JP2007315323A - System structure of egr cooler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system structure of an EGR cooler, capable of restraining local boiling by two heat exchangers, capable of preventing reduction in durability, and capable of enhancing the whole heat exchange efficiency. <P>SOLUTION: This system structure has two tube type heat exchangers for cooling the respective tube outer peripheries by cooling water, by passing EGR gas through into respective tubes, by arranging a cooling water inlet pipe and a cooling water outlet pipe in an outer shell of these heat exchangers, by storing a tube assembly of supporting both ends of the respective tubes by a partition plate, inside the outer shell of the cylindrically formed heat exchangers, in a state of respectively opening the mutual respective tubes, by arranging a large number of axially long tubes of the same length in parallel; and is constituted so as to connect a pipe of engine cooling water to the high temperature side heat exchanger for passing the EGR gas first among these two tube type heat exchangers, and to connect a pipe of the cooling water cooled by an exclusive radiator to the low temperature side heat exchanger for passing the EGR gas after this high temperature side heat exchanger. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a system structure of an EGR cooler that can be divided into two in the flow direction to improve cooling efficiency.

In recent years, with the tightening of exhaust gas regulations for diesel engines, the environment surrounding the EGR cooler has become severe, such as an increase in the temperature of the EGR gas, an increase in gas flow rate, and a decrease in the gas outlet temperature of the EGR cooler (an increase in heat dissipation). It is desired to increase the amount of heat and maintain high temperature durability.
In general, around the engine, as shown in FIG. 5, an intercooler 2 and a radiator 3 are arranged in front of the diesel engine 1, and an EGR cooler 4 or 6 is arranged in the rear. The charger 5 is disposed, and the turbocharger 5 is disposed so that the compressor 5a is directed from the front and the exhaust gas from the turbine 5b is discharged rearward.

In the EGR coolers 4 and 6, as shown by a multi-tube heat exchanger incorporating a large number of circular tubes in FIG. 6 or a flat tube heat exchanger incorporating a large number of flat tubes in which radiating fins are installed in FIG. Cooling water inlets 4a and 6a are provided at the end on the gas inlet side, cooling water outlets 4b and 6b are provided at the end on the gas discharge side, and flanged headers 4c, 4d, 6c, 6d is provided, and the sizes of the flanges 4e, 4f, 6e, and 6f are determined so that they can be bolted to the piping from the diesel engine 1 side.
As shown in FIG. 8, the internal structure of the EGR coolers 4 and 6 includes a plurality of tubes 4i,..., 4i, 6i,. A multi-tube heat exchanger or a flat tube containing a tube assembly 7 that supports each tube at approximately equal intervals by a partition plate for closing the end portion of 6g and the outlet side partition plates 4h, 6h. Configure as a heat exchanger.

The relationship between the inlet / outlet of the exhaust gas and the inlet / outlet of the cooling water to the EGR coolers 4 and 6 forming the multi-tubular heat exchanger and the tube type heat exchanger is as follows. 6a is provided, and cooling water outlets 4b and 6b are provided at the end on the gas outlet side, and a device is devised so that the flow can flow evenly in the main body by the pressure of the cooling water (patent flow method). Reference 1).
There is also a cooling water inlet 4a, 6a provided at the end on the gas discharge side and a cooling water outlet 4b, 6b provided at the end on the gas inlet side (counterflow system) (Patent Document 2).

JP 2000-045883 A JP 2000-274990 A

[Problems of the prior art]
In the EGR coolers 4 and 6, the exhaust gas temperature is higher than 500 ° C. on the gas inlet side, and the cooling water inlet temperature is approximately 80 ° C. to 90 ° C. because the cooling water after cooling the diesel engine 1 is used. On the gas inlet side, the temperature difference between the two fluids increases, and the cooling water may boil.
In order to suppress this boiling, the cooling water inlets 4a and 6a are provided at the gas inlet side ends of the EGR coolers 4 and 6, and the cooling water outlets 4b and 6b are provided at the gas outlet side ends. There is a structure in which the flow is evenly diffused by the inflowing pressure (cocurrent flow type). In this structure, the flow of EGR gas and cooling water is in the same direction. The temperature difference between the two fluids decreases due to the decrease and the increase in the cooling water temperature, and the amount of heat exchange decreases.
For this reason, although what is divided into two in the longitudinal direction is considered, if the same cooling water is used, the temperature on the inlet side does not change, and the piping system is branched and formed on both the inlet side and the outlet side. As a result, piping is complicated and installation work becomes difficult.

  The present invention has been made in view of the above-mentioned problems in the prior art, and the technical problem specifically set in order to solve this problem is to suppress local boiling with a 2-split type and to reduce durability. It is an object of the present invention to provide a system structure of an EGR cooler that can prevent the occurrence of heat and improve the overall heat exchange efficiency.

In order to identify the system structure of the EGR cooler that effectively solves the above-mentioned problems in the present invention, all the matters recognized as necessary are covered and concretely configured problem solving means is shown below.
The first problem-solving means related to the system structure of the EGR cooler is to support both ends of each tube by a partition plate in a state where a large number of tubes having the same length in the axial direction are parallel and each tube is opened. The tube assembly is accommodated inside a cylindrical heat exchanger outer shell, and a cooling water inlet pipe and a cooling water outlet pipe are provided in the outer shell of the heat exchanger, and EGR gas passes through each tube. Two tube heat exchangers that cool the tube periphery with cooling water are provided, and the engine cooling water piping is connected to the high temperature side heat exchanger through which the EGR gas first passes among these two tube heat exchangers. The low-temperature side heat exchanger through which the EGR gas passes after the high-temperature side heat exchanger is connected to a cooling water pipe cooled by a dedicated radiator.

Further, the second problem-solving means according to the system structure of the EGR cooler is characterized in that the high-temperature side heat exchanger and the low-temperature side heat exchanger are integrally formed by bolting concentrically.
Further, the third problem-solving means according to the system structure of the EGR cooler is the same as that described above, in which the cooling water inlet of the high temperature side heat exchanger is arranged on the EGR gas inlet side and the cooling water outlet is arranged on the EGR gas outlet side. The cooling water inlet of the low temperature side heat exchanger is arranged on the EGR gas outlet side, and the cooling water outlet is arranged on the EGR gas inlet side, so that the high temperature side heat exchanger is cocurrent and the low temperature side heat exchanger is directed. It is characterized by the flow.
Further, the fourth problem-solving means related to the system structure of the EGR cooler is the same as that described above, in which a multi-tubular heat exchanger is formed as the high-temperature side heat exchanger and arranged on the EGR gas inlet side, and as the low-temperature side heat exchanger A flat tube heat exchanger is formed and arranged on the EGR gas outlet side, the high temperature side heat exchanger is set as a parallel flow, and the low temperature side heat exchanger is set as a counter flow.

In the first problem solving means relating to the system structure of the EGR cooler, there are two high-temperature side heat exchangers and low-temperature side heat exchangers, and each of the engine cooling water and the cooling water cooled by a dedicated radiator is heated. By using it in the exchanger, the temperature relationship between the EGR gas and the cooling water is easily maintained in the specified state, the heat exchange amount is increased, the local boiling is suppressed, the deterioration of durability is prevented, and the overall heat exchange efficiency Can be increased.
In the second problem-solving means related to the system structure of the EGR cooler, the high-temperature side heat exchanger and the low-temperature side heat exchanger are integrated, so that the passage of the EGR gas is improved and the heat exchange efficiency is improved. , Heat exchangers can be put together compactly.

  In the third problem solving means relating to the system structure of the EGR cooler, the engine cooling water can be supplied to the high temperature side heat exchanger, and the cooling water from an independent radiator can be supplied to the low temperature side heat exchanger. The degree of freedom of cooling water supply is increased, temperature management is facilitated, cooling efficiency can be improved, the high-temperature side heat exchanger is parallel flow, and the low-temperature side heat exchanger is counterflow, so high-temperature side heat exchange In the vessel, the dynamic pressure at which the cooling water flows into the end plate and the tube on the inlet side of the high-temperature gas is used to effectively cool the water by spreading it, suppressing local boiling, and exposing the tube. Durability can be prevented, and in a low-temperature side heat exchanger, the EGR gas outlet temperature of the high-temperature side heat exchanger can be preferably used as a countercurrent by setting it to 200 ° C. or less, preferably around 150 ° C. Can It is possible to maintain high efficiency of the exchanger, it is possible to lower the minimum exhaust gas temperature at EGR gas outlet.

  In the fourth problem-solving means relating to the system structure of the EGR cooler, the high-temperature side heat exchanger disposed on the EGR gas inlet side is a multi-tube heat exchanger that cools cooling water in parallel flow. The flow is smooth and spreads easily, the EGR gas outlet temperature can be easily lowered to the desired set temperature, and the low temperature side heat exchanger located on the EGR gas outlet side is a flat tube type heat that cools the cooling water countercurrently Since the exchanger is used, the heat exchange efficiency can be kept high, the cooling can be effectively performed, and the minimum exhaust gas temperature at the EGR gas outlet can be effectively reduced.

Hereinafter, the best embodiment according to the present invention will be described in detail.
However, this embodiment is specifically described for better understanding of the gist of the invention, and does not limit the content of the invention unless otherwise specified.
In addition, the same thing as a prior art example attaches | subjects the same code | symbol, and abbreviate | omits detailed description.

[First Embodiment]
As shown in FIG. 1, the EGR cooler of the first embodiment has a high temperature side heat exchanger 10a and a low temperature side heat exchanger 10b arranged in series behind the diesel engine 1 with respect to the flow of EGR gas, The high temperature side heat exchanger 10a is provided with a cooling water inlet 11a and a cooling water outlet 11b for connecting the engine cooling water pipes 8a and 8b so that the engine cooling water can be supplied to the low temperature side heat exchanger 10b. Is provided with a cooling water inlet 12a and a cooling water outlet 12b connected to the pipes 9a and 9b from the dedicated radiator 9, so that cooling water dedicated to the low temperature side can be supplied.

As shown in FIG. 2, the high temperature side heat exchanger 10a and the low temperature side heat exchanger 10b both form a multi-tubular heat exchanger, and both are provided with flanges 10c and 10d at the ends of the outer shell, The EGR gas that has been concentrically and integrally coupled by constriction and has passed through the high temperature side heat exchanger 10a immediately flows into the low temperature side heat exchanger 10b so as not to lower the heat exchange efficiency.
And the high temperature side heat exchanger 10a and the low temperature side heat exchanger 10b are respectively provided with cooling water inlets 11a and 12a and cooling water outlets 11b and 12b, and the high temperature side heat exchanger 10a has a cooling water inlet 11a that is EGR. The cooling water outlet 11b is arranged on the EGR gas outlet side, the cooling water inlet 12a of the low temperature side heat exchanger 10b is arranged on the EGR gas outlet side, and the cooling water outlet 12b is arranged on the EGR gas inlet side. Arranged, the high temperature side heat exchanger 10a is used as a parallel flow, and the low temperature side heat exchanger 10b is used as a counter flow.

  When local boiling is suppressed by using the high-temperature side heat exchanger 10a as a parallel flow and improving the spreading of the water by using the dynamic pressure when cooling water flows in, each tube 4i of the tube assembly 7 which is an EGR gas passage. ,..., 4i can be eliminated from factors such as being exposed from the cooling water. Further, in the low temperature side heat exchanger 10b, when the EGR gas temperature is set to 200 ° C. or less, preferably around 150 ° C. at the EGR gas inlet, it can be effectively cooled by using a counter flow, and the heat exchanger As a result, the minimum temperature of the EGR gas can be lowered to a lower temperature.

[Second Embodiment]
As in the first embodiment, the EGR cooler of the second embodiment has a high-temperature side heat exchanger 20a and a low-temperature side heat exchanger 20b arranged in series behind the diesel engine 1 with respect to the flow of EGR gas. In the high temperature side heat exchanger 20a, a cooling water inlet 21a and a cooling water outlet 21b are provided and connected to the pipes 8a and 8b, respectively, so that engine cooling water can be supplied for cooling, and low temperature side heat exchange is performed. The vessel 20b is provided with a cooling water inlet 22a and a cooling water outlet 22b, and pipes 9a and 9b for connecting to a dedicated radiator 9 can be connected to supply cooling water dedicated to the low temperature side. To.

As shown in FIG. 3, the high temperature side heat exchanger 20a and the low temperature side heat exchanger 20b are both provided with flanges 20c and 20d at the end of the outer shell, and are concentrically and integrally coupled by bolt tightening. The EGR gas that has passed through the high temperature side heat exchanger 20a immediately flows into the low temperature side heat exchanger 20b so as not to lower the heat exchange efficiency.
And each of the cooling water inlets 21a, 22a and the cooling water outlets 21b, 22b of the high temperature side heat exchanger 20a and the low temperature side heat exchanger 20b is connected to the cooling water inlet 21a of the high temperature side heat exchanger 20a as an EGR gas inlet. The cooling water outlet 21b is arranged on the EGR gas outlet side, the cooling water inlet 22a of the low temperature side heat exchanger 20b is arranged on the EGR gas outlet side, and the cooling water outlet 22b is arranged on the EGR gas inlet side. Thus, the high temperature side heat exchanger 20a is used as a parallel flow, and the low temperature side heat exchanger 20b is used as a counter flow.

  When local boiling is suppressed by making the high temperature side heat exchanger 20a a parallel flow and using a dynamic pressure when cooling water flows in to improve the spread of water, each tube 6i of the tube assembly 7 which is an EGR gas passage. ,..., 6i can be eliminated from factors such as exposure from the cooling water. Moreover, in the low temperature side heat exchanger 20b, when the EGR gas temperature is set to 200 ° C. or less, preferably around 150 ° C. at the EGR gas inlet portion, it can be effectively cooled by making it countercurrent, and the heat exchanger As a result, the minimum temperature of the EGR gas can be lowered to a lower temperature.

[Function and effect]
In the EGR cooler according to the first embodiment and the second embodiment configured as described above, both of the independent heat exchangers of the high temperature side and the low temperature side are connected in series in the EGR gas flow direction, thereby It is possible to increase the exchange efficiency, suppress the decrease in durability, improve the operation rate, facilitate the assembly, and reduce the cost.

[Third Embodiment]
In the EGR cooler of the third embodiment, as in the first and second embodiments, a high temperature side heat exchanger 30a and a low temperature side heat exchanger 30b are arranged in series behind the diesel engine 1 with respect to the flow direction of the EGR gas. The high temperature side heat exchanger 30a is formed as a multi-tube heat exchanger, and the cooling water inlet 31a and the cooling water outlet 31b are provided to connect the pipes 8a and 8b to supply engine cooling water. The low temperature side heat exchanger 30b is formed as a flat tube heat exchanger, and is provided with a cooling water inlet 32a and a cooling water outlet 32b and connected to the pipes 9a and 9b, respectively. The cooling water can be supplied from the radiator 9.

As shown in FIG. 4, the high temperature side heat exchanger 30a and the low temperature side heat exchanger 30b are provided with flanges 30c and 30d at the end of the outer shell, and are concentrically and integrally coupled by bolt tightening. The EGR gas that has passed through the high temperature side heat exchanger 30a immediately flows into the low temperature side heat exchanger 30b so that the heat exchange efficiency does not have to be lowered.
The high temperature side heat exchanger 30a and the low temperature side heat exchanger 30b are respectively provided with pipes 31a and 32a as cooling water inlets and the pipes 31b and 32b as cooling water outlets. The inlet 31a is disposed on the EGR gas inlet side, the cooling water outlet 31b is disposed on the EGR gas outlet side, the cooling water inlet 32a of the low temperature side heat exchanger 30b is disposed on the EGR gas outlet side, and the cooling water outlet 32b is disposed on the EGR. Arranged on the gas inlet side, the high temperature side heat exchanger 30a is used as a parallel flow, and the low temperature side heat exchanger 30b is used as a counter flow.

  When the high-temperature side heat exchanger 30a is used as a parallel flow and the dynamic pressure at the time when cooling water flows in is used to improve the spread of water and suppress local boiling, each tube 4i of the tube assembly 7 serving as an EGR gas passage is provided. .., 4i can be eliminated from factors such as exposure from the cooling water. Further, in the low temperature side heat exchanger 30b, when the EGR gas temperature is set to 200 ° C. or less, preferably around 150 ° C. at the EGR gas inlet, each tube 6i,. The EGR gas in 6i can be cooled effectively by cooling with the cooling water outside the tube and countercurrent, so that the efficiency as a heat exchanger can be kept high, and the minimum temperature of EGR gas can be more effectively reduced. Can be lowered to low temperatures.

[Function and effect]
In the EGR cooler of the third embodiment configured as described above, the high-temperature side heat exchanger is a multi-tube heat exchanger, and the low-temperature side heat exchanger is a flat tube heat exchanger, which is serially arranged in the EGR gas flow direction. By connecting to the heat exchanger, the heat exchanger can be used more efficiently according to the flow direction of the EGR gas, the heat exchange efficiency can be improved, and the decrease in durability can be suppressed.

[Another aspect]
Such an embodiment is specifically described in order to facilitate understanding of the gist of the invention, but does not limit the content of the invention, and is not particularly described (including design content). The embodiment is not limited, and may be changed as appropriate. In this sense, some other embodiments that meet the spirit of the invention are shown below.

Although the high-temperature side heat exchanger 20a is a parallel flow and the low-temperature side heat exchanger 20b is a countercurrent, the heat exchange efficiency is not necessarily formed in such a form, but both are parallel or countercurrent. If piping is easy without lowering, it can be used.
For this reason, it can be divided into two heat exchangers, and the post-process including assembly can be processed efficiently, improving work efficiency, and reducing costs and improving heat exchange efficiency. Is available.

1 is a system diagram of an EGR cooler according to an embodiment of the present invention. It is an expansion perspective view which shows the multitubular heat exchanger by the 1st embodiment of an EGR cooler same as the above. It is an expansion perspective view which shows the flat tube type heat exchanger by the 2nd embodiment of an EGR cooler same as the above. It is an expansion perspective view which shows the case where the multitubular heat exchanger and flat tube type heat exchanger by a 3rd embodiment of an EGR cooler same as the above are combined. It is a system system | strain diagram of the conventional EGR cooler. It is a perspective view which shows the multitubular heat exchanger used for the conventional EGR cooler. It is a perspective view which shows the flat tube type heat exchanger used for the conventional EGR cooler. It is a longitudinal cross-sectional view which shows the internal structure of the conventional EGR cooler.

Explanation of symbols

1 Diesel engine 2 Intercooler 3 Radiator 4, 6 EGR cooler 4a, 6a Cooling water inlet 4b, 6b Cooling water outlet 4c, 4d, 6c, 6d Flange header 4e, 4f, 6e, 6f Flange 4g, 6g (EGR gas inlet Side) Partition plates 4h, 6h, 7h (EGR gas outlet side) Partition plates 4i, 6i Tube 7 Tube assemblies 8a, 8b (Engine cooling water) Piping 9 (Dedicated) Rajectors 9a, 9b (Cooling water by dedicated radiators) Piping 10a, 20a, 30a High temperature side heat exchangers 10b, 20b, 30b Low temperature side heat exchangers 10c, 10d, 20c, 20d, 30c, 30d Flange 11a, 12a, 21a, 22a, 31a, 32a Cooling water inlet 11b , 12b, 21b, 22b, 31b, 32b Cooling water outlet

Claims (4)

A tube assembly in which a large number of tubes with the same length in the axial direction are parallel to each other and the tubes are spaced from each other and both ends of each tube are supported by a partition plate is placed outside the cylindrical heat exchanger. Tube-type heat exchanger that is housed inside the shell, and is provided with a cooling water inlet pipe and a cooling water outlet pipe in the outer shell of the heat exchanger so that EGR gas passes through each tube and the outer periphery of each tube is cooled by cooling water. With two,
Of these two tube-type heat exchangers, the high-temperature side heat exchanger that passes EGR gas first is connected to the engine cooling water piping, and the low-temperature side heat exchanger that passes EGR gas is cooled by a dedicated radiator. The system structure of the EGR cooler, characterized by connecting the piping of the cooling water.   The system structure of the EGR cooler according to claim 1, wherein the high temperature side heat exchanger and the low temperature side heat exchanger are integrally formed by concentrically connecting bolts.   The cooling water inlet of the high temperature side heat exchanger is arranged on the EGR gas inlet side, the cooling water outlet is arranged on the EGR gas outlet side, and the cooling water inlet of the low temperature side heat exchanger is arranged on the EGR gas outlet side. The system structure of the EGR cooler according to claim 1, wherein a cooling water outlet is disposed on an EGR gas inlet side, the high temperature side heat exchanger is set as a parallel flow, and the low temperature side heat exchanger is set as a counter flow. .   A multi-tube heat exchanger is formed as the high temperature side heat exchanger and disposed on the EGR gas inlet side, and a flat tube heat exchanger is formed as the low temperature side heat exchanger and disposed on the EGR gas outlet side. The system structure of the EGR cooler according to claim 1, wherein the high temperature side heat exchanger is a parallel flow and the low temperature side heat exchanger is a counter flow.

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