DE102011103109A1 - Exhaust system with heat storage - Google Patents

Abstract

The present invention relates to an exhaust system (1) for an internal combustion engine, having a heat storage housing (3) and an exhaust pipe (2), the heat energy contained in the exhaust gas (A) being transported via heat pipes (5). According to the invention, the heat pipes (5) are arranged in a heat storage housing (3), the heat storage housing (3) completely enclosing the exhaust pipe (2) at least in sections in the longitudinal direction. The thermal energy extracted from the exhaust gas (A) can be dissipated via the heat pipes (5) contained in the heat storage housing (3). In particular, the system according to the invention is suitable for thermal management of the cold start behavior of an internal combustion engine.

Description

The present invention relates to an exhaust system for an internal combustion engine according to the features in the preamble of claim 1.

For operating internal combustion engines, such as gasoline or diesel engines, combustion fuels are needed. Due to limited oil resources, it is the desire to maximize the efficiency of an internal combustion engine and thus the exploitation of the energy contained in the combustion fuel. Due to the Carnot process, however, the efficiency of an internal combustion engine for converting the energy contained in the combustion fuel into mechanical energy is limited to approximately 40%.

This means that about 2/3 of the chemical energy bound in the combustion fuel is not supplied to the actual purpose of the internal combustion engine, ie the conversion of chemical energy into mechanical energy, but is lost as energy lost. In order to exploit this energy nevertheless, there are currently, in particular in the motor vehicle sector, multiple approaches, for example, the heat energy or recover the energy bound in the exhaust and to supply a particular application.

For example, the heat energy is used for heating the motor vehicle interior. There are also approaches in which thermoelectric generators convert the heat energy contained in the exhaust gas into electrical energy, which in turn can be used to operate a motor vehicle.

For an internal combustion engine initially to work in an optimal efficiency spectrum, it requires the setting of optimal operating conditions. The combustion engine, which is predominantly made of metallic materials, is designed in such a way that it operates at a good efficiency range at the operating temperature. That is, the different thermal expansions of engine block, pistons, piston rings, cylinder head, valves and other components are coordinated so that they reach an optimal operating efficiency at an average operating temperature of the core components of about 90 ° to 100 ° C and in this operating temperature Engine performance is minimized and the charge cycle is optimized. The operating materials of an internal combustion engine, for example the engine oil or in downstream transmissions, the mechanical components and the transmission oils are optimized for use at the respective operating temperature.

Especially in the cold start phases, which take place even at a starting temperature of 20 ° C, but also take place at starting temperatures of 0 ° C or minus degrees, it is therefore necessary to quickly reach the operating temperature of the individual components.

For this purpose, there are approaches from the prior art to withdraw the heat contained therein by exhaust heat energy recovery the exhaust gas and supply them to a site. For this purpose, however, heat exchangers in the region of the exhaust line are necessary, which generate an increased exhaust backpressure and thus adversely affect the overall efficiency of the internal combustion engine.

However, due to increasing demands on the minimization of exhaust emissions and associated exhaust aftertreatment components, such as a particulate filter or a catalyst, it is also counterproductive to extract heat from the exhaust in the cold start phase since the exhaust aftertreatment systems also require heat energy to develop their full effect can. In addition, often a heat transfer medium, in particular water, is used, which, however, in turn is itself limited in efficiency and represents only a suboptimal solution.

From the prior art, for example, by the DE 10 2009 049 196 A1 a heat transfer device is known in which heat is purposefully transported from a heat source to a heat sink via a heat pipe. In addition, the heat transfer is controllable.

However, the aforementioned prior art does not solve the problem in an exhaust system without increasing the exhaust backpressure and supplying heat energy to the desired heat sinks, especially in the cold start phase, without extracting too much heat energy from the exhaust gas in this phase.

Object of the present invention is therefore to provide an exhaust system available, with a targeted heat transfer is possible to withdraw without the exhaust gas in certain operating situations too much heat energy.

The aforementioned object is achieved with the features according to claim 1.

Advantageous embodiments of the present invention are part of the dependent claims.

The exhaust system according to the invention for an internal combustion engine has a heat storage housing and an exhaust pipe, wherein the Heat transport of the heat energy contained in the exhaust gas via heat pipes takes place. It is characterized in that the exhaust pipe is surrounded by the heat storage housing, wherein the heat pipes are arranged in the heat storage housing.

In the context of the invention is a part of the exhaust system, for. B. arranged at least in sections to a exhaust-carrying pipe of the exhaust line a heat storage. The heat accumulator is designed in the form of a heat accumulator housing, which preferably completely encloses or encloses the exhaust pipe at least in sections in the flow direction of the exhaust gas. In the heat storage itself are heat pipes, which are also known as heat pipe, integrated, which connect to a heat sink, preferably to produce a component to which the heat is to be supplied.

In particular, in the cold start behavior here, in contrast to previously known from the prior art solutions, the heat from the heat storage itself used to heat the connected components. The advantage of the invention is that especially in the cold start phase the exhaust gas no energy is removed, whereby the exhaust system according to the invention can be arranged both before an exhaust aftertreatment unit, as well as after an exhaust aftertreatment unit. The operating behavior of the exhaust gas aftertreatment unit is not or only insignificantly influenced by the exhaust gas system according to the invention.

The inventive arrangement of the heat accumulator to the exhaust pipe, no elements in the exhaust gas flow channel, ie in the interior of the exhaust pipe, integrated. An increase in the exhaust backpressure is thus avoided. If the entire system of the internal combustion engine has reached its optimum operating temperature, the heat energy contained in the exhaust gas can be used to charge the heat accumulator without negatively influencing the exhaust aftertreatment unit or other elements connected in the exhaust gas system.

In an advantageous embodiment, the exhaust pipe is completely enclosed by the heat storage housing. The heat storage housing is formed in this form as a cladding tube, which completely encloses the exhaust pipe at least in sections.

The heat storage housing, in particular the heat store located therein, is preferably formed from a zeolite. A dry zeolite extracts water vapor from the ambient air due to its hygroscopic character. As a result of the attachment of the water molecules to the surface of the zeolite, the molecule turns into an energetically low state. The water vapor thus releases energy in the form of heat to the zeolite, which causes the zeolite itself to heat up considerably. This heat is then removed via disposed in the heat storage housing heat pipes. In turn, by supplying heat energy from the exhaust to the zeolite, the water molecules desorb above a certain temperature and the zeolite is returned to its dry starting state.

By selecting a Zeolithwerkstoffes and dimensioning of the heat storage housing, it is thus possible to optimally tune the exhaust system to the cold start behavior of the internal combustion engine, where the exhaust system is used. In addition, an active or passive control and regulation of the exhaust system is conceivable, with which the exhaust system can be further modified to the respectively adjusting operating state.

In a further advantageous embodiment of the present invention, the heat pipes are arranged in the zeolite, preferably the heat pipes are completely enclosed by the zeolite. In the context of the invention, this is to be understood that the heat pipes are completely enclosed in the heat storage housing. Only in a connection region, preferably in an end region of the heat pipes, they emerge from the heat storage housing in order to be able to transport the heat out of the heat storage housing.

Furthermore, particularly preferably, the heat pipes are arranged running parallel to an exhaust gas flow direction. In the context of the invention, it is thus possible to conduct over particularly short distances, the heat energy extracted from the exhaust gas into the heat pipes and dissipate therefrom by the fluid contained in the heat pipes. Preferably can thus be removed over a length of 50, 100 or 200 mm already sufficient heat energy from the exhaust gas and transferred by heat conduction through the heat storage housing in the heat pipes and dissipate therefrom.

More preferably, a plurality of heat pipes are arranged in the heat storage housing. In particular, in the cross section of the exhaust pipe radially at least five, more preferably more than seven and in particular more than ten heat pipes are arranged.

In a further preferred embodiment variant of the present invention, a plurality of heat pipes are arranged running parallel in the heat storage housing and in the region of one end of the heat storage housing summarized. This makes it possible to avoid an oversized thickening of the heat storage housing by a plurality of small diameter heat pipes. By a plurality of, in cross-section rather small heat pipes, a sufficient amount of heat is removed from the heat storage and supplied in the region of the outlet of the heat storage housing via at least one central heat conduction in the form of a heat pipe to a corresponding heat sink. In particular, this results in a particularly space-saving concept of the exhaust system according to the invention.

In a preferred embodiment, the heat pipes are formed in I-shape. In a further preferred embodiment, the heat pipes are formed as a closed circuit, so that a medium therein can circulate. The schematic cross-sectional view then forms a circulation circuit. The respective choice of the appropriate application is made taking into account the expected area of application and the amount of heat to be transferred.

In a further preferred embodiment, the heat pipes are themselves controllable and adjustable. In this case, the heat transfer can be regulated and / or controlled by the heat pipe itself. For example, valves are arranged in the heat pipes, which regulate the heat transport within the heat pipe and / or control. As a result, active or in the case of passively actuated valves can be intervened in the respective heat transfer. For example, in the case of cold start behavior, initially a high heat dissipation through the heat pipes can be brought about, whereas when the operating temperature is reached heat dissipation via the heat pipes is minimized so that the heat accumulator can charge optimally.

Preferably, a thermal insulation is formed on the outer circumferential surface of the heat storage housing, in particular in the form of a metal coating. Due to the thermal insulation on the outside of the heat storage housing, the heat loss to the ambient air is minimized. This ensures that the heat accumulator can be optimally charged on the one hand in the operating behavior, on the other hand, that it retains the stored amount of heat over as long a period as possible and does not give up unused to the ambient air. The thermal insulation may also be in the form of a thermal insulation material, an air gap insulation and / or in the form of a metallic foil coating. In particular, in this case, a reflection of the heat energy in the heat accumulator can be carried back through the surface of the metallic coating in the heat storage. This in turn minimizes the amount of heat released to the ambient air.

In a further preferred embodiment variant, the heat storage housing has a valve for controlling the thermodynamic state in the heat storage housing itself. In particular, the thermodynamic state of a zeolite can be regulated and / or controlled via a controllable and controllable valve.

For enrichment of a zeolite with water molecules, the valve can be actively opened, for example. For drying the zeolite, the valve or an additional valve may be formed as a pressure relief valve.

Further advantages, features, characteristics and aspects of the present invention are part of the following description. The schematic figure representations are used for easy understanding of the invention and show a preferred embodiment. Show it:

1 an inventive exhaust system in a cross-sectional view and

2 an inventive exhaust system in a side view.

In the figures, the same reference numerals are used for the same or similar components, even if a repeated description is omitted for reasons of simplicity.

1 shows a cross-sectional view of an exhaust system according to the invention 1 , where the exhaust system 1 from an internal exhaust pipe 2 with a the exhaust pipe 2 surrounding heat storage housing 3 consists. In the exhaust pipe 2 flows exhaust gas A, which by heat transfer W in the exhaust 2 located heat energy in a heat storage medium 4 the heat storage housing 3 emits. In a preferred embodiment, the heat storage medium 4 from a zeolite. In the heat storage housing 3 themselves are heat pipes 5 arranged in the heat storage medium 4 absorb stored heat and remove it. Preferably, the heat storage housing 3 on an outer surface 6 an insulating layer 7 on.

2 shows the exhaust system of the invention 1 in a highly simplified schematic representation in side view. In the heat storage housing 3 are shown here three running in I-shape heat pipes 5 , where the heat pipes 5 parallel to the exhaust gas flow direction S in the heat storage housing 3 are arranged. The heat pipes 5 are in an end area 8th of Heat storage housing 3 to a central heating pipe 9 summarized, which through the heat pipes 5 from the heat storage housing 3 transported away heat energy to a heat consumer not shown here. Furthermore, the heat storage housing 3 a valve 10 on, with the valve 10 is used to control and control the thermodynamic state of the heat storage medium. This can be done via the heat pipes 5 regulate and control the amount of heat to be removed.

LIST OF REFERENCE NUMBERS

1

exhaust system

2

exhaust pipe

3

Heat storage housing

4

Heat storage medium

5

heat pipe

6

Outer casing surface

7

insulating

8th

end

9

Central heat pipe

10

Valve

W

heat conduction

A

exhaust

S

Exhaust gas flow direction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009049196 A1 [0009]

Claims (13)

Exhaust system ( 1 ) for an internal combustion engine, comprising a heat storage housing ( 3 ) and an exhaust pipe ( 2 ), wherein a heat transfer of the heat energy contained in the exhaust gas (A) via heat pipes ( 5 ), characterized in that the exhaust pipe ( 2 ) from the heat storage housing ( 3 ), wherein the heat pipes ( 5 ) in the heat storage housing ( 3 ) are arranged. Exhaust system according to claim 1, characterized in that the exhaust pipe ( 2 ) from the heat storage housing ( 3 ) is completely enclosed. Exhaust system according to claim 1 or 2, characterized in that the heat storage housing ( 3 ) is formed of a zeolite. Exhaust system according to claim 3, characterized in that the heat pipes ( 5 ) are arranged in the zeolite, preferably the heat pipes ( 5 ) completely enclosed by the zeolite. Exhaust system according to one of claims 1 to 4, characterized in that the heat pipes ( 5 ) are arranged to run parallel to an exhaust gas flow direction (S). Exhaust system according to one of claims 1 to 5, characterized in that a plurality of heat pipes ( 5 ) in the heat storage housing ( 3 ) run parallel and in the area of one end ( 8th ) of the heat storage housing ( 3 ) are summarized. Exhaust system according to one of claims 1 to 6, characterized in that the heat pipes ( 5 ) are formed in I-shape. Exhaust system according to one of claims 1 to 7, characterized in that the heat pipes ( 5 ) are formed as a closed circuit, so that a medium therein can circulate. Exhaust system according to one of claims 1 to 8, characterized in that the heat pipes ( 5 ) are controllable and controllable. Exhaust system according to one of claims 1 to 9, characterized in that on the outer circumferential surface ( 6 ) of the heat storage housing ( 3 ) a thermal insulation is formed, preferably in the form of a metal coating. Exhaust system according to one of claims 1 to 10, characterized in that on the heat storage housing ( 3 ) a valve ( 10 ) for controlling the thermodynamic state in the heat storage housing ( 3 ) is arranged. Exhaust system according to claim 11, characterized in that the valve ( 10 ) is designed as a pressure relief valve. Exhaust system according to claim 11 or 12, characterized in that the valve ( 10 ) is controllable and controllable.

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