FIELD OF INVENTION

The invention relate to the design of muffler, which are used to control noise in the exhaust system. The invention particularly relates to the designs of Integrated Rectangular muffler, which negates the need of additional after treatment devices.

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, 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 unborn 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.

It is also an objective of the invention, to provide a single new muffler that would blend the performance characteristics of two different varieties of twin combinations, which negates the need of an additional spark-arrester and after treatment devises.
Yet another objective of the present invention is the reduction of back pressure, which improves the engine performance.

SUMMARY OF THE INVENTION

In order to achieve the above objective, the present invention provides a novel advanced integrated muffler for an inline pump engine, which incorporates the noise reduction principle of reflection and absorption and there by reduces the exhaust noise.

Accordingly, the present invention provides an advanced integrated 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 glass wool. 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.

The diesel oxidation catalyst (DOC) is a device which is integrated within the muffler assembly which reduces the particulate matter in the emissions. The DOC is coated with precious metal like platinum which aids in the oxidation process. The NOx in the emission is converted to N2 and 02 and this in turn helps in oxidizing the unburnt HC or particulate matter.

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 3 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 FVDP 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.

Consistent performance, reduced weight, reduced cost, decreased variety, ease in vehicle assembly and reduced component assembly time are the another advantage of the present invention.

BRIEF DESCRIPTION OF DRAWING

Figure 1 illustrates the preview of the present invention.

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

Figure 2 shows the cross sectional view of the muffler in the present invention.

Figure 4 shows an isometric view of the present invention

Figure 5 shows the front and cross sectional view of the three point flange employed in the rectangular muffler.

Figure 6 is the front and cross sectional view of the exponential connector.

Figure 7 is the side view of the perforated pipe.

DETAILED DESCRIPTION OF THE INVENTION

Referring to fig 1, the perspective view of the present invention, shows a hollow jacket in which the whole muffler assembly is arranged. The hollow jacket is rectangular in shape.

The inlet pipe and the outlet pipe are connected to the opposite sides of the hollow jacket. The exhaust gas enters in to the muffler assembly via the inlet pipe. The outer end of the inlet pipe is connected to a three point flange.

The front and the isometric view of the muffler assembly according to the present invention is illustrated in fig 2 and 4. The muffler of the present invention comprises a hollow jacket (11) which is covered at both ends by end covers (7, 8) having a hole. The jacket (11) is divided into three chambers (A, B, C) with the help of two plain baffles (9, 10). An inlet pipe (2) is inserted from the first end cover (7) and extended up to the second chamber of the jacket through the holes in the end cover (7) and the first baffle (9). 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 (4) inserted through the holes in the first baffle (9) from the second chamber and extend in to the first chamber and fixed on to the first baffle (9). A diesel oxidation catalyst (DOC) assembly is supported on the 2 inner baffles (9, 10). The assembly is such that all the exhaust gases in chamber A pass through the DOC assembly and into chamber C. This leads to a reduction in the exhaust emissions due to oxidation of the particulate matter in the exhaust gases.

The DOC is a coated substrate that coverts harmful components. A DOC can be referred as o a scrubber, purifier or a catalytic converter. The harmful elements of exhaust are both gaseous and solid in form. There are also components of exhaust that are not harmful. The DOC is coated with precious metal like platinum and/or palladium. These catalysts are oxidation catalysts which help in accelerating the oxidation reaction of the particulate matter. An additional function performed by this assembly is reducing noise. When the exhaust gases flow through the DOC assembly, they are forced to flow through tiny holes/cells. The construction of the DOC 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.

DOC utilizes a chemical process in order to break down pollutants from engines in the exhaust stream, luring them into less harmful components. They are normally a honey comb shaped configuration coated in a catalyst designed to trigger a chemical reaction to reduce particulate matter by typically 20 % to 40% +.when exhaust gas passes over the catalyst material, a chemical exchange occurs and emissions constituents (HC,CO,PM ) are oxidized to C02 and water. The oxidation catalysis is a passive technology. It is ideal for equipments that work indoor application. Unlike some after- treatment options, the oxidation catalyst can be used regarding of the level of sulfur in the fuel, although they are most effective with fuels that have sulfur content of 500 ppm or less.

An outlet pipe (6) is inserted from the second end cover (8) through the hole in the second end cover and extends up to the second baffle (10) 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 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 (2) could have about 12 rows of perforation with 36 holes per row. The inlet pipe (2) can extend 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 second and third sets of perforations are made on the second and third pipes (4). Preferably the diameter can be 2.8mm and the pitch can be about 6mm. The second and third sets could contain about 20 rows of perforations with about 40 perforations per row. The fourth set of perforation is made on the outlet pipe (6) 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 fourth set could contain about 18 rows of perforations with about 16 perforations per row.

In preferred embodiment, the three chambers (A, B, C) of the jacket (11) 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 a the corners. The length of the jacket (11) can preferably range from 620mm to 650mm. The jacket (11) 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 (11).

The end baffles on both sides have an embossed constructional feature which is also filled with glasswool and covered with a perforated plate. The construction of the glasswool 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 glasswool. The glasswool absorbs the energy and vibrations of the sound waves.

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

REFLECTIVE PRINCIPLE:

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 glasswool 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 through the perforations in the second and third pipe which are specifically designed to kill a particular frequency in the exhaust gases thereby giving the benefit of transmission loss. The same phenomenon is also noted in the outlet pipe. The exhaust gases then pass through the DOC where the emission levels are brought down. The reflective phenomenon is again observed at the exit of the gases from the DOC when they are reflected from the second end cover. All this help in giving the benefit of increased transmission losses.

ABSORPTIVE PRINCIPLE:

The exhaust gas that comes in through the inlet pipe, flows over the surface of the inlet pipe and its perforations and blasts the glasswool blanket that is wrapped around the inlet pipe perforations, resulting in attenuation of certain frequencies and spreading of the glasswool across the whole of the region around the perforation pipe and inside the sleeve. As the glasswool 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 glasswool. This results in friction and conversion of acoustic energy into heat thereby helping in further transmission loss.

In addition to these, glasswool is also packaged in the embossed region of the end cover and a perforation plate is welded on it to prevent the glasswool 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.

Thus it is clearly evident that the Advanced Integrated muffler of the present invention has a potential to reduce the noise level of the exhaust gas. It should be noted that the muffler of the present invention can also be used to reduce the noise level of the exhaust gases of power generator and the like.

Referring to Fig. No. 3, the cross section view of the muffler assembly shows the arrangement of pipes inside the hollow jacket. All pipes are arranged parallel to each other.

The front view and the cross sectional view of the connecting point flange is depicted in Fig 5. The flange has designed to connect the entre muffler assembly with the exhaust Pipe-Referring to Fig 6 shows the front and cross sectional view of the exponential connector. The exhaust gases, once they leave the inlet pipe, are forced to flow through the exponential connector. The exponential connector 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 side view of the perforated pipes is shown in Fig. 7. The different perforated pipes used in the muffler assembly are inlet, outlet and inner pipes. These pipes are designed 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.

Pass-by noise test:

The pass-by noise test is the critical test performed for any vehicle to be road worthy. The overall pass-by noise is the average of the noise measured on both the driver's side and also the co-driver's side with the measurement being taken at a distance of 7.5m from the tail pipe outlet. The regulations define the pass-by noise targets for vehicles with carious power ratings. For the vehicles using the silencer of the present invention and with a power output of 160hp (120kW), the PBN target is set at 78dB (A).

A comparative test of the invention with silencers of older/ different concept shows that the noise performance of the AL design 120IL BS3 Rectangular advanced integrated muffler is much better showing a considerable improvement of up to 3.2dB (A) overall 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 pass-by noise values.

We claim:

1. A rectangular muffler comprising:

a hollow jacket (11), plurality of baffles(9,10) with holes, an inlet pipe (2) adapted to allow exhaust gas to the flow to the hollow jacket and an out let pipe (6), at least a pairs of pipes (4) having provision to accommodate perforations, means for oxidize exhaust gas (5), wherein, the said components are arranged such that, to obtain maximum flow path and space for expansion for exhaust gas.

2. The rectangular muffler as claimed in claim 1:

wherein, hollow jacket (11) having a first end cover and second end cover (8) and the inlet pipe (2) is inserted at the first end cover of the hollow jacket and outlet pipe is attached second end cover.

3. The rectangular muffler as claimed in claim 1:

wherein, the baffle plates (9,10) are arranged inside the hollow jacket (11) to create plurality of chambers (A,B,C) and the pipes are arranged parallel inside the chambers.

4. The rectangular muffler as claimed in claim 1:
wherein the means for oxidizing exhaust gas is a ceramic based diesel oxidation catalyst (5) and is coated with precious metals.

5. The rectangular muffler as claimed in claim 1:
wherein, the end of the inlet pipe (2) is connected to a exponential connector (3), designed to compress the exhaust gas.

6. The rectangular muffler as claimed in claim 1:
wherein, the baffle plates (9,10) are having perforations on sides and the said perforated sides are wrapped with glasswool and cylindrical sleeve.7.

7. The rectangular muffler as claimed in claim 1:
wherein, the arrangement is such that the inlet pipe (2) is situated in between the first end cover and baffle plate(9,10 );

the succeeding chamber consist of pair of pipes and diesel oxidation unit (5) arranged parallel to each other and disposing to the last chamber.