A Muffler for regulating an Engine exhaust Field of invention

The present invention generally relates to a muffler and specifically the present invention relates to a muffler for regulating an engine exhaust such that it complies with BS4 emission norms.

Background of invention

Currently the muffler being made use of in all commercial vehicles has a conventional circular or elliptical cross section with a high length to diameter ratio. As things stand, there are a lot of constraints in terms of packaging. The idea behind this invention is to design the muffler in such a way so that it occupies minimum space but at the same time does not compromise the emission and noise performance.

Commercial vehicles are the major contributors for noise pollution by automobiles. The main contributor of noise in a commercial vehicle, per se, is the exhaust system. The control of noise from the exhaust system depends on the design of the muffler, the layout of the exhaust system, the piping and also the after treatment devices. However, the specific focus is towards the design of the muffler. Design of mufflers is a complex function that affects the noise characteristics and the fuel efficiency of the vehicle. So, a good design of the muffler should give the best noise reduction and offer optimum back pressure for the engine. Moreover, for a given internal configuration, mufflers have to work for a broad range of engine speed. Mufflers can have a number of elements inside which need to be chosen as per the level of attenuation required and recommended engine back pressure, this involves a lot of iterations of physical testing for each of the prototypes. Any muffler is qualified by the amount of insertion loss (IL) that takes place within the muffler. Insertion loss can be defined as the difference in sound pressure levels (SPL) at the exhaust outlet, with and without the muffler. Based on the required insertion loss, mufflers with different internal configurations can be designed and tested for muffled noise spectrum and vehicle noise.

The drawback of conventional muffler is that it consumes larger packaging space leading to a shorter tail pipe & sharp bends of the tail pipes in some vehicles. As the muffler has a higher length, it is very difficult to package the muffler in the already limited space available. Also, the existing conventional muffler requires more number of brackets as it is longer in length and requires additional length tail pipes to bring the tailpipe outlet to the side of the vehicle. Another problem with the conventional muffler is, because of the elongated tail pipe, there is an increased back pressure which hampers the proper running of the engine. This also means that there is lesser scope for noise attenuation as the muffler back pressure is forced to be lower.

In addition to these, there is a need for exhaust systems to meet stricter emission norms. In such cases when the migration from BSIII to BSIV is effected, there is a need to have additional after-treatment devices. The common ones used are SCR (selective catalytic reduction) and DOC/POC (oxidation catalysts in tandem with EGR-exhaust gas re-circulation). When these are brought in to effect, we need to have additional space to package these in separate enclosures. All this results in addition of more brackets, lesser space for packaging, higher costs and need for more maintenance. Also there is always the risk of pilferage of the after treatment device.

The need for a front exhaust arises when we go for a petroleum tanker application. A muffler with outlet on the side of the vehicle is very dangerous as the hot exhaust gases flow close to the tanker body. This could lead to severe consequences. This is the reason for the incorporation of a front-exhaust system.

It comprised of an additional spark arrestor, which helps filter the larger particles of un burnt fuel which would otherwise come out of the tail pipe. This was a precaution to prevent the production of any spark.

For vehicles which comply with higher emission norms, there is a need for after treatment devices. But for a front exhaust system where packaging is already a constraint, further addition of components is not manageable.

Also, the new safety standards for smaller vehicles on road calls for additional under-protection devices like FUPD (front under protection device), RUPD (rear under protection device) and SUPD (side under protection device). This calls for additional space requirements.

Therefore there is a need for an invention which overcomes the drawbacks and disadvantages described above.

Object of invention

Object of present invention is to provide a muffler for regulating an engine exhaust in a vehicle.

Summary of the invention

A muffler for regulating an engine exhaust in a vehicle is provided which comprises a jacket having a hollow region formed by an inlet end baffle having an inlet opening in it and an outlet end baffle having an having an outlet opening in it. The muffler comprises one or more baffles to have a first baffle and a second baffle attached inside the jacket in symmetry to the inlet opening and to the outlet opening to form one or more chambers inside the jacket to have a first chamber, a second chamber and a third chamber and the first baffle and the second baffle are capable of letting tubes pass through it and holding the tubes in place. The muffler comprises an inlet tube fixed to the inlet end baffle through the inlet opening and through the first baffle such that the other end of the inlet tube is exposed in the second chamber and the periphery of the inlet tube is exposed in the first chamber and in the second chamber. The muffler comprises one or more mid tube which is attached inside the jacket between the inlet end baffle and the second baffle through the first baffle such that the periphery of the mid tube is exposed in the first chamber and in the second chamber. The muffler comprises a DOC-POC assembly tube attached inside the jacket through the first baffle and through the second baffle such that one end of the DOC-POC assembly tube is exposed in the first chamber and the other end of the DOC-POC assembly tube is exposed in the third chamber and the periphery of the DOC-POC assembly tube is exposed in the first chamber, in the second chamber and in the third chamber. The muffler comprises an outlet tube one end of which is attached on the second baffle and the other end of it is projected out of the outlet end baffle through the outlet opening such that the periphery of the outlet tube is exposed in the third chamber and outside the outlet end baffle wherein the main stream of the exhaust from the engine reaches the second chamber of the jacket through the inlet tube and takes 180 degrees turn through the mid tube to reach the first chamber and thereupon the main stream of the exhaust takes 180 degrees turn again to reach the third chamber through the DOC-POC assembly tube and thereupon the exhaust gas exits the jacket through the outlet tube.

Brief description of drawings

Fig. 1 illustrates a muffler for regulating an engine exhaust in a vehicle in accordance with an exemplary embodiment of the present invention; and

Fig. 2 illustrates a cross section of the muffler for regulating an engine exhaust.

Detailed description of the drawings

Referring to fig. 1 a muffler for regulating an engine exhaust in a vehicle in accordance with an exemplary embodiment of the present invention is illustrated and referring to fig. 2 a cross section of the muffler is illustrated.

The muffler for regulating an engine exhaust in a vehicle the muffler comprises a jacket (1) having a hollow region (2) formed by an inlet end baffle (3a) having an inlet opening (4) in it and an outlet end baffle (3b) having an having an outlet opening (5) in it.

The muffler has one or more baffles to have a first baffle (6a) and a second baffle (6b) attached inside the jacket (1) in symmetry to the inlet opening (4) and to the outlet opening (5) to form one or more chambers inside the jacket (1) to have a first chamber (A), a second chamber (B) and a third chamber (C) and the first baffle (6a) and the second baffle (6b) are capable of letting tubes pass through it and holding the tubes in place.

The muffler has an inlet tube (7) fixed to the inlet end baffle (3a) through the inlet opening (4) and through the first baffle (6a) such that the other end of the inlet tube (7) is exposed in the second chamber (B) and the periphery of the inlet tube (7) is exposed in the first chamber (A) and in the second chamber (B).

The muffler has one or more mid tube (9) which is attached inside the jacket (1) between the inlet end baffle (3a) and the second baffle (6b) through the first baffle (6a) such that the periphery of the mid tube (9) is exposed in the first chamber (A) and in the second chamber (B).

The muffler has a DOC-POC assembly tube (10) attached inside the jacket (1) through the first baffle (6a) and through the second baffle (6b) such that one end of the DOC-POC assembly tube (10) is exposed in the first chamber (A) and the other end of the DOC-POC assembly tube (10) is exposed in the third chamber (C) and the periphery of the DOC-POC assembly tube (10) is exposed in the first chamber (A), in the second chamber (B) and in the third chamber (C).

The muffler has an outlet tube (11) one end of which is attached on the second baffle (6b) and the other end of it is projected out of the outlet end baffle (3b) through the outlet opening (5) such that the periphery of the outlet tube (11) is exposed in the third chamber (C) and outside the outlet end baffle (3b) wherein the main stream of the exhaust from the engine reaches the second chamber (B) of the jacket (1) through the inlet tube (7) and takes 180 degrees turn through the mid tube (9) to reach the first chamber (A) and thereupon the main stream of the exhaust takes 180 degrees turn again to reach the third chamber (C) through the DOC-POC assembly tube (10) and thereupon the exhaust gas exits the jacket (1) through the outlet tube (11).

In the muffler the inlet tube (7) has perforations (12) in its periphery in the region where it is exposed in the first chamber (A) through which a part of the exhaust gas entering the inlet tube (7) can enter the first chamber (A) and the remaining exhaust gas enters the second chamber (B) through an exponential connector (8) attached to the other end of the inlet tube (7).

In the muffler the mid tube (9) has perforations (13) in its periphery in the region where it is exposed in the first chamber (A) and also has perforations (14) in the region where it is exposed in the second chamber (B).

In the muffler the outlet tube (11) has perforations (15) in its periphery in the region where it is exposed in the third chamber (C).

In the muffler the first chamber (A), the second chamber (B) and the third chamber (C) are sealed with respect to tubes passing through it such that the flow of the exhaust gas from one chamber to the other is only through the tubes.

In the muffler the periphery of the first baffle (6a), the second baffle (6b), the inlet end baffle (3a) and the outlet end baffle (3b) are covered by glass wools (16) and perforated plates to regulate the exhaust noise of the engine.

In the muffler the periphery of the inlet tube (7) exposed in the region of the first chamber (A) is covered by glass wools (17) to regulate the noise of the engine.

In the muffler the perforations pattern of the inlet tube (7) is such it has perforation of 2.8mm diameter with pitch 11mm and has 36 perforations in each row with 16 rows.

In the muffler the perforations pattern of the mid tube (9) is such it has perforations of 7mm diameter with pitch 14 mm and has 12 perorations in each row with 10 rows and has perforations of 2.8mm diameter with pitch 10mm and has 30 perforations in each row with 18 rows in the region where it is exposed in the first chamber (A) and it has perforations of 2.8mm diameter with 6mm pitch and has 40 perforations in each row with 17 rows in the region where it is exposed in the second chamber (B).

In the muffler the perforations pattern in the outlet tube (11) is such it has perforations of 6mm diameter with 10mm pitch and has 16 perforations in each row with 18 rows in the region where it is exposed in the third chamber (C).

The shape of the jacket (1) of the muffler is rectangular and the tubes arranged inside the jacket (1) are such that the back pressure created by the muffler on the engine is less.

In the muffler the exhaust gas from the engine under goes phase reversal inside the jacket (1) twice before it exits the muffler to make the exhaust spark free and less noise.

In the muffler the perforation pattern present on the inlet tube (7), the mid tube (9) and the outlet tube (11) is based on the harmonics of the noise of the engine exhaust.

Fig. 2 also illustrates the plurality of the mid tubes (9a, 9b).

The present muffler described herein helps meet the BS4 emission norms. It also incorporates the noise reduction principles of reflection and absorption and thereby reduces the exhaust noise. The invention here combines the functionality of an emission device and also the noise reduction principles of reflection and absorption.

The design of the present rectangular muffler is in such a way that it takes care of all the required constraints. Some of the salient features of the rectangular muffler are:

■ By having a rectangular design, it consumes very less space for packaging and minimizes the number of brackets required. The total volume of the muffler is increased without creating packaging constraints for other aggregates.

■ The packaging is done in such a way that the piping required for the exhaust system is as low as possible. This results in lower back pressure which improves the engine performance.

■ The introduction of the advanced integrated muffler, wherein the after treatment device is housed within the muffler body, means that there is no need for packaging the after treatment device separately. This saves more space, bracket and also prevents pilferage of the expensive after treatment device.

■ The design of the rectangular muffler is done in such a manner, that the size of the particulate matter coming out is negligible. This negates the need for using an additional spark arrestor. The various features incorporated in the rectangular muffler to prevent the production of spark are:

> Muffler design is such that two 180-degree flow reversal elements have been incorporated. Providing such flow reversal elements forces the gases to flow in a longer path thereby reducing risk of spark.

> Muffler design is such that several sets of perforations have been provided which help in more complex 3-dimensional flow and better circulation / centrifugal action thereby minimizing the chances of spark. A total of 4 sets of perforations have been used at different locations.

> In addition to this, special purpose absorptive material has been added at critical positions in the flow path which will inhibit the passage of any spark through the flow chambers.

> In order to further reduce the propagation of spark, the muffler volume has been increased strategically. Conventionally muffler volume is 8~10 times of swept volume of the engine (In general). The special muffler is about 16-18 times the engine swept volume. This results in a longer flow path and more space for the gases to expand meaning lesser spark propagation.

> Care has been taken to use the same material for the muffler as that used in spark arrestors to give the muffler elements the same material properties. MS has been replaced with Aluminized steel.

> Special acoustic elements like exponential connector (8) and plug connectors have been added which, in addition to providing noise benefits, also help in increasing the flow path through flow reversal, thereby reducing the spark propagation.

> The outlet position has been strategically positioned co-axially and in the same plane which has helped further increase the length of the flow path helping in minimizing the spark propagation.

The present invention provides a rectangular muffler which has the following benefits.
a) Consistent performance
b) Reduced weight
c) Reduced cost
d) Decreased variety
e) Ease in vehicle assembly
f) Reduced component assembly time
g) Meeting BS4 emissions

BS4 emissions in diesel engines are achieved through two routes:
■ The EGR Route
■ The SCR Route

As far as diesel engines are concerned, the main pollutants in the exhaust gases are NOx (oxides of nitrogen) and PM (particulate matter). Due to the NOx-PM trade off characteristic of a diesel engine where each component increases or decreases inversely with respect to each other, it is possible to control only one of them at a time in the engine. We make use of the SCR route to control PM in the engine itself and then control NOx in an after treatment system. We make use of the EGR route to control NOx in the engine and then control PM in the after treatment system.

The present invention is a solution for BS4 through EGR Route and the emission device used in the present invention to achieve BS4 emissions is a DOC/POC assembly. The present invention consists of one coated DOC, a coated POC and an uncoated POC. These three devices work in tandem to achieve the desired emission performance.

The DOC converts the harmful NOx into N02 in order for the POC to convert it further. There is also effective reduction of CO and HC. There is usually a 30% reduction in PM.

The POC converts the N02 into N2 and 02. This oxygen is utilized to oxidize the particulate matter. The PM reduction achieved is up to 50%. The DOC and POC assembly give a combined PM reduction of up to 80%.

The present invention provides a muffler for automotive vehicles comprising a hollow jacket (1) having a first and second end; a first end cover with a hole mounted on the first end of the jacket (1); a second end cover with a hole mounted on the second end of the jacket (1); two perforated baffles with five holes and two holes respectively in such a manner that the jacket (1) is divided into three chambers by the two baffles, an inlet pipe extending from the first end of the jacket (1) up to the second chamber of the jacket (1) through the holes in the first end cover and the first perforated baffle containing perforations on its circumference in the region of the first chamber (A) and wrapped with glasswool. This is covered with a cylindrical sleeve. One end of the inlet pipe is connected to a flange on one end and a connector is mounted on the other end.

Two pipes with perforations on their circumference extending from the second chamber into the first chamber and fixed on the first end cover with perforations in the region of the first chamber. Two pipes fixed to the first end cover extend into the third chamber with perforations on the pipes in the regions within the first and second chamber; the perforations in the second chamber are wrapped with glass wool and covered with a cylindrical sleeve. An outlet pipe fixed to the second baffle (6b) extends through the second end cover and outside with perforations around the circumference in the region of the third chamber.

The muffler of the present invention comprises a hollow jacket (1) which is covered at both ends by end covers having a hole. The jacket (1) is divided into three chambers with the help of two plain baffles. An inlet pipe is inserted from the first end cover and extended up to the second chamber of the jacket (1) through the holes in the end cover and the first baffle (6a). One end of the inlet pipe is connected to a three point flange and the other end is fitted with a connector.

Two pipes inserted through the holes in the first baffle (6a) from the second chamber and extend up to the first chamber and fixed on to the first end cover. The other end of each of the two pipes is connected to a connector. Two more pipes are inserted through the holes in the first and second baffles and extend into the first chamber and fixed there to the first end cover. An outlet pipe is inserted from the second end cover through the hole in the second end cover and extends up to the second baffle in the third chamber of the jacket (1) and is fixed there. A portion of the inlet pipe which is placed in the first chamber comprises of one set of perforations of predetermined size to kill certain frequencies. Each row of perforation is staggered compared to adjacent row of perforation. In a preferred embodiment, the diameter of the perforation can be 2.8mm and the pitch i.e. distance between corresponding points of consecutive rows can be about 11mm The inlet pipe could have about 16 rows of perforation with 36 holes per row. The inlet pipe can extended into the second chamber for 40mm to 60mm, preferably 50mm. the connector which is fixed to the free end of the inlet pipe converges from about 103mm outer diameter on one end to about 73mm on the other with a width of about 19mm.

The first set of perforation wrapped by glass wool and enclosed inside a steel sleeve. The second and third sets of perforations are made on the second and third pipes. Preferably the diameter can be 2.8mm and the pitch can be about 6mm. The second and third sets could contain about 17 rows of perforations with about 40 perforations per row. The fourth and fifth, and the sixth and seventh set of perforations are made on the fourth and fifth pipes respectively. Preferably, the diameter could be 7mm for the fourth and sixth sets with a pitch of about 14mm and 2.8mm for the fifth and seventh set of perforations with a pitch of about 10mm. The fifth and seventh sets of perforations are wrapped by glass wool and enclosed inside a steel sleeve. The fourth and sixth sets could contain about 10 rows of perforations with about 12 perforations per row. The fifth and seventh sets could contain about 18 rows of perforations with about 30 perforations per row. The eighth set of perforation is made on the outlet pipe which is placed in the third chamber. Preferably, the diameter of the eighth set of perforation can be 6mm and the pitch can be about 10mm. The eighth set could contain about 18 rows of perforations with about 16 perforations per row.

In preferred embodiment, the three chambers of the jacket (1) could have specific dimensions of 203.5mm, 198mm and 223.5mm respectively. The shape of the jacket (1) could be close to a rectangle with the longer sides containing a radius profile at the corners. The length of the jacket (1) can preferably range from 620mm to 650mm. The jacket (1) is preferably constructed from a plane sheet with ends overlapped and welded across the whole length or crimped across the whole length of the jacket (1).

The muffler according to the present invention uses both the principles of reflective and absorptive principles.

The gases then flow through the inlet pipe which has perforations which are made based on calculations which help in canceling certain frequencies of noise which otherwise would contribute to a higher noise level. The sound waves are subject to higher peaks being cancelled. The overall amplitude of the sound waves is brought down. This helps in reducing noise. The pipe is also surrounded by a sleeve and the portion in between filled with glass wool. This reduces the noise further.

The emission device used in the Integrated N4 BS4 muffler is a combination of one DOC and two POCs. The DOC and the first POC are coated with precious metal while the second POC is uncoated. The combination of these three is very important in achieving the emission targets of BS4. An additional function performed by this combination is reducing noise. When the exhaust gases flow through the DOC/POC assembly, they are forced to flow through tiny holes/cells. The construction of the DOC/POC is such that there are about 300 to 400 cells per square inch of area. When the gases pass through such tiny spaces, they lose energy by virtue of friction with the inner walls and this helps reduce noise.

The exhaust gases, once they leave the inlet pipe, are forced to flow through the exponential connector (8). The exponential connector (8) is designed such that it helps the gases coming out of the inlet pipe to get compressed through the connector. The gases lose energy further resulting in loss of sound energy.

The gases then flow through the outlet pipe which ahs perforations which are made based on calculations which help in canceling certain frequencies of noise which otherwise would contribute to a higher noise level. The sound waves are subject to heir peaks being cancelled. The overall amplitude of the sound waves is brought down. This helps in reducing noise.

The inlet pipe is surrounded by glass wool which helps in reducing noise. The end baffles (the inlet end baffle (3a) and the outlet end baffle (3b)) on both sides have an embossed constructional feature which is also filled with glass wool and covered with a perforated plate. The construction of the glass wool is in the form of a continuous fiber. When the sound waves pass through the outlet tube, they pass through the perforations in the tube and into the chamber which is packed with glass wool. The glass wool absorbs the energy and vibrations of the sound waves. This helps in reducing sound intensity and gives better acoustic performance.

The three chambers form the reflective muffler. As the exhaust gas enters the inlet pipe, it goes straight to the second chamber because there is no path to escape into the first chamber. On entering the inlet pipe it comes across the first set of perforations on the inlet pipe surrounded by glass wool and comes out into the second chamber through the connector. This phenomenon can be explained by the following two points

i) Compression: the exhaust gas is initially present in the pipe, which is of larger diameter compared to the outlet of the connector. There is a difference between the volumes of the shell giving rise to compression of the gas through the connector. This gives the benefit of transmission loss, ii) Pipe perforation: the perforations are the specific designs to kill certain frequencies during the passage of the exhaust gases over the perforations on the pipe. The thickness of the pipe also plays a role. This gives benefit of transmission loss.

The exhaust gases from the inlet pipe go straight into the second chamber and hit the second baffle and get reflected resulting in reflected waves that cancel some of the incoming waves. This gives the benefit of transmission loss. Subsequently, the gases circulate in the second chamber and enter the second and third pipes. During this circulation, they lose velocity and hence energy thereby reducing transmission loss. The exhaust gases then enter the second and third pipes and get reflected from the first end cover thereby giving the benefit of transmission loss. The gases then pass through the perforations in the second and third pipes which are specifically designed to kill a particular frequency in the exhaust gases thereby giving the benefit of transmission loss. The reflective phenomenon is again observed at the exit of the gases from the fourth and fifth pipes when they are reflected from the second end cover. All this help in giving the benefit of increased transmission losses.

The exhaust gas that comes in through the inlet pipe, flows over the surface of the inlet pipe and its perforations and blasts the glass wool blanket that is wrapped around the inlet pipe perforations, resulting in attenuation of certain frequencies and spreading of the glass wool across the whole of the region around the perforation pipe and inside the sleeve. As the glass wool is packed such that it has filament thickness of the order of a few microns, there is a lot of surface contact between the exhaust gas escaping from the perforations and the filaments of the glass wool. This results in friction and conversion of acoustic energy into heat thereby helping in further transmission loss.
The same phenomenon is repeated in the perforation pipes four and five in the second chamber which are wrapped around by glass wool and a sleeve.

In addition to these, glass wool is also packaged in the embossed region of the end cover and a perforation plate is welded on it to prevent the glass wool from coming out. When the exhaust gases pass through these holes in the perforation plates, due to the surface contact, there is further loss of acoustic energy as heat.

The above explanation merely illustrates the principle of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein embody the principles of the invention and are included within the spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

Performance results:

Insertion loss test:

Insertion loss is a term used to define the effectiveness of a silencer/ exhaust system. The insertion loss of an exhaust system gives the indication of how much noise reduction of the engine is possible due to the silencer. The higher the insertion loss, the better it is from the noise perspective.

A comparative test of the invention with silencers of older/ different concepts shows that the noise performance of the N4 BS4 Rectangular integrated muffler is much better showing a considerable improvement of up to 2.4dB over a proprietary silencer with an older design.

The below shown table gives a comparison of the silencers tested in the same conditions on the same vehicle in terms of insertion loss.

(1) Jacket (1)
(2) Hollow region (2)
(3) Inlet end baffle (3a), outlet end baffle (3b)
(4) Inlet opening (4)
(5) Outlet opening (5)
(6) First baffle (6a), Second baffle (6b)
(7) Inlet tube (7)
(8) Exponential connector (8)
(9) Mid tube (9)
(10) DOC-POC Assembly tube (10)
(11) Outlet tube (11)
(12) Perforation in inlet tube (12)
(13) Perforation in mid tube in first chamber (13)
(14) Perforation in mid tube in second chamber (14)
(15) Perforation in outlet tube in third chamber (15)
(16) Glass wool on baffles (16)
(17) Glass wool on inlet tube (17) First chamber (A)
Second chamber (B) Third chamber (C)

We claim:

1. A muffler for regulating an engine exhaust in a vehicle the muffler comprising:
a jacket having a hollow region formed by an inlet end baffle having an inlet opening in it and an outlet end baffle having an having an outlet opening in it;
one or more baffles to have a first baffle and a second baffle attached inside the jacket in symmetry to the inlet opening and to the outlet opening to form one or more chambers inside the jacket to have a first chamber, a second chamber and a third chamber and the first baffle and the second baffle are capable of letting tubes pass through it and holding the tubes in place;
an inlet tube fixed to the inlet end baffle through the inlet opening and through the first baffle such that the other end of the inlet tube is exposed in the second chamber and the periphery of the inlet tube is exposed in the first chamber and in the second chamber;
one or more mid tube which is attached inside the jacket between the inlet end baffle and the second baffle through the first baffle such that the periphery of the mid tube is exposed in the first chamber and in the second chamber;
a DOC-POC assembly tube attached inside the jacket through the first baffle and through the second baffle such that one end of the DOC-POC assembly tube is exposed in the first chamber and the other end of the DOC-POC assembly tube is exposed in the third chamber and the periphery of the DOC-POC assembly tube is exposed in the first chamber, in the second chamber and in the third chamber; an outlet tube one end of which is attached on the second baffle and the other end of it is projected out of the outlet end baffle through the outlet opening such that the periphery of the outlet tube is exposed in the third chamber and outside the outlet end baffle wherein the main stream of the exhaust from the engine reaches the second chamber of the jacket through the inlet tube and takes 180 degrees turn through the mid tube to reach the first chamber and thereupon the main stream of the exhaust takes 180 degrees turn again to reach the third chamber through the DOC-POC assembly tube and thereupon the exhaust gas exits the jacket through the outlet tube.

2. The muffler as claimed in claim 1 wherein the inlet tube has perforations in its periphery in the region where it is exposed in the first chamber through which a part of the exhaust gas entering the inlet tube can enter the first chamber and the remaining exhaust gas enters the second chamber through an exponential connector (8) attached to the other end of the inlet tube.

3. The muffler as claimed in claim 1 wherein the mid tube has perforations in its periphery in the region where it is exposed in the first chamber and also has perforations in the region where it is exposed in the second chamber.

4. The muffler as claimed in claim 1 wherein the outlet tube has perforations in its periphery in the region where it is exposed in the third chamber.

5. The muffler as claimed in claim 1 wherein the first chamber, the second chamber and the third chamber are sealed with respect to tubes passing through it such that the flow of the exhaust gas from one chamber to the other is only through the tubes.

6. The muffler as claimed in claim 1 wherein the periphery of the first baffle, the second baffle, the inlet end baffle and the outlet end baffle are covered by glass wools and perforated plates to regulate the exhaust noise of the engine.

7. The muffler as claimed in claim 1 wherein the periphery of the inlet tube exposed in the region of the first chamber is covered by glass wools to regulate the noise of the engine.

8. The muffler as claimed in any one of the preceding claims wherein the perforations pattern of the inlet tube is such it has perforation of 2.8mm diameter with pitch 11mm and has 36 perforations in each row with 16 rows.

9. The muffler as claimed in any one of the preceding claims wherein the perforations pattern of the mid tube is such it has perforations of 7mm diameter with pitch 14 mm and has 12 perorations in each row with 10 rows and has perforations of 2.8mm diameter with pitch 10mm and has 30 perforations in each row with 18 rows in the region where it is exposed in the first chamber and it has perforations of 2.8mm diameter with 6mm pitch and has 40 perforations in each row with 17 rows in the region where it is exposed in the second chamber.

10. The muffler as claimed in any one of the preceding claims wherein the perforations pattern in the outlet tube is such it has perforations of 6mm diameter with 10mm pitch and has 16 perforations in each row with 18 rows in the region where it is exposed in the third chamber.

11. The muffler as claimed in claim 1 wherein the shape of the jacket of the muffler is rectangular.

12. The muffler as claimed in any one of the preceding claims wherein the tubes arranged inside the jacket are such that the back pressure created by the muffler on the engine is less.

13. The muffler as claimed in any one of the preceding claims wherein the exhaust gas from the engine under goes phase reversal inside the jacket twice before it exits the muffler to make the exhaust spark free and less noise.

14. The muffler as claimed in any one of the preceding claims wherein the perforation pattern present on the inlet tube, the mid tube and the outlet tube is based on the harmonics of the noise of the engine exhaust.