JP2001304047A - Egr gas cooling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR gas cooling device using a heat transfer tube, and wherein it is suppressed that soot mixed in EGR gas is stuck and grown on a heat transfer tube inner wall surface by using a tube body for generating columnar resonance with kinetic energy of EGR gas so as to improve heat transferring performance of the tube body and a temperature efficiency as well as beforehand eliminating the cause of engine malfunction. SOLUTION: Heat transfer tube group composed of a plurality of tube bodies are fixed to tube sheets fixed to both end parts of a shell tube inner wall, the tube bodies are fitted and supported to a penetrating hole whose inner wall is fixed to the outer peripheral part of the tube body at plural portions of the shell tube, end caps provided with a flow inlet and a flow outlet of EGR gas are fixed to outsides of both end parts of the shell tube, and the tube bodies having projection and recessed parts for generating columnar resonance by EGR gas which flows the inside of the heat transfer tube on an inner wall are used for the heat transfer tube of the EGR gas cooling device wherein a flow inlet and flow outlet for a cooling medium are disposed on the shell tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to cooling water for an engine,
The present invention relates to an apparatus for cooling an EGR gas with a refrigerant for a car air conditioner or cooling air.

[0002]

2. Description of the Related Art A method of extracting a part of exhaust gas from an exhaust gas system, returning the exhaust gas to an intake system of an engine again, and adding it to an air-fuel mixture is based on an EGR (Exhaust Gas Recircucu).
ration: exhaust gas recirculation). EGR is NO
x generation suppression, pump loss reduction, heat radiation loss to coolant due to lowering of combustion gas temperature, increase in specific heat ratio due to changes in working gas amount and composition, and improvement in cycle efficiency accompanying this. Because of its effectiveness, it is considered an effective way to improve the thermal efficiency of the engine. However, when the temperature of the EGR gas increases, the durability of the EGR valve and the like deteriorates due to a decrease in fuel efficiency and a heat effect due to a rise in the intake air temperature, which may cause early damage, and a water cooling structure for preventing the damage may be provided. It is recognized that you need to.

In order to avoid such a situation, there has been proposed a device for cooling the EGR gas by means of a cooling liquid or cooling air for the engine, and a multi-tube heat exchanger is generally used as this device.

As a multi-tube type EGR gas cooling device used in this case, for example, a plurality of heat transfer tubes are fixedly arranged on a tube sheet fixed to the inner wall of the body tube at both ends of the body tube. EGR gas inlet and EG at the end
An R gas outlet is provided, and further, a cooling medium inlet and a cooling medium outlet are provided on the body tube itself by outward burring forming, and the cooling medium inlet and the cooling medium outlet provided by this burring forming are: There is an EGR gas cooling device having a structure in which branch pipes are directly joined by brazing or welding.

[0005]

However, in such a conventional heat transfer tube, the inner peripheral surface thereof is smooth over the entire length of the heat transfer tube in the longitudinal direction as in a normal heat exchanger. Since a simple circular pipe is used, the EGR gas flowing into the pipe flows smoothly with almost no flow resistance. As a result, the heat of the EGR gas flowing near the center of the heat transfer pipe is reduced by the heat transfer pipe. Since the EGR gas is not transmitted to the inner peripheral wall surface and the EGR gas is not agitated in the heat transfer tube, heat transfer from the EGR gas to the heat transfer tube is not sufficiently performed, and the cooling efficiency of the EGR gas must be reduced. I didn't get it. Further, soot as an exhaust gas composition is mixed in the EGR gas, and in the process of passing the EGR gas through the tube, the soot easily adheres to the inner peripheral surface of the tube, and once adheres. The soot is hard to separate from the inner peripheral surface of the tube, and grows gradually as it accumulates to form a lump of soot.

When soot adheres and accumulates on the inner surface of the tube of the heat transfer tube in this way, this soot acts as a heat insulating material, and the heat transfer from the gas body, which is not so high even in a normal state, to the inner wall of the tube is further inhibited. In addition, the heat exchange between the EGR gas and the cooling medium, which is initially intended, is not continuously performed as desired, and the temperature efficiency gradually deteriorates. Here, the temperature efficiency is a ratio obtained by dividing a temperature difference between the inlet and the outlet of the EGR gas by a temperature difference between the inlet of the EGR gas and the inlet of the cooling medium. In addition, when the soot attached to the inner peripheral surface of the tubular body is deposited and grows gradually to become a large lump of soot, and this lump is separated by vibration or the like, the EGR
There is also a problem that the gas flows into the circulation system and flows into the engine to cause malfunction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem of soot, and uses a tube that generates air column resonance sound by the kinetic energy of EGR gas.
The soot mixed in the R gas is prevented from adhering to and growing on the inner wall surface of the heat transfer tube to prevent deterioration of the heat transfer performance of the tube, to maintain the temperature efficiency and to prevent the cause of engine malfunction in advance. It is an object of the present invention to provide an EGR gas cooling device using the removed heat transfer tube.

[0008]

In the EGR gas cooling apparatus according to the present invention, a plurality of heat transfer tubes are fixedly arranged on a tube sheet fixed to both ends of an inner wall of a body tube, and the heat transfer tubes are provided outside both ends of the body tube. In a multi-tube type EGR gas cooling device in which an end cap is fixed and an inlet and an outlet for EGR gas are provided in the end cap, the EGR gas flowing through the pipe serves as the heat transfer tube. The gist of the present invention is that at least one tube having irregularities on the inner wall that produces column resonance is used. Further, the heat transfer tube may be one having a plurality of ring-shaped or spiral-shaped continuous irregularities in the tube axis direction.

That is, the present invention utilizes a pipe that generates loud noise considered as air column resonance due to the kinetic energy of the fluid flowing in the pipe as means for preventing soot from adhering to the inner wall surface of the heat transfer pipe. When such a tubular body is used for a heat transfer tube, when air column resonance occurs due to the EGR gas flow flowing in the heat transfer tube, sound waves (resonance sound) having a frequency resonating in the tube are propagated. . At this time, the vibration energy of the propagating sound prevents the very fine soot from adhering to the inner wall surface of the heat transfer tube, and even if it adheres, the soot is immediately separated by the vibration energy. Therefore, deterioration of the pipe heat transfer coefficient is prevented, and the temperature efficiency is maintained.

[0010] A tube body in which air column resonance sound is generated by a fluid flowing in the tube has, for example, a plurality of grooves which are wound in one direction in the whole, and are formed continuously in a spiral shape with respect to the tube axis direction. The ridges and grooves are each formed into a gentle curved surface and the cross-sectional shape in the direction perpendicular to the tube axis is formed in one to four leaves, or a ring-shaped groove is formed in a direction perpendicular to the tube axis or with respect to the tube axis. There is one that is inclined at an angle. It is considered that the air column resonance generated by the fluid flowing through the pipe is caused by the vortex generated by the unevenness of the inner wall surface of the pipe. Since this air column resonance is reflected by an end cap or the like, at least one heat transfer tube that emits air column resonance may be used, and a heat transfer tube having irregularities on its inner wall to generate sounds of different pitches May be used in combination.

[0011]

FIG. 1 is a partially cutaway plan view showing an embodiment of an EGR gas cooling device according to the present invention, and FIG.
FIG. 3 is a plan view partially showing an embodiment of a heat transfer tube used in an R gas cooling device, FIG. 3 is a partial longitudinal sectional view taken along the line II-II, and FIG. 5 and FIG.
(A) is a partial side view showing a heat transfer tube having a ring-shaped groove in a direction perpendicular to the tube axis, and (b) is a part (a) showing another embodiment of the heat transfer tube used in the GR gas cooling device. FIG. 6C is a partial side view showing a heat transfer tube having a ring-shaped groove inclined at a certain angle with respect to the tube axis, and FIG. 6 is a heat transfer tube used in the EGR gas cooling device of the above. FIGS. 4A and 4B show another embodiment of the present invention, in which FIG. 4A is a view corresponding to FIG.
FIG. 4B is a diagram corresponding to FIG. 4 showing a heat transfer tube in which a cross section perpendicular to the tube axis is formed in a two-lobe shape, and FIG. 4C is a diagram showing a heat transfer tube in which a cross section perpendicular to the tube axis is formed in a four-lobe shape. FIG.

As shown in FIG. 1, a multi-tube type EGR gas cooling device according to the present invention has a plurality of heat transfer tubes 4 fixedly arranged on a tube sheet 3 fixed to both ends of an inner wall of a body tube 1. Preferably, each heat transfer tube 4 constituting this heat transfer tube group
Are fitted and supported at a plurality of locations of the body tube 1 in through holes 6 of a baffle plate 5 whose outer peripheral portion is fixed to the inner wall of the body tube 1.
End caps 7 are secured to the outside of both ends of the EGR gas pipe. The end cap 7 is provided with an EGR gas inlet 8 and an EGR gas outlet 9. The body tube 1 has a cooling medium inlet 10 and a cooling medium inlet. A medium outlet 11 is provided, and a branch pipe 12 is connected to the cooling medium inlet 10 and the cooling medium outlet 11 by brazing or welding.

Here, the heat transfer tube used in the EGR gas cooling device will be described. The heat transfer tube 4 shown in FIG. 2 is formed of a tube having an irregular surface on the tube inner wall so as to generate air column resonance sound, and has straight tube portions 4-4 connected to the tube sheet 3 at both ends. , The straight pipe portion 4-4
Except for the three grooves 4-
1, continuous ridges 4-2 and grooves 4-3 spirally formed with respect to the tube axis direction are each formed into a gentle curved surface, and a cross-sectional shape perpendicular to the tube axis is formed into a trilobal shape. The heat transfer tube spiral portion has a rope-like appearance, and has a structure in which a continuous ridge formed in a spiral shape protrudes from the inner peripheral surface of the tube. For example, a method of forming a spiral ridge 4-2 and a groove 4-3 in which the winding direction is one direction by using three rollers disposed at 120 ° intervals on the outer peripheral surface of the tube relative to the outer peripheral surface of the tube is used. Can be.

Here, the lead angle α, pitch p, and groove depth h of the helical winding of the groove with respect to the tube axis of the heat transfer tube 4 for generating the air column resonance sound are not particularly limited. The following conditions can be considered. Lead angle α is 45 degrees to 1
35 degrees, the pitch p is 0.5d to 10d when the diameter of the inscribed circle of the uneven portion is d, and the groove depth h is 1 / 20d to 1 / 2d.
It is. The reason for these limitations is that when the lead angle α is less than 45 degrees, the air column resonance due to the flow of the EGR gas flowing in the tube is unlikely to occur, and when it exceeds 135 degrees, the air column resonance is similarly unlikely to occur. . In the case of the pitch p, if the pitch is less than 0.5d, the vibration frequency of the vortex due to the unevenness in the pipe is too high to cause resonance, while if it exceeds 10d, the vibration frequency of the vortex due to the unevenness in the pipe is too low to resonate. That's why. Further, in the case of the groove depth h, if the groove depth is less than 1 / 20d, the groove is too shallow and the vortex is small, so that resonance does not occur. On the other hand, if the groove depth is more than 1 / 2d, the irregularities in the tube become large and the rigidity of the heat transfer tube is lost. This is because the flexibility becomes large and the vibration resistance becomes poor.

Next, the heat transfer tube 4 shown in FIGS.
Is composed of a tube having a ring-shaped groove 4-5 in a direction perpendicular to the tube axis, and irregularities are formed inside and outside the tube in a direction perpendicular to the tube axis. In the case of this heat transfer tube 4,
The lead angle α is 90 degrees, the pitch p is 0.2d to 5d, and the groove depth h is 1/20, where d is the diameter of the inscribed circle of the uneven portion.
d to 1 / 3d. Further, in the case of the heat transfer tube 4 having the ring-shaped groove 4-6 inclined at a certain angle with respect to the tube axis shown in (c), the lead angle α is 30 to 160 degrees, and the pitch p is 0.
2d to 5d. In the case of the heat transfer tube 4, irregularities are formed inside and outside the tube at a desired angle with respect to the tube axis.

The heat transfer tube 4 shown in FIG. 6 is another embodiment of the heat transfer tube 4 shown in FIG. 2 in which the cross section in the direction perpendicular to the tube axis is formed in a trilobal shape. The heat transfer tube 4 has one groove 4-1 whose winding direction is one direction.
A continuous ridge and a groove formed in a spiral shape with respect to the tube axis direction were each formed into a gentle curved surface, and one continuous ridge formed in a spiral shape protruded from the peripheral surface of the tube. It has a structure. In the case of a heat transfer tube in which the sectional shape in the direction perpendicular to the tube axis shown in FIG.
In the same manner as described above, continuous peaks and grooves formed spirally in the pipe axis direction are each formed into a gentle curved surface, and are formed spirally on the inner peripheral surface of the pipe. It has a structure in which two continuous ridges are projected. Further, in the case of the heat transfer tube 4 in which the cross-section in the direction perpendicular to the tube axis shown in FIG. Consecutive peaks and grooves formed in a spiral shape with respect to the tube axis direction were each formed into a gentle curved surface, and four continuous protrusions formed in a spiral shape protruded from the peripheral surface of the tube. It has a structure.

According to the heat transfer tube 4 having a structure in which one or a plurality of spiral or ring-shaped protrusions are provided inside so as to cause air column resonance by the EGR gas flow flowing in the tube as described above. Vibration energy of a sound wave (resonant sound) having a resonance frequency propagating in the tube prevents the very fine soot from adhering to the inner wall surface of the tube, and immediately separates even if it adheres.

[0018]

As described above, according to the present invention, since the heat transfer tube is constituted by a tube which causes air column resonance by the EGR gas flow flowing in the tube, sound waves (resonance sound) having a frequency resonating in the tube are generated. During the propagation process, the vibration energy of the propagating sound prevents the very fine soot from adhering to the inner wall of the heat transfer tube, and even if it adheres, it is immediately separated by the vibration energy, resulting in heat transfer performance. As a result, it is possible to provide an EGR gas cooling device having an effect that the temperature efficiency can be remarkably improved, the heat exchange rate can be improved, and the occurrence of engine trouble due to soot and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a partially broken plan view showing one embodiment of an EGR gas cooling device of the present invention.

FIG. 2 is a plan view partially showing an embodiment of a heat transfer tube used in the above EGR gas cooling device;

FIG. 3 is a partial longitudinal sectional view taken along the line II in FIG. 2;

FIG. 4 is a transverse cross-sectional view taken along a roll line in FIG. 2;

FIG. 5 shows another embodiment of the heat transfer tube used in the EGR gas cooling device of the above, wherein (a) shows a heat transfer tube having a ring-shaped groove in a direction perpendicular to the tube axis in a cross section of a lower half. Partial side view, (b) is a longitudinal cross-sectional view on the roll line of (a),
(C) is a partial side view showing a heat transfer tube having a ring-shaped groove inclined at an angle with respect to the tube axis, with a lower half sectioned.

6A and 6B show another embodiment of the heat transfer tube used in the EGR gas cooling device, in which FIG. 6A shows a heat transfer tube in which a cross section in a direction perpendicular to the tube axis is formed into a single leaf shape. FIG. 4B is a diagram corresponding to FIG. 4 showing a heat transfer tube in which a cross section perpendicular to the tube axis is formed in a two-lobed shape, and FIG. 4C is a diagram showing a heat transfer tube in which a cross section perpendicular to the tube axis is formed in a four-lobe shape. It is a figure equivalent to FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Body tube 2 Inner wall 3 Tube sheet 4 Heat transfer tube 4-1 Groove 4-2 Crest portion 4-3 Groove portion 4-4 Straight tube portion 4-5, 4-6 Ring groove 5 Baffle plate 6 Through hole 7 End Cap 8 EGR gas inlet 9 EGR gas outlet 10 Cooling medium inlet 11 Cooling medium outlet 12 Branch pipe

Claims (2)

[Claims] A plurality of heat transfer tubes are fixedly arranged on a tube sheet fixed to both ends of an inner wall of a body tube, and end caps are fixed to outside of both ends of the body tube. Is a multi-tube EGR gas cooling device provided with an inlet and an outlet for EGR gas,
An EGR gas cooling device, characterized in that at least one tube having irregularities on its inner wall, which causes air column resonance due to EGR gas flowing in the tube, is used. 2. The EGR gas cooling device according to claim 1, wherein the heat transfer tube has a plurality of ring-shaped or spiral-shaped continuous irregularities in the tube axis direction.