FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2006
COMPLETE
Specification
(See Section 10 and Rule 13}
AN EXHAUST GAS RECIRCULATION ASSEMBLY FOR MIXING EXHAUST GASES WITH COMBUSTION AIR
MAHINDRA & MAHINDRA LTD.
an Indian Company
of R & D Center, Automotive Division,
89, M.I.D.C, Satpur, Nashik - 422 007,
Maharashtra, India
Inventors:a) PATADE VISHNU, and b) VELUSAMY RAMASAMY
The following specification particularly describes the invention and the manner in which it
is to be performed.

FIELD OF INVENTION
The present invention relates to the field of systems for recirculation of exhaust gases in an internal combustion engine.
Particularly, the present invention relates to an exhaust gas recirculation assembly for mixing the recirculated exhaust gases with combustion air.
DEFINITIONS OF TERMS USED IN THE SPECIFICATION
The term "venturi" used in the specification means a device which illustrates the venturi effect causing a drop in fluid pressure due to increase in fluid velocity when the fluid flows through a constricted region.
BACKGROUND
Ever-stricter emission standards for diesel and other internal combustion engines are implemented by countries worldwide to reduce emissions of oxides of nitrogen (NOx), hydrocarbon (HC) and particulate matter. Exhaust gas recirculation (EGR) is a known technique, by which a part of exhaust gases from a combustion process in the combustion engine, are lead back to an inlet duct, with a part of inlet (fresh) air, for supply of the mixture of air and exhaust gases to the combustion engine cylinders, where the combustion takes place. The recirculation of a part of exhaust gases with air to the engine cylinders reduces the concentration of oxygen therein, which in turn lowers the maximum combustion temperature in the cylinders and slows the chemical reactions of the combustion process, resulting in a decrease in the content of nitrogen oxides (NOx) in the exhaust gases produced thereof.

Furthermore, the exhaust gases contain unburned hydrocarbons, which due to re introduction into the combustion chamber, get burned, thus reducing the emission of undesirable pollutants from the internal combustion engine.
In boosted combustion engines, the air supplied to the combustion chamber is at a pressure higher than the pressure of the exhaust gases at some engine operating conditions. One widespread method for mixing exhaust gases with air is by using a venturi. The venturi induces a flow of the exhaust gases into the flow path of air passing there through, wherein the venturi is configured to mix low pressure exhaust gases with high pressure air. Typically, in the venturi, the pressurized air enters initially, through a first inlet of a first section having a decreased cross-section, which causes the air velocity to increase and the static pressure to decrease. At the mid-section of the venturi, with minimum cross-section, the pressure of the air falls to a level below the pressure of the exhaust gases, typically, a second inlet is provided in this section, from where the exhaust gases are sucked in to the venturi. The exhaust gases entering the venturi therefore get mixed with the air flow in the mid-section. The resulting mixture of exhaust gases and air is carried there through to a third section which has an increased cross-section and serves as a diffusor. In the third section, the pressure of the air and exhaust gases mixture increases and the velocity decreases, due to the increase in the venturi cross-section; the mixture, having gained pressure, is then guided to respective cylinders of the combustion engine.

The amount of exhaust gases to be recirculated to the engine and pressure of the combustion air fed to the engine varies depending on the engine speed and the load condition. To provide a varying exhaust gas recirculation rate and manipulate the pressure conditions, the venturi device can be designed with variable dimensions, having a narrow mid-section, that is sufficiently small to be capable of sucking the required amount of exhaust gases, at all load conditions. However, this is physically difficult and complex to design and manufacture. Further, an elastically deformable wall can be provided in the narrow mid-section of the venturi device, to vary the dimension of the mid section depending up on the external forces exerted by the combustion air, however, construction of such an implement is complicated and costly, with an added disadvantage of a shorter life span of the elastic material due to the temperature and alternating pressure conditions therein. Still further, a valve can be provided which is controllably actuated using an electronic controller, which senses the various operation parameters associated with the engine. The valve, typically, controls the flow rate of the combustion air to the venturi mid-section, which in turn affects the flow velocity and creates vacuum pressure therein. By varying the vacuum pressure, the amount of exhaust gases induced in the venturi can be varied. However, inducing the exhaust gases into the flow of combustion air in such manner may affect the diffusion and pressure recovery of the mixture in the divergent section.
Also, the flow of the mixture through the expanded channel leads to a relatively thick boundary layer along the wall of the channel. The boundary layer of a flowing medium is the layer which exhibits a velocity of at most 80

% of the actual flow velocity in the central portion. A thick boundary layer involves risk of the flow of the medium becoming unstable, and therefore resulting in the divergent section losing its pressure-raising function. This problem can be solved by providing a long straight section after the venturi, to help obtain a uniform and stable flow of the combustion air and exhaust gases mixture before entering the engine. However, such EGR systems are space-consuming; since the available engine space is limited, there is a need to provide alternate solutions to solve the afore-mentioned problem.
Several attempts have been made to alleviate some of the above-listed problems related to the systems adapted for mixing recirculated exhaust gases with combustion air, some of these disclosures are listed in the prior art
below:
US7552722 discloses a device to provide improved EGR mixing pipes, for facilitating better mixing of the air and exhaust gases prior to entry into the intake manifold of an internal combustion engine. The mixing pipe comprises an air inlet port and an outlet port disposed at Opposite ends of the mixing pipe, and an exhaust inlet port disposed at a region of the mixing pipe between the air inlet port and outlet port, configured to deliver exhaust gases to be mixed with air inside the mixing pipe. A diffuser nozzle is disposed internally within a region of the mixing pipe, between the exhaust inlet port and the air outlet port, to define an outer mixing channel in the space between the diffuser nozzle and the mixing pipe region.

US6502397 discloses a device for transferring exhaust gases from the exhaust collector of an internal combustion engine to the inlet conduit which comprises a venturi device, the exhaust gases being sucked in the inlet conduit from the exhaust collector, in order to overcome the high gas pressure in the pressurized charging air in the conduit. An injector tube is provided in the inlet section to the canal of the venturi device, through which, variable amounts of EGR gases, depending upon the engine load conditions, are led into the venturi device. The free end of the injector tube along with the surrounding canal wall, delimits a ring-shaped passage for the charging air, wherein the injector tube and the venturi device are axially movable relative to each other.
US6267106 discloses an exhaust gas recirculation system in an internal combustion engine comprising an induction venturi which includes a combustion air inlet connected and in communication with the combustion air supply, an exhaust gas inlet connected and in communication with the exhaust manifold, and an outlet. A venturi section terminates at a venturi throat and is in communication with the combustion air inlet; wherein an expansion section is positioned between and in communication with the venturi section and the outlet, and induction ports which terminate adjacent to the venturi throat and within the expansion section.
US20040006978 discloses a system and a method for controlling an exhaust gas recirculation (EGR) system comprising a venturi. The system includes means to measure the temperature of the exhaust gases entering the venturi,

the temperature of the supply air entering the venturi, and the temperature of air/exhaust gases mixture before entering the engine. The method comprises calculating, based on the measuring step, a parameter indicative of the mass fraction of exhaust gases in the mixture, and adjusting an engines operating parameter accordingly. The system as disclosed in US20040006978 can reduce the NOx, CO, HC, and particulate matter emissions in a diesel engine.
WO2009093993 discloses a device for mixing recirculated exhaust gas into an engine air intake of an internal combustion engine. The device comprises a mixing chamber disposed or formed in an air intake conduit, the chamber further comprising an inlet for receiving intake air, an outlet for exhausting the intake air, and a port there between with a mixer tube shaped as a cylindrical-section with an elongated opening, extending through the port in the mixing chamber; wherein the mixer tube extends into the mixing chamber so as to leave an aperture not more than 20% of the width of the mixing chamber, to allow for the pressure-drop in the intake air and therefore result in drawing of exhaust gases in the mixing chamber through the mixer tube.
WO03046361 discloses an apparatus for exhaust gas recirculation in a combustion engine comprising an inlet duct for supplying a composite medium comprising a mixture of air and exhaust gases to the combustion engine, wherein the inlet duct incorporates a venturi to allow the addition of exhaust gases to the pressurized air in the inlet duct. The apparatus further incorporates flow guide means in the inlet duct to counteract growth of the

boundary layer of the flowing medium in the expanding third portion of the venturi.
The present invention discloses one such exhaust gas recirculation assembly comprising a venturi for mixing the exhaust gases with combustion air, which aims at overcoming the aforesaid limitations of the conventional EGR systems having a venturi device. The present invention is directed at providing a simple and easy to design and manufacture assembly that allows uniform and stable mixing of a controllable amount of exhaust gases with combustion air in an internal combustion engine under varying load conditions.
OBJECT OF THE INVENTION
An object of the present invention is to provide an assembly for recirculation of exhaust gases m an internal combustion engine.
Another object of the present invention is to provide an exhaust gas recirculation assembly for uniformly mixing the recirculated exhaust gases with combustion air.
Still another object of the present invention is to provide an assembly for mixing the recirculated exhaust gases with combustion air which can be effectively used under varying load conditions.

Yet another object of the present invention is to provide an assembly for mixing the recirculated exhaust gases with combustion air which efficiently controls the exhaust gas recirculation rate, and the combustion air velocity and pressure.
One more object of the present invention is to provide an assembly for mixing the recirculated exhaust gases with combustion air which is compact and has a long life span.
Still one more object of the present invention is to provide an assembly for mixing the recirculated exhaust gases with combustion air which is physically simple and easy to design and manufacture.
Yet one more object of the present invention is to provide an assembly for mixing the recirculated exhaust gases with combustion air which does not comprise any additional components within the venturi device.
SUMMARY OF THE INVENTION
In accordance with the present invention is provided an assembly for mixing recirculated exhaust gases with combustion air, said assembly comprising:
■ a venturi adapted to introduce a flow of exhaust gases into a flow of pressurized combustion air; a pressurized combustion air supply connected to and in communication with said venturi, an

exhaust gas manifold connected to and in communication with said venturi, adapted to supply exhaust gases thereto; ■ said venturi comprising:
• a converging first section defining a narrowing combustion air inlet, axially connected to and in communication with the combustion air supply, adapted to receive pressurized combustion air;
• a cover plate, in communication with said converging first section and connected to and in communication with said exhaust gas manifold, said cover plate having a larger cross-section than said first section, the narrower end of said combustion air inlet opening in said cover plate; said cover plate comprising an exhaust gas inlet substantially orthogonally to the narrower end of said combustion air inlet to permit flow of said pressurized combustion air through said first section, thereby creating a pressure drop at said exhaust gas inlet adapted to draw exhaust gases from said manifold into said cover plate, said cover plate being adapted to uniformly mix the exhaust gases with the combustion air due to a swirling motion initiated in the combustion air on entering said cover plate;
• a diverging third section in communication with said cover plate, adapted to receive the mixture of exhaust gases and combustion air from said cover plate and

further adapted to, reduce the velocity of the mixture and

thereby recover at least partially the pressure drop in the
pressurized combustion air; and ■ a non-circular bent section in communication with said diverging third section, said bent section being adapted to cause a pressure drop in the mixture of exhaust gases and combustion air, thereby preventing eddy formation and providing a mixture of exhaust gases and combustion air to be fed to an intake manifold of an internal combustion engine.
Preferably, in accordance with the present invention, the angle of divergence in said diverging third section is in the range of 5 - 12 °, preferably 7 °.
Typically, in accordance with the present invention, said bent section is linearly connected to and in communication with an intake manifold, being adapted to receive the pressurized mixture of exhaust gases and combustion air thereto.
In accordance with the present invention, said assembly is mounted on the intake manifold of an engine by means of bolts.
Typically, in accordance with the present invention, the ratio of the diameters of said converging first section and said diverging third section is in the range of 1.33 : 1 to 2.5: 1.

Preferably, in accordance with the present invention, the ratio of the lengths of said converging first section and said diverging third section is in the range of 1 : 0.92 to 1 :2.6.
Typically, in accordance with the present invention, the cross-section of said

cover plate is in the range of 20 cm2 to 110 cm2 and width of the cover plate is in the range of 0.6 cm to 3.5 cm in the direction of flow.
Preferably, in accordance with the present invention, said venturi and said bent section are formed as a continuous body.
In accordance with the present invention, is provided a method for mixing recirculated exhaust gases with combustion air, said method comprising the following steps:
■ supplying pressurized combustion air from a combustion air supply through a narrowing combustion air inlet to a converging first section of a venturi;
■ effecting a pressure drop in the combustion air with increase in flow velocity due to the convergence in said first section of said venturi;
■ accepting the combustion air in a cover plate of said venturi having an enlarged cross-section compared to said first section, where the narrower end of the combustion air inlet opens, exhaust gases entering orthogonally to the flow of combustion air;

■ creating a vortex motion in the combustion air on entering said cover plate of said venturi, pressure drop in the combustion air resulting in drawing of exhaust gases therein, to result in uniform mixing of the exhaust gases with the combustion air;
■ decreasing the flow velocity and thereby increasing the pressure of the mixture of exhaust gases and combustion air by passing through a diverging third section of said venturi;
■ passing the mixture of exhaust gases and combustion air through a non-circular bent section provided in communication with the diverging third section of said venturi for causing a pressure drop in the mixture and to prevent eddy formation; and
■ receiving the pressurized mixture of exhaust gases and combustion air in an intake manifold.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with the help of the accompanying drawings, in which,
Figure 1 illustrates a schematic of the exhaust gas recirculation assembly for mixing recirculated exhaust gases with combustion air, in accordance with the present invention;
Figure 2 illustrates a pictorial view of the cover plate in the exhaust gas recirculation assembly for mixing recirculated exhaust gases with combustion air, in accordance with the present invention; and

Figure 3 illustrates a pictorial view of the exhaust gas recirculation assembly for mixing recirculated exhaust gases with combustion air, in accordance with the present invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the invention. The description provided is purely by way of example and illustration.
The present invention envisages an exhaust gas recirculation assembly for an internal combustion engine, adapted to provide uniform mixing of a controllable amount of recirculated exhaust gases, under varying load conditions, with combustion air, by using a venturi device which does not comprise any additional components therein, is simple in design, and easy to manufacture, and further comprises means to control the velocity of the resulting exhaust gases/combustion air mixture and thereby provide high pressure composite mixture to be fed to an intake manifold which supplies the mixture to the engine's cylinders for combustion purpose. The engine may for example be intended to power vehicles such as cars, trucks, pick-ups, and the like.
FIGURE 1 illustrates a schematic of the assembly of present invention, showing a venturi, generally represented in FIGURE 1 by numeral 100, adapted to introduce a flow of exhaust gases into a flow path of pressurized

combustion air, and further adapted to mix exhaust gases with the pressurized combustion air therein. Pressurized combustion air, having pressure in the range of 1 bar (A) -3.7 bar (A), is received in the venturi 100 at a converging first section, represented by numeral 106, from a pressurized combustion air supply (not shown in the FIGURE) connected to and in communication with the venturi 100, through a narrowing combustion air inlet 102, the path of combustion air is shown by numeral 104. Due to the convergence, i.e. reduction in the cross-section, the velocity of the combustion air increases which results in a sudden pressure drop. The converging first section 106 defines the narrowing combustion air inlet 102, axially connected to and in communication with the pressurized combustion air supply (not shown in the FIGURE), defining a narrowing path having a continuously decreasing cross-section that opens in a cover plate 108 of the venturi 100, and is adapted to receive the pressurized combustion air. The cover plate 108 of the venturi 100 is connected to and in communication with the converging first section 106 and a diverging third section 112 with the help of bolts and a gasketed joint (not shown in FIGURE).
The velocity of the combustion air in the converging first section 106 progressively increases in the direction of the flow while at the same time the static pressure decreases. FIGURE 2 illustrates a pictorial view of the cover plate 108 in the exhaust gas recirculation assembly of present invention. In the cover plate 108, the narrower end of the combustion air inlet 102 of the converging first section 106 opens, to permit flow of the de-pressurized combustion air to the cover plate 108, wherein the cover plate 108 comprises

an exhaust gas inlet, represented by numeral 110, substantially orthogonal to the narrower end of the combustion air inlet 102, thereby creating a pressure-drop at the exhaust gas inlet 110. Exhaust gases from an exhaust gas manifold (not shown in the FIGURE), connected to and in communication with the cover plate 108 of the venturi 100, are received via an exhaust gas supply line (not shown in FIGURE 1 & 2), in the venturi 100 through the exhaust gas inlet 110, perpendicular to the flow path 104 of the de-pressurized combustion air, refer FIGURE 2. The exhaust gases, typically have a pressure in the range of 1 bar (A) - 4.2 bar (A). These exhaust gases get sucked in the venturi device 100 through the exhaust gas inlet 110 from the exhaust manifold (not shown in FIGURE), in the cover plate 108, essentially perpendicularly to the flow path 104 of the combustion air entering the cover plate 108 through the combustion air inlet 102.
The amount of exhaust gases drawn in the cover plate 108 of the venturi 100 through the exhaust gas inlet 110 can be varied from 0 % to 76 % of the total gases entering the engine's cylinders, depending upon the engine load conditions and other parameters. The pressure of the combustion air may be manipulated to control the amount of EGR entering through the exhaust gas inlet 110. Further, a throttle valve (not shown in the FIGURE) which is a butterfly valve is provided in the combustion air supply (not shown in the FIGURE) to control the quantity of combustion air entering through the combustion air inlet 102. The throttle valve (not show in the FIGURE) is monitored by the sensors provided in the electronic control unit (ECU), where the signal generated there from controls the combustion air quantity entering

through the combustion air inlet 102 in the venturi 100, thereby indirectly manipulating the quantity of EGR through the exhaust gas inlet 110.
The cover plate 108 has a larger cross-section (diameter) and a smaller length compared to the respective cross-section and length of the converging first section 106, refer FIGURE 2, which causes the de-pressurized high velocity combustion air to be set in a swirling motion on entering the cover plate 108. While, due to the low pressure of air, exhaust gases are easily drawn into the combustion air flow in the cover plate 108 of the venturi 100, resulting in uniform mixing to provide a composite comprising a mixture of exhaust gases and combustion air. The resultant composite thereafter flows through the diverging third section 112 of the venturi 100, which is provided in communication with the cover plate 108, having a continuously increasing cross-section, resulting in a progressive decrease in the composite velocity and thereby raising the static pressure at least partially. The composite is, therefore, again pressurized in the diverging third section 112. The pressurized composite is led from the venturi 100 via the diverging third section 112; flow path of the composite is represented by numeral 114. The angle of divergence in the diverging third section 112 is in the range of 5 -12°, preferably 7 °, which is below the boundary layer condition set for fluids for boundary layer separation, thus, no boundary layer separation occurs in the diverging third section 112 of the venturi 100, therefore providing a stable flow of the composite medium and maintaining the pressure-raising characteristic of the diverging third section 112 of the venturi 100. The ratio of the diameters of the converging first section 106 and the diverging third

section 112 is typically in the range of 1.33 : 1 to 2.5 : 1. The cross-section (diameter) of the cover plate 108 is in the range of 20 cm2 - 110 cm2 and the width of the cover plate 108 is in the range of 0.6 cm to 3.5 cm in the direction of flow to accommodate the volume.
FIGURE 3 illustrates a pictorial view of the exhaust gas recirculation assembly of present invention being mounted on an intake manifold, represented in FIGURE 3 by numeral 200. The assembly of present invention 200 is linearly mounted on the intake manifold, represented by numeral 122. of an engine, with the help of four bolts at the ^gas entry; the^as entry is shown in FIGURE 3 by numeral 120, where an additional two bolts are provided for structural stability. The exhaust gases entering the cover plate 108 of the venturi 100 through the exhaust gas inlet 110 via the exhaust gas supply line 116, wherein the exhaust gases are led into the exhaust gas supply line 116 from the exhaust gas manifold (hot shown in the FIGURE), may be purified and cooled before being fed to the venturi 100 for combining with combustion air. The pressurized composite having a controlled velocity, after passing through the diverging third section 112 of the venturi 100, enters a bent section 118 provided in continuity with the diverging third section 112 of the venturi 100, where the bent section 118 is typically formed as a continuous body with the venturi 100. The bent section 118 is provided in communication with the diverging third section 112 to receive the pressurized composite, wherein the bent section 118 has the cross-section as the broadest end of the diverging third section 112. Further, the bent section 118 is linearly connected to and in communication with the intake manifold 122 at the gas

entry point illustrated by numeral 120 in FIGURE 3. The non-circular bent section 118 occupies a smaller space and is adapted to cause a pressure drop in the mixture of exhaust gases and combustion air, thereby preventing eddy formation and providing a mixture of exhaust gases and combustion air to be fed to an intake manifold of an internal combustion engine. Further, a uniformity index in the range of 0.83 to 0.97 is achieved at maximum combustion air flow requirement, typically 500 - 550 kg/hr of air.
This pressurized composite medium from the bent section 118 is led to the intake manifold 122 through the gas entry opening 120, where in the intake manifold 122 the composite medium is collected and there from the uniform mixture of exhaust gases and combustion air is distributed to the engine's cylinder via apertures represented by numeral 124 in the FIGURE 3. Adding the exhaust gases to the combustion air lowers the combustion temperature in the engine's cylinders and therefore decreases the content of NOx which are formed during the combustion process. Further, due to recirculation, the previously unburnt particles get combusted, which reduces the content of HC and particulate matter in the exhaust gases. The ratio of the lengths of the converging first section 106 and the diverging third section 112 of the venturi 100 is in the range 1 : 0.92 to 1 : 2.6, and the cross-section of the cover plate 108 is in the range of 20 cm2 - 110 cm2 and width of the cover plate 108 is in the range of 0.6 cm to 3.5 cm in the direction of flow to accommodate the volume, in the assembly of present invention.

The assembly of present invention, as illustrated in FIGURE 3 by numeral 200, is made from aluminum to impart the robustness, wherein the bent section 118, provides for a relatively compact design, while providing a uniform and stable flow of the composite medium there from after leaving the venturi 100, further with overcoming the limitations of the conventional exhaust gas recirculation systems.
TECHNICAL ADVANTAGES
An exhaust gas recirculation assembly for mixing exhaust gases with combustion air in an internal combustion engine, as described in the present invention has several technical advantages including but not limited to the realization of:
• an exhaust gas recirculation assembly for uniformly mixing the recirculated exhaust gases with combustion air;
• an assembly for mixing the recirculated exhaust gases with combustion air which can be effectively used under varying load conditions;
• an assembly for mixing the recirculated exhaust gases with combustion air which efficiently controls the exhaust gas recirculation rate, and the combustion air velocity and pressure;
• an assembly for mixing the recirculated exhaust gases with combustion air which is compact and has a long life span;
• an assembly for mixing the recirculated exhaust gases with combustion air which is physically simple and easy to design and manufacture; and

• an assembly for mixing the recirculated exhaust gases with combustion air which does not comprise any additional components within the venturi device.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the invention, unless there is a statement in the specification specific to the contrary. Wherever a range of values is specified a value up to 10% below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the invention.
In view of the wide variety of embodiments to which the principles of the present invention can be applied, it should be understood that the illustrated embodiments are exemplary only. While considerable emphasis has been placed herein on the particular features of this invention, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the invention. These and other modifications in the nature of the invention or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be inteipreted merely as illustrative of the invention and not as a limitation.

We Claim:
1. An assembly for mixing recirculated exhaust gases with combustion air, said assembly comprising:
■ a venturi adapted to introduce a flow of exhaust gases into a flow of pressurized combustion air; a pressurized combustion air supply connected to and in communication with said venturi, an exhaust gas manifold connected to and in communication with said venturi, adapted to supply exhaust gases thereto;
■ said venturi comprising:

• a converging first section defining a narrowing combustion air inlet, axially connected to and in communication with the combustion air supply, adapted to receive pressurized combustion air;
• a cover plate, in communication with said converging first section and connected to and in communication with said exhaust gas manifold, said cover plate having a larger cross-section than said first section, the narrower end of said combustion air inlet opening in said cover plate; said cover plate comprising an exhaust gas inlet substantially orthogonally to the narrower end of said combustion air inlet to permit flow of said pressurized combustion air through said first section, thereby creating a pressure drop at said exhaust gas inlet adapted

to draw exhaust gases from said manifold into said cover
plate, said cover plate being adapted to uniformly mix
the exhaust gases with the combustion air due to a
swirling motion initiated in the combustion air on
entering said cover plate;
• a diverging third section in communication with said
cover plate, adapted to receive the mixture of exhaust
gases and combustion air from said cover plate and
further adapted to, reduce the velocity of the mixture and
thereby recover at least partially the pressure drop in the
pressurized combustion air; and
■ a non-circular bent section in communication with said diverging
third section, said bent section being adapted to cause a pressure
drop in the mixture of exhaust gases and combustion air, thereby
preventing eddy formation and providing a mixture of exhaust
gases and combustion air to be fed to an intake manifold of an
internal combustion engine.
2. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein the angle of divergence in said diverging third section is in the range of 5 - 12 °, preferably 7 °.
3. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein said bent section is linearly connected to and in communication with an intake manifold, being

adapted to receive the pressurized mixture of exhaust gases and combustion air thereto.
4. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein said assemblyis mounted on the intake manifold of an engine by means of bolts.
5. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein the ratio of the diameters of said converging first section and said diverging third section is in the range of 1.33: lto 2.5: 1.
6. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein the ratio of the lengths of said converging first section and said diverging third section is in the range of 1 : 0.92 to 1:2.6.
7. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein the cross-section of said cover plate is in the range of 20 cm to 110 cm and width of the cover plate is in the range of 0.6 cm to 3.5 cm in the direction of flow.
8. The assembly for mixing recirculated exhaust gases with combustion air as claimed in claim 1, wherein said venturi and said bent section are formed as a continuous body.

9. A method for mixing recirculated exhaust gases with combustion air, said method comprising the following steps:
■ supplying pressurized combustion air from a combustion air supply through a narrowing combustion air inlet to a converging first section of a venturi;
■ effecting a pressure drop in the combustion air with increase in flow velocity due to the convergence in said first section of said venturi;
■ accepting the combustion air in a cover plate of said venturi having an enlarged cross-section compared to said first section, where the narrower end of the combustion air inlet opens, exhaust gases entering orthogonally to the flow of combustion air;
■ creating a vortex motion in the combustion air on entering said cover plate of said venturi, pressure drop in the combustion air resulting in drawing of exhaust gases therein, to result in uniform mixing of the exhaust gases with the combustion air;
■ decreasing the flow velocity and thereby increasing the pressure of the mixture of exhaust gases and combustion air by passing through a diverging third section of said venturi;
■ passing the mixture of exhaust gases and combustion air through a non-circular bent section provided in communication with the diverging third section of said venturi for causing a pressure drop in the mixture and to prevent eddy formation; and

■ receiving the mixture of exhaust gases and combustion air in an intake manifold of an internal combustion engine.