FIELD OF INVENTION
The invention relates to a muffler for controlling noise in the exhaust system. The invention particularly relates to the designs of Rectangular muffler, which reduces the emission and noise.
BACKGROUND OF THE INVENTION
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.

In case of petroleum tanker application, conventionally a front exhaust system was made use. 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 unburnt 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. 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.

OBJECT OF THE INVENTION

The object of the present 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 and additionally accommodate various after treatment devices like DOC/POC and SCR systems.

It is also the objective of the invention to negate the need for using an additional spark arrestor.

SUMMARY OF THE INVENTION

In order to achieve the above objective, the present invention provides a hybrid muffler for automotive vehicles comprising a hollow jacket having a first and second end; a first end cover with a hole mounted on the first end of the jacket; a second end cover with a hole mounted on the second end of the jacket; two perforated baffles with five holes and two holes respectively in such a manner that the jacket is divided into three chambers by the two baffles, an inlet pipe extending from the first end of the jacket up to the second chamber of the jacket 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 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 glasswool and covered with a cylindrical sleeve. An outlet pipe fixed to the second baffle extends through the second end cover and outside with perforations around the circumference in the region of the third chamber.

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. Moreover, 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. In order to prevent the production of spark, the 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. In addition to 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. Also, 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 modular 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.

Furthermore, 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. Special acoustic elements like exponential connector 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.

BRIEF DESCRIPTION OF DRAWINGS

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same,

Figure 1 shows a perspective view of the present invention.

Figure 2 shows a front view of the muffler of the present invention.

Figure 3 shows a cross section view of the muffler of the present invention.

Figure 4 shows an isometric view of the present invention.

Figure 5 shows the front view of the inlet pipe of the muffler.

Figure 6 shows front view of the first middle pipe.

Figure 7 shows the front view of the second middle pipe.

Figure 8 shows front view of the outlet pipe.

Figure 9 shows the front and sectional views of the inlet flange.

Figure 10 shows a graph comparing the performance of the muffler of the present invention and the conventional muffler in idle condition.

Figure 11 shows a graph comparing the performance of the muffler of the present invention and the conventional muffler in maximum power condition.

Figure 12 shows a graph comparing the performance of the muffler of the present invention and the conventional muffler in fly-up condition.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG 1, a perspective view of the rectangular muffler which shows a rectangular hollow jacket (8), an inlet (2) and an outlet (7). The gas from the exhaust manifold enters via the inlet pipe (2). One end of the inlet pipe (2) is connected to a three point flange (1). The inlet and outlets are attached to the opposite faces of the hollow jacket (8).

The rectangular muffler as illustrated in Figure 2 and 4, comprises a hollow jacket (8) which is covered at both ends by end covers (9, 10) having a hole. The jacket (8) is divided into three chambers (A, B, C) using two plain baffles (15, 16). An inlet pipe (2) is inserted from the first end cover (9) and extended up to the second chamber of the jacket through the holes in the end cover (9) and the first baffle (15). One end of the inlet pipe (2) is connected to a three point flange (1) and the other end is fitted with a connector (3).

Two pipes (5) inserted through the holes in the first baffle (15) from the second chamber and extend up to the first chamber and fixed on to the first end cover (9). The other end of the two pipes is connected to a connector (4). Two more pipes (6) are inserted through the holes in the first and second baffles (15, 16) and extend into the first chamber and fixed there to the first end cover (9).

An outlet pipe (7) is inserted from the second end cover (10) through the hole in the second end cover and extends up to the second baffle (16) in the third chamber of the jacket and is fixed there. A portion of the inlet pipe (2) which is placed in the first chamber comprises of one set of perforations of predetermined size to eliminate 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 (2) could have about 16 rows of perforation with 36 holes per row. The inlet pipe (2) can extended into the second chamber for 40mm to 60mm, preferably 50mm. the connector (3) which is fixed to the free end of the inlet pipe (2) 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 (11). The second and third sets of perforations are made on the second i and third pipes (5). 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 (6) 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 (12) and enclosed inside a steel sleeve (13). 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 i perforations per row. The eighth set of perforation is made on the outlet pipe (7) 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.

The exhaust gas that enters 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.

In preferred embodiment, the three chambers (A, B, C) of the jacket (8) could have specific dimensions of 203.5mm, 198mm and 223.5mm respectively. The shape of the jacket (8) could be close to a rectangle with the longer sides containing a radius profile at the corners. The length of the jacket (8) can preferably range from 620mm to 650mm. The jacket (8) 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 (8).
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 on the on the basis of two key factors, compression and perforations present in the pipe. 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. Furthermore, 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. 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 eliminate a particular frequency in the exhaust gases thereby giving the benefit of transmission loss. The same phenomenon is noted in the fourth and fifth pipes and also the outlet pipe.

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.

Referring to figure 3, the cross sectional view of the rectangular muffler, clearly illustrates the different set of pipes and their arrangement. All the pipes are arranged parallel to each other.

Referring to fig.5, a front view of the inlet pipe, it is made by rolling a plane sheet such that the outer diameter is equal to 4 inches. The sheet is perforated with holes of 2.8mm diameter. A total of 576 holes are scattered in 16 rows of circumferential pattern of 36 holes around the pipe. The diameter for the hole is calculated such that it will attenuate certain frequencies. The number of holes is calculated keeping in mind the open area ratios decided.

Referring to fig 6, a front view of first mid pipe, it is also made by rolling a plane sheet such that the outer diameter is equal to 3 inches. The sheet is perforated with two sets of holes:

A) Holes of 2.8mm diameter:

A total of 540 holes are scattered in 18 rows of circumferential pattern of 30 holes around the pipe.

The diameter for the hole is calculated such that it will attenuate certain frequencies. The number of holes is calculated keeping in mind the open area ratios decided.

B) Holes of 7mm diameter:

A total of 120 holes are scattered in 10 rows of circumferential pattern of 12 holes around the pipe.

The diameter for the hole is calculated such that it will attenuate certain frequencies. The number of holes is calculated keeping in mind the open area ratios decided.

Figure 7 illustrates the second mid pipe. The sheet is perforated with holes of 2.8mm diameter. A total of 680 holes are scattered in 17 rows of circumferential pattern of 40 holes around the pipe. The diameter for the hole is calculated such that it will attenuate certain frequencies. The number of holes is calculated keeping in mind the open area ratios decided.

Figure 8 shows the outlet pipe, which is made by rolling a plane sheet such that the outer diameter is equal to 4 inches. The sheet is perforated with holes of 6mm diameter. A total of 144 holes are scattered in 9 rows of circumferential pattern of 16 holes around the pipe. The diameter for the hole is calculated such that it will attenuate certain frequencies. The number of holes is calculated keeping in mind the open area ratios decided.

Figure 9 depicts the front and cross sectional view of the three point flange (1), which used to connect the inlet pipe (2) to the jacket (8).The total width of the flange is 7mm.

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 measure of 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 AL design modular rectangular advanced integrated muffler is much better showing a considerable improvement of up to 1.3dB 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.

The illustrations no 10,11 and 12 depicts the insertion loss comparison of three different silencers, Cummins side outlet silencer (D7266663), Ashok Leyland side outlet silencer (D7266746) and Cummins rear outlet silencer (B7G01001) at different working conditions such as idle condition, maximum power condition and fly-up condition.

We claim

1. A rectangular muffler for vehicles comprising:

a hollow jacket (8), an inlet pipe (2) adapted to allow exhaust gas to flow in to the hollow jacket and a outlet pipe (7), having proficiency to accommodate perforations;

baffle plates (15, 16) with holes, set of pairs of pipes (5, 6), adapted to accommodate perforations, wherein, the said pipes are arranged such that, length of flow path of the exhaust gas is maximum.

2. A rectangular muffler for vehicles as claimed in claim 1;

wherein, hollow jacket (8) having a first end cover (9) and second end cover (10) and the inlet pipe (2) is inserted at the first end cover (9) of the hollow jacket (8) and outlet pipe is attached second end cover.

3. A rectangular muffler for vehicles as claimed in claim 1;

wherein, the baffle plates are arranged inside the hollow jacket to create plurality of chambers and the pipes are arranged parallel inside the chambers.

4. A rectangular muffler for vehicles as claimed in claim 1;

wherein, a steel sleeve (11) is provided to enclose the pipes.

5. A rectangular muffler for vehicles as claimed in claim 1;

wherein the arrangement is such that,

the first pair of pipes (5) is situated parallel to the inlet pipe, which is introduced
through the hole of the baffle (15) and attached to the hollow jacket (8);

the next pair of pipes (6) is attached to the upper side of the hollow jacket and
extended up to the second baffle (16) and having segments in first and second chamber,

and disposed to the third chamber (C).