• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    Summary An extension device (2) in an exhaust system for an internal combustion engine comprises an extension part (4) and a pipe system (6) for directing exhaust gases (8) to the extension part (4) and a pipe system (10) for conducting exhaust gases from the extension part ( 4). An injector (l2) is arranged to inject a reducing agent (l4) into the exhaust gases. To ensure elongation of the reducing agent and to prevent cooling of the wall surfaces which the reducing agent may hit, the elongation device (2) comprises an insulating part (16) arranged to thermally insulate the elongation part (4) from the pipe system (10) leading the exhaust gases from the elongation part. (Figure 2)
    公开号:SE1150546A1
    申请号:SE1150546
    申请日:2011-06-16
    公开日:2012-12-17
    发明作者:Esa Rosvall
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    15 20 25 30 2 depending on the storage level. In order to maintain a high conversion efficiency under different operating conditions, the NH3 layer must be maintained. However, as the temperature of the SCR catalyst increases, the NH 3 level must be reduced to avoid NH 2 emissions (ie, excess NH 2 is emitted from the SCR catalyst), which may reduce the conversion efficiency of the catalyst.
    In summary, in order to meet stricter environmental requirements, all your vehicle manufacturers use SCR catalytic converter systems to purify diesel exhaust gases from nitrogen oxides (N OX). This is done by injecting ammonia solution into an SCR catalyst that helps convert NOX particles into nitrogen and water. The exhaust gas purification strategy should take into account that sufficient NOX is converted while not wanting to inject too much ammonia, for both the driving economy and the environment.
    The temperature of the exhaust gas must normally be in the range 400-500 ° C for the reducing agent to evaporate and for the subsequent catalyst to function optimally.
    It has been noted that when injecting a reducing agent at low exhaust fumes and low temperatures, the agent does not have time, e.g. urea, which evaporates without sticking to the evaporation wall and begins to grow into the urea - this is schematically illustrated in Figure 1. This occurs, for example, at temperatures below 280 ° C when using AdBlue®.
    If this growth is allowed to continue, the function will deteriorate because the exhaust gases do not emerge.
    US 2006/0008397 and US 2008/0041036 show how to thermally insulate the evaporator part, among other things by applying a heat-insulating material on the outside of the evaporator part.
    The object of the present invention is to provide an improved evaporator device which eliminates the problem of, for example, the urea being formed in connection with the evaporator part, which can cause operational disturbances and in the worst case downtime. Summary of the Invention The above objects are achieved by the invention defined by the independent claim.
    Preferred embodiments are defined by the dependent claims.
    According to the present invention, a thermal insulation is provided with an insulating part between the pipe system and the extension part, which prevents the shields from spreading from the extension part to the pipe system. This improves the conditions for the narrowing of the reducing agent in the exhaust gases when they hit the narrowing part.
    By applying the present invention, a more even temperature is maintained in the evaporation part and the energy in the exhaust gases can be utilized better.
    According to one embodiment, a heating device is arranged for heating the extension part. For example, the heating device consists of an electric heating device which, in application in connection with the present invention, requires a relatively small effect when the heat is concentrated to the extension part and is not conducted away to the pipe parts because the insulating part prevents this.
    According to a further embodiment, the narrowing part is made of a material with a high thermal conductivity, for example copper.
    Further features and advantages will become apparent from the accompanying description which exemplifies a number of different embodiments of the invention.
    Brief description of the drawings Fig. 1 shows a schematic longitudinal section of a part of an exhaust system according to the prior art. Fig. 2 shows a schematic longitudinal section of a part of an exhaust system illustrating an evaporator device according to the present invention.
    Fig. 3 shows a schematic longitudinal section of a part of an exhaust system illustrating another embodiment of an evaporator device according to the present invention.
    Fig. 4 shows a schematic longitudinal section of a part of an exhaust system illustrating still another embodiment of an evaporator device according to the present invention.
    Fig. 5 shows a schematic cross-section A-A of the evaporator device according to Fig. 2.
    Fig. 6 shows a schematic longitudinal section showing how the insulating part is mounted to the second pipe part and the insulating part.
    DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In the accompanying figures, the same or similar parts are shown with the same reference numerals.
    Figure 1 shows a schematic longitudinal section of a part of an exhaust system according to the prior art. The exhaust system comprises an evaporator device with an outer tube 7, a concentrically arranged inner tube 5 and an evaporator part 3 connected to the outer tube 7. An injector 12 is arranged in the inner tube for injecting a reducing agent, e.g. urea, in the exhaust gases 8 which are passed through the inner tube, past the injector 12, towards the evaporator part 3 and then back along the channel formed between the outer wall of the inner tube 5 and the inner wall of the outer tube 7.
    At too low temperatures on the exhaust gases, for example at temperatures below 280 ° C when using AdBlue, there is a risk that reducing agents that have not evaporated will accumulate and grow on the evaporating part. If this growth 9 is allowed to continue, the function of the exhaust system will deteriorate as the flow of the exhaust gases deteriorates, which may result in operational disturbances and downtime as a result.
    Figure 2 shows a schematic longitudinal section of an evaporator device according to the present invention. Evaporation device 2 intended to be part of an exhaust system for an internal combustion engine (not shown), for example a diesel engine for a vehicle. The evaporator device 2 comprises an evaporator part 4, a pipe system comprising a first pipe part 6 for conducting exhaust gases from the internal combustion engine towards the evaporator part 4, and a second pipe part 10 for conducting exhaust gases from said evaporator part. Preferably, the first pipe part 6 is concentrically arranged in the second pipe part 10 so that a channel is formed for the exhaust gases flowing away from the evaporating part, between the outer wall of the first pipe part 6 and the inner wall of the second pipe part 10. As can be seen from In the figures, the exhaust gases, the flows of which are illustrated by arrows 8, will thus turn in the direction of flow as they pass the evaporator part 4.
    The outer diameter of the second pipe part is preferably in the order of 130-150 mm and the wall thickness is in the range 1-5 mm. The pipe parts are made of, for example, jäm.
    The first pipe part 6 is adapted for mounting an injector 12 arranged to inject a reducing agent 14, e.g. urea, in the exhaust gases 8. The injector is connected to a tank (not shown) with reducing agent and the injection is controlled by a control unit (not shown) in a manner known to those skilled in the art.
    During normal operation of the engine, the injected reducing agent will at least partially evaporate already when it is injected into the hot exhaust gases, but a certain part will also evaporate when it hits hot wall surfaces in the exhaust system. It is therefore essential that the wall surfaces have a high temperature, especially if the exhaust gases have a relatively low temperature, which can occur at low engine speeds and / or at low engine load. The purpose of the evaporator device 2 is to ensure that the wall surfaces which may come into contact with unevaporated reducing agent have a high temperature. Normally the wall surfaces of the exhaust gases are stored, but the wall surfaces are all exposed to cooling by discharge to other parts of the exhaust system. To prevent this from happening, the evaporator device 2 comprises an insulating part 16 arranged to thermally insulate the second pipe part 10 from the evaporator part 4. The insulating part 16 is made of a poor thermal conductor, i.e. of a material with a low thermal conductivity coefficient, such as ceramic or glass, to ensure the thermal insulation. This ensures that the heat in the evaporator part 4 is not conducted away via the second pipe part 10, but instead can maintain a high temperature which ensures that the injected reducing agent can be evaporated.
    Preferably, the insulating member 16 has a shape corresponding to the cross section of the second pipe member 10, which preferably has a substantially circular cross section. Of course, other cross-sections may occur, such as elliptical or square. What is central is that the insulating part 16 thermally insulates the evaporation part 4 from the second pipe part 10.
    As can be seen, the insulating part thus forms a part which is arranged between the second pipe part 10 and the evaporation part and these parts are thus mechanically insulated from each other, which in turn prevents heat transfer through conduit.
    Figure 5 is a schematic cross-section at A-A in Figure 2 of a part of an exhaust system illustrating an evaporator device according to Figure 2. Figure 5 shows an embodiment where the insulating part 16 is annular.
    The evaporator part 4 is, according to an embodiment, cup-shaped in such a way that the exhaust 8 from the first pipe part 6 is led into the channel between said first pipe part 6 and said second pipe part 10. The bowl-shaped evaporator part 4 preferably has a convex central part 15 which facilitates the exhaust flow to flow out towards the inner wall of the second pipe part 10. The evaporation part can also be designed without this convex central part, and then have the shape of, for example, a hemisphere.
    Figure 6 shows a schematic longitudinal section how the insulating part 16 is mounted between an end part 18 of the second pipe part 10 and the evaporation part 4, so that the second pipe part and the evaporation part are not in direct contact with each other. The end part 18 can for instance consist of an outward ns end. The evaporator part 4 is correspondingly provided with an edge 26, adapted to be mounted against the insulation part 16. To hold the second pipe part together at the insulation part and the evaporator part, for example a screw connection 28 can be used. The screws are preferably of a material that conducts heat poorly.
    To further improve the function of the evaporator 2, according to an embodiment shown in Figure 3, it comprises a heating device 20 arranged for heating the evaporator part 4. The heating device may for instance be a resistor or a filament which emits heat when a current flows through it. To transfer the friend to the evaporator part 4, the resistor / filament is, for example, molded into an applicator which has a shape which corresponds to the outside of the evaporator part.
    The evaporator device according to this embodiment comprises a control unit 22 adapted to control the heating of the heating unit via a control signal 24 which is delivered to the heating unit 20, the heating being initiated if predetermined heating criteria are met.
    The recovery criteria are chosen to include conditions and parameters that reflect situations where the exhaust gas temperature risks becoming too low for the reducing agent to evaporate. These heating criteria may, for example, include speed limits for the motor, and that the heating is initiated if the current motor speed is below a predetermined level. The heating criteria may also include the temperature of the exhaust gases, and that the heating is initiated if the current exhaust gas temperature is below a predetermined level.
    In order to further enable that as large a part as possible of the reducing agent actually hits the evaporator part 4 and is evaporated, according to an embodiment schematically shown in Figure 4, a voltage generator 26 is arranged to apply a high electrical voltage 28 between the evaporator part 4 and earth. Since the droplets of the reducing agent have a polarity, the applied voltage, with a polarity selected depending on the selected reducing agent, will attract the reducing agent which is thus sucked in towards the evaporating part.
    The magnitude of the voltage depends on how well the evaporator part is insulated from the second pipe part 10, i.e. the thickness of the insulation part 16. A suitable voltage is about 1 kV / mm insulation, which means that about 10 kV may be suitable if the insulation part has a thickness of 10 mm.
    According to a further embodiment, the evaporator device 4 is made of a material with a high thermal conductivity, for example copper or suitable alloys. After the exhaust gases have passed the evaporator described above, the exhaust gases are passed on in the exhaust system to an SCR catalyst where the nitrogen oxides present in the exhaust gases are reduced.
    The present invention is not limited to the above-described preferred embodiments.
    Various alternatives, modifications and equivalents can be used. The above embodiments are, therefore, not to be construed as limiting the scope of the invention as defined by the appended claims.
    权利要求:
    Claims (15)
    [1]
    Evaporation device (2) intended to be part of an exhaust system for an internal combustion engine comprising an evaporation part (4), a pipe system comprising a first pipe part (6) for directing exhaust gases (8) from said internal combustion engine towards said evaporation part (4), a second pipe section (10) for guiding exhaust gases from said evaporation section, and an injector (12) arranged to inject a reducing agent (14) into the exhaust gases which are led into the first pipe section (6), characterized in that the evaporation device comprises an insulating section (16 ) arranged to thermally insulate said second pipe part (10) from said evaporation part (4).
    [2]
    The evaporator device according to claim 1, wherein said insulating member (16) is made of a bad thermal conductor, such as ceramic or glass.
    [3]
    The evaporator device according to claim 1 or 2, wherein said insulating part (16) has a shape corresponding to the cross section of the second pipe part (10).
    [4]
    The evaporator device according to any one of claims 1-3, wherein the second pipe part (10) has a substantially circular cross-section.
    [5]
    The evaporator device according to any one of claims 1-4, wherein the insulating part (16) is annular.
    [6]
    The evaporator device according to any one of claims 1-5, wherein the insulating part (16) is adapted to be mounted between an end part (18) for the second pipe part (10) and the evaporator part (4), so that the second pipe part and the evaporator part do not stand in direct contact with each other.
    [7]
    The evaporator device according to any one of claims 1-6, wherein the first pipe part (6) is arranged concentrically in the second pipe part (10).
    [8]
    The evaporator device according to any one of claims 1-7, wherein the evaporator part (4) is cup-shaped in such a way that the exhaust gas flow from the first pipe part (6) is led into said second pipe part (10), and is further provided with an edge (26) adapted to be mounted against the insulating part (16).
    [9]
    The evaporator device according to any one of claims 1-8, wherein the evaporator device comprises a heating device (20) arranged for heating the evaporator part (4).
    [10]
    The extension device according to any one of claims 1-9, comprising a control unit (22) adapted to control the heating via a control signal (24) to the heating unit (20), the heating being initiated if predetermined heating criteria are met.
    [11]
    The evaporator device according to claim 10, wherein said heating criteria comprise speed limits for the internal combustion engine, and that the heating is arranged to be initiated if the current engine speed is below a predetermined level.
    [12]
    The evaporator device according to claim 10 or 11, wherein said heating criteria comprise the temperature of the exhaust gases, and that the heating is arranged to be initiated if the current exhaust gas temperature is below a predetermined level.
    [13]
    The evaporator device according to any one of the preceding claims, wherein the evaporator device (4) comprises a voltage generator 26 arranged to apply a high electrical voltage 28 between the evaporator part and the second pipe part connected to earth.
    [14]
    The evaporator device according to any one of the preceding claims, wherein the evaporator device (4) is made of a material with high thermal conductivity.
    [15]
    Internal combustion engine comprising an exhaust system comprising an evaporator (4) according to any one of the preceding claims.
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    同族专利:
    公开号 | 公开日
    SE536791C2|2014-08-19|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2017-01-31| NUG| Patent has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    SE1150546A|SE536791C2|2011-06-16|2011-06-16|Thermally insulated evaporator designed to be included in a single exhaust gas system for an internal combustion engine|SE1150546A| SE536791C2|2011-06-16|2011-06-16|Thermally insulated evaporator designed to be included in a single exhaust gas system for an internal combustion engine|
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