Exhaust gas recirculation cooler with multi-channel coolant

Abstract

The present invention relates to an exhaust gas recirculation cooler with multiple coolant flow channels, the exhaust gas recirculation cooler includes a shell, one end of the air inlet of the shell is provided with a coolant flow channel arranged along the cross-sectional direction of the shell, the water inlet of the coolant flow channel is connected to the water inlet of the shell; the inner cavity corners of the shell are provided with corner connecting holes connected to the coolant flow channel, and the inner cavity side of the shell is provided with at least one side connecting hole connected to the coolant flow channel. By arranging the coolant flow channel on the shell, the water inlet of the coolant flow channel is connected to the water inlet of the shell; the inner cavity corners of the shell are provided with corner connecting holes connected to the coolant flow channel, and the inner cavity side of the shell is provided with at least one side connecting hole connected to the coolant flow channel; when the coolant flows through the water inlet, a part of it will directly enter the inner cavity of the shell, and the other part will flow into a separate coolant flow channel, and then enter the inner cavity of the shell from connecting holes at different positions, and reach the designated high-risk boiling area for heat exchange.

Description

Technical Field

[0001] The invention relates to the technical field of commercial vehicle exhaust gas cooling, and in particular to an exhaust gas recirculation cooler with multiple coolant flow channels. Background Art

[0002] The main function of the exhaust gas recirculation (EGR) system is to suppress the generation of NOx by reducing the high temperature and oxygen-rich environment in the engine cylinder. The principle is to return part of the burned exhaust gas to the intake manifold after cooling, and re-enter the cylinder together with the fresh mixed gas. The burned exhaust gas contains a large amount of inert gas, which does not participate in the combustion in the combustion chamber, but can absorb a large amount of heat and dilute the mixed gas, thereby reducing the oxygen concentration and the maximum combustion temperature, and suppressing the generation of NOx. The exhaust gas recirculation (EGR) cooler is a device that reduces the temperature of the circulating exhaust gas. Before it is mixed with fresh air, the temperature is reduced to the target value (110-140°C) to reduce the temperature of the mixed gas in the combustion chamber. For the sake of convenience, the exhaust gas recirculation (EGR) cooler is referred to as the EGR cooler below.

[0003] The EGR cooler has become a high-incidence area for failures on commercial vehicles due to its working environment of high intake air temperature and intake air flow, among which boiling failure is the most common. Boiling, commonly known as "dry burning", is mainly caused by the uneven local coolant velocity field on the water inlet side, which causes the coolant in this area to continue to heat up until the boiling point under high heat load. Taking the EGR cooler described in this patent as the research object, according to the CFD flow field simulation results, combined with the boiling failure performance in the terminal market, it is concluded that the coolant flow velocity of the four rows of heat pipes far away from the water inlet is low, and the row farthest from the water inlet is particularly obvious. Large areas of low flow velocity appear in the corners on both sides. Local film boiling is very likely to occur under harsh working conditions, causing the heat pipe to crack. The coolant flow velocity and uniformity of the two rows of heat pipes close to the water inlet are relatively good. Therefore, how to optimize the coolant flow channel layout, accurately introduce high-flow coolant into the high-risk boiling area, and ensure heat exchange efficiency is the key to fundamentally solving the boiling failure of the EGR cooler;

[0004] The current EGR coolers all use a single-channel water inlet, that is, the coolant directly enters the shell cavity through the water inlet and flows around the heat dissipation pipe for heat exchange. Boiling failure is mainly reduced by reasonably designing the internal shape of the water inlet and the volume of the shell cavity: optimizing the coolant flow field on the high-temperature side to make the coolant more evenly distributed on the high-temperature side, ensuring the flow rate and reducing the blind area of ​​the flow field, enhancing heat exchange and reducing the risk of boiling. However, the improvement effect of optimizing the water inlet and the shell cavity is limited, especially at the end far away from the water inlet. Due to the influence of the heat dissipation pipe bundle flow resistance, liquid side blind areas or areas with low flow rates will inevitably appear, and when the water inlet is located below the EGR cooler, it is more obvious. The low-speed field area and blind area of ​​the coolant will cause the liquid side temperature to continue to rise until boiling, and local film boiling is the most common. The bubbles generated by film boiling will cause a vacuum area to form on the heat exchange wall of the heat dissipation pipe, isolating the heat exchange wall and the coolant, reducing the heat exchange performance, and in severe cases, it will accelerate fatigue cracking of the heat dissipation pipe, resulting in gas-liquid communication.

[0005] As the displacement and EGR rate of commercial vehicle engines increase, the heat load on the EGR cooler also increases, which puts higher requirements on the boiling resistance of the EGR cooler. How to reasonably design the cooler to significantly reduce the boiling risk in the early stage of product development is the key. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an exhaust gas recirculation cooler with multiple coolant flow channels to solve the problems of uneven coolant flow field on the existing water inlet side (exhaust gas high temperature test) and boiling failure under high heat load conditions, aiming to improve the boiling resistance of the EGR cooler and reduce the failure rate in the terminal market.

[0007] The technical solution adopted by the present invention is: an exhaust gas recirculation cooler with multiple coolant flow channels, characterized in that: it includes a shell, one end of the air inlet of the shell is provided with a coolant flow channel arranged along the cross-sectional direction of the shell, and the water inlet of the coolant flow channel is connected to the water inlet of the shell; the inner cavity corners of the shell are provided with corner connecting holes connected to the coolant flow channel, and the inner cavity side of the shell is provided with at least one side connecting hole connected to the coolant flow channel.

[0008] Preferably, the coolant flow channel comprises a first coolant flow channel and a second coolant flow channel, the first coolant flow channel is arranged on one side of the shell, and the second coolant flow channel is arranged on the other side of the shell.

[0009] Preferably, a first upper corner connecting hole is provided at a corner away from the water inlet of the shell on one side of the shell, and a first lower corner connecting hole is provided at a corner close to the water inlet of the shell; at least one first side connecting hole is provided between the first upper corner connecting hole and the first lower corner connecting hole, and the first side connecting hole is provided on the inner side wall of the shell away from the water inlet of the shell; the first upper corner connecting hole, the first lower corner connecting hole and the first side connecting hole connect the first coolant flow channel and the inner cavity of the shell.

[0010] Preferably, there are three first side connecting holes in total, and the center lines of the first side connecting holes are collinear with the center lines of the gaps between the short sides of the cross sections of adjacent pitted heat dissipation tubes, that is, the first side connecting holes are directly opposite to the gaps between the adjacent pitted heat dissipation tube bundles.

[0011] Preferably, a second upper corner connecting hole is provided at the corner on the other side of the shell away from the water inlet of the shell, and a second lower corner connecting hole is provided at the corner close to the water inlet of the shell; at least one second side connecting hole is provided between the second upper corner connecting hole and the second lower corner connecting hole, and the second side connecting hole is provided on the inner side wall of the shell away from the water inlet of the shell; the second upper corner connecting hole, the second lower corner connecting hole and the second side connecting hole connect the second coolant flow channel and the inner cavity of the shell.

[0012] Preferably, there are three second side connecting holes, and the center lines of the second side connecting holes are collinear with the center lines of the gaps between the short sides of the cross sections of adjacent pitted heat dissipation tubes, that is, the second side connecting holes are directly opposite to the gaps between the adjacent pitted heat dissipation tube bundles.

[0013] Preferably, the first coolant flow channel and the second coolant flow channel are both in an "L" structure, and are combined with each other to form a connected "U"-shaped coolant flow channel; the water inlet of the shell is connected to the water inlets of the first coolant flow channel and the second coolant flow channel.

[0014] Preferably, at the location of the coolant flow channel, the shell wall is thickened; the diameter of the coolant flow channel is φ10.

[0015] Preferably, the corner connecting holes and the side connecting holes are waist-shaped holes, and the minimum distance from the mounting surface of the air inlet side of the shell is 2 mm.

[0016] Preferably, the pitted heat dissipation pipes 10 at the corners of the inner cavity of the shell 5 are removed.

[0017] The beneficial effects achieved by the present invention are as follows: a coolant flow channel is arranged along the cross-sectional direction of the shell at one end of the shell air inlet, and the water inlet of the coolant flow channel is connected to the shell water inlet; corners of the inner cavity of the shell are provided with corner connecting holes connected to the coolant flow channel, and the inner cavity side of the shell is provided with at least one side connecting hole connected to the coolant flow channel; when the coolant flows through the water inlet, a part of it will directly enter the inner cavity of the shell, and the other part will flow into a separate coolant flow channel, and then enter the inner cavity of the shell from the connecting holes at different positions to reach the designated high-risk boiling area for heat exchange.

[0018] The coolant passing through the coolant flow channel avoids the kinetic energy loss caused by collision and friction with the heat dissipation tube bundle, has good flow rate retention and relatively high penetration, and can introduce more coolant into the four rows of heat dissipation tubes away from the shell water inlet through the connecting holes, as well as the two corners of the shell close to the shell water inlet, i.e., the low flow rate field area, and enters the tube bundle from the gap between the heat dissipation tubes. The relatively high flow rate of the coolant significantly improves the uniformity of the flow field in these areas, ensures the heat exchange efficiency, suppresses the temperature rise of the heat exchange wall, and thereby reduces the failure risk in the high-incidence boiling area.

[0019] The multi-channel design of the coolant increases the flow area on the liquid side, and the coolant flowing into the coolant channel avoids collision and friction with the radiator bundle, so the overall liquid side resistance of the EGR cooler is reduced, more coolant can be obtained in the engine cooling circuit, and the boiling risk can be further reduced. The verification results show that: using the multi-channel design of the coolant, under the same working conditions, the liquid side resistance is reduced by 9%, and an additional flow of 10 to 20L / min can be obtained, which reduces the overall coolant boiling volume by 80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a multi-channel exhaust gas recirculation cooler of the present invention;

[0021] Figure 2 This is a schematic diagram of the assembly of the pitted heat pipe;

[0022] Figure 3 Schematic diagram of multi-channel design for shell coolant;

[0023] Figure 4 for Figure 3 A top view of

[0024] Figure 5 It is a schematic diagram of the structure of the multi-channel coolant on one side of the shell;

[0025] Figure 6 It is a schematic diagram of the structure of the multi-channel coolant on the other side of the shell;

[0026] Figure 7 for Figure 3A partial enlarged view of point A shown;

[0027] Figure 8 This is a comparison diagram of the current design CFD flow field and the actual boiling failure position;

[0028] Fig. 9 A comparison chart of CFD velocity field results between the current design and the multi-channel design of the present invention;

[0029] Fig.10 This is the current design CFD streamline field result diagram;

[0030] Fig.11 The CFD streamline field result diagram for the multi-channel design of the present invention;

[0031] Fig.12 This is a stress distribution diagram of the main intake plate of the EGR cooler subjected to thermal shock in the present invention;

[0032] In the figure: 1, air inlet chamber; 2, air inlet sealing gasket; 3, air inlet main plate; 4, air inlet sealing gasket; 5, shell; 6, air outlet sealing gasket; 7, air outlet main plate; 8, air outlet sealing gasket; 9, air outlet chamber; 10, pitting heat pipe; 11, shell water inlet; 12, shell water outlet; 13, first upper corner connecting hole; 14, first side connecting hole; 15, first lower corner connecting hole; 16, first coolant flow channel; 17, second upper corner connecting hole; 18, second side connecting hole; 19, second lower corner connecting hole; 20, second coolant flow channel;

[0033] Figures 9-11 This is the CFD flow field simulation result. Different colors in the result graph represent different flow velocities. Fig. 9 As shown in the flow rate scale, blue is the lowest flow rate, red is the highest flow rate, and the flow rate gradually increases from blue to red;

[0034] Figure 8 , Fig. 9 The selected sections for the coolant velocity field results shown are all located 1mm from the mounting surface on the air inlet side of the shell. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] like Figure 1As shown, an exhaust gas recirculation cooler with multiple coolant channels of the present invention comprises an air intake chamber 1, an air intake sealing gasket (2, 4), an air intake main plate 3, a shell 5, an air outlet sealing gasket (6, 8), an air outlet main plate 7, an air outlet chamber 9 and a pitted heat dissipation pipe 10, wherein the pitted heat dissipation pipe 10 is an exhaust gas channel, and the number of the pitted heat dissipation pipes 10 is usually 50 to 80, and the pitted heat dissipation pipes 10 are evenly distributed in the shell 5 at equal intervals; the air intake main plate 3 and the air outlet main plate 7 are respectively arranged at both ends of the shell 5, the air intake main plate 3 is close to the water inlet 11, and the air outlet main plate 7 is close to the water outlet 12; the same number of square holes are opened on the air intake main plate 3 and the air outlet main plate 7, and the inner contour of the square hole is consistent with the pitted heat dissipation pipe The outer contour of 10 is the same, the heat dissipation pipe 10 is connected between the air intake main plate 3 and the air outlet main plate 7 at both ends, and the number of heat dissipation pipes 5 corresponds to the square holes. After the pockmarked heat dissipation pipe 10 is inserted into the square holes corresponding to the air intake main plate 3 and the air outlet main plate 7 on both sides, the pockmarked heat dissipation pipe 5 is assembled with the air intake main plate 3 and the air outlet main plate 7 and fixed by laser welding. The laser welding trajectory is the matching gap between each pockmarked heat dissipation pipe 10 and the square hole of the main plate (the air intake main plate 3 and the air outlet main plate 7); the short side of the cross section of the pockmarked heat dissipation pipe 10 faces the water inlet, that is, after the coolant enters the shell 5 from the water inlet 11, it enters the tube bundle from the gap on the short side of the pockmarked heat dissipation pipe 5 for heat exchange. An intake sealing gasket 2 is installed between the intake main plate 3 and the intake chamber 1, and an intake sealing gasket 4 is installed between the intake main plate 3 and the shell 5, and the whole is fixed by bolts; similarly, an outlet sealing gasket 6 is installed between the outlet main plate 7 and the shell 5, and an outlet sealing gasket 8 is installed between the outlet main plate 7 and the outlet chamber 9, and the whole is fixed by bolts.

[0037] Combination Figure 2-7As shown, in this embodiment, a coolant flow channel is provided along the cross-sectional direction of the shell 5 at one end of the air inlet of the shell 5 (i.e., the end close to the shell water inlet 11), and the water inlet of the coolant flow channel is connected to the shell water inlet 11; corner connecting holes (13, 15, 17, 19) connected to the coolant flow channel are provided at the corners of the inner cavity of the shell 5, and at least one side connecting hole (14, 18) connected to the coolant flow channel is provided on the side of the inner cavity of the shell 5. When the coolant flows through the water inlet, a part of it will directly enter the inner cavity of the shell 5, and the other part will flow into a separate coolant flow channel, and then enter the inner cavity of the shell 5 from the connecting holes (13, 14, 15, 17, 18, 19) at different positions, and reach the designated high-risk boiling area for heat exchange. The coolant passing through the coolant flow channel avoids the kinetic energy loss caused by collision and friction with the pockmarked heat dissipation tube 10, has good flow velocity retention and relatively high penetration, and more coolant can be introduced into the pockmarked heat dissipation tube 10 area away from the shell water inlet 11 and the shell 5 corner close to the shell water inlet 11, that is, the low flow velocity field area, through the connecting hole, and enters the tube bundle from the gap between adjacent pockmarked heat dissipation tubes 10. The relatively high flow velocity of the coolant significantly improves the uniformity of the flow field in these areas, ensures the heat exchange efficiency, suppresses the temperature rise of the heat exchange wall, and thereby reduces the failure risk of the boiling high-incidence area.

[0038] In this embodiment, the shell 5 is a square cylindrical structure with left and right openings, the left side is the air inlet side, and the right side is the air outlet side. The shell water inlet 11 is arranged at the bottom of the shell 5 near the air inlet side. The coolant flow channel is arranged on the left side of the shell, the water inlet is connected with the shell water inlet 11, and the water outlet is connected with the inner cavity of the shell 5 through the corner connecting holes (13, 15, 17, 19) and the side connecting holes (14, 18); the inner cavity of the shell 5 has four corners (two at each end), so there are four corner connecting holes (13, 15, 17, 19) connected with the coolant flow channel in the shell 5.

[0039] In this embodiment, the coolant flow channel includes a first coolant flow channel 16 and a second coolant flow channel 20. The first coolant flow channel 16 is arranged on one side of the shell, and the second coolant flow channel 20 is arranged on the other side of the shell. After the coolant enters the coolant flow channel through the shell water inlet 11, it is divided into three parts, one part of which directly enters the inner cavity of the shell 5, and the remaining two parts: one part enters the first coolant flow channel 16 to cool the shell, and the other part enters the second coolant flow channel 20 to cool the shell.

[0040] In this embodiment, a first upper corner connecting hole 13 is provided at a corner away from the shell water inlet 11 on one side of the shell 5, and a first lower corner connecting hole 15 is provided at a corner close to the shell water inlet 11; at least one first side connecting hole 14 is provided between the first upper corner connecting hole 13 and the first lower corner connecting hole 15, and the first side connecting hole 14 is provided on the inner side wall of the shell away from the shell water inlet 11; the first upper corner connecting hole 13, the first lower corner connecting hole 15 and the first side connecting hole 14 are connected to the first coolant flow channel 16 and the inner cavity of the shell 5.

[0041] In the present embodiment, there are three first side connecting holes 14, which are evenly distributed, and the distance between two adjacent first side connecting holes 14 is 15 mm; the center line of the first side connecting hole 14 is collinear with the center line of the short side gap of the cross section of the adjacent pockmarked heat dissipation tube 10, that is, the first side connecting hole 14 is directly opposite to the tube bundle gap of the adjacent pockmarked heat dissipation tube 10.

[0042] In this embodiment, a second upper corner connecting hole 17 is provided at the corner on the other side of the shell away from the shell water inlet 11, and a second lower corner connecting hole 19 is provided at the corner close to the shell water inlet 11; at least one second side connecting hole 18 is provided between the second upper corner connecting hole 17 and the second lower corner connecting hole 19, and the second side connecting hole 18 is provided on the inner wall of the shell away from the shell water inlet 11; the second upper corner connecting hole 17, the second lower corner connecting hole 19 and the second side connecting hole 18 are connected to the second coolant flow channel 20 and the inner cavity of the shell 5.

[0043] In the present embodiment, there are three second side connecting holes 18, which are evenly distributed, and the distance between two adjacent second side connecting holes 18 is 15 mm; the center line of the second side connecting hole 18 is collinear with the center line of the short side gap of the cross section of the adjacent pockmarked heat dissipation tube 10, that is, the second side connecting hole 18 is directly opposite to the tube bundle gap of the adjacent pockmarked heat dissipation tube 10.

[0044] In this embodiment, the first coolant flow channel 16 and the second coolant flow channel 20 are both in an "L" structure, and are combined with each other to form a connected "U"-shaped coolant flow channel; the shell water inlet 11 is arranged on the symmetry axis of the first coolant flow channel 16 and the second coolant flow channel 20 (the water inlet 11 is actually not on the standard symmetry axis of the flow channel 16 and the flow channel 20, and its position is slightly deviated from the axis, and there is no technical limitation on the horizontal position of the shell water inlet 11, that is, slightly deviating from the center can also achieve the desired effect), and both are connected to the water inlets of the first coolant flow channel 16 and the second coolant flow channel 20.

[0045] In the present embodiment, the first upper corner connecting hole 13, the first lower corner connecting hole 15 and the first side connecting hole 14, and the second upper corner connecting hole 17, the second lower corner connecting hole 19 and the second side connecting hole 18 are all waist-shaped holes, and the minimum distance from the mounting surface of the air intake side of the shell 5 is 2 mm. The main purpose is to allow the coolant flowing out of the connecting holes to flow to the high-temperature air intake main plate 3 as much as possible to enhance the heat exchange effect.

[0046] In this embodiment, the wall of the housing 5 is thickened at the location of the coolant flow channel; the diameter of the coolant flow channel is φ10. According to the FEA modal and sample DV vibration test results: adding the coolant flow channel and the waist-shaped hole has no effect on the structural strength of the EGR cooler.

[0047] In this embodiment, the distribution characteristics of the pitted heat dissipation pipes 10 in the housing 5 are as follows: Figure 3 As shown in the figure, the four pitted heat pipes at the four corners of the heat pipe group are removed, and the assembly positions corresponding to the air intake main plate 3 and the air outlet main plate 7 are not provided with punched square holes, and the remaining pitted heat pipes are distributed at equal intervals. According to the FEA thermal shock simulation results, the weld area at the four corners of the heat pipe bundle and the air intake main plate 3 is the thermal stress concentration area, and the stress at the "R" corner of the weld is the largest, as shown in the figure. Fig.12 As shown in the figure, different colors represent different stress areas, red is the maximum stress. Removing the heat pipes at the four corners can eliminate the thermal stress concentration points on the intake main chip and reduce the overall thermal stress amplitude. According to the SN (stress-life) curve description, reducing the stress amplitude of the cyclic load can improve the thermal fatigue life. The results of thermal shock simulation and bench verification show that removing the pitted heat pipes 10 at the corners increases the thermal shock resistance life of the EGR cooler by 70%; further, by removing four pitted heat pipes 10, the gas side flow channel corresponding to the original heat pipe becomes a liquid side flow channel, that is, the flow area on the liquid side of the EGR cooler is increased, the pressure resistance of the coolant is reduced, and the EGR cooler can obtain more coolant in the engine cooling circuit, thereby improving the heat exchange efficiency of the high-temperature circulating exhaust gas. At the same time, the coolant flow field distribution and flow velocity in the area near the shell water inlet 11 on the hot side of the shell 5 are guaranteed, and the blind area of ​​the coolant distribution on the high-temperature side is further reduced, which can reduce the local boiling risk of the EGR cooler. The performance-pressure drop bench verification shows that after removing the pitted heat pipes 10 at the four corners, the pressure drop on the coolant side can be reduced by about 9%, and the outlet gas temperature is only increased by 1°C, which meets the heat exchange performance requirements. The CFD simulation results show that after removing the heat pipes at the four corners, the boiling volume can be reduced by 58%.

[0048] In this embodiment, the surface of the pitted heat dissipation tube 10 is evenly distributed with "eight"-shaped grooves and conical protrusions along the tube length direction, and the grooves and protrusions are evenly distributed along the tube length direction in the form of two alternating combination units.

[0049] In this embodiment, the material of the air inlet sealing pads (2, 4) and the air outlet sealing pads (6, 8) are both 0.25 mm thick stainless steel, and are provided with 0.025 mm thick fluororubber coating on both sides.

[0050] In this embodiment, the air intake chamber 1 adopts a double flow channel inlet, each flow channel is connected to three exhaust manifold interfaces, and a baffle is cast in the air intake chamber 1 to ensure that the double flow channels independently pass exhaust gas.

[0051] The existing EGR coolers all use a single-channel water inlet, that is, the coolant directly enters the inner cavity of the shell 5 through the water inlet, flows around the heat dissipation pipe for heat exchange, and reduces boiling failure mainly by reasonably designing the internal shape of the shell water inlet 11 and the volume of the inner cavity of the shell 5: optimize the coolant flow field on the high-temperature side to make the coolant more evenly distributed on the high-temperature side, ensure the flow rate and reduce the blind area of ​​the flow field, enhance heat exchange and reduce the risk of boiling, but the improvement effect of optimizing the shell water inlet 11 and the inner cavity of the shell 5 is limited, especially at the end far away from the water inlet. Due to the influence of the heat dissipation pipe bundle flow resistance, it is inevitable that there will be a liquid side blind area or a low flow rate area, and it is more obvious when the shell water inlet 11 is located below the EGR cooler. The low-speed field area and blind area of ​​the coolant will cause the liquid side temperature to continue to rise until boiling, and local film boiling is the majority. The bubbles generated by film boiling will cause a vacuum area to form on the heat exchange wall of the heat dissipation pipe, isolating the heat exchange wall and the coolant, which will greatly reduce the heat exchange performance. In severe cases, it will accelerate the fatigue cracking of the heat dissipation pipe, resulting in gas-liquid communication.

[0052] Figure 8 The figures are the CFD velocity field simulation results of the water inlet side of the EGR cooler and the boiling failure performance in the terminal market, where the coolant flows in a "bottom-in and bottom-out" manner, that is, the shell water inlet 11 and the shell water outlet 12 are both located below the shell 5. From the CFD flow field simulation results, it can be concluded that the low velocity field is located in the area far away from the shell water inlet 11, which is consistent with the actual failure position, and the failure mode is mostly the cracking of the heat pipe. Therefore, how to improve the liquid side velocity field in the far water inlet area (far away from the shell water inlet 11 water inlet area) and reduce the distribution blind area is the key to reducing the boiling failure of the EGR cooler.

[0053] In this embodiment, additional independent coolant flow channels (first coolant flow channel 16 and second coolant flow channel 20) are opened on both sides of the bottom of the water inlet 11 of the EGR cooler, and connecting holes (13, 14, 15, 17, 18, 19) are provided on the coolant flow channel on the side facing the inner cavity of the shell 5, and the connecting holes connect the inner cavity of the shell 5 and the coolant flow channel, the first upper corner connecting hole 13 and the first lower corner connecting hole 15 are respectively close to the inside of the shell 5, and the first side connecting hole 14 is at the far water outlet end and is directly opposite to the gap between the adjacent pitted heat dissipation pipes 10 at the location. When the coolant flows through the shell water inlet 11, a part of it will directly enter the inner cavity of the shell 5, and the other part will flow into the first coolant flow channel 16 and the second coolant flow channel 20, and then enter the inner cavity of the shell 5 from the connecting holes at different positions to reach the designated high-risk boiling area for heat exchange. The coolant passing through the first coolant flow channel 16 and the second coolant flow channel 20 avoids the kinetic energy loss caused by the collision and friction between the coolant and the heat dissipation tube bundle, has good flow velocity retention and relatively high penetration. More coolant can be introduced into the four rows of heat dissipation tubes away from the water inlet and the four corners of the shell 5 close to the shell water inlet 11, that is, the low flow velocity field area, through the connecting holes (13, 14, 15, 17, 18, 19), and enters the tube bundle from the adjacent pockmarked heat dissipation tube 10. The relatively high flow velocity of the coolant significantly improves the uniformity of the flow field in this area.

[0054] Take the two upper corners of the housing 5 (the first upper corner connecting hole 13 and the second upper corner connecting hole 17) as an example. Fig. 9 As shown, the design of the coolant multi-channel significantly improves the flow rate of the upper corner blind area, enhances the heat exchange efficiency of the high boiling risk point, reduces the maximum temperature of the heat exchange wall, and inhibits the occurrence of film boiling; similarly, more coolant can be introduced into the two corner areas of the inner cavity of the shell 5 near the shell water inlet 11 through the first lower corner connecting hole 15 and the second lower corner connecting hole 19, thereby improving the liquid side flow rate in this area and reducing the risk of film boiling;

[0055] Fig. 9 The CFD velocity field simulation results for the current coolant flow channel design and multi-flow channel design of the EGR cooler. Fig. 9 (a) is of current design, Fig. 9(b) is designed for the present invention, and the flow field sections are all taken at a position of 1 mm away from the mounting surface of the air inlet side of the shell. It can be seen that by using the coolant multi-channel design of the present invention, the uniformity of the coolant flow field is significantly improved, and the coolant flow rate of the heat dissipation tube bundle away from the water inlet and the four corners of the shell is greatly improved, the heat exchange efficiency is guaranteed, and the temperature rise of the heat exchange wall surface is suppressed, thereby reducing the failure risk of the high-incidence area of ​​boiling;; Further, the design of the coolant multi-channel increases the liquid side flow area, and the coolant flowing into the first coolant channel 16 and the second coolant channel 20 avoids collision and friction with the heat dissipation tube bundle, so the overall liquid side resistance of the EGR cooler is reduced, more coolant can be obtained in the engine cooling circuit, and the boiling risk can be further reduced. The verification results show that: by using the coolant multi-channel design, under the same working conditions, the liquid side resistance is reduced by 9%, and an additional flow of 10 to 20 L / min can be obtained, which reduces the overall boiling volume of the coolant by 80%.

[0056] Fig.10 and Fig.11 They are the CFD liquid side streamline field results of the current coolant flow channel design and multi-flow channel design of the EGR cooler. Fig.10 For current design, Fig.11 For the design of the present invention, it can be seen that the results of the CFD liquid side streamline field correspond to the flow velocity field. Compared with the existing structure, the multi-channel design of the coolant of the present invention makes the coolant on the far water inlet side more distributed and has a higher flow rate, which further illustrates the principle of reducing the boiling risk by the multi-channel design;

[0057] The above shows and describes the basic principles and main structural features of the present invention. The present invention is not limited to the above examples. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. An exhaust gas recirculation cooler with multiple coolant channels, characterized in that: The invention comprises a shell (5), wherein one end of the air inlet of the shell (5) is provided with a coolant flow channel arranged along the cross-sectional direction of the shell (5), and the water inlet of the coolant flow channel is connected to the water inlet (11) of the shell; corners of the inner cavity of the shell (5) are provided with corner connecting holes connected to the coolant flow channel, and the inner cavity side of the shell (5) is provided with at least one side connecting hole connected to the coolant flow channel.

2. The exhaust gas recirculation cooler with multiple coolant channels according to claim 1, characterized in that: The coolant flow channel comprises a first coolant flow channel (16) and a second coolant flow channel (20), wherein the first coolant flow channel (16) is arranged on one side of the shell (5), and the second coolant flow channel (20) is arranged on the other side of the shell (5).

3. The exhaust gas recirculation cooler with multiple coolant channels according to claim 2, characterized in that: A first upper corner connecting hole (13) is provided at a corner of one side of the shell (5) away from the shell water inlet (11), and a first lower corner connecting hole (15) is provided at a corner close to the shell water inlet (11); at least one first side connecting hole (14) is provided between the first upper corner connecting hole (13) and the first lower corner connecting hole (15), and the first side connecting hole (14) is provided on the inner wall of the shell (5) away from the shell water inlet (11); the first upper corner connecting hole (13), the first lower corner connecting hole (15) and the first side connecting hole (14) are connected to the first coolant flow channel (16) and the inner cavity of the shell (5).

4. The exhaust gas recirculation cooler with multiple coolant channels according to claim 2, characterized in that: There are three first side connecting holes (14) in total, and the center lines of the first side connecting holes (14) are collinear with the center lines of the short side gaps of the cross sections of adjacent pitted heat dissipation tubes (10), that is, the first side connecting holes (14) face the tube bundle gaps of adjacent pitted heat dissipation tubes (10).

5. The exhaust gas recirculation cooler with multiple coolant channels according to claim 2 or 3, characterized in that: A second upper corner connecting hole (17) is provided at a corner of the other side of the shell (5) away from the shell water inlet (11), and a second lower corner connecting hole (19) is provided at a corner close to the shell water inlet (11); at least one second side connecting hole (18) is provided between the second upper corner connecting hole (17) and the second lower corner connecting hole (19), and the second side connecting hole (18) is provided on the inner wall of the shell (5) away from the shell water inlet (11); the second upper corner connecting hole (17), the second lower corner connecting hole (19) and the second side connecting hole (18) are connected to the second coolant flow channel (20) and the inner cavity of the shell (5).

6. The exhaust gas recirculation cooler with multiple coolant channels according to claim 5, characterized in that: There are three second side connecting holes (18) in total, and the center lines of the second side connecting holes (18) are collinear with the center lines of the short side gaps of the cross sections of adjacent pitted heat dissipation tubes (10), that is, the second side connecting holes (18) are directly opposite to the tube bundle gaps of adjacent pitted heat dissipation tubes (10).

7. The exhaust gas recirculation cooler with multiple coolant channels according to claim 2, characterized in that: The first coolant flow channel (16) and the second coolant flow channel (20) are both in an "L" structure and are combined to form a connected "U"-shaped coolant flow channel; the shell water inlet (11) is connected to the water inlets of the first coolant flow channel (16) and the second coolant flow channel (20).

8. The exhaust gas recirculation cooler with multiple coolant channels according to claim 1, characterized in that: At the location of the coolant flow channel, the wall surface of the shell (5) is thickened; the diameter of the coolant flow channel is φ10.

9. The exhaust gas recirculation cooler with multiple coolant channels according to claim 1, characterized in that: The corner connecting holes and the side connecting holes are both waist-shaped holes, and the minimum distance from the air inlet side mounting surface of the shell (5) is 2 mm.

10. The exhaust gas recirculation cooler with multiple coolant channels according to claim 1, characterized in that: The pitted heat dissipation pipes (10) at the corners of the inner cavity of the shell (5) are all removed.

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