Method for controlling the temperature of a NOx controlling component and an exhaust after treatment system

Abstract

The invention relates to a method for controlling the temperature of an NOx controlling component in an exhaust after treatment system of an internal combustion engine. The NOx controlling component has inner surface portions defining an interior component space through which exhaust gases are arranged to flow in order to be NOx controlled, and has outer surface portions facing away from the interior component space. The method comprises the step of: controlling the temperature of at least a portion of the NOx controlling component by a heat transfer medium arranged outside of the outer surface portions. The invention also relates to an exhaust after treatment system and a vehicle with such a system.

Claims

1. A method for controlling the temperature of a NOx controlling component in an exhaust after treatment system of an internal combustion engine, said NOx controlling component having inner surface portions defining an interior component space through which exhaust gases are arranged to flow in order to be NOx controlled, and having outer surface portions facing away from said interior component space, the method comprising: controlling the temperature of at least a portion of said NOx controlling component by a heat transfer medium arranged outside of said outer surface portions, herein the heat transfer medium comprises gas that has been obtained in accordance with the following: bleeding a sub portion of the exhaust gases downstream of said NOx controlling component.

2. The method according to claim 1, wherein said step of controlling the temperature comprises directing a flow of said heat transfer medium to flow over said outer surface portions of said NOx controlling component.

3. The method according to claim 1, wherein said step of controlling the temperature comprises cooling at least a portion of said NOx controlling component by said heat transfer medium.

4. The method according to claim 1, wherein said step of controlling the temperature comprises heating at least a portion of said NOx controlling component by said heat transfer medium.

5. The method according to claim 4, comprising the further step of heating a fluid in a heating line by a burner, and using said heated fluid to form at least a part of said heat transfer medium.

6. The method according to claim 1, wherein said step of controlling the temperature comprises receiving heat from, or releasing heat to, said NOx controlling component by a phase change of said heat transfer medium.

7. The method according to claim 1 where said NOx controlling component is a diesel oxidation catalyst, DOC component, or a NOx adsorber, e.g. a passive NOx adsorber, PNA, a lean NOx trap, LNT, or another type of NOx adsorber.

8. An exhaust after treatment system comprising an NOx controlling component having inner surface portions defining an interior component space through which exhaust gases is arranged to flow in order to be NOx controlled, and having outer surface portions facing away from said interior component space, said exhaust gas after treatment system further comprising a heat transfer arrangement arranged to at least partly surround said NOx controlling component, said heat transfer arrangement being configured to contain a heat transfer medium in order to control the temperature of said NOx controlling component by receiving heat from, or releasing heat to, said outer surface portion of said NOx controlling component, wherein said heat transfer arrangement comprises an inlet for receiving said heat transfer medium, and an outlet for discharging said heat transfer medium such that said heat transfer medium is allowed to flow through said heat transfer arrangement, and wherein said heat transfer arrangement is configured to direct the flow of said heat transfer medium over said outer surface portions in order to receive heat from, or release heat to, said NOx controlling component, the exhaust gas after treatment system further comprises a selective catalytic reduction unit arranged downstream of said NOx controlling component, and a cooling by-pass channel configured to bleed a sub portion of the exhaust gases downstream of said catalytic reduction unit, and wherein said heat transfer medium is at least partly comprised of said sub portion in order to receive heat from said NOx controlling component.

9. The exhaust gas after treatment system according to claim 8, further comprising a burner configured to heat fluid in a heating line, and, wherein said heat transfer medium is at least partly comprised of said heated fluid in order to release heat to said NOx controlling component.

10. The exhaust gas after treatment system according to claim 8, wherein said heat transfer medium is chosen as a phase change heat transfer medium, and wherein said heat transfer arrangement comprises an expansion vessel configured to compensate for a change in volume of said phase change heat transfer medium as said phase change heat transfer medium undergoes a phase change when receiving heat from, or releasing heat to, said NOx controlling component.

11. The exhaust gas after treatment system according to claim 8, wherein said NOx controlling component is a diesel oxidation catalyst, DOC component, or a NOx adsorber, e.g. a passive NOx adsorber, PNA, a lean NOx trap, LNT, or another type of NOx adsorber.

12. A vehicle comprising an exhaust gas after treatment system according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

(2) FIG. 1 is a side view of a vehicle comprising an exhaust after treatment system according to an example of the present invention, and a combustion engine;

(3) FIG. 2 is a schematic overview of an exhaust after treatment system according to an example of the present invention;

(4) FIG. 3 shows a cross section of a heat transfer arrangement, and a NOx controlling component comprised in an exhaust after treatment system, according to one embodiment of the invention;

(5) FIG. 4 shows a cross section of a heat transfer arrangement, and a NOx controlling component comprised in an exhaust after treatment system, according to one alternative embodiment of the invention;

(6) FIG. 5 is a schematic overview of an exhaust after treatment system according to an example of the present invention;

(7) FIG. 6 is a flow-chart showing steps of a method for controlling the temperature of a NOx controlling component according to one embodiment of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

(8) The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which an exemplary embodiment of the invention is shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein; rather, the embodiment is provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

(9) With particular reference to FIG. 1, there is provided a vehicle 800 comprising an exhaust after treatment system (EATS) 1, 1″ according to one example of the present invention, and a combustion engine 100, such as an internal combustion engine 100, arranged upstream of, and fluidly connected to, the EATS 1, 1′ via pipe 802. The vehicle 800 depicted in FIG. 1 is a truck 800 for which the inventive concept which will be described in detail below, is suitable for.

(10) FIG. 2 shows a schematic overview of an EATS 1 in accordance with one embodiment of the invention. In the non-limiting example of FIG. 2, the EATS 1 comprises various components such as a NOx controlling component 10, a filter 20, e.g. a particulate filter for reducing soot content in exhaust gases 3, and a selective catalyst reduction (SCR) component 60. Moreover, the EATS 1 comprises a cooling by-pass channel 5′ with a corresponding shut-off valve 6′, configured to bleed a sub portion 5 of the exhaust gases 3 downstream of the SCR component 60, and an air intake 40′ with a corresponding shut-off valve 41′, configured to receive ambient air 40. Both the cooling by-pass channel 5′ and the air intake 40′ are fluidly connected to the jacket, or outer surface portions, of the NOx controlling component 10 which will be described below. Moreover, in FIG. 2, an optional burner 70 and optional heating line 72 is fluidly connected to the jacket, or outer surface portions, of the NOx controlling component 10 as will be described below.

(11) Turning to FIG. 3, showing a schematic overview of the NOx controlling component 10 of FIG. 2, and a flow heat transfer arrangement 50. The NOx controlling component 10 comprises inner surface portions 12 defining an interior component space 20 through which exhaust gases 3 is arranged to flow in order to be NOx controlled. The NOx controlling component 10 further comprises outer surface portions 14 facing away from the interior component space 20. The flow heat transfer arrangement 50 is arranged to at least partly surround the NOx controlling component 10, and in FIG. 3, the flow heat transfer arrangement 50 completely surrounds the NOx controlling component 10. The flow heat transfer arrangement 50 is configured to contain a heat transfer medium 30 which may receive heat from, or release heat to, the outer surface portion 14 of the NOx controlling component 10 in order to at least partly control the temperature of the NOx controlling component 10.

(12) In more detail, and as shown in FIG. 3, the flow heat transfer arrangement 50 comprises a heat transfer housing 51, wherein the heat transfer housing 51 defines a heat transfer space 53 which houses the NOx controlling component 10, and contains the heat transfer medium 30. Thus, in the heat transfer space 53, heat transfer is allowed to occur between the outer surface portions 14 of the NOx controlling component 10, and the heat transfer medium 30.

(13) As also shown in the embodiment of FIG. 3, the flow heat transfer arrangement 50 comprises an inlet 52 for receiving the heat transfer medium 30, and an outlet 54 for discharging the heat transfer medium 30. Hereby, the heat transfer medium 30 is allowed to flow through the flow heat transfer arrangement 50, and the heat transfer space 53, in order to exchange heat with the outer surface portions 14 of the NOx controlling component 10 (indicated by arrows in FIG. 3). For this purpose, the inlet 52 is preferably arranged to direct the flow of the heat transfer medium 30 over the outer surface portions 14. According to one embodiment, and as indicated in FIG. 3, the inlet 52 is arranged to direct the flow of the heat transfer medium 30 to an inlet portion of the NOx controlling component 10. Hereby, an effective heat transfer of the NOx controlling component 10 may be achieved. However, it should be noted that the inlet 52 may be arranged at different locations along the length of the NOx controlling component, and/or that more than one inlet (not shown) is arranged in the flow heat transfer arrangement 50.

(14) The function of the EATS 1 will now be described in more detail with reference to FIG. 2 and FIG. 3. The exhaust gases 3, or exhaust gas stream 3, from the engine 100 (shown in FIG. 1) is fed to the EATS 1 by pipe 802 fluidly connected to the NOx controlling component 10. The exhaust gas stream 3 is subsequently passed through the EATS 1, i.e. through the interior component space 20 of the NOx controlling component 10, and subsequently through other components such as the filter 20 and SCR component 60, in order to be cleaned before exiting the EATS 1 via a tailpipe 803. The EATS 1 in FIG. 2 is configured to, in at least one example operational mode, enable cooling of the NOx controlling component 10, by using the sub portion 5 of the cooling by-pass channel 5′ and/or using the ambient air 40 received by the air intake 40′. It should be understood that both, or one of, the cooling by-pass channel 5′ and air intake 40′, may be shut off by the respective shut-off valve 6′, 41′ in order to control, or even stop, the cooling of the NOx controlling component 10. In the example shown in FIG. 2, the sub portion 5 of the exhaust gases and the ambient air 40 is combined into a cooling stream 42 which is fed to the inlet 52 of the flow heat transfer arrangement 50 whereby it is allowed to flow over the outer surface portions 14 of the NOx controlling component 10 in order to receive heat, and thereby cool the NOx controlling component 10. That is, the EATS 1 in FIG. 2 is configured to utilize the cooling stream 42 as the heat transfer medium 30. Thus, the heat transfer medium in the embodiment shown in FIG. 2 is at least partly comprised of the sub portion and at least partly comprised of the ambient air 40, in order to receive heat from the NOx controlling component 10.

(15) Additionally, or alternatively, the EATS 1 in FIG. 2 is configured to enable heating of the NOx controlling component 10. Thus, for such embodiment the shut-off valves 6′, 41′ of the cooling by-pass 5 and air intake 40, respectively, are preferably closed. The EATS 1 comprises a burner 70 configured to heat a fluid in the heating line 72, whereby the heated fluid is used to form at least a part of the heat transfer medium 30. Thus, the heated fluid in the heating line 72 is guided to the inlet 52 of the flow heat transfer arrangement 50 and allowed to flow over the outer surface portions 14 of the NOx controlling component 10 in order to release heat to the NOx controlling component 10. Additionality or alternatively the heating line 72 may be heat exchanged with the exhaust gas stream 3 upstream of the NOx controlling component 10, by a heat exchanger 70′, instead of, or as a complement to, using the burner 70 for heating purposes.

(16) It should be noted that all of, or only some of, e.g. only one of, the heating and cooling means described in relation to FIG. 2, may be included in the EATS 1. To clarify, the cooling by-pass channel 5, and the sub portion 5 may be referred to as a first cooling means of the NOx controlling component 10, the air intake 40′ and the ambient air 40 may be referred to as a second cooling means of the NOx controlling component 10, the burner 70 and the heating line 72 may be referred to as a first heating means of the NOx controlling component 10, and the heat exchanger 70′ and the heating line 72 may be referred to as a second heating means of the NOx controlling component 10. For example, the cooling by-pass channel 5 may be omitted (or closed by the shut-off valve 6′), and only the air intake 40 may be used to cool the outer surface portions 14 of the NOx controlling component 10. Correspondingly, the air intake 40′ may be omitted (or closed by the shut-off valve 41′), and only the cooling by-pass channel 5 may be used to cool the outer surface portions 14 of the NOx controlling component 10. Likewise, the burner 70, and/or the heat exchanger 70′ may be omitted from the EATS, or they may be used separately and be individually shut off depending on the need of the NOx controlling component 10.

(17) Turning to FIG. 4, showing a schematic overview of the NOx controlling component 10 of FIG. 2 and FIG. 3, and an expansion heat transfer arrangement 50′. The NOx controlling component 10 in FIG. 4 is identical with the one described with reference to FIG. 3, and the features are not described here again, but same reference numerals are used for corresponding features. The expansion heat transfer arrangement 50′ is arranged to at least partly surround the NOx controlling component 10, and in FIG. 4, the expansion heat transfer arrangement 50′ completely surrounds the NOx controlling component 10. The expansion heat transfer arrangement 50′ is configured to contain a heat transfer medium 30′ which may receive heat from, or release heat to, the outer surface portion 14 of the NOx controlling component 10 in order to at least partly control the temperature of the NOx controlling component 10.

(18) In more detail, and as shown in FIG. 4, the expansion heat transfer arrangement 50′ comprises a heat transfer housing 51′, wherein the heat transfer housing 51′ defines a heat transfer space 53′ which houses the NOx controlling component 10, and contains the heat transfer medium 30′. The contained heat transfer medium 30′ is chosen as a phase change heat transfer medium 30′, meaning that the properties of the heat transfer medium 30′ is chosen such that the heat transfer medium 30′ will undergo a phase change when receiving heat from, or releasing heat to, the outer surface portions 14 of the NOx controlling component 10. Thus, the phase change heat transfer medium 30′ is adapted to the temperature range of the NOx controlling component 10 and to the desired temperature change of the NOx controlling component 10. Thus, in the heat transfer space 53′, heat transfer is allowed to occur between the outer surface portions 14 of the NOx controlling component 10, and the phase change heat transfer medium 30′.

(19) As also shown in the embodiment of FIG. 4, the expansion heat transfer arrangement 50′ comprises an expansion vessel 56′ configured to compensate for a change in volume of the phase change heat transfer medium 30′ as it undergoes a phase change when receiving heat from, or releasing heat to, the NOx controlling component 10. For this purpose, the expansion vessel 56′ is adapted in size corresponding to the chosen phase change heat transfer medium 30′.

(20) The function of the expansion heat transfer arrangement 50′ will now be described in further detail. For cooling the outer surface portions 14 of the NOx controlling component 10, the phase change heat transfer medium 30′ is chosen such that it undergoes a phase change from solid to liquid, or from liquid to gas form, for the desired temperature change of the oxidation catalyst. Hence, the expansion vessel 56′ is used to compensate for the change in volume of the phase change heat transfer medium as it changes from e.g. solid to liquid, or liquid to gas. Correspondingly, for heating the outer surface portions 14 of the NOx controlling component 10, the phase change heat transfer medium is chosen such that it undergoes a phase change from e.g. liquid to solid, or from gas to liquid form, for the desired temperature change of the oxidation catalyst. Hence, the expansion vessel 56′ is used to compensate for the change in volume of the phase change heat transfer medium as it changes from liquid to solid, or gas to liquid form. Such volume expanding or reducing properties in relation to the phase change, and the desired need of cooling or heating, is dependent on the choice of the phase change heat transfer medium 30′ and is known to the skilled person. Thus, the expansion vessel 56′ is typically adapted to the choice of the phase change heat transfer medium 30′.

(21) FIG. 5 shows an EATS 1′ similar to the EATS 1 of FIG. 2, thus the same reference numerals are used for corresponding features, and are not described in detailed again for FIG. 5. Moreover, the function of the EATS 1′ is similar to the function of the EATS 1 of FIG. 2, especially concerning the flow of exhaust gases 3 through the EATS 1′, why this is not described in detail again. However, the EATS 1′ of FIG. 5 comprises the expansion heat transfer arrangement 50′ described with reference to FIG. 4 instead of the flow heat transfer arrangement 50 described with reference to FIG. 3. Thus, both heating and cooling of the outer portions 14 of the NOx controlling component 10 is possible with the expansion heat transfer arrangement 50′, depending on the choice of the phase change heat transfer medium 30′, as described with reference to FIG. 4, and thus the cooling by-pass channel 5′, the air intake 40′ and the heating line 72 may be omitted.

(22) As shown in FIG. 5, the EATS 1′ comprises an optional exhaust gas burner 80, and a turbo unit 90 arranged upstream of the NOx controlling component 10. The exhaust gas burner 80 may be used to heat the exhaust gases 3 prior to entering the NOx controlling component 10 and/or to heat the exhaust gases after the NOx controlling component 10, and the turbo unit 90 may be provided with a turbo by-pass channel 92, enabling hot exhaust gases to by-pass the turbo unit 90 and thus heat the exhaust gases 3 prior to entering the NOx controlling component 10.

(23) As also shown in FIG. 5 the EATS 1′ comprises an optional cooling line 94, e.g. fed with ambient air, configured for direct cooling of the exhaust gases 3 prior to the NOx controlling component 10. Thus, the cooling line 94 may be used to cool the exhaust gases 3 prior to entering the NOx controlling component 10.

(24) The heating and/or cooling means of the exhaust gases shown in FIG. 5, i.e. the burner 90 and/or the turbo unit 90 with turbo by-pass channel 92, and/or the cooling line 94 shown in FIG. 5 is applicable to the EATS 1 of FIG. 2 as well.

(25) The invention will now be described with reference to a method for controlling the temperature of a NOx controlling component 10 in an exhaust after treatment system, EATS 1, 1′ as those described in FIG. 2 and FIG. 5. The method is described in the flow-chart of FIG. 6 and reference numerals used in FIGS. 1-5 will be used throughout the description of the flow-chart in FIG. 6, when referring to corresponding features.

(26) In a first step 601 of the method, the temperature of at least a portion of the NOx controlling component 10 is controlled by the heat transfer medium 30, 30′ arranged outside of the outer surface portions 14 of the NOx controlling component 10. Thus, the heat transfer medium 30, 30′ is arranged to release heat to, or receive heat from, the NOx controlling component 10 via the outer surface portions 14.

(27) In a second step 603, the first step 601 of controlling the temperature comprises cooling at least a portion of the NOx controlling component 10 by the heat transfer medium 30, 30′. That is, the second step 603 comprises cooling at least a portion of the NOx controlling component 10, by receiving heat from the outer surface portions 14.

(28) Below, different alternative steps are described which relates to either the use of the flow heat transfer arrangement 50, or to the expansion heat transfer arrangement 50′. In more detail, first and third alternative steps are related to the use of the flow heat transfer arrangement 50, and second and fourth alternative steps are related to the use of the expansion heat transfer arrangement 50′.

(29) In a first alternative first step 603a1, the second step 603 of cooling comprises directing a flow 40 of the heat transfer medium 30 to flow over the outer surface portions of the NOx controlling component 10. Thus, the heat transfer medium 30 may receive heat from the NOx controlling component 10 as it flows over the outer surface portions 14.

(30) In a first alternative second step 603a2, a sub portion 5 of the exhaust gases downstream of the NOx controlling component 10 is bled, and said sub portion is used to form at least a part of the heat transfer medium 30.

(31) In a first alternative third step 603a3, which may be carried out additionally to, or as an alternative to, the first alternative second step 603a2, external cooling gas such as e.g. ambient air 40 is used to form at least a part of the heat transfer medium 30.

(32) In a second alternative first step 603b1, the second step 603 of cooling comprises receiving heat from the NOx controlling component 10 by a phase change of the heat transfer medium 30′. This step 603b1 is typically preceded by a step of choosing a heat transfer medium as a phase change heat transfer medium adapted to the desired temperature change of the NOx controlling component 10.

(33) In a third step 605, which may be carried out additionally to, or as an alternative to, the second step 603, the first step 601 of controlling the temperature comprises heating at least a portion of the NOx controlling component 10 by the heat transfer medium 30, 30′.

(34) In a third alternative first step 605a1, the third step 605 of heating comprises directing a flow 40 of the heat transfer medium 30 to flow over the outer surface portions of the NOx controlling component 10. Thus, the heat transfer medium 30 may release heat to the NOx controlling component 10 as it flows over the outer surface portions 14.

(35) In a third alternative second step 605a2, a fluid in a heating line is heated by a burner, and the heated fluid is used to form at least a part of the heat transfer medium 30.

(36) In a fourth alternative first step 605b1, the third step 605 of heating comprises receiving releasing heat to the NOx controlling component 10 by a phase change of the heat transfer medium 30′. This step 605b1 is typically preceded by a step of choosing a heat transfer medium as a phase change heat transfer medium adapted to the desired temperature change of the NOx controlling component 10.

(37) In a fourth optional step 607, the NOx controlling component 10 is heated by adding heat to the exhaust gases 3 upstream of the NOx controlling component 10. This may e.g. be carried out by using a burner or a turbo by-pass channel.

(38) It should be understood that the NOx controlling component 10 in the EATS 1, 1′ described herein may for example be a diesel oxidation catalyst (DOC) component, or a NOx adsorber, e.g. a passive NOx adsorber (PNA), a lean NOx trap (LNT), or another type of NOx adsorber.

(39) Moreover, it should be noted that the EATS 1, 1′ shown in FIG. 1 may correspond to any one of the described EATS 1, 1′ in FIG. 2, and FIG. 5.

(40) It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.