Exhaust-gas mixer

Abstract

An exhaust-gas mixing pipe for admixing additive into an exhaust-gas stream of a combustion engine. The housing wall has multiple rows, arranged over a circumference U, of openings through which gas can flow into the interior of the pipe, wherein the at least one opening of a row forms in each case one stage M characterized according to its size by the average opening cross section Q of the openings, wherein the sum of all the opening cross sections Q of all the openings of all the rows of the exhaust-gas mixing pipe is equal to SQ. In that context, at least one first-order stage M1, is provided, wherein stage M1 has openings having an average opening cross section Q1. At least one second-order stage M2, is provided, with openings having an average opening cross section Q2, where Q2>=f Q1, where 5<=f<=25.

Claims

1. An exhaust-gas mixing pipe for admixing at least one additive into an exhaust-gas stream of an internal combustion engine, comprising: a housing wall of longitudinal axis L and of round cross section, and a closed end wall on which can be placed an injection nozzle, for said additive wherein the housing wall has multiple rows arranged over a circumference U, of openings, through which exhaust gas can flow from an outer side of the exhaust-gas mixing pipe into an interior of the exhaust-gas mixing pipe, wherein several openings of a row form in each case one stage M and wherein the respective stage M is characterized according to its size by an average opening cross section Q of its openings, wherein a sum of all the opening cross sections Q of all the openings of all the rows of the exhaust-gas mixing pipe is equal to SQ, wherein at least one first-order stage, stage M1, is provided, wherein the stage M1 has openings having an average opening cross section Q1, and an, in addition, at least one second-order stage, stage M2, is provided, wherein a stage M2 has openings having an average opening cross section Q2, where Q2f Q1, where 5f25, and there is provided a first sector S1 which is designed as a flushing sector and consists of at least the one stage M1, and a second sector S2 which is designed as a mixing sector and consists of at least the one stage M2, wherein, in the direction of the longitudinal axis L toward the end wall, the first sector S1 is positioned first and the second sector S2 is positioned thereafter.

2. The exhaust-gas mixing pipe according to claim 1, wherein the stage M or a sector S has at least predominantly openings which are each designed as a recess of the housing wall, and/or the stage M or the sector S has at least predominantly openings which are designed as a formation of the housing wall, wherein the formed part of the housing wall at least partially forms a blade.

3. The exhaust-gas mixing pipe according to claim 2, wherein the blade has a straight blade axis which extends parallel to the longitudinal axis L or which extends tangentially to the circumference U or which is arranged in a joint plane E with the longitudinal axis L.

4. The exhaust-gas mixing pipe according to claim 2, wherein at least one additional sector S3 is provided with at least one third-order stage, stage M3, having an average opening cross section Q3 and having a sum SQ3 of the opening cross sections Q3, where SQ3x2 SQ, where 0.05x20.35.

5. The exhaust-gas mixing pipe according to claim 4, wherein the openings of the stage M3 are an average distance r3 from the longitudinal axis L and the openings of the stage M2 are an average distance r2 from the longitudinal axis L, where r31.05 r2.

6. The exhaust-gas mixing pipe according to claim 5, wherein the openings and/or the blades of the respective stage M1, M2, M3 are arranged offset to one another with respect to the direction of the longitudinal axis L.

7. The exhaust-gas mixing pipe according to claim 4, wherein at least one additional sector S4 is provided with at least one stage M1, M2 and/or M3, wherein the sector S4 is arranged between the sector S2 and the sector S3.

8. The exhaust-gas mixing pipe according to claim 4, wherein the opening cross section Q2 or Q3 has a value qa over a first partial circumference Ua of 100 to 180 which can be turned toward the stream and has a value qb over an opposite partial circumference Ub of 100 to 180 with respect to the longitudinal axis L, where 1.1 qa=qb.

9. The exhaust-gas mixing pipe according to claim 1, wherein the sector S1 has a sum SQ1 of the opening cross sections Q1, where SQ1<=x1 SQ, where 0.05<=x1<=0.25.

10. The exhaust-gas mixing pipe according to claim 1, wherein the sector S1 consists of a maximum of three to five stages M1 and/or the sector S2 consists of a maximum of 2 to 10 stages M2.

11. The exhaust-gas mixing pipe according to claim 1, wherein the exhaust-gas mixing pipe has an average diameter DS1 in the region of the sector S1 and the sector S1 is a maximum distance AS1 from the end wall, where AS1y1 DS1, and where 0y10.3.

12. The exhaust-gas mixing pipe according to claim 1, wherein the exhaust-gas mixing pipe is calibrated at least in a region of a start of a pipe and/or of the end of a pipe with respect to the diameter and/or cross-sectional form.

13. The exhaust-gas mixing pipe according to claim 1, wherein the exhaust-gas mixing pipe has an average diameter DS1 in the region of the sector S1 and an average diameter DS2 in a region of the sector S2, wherein DS1=DS2 or the diameter DS1 deviates by a maximum of 5%-10% from the diameter DS2.

14. An exhaust-gas mixer consisting of an exhaust-gas mixing pipe according to claim 1 and a mixer housing, wherein the mixer housing has an inlet opening and an outlet opening for exhaust gas and the exhaust-gas mixing pipe is positioned with an end of a pipe opposite the end wall at an outlet opening.

15. The exhaust-gas mixer according to claim 14, wherein the inlet opening has an inflow cross section T, where 0.8 SQT4SQ.

16. The exhaust-gas mixer according to claim 14 between the end of the pipe of the exhaust-gas mixing pipe and the outlet opening there is provided an annular gap having an opening cross section QR, where QRx3 SQ, and where 0.05x30.35.

17. The exhaust-gas mixer according to claim 14, wherein the exhaust-gas mixing pipe has a conical widened portion at the start of the pipe and/or at the end of the pipe.

18. The exhaust-gas mixer according to claim 14, wherein a nozzle is provided with a discharge opening for introducing the additive, wherein the exhaust-gas mixing pipe has the average diameter DS1 in a region of the sector S1 and the discharge opening is a maximum distance ADA from the end wall, where ADAy2 DS1, and where 0.4y20.8.

19. An exhaust system for an internal combustion engine having an exhaust-gas mixer according to claim 14 and an exhaust-gas aftertreatment device such as a DPF and/or a SCR arranged downstream in the direction of flow of the exhaust gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and details of the invention are explained in the claims and in the description and illustrated in the figures, wherein:

(2) FIGS. 1, 2, 3, 4, 5, 6, 7, 8, 9, 9a, 10 and 10a show very different embodiments of the exhaust-gas mixing pipe 1;

(3) FIG. 11 shows a schematic diagram regarding the opening cross section;

(4) FIG. 12 shows a schematic diagram of an exhaust-gas mixer;

(5) FIG. 13 shows a schematic diagram of an exhaust system.

DETAILED DESCRIPTION OF THE INVENTION

(6) Common to all embodiments of an exhaust gas mixing pipe 1 is a housing wall 1.1 having multiple rows 1.3 of openings 1.2, an end wall 2 at the start of the pipe 1.7 and an open end at the end of the pipe 1.6. In addition, a first sector S1 having two rows 1.3 of openings 1.2 having an average opening cross section Q1, therefore two first-order stages M1. The openings 1.2 are each designed as a blade-free recess of the housing wall 1.1. The sum of all the opening cross sections Q1 of a sector S1 is SQ1. The sum of all the opening cross sections Q of all the openings 1.2 of all the rows 1.3 of the exhaust-gas mixing pipe 1 is SQ. SQ10.15 SQ initially applies to the ratio of SQ1 to SQ.

(7) The housing wall 1.1 has a diameter DS1 which corresponds to double the distance from a longitudinal axis L (see FIGS. 9, 9a). The sector S1 has a distance AS1 from the end wall 2, where AS10.2 DS1.

(8) A second sector S2 having multiple stages M2 formed from multiple rows 1.3 of openings 1.2 having an average opening cross section Q2 is provided for all embodiments of the exhaust-gas mixing pipe 1. The sum of all the opening cross sections Q2 of the sector S2 is SQ2. Whilst the embodiments in FIGS. 1, 3-6, 8 and 9 are openings 1.2 which are designed as a formation of the housing wall 1.1, wherein the formed part of the housing wall 1.1 forms a blade 1.4, the respective opening 1.2 is designed as a recess of the housing wall 1.1 which is blade-free in the embodiments in FIGS. 10 and 11. The embodiments in FIGS. 2 and 7 are a mixed variant of openings 1.2. The respective row 1.3 is formed from formations having a blade 1.4, on the one hand, and recesses arranged therebetween, on the other hand. In this case, the average opening cross section Q2 in sector S2 is the quotient formed from the sum of the opening cross sections Q of a row 1.3 divided by the number of openings 1.2 of this row 1.3.

(9) A stage M3 having a row 1.3 of openings 1.2 having an average cross section Q3 is considered as the third sector S3 for the embodiments in FIGS. 1 to 7 and FIG. 9, with the latter being combined with a conical widened portion 1.9 of the exhaust-gas mixing pipe 1 at the end of the pipe 1.6 to achieve a larger diameter DS3 in accordance with the cross-sectional view in FIG. 9a. The diameter DS3 and the ratio thereof to a diameter DS2 regarding the respective opening 1.2 of the sector S2 is shown in FIG. 9a, a cross-sectional view A-A from FIG. 9. SQ3=0.2 SQ applies initially to the ratio of SQ3 to SQ.

(10) As an alternative to the openings 1.2, the embodiments in accordance with FIGS. 8, 10 and 12 have an annular gap 5 at the end side. The latter is limited according to FIG. 12 by means of an outlet opening 4.2 or an outlet connection of a mixer housing 4. There are provided in the circumferential direction three retaining crosspieces 1.8 which join the end of the pipe 1.6 and which are connected to an outlet opening 4.2 of a mixer housing 4 according to FIG. 12. A conical widened portion 1.9 to which the retaining crosspieces 1.8 are joined is provided at the end of the pipe 1.6 according to FIG. 10.

(11) According to the embodiment in FIG. 2 two stages M5, M6 which each have a different opening cross section Q5, Q6 are provided within the sector S2. These are openings 1.2 which are each designed as a blade-free recess of the housing wall 1.1. The two stages M5, M6 should not be considered during the determination of the opening cross section SQ2, so that a separate value is to be determined for the sum of the opening cross sections for the sector S2 having the two stages M5, M6.

(12) According to the embodiments in FIGS. 4, 6 and 7 there is provided a sector S4 which is arranged in each case with a clear distance between the sectors S2 and S3. The sector S4 has six stages M4 according to FIG. 4, three stages M4 according to FIG. 6 and two stages M4 according to FIG. 7, with each having an opening cross section Q4. In the case of the two embodiments in FIGS. 4 and 6 the stages M4 are arranged directly beside one another. According to FIG. 7, the stage M5 is provided between the two stages M4. Whilst the sector S4 has openings 1.2 which are each designed as a blade-free recess of the housing wall 1.1, the stage M5 has openings which are designed as a formation of the housing wall 1.1, wherein the formed part of the housing wall 1.1 forms the blade 1.4. A separate value for the sum of the opening cross sections is to be determined for the sector S4 with the stage M5.

(13) According to the embodiment in FIG. 6 there is provided in the region of the sector S4 a circumferential inlet funnel 8, by means of which the exhaust-gas stream is supplied to the sector S4.

(14) According to FIG. 7 a blade axis 1.5 of the blades 1.4 extends substantially in a tangential direction to the longitudinal axis L. According to FIG. 8 the housing wall 1.1 is designed in a conical form in the region of the sector S2, therefore the blade axis 1.5 of the blades 1.4 does not extend parallel to the longitudinal axis L. However, the respective blade axis 1.5 and the longitudinal axis L are arranged in a joint plane E.

(15) According to FIGS. 10, 10a the opening cross section Q2 over a first partial circumference Ua of approximately 180 which can be turned toward the exhaust-gas stream is half as large as an opening cross section Q2 of an opposite partial circumference Ub of approximately 180 with respect to the longitudinal axis L. The dynamic pressure gradient of the inflow is therefore taken account of. FIG. 10a shows a slightly centric view B-B from FIG. 10. The variation of the opening cross section Q or of the opening density in the lower partial circumference Ub, as can be seen in the side view in FIG. 10, is shown in perspective in FIG. 10a and according to the principle by the hatch pattern density on the housing wall 1.1.

(16) FIG. 11 shows by way of example the opening cross section Q which, according to the definition, is the smallest passage opening. Whereas in the case of a recess 1.2, i.e. a simple hole (left variant), the definition of the opening cross section Q is obvious, the situation can be different when a blade 1.4 is used, depending on the angle of attack. In the case of blades 1.4 set at a steep angle (middle variant) the opening cross section Q of the recess 1.2 is probably also considered, since the circumferential blade gap on three sides will be larger than the blade surface. In the case of a blade 1.4 which is set at a flat angle (right variant), however, the circumferential blade gap on the other side or on three sides is considered as the smallest opening cross section Q, since the formation itself, in this case the blade surface, will be larger.

(17) In the case of an exhaust-gas mixer 3 according to FIG. 12, the mixer housing 4 is provided with an inlet opening 4.1 or an inlet connection and an outlet opening 4.2 or an outlet connection. The inlet opening 4.1 has an inflow cross section T, where 1.3 SQT1.5 SQ. Joined to the outlet connection 4.2 is the exhaust-gas mixing pipe 1, with these being joined by means of the indicated retaining webs 1.8 at the end of the pipe 1.6 which provide the annular gap 5 indicated. Due to the conical widened portion 1.9 of the exhaust-gas mixing pipe 1 or the enlarged diameter of the outlet opening 4.2, a jacket flow of the exiting exhaust gas can be guaranteed in the outlet connection 4.2. The jacket flow surrounds the flow exiting through the exhaust-gas mixing pipe 1, thus preventing additives from being deposited at the outlet connection 4.2 or on a pipe wall. The annular gap 5 has an opening cross section QR, wherein the following formula initially applies: QR<=0.2 SQ.

(18) In the region of the end wall 2 there is provided an injection nozzle 2.1 with a discharge opening 2.2. The discharge opening 2.2 is a shown distance ADA from the end wall 2, where ADA0.5 DS1.

(19) FIG. 13 shows in principle an internal combustion engine 6 having an exhaust system 7, in which an exhaust gas mixer 3 is arranged, which is followed by an exhaust gas after treatment device 7.1.

(20) All of the aforementioned variants for the design of the sectors S1, S2, S3, S4, or additional sectors S5 and S6 having multiple mixing stages M5, M6, as well as the number and the order of the mixing stages M1, M2, M3, M4, M5, M6 themselves are exemplary, and can also be considered in other combinations of the described variations.

LIST OF REFERENCE NUMERALS

(21) 1 Exhaust-gas mixing pipe 1.1 Housing wall 1.2 Opening, recess 1.3 Row 1.4 Blade 1.5 Blade axis 1.6 End of pipe 1.7 Start of pipe 1.8 Retaining crosspiece 1.9 Widened portion 2 End wall 2.1 Injection nozzle, nozzle 2.2 Discharge opening 3 Exhaust-gas mixer 4 Mixer housing 4.1 Inlet opening 4.2 Outlet opening 5 Annular gap 6 Internal combustion engine 6.1 Discharge opening 7 Exhaust system 7.1 Exhaust-gas aftertreatment device 8 Inlet funnel ADA Distance of 6.1 AS1 Distance S1, S2 AS2 Distance between S1 and S2 DS1 Diameter for S1 DS2 Diameter for S2 DS3 Diameter for S3 E Plane f Factor 12 L Longitudinal axis l Factor k Factor M Stage M1 Stage M2 Stage M3 Stage M4 Stage M5 Stage M6 Stage Q Opening cross section Q1 Opening cross section of M1 Q2 Opening cross section of M2 Q3 Opening cross section of M3 Q4 Opening cross section of M4 Q5 Opening cross section of M5 Q6 Opening cross section of M6 QR Opening cross section of 5 qa Value qb Value r2 Distance, radius r3 Distance, radius S1 Sector S2 Sector S3 Sector S4 Sector S5 Sector S6 Sector SQ Sum Q SQ1 Sum Q1 of S1 SQ2 Sum Q1 of S2 SQ3 Sum Q3 of S3 SQ4 Sum Q4 of S4 T Inflow cross section of 4.1 U Circumference Ua Partial circumference Ub Partial circumference UR Circumferential direction x1 Factor x2 Factor x3 Factor y1 Factor y2 Factor