AU2021104411A4

AU2021104411A4 - Double expansion chamber reactive muffler

Info

Publication number: AU2021104411A4
Application number: AU2021104411A
Authority: AU
Inventors: Ravindra Ingle; Mahesh Kulkarni
Original assignee: Vishwanath Karad Mit World Peace University
Current assignee: Vishwanath Karad Mit World Peace University
Priority date: 2021-05-25
Filing date: 2021-07-21
Publication date: 2022-05-26
Anticipated expiration: 2029-07-21

Abstract

DOUBLE EXPANSION CHAMBER REACTIVE MUFFLER Disclosed is a double expansion chamber reactive muffler (100) for maximizing the transmission loss in a specific frequency range within the full operational range for the internal combustion 5 engine. The muffler (100) comprises a two chambers (10, 20) having identical length and diameter and connected with a connecting tube (50) extended into the second chamber (20). A baffle (30) with a choke tube (40) is incorporated in a first chamber (10) while an exhaust gas outlet tube (60) extends inside the second chamber (20). The distance (M) of the baffle (40), the lengths (LI, L2) of the two parts of the choke tube (30) on either side of the baffle (40) and the lengths (L3, L4) of 0 the extended inlet and outlet tubes of the second chamber (20) are optimized in a way to give maximum transmission loss in the specific frequency range. Figure 2 1 1/2 100 K4050 30 4so60 A B 1 20 Figure 1 100 x y 5 A 1o B sei 20 610 DI 230 MN L L4 Figure 2

Description

1/2

100

K4050 30 4so60

A B

1 20

Figure 1 100

x y

5 A 1o B sei 20 610

DI 230

MN L L4

Figure 2

TITLE DOUBLE EXPANSION CHAMBER REACTIVE MUFFLER FIELD OF THE INVENTION:

The present invention generally relates to exhaust system mufflers to attenuate internal combustion engine noise and more particularly to double expansion chamber reactive mufflers for maximizing the transmission loss in the specific frequency range within a full frequency range (1-1600 Hz) of operation for the internal combustion engine.

BACKGROUND OF THE INVENTION:

When internal combustion takes place, the engine expels exhaust gasses in the form of high pressure pulses. These high pressure pulses create very powerful sound waves. Sound waves propagating along a duct can be attenuated using either an absorptive or a reactive muffler. Absorptive muffler uses sound absorbing material to absorb energy from the acoustic in the wave, when it propagates through the muffler, while reactive muffler works on impedance mismatch principle. Muffler is a device used for reducing the amount of noise produced by the exhaust of an internal combustion engine. The acoustic analysis of exhaust muffler is characterized by numerous parameters like insertion Loss (IL), Transmission Loss (TL). The frequently used parameter to evaluate the sound radiation characteristics of muffler is Transmission loss (TL). Transmission Loss is defined as difference between power incident on muffler proper and power transmitted downstream into an-echoic termination. The transmission loss is independent of source and it presumes an-echoic termination at tail pipe. Exhaust noise from engines is one of the components of noise pollution to the environment. Exhaust systems are developed to attenuate noise meeting required dB levels and sound quality, emissions based on environment norms. Noise levels of more than 80 dB are injurious for human beings. Design of mufflers is a complex function that affects noise characteristics, emission and fuel efficiency of engine. Hence muffler design becomes important for noise reduction. Hence to reduce noise from internal combustion engines they are equipped with an important noise control element known as silencer or exhaust muffler which reduces the acoustic pulse generated by the combustion processes. The internal changes in the geometry of the muffler are made to develop the impedance mismatch for maximizing the transmission loss.

A very meagre study on double expansion chamber muffler for improvement in transmission loss in specific frequency range of 650 Hz-850 Hz is available. The improvement in Transmission Loss in specific frequency range of 650 Hz-850 Hz is required for muffler of particular configuration of engine which is used for diesel generator set available in the market. This is because these engines shows maximum sound pressure levels in their exhaust at specified frequency range of 650 Hz-850 Hz, which needs to be attenuated. Prior art patents do not disclose the design of muffler for improvement in transmission loss in frequency range of650 Hz-850 Hz.

Accordingly, there exists a need to develop a double expansion chamber reactive muffler that for improvement in transmission loss in a specific frequency range and overcome the drawbacks in the prior art.

OBJECTS OF THE INVENTION:

An object of the present invention is to provide a double expansion chamber reactive muffler that will improve the transmission loss in a specific frequency range within a full frequency range (1-1600 Hz) of operation for the internal combustion engine.

SUMMARY OF THE INVENTION

The present invention discloses a double expansion chamber reactive muffler for an internal combustion engine, for maximizing the transmission loss at a specific frequency range within a full frequency range (1-1600 Hz) of operation for the internal combustion engine. The double expansion chamber reactive muffler comprises a first chamber and a second chamber connected with a connecting tube.

The first chamber is having cylindrical shape defined by two flat ends and a curved surface. The first chamber is fitted with an exhaust gas inlet on the first flat end for providing a passage therein for gas exhausted from the internal combustion engine. A baffle is internally fitted in the first chamber at a predefined distance (M) from the first flat end thereof. The baffle is centrally fitted with a choke tube of a predefined diameter, wherein the predefined distance (M) is one third of the total length (X) of the first chamber and the baffle divides the choke tube in two parts having predefined lengths Li and L2. The second chamber is identical in length and diameter with the first chamber. The second chamber is having a cylindrical shape defined by two flat ends and a curved surface. The second chamber is connected to the first chamber through the connecting tube having one end fitted to the second flat end of the first chamber and a part having a predefined lengthL3 extending through the first flat end into the second chamber. An exhaust gas outlet tube is fitted to the second flat end of the second chamber with one end extending outside the second chamber and a part having a predefined length L4 extending inside the second chamber. In an embodiment, the diameters of the choke tube, the connecting tube and the exhaust gas outlet tube are same. The distance (M) and the lengths LI, L2, L3 and L4 are optimized to give maximum transmission loss for the specific frequency range within a full frequency range (1-1600 Hz) of operation for the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS:

The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein

Figure 1 shows a schematic view of a double expansion chamber reactive muffler, in accordance with the invention;

Figure 2 shows a schematic view of a double expansion chamber reactive muffler depicting lengths of parts of the muffler, in accordance with the invention; and

Figure 3 shows graph of transmission loss for frequency range of 650-850 Hz, for various placements of baffle with choke tube, in accordance with an exemplary embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS:

The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiments.

The present invention provides a double expansion chamber reactive muffler having baffle with choke tube incorporated in a first chamber and an extended inlet and an extended outlet tubes incorporated in a second chamber of double expansion chamber reactive muffler with external connecting tube, to increase the transmission loss at specific frequency range.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description and in the table below.

Table:

Ref No: Component Ref No: Component

5 Exhaust gas inlet 40 Choke tube 10 First chamber 50 Connecting tube 20 Second chamber 60 Exhaust gas outlet 30 Baffle

Referring to the figures 1 and 2, a double expansion chamber reactive muffler (100) (hereinafter referred to as "the muffler (100)") with external connecting tube, for an internal combustion engine, for increasing the transmission loss at specific frequency range, in accordance with the present invention is shown. The muffler

(100) comprises a first chamber (10) and a second chamber (20) connected with a connecting tube (50).

The first chamber (10) having a cylindrical shape defined by two flat ends (10A, 1OB) and a curved surface (1OC) is fitted with an exhaust gas inlet (5) on the first flat end (10A) for providing a passage therein for exhaust gas from the internal combustion engine. The first chamber (10) is internally fitted with a baffle (30) at a predefined distance from the first flat end (10A) thereof, with a centrally fitted choke tube (40) of a predefined diameter. Distance of the baffle (30) from the first flat end (10A), denoted by M is one third of the total length of the first chamber (10). Thus, the baffle (30) divides the first chamber (10) in two sub-chambers A and B having their lengths in a ratio of 1:2. The baffle (30) divides the choke tube (40) fitted centrally there through in two parts Li and L2.

The second chamber (20) having a cylindrical shape defined by two flat ends (20A, 20B) and a curved surface (20C) is connected to the first chamber (10) through a connecting tube (50) having one end fitted to the second flat end (10B) of the first chamber (10) and a part having a predefined length L3 extending through the first flat end (20A) into the second chamber (20). The exhaust gas outlet tube (60) is fitted to the second flat end (20B). The outlet tube (60) is having one end extending outside the second chamber (20) and a part having a predefined length L4 extending inside the second chamber (20). The lengths M, LI, L2, L3 and L4 are optimized to maximize the transmission loss at specific frequency range, using finite element method (FEM) and Taguchi method.

In another preferred embodiment, the two chambers (10, 20) are identical in length and diameter. In still another preferred embodiment, diameter of the choke tube (30), the connecting tube (50) and the exhaust gas outlet tube (60) is same. In yet another preferred embodiment, the lengths L1, L2, L3 and L4 are predefined in such a way that the transmission loss at a specific frequency range is maximum.

The baffle (40), the choke tube (30), the connecting tube (50) and the extended parts of the connecting tube (50) and the exhaust gas outlet (60) inside the second chamber provide sudden expansion and sudden contractions to the sound waves entering into through the exhaust gas inlet (5) and passing there through. These geometrical variations provide impedance mismatch resulting in attenuation of sound wave. This in turn increases the Transmission Loss of the muffler at specific frequency range. The placement of baffle (40), lengths L, L2 of the choke tube (30) and the lengths L3 and L4 of the connecting tube (50) are optimized using Taguchi Method for maximum Transmission Loss in the specific frequency range. The peculiarity of the arrangement of baffles and tubes that gives this effect is that, it gives overall broadband Transmission Loss for the muffler for specific frequency range within a full frequency range (1-1600 Hz) of operation for particular engine.

Example

The muffler (100) of the present invention will be described with more details as below by means of example. The following example is provided in order to demonstrate and further illustrate certain preferred embodiments and aspects of the present invention and are not to be construed as limiting the scope thereof.

Referring to figures 2 and 3, the transmission loss (TL) comparison for muffler (100) with external connecting tube (50) for placement variation of baffle (40) with choke tube (30) for specific frequency range (650-850 Hz) is shown. The diameter of the choke tube (30) is kept constant (i.e.44 mm) and the diameter of the first and second chamber is kept constant (i.e. 120 mm) and the position of the choke tube (30) is kept at central. It is observed that, the maximum Transmission Loss is obtained when the choke tube is at central position as compared to offset positions.

Various dimensions of the muffler (100) are as below:

Length of the first chamber (10) X 270 mm Length of the second chamber (20) Y 270 mm Diameter of the first chamber (10) D1 120 mm Diameter of the second chamber (20) DI 120 mm Diameter of the chock tube (30), the connecting tube (50) D2 44 mm and the exhaust gas outlet tube (60)

Length of the exhaust gas inlet tube outside the first P 95 mm chamber (10) Length of the exhaust gas outlet tube outside the first Q 110mm chamber (10) Length of the exhaust gas outlet tube outside the second R 95 mm chamber (20)

Here the main objective is to optimize the lengths of the extended inlets and outlets inside the chamber, to achieve the maximum Transmission Loss in the specified frequency range. The Lengths L, L2, L3 and L4 are optimized using Taguchi method of optimization.

Length of choke tube (30) in sub-chamber (A) Li 65 mm Length of choke tube (30) in sub-chamber (B) L2 105 mm Length of the part of connecting tube (50) extending into L3 110mm the second chamber (20). Length of the part of exhaust gas outlet tube (60) inside L4 95 mm the second chamber (20)

Referring to the graph shown in figure 3, the average transmission loss for the muffler (100) was observed for three different values of distance (M) between the baffle (40) and the first flat end (10A).

The blue colored curve in the graph shows that the maximum average transmission loss of 86.9 dB is observed when M is 90mm.

The red colored curve in the graph shows that the average transmission loss of for 84.3 dB is observed for M = 120 mm; and

The green colored curve in the graph shows that the average transmission loss of for 69.4 dB is observed for M = 150 mm;

Hence maximum transmission loss of 86.9 dB is observed when M is 90mm.

ADVANTAGES OF THE INVENTION:

Attenuation of sound at specific frequency ranges is achieved using the muffler (100). > Optimization of extended tube lengths saves design time. > Broadband Transmission Loss is achieved using the muffler (100).

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.

Claims

CLAIM:

1. A double expansion chamber reactive muffler (100) for an internal combustion engine, for maximizing the transmission loss at a specific frequency range within a full frequency range (1-1600 Hz) of operation for the internal combustion engine; the double expansion chamber reactive muffler (100) comprising: a first chamber (10) having cylindrical shape defined by two flat ends (10A, 1OB) and a curved surface (10C); the first chamber (10) fitted with an exhaust gas inlet (5) on the first flat end (10A) for providing a passage therein for exhaust gas from the internal combustion engine and with a baffle (30) internally fitted at a predefined distance (M) from the first flat end (10A); the baffle (40) fitted with a choke tube (40) of a predefined diameter, wherein the predefined distance (M) is one third of the total length (X) of the first chamber (10) and the baffle (30) divides the choke tube (40) in two parts having predefined lengths Li and L2; a second chamber (20) having a cylindrical shape defined by two flat ends (20A, 20B) and a curved surface (20C), the second chamber (20) connected to the first chamber (10) through a connecting tube (50) having one end fitted to the second flat end (1OB) of the first chamber (10) and a part having a predefined length L3 extending through the first flat end (20A) into the second chamber (20); and an exhaust gas outlet tube (60) fitted to the second flat end (20B) with one end extending outside the second chamber (20) and a part having a predefined length L4 extending inside the second chamber (20); wherein the predefined distance (M) and the lengths L1, L2, L3 and L4 are the lengths optimized for the maximum transmission loss for the specific frequency range.

2. The double expansion chamber reactive muffler (100) as claimed in claim 1, wherein the two chambers (10, 20) are identical in length (X) and diameter (D1).

3. The double expansion chamber reactive muffler (100) as claimed in claim 1, wherein diameter (D2) of the choke tube (30), the connecting tube (50) and the exhaust gas outlet tube (60) is same.

4. The double expansion chamber reactive muffler (100) as claimed in claim 1, wherein the choke tube (30) is centrally fitted to the baffle (40).