Gas flow sound attenuation device
The gas flow sound attenuation device includes a number of variations each having at least one pressure pulse reflecting chamber, i.e., a Helmholtz chamber, installed in axial alignment with the upstream gas flow. Gas flow is transferred laterally externally to the chamber, with the single opening of the chamber receiving substantially all incoming pressure pulse energy to maximize the reflection and canceling of those pulses back into the upstream duct. The device may incorporate any practicable number of chambers, so long as each has at least some length of upstream pipe or duct axially aligned with the chamber opening. The chambers may have any practicable shape and/or may include internal baffling. The device may be applied to any gas flow system, e.g., heating, ventilation, and air conditioning systems, but is particularly effective in reducing the sound output of internal combustion engine exhaust systems.
1. Field of the Invention
The present invention relates generally to systems and devices for reducing sound emissions due to the dynamic flow of gases through ducts, pipes, and the like, such as in exhaust and intake systems for internal combustion engines, heating, air conditioning, and ventilation systems, etc. More specifically, the present invention relates to a gas flow sound attenuation device having at least one Helmholtz chamber, i.e., a resonant chamber, having only a single opening axially aligned with the upstream gas flow and pressure pulses, rather than axially offset therefrom.
2. Description of the Related Art
The production of audible sound or noise from a moving gas stream is a well-known phenomenon. The effect can make itself known even where no combustion occurs, with the effect being utilized for the production of sound in all wind instruments in the musical field. However, in other fields it may be more desirable to reduce or cancel the sound or noise produced by the moving gas stream, e.g., in air intake systems, heating, air conditioning, and ventilation systems, etc. This is particularly true where additional sound is generated by combustion of a fuel with the gas, as in an internal combustion engine.
Conventionally, sound produced by internal combustion engines is controlled by means of mufflers and resonators, with some sound reducing effect perhaps being due to additional componentry, such as turbochargers and catalytic converters, installed in the exhaust system. Mufflers are the primary means for reducing sound emissions from internal combustion engines, with resonators primarily employed to cancel certain limited frequencies. Other components have relatively little effect. A great deal of research and development has gone into muffler technology over the years, but essentially all mufflers incorporate a labyrinth pathway through which the gas must flow, with a corresponding loss of energy, and therefore sound, in the gas flow as it passes through the muffler.
The corresponding increase in static pressure (back pressure) as the gas loses dynamic pressure (velocity) through the muffler is an undesirable side effect of muffler technology. As a result, various alternatives have been applied to mufflers, exhaust systems, and gas flow paths in general, in attempts to reduce the sound level while avoiding a corresponding increase in back pressure. Attempts have been made to reduce back pressure while simultaneously reducing sound output by means of a Helmholtz chamber, i.e., a chamber having a single opening therein. The chamber is joined to the gas passageway, with the theory being that pressure pulses in the system will travel into the chamber and will be reflected back out the single opening of the chamber to cancel incoming pressure pulses.
Obviously, a chamber having only a single opening must allow for gas flow therearound or thereby, as there can be no net flow through a chamber having only a single opening. As a result, the prior art has laterally offset such Helmholtz chambers from the primary gas pathway, with the gas tending to flow past the opening to the chamber. While this optimizes the gas flow, this axial offset of the chamber results in only a relatively small portion of the pressure pulse being reflected from the lip of the offset opening of the chamber. This may result in the sound actually being amplified at certain frequencies, and, in fact, this is the general principle used in all woodwind musical instruments and pipe organs, albeit using open airflow paths. A more specific example of the resonance caused by a Helmholtz chamber having an opening axially offset to the airflow path is found in the simple concept of blowing across the open mouth of a bottle, with the production of sound from this action being well known.
Thus, a gas flow sound attenuation device solving the aforementioned problems is desired.
SUMMARY OF THE INVENTIONThe gas flow sound attenuation device is exemplified by various embodiments, which each include at least one Helmholtz chamber having its single opening axially aligned with the upstream gas flow, with the gas flow path being deflected or angled laterally from this alignment to allow gas to flow around the chamber. In this manner the chamber directly receives all incoming pressure pulses, or in other words all sound, emanating from upstream in the pipe or duct and reflects those pressure pulses directly back upstream into the incoming pulses. This serves to cancel at least some of the pressure pulses as they travel through the pipe, thereby reducing the sound output of the system, with the gas flow continuing through a lateral branch to the side of the chamber to exit downstream with no appreciable increase in back pressure.
The gas flow sound attenuation device may be applied to internal combustion engine exhaust systems and other systems where no combustion occurs, e.g., heating, ventilating, and air conditioning duct systems, etc. The chamber(s) may be formed of relatively low temperature materials, even when used in engine exhaust systems, as it has been found in testing that the temperatures of the relatively static gases that collect within the chamber are relatively low in comparison to the dynamic gas flow through the pipe. The device may include one or more chambers, so long as each is axially aligned with the immediate upstream flow path so that pressure pulses traveling down that path will pass directly into the chamber, rather than having the majority of the pulse energy bypass a laterally displaced chamber. The chamber or chambers may be a relatively simple cylindrical canister or canisters, or may incorporate various shapes to alter the effects on the pressure pulses. The chamber(s) may be devoid of internal structure, or may include internal baffling or the like in order to alter the effects.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSThe present invention comprises various embodiments of a gas flow sound attenuation device, wherein a pressure pulse reflecting chamber having a single opening therein is installed in axial alignment with the upstream pipe or duct in order to accept substantially all of the incoming pressure pulse or sound energy from the upstream direction. In each case, the chamber has a larger volume than the inlet tube or pipe, thereby defining a Helmholtz resonant chamber. The device is applicable to virtually any system where gases are moved through a pipe, duct, tube, or other closed passageway, but is particularly useful in quieting the sound output from internal combustion engine exhaust systems.
An elongate exhaust gas flow passageway 120 has an inlet end 122 extending from the downstream end of the muffler 118, and an opposite outlet end 124. The passageway 120 includes an upstream portion 126 disposed between its inlet end 122 and its outlet end 124, and a stub portion 128, which is axially aligned with the upstream portion 126. The stub portion 128 includes an inlet end 130 in gas flow communication with the upstream portion 126, and an opposite outlet portion 132. The downstream portion 134 of the passageway 120 is axially offset from the upstream portion 126 thereof, with the outlet end 124 of the passageway extending from the downstream portion 134 thereof.
A sound canceling chamber 136 has a single opening 138 in communication with the outlet end 132 of the stub 128 and upstream portion 126 of the passageway 120, with the chamber 136 and its opening 138 being in axial alignment with the stub 128 and upstream portion 126 of the passageway 120, as indicated by the axial centerline A. This allows the chamber 136 to receive incoming pressure pulses P1, and reflect those pulses back up the upstream portion 126 of the passageway 120 as reflected pulses RP1. The reflected pulses RP1 tend to cancel the downstream traveling pulses P1, thus reducing the sound output of the exhaust system 110. Exhaust gases are free to travel through and leave the system by means of the axially offset downstream portion 134 of the passage 120, as indicated by the exhaust gas arrows G1 in
Each passageway further includes a stub portion, respectively 328a and 328b, which is axially aligned with its respective upstream portion 326a, 326b. The stub portions each include an inlet end, respectively 330a and 330b, in gas flow communication with the respective upstream portions 326a, 326b, and an opposite outlet portion, respectively 332a and 332b. The downstream portions 334a, 334b of the passageways 320a, 320b are axially offset from the respective upstream portions 326a, 326b thereof, with the outlet ends 324a, 324b of the passageways extending from their respective downstream portions 334a and 334b thereof.
Each of the passageway stub portion ends 332a, 332b has a sound canceling chamber, respectively 336a and 336b, extending therefrom. Each chamber has a single opening, respectively 338a and 338b, in communication with the outlet end 332a, 332b of the respective stub 328a, 328b and upstream portion 326a, 326b of the respective passageway 320a, 320b. Each chamber 336a, 336b and respective opening 338a, 338b is in axial alignment with the respective stub 328a, 328b and upstream portions 326a, 326b of the passageways 320a, 320b, as indicated by the axial centerlines A. This configuration allows each of the chambers 336a, 336b to receive incoming pressure pulses from their respective axially aligned gas flow passages 320a and 320b and reflect those pulses back up the respective upstream portion 326a, 326b of the passageways, generally as described for the single sound canceling chamber embodiment of
The passageway 420 further includes a stub portion 428, which is axially aligned with the upstream portion 426. The stub portion includes an inlet end 430 in gas flow communication with the upstream portion 426, and an opposite outlet portion 432. The downstream portions 434a and 434b of the passageways 420a and 420b are axially offset from the upstream portion 426 thereof, with the outlet ends 424a and 424b of the passageways extending from the respective downstream portions 434a and 434b thereof.
The passageway stub portion end 432 has a sound-canceling chamber 436 extending therefrom. The chamber has a single opening 438, in communication with the outlet end 432 of the stub 428 and upstream portion 426 of the passageway 420. The chamber 436 and its opening 438 are in axial alignment with the stub 428 and upstream portion 426 of the passageway 420, as indicated by the axial centerline A. This configuration allows the chamber 436 to receive incoming pressure pulses from the axially aligned gas flow passages 420 and reflect those pulses back up the respective upstream portion 426 of the passageway, generally as described for the single sound canceling chamber embodiment of
Each passageway further includes a stub portion, respectively 528a through 528c, which is axially aligned with its respective upstream portion 526a through 526c. A further stub portion 528 is axially aligned with the upstream pipe 514. The stub portions each include an inlet end, respectively 530 through 530c, in gas flow communication with their respective upstream portions 514 and 526a through 526c, and an opposite outlet portion, respectively 532 through 532c. The downstream portions of the system, i.e., passageway 520a stemming from pipe 514; passage 520b stemming from passage 520a; passage 520c stemming from passage 520b; and outlet passage 534 stemming from passage 520c, are axially offset from the respective upstream portions 514 and 526a through 526c thereof, with the outlet ends 524a through 524c of the passageways extending from their respective downstream portions 534a through 534c thereof.
Each of the passageway stub portion ends 532 through 532c has a sound canceling chamber, respectively 536 through 536c, extending therefrom. Each chamber has a single opening, respectively 538 through 538c, in communication with the outlet end 532 through 532c of the respective stub 528 through 528c and upstream portion 514 and 526a through 526c of the respective passageway. Each chamber 536 through 536c and respective opening 538 through 538c is in axial alignment with the respective stub 528 through 528c and upstream portions 514 and 526a through 526c of their passageways, as indicated by the axial centerlines A. This configuration allows each of the chambers 536 through 536c to receive incoming pressure pulses from their respective axially aligned gas flow passages 514 and 520a through 520c and reflect those pulses back up the respective upstream portion 514 and 526a through 526c of the passageways, generally as described for the single sound canceling chamber embodiment of
The sound canceling chamber 636 has a single opening 638 in communication with the outlet end 632 of the stub 628 and upstream portion 626 of the passageway 620, with the chamber 636 and its opening 638 being in axial alignment with the stub 628 and upstream portion 626 of the passageway 620, as indicated by the axial centerline A. This allows the chamber 636 to receive incoming pressure pulses and reflect those pulses back up the upstream portion 626 of the passageway 620, generally as described for the embodiment 110 of
However, the sound attenuating or canceling chamber 636 has a different configuration than the corresponding chambers 136 through 536 of the embodiments of
The sound canceling chamber 736 has a single opening 738 in communication with the outlet end 732 of the stub 728 and upstream portion 726 of the passageway 720, with the chamber 736 and its opening 738 being in axial alignment with the stub 728 and upstream portion 726 of the passageway 720, as indicated by the axial centerline A. This allows the chamber 736 to receive incoming pressure pulses and reflect those pulses back up the upstream portion 726 of the passageway 720, generally as described for the embodiment 110 of
However, the sound attenuating or canceling chamber 736 has a different configuration than the corresponding chambers 136 through 636 of the embodiments of
It should also be noted that the opening end portion 738 of the sound canceling chamber 736 embodiment of
The sound canceling chamber 836 has a single opening 838 in communication with the outlet end 832 of the stub 828 and upstream portion 826 of the passageway 820, with the chamber 836 and its opening 838 being in axial alignment with the stub 828 and upstream portion 826 of the passageway 820, as indicated by the axial centerline A. This allows the chamber 836 to receive incoming pressure pulses and reflect those pulses back up the upstream portion 826 of the passageway 820, generally as described for the embodiment 110 of
However, the sound attenuating or canceling chamber 836 has a different configuration than the corresponding chambers 136 through 736 of the embodiments of
It should be noted that the various sound canceling or attenuating chambers in the gas flow sound attenuation devices of the present invention need not have a uniform external shape. In some instances, a chamber having an irregular or non-uniform configuration, particularly such an internal configuration, may prove superior in canceling certain frequencies of sound.
The chamber 936 of
The chamber 1036 of
Any of the sound canceling chambers in the gas flow sound attenuation devices of the present invention may also be combined and/or enclosed within an external shell, if so desired, in order to provide a compact unit. This is particularly true of multiple chamber embodiments, such as that exemplified in
The entire above-described assembly is enclosed within an external shell 1148, with only the upstream or entry pipe 1114 and the opposite downstream passage or pipe 1134 and its outlet 1124 extending from the otherwise closed shell 1148. The various pipes and passages contained within the enclosure 1148 may include additional sound attenuation means if so desired, e.g., baffling, glass packing, etc., as desired. Alternatively, additional flow paths may be provided outwardly from the various passages within the device to allow gas to flow through the remainder of the shell volume, if so desired.
The various pipes and passageways of the gas flow sound attenuation devices may include additional sound attenuating means therein, as noted above. It is also possible to include internal baffling within any of the sound attenuating chambers of the gas flow sound attenuation devices.
The chamber 1236 of
The present inventors have performed a series of tests upon different vehicles, in order to quantify the reduction in sound level provided by the present gas flow sound attenuation device. Tables I-IV, provided below, clearly indicate the sound level reduction provided by the present invention.
In the above tests, the gas flow sound attenuation device tested with the Cadillac Seville is similar in configuration to that shown in
In the above Tables, the “Base” temperature refers to the temperature of the exhaust pipe temperature in the flow-through portion, upstream of the gas flow sound attenuation device. The final column in the temperature Tables refers to the temperature of the canister when installed for testing in the exhaust system. Ambient temperature during testing averaged about 78° F. The quality of the sound was affected positively by the gas flow sound attenuation devices, although this could not be quantified. Some vehicles produced a “burbling” sound, consistent with varying pressure pulsations, before the installation of the sound attenuation devices. The “burbling” sound was reduced dramatically or canceled completely by the installation of the gas flow sound attenuation devices during testing.
The gas flow sound attenuation device can be constructed of any material, or any combination of materials, suitable to its application.
In conclusion, the gas flow sound attenuation device, in its various embodiments, provides a means of canceling or greatly reducing the sound output of a volume of gas flowing through a pipe or duct without a corresponding increase in backpressure. While the gas flow sound attenuation device is particularly well suited for use in automotive and other internal combustion engine exhaust systems, it is also well suited for use in quieting heating, ventilating, and air conditioning systems where there are no combustion gases. It should be noted that other variations are possible, e.g., the addition of sound absorption material (glass fiber batts, etc.) in the canister or chamber. The device may also be modified by the installation of a diverter valve at the mouth or opening of the chamber to allow pressure pulses to enter the chamber or to close off the chamber to such pulses, thereby altering the sound output of the system accordingly. Electronic noise or sound canceling means may be installed in combination with the device, thereby resulting in even further gains in sound cancellation. Accordingly, the gas flow sound attenuation device will provide improved efficiencies in exhaust systems and corresponding increases in fuel efficiency when used in motor vehicle installations.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
Claims
1. A gas flow sound attenuation device, comprising:
- at least one elongate gas flow passageway having: an inlet end; an outlet end opposite the inlet end; at least one upstream portion disposed between the inlet end and the outlet end; a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; and at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and
- a sound-canceling chamber having a single opening defined therein, the single opening connected to and communicating with the outlet end of the stub portion and in axial alignment therewith.
2. The gas flow sound attenuation device according to claim 1, wherein said at least one elongate passageway comprises an exhaust gas flow passageway and said sound canceling chamber comprises an exhaust sound canceling chamber.
3. The gas flow sound attenuation device according to claim 1, wherein said at least one elongate gas flow passageway comprises a plurality of elongate gas flow passageways and said sound canceling chamber comprises a plurality of chambers, each of the chambers being connected to a corresponding one of the gas flow passageways.
4. The gas flow sound attenuation device according to claim 3, further including an external shell surrounding all of the gas flow passageways and sound canceling chambers, the shell having an inlet and an outlet communicating with the gas flow passageways.
5. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has a plurality of branches.
6. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the single opening defined therein.
7. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has a polyhedral external configuration.
8. The gas flow sound attenuation device according to claim 1, wherein said sound canceling chamber has at least one internal baffle disposed therein.
9. An internal combustion engine exhaust gas flow sound attenuation device, comprising:
- at least one elongate exhaust gas flow passageway having: an inlet end; an outlet end opposite the inlet end; at least one upstream portion disposed between the inlet end and the outlet end; a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; and at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and
- an exhaust sound-canceling chamber having a single opening defined therein, the single opening connected to and communicating with the outlet end of the stub portion and in axial alignment therewith.
10. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said at least one elongate exhaust gas flow passageway comprises a plurality of elongate exhaust gas flow passageways and said exhaust sound canceling chamber comprises a plurality of chambers, each of the chambers being connected to a corresponding one of the exhaust gas flow passageways.
11. The internal combustion engine exhaust gas flow sound attenuation device according to claim 10, further including an external shell surrounding all of the exhaust gas flow passageways and exhaust sound canceling chambers, the shell further having an inlet and an outlet each communicating with the exhaust gas flow passageways.
12. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has a plurality of branches.
13. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the opening thereof.
14. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has a polyhedral external configuration.
15. The internal combustion engine exhaust gas flow sound attenuation device according to claim 9, wherein said exhaust sound canceling chamber has at least one internal baffle disposed therein.
16. An internal combustion engine exhaust gas flow sound attenuation device, comprising:
- a plurality of elongate gas flow passageways, each of the passageways having: an inlet end; an outlet end opposite the inlet end; at least one upstream portion disposed between the inlet end and the outlet end; a stub portion axially aligned with the upstream portion, the stub portion having an inlet end communicating with the upstream portion and an outlet end opposite the inlet end; at least one downstream portion axially offset from the upstream portion, the outlet end extending from the downstream portion; and an exhaust sound canceling chamber having a single opening therein, the single opening connected to and communicating with the outlet end of each stub portion and in axial alignment therewith; and
- an external shell surrounding all of the gas flow passageways and sound canceling chambers, the shell having an inlet and an outlet each communicating with the gas flow passageways.
17. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has a plurality of branches.
18. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has a cross-sectional area larger than the cross-sectional area of the opening thereof.
19. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has a polyhedral external configuration.
20. The internal combustion engine exhaust gas flow sound attenuation device according to claim 16, wherein at least one said exhaust sound canceling chamber has at least one internal baffle disposed therein.
Type: Application
Filed: Oct 23, 2006
Publication Date: Apr 24, 2008
Inventors: Gregory M. Marocco (Montville, NJ), Gregory Colletti (Belvidere, NJ)
Application Number: 11/584,636