Claims:We claim:

1. A compact underhood muffler of elongated section to reduce the back-pressure and sound pressure of the exhaust gases from the internal combustion engines, wherein the muffler comprises:

(a) a main chamber configured with an inlet tube partially provided with circumferential holes and a non-perforated outlet tube for carrying the exhaust gas to be treated inside the main chamber, the inlet and outlet tubes mutually disposed in parallel and opening on the same side of the main chamber;

(b) a plurality of sub-chambers configured within the main chamber by means of a respective separating wall provided with holes for the passage of inlet tube and outlet tube therethrough, each sub-chamber and the sub-chamber disposed downstream thereof in the incoming exhaust gas flow direction having a predetermined increasing volume ratio for optimally tuning to a particular band of frequency, preferably from a lower range of frequency at the inlet tube entry to a higher range of frequency at the inlet tube exit,

(c) a largest volume chamber disposed downstream the last sub-chamber in the incoming exhaust gas flow direction, which is configured for achieving better transmission loss for higher range of frequency, and

(d) a smallest volume end-chamber disposed downstream the largest volume chamber in the exhaust gas flow direction, which is configured for tuning to high range of frequency by means of perforations provided in the wall separating it from the largest volume chamber for reducing the end plate heating issues,

wherein the circumferential holes in the inlet tube are uniformly distributed to open the inlet tube bore to create acoustic short circuits to the outside air for reducing the effective length of the inlet tube and the plurality of sub-chambers and the smallest chamber are packed with the glass-wool in a predetermined packing density optimized for improving the transmission loss at higher range of frequency.

2. An underhood muffler as claimed in claim 1, wherein the elongated section is an elliptical section.

3. An underhood muffler as claimed in claim 1, wherein the main chamber is configured as an elliptical chamber with an apertured end plate and a closed end plate, the apertured end plate having one hole each for the passage of the inlet tube and the outlet tube therethrough respectively.

4. An underhood muffler as claimed in claim 3, wherein the first ends of the inlet tube and the outlet tube partially protrude out of the apertured end plate.

5. An underhood muffler as claimed in claim 1, wherein the main chamber comprises three sub-chambers with the volume ratio progressively increasing approximately in a ratio of 1:1.2, 1: 1.5, 1:2 respectively with respect to the first sub-chamber and the largest chamber and the smallest chamber having volume ratios of 1: 2.5 and 1: 0.6 with respect to the first sub-chamber.

6. An underhood muffler as claimed in claim 1, wherein the main chamber comprises the volumes of the first, second and third sub-chambers are approximately in a range of 0.55 to 0.65, 0.65 to 0.75 and 0.80 to 0.90 L respectively, the volume of the largest chamber is approximately in a range of 1.00 to 1.10 L and the volume of the smallest chamber is approximately in a range of 0.30 to 0.40 L.

7. An underhood muffler as claimed in claim 1, wherein the main chamber is elliptical in section and the separating walls configuring the first, second and third sub-chambers are the first, second and third elliptical baffle plates disposed space apart from the apertured end plate and fitted inside the main chamber in a sealing manner and the largest chamber and the smallest chamber are configured by means of a perforated elliptical baffle plate disposed between the third baffle plate and the close end plate of the main chamber for reducing the closed end plate heating issues and for tuning the high frequency waves.

8. An underhood muffler as claimed in claim 7, wherein the inlet tube comprises circumferential holes between the apertured end plate of the main chamber and the third baffle plate and the exit end of the inlet tube protrudes out of the third baffle plate by a predetermined length, and the inlet end of the non-perforated outlet tube ends at the third baffle plate.

9. An underhood muffler as claimed in claim 1, wherein the packing density of glass wool is in a range of 150 to 200 g/L, preferably 200 g/L.

10. An underhood muffler as claimed in claim 1, wherein the first, second and third baffle plates as well as perforated baffle plate are configured as separating walls made of steel, preferably mild steel of thickness between 1 mm to 2 mm, preferably 1.5 mm.

Dated: this 28th day of September, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to muffler or silencers for motor vehicles. In particular, the present invention relates to mufflers or silencers for tractors. More particularly, the present invention relates to underhood mufflers or silencers for tractors.

BACKGROUND OF THE INVENTION

An internal combustion (IC) engines is a major source of noise pollution. Any sound having a noise level above 80 dB is injurious to human beings and thus not acceptable. The main sources of noise in any IC engine are the exhaust gases produced and the friction between various components. However, the exhaust gas noise is a predominant part of the IC engine noise pollution.

A muffler or silencer is a device to reduce the noise emitted by the exhaust port/s of an IC engine. The level of exhaust noise reduction depends on the construction and operation of the muffler.

In farm equipment, e.g. tractors, the muffler is generally fitted as an underhood muffler, which extends above the engine hood or bonnet to lead the treated exhaust gases away from the engine, particularly via an exhaust pipe extending upwardly through the engine hood.

Therefore, the tractor muffler is constructed as acoustic soundproofing device configured to suppress the acoustic pulse generated by the combustion process and thereby to reduce the noise level of the exhaust gases emitted to the atmosphere. The majority of acoustic pressure produced in the engine is exhausted from of the vehicle via the same piping which is used by the exhaust gases muffled by a series of passages and glass insulation lined. In addition, resonating chambers are harmonically tuned to produce destructive interference for cancellation of the opposite sound waves by each other. An inherent side effect of using a muffler is increased back pressure, which decreases the IC engine efficiency.

Any internal combustion engine produces high intensity pressure wave, which are propagated along the exhaust pipe and emitted to the atmosphere from the exhaust pipe outlet. Generally, the acoustic pulse repeats at the firing frequency of the IC engine, which is defined by:

f = engine rpm x number of cylinders / 120……[for four stroke engines]

The exhaust noise frequency is predominantly composed of a pulse at the firing frequency. However, it also has a broadband component to the spectrum thereof, which also extends to higher frequencies.

Therefore, the exhaust mufflers are configured to reduce the sound levels at all these frequencies.

DISADVANTAGES WITH THE PRIOR ART

The back pressure decreases the IC engine efficiency. This is due to the fact that the IC engine exhaust has to be shared by both the complex exhaust passage built inside the muffler and the designed acoustic pressure of the muffler. This back pressure develops, when the exhaust gases flow from the IC engine to the atmosphere is obstructed in any way and therefore, the efficiency of the engine and so the power is also reduced.

Therefore, it is necessary to develop performance-oriented mufflers and exhaust systems, which are aimed at minimizing the back pressure by employing different technologies and processes to attenuate the sound produced by IC engine exhaust gases. It is also necessary to have lower back pressure values. It is further required to have reduced noise levels along with reduced emissions and improved or at least the same fuel efficiency.

Therefore, there is a long felt need for eliminating the disadvantages associated with the conventional mufflers or silencers in automotive engines, particularly farm equipment, and more particularly underhood mufflers used in tractors.

DESCRIPTION OF THE PRESENT INVENTION

The sound waves propagating along an exhaust pipe are attenuated by using dissipative and/or reactive muffler. The dissipative muffler makes use of sound absorbing material to absorb the energy from the acoustic motion of the wave, while its propagation through the muffler. The reactive mufflers normally used in automotive applications reflect the sound waves back towards to source and prevent the sound from being transmitted along the exhaust pipe. The reactive silencer design is based on the principle of a Helmholtz resonator and/or includes at least one expansion chamber. This type of muffler applies the acoustic transmission line theory. A hollow cavity is provided in the exhaust pipe of the Helmholtz resonator, which resonates at a specific frequency and the waves in the exhaust pipe are reflected back towards the source. However, the resonator has no effect in the pass band frequencies and thus the resonator muffler is aimed at specific frequencies, where the most of the attenuation is desirable. The muffler can also have multiple resonators of different sizes to target a range of frequencies. The expansion chamber mufflers reflect acoustic waves by introducing a sudden change in cross sectional area of the pipe. Unlike Helmholtz resonator, expansion chamber mufflers do not show high attenuation; however these have a broadband frequency characteristic in pass band frequencies, when half the acoustic wavelength is equal to the cavity length. The expansion chamber mufflers can also be packed with sound absorbing material to help in improving the high frequency attenuation. The tailpipe length can also have a significant effect, because the tailpipe itself acts as a resonant cavity which couples with the muffler cavity.

Generally, the term Transmission Loss (TL) means the accumulated decrease in intensity of a waveform energy as the wave propagates away from a source, or as it propagates through a specific area or through a specific type of structure. The measurement of TL is very important in the acoustic devices such as mufflers and is defined as the difference between the incident wave power coming towards the muffler’s specific area/structure and the transmitted wave power going away from the specific area or structure of the muffler.

The transmission loss (TL) is measured in dB scale and can be generally defined by using the following formula:

wherein,

and further wherein,

and are the transmitted and incident wave power respectively.

Accordingly, using above characteristics for configuring each chamber of the muffler can be tuned to a particular frequency range for obtaining better/optimized transmission loss therein.

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 underhood muffler of elongated section having reduced back pressure values.

Another object of the present invention is to provide an underhood muffler of elongated section having lower sound pressure levels.

Still another object of the present invention is to provide an underhood muffler of elongated section having reduced emissions.

Yet another object of the present invention is to provide an underhood muffler of elongated section having improved or at least the same fuel efficiency.

A further object of the present invention is to provide an underhood muffler of elongated section having improved transmission loss (TL) characteristics.

Still further object of the present invention is to provide an underhood muffler of elongated section having improved acoustic impedance for better muffler performance.

Yet further object of the present invention is to provide an underhood muffler of elongated section for eliminating end plate heating issues.

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 compact underhood muffler of elongated section to reduce the back-pressure and sound pressure of the exhaust gases from the internal combustion engines, wherein the muffler comprises:

a) a main chamber configured with an inlet tube partially provided with circumferential holes and a non-perforated outlet tube for carrying the exhaust gas to be treated inside the main chamber, the inlet and outlet tubes mutually disposed in parallel and opening on the same side of the main chamber;

b) a plurality of sub-chambers configured within the main chamber by means of a respective separating wall provided with holes for the passage of inlet tube and outlet tube therethrough, each sub-chamber and the sub-chamber disposed downstream thereof in the incoming exhaust gas flow direction having a predetermined increasing volume ratio for optimally tuning to a particular band of frequency, preferably from a lower range of frequency at the inlet tube entry to a higher range of frequency at the inlet tube exit,

c) a largest volume chamber disposed downstream the last sub-chamber in the incoming exhaust gas flow direction, which is configured for achieving better transmission loss for higher range of frequency, and

d) a smallest volume end-chamber disposed downstream the largest volume chamber in the exhaust gas flow direction, which is configured for tuning to high range of frequency by means of perforations provided in the wall separating it from the largest volume chamber for reducing the end plate heating issues,

wherein the circumferential holes in the inlet tube are uniformly distributed to open the inlet tube bore to create acoustic short circuits to the outside air for reducing the effective length of the inlet tube and the plurality of sub-chambers and the smallest chamber are packed with the glass-wool in a predetermined packing density optimized for improving the transmission loss at higher range of frequency.

Typically, the elongated section is an elliptical section.

Typically, the main chamber is configured as an elliptical chamber with an apertured end plate and a closed end plate, the apertured end plate having one hole each for the passage of the inlet tube and the outlet tube therethrough respectively.

Typically, the first ends of the inlet tube and the outlet tube partially protrude out of the apertured end plate.

Typically, the main chamber comprises three sub-chambers with the volume ratio progressively increasing approximately in a ratio of 1:1.2, 1: 1.5, 1:2 respectively with respect to the first sub-chamber and the largest chamber and the smallest chamber having volume ratios of 1: 2.5 and 1: 0.6 with respect to the first sub-chamber.

Typically, the main chamber comprises the volumes of the first, second and third sub-chambers are approximately in a range of 0.55 to 0.65, 0.65 to 0.75 and 0.80 to 0.90 L respectively, the volume of the largest chamber is approximately in a range of 1.00 to 1.10 L and the volume of the smallest chamber is approximately in a range of 0.30 to 0.40 L.

Typically, the main chamber is elliptical in section and the separating walls configuring the first, second and third sub-chambers are the first, second and third elliptical baffle plates disposed space apart from the apertured end plate and fitted inside the main chamber in a sealing manner and the largest chamber and the smallest chamber are configured by means of a perforated elliptical baffle plate disposed between the third baffle plate and the close end plate of the main chamber for reducing the closed end plate heating issues and for tuning the high frequency waves.

Typically, the inlet tube comprises circumferential holes between the apertured end plate of the main chamber and the third baffle plate and the exit end of the inlet tube protrudes out of the third baffle plate by a predetermined length, and the inlet end of the non-perforated outlet tube ends at the third baffle plate.

Typically, the packing density of glass wool is in a range of 150 to 200 g/L, preferably 200 g/L.

Typically, the first, second and third baffle plates as well as perforated baffle plate are configured as separating walls made of steel, preferably mild steel of thickness between 1 mm to 2 mm, preferably 1.5 mm.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

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

Figure 1 shows a perspective view of an embodiment of the underhood muffler of elongated section in accordance with the present invention.

Figure 2 shows a detailed perspective view of underhood muffler of Figure 1.

Figure 3 shows the front views of the elliptical end plates and the baffles plates of the underhood muffler of Figures 1 and 3.

Figure 4 shows a schematic figure for the muffler chambers and relationship of different values thereof for deciding the muffler chamber configuration.

Figure 5 shows the typical behavior of the exhaust gases entering through the holes in the inlet pipe of the muffler.

Figure 6 shows a graph representing the comparison of the curves of the transmission loss (TL) drawn against the frequency (f) for the baseline (conventional) muffler and the elliptical muffler 100 according to the invention.

Figure 7 shows another graph representing the comparison of Brake Specific Fuel Consumption (BSFC) of 4-Cylinder Diesel engine drawn against Engine RPM for the baseline (conventional) muffler and the underhood muffler 100 according to the present invention.

Figure 8 shows a graph for the sound pressure levels at the exhaust orifice [2nd Order engine firing frequency in a 4-Cylinder diesel engine] drawn against the engine speed (in rpm) for the baseline (conventional) muffler and the underhood muffler 100 according to the present invention.

Figure 9 shows another graph for the sound pressure levels at the exhaust orifice [4th Order engine firing frequency in a 4-Cylinder diesel engine] drawn against the engine speed (in rpm) for the baseline (conventional) muffler and the underhood muffler 100 according to the present invention.

Figure 10 shows another graph representing curves for the overall sound pressure levels at the exhaust orifice in a 4-Cylinder diesel engine drawn against the engine speed (in rpm) for the baseline (conventional) muffler and the underhood muffler 100 according to the present invention.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows a perspective view of an embodiment of the present invention as an elliptical underhood muffler 100. The muffler 100 includes the main chamber made of 1 mm to 1.5 mm thick, preferably 1.2 mm thick mild steel sheet with dimensions ? D x L, wherein both length L and diameter D are in a range of 180 ? 30 mm, preferably 200 to 210 mm. The inlet tube diameter d1 and outlet tube diameter d2 are in a range of 40 to 50 mm, preferably about 45 mm. The underhood muffler 100 is configured as an elliptical muffler of about 3 to 4 liters volume, preferably about 3.6 liters, which consists of three (3) sub-chambers configured by means of by four (3) baffle plates (Fig. 2). The volume for each sub-chamber has been optimized to tune to a particular band of frequency. The volume of the muffler is also increasing progressively till the exhaust gas is allowed to expand in the fourth largest volume chamber. Accordingly, first sub-chamber has about 15% less volume than the volume of second sub-chamber. The second sub-chamber has about 20% less volume than the third sub-chamber. Finally, the third sub-chamber has about 25% less volume than the fourth largest volume chamber. This way, the fourth chamber has the largest volume of about 1 to 1.2 liters and both inlet and outlet pipes open into this largest chamber. This chamber is responsible for better transmission loss (TL) for high frequency waves. One more chamber with smallest volume is configured between the third baffle plate and the closed end plate of the main chamber by means of a perforated baffle plate disposed between them.

Figure 2 shows a detailed perspective view of the underhood muffler of Fig. 1. An elliptical apertured end plate with holes for the passage of the Inlet tube 110 has an inlet 112 and outlet tube 120 having an outlet 122, both tubes being fixed substantially parallel to each other protruding out of the first apertured end plate 130. The other end of the muffler 100 is closed by the elliptical closed end plate 180. There are four mild steel elliptical baffle plates 140, 150, 160 and 170, e.g. of about 1 mm to 2 mm, preferably 1.5 mm thickness, fixed between the elliptical apertured and closed end plates 130 and 180 respectively to configure three sub-chambers 135, 145, 155 and the largest volume chamber 165 and the smallest volume chamber 175 respectively. For example, in a typical embodiment of muffler 100, the volumes of the first, second, third, fourth and fifth chambers are 0.61 L, 0.70 L, 0.85 L, 1.07 L and 0.37 L respectively. The inlet or entry side end of the inlet tube 110 protrudes out of the apertured end plate 130 and the inlet tube 110 extends through the openings provided in the baffles plates 140, 150 and 160 respectively and its other exit or outlet end protrudes into the largest volume chamber 165. Similarly, the outlet side end of the outlet tube 120 protrudes out of the apertured end plate 130 and the outlet tube 120 also extends through the openings provided in the baffles plates 140 and 150 respectively; however it other end ends in the opening provided in the baffle plate 160 opening into the largest chamber 165. In addition, the inlet tube 110 is provided with circumferential holes 114 between the apertured end plate 130 and the third baffle plate 160. According to this embodiment of the invention, the first 135, second 145 and third sub-chambers 155 collectively facilitate in tuning the mid-frequency range from 250Hz to 600Hz. These three sub-chambers 135, 145, 155 are packed with glass wool with a packing density of about 200 gm/L. The fourth chamber 165 has the largest volume and both the inlet tube 110 and outlet tube 120 is opening into this chamber. This chamber is responsible for better transmission loss for higher range of frequency. The fifth chamber is the smallest volume chamber configured to reduce heating issues of the second end plate 180 and tuned to higher frequency with the help of perforations 172 provided on the perforated baffle plate 170 of, e.g. 1 mm to 2 mm, preferably 1.5 mm thickness. This smallest volume chamber 175 is also packed with ADVENTEX Glass wool. The size of the perforations 172 is suitably optimized to achieve the desired acoustic impedance for better performance of the muffler 100. The Inlet pipe 110 is drilled with holes uniformly distributed over its circumference to achieve maximum impedance to the sound wave though the holes 114 and the sound waves are allowed to impinge into the initial volumes of the chambers 135, 145 and 155. The exhaust gases are entering through the opening 112 provided on the inlet pipe 110 and exhaust gas flowing through the holes 114 provided on the inlet pipe 110 as well as out of the other end of inlet tube protruding into the largest chamber 165.

Figure 3 shows the elliptical apertured end plate 130 and closed end plate 180 as well as the baffles plates 140, 150, 160 and perorated baffle plate 170 disposed between the third baffle plate 160 and the closed end 180 of the main chamber. All the plates except the perforated baffle plate 170 and the closed end plate 180 forming the smallest chamber 175 are provided with two openings each (131, 132; 141, 142; 151, 152; 161, 162) for the passage and/or fixing of the inlet tube 110 and outlet tube 120. The perforated baffle plate 170 is provided with perforations 172 in order to reduce heating issues with the end plate 180 and for tuning high frequency waves by means of these perforations 172. The perforations 172 are optimized to achieve the targeted acoustic impedance to sound waves for improving the muffler performance.

Figure 4 shows a schematic relationship for any muffler chamber for arriving at the optimized configuration of each muffler chamber. The resonance frequency has a significant effect on the transmission loss (TL) of any hollow cavity, e.g. muffler chambers 135, 145, 155, 165, 175. This relationship is expressed as under:

wherein,
f = Resonance frequency,
v = Velocity of exhaust gas exiting from the chamber,
A = Area of opening port,
V = Volume of the chamber, and
l = Length of the opening port.

In other words,

fresonance ? __________Area of Opening Port___________
[Volume of Chamber] [Length of Opening Port]

The larger area of the opening port facilitates a higher frequency, because the exhaust gas can enter and exit the chamber faster. Further, a larger chamber volume also leads to a lower frequency, because more exhaust gas needs to move out to relieve a predetermined excess pressure. Finally, the length of the opening port, i.e. a longer neck thereof facilitates in achieving a lower frequency, because more resistance is offered to the exhaust gas movement into and out of the chamber.

Figure 5 shows the typical behavior of exhaust gases entering through the holes 10 provided on the surface of the inlet pipe of the muffler. The perforations offer impedance to the high and low frequency sound waves. These holes actually expose the engine bore up to the outside air or the atmosphere. Thus, they shorten the effective length of the sound duct. The acoustic wave is reflected at or near this point, because the holes provide, e.g. an acoustical 'short circuit' to the outside air. However, this phenomenon is more complicated for high frequencies. The air in and near the holes has some mass, which needs to be accelerated for passing the sound wave through these holes. In fact, air must be accelerated backwards and forwards in order for the waves to radiate out.

It is known that the required acceleration (all other things being equal) increases as the square of the frequency. So, there is little time in half a cycle to get this air mass moving for a high frequency wave. Therefore, the high frequency waves are impeded by the air present in the hole, so it does not 'appear open enough' to these high frequency waves as it appears to the low frequency waves. The low frequency waves 20 are reflected at the first open hole, but high frequency waves 30 travel further and sufficiently high frequency waves travel down the inlet tube past the open holes. Therefore, an array of open tone holes act as a high pass filter, which allows high frequency wave to pass therethrough, but rejects the low frequency wave therethrough. Further, the cut-off frequency (fc) depends on the geometry.

However, there is an approximate and simple equation, which can be used to estimates it, as given below:

fc = 0.11 (b/a)v/(s.t)½
wherein,
b = radius of a hole,
a = radius of the pipe diameter,
v = speed of sound,
s = half the typical spacing between holes, and
t = typical effective length of the hole, including the end effects.

It also has glass wool with a packing density of 200 gm/L, which helps in improving the TL in higher frequency range. The glass-wool quantity is also optimized in-order to achieve an improved sound quality along with the cost saving associated therewith.

Figure 6 shows a graphical representation of the curve of transmission loss (TL) versus frequency (f) both for a baseline (conventional) muffler and the embodiment of the elliptical muffler 100 according to the invention. It is quite evident from this graph that the elliptical muffler 100 offers a substantially higher transmission loss than for conventional muffler at all frequencies except for frequencies between 200 to 240 Hz. Moreover, certain peaks of transmission loss are visible at the frequency of 600 Hz, 1200 Hz, 1350 Hz and 1935 Hz respectively, which are effectively used for optimizing the transmission loss for configuring different chambers of elliptical muffler 100. Higher the transmission loss (TL), better the NVH performance of the muffler.

Figure 7 shows another graph representing the comparison of the brake specific fuel consumption (BSFC) drawn against the frequency (f) for baseline (conventional) muffler and the elliptical muffler 100 according to the invention. However, there is not any significant improvement seen in the elliptical muffler as compared to the conventional muffler. The very little improvement is seen in the higher frequency range of 1650 to 2100 Hz only.

Figure 8 shows a graph representing the curves for the sound pressure levels [in dB(A)] at the exhaust orifice [for the second order engine firing frequency] in a 4-Cylinder diesel engine drawn against the engine speed (in rpm) for comparing the performances of the baseline (conventional) muffler and the elliptical muffler in accordance with the present invention. It is evident from the graph that the elliptical muffler of the invention performs poorer till reaching the engine speed of about 1250 rpm, but the sound pressure level are substantially lower than the conventional muffler for the engine speeds above 1250 rpm.

Figure 9 shows another graph representing the curves for the sound pressure levels [in dB(A)] at the exhaust orifice [for the fourth order engine firing frequency] in a 4-Cylinder diesel engine drawn against the engine speed (in rpm) for comparing the performances of the baseline (conventional) muffler and the elliptical muffler in accordance with the present invention. . It is evident from the graph that the elliptical muffler of the invention performs poorer till reaching the engine speed of about 1375 rpm, but the sound pressure level are substantially lower than the conventional muffler for the engine speeds above 1375 rpm.

Figure 10 shows another graph representing curves for the overall sound pressure levels [in dB(A)] at the exhaust orifice in a 4-Cylinder diesel engine drawn against the engine speed (in rpm) for comparing the performances of the baseline (conventional) muffler and the elliptical muffler in accordance with the present invention. . It is evident from the graph that the overall performance of the elliptical muffler of the invention is much better than the conventional muffler, because sound pressure levels are substantially lower than the conventional muffler for the entire range of engine speeds.

TESTS CARRIED OUT & RESULTS THEREOF

According to SABS 0205* standard covering the measurement of noise emitted by motor vehicles in motion, the following values were obtained:

Bystander Noise dB(A)
SABS noise limit* 89
Engineering limit 87
Base (conventional) Muffler 87.7
Elliptical Embodiment of the Muffler 84.7

In addition, various tests were conducted both for the conventional (baseline) muffler and the elliptical muffler 100 in accordance with the present invention, particularly at the following conditions:

a) Background noise level 38.2 dB(A),
b) Low idle at 815 rpm,
c) High idle at 2440 rpm, and
d) Maximum Bystanders noise 87.7 dB(A).

The obtained results on comparing the following characteristics for the conventional and elliptical muffler 100 are as under:

Baseline (Conventional) Muffler Elliptical Embodiment of the Muffler
Gear Silencer facing towards the microphone
Noise dB(A) Silencer facing away from the microphone Noise dB(A) Gear Silencer facing towards the microphone
Noise dB(A) Silencer facing away from the microphone Noise dB(A)
M4 85.2 83.5 M4 82.9 82.9
M5 86.8 84.4 M5 84.4 83.4
H1 84.7 83.2 H1 82.7 82.6
H2 85.0 83.6 H2 82.6 82.8
H3 87.7 84.0 H3 83.9 83.1
H4 87.0 83.8 H4 84.7 83.5
H5 84.3 81.1 H5 83.0 82.8

Further, the backpressure values were also compared for the baseline (conventional) and embodiment of the elliptical muffler according to the present invention, for which the results are as under:

Backpressure value Baseline (Conventional) Muffler Elliptical (Inventive) Muffler Design Limits Fixed at:
Simulation 72 mbar 67 mbar 90 mbar
Test 49 mbar 45 mbar 90 mbar

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

- Progressive volume increase in chambers helps in achieving better Noise reduction.

- Inlet and outlet pipe opening configured in same chamber in accordance with the invention facilitates in obtaining a lower backpressure.

- Slightly improved fuel efficiency as compared to the conventional muffler.

- Exhaust gas expansion in second last chamber to prevent the End plate heating issues by direct impact of high temperature exhaust gases

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 in order 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.

Although, only the preferred embodiments have been described herein, the skilled person in the art would readily recognize to apply these embodiments with any modification possible within the spirit and scope of the present invention as described in this specification.

Therefore, innumerable changes, variations, modifications, alterations may be made and/or integrations in terms of materials and method used may be devised to configure, manufacture and assemble various constituents, components, subassemblies and assemblies according to their size, shapes, orientations and interrelationships.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

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.