR gas is increased, the durability of the EGR valve is deteriorated due to its thermal action, which may cause premature breakage, and a water cooling structure is necessary to prevent this. It is recognized that there is a decrease in fuel consumption due to a decrease in charging efficiency as the intake air temperature increases. In order to avoid such a situation, an apparatus that cools EGR gas with engine coolant or the like is used. As this apparatus, a multi-tube heat exchanger is generally used.
[0004]
As shown in FIG. 5 and FIG. 6, the multitubular heat exchanger used in this case is a trunk pipe provided with a cooling medium inlet 11-1 and a cooling medium outlet 11-2 at both ends. 11, both end portions of the heat transfer tube group 12 are fixed to the tube sheet 13 made of sheet metal by brazing, while the tube sheet 13 is arranged with its outer peripheral end fixed to the inner wall of the trunk tube 11 by brazing. An end cap 14a provided with an EGR gas inlet 14a-1 is fixed to one end of the trunk tube 11, and an EGR gas outlet 14b-1 is provided at the other end. The end cap 14b is fixed, and the fastening flanges 15a and 15b are externally fixed to the outer opening ends of the gas inlet 14a-1 and the outlet 14b-1 of the end caps 14a and 14b. Structure and You have me.
[0005]
[Problems to be solved by the invention]
In the case of the conventional multi-tube heat exchanger used for cooling the EGR gas, the cooling medium is used to ensure the reliability of the fixing structure between the trunk tube 11, the tube sheet 13, and the end caps 14a and 14b. Since the inflow port 11-1 and the cooling medium outflow port 11-2 are respectively provided at positions away from the tube sheet 13 by a desired distance, particularly in the cooling medium inflow port 11-1 side, The cooling medium flowing into the tube sheet 13 on this side stagnates on the side of the tube sheet 13 and the range S surrounded by the dotted line shown in FIGS. 5 and 6 becomes an overheated area where cooling is insufficient, and the temperature of the EGR gas is in this overheated area When the temperature rises or the amount of EGR gas increases, the outer peripheral surface temperature of the heat transfer tube rises, causing boiling of the cooling medium. When the cooling medium boils, the outer surface of the heat transfer tube is covered with steam and cannot contact the cooling medium and heat exchange is not performed, so that the EGR gas is not cooled in the area, and as a result, the heat of the entire cooling device is heated. The exchange performance is deteriorated, and the EGR gas outlet temperature does not decrease.
[0006]
The present invention was made to solve the above-mentioned problems of the conventional multi-tube heat exchanger, and the heat exchange performance is lowered by eliminating the overheating area formed on the cooling medium inflow side and eliminating the boiling of the cooling medium. It is intended to provide an EGR gas cooling device that can prevent EGR and sufficiently cool the EGR gas.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a heat transfer tube group in a tube sheet fixed in the vicinity of both end portions of the inner wall of a trunk tube provided with a cooling medium inlet and a cooling medium outlet at both ends. Further, end caps are fixed to both ends of the trunk tube, and an EGR gas inlet and outlet are provided on the end cap, and the gas inlet and outlet of the end cap are provided. In the multi-tube EGR gas cooling device having a structure in which a fastening flange is fitted and fixed to the outer opening end of the outlet, the cooling medium inlet provided on the EGR gas inlet side is plural, In the second embodiment, a plurality of cooling medium inlets provided on the EGR gas inlet side are provided so that the cooling medium flowing into the trunk pipe flows vertically along the tube sheet on the EGR gas inlet side. Inclined with respect to the center line In the third embodiment, a plurality of cooling medium inflow ports provided on the EGR gas inflow side are provided, and the cooling medium flowing into the cylinder tube becomes a swirling flow, and the axis of the cylinder tube is provided. characterized by digits set to flow toward the vicinity of the fourth embodiment causes decentering the inlet of the EGR gas to the axis of said cylinder tube, the cooling medium eccentric side flows often the EGR gas A plurality of cooling medium inlets are provided so as to be concentrated.
[0008]
That is, the present invention uses a means for providing a plurality of cooling medium inlets as means for eliminating an insufficiently overcooled area caused by the cooling medium flow stagnating near the tube sheet on the cooling medium inlet side, As a result, the flow velocity in the vicinity of the tube sheet is made uniform and fast, and an overheating area hardly occurs, and boiling of the cooling medium on the EGR gas inlet side can be prevented.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an EGR gas cooling device corresponding to claim 1 of the present invention, in which (A) is a plan view with the central portion omitted, and (B) is a b- FIG. 2 is a longitudinal sectional view taken along line b, FIG. 2 shows an embodiment of an EGR gas cooling device corresponding to claim 2 of the present invention, (A) is a plan view with the central portion omitted, and (B). FIG. 3A and FIG. 3B are diagrams corresponding to FIG. 1B illustrating an EGR gas cooling device corresponding to claim 3 of the present invention, and FIG. 4 is the present invention. 1 is a front view showing an embodiment of an EGR gas cooling device corresponding to claim 4 of the present invention, wherein 1 is a trunk tube, 1-1a, 1-1b, 1-1c, 1-1d are cooling medium inlets, 1- 2a, 1-2b, 1-2c, 1-2d are cooling medium outlets, 2 is a heat transfer tube group, 3 is a tube sheet, 4 is an end cap, 4-1 is EGR gas Inlet, 4-2 outlet of the EGR gas, 5 is a fastening flange.
[0010]
First, the EGR gas cooling device of the present invention shown in FIG. 1 is an example in which two cooling medium inlets are provided, and two cooling medium inlets 1-1 are provided on the EGR gas inlet 4-1 side of the trunk tube 1. As shown in the figure, 1a is provided on the bottom surface side opposite to the cooling medium outlet 1-2a on both sides of the central axis of the trunk tube 1 at a desired interval and perpendicular to the trunk axis toward the trunk tube center. It is an example. In this case, since the two cooling medium inlets 1-1a are provided, the diameter is smaller than that of a normal one, and the cooling medium outlet 1-2a corresponds to the two cooling medium inlets 1-1a. The size is about twice the cross-sectional area of -1a.
[0011]
The EGR gas cooling device having the configuration shown in FIG. 1 is an example of a method of providing a plurality of cooling medium inlets provided on the EGR gas inlet side, and is provided on the lower surface side of the EGR gas inlet 4-1 side. In addition, since the cooling medium flowing into the trunk tube 1 from the two cooling medium inlets 1-1a flows toward the center of the trunk tube 1, the flow velocity in the vicinity of the tube sheet 3 on this side is made uniform. And there is no overheating area caused by stagnant flow. As a result, almost no boiling of the cooling medium occurs on the EGR gas inlet side. Then, the cooling medium flowing into the trunk pipe 1 from the cooling medium inlet 1-1a flows through the trunk pipe 1 without generating an overheat area, and cools the EGR gas flowing in the heat transfer pipe group 2 to cool it. It discharges from the medium outlet 1-2a.
[0012]
The EGR gas cooling device shown in FIG. 2 has a plurality of cooling medium inlets provided on the EGR gas inlet side so that the cooling medium flowing into the trunk pipe flows along the tube sheet on the EGR gas inlet side. This is an example of a system that is inclined with respect to a vertical line with respect to the axis of the tube, and three cooling medium inlets 1-1b are respectively provided on the EGR gas inlet 4-1 side of the barrel tube 1, and the axis of the barrel tube 1 is provided. A structure in which a desired interval is provided on the upper side and inclined toward the tube sheet side with respect to a vertical line with respect to the axis of the trunk tube 1 is formed. Here, the inclination angle θ of each of the three cooling medium inflow ports 1-1 is not particularly limited, and varies depending on the outer diameter of the trunk tube 1, but approximately 5 ° to 30 ° is appropriate. Needless to say, the inclination angle θ may be different from each other. Also in this case, since three cooling medium inlets 1-1b are provided, the diameter is smaller than that of a normal one, and the cooling medium outlet 1-2b corresponds to the three cooling medium inlets 1-1b. The size is about three times the cross-sectional area of 1-1b.
[0013]
In the case of the EGR gas cooling device having the configuration shown in FIG. 2, the cooling medium inlet 1-1b provided at the EGR gas inlet side inclines toward the tube sheet 3 side into the trunk pipe 1. Since all of the inflowing cooling medium flows along the inner surface of the tube sheet 3, it is possible to prevent the occurrence of an overheating area caused by the stagnation of the cooling medium flow, and the boiling of the cooling medium occurring on the EGR gas inlet side can be prevented. Can be prevented. The cooling medium flowing into the trunk tube 1 from the cooling medium inlet 1-1b flows in the trunk tube 1 without generating an overheat area as described above, and cools the EGR gas flowing in the heat transfer tube group 2. It discharges from the cooling medium outlet 1-2b.
[0014]
The EGR gas cooling device shown in FIG. 3 has a plurality of cooling medium inlets provided on the EGR gas inlet side, and the cooling medium that has flowed into the trunk pipe turns into a swirling flow and flows toward the vicinity of the axis of the trunk pipe. As shown in the figure, FIG. 3A is an example of a system provided in the tangential direction of the trunk pipe or in a direction close to the tangential direction, and FIG. 9A shows three cooling medium inlets 1-1c on the EGR gas inlet 4-1 side of the trunk pipe 1. Are arranged at intervals of 120 ° in the tangential direction of the trunk tube. (B) shows three cooling medium inlets 1-1c arranged on the EGR gas inlet 4-1 side of the trunk pipe 1 at intervals of 120 ° in the direction close to the tangential direction, and the cooling medium inlet. By removing the heat transfer tube in the vicinity of 1-1b, the cooling medium can smoothly flow to the vicinity of the center of the trunk tube 1. In this case as well, since three cooling medium inlets 1-1c are provided, the diameter is smaller than that of a normal one, and the cooling medium outlet 1-2c corresponds to the three cooling medium inlets 1-1c. The size is about three times the cross-sectional area of 1-1c.
[0015]
In the case of the EGR gas cooling apparatus having the configuration shown in FIGS. 3A and 3B, the cooling medium disposed at intervals of 120 ° in the tangential direction of the trunk tube or in the direction close to the tangential direction on the EGR gas inlet side. The cooling medium that has flowed into the trunk pipe 1 from the inlet 1-1c flows as a swirling flow toward the vicinity of the axial center of the trunk pipe. This can eliminate the boiling of the cooling medium that occurs on the EGR gas inlet side. Then, the cooling medium that has flowed into the tube 1 from the cooling medium inlet 1-1c flows in the tube 1 without generating an overheat area, and cools the EGR gas flowing in the heat transfer tube group 2 as described above. And discharged from the cooling medium outlet 1-2c.
[0016]
The EGR gas cooling apparatus shown in FIG. 4 has a plurality of cooling medium inlets so that the EGR gas inlet is eccentric with respect to the axial center of the trunk tube, and the cooling medium is concentrated on the eccentric side through which a large amount of EGR gas flows. This is an example of a system in which the EGR gas inlet 4-1 is offset by an eccentric amount l on the side opposite to the cooling medium outlet 1-2d with respect to the axis O of the trunk tube 1, In this structure, a total of three cooling medium inlets 1-1d are provided on a vertical line with respect to the axis of the trunk tube 1 on the eccentric side and on a horizontal center line passing through the eccentric axis O '. In this case as well, since three cooling medium inlets 1-1d are provided, the diameter is smaller than that of the normal one, and the cooling medium outlet 1-2d corresponds to the three cooling medium inlets 1-1d. The size is about three times the cross-sectional area of 1-1d.
[0017]
In the case of the EGR gas cooling device having the configuration shown in FIG. 4, the EGR gas inlet 4-1 is eccentric, and therefore the EGR gas flowing into the heat transfer tube group 2 inside the trunk tube 1 inevitably has a flow. Drift occurs, but the cooling medium flowing into the barrel 1 from the three cooling medium inflow ports 1-1d provided on the drift generation side concentrates on the eccentric side where a lot of EGR gas flows. It is possible to eliminate the overheating area caused by the stagnation of the flow and to prevent the cooling medium from boiling on the EGR gas inlet side. Then, the cooling medium that has flowed into the trunk tube 1 from the cooling medium inlet port 1-1d flows in the trunk tube 1 without generating an overheat area as described above, and cools the EGR gas flowing in the heat transfer tube group 2. And discharged from the cooling medium outlet 1-2d.
FIG. 4 shows an example in which the EGR gas inlet 4-1 is eccentric. However, even if the EGR gas 4-1 is not eccentric, the same effect can be obtained when the EGR gas flowing in is eccentric. can get.
[0018]
The number of installed cooling medium inlets 1-1a, 1-1b, 1-1c, and 1-1d in the present invention is not limited to the two to three exemplified here, and the cross-sectional area and size of the trunk pipe As appropriate, depending on
[0019]
【The invention's effect】
As described above, the EGR gas cooling device of the present invention is not cooled by the flow of the cooling medium stagnating near the tube sheet on the cooling medium inlet side due to the high kinetic energy of the cooling medium flowing in from the cooling medium inlet. As a result of being able to eliminate a sufficient overheating area, it is possible to prevent a temporary decrease in heat exchange performance due to boiling of the cooling medium on the EGR gas inlet side, and to achieve an excellent effect that the EGR gas can be sufficiently cooled. .
[Brief description of the drawings]
FIG. 1 shows an embodiment of an EGR gas cooling device corresponding to claim 1 of the present invention, in which (A) is a plan view with the central portion omitted, and (B) is b in (A). It is a longitudinal cross-sectional view on the -b line.
FIGS. 2A and 2B show an embodiment of an EGR gas cooling apparatus corresponding to claim 2 of the present invention, in which FIG. 2A is a plan view with the central portion omitted, and FIG. FIG.
FIGS. 3A and 3B illustrate an EGR gas cooling device corresponding to claim 3 of the present invention, wherein FIG. 3A is a view corresponding to FIG. 1B showing one embodiment, and FIG. 3B is another embodiment. FIG. 1B is a diagram corresponding to FIG.
FIG. 4 is a front view showing an embodiment of an EGR gas cooling device corresponding to claim 4 of the present invention.
FIG. 5 is a cross-sectional plan view showing an example of a conventional multi-tube EGR gas cooling apparatus that is the subject of the present invention, with the central portion omitted.
6 is a cross-sectional view taken along the line II in FIG.
[Explanation of symbols]
1 Body tube 1-1a, 1-1b, 1-1c, 1-1d Cooling medium inlet 1-2a, 1-2a, 1-2c, 1-2d Cooling medium outlet 2 Heat transfer tube group 3 Tube sheet 4 End Cap 4-1 EGR gas inlet 4-2 EGR gas outlet 5 Fastening flange

Claims (3)

A heat transfer tube group is fixedly arranged on a tube sheet fixed near both ends of the inner wall of the trunk tube provided with a cooling medium inlet and a cooling medium outlet at both ends, and end portions are provided at both ends of the trunk tube. The cap was fixed, and the end cap was provided with an EGR gas inlet and outlet, and a fastening flange was fitted and fixed to the outer opening end of the gas inlet and outlet of the end cap. In the multi-tube EGR gas cooling apparatus having the structure, the cooling medium flowing into the trunk pipe flows along the tube sheet on the EGR gas inlet side through a plurality of cooling medium inlets provided on the EGR gas inlet side. Thus, the EGR gas cooling device is provided so as to be inclined with respect to a vertical line with respect to the axis of the trunk tube. A plurality of cooling medium inlets provided on the EGR gas inlet side are provided so that the cooling medium flowing into the trunk pipe flows in a swirling flow toward the vicinity of the axis of the trunk pipe. 2. The EGR gas cooling device according to 1. A heat transfer tube group is fixedly arranged on a tube sheet fixed near both ends of the inner wall of the trunk tube provided with a cooling medium inlet and a cooling medium outlet at both ends, and end portions are provided at both ends of the trunk tube. The cap was fixed, and the end cap was provided with an EGR gas inlet and outlet, and a fastening flange was fitted and fixed to the outer opening end of the gas inlet and outlet of the end cap. In the multi-tube type EGR gas cooling apparatus having the structure, the EGR gas inlet is eccentric with respect to the axial center of the trunk pipe, and the cooling medium inlet is concentrated so that the cooling medium is concentrated at an eccentric position where the EGR gas flows largely. A plurality of EGR gas cooling devices.

Images