Field of the invention
This invention relates to a system to regulate temperature of an exhaust gas in a vehicle and a method thereof.
Background of the invention
A vanadium SCR (selective catalytic reduction) technology offers a low cost, robust and promising solution to meet legislative targets for non-road emission legislation like CEV stage IV and CPCB4+. A SCR system is defined, which uses predominantly Vanadium SCR for meeting NOx conversion targets when the temperature is between a range of 250-500 degrees. Unfortunately, high performance of vanadium catalyst is limited at temperature less than 250 OC. Due to low power density engines, engine out temperatures are on the lower side and it becomes difficult to meet performance targets with vanadium catalyst.
A Prior art document US7998423 discloses a selective catalytic reduction (SCR) filters that effectively provide simultaneous treatment of particulate matter and NOx. The SCR filter can include a fiber matrix wall flow filter comprising a plurality of non-woven inorganic fibers and a chabazite molecular sieve SCR catalyst on the fiber matrix wall flow filter. By combining a fiber matrix wall flow filter with a chabazite molecular sieve SCR catalyst, high catalyst loading can be achieved without causing excessive back pressure across the filter when implemented in emission treatment systems.
Brief description of the accompanying drawing
Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:
Figl illustrates a system to regulate temperature of an exhaust gas in a vehicle, in accordance with an embodiment of the invention;
Fig.2 illustrates the system to regulate temperature of the exhaust gas in the vehicle, in accordance with an embodiment of the invention; and

[0007] Fig.3 illustrates a system to regulate a temperature of an exhaust gas in a vehicle in accordance with an embodiment of the invention.
Detailed description of the embodiments
[0008] Fig.1 illustrates a system to regulate temperature of an exhaust gas in a vehicle, in accordance with one embodiment of the invention. The system 11 comprises a diesel oxidization catalyst (DOC) 12 and a SCR unit 14 positioned in an exhaust path 13. The system 11 comprises a temperature sensor 16 positioned upstream of the DOC 12 to detect temperature of an exhaust gas flowing in the exhaust path 13. The vehicle 11 further comprises a control unit 18 connected to the temperature sensor 16 and to an electronically controlled coolant unit 20. The device 10 comprises a cover 22 formed as a chamber enclosing the exhaust path 13 located between the DOC 12 and the SCR unit 14. The cover 22 comprises an inlet 24 and an outlet 26 for facilitating a flow of a coolant from the electronically controlled coolant unit 20 over the exhaust path 13, to regulate the temperature of the exhaust gas in the vehicle 11.
[0009] Further, the construction of the system 11 and the components of the system 11 and their working are explained below. The system 11 comprises an engine 22 connected to the diesel oxidation catalyst (DOC) 12 positioned in the exhaust path 13. The DOC 12 is used to convert the exhaust gas emitting from the engine 22 into less harmful gas during the working of the vehicle. The DOC 12 is used to reduce the carbon and the sulphur content in the exhaust gas before reaching the SCR unit 14. The working of the DOC 12 and the engine is very well known in the state of the art, so hereby, the working and the construction of the engine 22 and the DOC 12 is not explained in the present document. The SCR unit 14 comprises a catalyst, arranged in the form of a coating on an inert support (not shown). The SCR unit 14 comprises vanadium compounds. The catalyst composition is selected from the group consisting of the oxides of vanadium, niobium, molybdenum, iron and copper. The SCR unit 14 is used to reduce the nitrogen content in the exhaust gas before flowing out into the atmosphere. The working of the SCR unit 14 is a known concept.

[0010] The SCR unit 14 is a cylindrical structure with vanadium coating. For instance, on an inert ceramic honeycomb structure, the vanadium coating is applied up along the length of the inert support by a conventional dipping process as known to a person skilled in the art. However, the SCR unit 14 is not restricted to vanadium, but can be any type of SCR unit 14 comprising an Iron zeolite , a copper zeolite and the like or a combination of the vanadium with any one of the above types and the like. The SCR unit 14 is designed to operate in a predefined temperature range. For instance, the SCR unit 14 is operated in the temperature range from 250 degrees- 500 degrees.
[0011] A device 10 to regulate temperature of an exhaust gas in accordance to one embodiment of the invention. The device10 comprises a cover 22 enclosing the exhaust path 13 located between the DOC 12 and the SCR unit 14. The cover 22 forms a chamber and comprises an inlet 24 and an outlet 26 for facilitating a flow of a coolant from the electronically controlled coolant unit 20 over the exhaust path 13 to regulate the temperature of the exhaust gas in the vehicle 11. The device comprises a uni-directional valve 28, which is in fluid communication with the cover 22. The control unit 18 controls the operation of the uni-directional valve 28. The cover 22 is chosen from a group of covers comprising a tube, a pipe and a hose and the like. However, the cover 22 is not restricted to the above-disclosed covers, but can also be a sheet metal, and the like as known to a person skilled in the art. The cover 22 is made of a heat resisting material or the cover 22 comprises a coating of the heat resisting materials comprising boron, silicon and the like. An inter cooler is connected between the outlet 26 of the cover 22 and the coolant unit 20. The control unit 18 opens the valve 28 for allowing the coolant to flow over the exhaust path 13 located between the DOC 12 and the SCR unit 14 via the cover 22, when the detected temperature is more than a predefine temperature value. The predefined temperature is a temperature range calibrated, when the vehicle is operating in at least one-vehicle conditions comprising a low-load condition and a high-load condition.

[0012] According to one embodiment of the invention, the coolant unit 20, which is electronically controlled, comprises a tank (not shown) to store and a pump to supply the coolant respectively to the engine for reducing the temperature of the engine 22 as known in the state of the art. The coolant is chosen from a group of coolants comprising a water, a mineral oil, liquid nitrogen and the like.
[0013] Fig.2 illustrates a device to regulate a temperature of an exhaust gas in a vehicle in accordance with one embodiment of the invention. According to one embodiment of the invention, the coolant unit 20 is a path circulating the atmospheric air from intake manifold 34 to the engine to reduce the temperature of the engine. The coolant in this embodiment is the atmospheric air taken from the engine air intake path and is driven over the exhaust path 13 located between the DOC 12 and the SCR unit 14 via the inlet 24 of the cover 22.
[0014] Fig.3 illustrates a device to regulate a temperature of an exhaust gas in a vehicle in accordance with one embodiment of the invention. According to another embodiment of the invention, the cover 22 is a heat-dissipating element 30 comprising multiple fins 32 enclosing the exhaust path 13 located between the DOC 12 and the SCR unit 14. The dimensions (length and diameter) of the heat-dissipating element 30 and number of the fins 32 made on the heat-dissipating element 30 is based on a quantity of heat to be regulated of the exhaust gas. More the temperature of the exhaust gas is to be reduced, more number of fins 32 is used. For instance, the heating dissipating element 30 design ensures the temperature of the exhaust gas upstream the SCR unit 14 maintained below 500degrees.
[0015] A method of regulating the temperature of the exhaust gas in the system 11 of the vehicle is explained as follows. The exhaust gas from the engine 22 flows into the DOC 12 where the sulphur and the carbon content is reduced. Before entering the SCR unit 14, which is located, downstream of the DOC 12, the exhaust gas temperature has to be reduced, as the high temperatures of the exhaust gas will damage the SCR unit 14. The

temperature sensor 16 present in the exhaust path 13, detects the temperature of the exhaust gas entering the SCR unit 14. The control unit 18 receives the detected temperature. According to one embodiment of the invention, the control unit 18 is an engine control unit. The control unit 18 upon detecting the temperature more than the predefined temperature value which is stored in the control unit 18, opens the uni-directional valve 28 and provides a signal to the coolant unit 20 to transmit the coolant over the exhaust path 13 via the inlet 24 of the cover 22.
[0016] For instance, the coolant unit 20 pumps the coolant (water) through the uni-directional valve 28 onto the exhaust path 13 located between the DOC 12 and the SCR unit 14 via the inlet 24 of the cover 22. The heat of the exhaust gas is absorbed by the coolant (water) and is flown back to the coolant unit 20 via the outlet 26 of the cover 22. The inter cooler 36 present in between the outlet 26 of the cover 22 and the coolant unit 20 , reduces the heat of the coolant coming out of the cover 22 before entering the coolant unit 20.
[0017]In another instance, the control unit 14 directs the atmospheric air via the unidirectional valve 28 and the inlet 24 of the cover 22 onto the exhaust path 13 located between the DOC 12 and the SCR unit 14, upon detecting the temperature of the exhaust gas more than the predefined temperature valve. The atmospheric air reduces the heat of the exhaust gas and reaches the intake manifold 34 via the outlet 26 of the cover 22. The inter cooler 36 as mentioned above, reduces the heat of the atmospheric air coming out of the outlet 26 of the cover 22.
[0018] Yet in another instance, the heat-dissipating element 30 is inserted over the exhaust path 13 located between the DOC 12 and the SCR unit 14. The fins 32 of the heat-dissipating element 30 helps in dissipating the heat of the exhaust gas and thus reducing the temperature of the exhaust gas before reaching the SCR unit 14. The design parameters of the heat-dissipating element 30 like length, diameter and number of fins/corrugations depends on the quantity of the temperature to be reduced. For

example, when the vehicle is operating at 580 degrees and 10% over load at an altitude of 2000 m needs a temperature drop of 80 degrees to make sure the efficient working of the SCR unit 14 works at all operating conditions. For such application, a 1m pipe with 25 fins/corrugations with an area of 4 cm would be sufficient to ensure temperature drop of 80 degrees, at above-mentioned operating condition.
[0019]However, when the vehicle is operating at a low load conditions, the temperature drop is counterproductive for the performance of the SCR unit 14. To meet the emission targets at low load operating conditions, an additional copper zeolite SCR unit is placed in front of the existing vanadium SCR. The volume of copper SCR unit is kept minimum to make sure there is least impact on overall system cost. This additional copper SCR unit is used depending on the operating conditions. If the temperature upstream the SCR unit 14 is maintained above 250 0C then, copper SCR unit is eliminated the Vanadium SCR unit is used in the vehicle 11.
[0020]With the above device 10 and the method, the conversion process of the exhaust gas into the non-harmful gases will be efficient. The device 10 provides a simple, cost-effective solution as the use of expensive zeolite-based SCR catalyst is reduced. The emission compliance is efficiently achieved for low temperature and for high temperature operating conditions by the above-disclosed device10. The usage of the existing components (engine coolant and the intake air) to reduce the temperature of the exhaust gas results in efficient usage of the recirculated products.
[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.

We Claim:
1. A system (11) to regulate temperature of an exhaust gas in a vehicle (11),
said system (11) comprising:
- a diesel oxidization catalyst (DOC) (12) and a SCR unit (14) positioned in an exhaust path (13);
- a temperature sensor (16) positioned upstream said DOC (12) to detect temperature of an exhaust gas flowing in said exhaust path (13);
- a control unit (18) connected to said temperature sensor (16);
- an electronically controlled coolant unit (20) connected to said control unit (18);
characterized in that: a device (10) comprising:
- a cover (22) enclosing said exhaust path (13) located between said DOC (12) and said SCR unit (14),
said cover (22) forms a chamber and comprises an inlet (24) and an outlet (26) for facilitating a flow of a coolant from said electronically controlled coolant unit (20) over said exhaust path(13) to regulate said temperature of said exhaust gas in said vehicle (11).
2. The system (11) as claimed in claim 1, wherein said device (10) comprises a uni-directional valve (28) in fluid communication with said inlet (24) of said cover (22), said uni-directional valve (28) is electronically controlled.
3. The system (11) as claimed in claim 2, wherein said control unit (18) adapted to operate said uni-directional valve (28) to allow passage of said coolant, when a detected temperature is more than a predefined temperature value.

4. The system (11) as claimed in claim 1, wherein said cover (22) is chosen from a group of covers comprising a tube, a pipe, a hose and a sheet metal.
5. The system (11) as claimed in claim 1, wherein said coolant is an engine coolant/water.
6. The system (11) as claimed in claim 1, wherein said coolant is an atmospheric air.
7. The system (11) as claimed in claim 1, wherein said cover (22) is a heat dissipating element (30) comprising multiple fins (32) enclosing said exhaust path (13) located between said DOC (12) and said SCR unit (14).
8. The system (11) as claimed in claim 7, wherein dimensions of and number of said fins (32) made on said heat dissipating element (30) is based on a quantity of heat to be regulated of said exhaust gas.
9. The system (11) as claimed in claim 1, wherein said SCR unit (14) comprises a vanadium compound and a catalyst, arranged in the form of a coating on an inert support.
10. A device (10) to regulate temperature of an exhaust gas, said device(10) comprising:
- a cover (22) enclosing said exhaust path (13) located between said DOC (12) and said SCR unit (14),
said cover (22) forms a chamber and comprises an inlet (24) and an outlet (26) for facilitating a flow of a coolant from said electronically controlled coolant unit (20) over said exhaust path(13) to regulate said temperature of said exhaust gas in said vehicle (11).