Claims:We claim:

1. A hybrid exhaust system for reducing automotive exhaust noise, wherein the system comprises a pre-muffler and a pair of rear muffler disposed parallel to each other and connected downstream the pre-muffler; the pre-muffler and two rear-mufflers are configured to have different internal arrangement of pipes and baffles for tuning to different frequency range and optimized to increase the transmission loss in the respective frequency range.

2. Hybrid exhaust system as claimed in claim 1, wherein the pre-muffler is configured as cuboid, preferably a rectangular cuboid divided into three chambers by means of two perforated baffles disposed between the two longitudinal ends thereof.

3. Hybrid exhaust system as claimed in claim 2, wherein the first chamber acts as an inlet chamber; the second chamber acts as an expansion chamber and the third chamber acts as a resonator chamber.

4. Hybrid exhaust system as claimed in claim 3, wherein the volume of the first chamber is optimized by tuning the same for increasing the transmission loss in the lower range of frequency.

5. Hybrid exhaust system as claimed in claim 3, wherein the volume of the second chamber is optimized by tuning the same for increasing the transmission loss in the higher range of frequency by providing perforations in the baffles as well as pipe lengths disposed therein and by packing glass wool between the baffles to optimize the same to obtain predefined acoustic impedance for better performance.

6. Hybrid exhaust system as claimed in claim 5, wherein the second chamber comprises an inlet pipe and an outlet pipe and an intermediate pipe disposed therebetween, wherein perforations are provided in the pipes between the portions thereof disposed between the baffles, the perforations being configured with a predefined dimeter, number and spaced at a predefined in an optimized spatial pattern.

7. Hybrid exhaust system as claimed in claim 1, wherein the rear-muffler is configured as a profiled body, preferably a cylindrical body divided into three chambers by means of two baffles disposed between the two longitudinal ends thereof and the outlet end side baffle are configured with perforations.
8. Hybrid exhaust system as claimed in claim 7, wherein the first chamber acts as a resonator chamber; the second chamber acts as an expansion chamber and the third chamber acts as an absorptive chamber.

9. Hybrid exhaust system as claimed in claim 7, wherein the volume of the first chamber is optimized by tuning the same for increasing the transmission loss in the lower range of frequency.

10. Hybrid exhaust system as claimed in claim 7, wherein one end of the inlet pipe with an intermediate pipe disposed therein and connecting the first and second chambers; the outlet pipe having a U-bend disposed inside the first chamber and its inlet opening into the second chamber for expanding the recirculated exhaust gas (EGR).

11. Hybrid exhaust system as claimed in claim 7, wherein the volume of the third chamber is optimized by tuning the same for increasing the transmission loss in the higher range of frequency by providing perforations in the baffles and by packing glass wool between the baffle disposed towards the outlet opening side and the outlet side end of the rear muffler for optimizing it by obtaining predefined acoustic impedance for better performance.

12. Hybrid exhaust system as claimed in claim 5, wherein the second chamber comprises an inlet pipe and an outlet pipe and an intermediate pipe disposed therebetween, wherein perforations are provided in the pipes between the portions thereof disposed between the baffles, the perforations being configured with a predefined diameter, number and spaced at a predefined in an optimized spatial pattern.

Dated this day of 28th November, 2016. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to the field of the automotive exhaust system. In particular, the present invention relates to a tuned muffler for better sound characteristics having reduced sound pressure levels and higher transmission loss. More particularly, the present invention relates to an automotive muffler having better engine performance parameters.

BACKGROUND OF THE INVENTION

Automotive exhaust systems are used for controlling the pressure levels raised due to the noise generated during combustion process. For this purpose, different types of silencers or mufflers are used for substantially reducing the sound pressure levels of the exhaust gases being released to the atmosphere. With the increasing vehicle population, all over the world, particularly in a fast developing heavily populated countries like India, there is tremendous pressure on automobile manufacturers to reduce the sound levels of the automotive exhaust gases to be exhausted to the atmosphere to comply with the stringent environmental regulations.

Therefore, an optimum tuning of the muffler is an important design criteria during vehicle designing for obtaining reduced sound pressure levels.

This substantially increases the transmission losses, which in turn leads to better engine performance parameters. Another critical criterion while designing the automotive muffler is to tune it to different frequency ranges by using varying internal layout of pipes, baffles and by optimizing the chamber volumes to increase the transmission loss in the respective frequency range to ensure flow of exhaust gases to atmosphere.

DISADVANTAGES WITH THE PRIOR ART

However, there are several disadvantages associated with the existing automotive mufflers, which are briefly enumerated below:

• Low transmission loss in the frequencies below 250 Hz.

• Higher sound pressure levels in 2nd and 4th order between 1300-1800 rpm.

• Higher back pressure levels in 2nd and 4th order between 1300-1800 rpm.
Therefore, there is an existing need for redesigning the presently available automotive mufflers, e.g. of diesel variant of SUV XUV of the applicant, which provides a better NVH performance in the rear muffler by optimizing the transmission losses in different range of frequencies to substantially reduce the noise levels released to the atmosphere.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide an automotive muffler with higher transmission loss in lower frequency range.

Another object of the present invention is to provide an automotive muffler with better NVH performance.

Still another object of the present invention is to provide an automotive muffler with lower second and fourth order sound pressure levels.

Yet another object of the present invention is to provide an automotive muffler with better acoustic impedance and articulation index.

A still further object of the present invention is to provide an automotive muffler with better sound quality at lower costs.

A yet further object of the present invention is to provide an automotive muffler with lower sound levels throughout the vehicle in city driving conditions

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a hybrid exhaust system for reducing automotive exhaust noise, wherein the system comprises a pre-muffler and a pair of rear muffler disposed parallel to each other and connected downstream the pre-muffler; the pre-muffler and two rear-mufflers are configured to have different internal arrangement of pipes and baffles for tuning to different frequency range and optimized to increase the transmission loss in the respective frequency range.

In an embodiment of the present invention, the pre-muffler is configured as cuboid, preferably a rectangular cuboid divided into three chambers by means of two perforated baffles disposed between the two longitudinal ends thereof.

In another embodiment of the present invention, the first chamber acts as an inlet chamber; the second chamber acts as an expansion chamber and the third chamber acts as a resonator chamber.

In a still another embodiment of the present invention, the volume of the first chamber is optimized by tuning the same for increasing the transmission loss in the lower range of frequency.

In a yet another embodiment of the present invention, the volume of the second chamber is optimized by tuning the same for increasing the transmission loss in the higher range of frequency by providing perforations in the baffles as well as pipe lengths disposed therein and by packing glass wool between the baffles to optimize the same to obtain predefined acoustic impedance for better performance.

In an embodiment of the present invention, the second chamber comprises an inlet pipe and an outlet pipe and an intermediate pipe disposed therebetween, wherein perforations are provided in the pipes between the portions thereof disposed between the baffles, the perforations being configured with a predefined dimeter, number and spaced at a predefined in an optimized spatial pattern.

In a further embodiment of the present invention, the rear-muffler is configured as a profiled body, preferably a cylindrical body divided into three chambers by means of two baffles disposed between the two longitudinal ends thereof and the outlet end side baffle are configured with perforations.

In a still further embodiment of the present invention, the first chamber acts as a resonator chamber; the second chamber acts as an expansion chamber and the third chamber acts as an absorptive chamber.

In a yet further embodiment of the present invention, the volume of the first chamber is optimized by tuning the same for increasing the transmission loss in the lower range of frequency.

In a preferable embodiment of the present invention, one end of the inlet pipe with an intermediate pipe disposed therein and connecting the first and second chambers; the outlet pipe having a U-bend disposed inside the first chamber and its inlet opening into the second chamber for expanding the recirculated exhaust gas (EGR).

In a still further preferable embodiment of the present invention, the volume of the third chamber is optimized by tuning the same for increasing the transmission loss in the higher range of frequency by providing perforations in the baffles and by packing glass wool between the baffle disposed towards the outlet opening side and the outlet side end of the rear muffler for optimizing it by obtaining predefined acoustic impedance for better performance.

In a yet further preferable embodiment of the present invention, the second chamber comprises an inlet pipe and an outlet pipe and an intermediate pipe disposed therebetween, wherein perforations are provided in the pipes between the portions thereof disposed between the baffles, the perforations being configured with a predefined diameter, number and spaced at a predefined in an optimized spatial pattern.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, wherein:

Figure 1a shows a graph drawn for frequency (Hz) versus transmission loss TL (dB) for a conventional exhaust system of a petrol engine of a SUV.

Figure 1b shows a CFD diagram of the acoustic modes at 2nd order for a conventional exhaust system in a petrol engine of an SUV.

Figure 1c shows a CFD diagram of the acoustic modes at 4th order for a conventional exhaust system in a petrol engine of an SUV.

Figure 2a shows a comparative graph drawn for frequency (Hz) versus transmission loss TL (dB) for the conventional exhaust system and the exhaust system optimized in accordance with the present invention.

Figure 2b shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an exemplary exhaust system configured in accordance with the present invention.
Figure 2c shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 2d shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an improved exhaust system configured in accordance with the present invention indicating an improvement in transmission loss for the 4th order.

Figure 2e shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an improved exhaust system configured in accordance with the present invention indicating an improvement in transmission loss for the 6th order.

Figure 3a shows a schematic layout of an exemplary exhaust system configured in accordance with the present invention, including a pre-muffler and a rear-muffler for achieving tailpipe noise optimization.

Figure 3b shows a perspective view of the pre-muffler of the exhaust system of Fig.3a.

Figure 3c shows a top view of the pre-muffler of the exhaust system of Fig.3a.

Figure 3d shows a side view of the pre-muffler of the exhaust system of Fig.3a.

Figure 4a shows an internal layout of the pre-muffler of Fig.3c in top view.

Figure 4b shows a detailed front view of the schematic layout of components in the assembled housing 140 of the pre-muffler depicted in Fig. 4a.

Figure 4c shows an isometric view of the assembled housing 140 depicted in Fig. 4b.

Figure 4d shows an isometric view of the pre-muffler housing 140 depicted in Fig. 4c.

Figure 4e shows a front view of the housing of the pre-muffler of Fig. 4d.

Figure 4f shows a side view of the housing of the pre-muffler of Fig. 4f.

Figure 5a shows the front view of the inlet pipe of the pre-muffler of Fig. 4b.

Figure 5b shows the front view of the intermediate pipe of the pre-muffler of Fig. 4b.

Figure 5c shows the front view of the outlet pipe of the pre-muffler of Fig. 4b.

Figure 6a shows a perspective view of the rear-muffler of Fig. 3a.

Figure 6b shows a top view of the rear-muffler of Fig. 3a.

Figure 6c shows a side view of the rear-muffler of Fig. 3a.

Figure 6d shows internal layout of components in housing of rear-muffler of Fig. 6a.

Figure 6e shows a perspective view of the perspective front view of the housing 155 of the rear-muffler of Fig. 6a.

Figure 6f shows detailed front view of the assembly of rear-muffler of Fig. 6e.

Figure 6g shows a schematic layout of the rear-muffler of Fig. 6e.

Figure 7a shows a graph drawn for driver ear noise of the 2nd order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 7b shows a graph drawn for mid-seat row noise of the 2nd order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 7c shows a graph drawn for rear-seat row noise of the 2nd order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 8a shows a graph drawn for driver ear noise of the 4th order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 8b shows a graph drawn for mid-seat row noise of the 4th order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 8c shows a graph drawn for rear-seat row noise of the 4th order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention.

Figure 9a shows a bar-chart of the sound pressure level in part throttle city driving condition for the driver seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention.
Figure 9b shows a bar-chart of the sound pressure level in part throttle city driving condition for the mid-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 9c shows a bar-chart of the sound pressure level in part throttle city driving condition for the rear-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 10a shows a bar-chart of the Articulation Index (AI) in part throttle city driving condition for the driver seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 10b shows a bar-chart of the Articulation Index (AI) in part throttle city driving condition for the mid-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 10c shows a bar-chart of the Articulation Index (AI) in part throttle city driving condition for the rear-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 11a shows a bar-chart of the loudness (Sones) in part throttle city driving condition for the driver seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 11b shows a bar-chart of the loudness (Sones) in part throttle city driving condition for the mid-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

Figure 11c shows a bar-chart of the loudness (Sones) in part throttle city driving condition for the rear-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, the exemplary exhaust system configured in accordance with the present invention will be described in more details referring to the accompanying drawings without limiting the scope and ambit of the present invention.

Figure 1a shows a graph drawn for frequency (Hz) versus transmission loss TL (dB) for a conventional or baseline exhaust system of a petrol engine of a SUV. Accordingly, low transmission loss (TL) is identified below 250 Hz and acoustic modes at frequencies of 78 Hz, 180 Hz and 280 Hz respectively. Here, the dominant orders are, 2nd order, i.e. 1000-4500 rpm having frequency in the range of 33-166 Hz and 4th order, i.e. 1000-4500 rpm having frequency in the range of 66-333 Hz.

Figure 1b shows a CFD diagram of the acoustic modes at 2nd order for a conventional exhaust system in a petrol engine of an SUV at 78.7 Hz frequency. It is clear from this diagram that the 2nd order is dominant at 2500-3500 rpm having frequency in the range of 83-116.6 Hz and 4th order is dominant at 1300-1500 rpm having frequency in the range of 86-100 Hz.

Figure 1c shows a CFD diagram of the acoustic modes at 4th order for a conventional exhaust system in a petrol engine of an SUV at 284.5 Hz frequency. However, a difference of 12 dB(A) is observed between the baseline and targeted tail pipe noise, which was considered while designing the exhaust system configured in accordance with the present invention. This transmission loss (TL) is increased by using a combination of a pre-muffler and a rear muffler discussed in the following referring to Figs. 3-12.

Figure 2a shows a comparative graph drawn for frequency (Hz) versus transmission loss TL (dB) for the conventional exhaust system and the exemplary exhaust system optimized in accordance with the present invention, which achieves an improvement of 10-20 dB(A).

Figure 2b shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an exemplary exhaust system configured in accordance with the present invention indicating an overall improvement of 10dB(A) in tail-pipe noise.

Figure 2c shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an improved exhaust system configured in accordance with the present invention indicating improvement in a range of 5-10 dB(A) in tail-pipe noise.

Figure 2d shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an improved exhaust system configured in accordance with the present invention indicating improvement of 10dB(A) in tail-pipe noise.

Figure 2e shows a comparative graph drawn for frequency (Hz) v/s tailpipe noise (dB) for a conventional exhaust system and an improved exhaust system configured in accordance with the present invention indicating a substantial improvement in tail-pipe noise.

Figure 3a shows a schematic layout of an exemplary exhaust system configured in accordance with the present invention, including a combination of 12 Lit pre-muffler 100 and two rear-mufflers 150 disposed in parallel and connected downstream to the pre-muffler 100 for obtaining substantially improved NVH performance, e.g. 5-10 dB(A) reduction in sound pressure levels as compared to the baseline model discussed in Figure 1a-c.

Figure 3b shows a perspective view of the pre-muffler 100 of exhaust system of Fig.3a. It includes an undulating and profiled outer surface with inlet pipe opening 102 at one end thereof and an outlet pipe opening 142 at the other end thereof. A bulged portion 108 is configured from the inlet pipe end to a portion of the expansion chamber. However, the top portion of bulge is provided to increase the travel of the exhaust gases which in turn increases the effective length and diameter of the inlet pipe and thereby results in a better expansion in the first chamber.

Figure 3c shows a top view of the pre-muffler 100 of the exhaust system of Fig.3a. It includes 3 chambers, i.e. first chamber 110 for exhaust gas inlet, second chamber 120 for expansion and a third chamber 130 for Helmholtz resonance. The exhaust gas is introduced into the pre-muffler 100 via an inlet opening 102 through a profiled inlet pipe 104 which is in fluid communication with the expansion chamber 120 and resonator chamber 130 to be discussed below. The volume of each of these three chambers 110, 120, 130 is optimized to be tuned for the particular range of frequency. Moreover, the volumes are increasing progressively from inlet chamber 110 to exhaust chamber 130. For example, the first chamber 110 in the present embodiment has 4.4 Lit volume and the first end 136 of the outlet pipe 136 opens in this chamber 110. It is tuned for better transmission loss for lower range of frequency. The second chamber 120 has 3.7 Lit volume. It is tuned for high range of frequency with the help of holes provided on baffles 115, 135 and ADVANTEX Glass wool packed between the baffle 135 and the right-hand side end plate of the housing 155. The hole size is optimized to obtain the desired acoustic impedance for better performance of the muffler. Perforations opens the bore to the outside air to shorten the effective length of the outlet pipe 132. The sound waves are reflected at or near this point, because the holes provide an acoustical 'short circuit' to the outside air. However, it is more complicated for high frequencies. The air in and near the hole has some mass and for the sound waves to pass through the hole, this mass needs to be accelerated and this required acceleration (all else being equal) is increased with the square of the frequency:

For a high frequency sound wave, there is hardly any time in half cycle to get it moving. Therefore, the high frequency waves are impeded by the air in the hole: It does not 'look so open' to the high frequency waves as it does to the low frequency waves.

The low frequency waves are reflected at the first open hole, whereas the higher frequency waves travel further and sufficiently high frequency waves travel down the outlet pipe past the open holes. Thus, an array of open tone holes acts as a high pass filter: It lets high frequency waves to pass through but rejects the low frequency waves. The cut-off frequency fc depends on the geometry. However, there is an approximate and simple equation that is given by:
fc = 0.11 (b/a)v/(st)½
wherein,
a = radius of the pipe diameter,
b = radius of a hole,
v = speed of sound,
s = half the typical spacing between holes, and
t = typical effective length of the hole, including end effects.

The third chamber 130 is filled with glass wool having a packing density of 340 gms/Lit which helps in improving the transmission loss (TL) in the higher range of frequencies. This glass-wool quantity is optimized for obtaining better sound quality at reduced costs.

Figure 3d shows a side view of the pre-muffler 100 of the exhaust system of Fig.3a. It clearly depicts the inlet opening 102 for introducing the exhaust gas and the bulged portion 108.

Figure 4a shows an internal layout of the pre-muffler 100 of Fig.3c in top view depicting inlet chamber 110 with inlet opening 102 for inlet pipe 104, expansion chamber 120 and resonant chamber 130 with outlet opening 142.

Figure 4b shows a detailed front view of the schematic layout of components in the assembled housing 140 of the pre-muffler depicted in Fig. 4a. It includes a housing 140 divided into 3 chambers, the first chamber 110, the second chamber 120 and the third chamber 130 by means of two baffle plates 115 and 135 respectively. The profiled inlet pipe 104 has an open inlet end 102 and another end 112 opening into the resonator chamber 130. The inlet pipe 104 has a plurality of perforations 106 in its straight length disposed within the expansion chamber 120 and near the first ends of the baffle plates 115, 135. The outlet pipe 132 opens at one end 136 into the inlet chamber 110 and includes a plurality of perforations 134 in its straight length disposed within the expansion chamber 120 and near the second ends of the baffle plates 115, 135. The other end of the outlet pipe 132 opens at 142 to be connected to the exhaust pipe of the vehicle opening into the atmosphere. A perforated pipe 125 is substantially centrally disposed between the two ends of the baffle plates 115, 135 and thereby between straight lengths of the inlet pipe 104 and outlet pipe 132.

Figure 4c shows isometric view of assembled housing 140 depicted in Fig. 4b. Here, the second chamber 120 is optimized by tuning the same for increasing the transmission loss in the higher range of frequency by providing holes in the baffles 115, 135 and by packing glass wool between the baffles 115, 135 to optimize the second chamber for obtaining the desired acoustic impedance for better performance of the pre-muffler.

Figure 4d shows an isometric view of the housing 140 of the pre-muffler depicted in Fig. 4c. Here, pre-muffler housing 140 is depicted with baffles 115, 135 dividing this into three chambers, i.e. inlet chamber 110, expansion chamber 120 and resonator chamber 130 respectively. The exhaust gas is introduced into the pre-muffler 100 via an inlet opening 102 through a profiled inlet pipe 104, a portion of which disposed inside the expansion chamber has a plurality of perforations in a predetermined pattern. The arrows show the direction of movement of exhaust gas through the perforations in the pipes 106, 125 and 134 as well as in three chambers 110, 120, 130 respectively.

Figure 4e shows a front view of the housing of the pre-muffler of Fig. 4d, which includes inlet chamber 110, expansion chamber 120 and resonator chamber 130 divided by means of baffles 115 and 135.

Figure 4f shows a side view of the housing of the pre-muffler of Fig. 4f, which is also indicating bulged portion 108.

Figure 5a shows the front view of the inlet pipe 104 of the pre-muffler 100 having inlet 102, perforated portion 106 and outlet 112 opening into resonator chamber 130.
Figure 5b shows the front view of the intermediate pipe 125 of pre-muffler 100 with inlet 122, perforated portion 115 and outlet 124 opening into resonator chamber 130.

Figure 5c shows the front view of outlet pipe 132 of pre-muffler 100 having inlet 136, perforated portion 134 and outlet 142 opening out of housing 140 to be connected to exhaust pipe releasing the cooled and low-noise exhaust gas into the connecting Rear muffler inlet pipe 152.

Figure 6a shows a perspective view of the rear-muffler 150 of Fig. 3a.

Figure 6b shows a top view of the rear-muffler 150 of Fig. 6a depicting inlet pipe 152 and outlet pipe 154. It also has 156 which is hanger rod, one of the path to transfer structure borne noise to the exhaust system and 158 is outlet pipe which is getting connected to tailpipe helps in releasing exhaust gases to atmosphere through 154.

Figure 6c shows a side view of the rear-muffler 150 of Fig. 6a also depicting inlet pipe 152 and 156 is exhaust hanger rod, one of the path to transfer structure borne noise to the exhaust system.

Figure 6d shows an internal layout of the components in the housing of the rear-muffler 150 of Fig. 6a without the housing 155 (Fig. 6a) thereof.

Figure 6e shows a perspective view of the front view of the housing assembly of the rear-muffler 150 of Fig. 6a. It includes a housing 155, divided into 3 chambers by means of partition walls 162, 164, 166 and 168. The first chamber 172 is a resonator chamber, the second chamber 174 is an expansion chamber and the third chamber 176 is an absorptive chamber.

Figure 6f shows a detailed front view of the assembly of the rear-muffler of Fig. 6e. The inlet pipe 152 passes through the resonator chamber 172 and opens into the second chamber 174 adjacent the muffler center axis Y-Y. The outlet pipe 158 is connected to a U-band 160 also opening into the second chamber 174 adjacent the muffler center axis Y-Y. Here, it is important to note that partition wall 166 is perforated and the third absorptive chamber 176 is filled with glass wool to facilitate noise absorption therein. Rear muffler 150 is configured as an elliptical muffler with 10 Lit volume and having 3 chambers 172, 174, 176 made by means of two baffles 164, 166. The volume for each chamber 172, 174, 176 is optimized to tune a particular band of frequency and the chamber volumes increase progressively till the exhaust gas is allowed to expand in 2nd chamber 174. The first chamber 172 has 4.2 Lit volume and is formed by the inlet end 162 of the housing 155 and the first baffle 164. A tuned resonator pipe 165 opens in this chamber 172, which is responsible for better transmission loss for lower range of frequency. The second chamber 174 has 4.6 Lit volume and both inlet pipe 152 and outlet pipe 158 open in this chamber 172 formed by means two baffles 164, 166. The third chamber 176 has 1.2 Lit volume and it is tuned for high frequency with the help of holes provided on the baffles 164, 166 and ADVANTEX Glass wool packed between the second baffle 166 and the outlet end 168 of the housing 155. The hole size is optimized to obtain the desired acoustic impedance for better performance of the muffler. Glass wool packed with a packing density 100gms/Lit in the third chamber 176 helps in improving the transmission loss (TL) in the higher range of frequencies. The glass-wool quantity is also optimized for better sound quality along with cost saving.

Figure 6g shows a schematic layout of the rear-muffler 150 of Fig. 6e with its housing assembly 155 enclosed within an outer shell 180 with undulating surface.

Figure 7a shows a graph drawn for driver ear noise of the 2nd order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention, which achieves 10 dB reduction at 1600 rpm and 8 dB reduction at 2400 rpm with respective rpm.

Figure 7b shows a graph drawn for mid-seat row noise of the 2nd order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention, which achieves 3 dB reduction at 1600 rpm and 10 dB reduction at 2400 rpm with respective rpm.

Figure 7c shows a graph drawn for rear-seat row noise of the 2nd order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention, which achieves 6 dB reduction at 1600 rpm and 8 dB reduction at 2400 rpm with respective rpm.

Figure 8a shows a graph drawn for driver ear noise of the 4th order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention which achieves 6 dB reduction at 1400 rpm.

Figure 8b shows a graph drawn for mid-seat row noise of the 4th order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention, which achieves 10 dB reduction at 1200 rpm and 6 dB reduction at 2400 rpm with respective rpm.

Figure 8c shows a graph drawn for rear-seat row noise of the 4th order compared between the conventional exhaust system and an improved exhaust system configured in accordance with the present invention, which achieves 10 dB reduction at 1200 rpm and 18dB reduction at 2400 rpm with respective rpm.

Figure 9a shows a bar-chart of the sound pressure level in part throttle city driving condition for the driver seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 4 dB(A) reduction with respect to the baseline configuration.

Figure 9b shows a bar-chart of the sound pressure level in part throttle city driving condition for the mid-row seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 4.5 dB(A) reduction with respect to the baseline configuration.

Figure 9c shows a bar-chart of the sound pressure level in part throttle city driving condition for the rear-row seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 4 dB(A) reduction with respect to the baseline configuration.

Figure 10a shows a bar-chart of the Articulation Index (AI) in part throttle city driving condition for the driver seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 8% increase with respect to the baseline configuration.

Figure 10b shows a bar-chart of the Articulation Index (AI) in part throttle city driving condition for the mid-row seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 9% increase with respect to the baseline configuration.

Figure 10c shows a bar-chart of the Articulation Index (AI) in part throttle city driving condition for the rear-row seat compared between the conventional exhaust system and the exemplary exhaust system configured according to the present invention having 7% increase with respect to baseline configuration.

Figure 11a shows a bar-chart of the loudness (Sones) in part throttle city driving condition for the driver seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 5 Sones reduction with respect to the baseline configuration.

Figure 11b shows a bar-chart of the loudness (Sones) in part throttle city driving condition for the mid-row seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 7 Sones reduction with respect to the baseline configuration.

Figure 11c shows a bar-chart of the loudness (Sones) in part throttle city driving condition for the rear-row seat compared between the conventional exhaust system and the exemplary exhaust system configured in accordance with the present invention, which has 4 Sones reduction with respect to the baseline configuration.

WORKING PRINCIPLE OF THE INVENTION

In the exemplary exhaust system configured in accordance with the present invention, the exhaust mid-muffler is located at center and a twin muffler is located at the rear side of the exhaust system and the tailpipe thereof blows sideways to the offside for venting the exhaust gases to the atmosphere. Here, the internal configuration of the mid-muffler and twin rear muffler of the innovative exhaust system are tuned to suppress the high noise created by the engine by releasing the exhaust gases into atmosphere by providing better sound characteristics with reduced sound pressure levels, back pressure and by providing a higher transmission loss .Moreover, it has substantially improved parameters for engine performance, such as lower fuel consumption, lower NOx and hydrocarbon levels.

TECHNICAL ADVANTAGES & ECONOMIC SIGNIFICANCE

Some of the technical advantages of the exemplary exhaust system configured in accordance with the present invention are as under:

• Better sound characteristics.
• Reduced sound pressure levels.
• Higher transmission loss.
• Less fuel consumption.
• Less NOx and hydrocarbon levels.
• Can be tuned with different frequencies.
• Optimized configuration by increasing transmission loss.
• Efficient exhaust gas flow to the atmosphere.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure to achieve one or more of the intended objects or results of the present invention.

The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention. The description provided herein is purely by way of example and illustration.

Although the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention.

These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.