TW201245569A - Exhaust train having an integrated thermoelectric generator - Google Patents

Abstract

In an exhaust train for an internal combustion engine having an integrated thermoelectric generator, the exhaust train has at least one duct, through which exhaust gas flows and in which at least one thermoelectric module is arranged in such a way that the hot side of the thermoelectric module is in direct contact with the exhaust gas, while the cold side of the thermoelectric module is cooled by means of a heat transfer medium.

Description

201245569 VI. Description of the Invention: TECHNICAL FIELD OF THE INVENTION The present invention relates to an exhaust system for an internal combustion engine having an integrated thermoelectric generator and its use for thermal power generation from exhaust gas. [Prior Art] Such configurations of thermoelectric generators and Peltier arrangements have long been known. The p-type and doped semiconductors that are heated on one side and cooled on the other side carry charge via an external circuit so that electrical operation can be performed under load in the circuit. The efficiency of thermal conversion to electrical energy here is thermodynamically limited by Carnot efficiency. Therefore, at a temperature of 400 K on the hot side and at a temperature of 400 K on the "cold" side, the efficiency may be (1 〇〇〇 _4 〇〇): 1 〇〇〇 = 6 〇〇 / ^ However 'to date It is only possible to achieve an efficiency of at most 6%. On the other hand, if direct current is applied to such a configuration, heat is transferred from one side to the other side. This type of Peltier configuration operates like a heat pump and is therefore suitable for use in cold equipment components, vehicles or buildings. Heating by means of the Peltier principle is also advantageous over conventional heating methods because more heat is often transferred than the supplied energy equivalent. Currently, thermoelectric generators are used in space probes to generate direct current, cathodic corrosion protection for pipes, to supply energy to lights and radio buoys or beacons, and to operate radios and televisions. The advantage of a thermoelectric generator is that it is extremely reliable. Therefore, its operation is independent of atmospheric conditions such as atmospheric humidity; there is no error-prone material transfer and only charge transfer exists. The thermoelectric module includes p-type and n-type legs that are electrically connected in series and thermally in parallel. Figure 2 shows one such mode.

S 161982.doc 201245569 The classic structure comprises two support plates, preferably ceramic plates, with individual legs alternating between the support plates. In each case, the two legs are in contact with each other in an electrically conductive manner by means of the end faces. In addition to the electrically conductive contact members, various additional layers are typically applied to the actual material, which layers act as a protective or solder layer. However, the electrical contact between the two legs is ultimately established by means of a metal bridge. The contact member is the primary component of the thermoelectric component. The contact member represents the physical link between the material at the "heart" of the component (which is responsible for the desired thermoelectric effect of the component) and the "outside world." The structure of such contact is shown in the figure, and the structure of the thermoelectric module is illustrated in Fig. 2. The thermoelectric material 1 within the assembly ensures the actual effect of the assembly. This is a thermoelectric leg. There is a current and heat flow through the material to enable the material to perform its function in the overall structure. Material 1 is joined to feed lines 6 and 7 by means of contacts 4 and 5 on at least two sides. Here, layers 2 and 3 are intended to represent - or a plurality of intermediate layers (barrier material, solder, adhesion promoter or the like) which may be necessary between the material crucible and the contacts 4 and 5. However, the sections 2/3, 4/5, 6/7 in which the respective pairs are combined do not have to be the same. Ultimately, & also depends on the specific structure and application, as is the flow of current through the structure and the direction of flow of heat. The contacts 4 and 5 play an important role. It provides a tight contact between the material and the feed line. If the contact is poor, there is a serious loss here and the power of the component may be severely restricted. To do this, the legs and contacts are often pressed onto the material. The contacts are subjected to extremely heavy mechanical loads. Once the higher temperature is involved, 161982.doc 201245569 (or indeed lower) and/or thermal cycling, then these mechanical loads increase even further. Thermal expansion of the material incorporated into the assembly results in mechanical stresses that, in extreme cases, result in component failure due to breakage of the contacts/to avoid this situation. The contacts used must have some flexibility and ridge properties. To allow compensation for these thermal stresses. In order to impart stability to the entire structure and to ensure the necessary thermal coupling on all legs (thermal coupling should be as uniform as possible), such a support plate as shown in Figure 2 is necessary for this purpose. From ^, 2 or oxide or nitride. There are often limitations regarding the use of the canonical structure because only the always flat surface can be in contact with the thermoelectric module. To ensure proper heat flow, intimate contact between the module surface and the heat source/heat sink is indispensable. At present, attempts are being made to provide thermoelectric modules in exhaust systems or exhaust gas recirculation systems of motor vehicles, such as passenger cars and trucks, from the heat of the exhaust gases. In this case, the hot side of the thermoelectric element is connected to the exhaust or exhaust pipe and the cold side is connected to the cooling system. The amount of electricity that can be generated depends on the temperature of the exhaust gas and the heat flow from the exhaust gas to the thermoelectric material. In order to maximize heat flow, fittings are often installed in the exhaust pipe 'however, it is limited because of an example. Women's hot parent exchangers often cause pressure loss in the exhaust gas, which in turn leads to an unacceptable increase in internal combustion engine consumption. In fact, thermoelectric generators are typically installed in the exhaust system behind the exhaust catalytic converter. At the same time as the pressure loss in the exhaust catalytic converter, this often results in excessive pressure loss and therefore no heat transfer fitting is provided in the exhaust system, but the thermoelectric module rests on the outside of the exhaust pipe. To this end, it is often necessary to provide an angular cross section for the exhaust gas 161982.doc 201245569, thereby enabling the flat surface to be in intimate contact with the thermoelectric material. However, heat transfer is still difficult to satisfy. SUMMARY OF THE INVENTION An object of the present invention is to configure a thermoelectric generator for use in an exhaust system of an internal combustion engine, meaning that a temperature difference as large as possible should be generated during operation of the thermoelectric generator. In particular, it is intended to improve the heat transfer from the exhaust gas to the thermoelectric generator. According to the invention, this object is achieved by an exhaust system for an internal combustion engine having an integrated thermoelectric generator, the exhaust system having at least one conduit 'exhaust gas flowing through the conduit, and at least one thermoelectric module in the conduit The cold side of the thermoelectric module is directly in contact with the exhaust gas and the cold side of the thermoelectric module is cooled by means of a heat transfer medium. Preferably, the at least one thermoelectric module has P-type and n-type legs, the legs are electrically connected in series and thermally connected in parallel, and the contact members are resting on the hot side of the thermoelectric module and On the support plate on the cold side, the exhaust gas flow directly impinges on the support plate on the hot side of the thermoelectric module. The heat transfer (the thermoelectric module from the exhaust to the hot side and the self-heating module to the cold side of the cold side) is a key factor in providing the largest possible temperature difference for the thermoelectric module. Thus, in the broadest sense, the present invention relates to the utilization of exhaust gases via direct conversion of thermal energy into electrical energy by a thermoelectric generator. The thermoelectric generator consists of a heat source (exhaust gas), a thermoelectric active module, and a heat sink (cooling medium). Therefore, in order to achieve high productivity of electric energy, there is a need for a thermoelectric module having a high temperature difference between the heat source and the heat sink as much as possible and requiring high efficiency. The present invention relates to a thermoelectric generator having improved heat transfer from an exhaust gas to a thermoelectric module, the improvement being achieved by placing a thermoelectrically active element and/or a necessary contact and insulating layer directly in the conduit carrying the exhaust gas. The exhaust system of the present invention can have apertures into which the thermoelectric modules are inserted in a package' thereby ensuring that the packaged thermoelectric modules are in direct contact with the exhaust gases. The packaged thermoelectric module used is hermetically mounted to its cold side relative to the exhaust system. The thermoelectric module is constructed as described in the introduction to the specification and as illustrated in Figure 2 and Figure 2. Due to the fact that the hot side of the thermoelectric module is in direct contact with the exhaust gas, heat transfer losses are minimal on the hot side of the thermoelectric module. In contrast, in the hitherto known embodiments, the thermoelectric module is placed outside the exhaust pipe, thereby significantly impairing heat transfer. The thermoelectric module typically has a support or insulating plate on the surface to impart stability to the structure of the thermoelectric module and to ensure the necessary thermal coupling on all legs, which should be as uniform as possible. According to the present invention, an additional protective layer can be applied to the support plates as long as the protective layers do not significantly impede heat transfer from the exhaust gas to the thermoelectric module. For example, a cover layer composed of a thin metal layer may be provided. Technical Description According to the present invention, the term "exhaust system" is used to mean an exhaust line section of an internal combustion engine. The exhaust system can also be opened from the cylinder outlet of the internal combustion engine to the entire end of the exhaust pipe. For example, an exhaust catalytic converter and other accessories may be additionally provided in the exhaust system, such as an exhaust turbocharger or a 161982.doc S: 201245569 particulate filter; The exhaust system of the present invention is configured as close as possible to the exit of the internal combustion engine to allow for large temperature differences in the thermoelectric material. The precise positioning along the exhaust system can be determined by the stability and operating conditions of the individual thermoelectric materials. The exhaust system of the present invention has at least one conduit through which exhaust gas flows and in which the thermoelectric module is disposed. For example, exhaust gas can be distributed between many pipes' thermoelectric modules are integrated into each pipe. For example, thermoelectric modules disposed in adjacent conduits can collectively contact the heat transfer medium on the cold side. In this configuration, the conduit can have any suitable cross-section and longitudinal wear. The at least one conduit through which the exhaust stream flows preferably has a rectangular or trapezoidal cross section including substantially flat sidewalls, the thermoelectric generator being integrated into one or more flat sidewalls. For example, the thermoelectric module can be integrated into In the two opposite side walls of the pipe. In the region in which the thermoelectric module is integrated, the exhaust system preferably has a substantially flat rectangular parallelepiped shape in which the thermoelectric module or generator is disposed on the flat side of the rectangular parallelepiped, i.e., the side surface having the largest surface area. Preferably, 3 to j thermoelectric modules are disposed in the exhaust system of the present invention. There are preferably 2 to 1 〇 'More 3 to 5 layers of thermoelectric modules in the corresponding exhaust duct. A plurality of modules having the same design of thermoelectric modules are preferably used in a thermoelectric generator and connected together. The conduit for carrying the exhaust gas preferably serves as a direct support for the thermoelectrically active element and its necessary insulation and contact layers. This eliminates the need for a separate package of thermoelectric modules placed on gas lines. According to the present invention, no layer is required between the exhaust duct and the thermoelectrically active element. The layer of the hermetic package of the thermoelectric module is used. At least one layer of the xenon module 将 x 将 will suppress heat flow. The ., .. module is preferably airtightly incorporated into at least one of the tubes on the side. Therefore, turn off the cold & thermostat module. In this case, regarding the "encapsulation and airtightness of the electroactive element: Τ" side and the adjacent element μ m ., *11 helps to cover the cover to the hot side 2, so the money can be left to the ground (4) The heat ==Γ or tube is constructed of any suitable material. Others can be used as a ^ μ casting materials, affixed bulk materials or some as bulk materials for the use of heat-resistant solid bodies. A: - the gas pipe preferably has a rectangular or trapezoidal transverse longitudinal section ❹ 丨 , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Hot side open: package; == connection: welded, sintered, bonded or otherwise sealed in a solid material to hermetically seal. According to the invention, the at least one conduit or conduits may have fittings that improve the flow of exhaust gas to the at least one thermoelectric module. However, such a match = should not significantly increase the pressure in the pipe. The dust loss of the exhaust gas (more specifically, the exhaust gas from the internal combustion engine) flowing through the exhaust system of the present invention or the pipe of the present invention preferably should not exceed 100 mbar, and in particular should not exceed 5 〇. The pressure loss does not cause the internal combustion engine. Increased fuel consumption. A plurality of thermoelectric modules may be present in the thermoelectric generator in an end-to-end and/or adjacent to each other in a plane. In addition, protection against overheating temperatures can be provided on the thermoelectric module

161982.doc S 201245569 Layer. This layer (also referred to as the "phase change layer") is preferably comprised of 25 Å. 〇 to 17〇〇. Build an inorganic metal salt or metal alloy with a melting point within the range. Suitable metal salts are sulphate, sodium 'potassium, noodles, magnesium, sputum and sputum vapors, vapors, bromide 'iodide, sulfate 'nitrate, carbonate, chromate, molybdic acid Salt, vanadate and tungstate. It is preferred to use a mixture of such suitable salts which form a binary or ternary eutectic as a material. It can also form a quaternary or pentad eutectic. It is possible to use metal alloys and combinations thereof, such as rhetoric, magnesium, aluminum, steel, office, Shixi, and to form a binary, ternary, quaternary or pentad eutectic, as a substitute for phase change materials. The melting point of the metal alloy should be in the range of 2 〇〇 ° c to 18 ° ° C. The thermoelectric module can be encapsulated with a protective layer, especially when using metals such as nickel, tantalum, titanium, silver and iron or when alloys based on nickel, chromium, iron, niobium and/or titanium are used. One or more of the thermoelectric modules of the present invention may be integrated into an exhaust system of an internal combustion engine', e.g., connected in series. In this case, the thermoelectric module can also be combined with different thermoelectric materials. In general, any thermoelectric material suitable for the temperature range of the exhaust gas from the internal combustion engine can be used. Examples of suitable thermoelectric materials are: skutterudite, such as CoSb3, RuPdSb6, TX6 (where T=Co 'Rh, Ir and χ=Ρ, As 'Sb); χ2γ8ζ24 (where χ = steel elements, lanthanides, Alkaline earth metal, alkali metal, Th, Group IV element); semi-Heusler compound, such as TiNiSn, HfPdSn and intermetallic alloy; clathrate, such as zn4Sb3, Sr8Ga16Ge30, Cs8Sn44, C〇4TeSb4; Oxide, such as 161982.doc β 1〇β s 201245569

NaxCo02 > CaCo4〇9 ' Bi2Sr2C〇2〇ySr2Ti〇4 ' Sr3Ti2〇7 > Sr4Ti3O10, RbxMxCo03 (where R = rare earth metal and M =. earth metal); Srn+1Tin03n+1 (where n is an integer); YBa2Cu3 〇7 χ ; 矽 ,, such as

FeSi2, Mg2Si, Mn15Si26; boride such as B4c, CaB6;

BhCes and its derivatives, pbce and its derivatives, oximes such as zinc telluride and Zinti phase such as YbMMnSb4. The exhaust system of the present invention is preferably installed in a motor vehicle. In this case, the exhaust system is mainly used as thermal power generation from the exhaust gas. In detail, the exhaust system of the present invention has an advantage in that heat transfer loss between the exhaust gas and the thermoelectric module is minimized, whereby the efficiency of power generation can be improved. [Embodiment] An illustrative embodiment of the exhaust system of the present invention is explained in more detail in the accompanying drawings. EXAMPLES Examples of the exhaust system or exhaust duct of the present invention are illustrated in Figures 3 through 5. Figure 3 shows a schematic cross-face of an exhaust system of the present invention having a layered configuration of two exhaust conduits (2〇a, 2〇b). The thermoelectric module (21a. n) is directly applied thereto and is disposed downstream of the connected cooling plates (23a, 23b, 23e), which in turn is used to dissipate the heat introduced from the gas pipe and maintain as much as possible across the thermoelectric module Large temperature gradient. It is apparent from the figure that the thermoelectric module (21a".n) is in direct contact with the exhaust gas in the exhaust ducts (20a, 20b) on the hot side, while the cold side of the thermoelectric module is by means of a heat transfer medium (cooling plates 22a, 22b) , 22c) cooling. 161982.doc , , c 201245569 It can be seen from Figure 3 that five consecutive thermoelectric modules are provided above and below the exhaust ducts. The beta cooling plates are in contact with the cooling medium, and the cooling medium flows in and out via the connections shown on the left side of Figure 3. Figure 4 shows a top plan view from above of the exhaust system of the type illustrated schematically in Figure 3. The cooling plates (22a c) and the thermoelectric modules (21a...η) located behind the thermal insulation layer are apparent. An electrical connection for the thermoelectric module can be seen above the upper cooling plate. Fig. 5 shows a measuring structure for the exhaust duct (2〇a/b) of the present invention, which is provided with modules (21a...n) on both sides. Show one thermoelectric module with electrical input and output. In the illustrated exhaust system, the heat transfer loss between the exhaust gas and the thermoelectric module is minimized, thereby increasing the efficiency of power generation. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the structure of a contact. Figure 2 illustrates the structure of a thermoelectric module. Figure 3 illustrates an unintended cross section of an exhaust system of the present invention having a layered configuration of two exhaust conduits. Figure 4 illustrates a perspective view from above of the exhaust system illustrated in Figure 3. Figure 5 illustrates the measurement structure for the exhaust duct of the present invention. [Main component symbol description] 2 3 4 Thermoelectric material intermediate layer intermediate layer contact piece 161982.doc -12- 201245569 5 Contact piece 6 Feed line 7 Feed line 20a Exhaust pipe 20b Exhaust pipe 2 1 a...n Thermoelectric mode Group 22a, 22b ' 22c cooling plate 161982.doc 13-

Claims (1)

201245569 VII. Patent application scope: An exhaust system with an integrated thermoelectric generator for an internal combustion engine 'The exhaust system has at least one pipe through which exhaust gas flows' and at least one thermoelectric module in the pipe The exhaust system of claim 1 is configured such that the hot side of the thermoelectric module is in direct contact with the exhaust gas and the cold side of the thermoelectric module is cooled by means of a heat transfer medium, wherein the at least one thermoelectric module Having a p-type and an n-type leg 'the legs are electrically connected in series and thermally connected in parallel, and the contact members rest on the support plate on the hot side and the cold side of the thermoelectric module, The exhaust stream directly impinges on the support plate on the hot side of the thermoelectric module. 3. The exhaust system of claim 1 wherein the at least one conduit through which the exhaust gas flows has a rectangular or trapezoidal cross-section comprising substantially planar sidewalls, the thermoelectric generator being integrated into one or more of the planar sidewalls. 4. The exhaust system of claim 3 wherein the thermoelectric module is integrated into two opposing side walls of the conduit. 5. The exhaust system of any of claims 1 to 4, wherein the at least one thermoelectric module is hermetically incorporated into the at least one conduit on the cold side of the at least one thermoelectric module. 6. The exhaust system of any one of claims 1 to 4, wherein the at least one conduit has an accessory 0 that improves the flow of the exhaust gas to the at least one power module. 7. Requests 1 to 4 Either of the groups are present in / of the plurality of thermoelectric modes 15 to be connected end to end in a plane and/or adjacent to each other 161982.doc S 201245569. 8. The exhaust system of any of claims 1 to 4, wherein the exhaust system is installed in a motor vehicle. 9. The exhaust system of any of claims 1 to 4 for use in thermal power generation from exhaust gases. 161982.doc - 2 - S