Field of the invention
The present disclosure relates to a device for dosing an aqueous solution in exhaust gas pipe of a vehicle.
Background of the invention
Exhaust gas treatment devices and strategies widely used in vehicle ensure that the exhaust gases are treated and harmful emissions coming out of a vehicle are kept as low as possible. The most popular exhaust gas treatment devices and strategy is dosing an aqueous solution to treat oxides of nitrogen. One of the many components of the exhaust gas is different oxides of nitrogen that contribute to the greenhouse effect and other types of contamination. Hence emission norm around the world require that the oxides of nitrogen be treated to convert them to elemental nitrogen before they are let out into the atmosphere. One of the most popular methods of treating the exhaust gases to convert the oxides of nitrogen to elemental nitrogen is by using an aqueous solution.
An aqueous solution dosing device is used downstream of the exhaust gas pipe. The dosing mechanism doses a metered quantity of the aqueous solution into the exhaust gas path. The metered quantity of the aqueous solution reacts with the oxides of nitrogen and converts it to elemental nitrogen. The dosing device comprises an injector which is the device responsible for dosing the metered quantity of aqueous solution in

the exhaust gas path. The injector sprays the metered quantity of the aqueous solution. Packaging constraint in vehicles have led to the widespread use of compact mixing sections for mixing aqueous solution with exhaust gas. These compact mixing sections lead to a lot of recirculation of aqueous solution vapors is near the tip of injector while dosing. Recirculation near or towards injector tip causes crystallization and deposition of aqueous solution on the tip. This would lead to the failure of dosing system due to blockage of injector.
[0004] Patent Application WO13035112A1 “A device for dosing an
aqueous solution in an exhaust gas path” discloses a device for dosing an aqueous solution in an exhaust gas path is disclosed. The device comprises a dosing module having a dosing valve. The device is characterized by a flange located in the exhaust gas path. A flange interface comprising a protection feature and a mounting feature located at the end of the flange distant from the exhaust gas path and a heat sink located on the flange interface adapted to receive a dosing valve. However this design doesn’t solve the problem of injector tip crystallization as discussed above.
Brief description of the accompanying drawings
[0005] An embodiment of the invention is described with
reference to the following accompanying drawing.
[0006] Fig. 1 depicts a device (100) for dosing an aqueous solution
in exhaust gas pipe of a vehicle.

Detailed description of the drawings
[0007] Figure 1 depicts a device (100) for dosing an aqueous
solution in exhaust gas pipe (106) of a vehicle. The device comprises a housing, a flange (105) welded to the housing (102) and at least an injector (101). The injector (101) is located inside the housing. The device is characterized by a sleeve (107) mounted on the circumference of the tip of the injector (101) and interior to the flange (105). The sleeve (107) has inlet (103) and outlet (104) ports with direction flaps. The sleeve (107) is of the shape of a frustum.
[0008] In an embodiment, the device (100) for dosing an aqueous
solution in exhaust gas pipe (106) is mounted vertically at right angles on top of the exhaust gas pipe (106). In another embodiment of the invention, the device (100) for dosing an aqueous solution in exhaust gas pipe (106) is mounted at various angles inclined to the circular cross-section of the exhaust gas pipe (106). In an embodiment of the invention described above, where the device (100) is mounted vertically and at right angles on top of the exhaust gas pipe (106), the need for a flange can be dispensed with. In this embodiment the housing (102) is welded to the exhaust gas pipe (106) and the sleeve (107) is placed inside the exhaust gas pipe (106). The inlet (103) and outlet (104) ports of the sleeve (107) here play an important role by allowing exhaust gas to enter the sleeve (107) and avoiding a build-up of back-pressure in the exhaust gas pipe (106).

[0009] The injector (101) located inside the housing (102) injects
diesel exhaust fluid into the exhaust pipe. The diesel exhaust fluid comprises a urea based aqueous solution. This urea based solution is used to carry out selective catalytic reactions in the exhaust gas pipe (106). When this urea based aqueous solution is injected into the exhaust pipeline, the aqueous urea vaporizes and decomposes to form ammonia and carbon dioxide. Further the ammonia reacts with Nitrogen Oxides (NOx) and reduces them into water and elemental nitrogen, which are both harmless. Then these are released through the exhaust.
[0010] The exhaust gas coming through the pipe enters the device
through the flange (105). In conventional systems, the swirling motion of the gas inside the flange (105) leads to crystallization of urea injected by the injector (101). Hence an important aspect of this invention is the sleeve (107) of the injector (101). The sleeve (107) of the injector (101) prevents unwanted quantities of exhaust gases from entering the region near the injector (101). The sleeve (107) of the injector (101) is also provided with inlet (103) and outlet (104) ports. These inlet (103) and outlet (104) ports allow an optimum amount of exhaust gas to enter the flange (105) to avoid building up of a back pressure.
[0011] Further these inlet (103) and outlet (104) ports of the sleeve
(107) are equipped with direction flaps. These direction flaps ensure that the exhaust gas and the aqueous vapors are directed towards the exhaust gas pipe (106) and not allowed to re-circulate near the tip of the injector

(101). Further the cone angle of this sleeve (107) will be more than the spray cone angle to avoid spray impingement on the walls of sleeve (107). The sleeve (107) would force the flow downwards, away from the tip of urea injector (101), reducing the probability of urea vapors moving towards injector (101) tip.
[0012] This idea to develop a device for dosing an aqueous solution
in exhaust gas pipe (106) of a vehicle enhances the efficiency of the injector (101) and the Selective Catalytic System as a whole. In conventional systems, when crystals start growing around the tip of the injector it affects the NOx conversion efficiency. In order to remove these crystals, a service regeneration needs to be triggered in the system. In this, the operating temperature of the injector tip is brought to > 450 deg. C to remove the crystals. However this procedure causes additional fuel to be burnt and reduces the fuel efficiency.
[0013] It must be understood that the embodiments explained in the
above detailed description are only illustrative and do not limit the scope of this invention. Any modification to this device for dosing an aqueous solution in exhaust gas pipe (106) of a vehicle are envisaged and form a part of this invention. Thus many modification and embodiments are envisaged to be within the scope of this invention. The scope of this invention is limited only by the claims.

We Claim:
1. A device for dosing an aqueous solution in exhaust gas pipe (106)
of a vehicle, the device comprising a housing (102), a flange (105)
welded to the housing (102) and at least an injector (101), where
the injector (101) is located inside the housing, characterized in that
device
a sleeve (107) mounted on the circumference of the tip of the injector (101) and interior to the flange (105).
2. The device for dosing an aqueous solution in exhaust gas pipe (106) of a vehicle as claimed in claim 1, where the sleeve (107) has inlet (103) and outlet (104) ports with direction flaps.
3. The device for dosing an aqueous solution in exhaust gas pipe (106) of a vehicle as claimed in claim 1, where the sleeve (107) is of the shape of a frustum.