GB1579275A

GB1579275A - Heat exchanger for cooling exhaust gas

Info

Publication number: GB1579275A
Application number: GB26182/77A
Authority: GB
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1976-08-23
Filing date: 1977-06-22
Publication date: 1980-11-19
Also published as: JPS6133972B2; JPS6223236B2; DE2733215A1; SE8303353L; GB1579276A; SE7708696L; CA1090778A; DE2733215C3; FR2363073A1; DE2733215B2; DE2759785C2; SE429675B; FR2363073B1; SE8303353D0; JPS5325717A; AU518454B2; AU2655677A; JPS6183881A

Description

(54) HEAT EXCHANGER FOR COOLING EXHAUST GAS (71) We, BORG-WARNER CORPORA TION, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of 200 South Michigan Avenue, Chicago, State of Illinois 60604, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to exhaust gas recirculation in the automotive internal combustion engine and more particularly to a heat exchanger for cooling the exhaust gas that is returned to the combustion cycle.

Since approximately 1971, automotive vehicle manufacturers have been required to add an ever-increasing number of components or systems to the vehicle or to the internal combustion engine therein to increase the safety of the vehicle or decrease the emissions inherent in the exhaust gases from the internal combustion engine. Such components include positive crankcase ventilation, exhaust gas recirculation, an evaporation control system and a catalytic converter in the exhaust line.

Of major concern is the emissions from the exhaust gas of an internal combustion cycle which have been blamed for conditions such as smog occurring in large cities where a large number of automobiles are present each day. The oxides of nitrogen are one such emission, and an exhaust gas recirculation cycle is used to reduce these oxides present in the engine exhaust.

Formation of nitrogen oxides takes place at very high temperatures and consequently occurs during the peak temperature period of the combustion process. To reduce and control nitrogen oxides formation, only a slight reduction in peak temperature is required.

This temperature reduction can be accomplished by introducing small amounts of an inert gas into the combustion process and, as the end products of combustion provide a continuous supply of relatively inert gases, it becomes a matter of utilizing those gases in the correct proportion. Thus, a recirculation passage is complected to the exhaust manifold and to a vacuum modulated shut-off and metering valve installed on the inlet manifold to control the flow of exhaust gases. The recirculation or additional exhaust gas passages are closely positioned to the engine or may be cast into the complex runner system of the inlet manifold.

However, the exhaust gases from the internal combustion engine cycle are still at a very high temperature level and it is desirable to substantially reduce that temperature level before the gases are reintroduced into the combustion cycle. The present invention is directed at providing a heat exchanger for use in obtaining this desired temperature reduction.

The present invention comprehends the provision of a heat exchanger to be inserted in the exhaust gas recirculation system of an automotive internal combustion engine to cool the recirculating exhaust gases before reintroduction into the inlet manifold. The heat exchanger is of a compact design to fit within the relatively crowded space in the engine compartment of the vehicle and to be easily mounted on the engine without substantially increasing the flow path of the recirculating gases.

According to the present invention there is provided a gas-to-liquid heat exchanger for use in cooling of recirculating exhaust gas in an internal combustion engine, comprising an inner exhaust gas chamber enclosed within a generally flat outer cooling liquid envelope, said inner chamber being formed of an inner pair of dished plates joined by peripheral flanges, having a gas inlet and a gas outlet extending therefrom, said inlet and outlet communicating with a cavity between said dished plates which includes at least one metal plate defining a heat transfer surface within said chamber, said peripheral flanges including openings adjacent opposite end portions of said chamber, said envelope being formed of an outer pair of dished plates encompassing said chamber and having flanges joined to said chamber beyond said openings, one of said outer dished plates having a central depression extending transversely of said envelope disposed between said end portions of said chamber dividing said envelope into inlet and outlet portions, said one outer dished plate further including a cooling liquid inlet located to one side of said depression and a cooling liquid outlet located to the other side of said depression, said liquid inlet, outlet, depression and openings directing flow of cooling liquid from said depression along one surface of said chamber toward an end portion, through said flange openings, thence along an opposite surface of said chamber and through other of said flange openings and then along said one surface of said chamber toward said depression thus circulating liquid around said chamber.

In one embodiment said gas inlet and outlet are positioned adjacent the opposite ends of the heat exchanger, said inner and outer flanges on the side of the heat ex changes receiving said gas inlet and outlet include embossments around the inlet and the outlet, and said chamber has an inlet portion and an outlet portion aligned with said gas inlet and outlet, and said metal plate is pleated and extends longitudinally between said inlet and outlet chamber portions.

In another embodiment said liquid inlet and outlet are located in one outer dished plate adjacent the central depression, and said gas inlet and outlet are centrally located in said same outer dished plate and extending through said outer dished plate at the opposite sides of the heat exchanger adjacent terminal portions of the central depression, said gas inlet and outlet each being defined by flared portions of said adjacent inner and outer dished plates which are crimped together. The heat exchanger is formed of suitable materials to resist corrosion and decay in the highly corrosive exhaust gas environment.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a heat exchanger for cooling exhaust gas; Figure 2 is a vertical cross-sectional view taken on the line 5-5 of Figure 1; Figure 3 is a partial vertical crosssectional view taken on the irregular line 6-6 of Figure 1; Figure 4 is a top plan view of a second embodiment of heat exchanger; Figure 5 is a vertical cross-sectional view taken on the line 8-8 of Figure 4; Figure 6 is a partial vertical crosssectional view taken on the line 9-9 of Figure 4; Figure 7 is a top plan view of a third embodiment of heat exchanger; Figure 8 is a vertical cross-sectional view taken on the line 11-11 of Figure 7; Figure 9 is a partial vertical crosssectional view taken on the line 12-12 of Figure 7.

Figures 1 to 3 disclose a liquid-to-gas heat exchanger 31 having a generally flat con figuraticn which will easily and compactly fit alongside the vehicle engine in the limited space of the engine compartment. This heat exchanger is formed from four stamped pieces of sheet metal comprising a pair of syminetrical inner sheets 32, 32a and a pair of generally identical outer pieces 47, 47a the inner pieces having flat flanges 33, 33a around three sides of the unit and generally flat flanges 34, 34a on the fourth side provided with two pairs of oppositely disposed embcssments 35, 35a; the embossments 35 extending above the plane of the flanges 34, 34a and the other embossment 35a extending below the flange plane.

The pieces 32, 32a have oppositely dished central portions 36, 36a with generally vertical side walls 37, 37a merging into the flanges 33 and converging away from the walls 38, 38a merging into the flanges 34.

The walls 37, 37a converge toward walls 39, 39a parallel to and opposite the wall 38.

Generally conical embossments 40, 40a are formed in the central portions 36, 36a and merge into the embossments 35, 35a to define openings for an inlet conduit 41 and an outlet conduit 42. The conical embossments 40, 40a also merge into the sheets 32, 32a as seen in Figure 2. Within a central chamber 43 formed by the dished portions 36, 36a, is positioned a partially folded turbulizer 44 extending longitudinally in the chamber to divide the chamber into a plurality of parallel flow passages 45; the turbulizer terminating short of the ends of the chamber to form an entrance tank 46 and an exit tank (not shown) for the exhaust gas.

The outer pieces 47, 47a also have flat flanges 48, 48a sandwiching the flanges 33, 33a around three sides of the heat exchanger and generally flat flanges 49, 49a sandwiching the flanges 34, 34a on the fourth side.

Conical embossments 50, 50a are formed in central dished portions 52, 52a defined by the flanges 48, 48a, 49, 49a with outer edges 51, 51a engaging and secured to the embossments 35, 35a. The dished portions 52, 52a have side walls 53, 53a converging from a rear wall 54, 54a having the embossments therein and toward forward walls 55, 55a parallel to the walls 54, 54a; the walls being spaced outwardly of the walls of the inner dished portions 36, 36a. A central indentation 56 in the dished portion 52 engages its respective inner dished portion 36 to divide the upper portion of the fluid envelope 57 formed between the dished portions 36, 36a, 52, 52a to cause flow of the cooling fluid into the lower envelope portion.

The flanges 33 of the inner sheets 32, 32a, as seen in Figures 2 and 3, act to divide the fluid envelope 57 into upper and lower portions; however, fluid ports or openings 58 are formed in the oppositely disposed flanges 33 at the opposite ends of the inner pieces to allow fluid communication and flow between the upper and lower portions of the envelope. A cooling fluid inlet conduit 59 and a fluid outlet conduit 60 are secured in the upper piece 52 adjacent the indentation 56; the conduits communicating with the upper portion of the fluid envelope 57. As shown by the arrows in Figure 1, the hot exhaust gas enters the conduit 41 (arrow A) into the entrance tank 46, passes through the parallel passages 44 to the exit tank, and the cooled gas leaves through the conduit 42 (arrow B).The cooling water enters conduit 59 (arrow C) into the communicating half of the upper portion of the envelope 57 passes down through the openings 58 to the lower envelope portion, flows across the lower portion and up through the opposite set of openings 58 to the other half of the upper envelope portion and exits through the conduit 60 (arrow D) to cool the exhaust gas.

Figures 4, 5 and 6 disclose a second embodiment of heat exchanger 61 having a generally rectangular symmetrical configuration. This device includes a pair of inner metal sheets 62, 62a having parallel side flanges 63 and curved end flanges 64; the sheets having oppositely dished portions 65, 65a with dished end extensions 66, 66a.

The dished portions 65, 65a form a central chamber 67 for the exhaust gases, with the extensions 66, 66a forming inlet and outlet chambers. An elongated opening 68 in the extension 66 forms an inlet port and an elongated opening 69 forms the outlet port in the opposite extension 66.

A pair of outer sheets 71, 71a have flanges 72 engaging the flanges 63 (see Figure 5) and flanges 73 engaging the dished extension 66, 66a (Figure 6); the sheets having oppositely dished portions 74, 74a cooperating with the dished portions 65, 65a to provide a cooling fluid envelope around the chamber 67. As seen in Figure 5, the walls 75 of dished portions 65, 65a are spaced inwardly of the walls 76 of dished portions 74, 74a with the side flanges 63 dividing the fluid envelope into upper and lower portions 77 and 78, respectively, and provided with openings 79 formed therein to provide communication between these two portions. Embossments 80 are preferably formed in the sheets 71, 71a to extend into the cooling fluid envelope.

The sheet 71 has a fluid inlet conduit 81 formed in the dished portion 74 on one side of a central depression 82 and a fluid outlet conduit 83 adjacent the opposite side of the depression. The central transverse elongated depression 82 is formed across the dished portion 74 and extends inwardly to contact and be joined to the dished portion 65 of the upper sheet 62. This depression 82 effectively divides the upper envelope portion 77 in half to provide the desired flow pattern for the fluid.

In use, the hot exhaust gas enters the inlet port 68 in the inlet chamber and passes into the central chamber where a partially folded metal sheet 84 forms a plurality of flow passages 85. The cooled gas flows into the outlet chamber and exits through the port 69. Also, the cooling fluid, such as water, enters the upper portion 77 of the envelope via the conduit 81, but is stopped from directly flowing to the outlet conduit 83 by the depression 82.

Thus, fluid flows from the upper portion through the openings 79 at the end 86 to the lower envelope portion 78, across the portion 78 to the openings 79 at the end 87 and enters the upper envelope portion 77 again to exit through the outlet conduit 83. The ribs or embossments 80 formed in the dished portions 71, 71a (see Figure 5) act to interrupt straight flow of the fluid in the envelope and turbulize the fluid to enhance the heat transfer and reduce any channelling of the flow of the cooling fluid.

Figures 7 to 9 disclose another heat exchanger 91 similar to that shown in Figures 4 to 6 except for the positioning of the exhaust gas inlet and outlet. This heat exchanger 91 utilizes a pair of inner plates 92, 92a having flanges 93 around the periphery and defining oppositely disposed dished portions 94, 94a forming a central chamber 95. Outer metal sheets 96, 96a have peripheral flanges 97 and oppositely dished portions 98, 98a. As seen in Figure 8, the exhaust gas inlet 99 and the exhaust gas outlet 101 are formed through both sheets 92, 96, with the sheets being crimped together to form the conduits. A partially folded metal plate 102 is positioned in the chamber 95 to divide the flow of hot gases and enhance heat transfer to the cooling fluid in the surrounding envelope.

The spacing between the dished portions forms a fluid envelope having an upper portion 103 and a lower portion 104. An elongated central depression or rib 105 is formed in the sheet 96 and engages the inner sheet 92 to divide the upper envelope portion 103 to two compartments; a fluid inlet conduit 106 in sheet 96 communicates with the compartment on one side of the rib 105 and the fluid outlet conduit 107 communicates with the opposite compartment. A plurality of openings 108 are formed in the flanges 93 between the spaced walls of the dished portions 92, 92a and 98, 98a adjacent the conduit 106 and a second set of openings 109 are formed in the flanges 93 adjacent the outlet conduit 107. The flow of hot exhaust gas and cooling water takes substantially the same paths as for the heat exchanger 61.

Obviously, in the various illustrated embodiments, the water connections would be positioned in the outer envelope to provide the most effective distribution and circulation of the cooling fluid; and the folded metal sheet in the inner chamber acts to break up the hot gas flow into smaller streams to effectively maximize the heat transfer from the exhaust gas to the cooling fluid in the envelope. Also, the flow of cooling fluid can be either concurrent or counter current to the gas flow, with the cooling fluid jacket shielding a very localized but high temperature zone.

WHAT WE CLAIM IS: 1. A gas-to-liquid heat exchanger for use in cooling of recirculating exhaust gas in an internal combustion engine, comprising an inner exhaust gas chamber enclosed within a generally flat outer cooling liquid envelope, said inner chamber being formed of an inner pair of dished plates joined by peripheral flanges, having a gas inlet and a gas outlet extending therefrom, said inlet and outlet communicating with a cavity between said dished plates which includes at least one metal plate defining a heat transfer surface within said chamber, said peripheral flanges including openings adjacent opposite end portions of said chamber, said envelope being formed of an outer pair of dished plates encompassing said chamber and having flanges joined to said chamber beyond said openings, one of said outer dished plates having a central depression extending transversely of said envelope disposed between said end portions of said chamber dividing said envelope into inlet and outlet portions, said one outer dished plate further including a cooling liquid inlet located to one side of said depression and a cooling liquid outlet located to the other side of said depression, said liquid inlet, outlet, depression and openings directing flow of cooling liquid from said depression along one surface of said chamber toward an end portion, through said flange openings, thence along an opposite surface of said chamber and through other of said flange openings and then along said one surface of said chamber toward said depression thus circulating liquid around said chamber.

2. A gas-to-liquid heat exchanger as claimed in claim 1, in which said gas inlet and outlet are positioned adjacent the opposite ends of the heat exchanger, said inner and outer flanges on the side of the heat exchanger receiving said gas inlet and outlet include embossments around the inlet and the outlet, and said chamber has an inlet portion and an outlet portion aligned with said gas inlet and outlet, and said metal plate is pleated and extends longitudinally between said inlet and outlet chamber portions.

3. A gas-to-liquid heat exchanger as claimed in claim 2, wherein said embossments in said inner and outer flanges merge into said inner and outer dished plates, respectively.

4. A gas-to-liquid heat exchanger as claimed in claim 1, wherein said inner chamber is provided with oppositely disposed extensions projecting through the side of the outer flanges, and said gas inlet and outlet are located in said extensions.

5. A gas-to-liquid heat exchanger as claimed in claim 4, wherein said inner extensions are located on two parallel sides of said heat exchanger, and the two outer dished plates extend beyond the inner dished plates on the two parallel ends of said heat exchanger.

6. A gas-to-liquid heat exchanger as claimed in claim 5, in which gas flow in said inner chamber is generally transverse to the flow of cooling liquid in said outer envelope.

7. A gas-to-liquid heat exchanger as set forth in claim 6, including a plurality of flow diverting ribs formed on said outer dished plates and projecting towards said chamber.

8. A gas-to-liquid heat exchanger as set forth in claim 1, in which said liquid inlet and outlet are located in one outer dished plate adjacent the central depression, and said gas inlet and outlet are centrally located in said same outer dished plate and extending through said outer dished plate at the opposite sides of the heat exchanger adjacent terminal portions of the central depression, said gas inlet and outlet each being defined by flared portions of said adjacent inner and outer dished plates which are crimped together.

9. A gas-to-liquid heat exchanger constructed and arranged to operate substantially as hereinbefore described with reference to and as shown by Figures 1 to 3, Figures 4 to 6 or Figures 7 to 9 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. rib 105 and the fluid outlet conduit 107 communicates with the opposite compartment. A plurality of openings 108 are formed in the flanges 93 between the spaced walls of the dished portions 92, 92a and 98, 98a adjacent the conduit 106 and a second set of openings 109 are formed in the flanges 93 adjacent the outlet conduit 107. The flow of hot exhaust gas and cooling water takes substantially the same paths as for the heat exchanger 61. Obviously, in the various illustrated embodiments, the water connections would be positioned in the outer envelope to provide the most effective distribution and circulation of the cooling fluid; and the folded metal sheet in the inner chamber acts to break up the hot gas flow into smaller streams to effectively maximize the heat transfer from the exhaust gas to the cooling fluid in the envelope. Also, the flow of cooling fluid can be either concurrent or counter current to the gas flow, with the cooling fluid jacket shielding a very localized but high temperature zone. WHAT WE CLAIM IS:

1. A gas-to-liquid heat exchanger for use in cooling of recirculating exhaust gas in an internal combustion engine, comprising an inner exhaust gas chamber enclosed within a generally flat outer cooling liquid envelope, said inner chamber being formed of an inner pair of dished plates joined by peripheral flanges, having a gas inlet and a gas outlet extending therefrom, said inlet and outlet communicating with a cavity between said dished plates which includes at least one metal plate defining a heat transfer surface within said chamber, said peripheral flanges including openings adjacent opposite end portions of said chamber, said envelope being formed of an outer pair of dished plates encompassing said chamber and having flanges joined to said chamber beyond said openings, one of said outer dished plates having a central depression extending transversely of said envelope disposed between said end portions of said chamber dividing said envelope into inlet and outlet portions, said one outer dished plate further including a cooling liquid inlet located to one side of said depression and a cooling liquid outlet located to the other side of said depression, said liquid inlet, outlet, depression and openings directing flow of cooling liquid from said depression along one surface of said chamber toward an end portion, through said flange openings, thence along an opposite surface of said chamber and through other of said flange openings and then along said one surface of said chamber toward said depression thus circulating liquid around said chamber.