[001] The present invention relates to development of urea mixer for exhaust and after treatment system towards enhancing the homogeneity of aqueous urea and exhaust gas to meet the Bharat Stage VI emission norms.
BACKGROUND OF THE INVENTION
[002] In view of the increasingly stringent emission norms laid out by the government, it is necessary to have a complex, smart and robust After Treatment System for treating the exhaust gas. Carbon Monoxide (CO), Unburnt Hydrocarbons (HC), Particulate Matter (PM) and Nitrogen Oxides (NOx) are the major constituents of the exhaust gas that are regulated. In a modern after treatment system, CO, HC are controlled by the Diesel Oxidation Catalyst, and the PM is controlled by the Diesel Particulate Filter (DPF).
[003] On the other hand, NOx is controlled by injecting an aqueous solution of urea into the stream of exhaust gas inside the after treatment system and with the help of Selective Catalytic Reduction (SCR). For the effective control of NOx, it is important to achieve a good Flow Distribution Index (FDI), Urea Distribution Index (UDI), uniform velocity distribution, and a thorough mixing of the injected urea and the exhaust gas. Failing to achieve the same will result in the formation of undesirable urea crystal deposits inside the after treatment system leading to increased urea consumption, increased back pressure and not meeting the emission performance.
[004] Therefore, the objective of this invention is to develop a mixer that would ensure that all the flow performance parameters and ultimately, the emission standards are met.

[005] In one aspect, an embodiment herein provides a urea mixer assembly for uniform mixing of urea and exhaust gas. The urea mixer assembly comprises a mixing tube, a urea injector, a Z-shape plate, and a splash plate. The urea injector injects the urea into the mixing tube to mix the exhaust gas with the urea uniformly. The mixing tube having deflectors at an upper half and bottom half. The deflectors at the upper half of the mixing tube have openings that are opposite in directions to the deflectors at the bottom half of the mixing tube which creates a swirl inside the mixing tube in counter clockwise direction until the end of the mixing tube. The Z-shape plate directs the flow of the exhaust gas towards the upper half of the mixing tube for uniform mixing of urea and exhaust gas. The splash plate is coupled with the mixing tube at inside. Further, the splash plate disperses and evaporates any non-evaporated injected urea in the swirl. In one embodiment, the material which is used to manufacture the Z-shape plate, the deflectors and the mixing tube is, but not limited to, SS439 & SS441.
[006] The urea mixer further comprises an adaptor mounting plate, and an adaptor. In one embodiment, the adaptor mounting plate and the adaptor are welded together and are mated to the urea injector using a V-Clamp to ensure optimal tip penetration inside the mixer assembly.
[007] In another embodiment, the exhaust gas flows down the mixing tube, past the splash plate and out of the urea mixer assembly.
OBJECT OF THE INVENTION:
[009] The main objective of this invention is to develop a mixer that would ensure the proper mixing of injected aqueous urea solution and the exhaust gas flowing through the system in order to meet the Bharat Stage VI emission norms.

[010] Another objective of this invention is to produce and design the urea mixer assembly for attaining higher mixing uniformity.
[011] Yet another objective of this invention is to produce and design the urea mixer assembly for attaining low back pressure.
[012] Yet another objective of this invention is to produce and design the urea mixer assembly for attaining uniform velocity distribution and Urea vapour mass fraction distribution by strategically directing the exhaust gas through this mixer.
[013] Yet another objective of this invention is to produce and design the urea mixer assembly that facilitates the proper mixing of injected aqueous urea and exhaust gas and also to meet the flow performance parameters, thereby meeting the emission targets. The Z-shape plate ensures uniform mixing of the urea with the exhaust gas.
[014] Yet another objective of this invention is to produce a splash plate that disperses injected urea which are not evaporated in the swirl.
[015] Yet another objective of this invention is to produce an adaptor and mounting plate that ensures optimal tip penetration inside the mixer to reduce the risk of deposits at the injector tip.
[016] Yet another objective of this invention is to produce a unique mixing tube with specialised deflectors that ensures good swirl and evaporation of injected urea.
BRIEF DESCRIPTION OF THE DIAGRAMS:
[016] A preferred embodiment of the invention is described below with reference to the accompanying drawing, in which:

[017] FIG. 1 illustrates a front view of the urea mixer assembly according to an embodiment herein;
[018] FIGs. 2a and 2b illustrate an isometric view of a Z-shape plate of FIG. 1 according to an embodiment herein;
[019] FIG. 3 illustrates an isometric view of a mixing tube of FIG. 1 according to an embodiment herein;
[020] FIG. 4 illustrates an isometric view of an adaptor mounting plate of FIG. 1 according to an embodiment herein;
[021] FIG. 5 illustrates an isometric view of a splash plate of FIG. 1 according to an embodiment herein;
[022] FIG. 6 illustrates an isometric view of a urea injector of FIG. 1 according to an embodiment herein;
[023] FIG. 7 illustrates an isometric view of an adaptor of FIG. 1 according to an embodiment herein; and
[024] FIG. 8 illustrates an isometric view of the urea mixer assembly of FIG. 1 according to an embodiment herein.
DETAILED DESCRIPTION OF THE DIAGRAMS:
[025] With reference to Figures 1 to 8, the urea mixer assembly (100) is developed to ensure uniform mixing of urea and exhaust gas at all conditions (e.g. emission norms). The urea mixer assembly (100) includes a mixing tube (2), a urea injector (5), a Z-shape plate (1), and a splash plate (4). The urea injector (5) is placed at top of the mixing tube (2).

[0026] The exhaust gas enters the mixer assembly (100) and it is diverted towards the top of the mixer by the Z-shape plate (1) and into the mixing tube (2). The urea injector (5) injects the urea into the mixing tube (2) to mix the exhaust gas with the urea uniformly.
[027] The deflectors (9a) at the upper half (10) of the mixing tube (2) have openings that are opposite in directions to the deflectors (9b) at the bottom half (11). These unique opposite facing deflectors (9z, 9b) create a swirl inside the pipe in counter clockwise direction until the end of the mixing tube (2).
[028] The splash plate (4) is placed inside the mixing tube (2) which disperses and evaporates any non-evaporated stream of injected urea back into the swirl. The adaptor mounting plate (3) and the adaptor (6) are welded together and the same is mated to the injector using a V-Clamp (8).
[029] The exhaust gas flows down the mixing tube (2), past the splash plate (4) and exits the urea mixer assembly (100).

[031] The below table no. 2 illustrates the test details (experimental results) of the present invention showing that the present invention meets BSVI emission norms.

1. An urea mixer assembly (100) for mixing of urea and exhaust gas uniformly,
comprising:
a mixing tube (2);
an urea injector (5) that injects the urea into said mixing tube (2) to mix the exhaust gas with the urea uniformly,
characterized in that,
said mixing tube (2) having deflectors (9a, 9b) at an upper half (10) and bottom half (11), said deflectors (9a) at the upper half (10) of the mixing tube (2) have openings that are opposite in directions to the deflectors (9b) at the bottom half (11) of the mixing tube (2) which creates a swirl inside the mixing tube (2) in counter clockwise direction until the end of the mixing tube (2);
a Z-shape plate (1) that directs the flow of the exhaust gas towards the upper half of the mixing tube (2); and
a splash plate (4) that is coupled with said mixing tube (2) at inside, said splash plate (4) disperses and evaporates any non-evaporated stream of injected urea into the swirl.
2. The urea mixer assembly as claimed in claim 1, comprising:
an adaptor mounting plate (3); and
an adaptor (6), wherein said adaptor mounting plate (3) and said adaptor (6) are welded together and are mated to the urea injector (5) using a V-Clamp (8) to ensure optimal tip penetration inside the urea mixer assembly (100).
3. The urea mixer assembly as claimed in claim 1, wherein the exhaust gas flows down
the mixing tube (2), past the splash plate (4) and exits the urea mixer assembly (100).