FORM - 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
PROVISIONAL SPECIFICATION
(SEE SECTION 10; RULE 13)
"RE-CIRCULATED EXHAUST GAS DIFFUSER"
MAHINDRA & MAHINDRA LIMITED
AN INDIAN COMPANY,
R&D CENTER, AUTOMOTIVE SECTOR,
89, M.I.D.C., SATPUR,
NASHIK - 422 007,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION DESCRIBES THE NATURE OF THE
INVENTION

FIELD OF INVENTION:
The present invention is related to mixing of re-circulated exhaust gas and fresh air. More particularly the present invention is related to the device that mixes exhaust gas effectively in desired manner with the fresh air so as to form homogenous mixture for subsequent applications.
BACKGROUND & PRIOR ART SEARCH:
Combustion of gasses in a diesel engine when done in excess of oxygen, it results in the generation of NOx. To negate the formation of NOx, neutral gasses are infused into the stream of fresh air circulation thus reducing the concentration of available oxygen and limiting the maximum temperature resulting in the reduction of NOx, These neutral gasses used for the purpose are the re-circulated exhaust gasses. Also these re-circulated exhaust gasses have un-burnt hydrocarbons which when reintroduced into combustion chamber helps in reduction of emission also. Therefore, the exhaust gasses are infused into the stream of fresh air coming from the intercooler. But it requires uniform mixing of exhaust gasses with the fresh air. The uniform mixing of gases with air is achieved by providing a novel diffuser device as disclosed in this invention.
There is good number of EGR mixers / diffuser available in public domain that meets with varying degrees of success. United Kingdom patent No. GB2364656 discloses an exhaust gas re-circulation mixer partially shielded conduit disposed in the inlet conduit and has a fluid diverting portion and fluid passing portion. The fluid diverting portion diverts intake air into the first fluid stream and the second fluid stream. Exhaust gas is passed through fluid passing portion and is mixed with the first fluid stream and second fluid stream generally at a point downstream of the shielded conduit. But this system does not ensure homogeneous mixing of two fluids; also it does not enable the formation of hot spots and results in high back pressure due to partial blockage of the intake pipe.

United States patent No. US6945237 describes intake manifold with EGR/air mixing. The manifold includes an air intake port, an intake chamber receiving intake air from the intake port, an outlet plenum communicated with the engine, an EGR inlet port, and first and second EGR valve chambers. A wall separates air intake chamber from central EGR outlet passage chamber and from one of the EGR inlet passages. The wall creating turbulence as the EGR from the central EGR outlet passage mixes with intake air from the intake chamber. Patent No. US6935321 talks about EGR / air intake manifold with dual orientations, however this design has two spate channels. In this prior art document, the entry of exhaust gas is not at the center of the pipe and also it does not provide unrestricted flow of the incoming fresh air.
International patent application No. WO2007/140148 provides an exhaust gas recirculation mixer for use with a long route (i.e. low pressure) EGR system adapted for use in turbocharged IC engine. The mixer comprises an outer wall and inner wall defining a cavity there between, a chamber defined within the inner wall an exhaust gat inlet on the outer wall and apertures of varying dimensions disposed within the inner wall so that exhaust gas enters the mixer in controlled flow through the exhaust gas inlet for mixing with ambient air. This document also does not talk about entry of exhaust gas at the center of the pipe and also it does not provide unrestricted flow of the incoming fresh air.
None of the prior art EGR diffuser / mixer ensures homogeneous mixing of exhaust gas with fresh air maintaining the pressure in the intake pipe. Also, none of the prior art concepts talks about the entry of exhaust gas about the axis of the intake pipe.
OBJECTIVES OF THE PRESENT INVENTION:
Main object of the present invention is to achieve homogeneous mixing of re¬circulated exhaust gas with fresh air stream for diesel engine.

Another object of the present invention is to avoid the formation of hot spots inside the intake pipe.
Another object of the present invention is to achieve homogeneous mixing of re-circulated exhaust gas with fresh with the help of specially designed EGR diffuser.
Still another object of the present invention is to provide a novel re-circulated exhaust gas diffuser that homogeneously mixes the gas with a stream of fresh air.
Still further object of the present invention is to provide a gas diffuser that provides unrestricted flow to incoming air maintaining the pressure inside the intake pipe.
Still another object of the present invention is overcome the drawbacks of the prior art exhaust gas and fresh air mixing systems.
These objectives are achieved by the present invention wherein a diffuser mixes re-circulated exhaust gas with a stream of fresh air homogeneously and supplies the mixed air and exhaust gas to an internal combustion engine.
BRIEF DESCRIPTION OF THE FIGURES:
Further objectives and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein,
Figure 1 shows layout of the overall system comprising intake pipe encompassing the diffuser device of the present invention.
Figure 2 shows the longitudinal cross sectional view of the diffuser inside the intake pipe at encircled portion (17) in figure 1 in accordance with the present invention.

Figure 3 shows the exploded view of the diffuser device in accordance with the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION:
Referring to figure 1, the fresh air after the air filter (01) enters into compressor (09) of the turbocharger; the compressed air then enters into the intercooler (02) through the air inlet hose (15). The compressed and cooler air would enter into the intake pipe (04) through the air inlet hose (03) from the intercooler. In the intake pipe, EGR is also introduced through the diffuser (05) which is initially cooled by the EGR cooler (12) and routed through the EGR long pipe (13). The flow of the EGR is regulated by the EGR valve (11). When the re-circulated exhaust gas enters the intake pipe (4) through EGR diffuser (5) at location (17) it needs to be homogeneously mixed with a flowing stream of fresh air.
Referring figure 2 and 3, homogeneous mixing of exhaust gas with fresh air is achieved by gas diffusing device (20) which is mounted in the intake pipe (4). Re-circulated exhaust gas diffusing device (20) comprises of a pair of curved side walls (21) wherein the side walls (21) are exactly opposite to each other. The radius of curvature of the side wall is 13.3 mm and the curved side walls occupy total 43.32% of the total surface area and the surface area can be in the range of 37% to 52%. The diffusing device has curved top (22) placed on the curved side walls (21). The radius of curvature of the curved top is around 10 mm and the included angle is around 80 deg between the two flat faces. The importance of this geometry is that these features allow seamless mixing of the exhaust gasses with the incoming fresh air through intercooler. The curved top (22) is formed over the curved side walls (21) with help of single sheet metal operation. The curved side walls and the curved top wall is made by a single sheet metal by bending followed by forming operation, thus resulting in higher productivity, better reliability and durability over the life of its operation. The curved top (22) is having notches (23) on its either slanting. These notched gets developed automatically as the result of forming

operation. The complete diffuser device is made in sheet metal. The diffuser is made of mild steel as this suffices to the requirement of the functionality of the diffuser. The diffuser device is fitted to the inlet pipe so that the heat from the diffuser device does not get transferred to the intake pipe made of plastic. This is achieved by the construction as shown in Fig-2. The heat source of the exhaust gas and the joint of metal pipe on the plastic manifold are at a distance. The diffuser is welded to the pipe at the location (24) and the pipe is in touch with the plastic intake pipe (17) at the location (25), hence because of this distance the temperature on the plastic intake pipe is much lesser. Also at the location mentioned (26) has free air which takes away the temperature and thus helps in keeping the metals diffuser pipe to plastic intake pipe at a much lesser temperature.
The diffuser is snap fitted using a quick fix clamp which rests over the location mentioned (27). The leakage is assured by using the -Oring (28). The clip type assembly is very easy to assemble and provides easy access during servicing issues.
The homogeneous mixture of fresh cooler air and the EGR then enters into the intake manifold (06) which is combusted in the engine combustion chamber (07). The combustion gasses are collected in the exhaust manifold (08) where it gets bifurcated into two different streams. One stream of the gas is used to drive the turbine (14) of the turbocharger while the other stream is given as EGR through the EGR short pipe (10). The exhaust gas after working on the turbine goes as exhaust gas to the exhaust pipe (16) for further exhaust gas treatment.
The entry of the exhaust gasses into the stream of inflowing fresh air is achieved by using the diffuser design which enable the diffusion of re¬circulated exhaust gasses to enter the tube almost at the centre of the pipe and then the diffuser side body arrangements allow those gasses to get mixed across with the stream of inflowing fresh air from the intercooler. The radial entry of the exhaust gasses hits the curved top face of the diffuser which along with the incoming fresh air gets mixed homogeneously.

The diffuser assists additionally in case when the intake pipe & the intake manifolds are in plastic as it drastically reduces the hot spot temperatures formed over the body of the intake pipe & manifold thus allowing using a lower temperature withstanding material for which the cost is also low. The profile at the diffuser location comprising of the curved side walls and the top curved walls restricts the contact of the exhaust gas directly on the plastic intake pipe. However the exhaust gasses once get mixed with fresh air has lesser temperature. The profile of the diffuser guides the exhaust gas and simultaneously allows the fresh air to exhaust gas mixing without the formation of hot spots.
The diffuser makes the entry of exhaust gas about the axis of the intake pipe to ensure better mixing and better efficiency and to avoid formation of hot spots. The induction of the exhaust gasses happens almost near the centre of the plastic intake pipe hence the mixing is most effective and even the profile does not restricts the incoming fresh air thus even the pressure drop is also negligible. The diffuser also provides unrestricted flow to incoming air thereby maintaining the pressure inside the intake pipe (i.e. negligible pressure drop).
The diameter of the diffuser (5) is selected in such a way that, during engine operation exhaust gas flowing through will generate velocity of exhaust gas to the maximum order of Mach no 0.69.
It should be understood that the present invention is not to be limited by the exact details of the illustrated embodiment. However, it is to be taken as the preferred example of the invention and that various changes may be resorted to by a person skilled in the art without departing from the spirit of the invention. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.

ADVANTAGES OF THE PRESENT INVENTION:
• It is a cost effective solution of mixing exhaust gas with fresh air homogeneously.
• It can be made in plastic and metal sheet as well.
• It leads to overall reduction of the system weight.
• The diffuser is easy to manufacture.