Field of the invention
Present invention relates generally to an Exhaust gas treatment for internal combustion engines. The invention relates in specific to a system for preventing crystallization of urea near injector tip of an exhaust gas after treatment system.
Background of the invention
Exhaust gas treatment for internal combustion engines are known in the prior arts. The exhaust gas treatment (EGT) systems are used to reduce the exhaust emissions coming out of the internal combustion engine. The EGT system of diesel engines typically reduces hydro carbons, carbon monoxide, nitrogen oxide and particulate matter. A selective reduction catalyst that includes a particulate filter that collects particulates in exhaust gas in the middle of an exhaust pipe and that can selectively react NOx with ammonia even in the presence of oxygen on the downstream side of the particulate filter In this case, urea water is added as a reducing agent between the selective reduction catalyst and the particulate filter so as to simultaneously reduce particulates and NOx.
Current dosing modules or urea injectors come with a provision of coolant cooling to reduce the tip temperature during events like DPF regeneration, Hot shut down and even during normal mode for higher specific power engines. The cooling is provided to prevent the damage of injector tip at higher temperatures. But in certain cases when engine has a high capacity coolant pump or coolant flow rate is high through injector body, it leads to excessive cooling of injector housing leading to urea deposits in DM tip including the housing through which coolant flows. These deposits can block the injector holes, can lead to spray collapse, can create ammonia imbalance directly affecting the performance of SCR system which may result in insufficient NOx conversion. Prolonged exposure to deposits can also lead to issues like corrosion. Currently the coolant flow to injector is not

controlled. The coolant connectors are directly connected to engine cooling circuit with no control over flow rate / cooling efficiency.
[0004] When urea crystallization appears, as a part of or even the complete exhaust pipe of the engine will be blocked. The waste flow will be changed, conversion rate will be reduced, and the exhaust will be affected. The distribution of fuel agent will not be homogeneous and finally, lead to blockage of the injection nozzle.
[0005] Existing solutions for the above-mentioned problems includes urea crystals are easy to dissolve in water, so the automotive urea needs to avoid the contact with dry air, especially at the injection valve and exhaust pipe. At 100~130 degrees centigrade, the water of the urea solution evaporates very quickly. So it is necessary to avoid storing urea solution at this temperature. Urea crystal is a white powder, with a melting point at 190 degrees. At this high temperature, the urea crystal can be dissolved in water, changed into the crystals.
[0006] The prior art US8893470 discloses a method for preventing clogging of a urea injection nozzle in an after-run operation of a selective catalytic reduction (SCR) system which supplies urea stored in a urea tank through a supply module, a urea injection nozzle and a urea line connecting the supply module and the urea injection nozzle, the method may include an emptying step where the urea is withdrawn into the urea tank by creating negative pressure in the supply module and a pressure equilibrium step where the pressure in the supply module is recovered by stopping creation of negative pressure in the supply module, wherein in the pressure equilibrium step, whether to forcibly inject the urea is controlled on the basis of pressure after a predetermined time has passed since the pressure equilibrium step began.
Brief description of the accompanying drawing

[0007] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
[0008] Fig. 1 illustrates exhaust gas after treatment system for an internal combustion engine, according to one embodiment of the invention.
[0009] FIG. 2 is an example process for preventing urea deposits on an injector tip for an internal combustion engine, using the system of FIG. 1, according to the aspects of the present technique.
Detailed description of the embodiments
[0010] FIG. 1 illustrates an exhaust gas after treatment (hereinafter EGT) system 100,
an internal combustion engine 102 in a vehicle. The EGT system 100 includes a dosing
module 104, a coolant circuit 106, a temperature sensor 108, a controller 112 and a
flow control device 110. Each component of the EGT system 100 is further described
below.
[0011] The dosing module 104 includes an injector having a discharge opening and configured to inject a reducing agent into a duct of the EGT system 100. The dosing module 104 is supported on a duct of the EGT system 100 and is configured to inject the reducing agent from a reservoir into the duct. The reducing agent is, for example, an aqueous urea solution of 32.5 percent urea and 67.5 percent deionized water, frequently sold under the registered trademark AdBlue. The EGT system 100 includes a pump that directs fluid from the reservoir to the dosing module 104.
[0012] The coolant circuit 106 includes a delivery portion 12 that directs coolant from the internal combustion engine 102 to an inlet of a coolant passageway formed in the dosing module 104, and a return portion 14 that returns coolant from an outlet of the coolant passageway and returns it to the internal combustion engine 102. Herein the

delivery portion 12 of the coolant passageway is the direction of the coolant through which cold coolant will flow to the injector body through the dosing module 104. In the same context, return portion 14 of the coolant passageway is the direction of the coolant through which hot coolant will flow through the injector body.
[0013] The temperature sensor 108 is placed at upstream of dosing module 104 of the engine 102 and configured to acquire temperature of the exhaust gases in the EGT system 100.
[0014] The flow control device 110 is disposed in between the dosing module 104 and the coolant circuit 106. The flow control device 110 is configured to control coolant direction through the coolant circuit 106 based on the temperature of the exhaust gases in the EGT system (100). The acquired temperature is used to trigger the flow control device 110 to control the direction of the coolant in the EGT system 100.
[0015] In one embodiment, in case of increased temperature of the exhaust gases to a certain predefined temperature value, the flow control device 110 will get actuated and open the coolant flow for the delivery portion 12 carrying cold coolant engine in through the injector body to cool down the injector tip. In an another example, in case of decreased temperature of the exhaust gases to certain predefined temperature value, the flow control device 110 will get actuated and open coolant flow for return portion 14 for carrying hot coolant flow through the injector body, maintaining sufficient temperatures in and around dosing tip to avoid deposits.
[0016] In one embodiment, the EGT system 100 includes a controller 112 which is coupled in communication with the flow control device 110. The controller 112 is configured to any change in mode of operation of the internal combustion engine 102. In one embodiment, the controller 112 may include any electronic control unit. In this embodiment, the mode of operation of the engine 102 may include normal mode and

regeneration mode. The controller 112 controls the internal combustion engine 102 and in so doing receives signals from the temperature sensor 108 concerning operating parameters of the internal combustion engine 102 and processes the temperature signals to actuate the flow control device 110.
[0017] As soon as the change in operation mode of engine is detected, the flow control device 110 will actuate and change the direction of flow of the coolant. The flow control device 110 will change the direction of the coolant by changing the coolant passage way from delivery portion 12 to return portion 14 or vice versa. For example, on detection of regeneration mode, the temperature of the exhaust gases is higher than a pre-defined temperature value, the controller 112 will communicate this to the flow control device 110. After getting this information from the controller 112, the flow control device 110 will change the direction of flow of the coolant, the delivery portion 12 will get actuated, and now the direction of the coolant through which cold coolant will flow to the injector body through the dosing module 104, to cool down the injector tip. Similarly on detection of normal operating mode of engine, return portion 14 of the coolant passageway gets actuated by the flow control device 110, and now the direction of the coolant through which hot coolant will flow through the injector body, maintaining sufficient temperatures in and around dosing tip to avoid deposits.
[0018] FIG. 2 is an example process 200 for preventing urea deposits on an injector tip for an internal combustion engine 102, using the system of FIG. 1, according to the aspects of the present technique.
[0019] At step 201, temperature (Te) of exhaust gases passing through exhaust pipe of the engine 102, is detected by using a temperature sensor 108 placed at upstream of a dosing module 104 of the engine 102. If the detected temperature (Te) at step 201, is greater than a pre-defined value of temperature (Tc), at step 202 the direction of cold coolant through the engine to the injector tip is actuated, by using a flow control device

110. On detecting temperature (Te) greater than a pre-defined value of temperature (Tc), the direction of cold coolant through the engine to the injector tip is actuated to cool down the injector tip.
[0020] If the detected temperature (Te) at step 201, is lesser than a pre-defined value of temperature (Tc), at step 203 the direction of hot coolant through the engine to the injector tip is actuated, by using a flow control device 110. On detecting temperature (Te) is lesser than the pre-defined value of temperature (Tc), the direction of hot coolant through the engine to the injector tip is actuated (203) to maintain sufficient temperatures in and around dosing tip to avoid deposits. In this embodiment, the flow control device 110 is disposed in between the dosing module 104 and the coolant circuit 106. The flow control device 110 is configured to control coolant direction through the coolant circuit 106 of fig. 1, based on the temperature of the exhaust gases in the EGT system (100).
[0021] 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.

CLAIMS We Claim:
1. An exhaust gas after treatment system (100) for an internal combustion engine
(102), comprising:
a dosing module (104) comprising an injector having a discharge opening and configured to inject a reducing agent into a duct of the exhaust gas after treatment system (100);
a coolant circuit (106) comprising a delivery portion (12) that directs coolant from the internal combustion engine (102) to an inlet of a coolant passageway formed in the dosing module (104), and a return portion (14) that returns coolant from an outlet of the coolant passageway and returns it to the internal combustion engine (102);
a temperature sensor (108) placed at upstream of dosing module (104) of the engine and configured to acquire temperature of the exhaust gases in the exhaust gas after treatment system (100); and
a flow control device (110) disposed in between the dosing module (104) and the coolant circuit (106), wherein the flow control device (110) is configured to control coolant direction through the coolant circuit (106) based on the temperature of the exhaust gases in the exhaust gas after treatment system (100), wherein the acquired temperature is used to trigger the flow control device (110) to control the direction of the coolant in the exhaust gas after treatment system (100).
2. The exhaust gas after treatment system (100) as claimed in claim 1, further comprises a controller (112) coupled in communication with the flow control device (110) and configured to detect any change in mode of operation of the engine (102).
3. The exhaust gas after treatment system (100) as claimed in claim 3, the mode of operation of the engine (102) includes normal mode and regeneration mode.

4. The exhaust gas after treatment system (100) as claimed in claim 2, wherein the
flow control device (110) further configured to change the direction of the coolant
by changing the coolant passage way from delivery portion (12) to return portion
(14) or vice versa.
5. A method (200) for preventing urea deposits on an injector tip for an internal
combustion engine (102), the method comprising:
detecting (201) temperature (Te) of exhaust gases passing through exhaust pipe
of the engine (102), by using a temperature sensor (108) placed at upstream of a
dosing module (104) of the engine (102);
if the detected temperature (Te) is greater than a pre-defined value of temperature
(Tc), actuating (202) the direction of cold coolant through the engine to the
injector tip, by using a flow control device (110);
if the detected temperature (Te) is lesser than the pre-defined value of temperature
(Tc), actuating (203) the direction of hot coolant through the engine to the injector
tip by using a flow control device (110).
6. The method as claimed in claim 6, on detecting temperature (Te) greater than a pre-defined value of temperature (Tc), the direction of cold coolant through the engine to the injector tip is actuated (202) to cool down the injector tip.
7. The method as claimed in claim 6, on detecting temperature (Te) is lesser than the pre-defined value of temperature (Tc), the direction of hot coolant through the engine to the injector tip is actuated (203) to maintain sufficient temperatures in and around dosing tip to avoid deposits.