Claims:We claim:

1. An apparatus (100) for mixing reductant in an exhaust path (105) of a vehicle, said apparatus (100) comprises
? a mixing tube (110) placed in said exhaust path (105) in alignment with a reductant-injector (115) and having a plurality of inlet holes (120);
? a reductant-breaker (125) in said mixing tube (110) to break said reductant sprayed from said reductant-injector (115);
? characterized in said mixing tube (110)
• at least one deflecting tab (130) to direct the exhaust gas entering said mixing tube (110) through said inlet holes (120), towards said reductant-breaker (125).
2. The apparatus (100) of claim 1, wherein said mixing tube (110) comprises said plurality of inlet holes (120) on first side.
3. The apparatus (100) of claim 1, said mixing tube (110) is completely closed on second side.
4. The apparatus (100) of claim 1, wherein said reductant-breaker (125) is in the form of a fan.
5. The apparatus (100) of claim 1 further comprises at least one flap (135) in said mixing tube (110) to exit the exhaust gas mixed with said reductant towards the downstream side of said mixing tube (110).
6. The apparatus (100) of claim 5 wherein said at least one flap (135) is provided at lower part of said mixing tube (110).
7. The apparatus (100) of claim 5 wherein said at least one flap (135) creates a swirl flow (140) of said exhaust gas mixed with said reductant.
8. The apparatus (100) of claim 5 further comprises additional inlet holes (145) to allow entry of exhaust gas directly towards said lower part of said mixing tube (110).
, Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed:
Field of the invention:
[0001] The present invention relates to an apparatus for mixing a reductant especially a urea solution in an exhaust path of a vehicle for exhaust treatment. More specifically, it relates to a dual-stage reductant mixing apparatus.

Background of the invention:
[0002] Selective catalytic reduction (SCR) systems are very effective solutions for exhaust treatment. In SCR systems, reducing agent or reductant such as urea solution is injected with an injector to reduce the pollutants such as nitrogen oxide (NOx).

[0003] However, if urea solution is not mixed well with the exhaust gas flowing in the exhaust path, urea is deposited and crystallized on the internal walls of the exhaust tube. This results in poor urea solution utilization as well as adverse impact on system performance on NOx conversion efficiency. Further, formation of such deposits in exhaust path can lead to several issues like increase in system back pressure, corrosion of exhaust path, poor ammonia distribution in SCR catalyst and finally non-compliance of emission legal limits. In short, such mixing sections are less robust and fail to offer robust SCR calibration over the lifetime.

[0004] A Chinese patent publication CN106110980A discloses a urea solution mixer for a selective catalytic reduction system of a vehicle. The mixer comprises an outer tube with inlet holes and an inner tube with outlet holes tubular structure with holes.

Brief description of the invention:
[0005] The invention discloses an apparatus for mixing a reductant such as urea solution in an exhaust path of a vehicle. The apparatus comprises a mixing tube placed in the exhaust path in alignment with a reductant-injector and having a plurality of inlet holes. A reductant-breaker is provided in the mixing tube to break the reductant sprayed from the reductant-injector. The mixing tube comprises at least one deflecting tab to direct the exhaust gas entering to the mixing tube through the inlet holes, towards the reductant-breaker. The mixing tube comprises the plurality of inlet holes on first side, while it is completely closed on its second side.

[0006] In one embodiment of the invention, the reductant-breaker is in the form of a fan. The apparatus further comprises at least one flap in the mixing tube to exit the exhaust gas mixed with the reductant towards the downstream side of the mixing tube. The at least one flap is provided at lower part of the mixing tube and creates a swirl flow of the exhaust gas mixed with the reductant. Additional inlet holes are provided in the mixing apparatus to allow entry of exhaust gas directly towards the lower part of the mixing tube.

Brief description of the accompanying drawings:
[0007] An embodiment of the disclosure is described with reference to the following accompanying drawing,

[0008] Fig. 1 illustrates a schematic perspective view of an apparatus for mixing reductant in an exhaust path, according to an embodiment of the present invention;
[0009] Fig. 2 illustrates another schematic perspective view of an apparatus for mixing reductant in an exhaust path, according to an embodiment of the present invention, and

[0010] Fig. 3 shows a side view of a mixing apparatus having a perforated plate, according to an embodiment of the present invention.

Detailed description of the embodiments:
Fig. 1 illustrates a schematic perspective view of an apparatus for mixing reductant in an exhaust path, according to an embodiment of the present invention. Selective Catalytic Reduction (SCR) system is used for effectively controlling the emission of the pollutants by reducing Nitrous Oxide (NOx) into elemental nitrogen. Reducing agents or Reductants such as Urea is sprayed in the exhaust path 105 by a reductant injector 115. The mixing apparatus 100 mixes the reductant with the exhaust gas coming out of the engine.

[0011] The mixing apparatus 100 comprises a mixing tube 110 placed inside the exhaust path 105 in alignment with the reductant-injector 115. In other words, the mixing tube 110 is placed inside the exhaust path 105 below the reductant-injector 115 across the flow of the exhaust gas. The mixing tube 110 has a plurality of inlet holes 120 on its first side to allow entry of the exhaust gas. The second side of the mixing tube 110 is completely closed; therefore, the exhaust gas entered via the inlet holes 120 passes only towards the lower part of the mixing tube.

[0012] A reductant-breaker 125 is placed inside the mixing tube 110 to break the reductant sprayed from the reductant-injector 115. In an embodiment of the invention, the reductant-breaker 125 in the form of a fan. The shape or form of the reductant-breaker is not limited to fan or ring. The reductant-breaker 125 is alternately called as ‘spray-breaker’. The reductant-breaker 125 breaks the reductant into smaller particles to enable effective and homogeneous mixing of the reductant with the exhaust gas. This helps in improving the efficiency of the exhaust treatment and minimizing the pollution considerably.

[0013] The mixing tube 110 comprises one or more deflecting tabs 130 to direct the exhaust gas entering the mixing tube 110 towards the reductant-breaker 125. In an embodiment of the invention, the deflecting tabs 130 are provided at the inner wall of the mixing tube 110.

[0014] As the deflecting tabs 130 direct the exhaust gas towards the reductant breaker 125, the exhaust gas mixes well with the broken down particles of the reductant. Further, formation of deposits of the reductant on the internal walls of the exhaust pipe is avoided. In addition, the mixing concept of the present invention ensures better evaporation of the reductant and improves the efficiency of the SCR system.

[0015] The mixing apparatus 100 further comprises one or more flaps 135 to direct or exit the exhaust gas mixed with the reductant out of the mixing tube 110 towards the downstream side of the mixing tube 110.

[0016] Fig. 2 illustrates another schematic perspective view of an apparatus for mixing reductant in an exhaust path, according to an embodiment of the present invention. Figure 2 shows a view of a section of the exhaust pipe from the tail pipe or exit side.

[0017] As shown in figure, the flaps 135 are provided at the lower part of the mixing tube 110. The flaps 135 exit the exhaust gas mixed with the reductant out of the mixing tube 110 towards its downstream side, that is, towards an SCR & ammonia-slip-catalyst or towards a tail pipe. The SCR & ammonia-slip-catalyst or the tail pipe is not shown in the figure 2. The flaps 135 create a swirl flow 140, which ensures homogenous mixing of the exhaust gas and the reductant, avoids dead-zones, and prevents deposit and crystallization of the reductant. As a result, the efficiency of the SCR system is improved remarkably. The life of the exhaust pipe is improved considerably.

[0018] The mixing apparatus 100 comprises additional holes 145 (shown in figure 1) to directly allow entry of some part of the exhaust gas coming from engine to the lower part of the mixing tube 110. This facilitates free flow of exhaust gas and avoids congestion in the upper part of the mixing tube 110.

[0019] Fig. 3 shows a side view of a mixing apparatus having a perforated plate, according to an embodiment of the present invention. In one embodiment of the invention, the second side of the mixing tube 110 comprises a perforated plate 40, instead of being completely closed. The perforate plate 140 ensures uniform mixing and distribution of the exhaust gas with the reductant. The mixing apparatus 100 of the invention provides two stage mixing of the exhaust gas with the reductant using the reductant breaker 125 and also by creating swirl flow. The mixing apparatus 100 effectively contributes for the control of exhaust emissions from the vehicle.

[0020] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.