US20200362845A1

US20200362845A1 - Resonance free compressor inlet acoustic suppressor

Info

Publication number: US20200362845A1
Application number: US15/930,091
Authority: US
Inventors: Kwin R. Abram; Michael T. Zuroski; David J. Moenssen
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2019-05-14
Filing date: 2020-05-12
Publication date: 2020-11-19

Abstract

A system for attenuating sound comprises an air compressor with an inlet, the inlet in fluid communication with an ambient environment. An inlet conduit extends from the inlet to the ambient environment, and an expansion volume is in fluid communication with the inlet conduit. A throttling valve or pressure relief valve is located between the expansion volume and the ambient environment, the throttling valve configured to regulate the flow of sound waves from the expansion volume, thereby attenuating the sound from the air compressor entering the ambient environment.

Description

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority from U.S. Provisional Application No. 62/847,505, filed May 14, 2019, incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to systems for attenuating sound in an inlet of an air compressor system.

BACKGROUND

An air compressor converts power (using an electric motor, diesel or gas engine, or other power source) into potential energy stored as pressurized air. The air compressor forces air into a storage tank, and the air pressure increases as more air is forced into the tank and is compressed. The compressed air can be used for a wide variety of applications (e.g., pressurized cleaning, powering pneumatic tools, etc.). The process of forcing air into the storage tank via an inlet conduit typically results in high noise levels generated by the air compressor, which can travel through the inlet conduit to reach the ambient environment. As described herein, “sound pressure level” refers to the effective pressure of a sound relative to a reference value. A commonly used reference sound pressure level in air is twenty microPascals, which is similar to the sound emitted by a mosquito flying approximately 3 meters away. A higher sound pressure level is generally perceived as noisier than a lower sound pressure level. For example, a sound pressure level of one Pascal is equivalent to 94 decibels (dB), which is similar to the sound emitted by a lawnmower.
As used herein, the terms sound pressure level, noise, and noise level are used interchangeably. To reduce inlet noise levels associated with air compressors, various solutions have been implemented. One method to reduce noise levels emanating from the inlet is to use a large volume (e.g., greater than 2 liters) located along the inlet line. The large volume acts as an acoustic impedance to the sound generated by the air compressor during the compression process. Though effective at reducing the amplitude of the acoustic wave traveling upstream, which can reduce the noise, the large volume requires more space than is desirable. Another method to reduce inlet noise levels is to include a Helmholtz resonator on a side branch or the inlet conduit; however, adding a Helmholtz resonator also has the drawback of requiring more space than is desirable for an air compressor.

SUMMARY

In one set of embodiments, a system for attenuating sound is provided. The system comprises an air compressor with an inlet, the inlet in fluid communication with an ambient environment. An inlet conduit extends from the inlet to the ambient environment, and an expansion volume is in fluid communication with the inlet conduit. A valve is located between the expansion volume and the ambient environment, the valve configured to regulate the flow of sound waves from the expansion volume, thereby attenuating the sound from the air compressor entering the ambient environment.
In another set of embodiments, a system for attenuating sound includes an air compressor comprising an inlet in fluid communication with an ambient environment. An inlet conduit extends from the inlet to the ambient environment, and an expansion volume is in fluid communication with the inlet conduit. A valve is located between the expansion volume and the ambient environment. The valve is configured to regulate a flow of sound waves from the expansion volume, thereby attenuating the sound from the air compressor entering the ambient environment. A controller is configured to control operation of the valve.
In yet another set of embodiments, a compressor includes an inlet in fluid communication with an ambient environment. An inlet conduit extends from the inlet to the ambient environment, and an expansion volume is in fluid communication with the inlet conduit. A valve is located between the expansion volume and the ambient environment. The valve is configured to regulate a flow of sound waves from the expansion volume, thereby attenuating the sound from the air compressor entering the ambient environment.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosure will become apparent from the description, the drawings, and the claims, in which:

FIG. 1A is a block diagram of a conventional air compressor system.

FIG. 1B is a block diagram of a noise attenuation system for a conventional air compressor with an inlet conduit including an expansion volume near an air supply.

FIG. 1C is a block diagram of a noise attenuation system for a conventional air compressor with an inlet conduit including an expansion volume near the air compressor.

FIG. 1D is a block diagram of a noise attenuation system for a conventional air compressor with an inlet conduit including a resonator.

FIG. 2 is a block diagram of a noise attenuation system for a conventional air compressor with an inlet conduit including an expansion volume and a valve, according to some embodiments.

FIG. 3 is an illustration of a chart showing the noise attenuation performance of the systems of FIGS. 1-2, according to some embodiments.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various concepts related to, and implementations of, methods, apparatuses, and systems for attenuating sound in an inlet of an air compressor system, and particularly by bleeding pressure through an exhaust reed valve of a vacuum pump of an internal combustion engine system. The various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the described concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.

I. Overview

An air compressor system may include an inlet conduit through which ambient air is drawn into the compressor. Substantial noise (e.g., greater than 140 dB) is associated with drawing ambient air into an air compressor because of the sound generated by the air compressor when drawing the air into the compressor. Methods to reduce the noise include adding a large volume (e.g., greater than 2 liters) in line with the inlet conduit. The large volume provides a space for the sound waves from the air compressor to reflect off the wall of the large volume and collide with each other. During these collisions, waves of the same resonant frequency can collide and cancel each other out, thereby reducing the sound pressure level. However, the large volume can create inefficiencies in design by requiring more space than desired. Additionally, a resonator can be added to a side branch of the inlet conduit. The resonator also provides a space in which the sound waves can collide and cancel each other out, but also requires more space than is desirable.
Implementations herein relate to modifying the inlet conduit of an air compressor by combining a small volume (e.g., 2 liters or smaller) in line with the inlet conduit with a valve to regulate sound waves exiting the volume. The valve can include a throttling valve, a bleed valve, or any other kind of valve that can regulate air flow. The small volume provides a space similar to the large space in which the amplitude of the sound is reduced, thereby reducing the noise created by the air compressor. The valve further reduces the noise created by the sound waves by reducing the flow of sound from the volume, further reducing the amplitude of the sound waves. The combination of the valve and the small volume serves to reduce the noise of the air compressor more than if the small volume or the valve were used alone. Adding the small volume in line with the inlet conduit also provides greater design flexibility than using a large volume because the small volume requires less space than the large volume or a resonator.

II. Example Noise Attenuation Systems

FIG. 1A is a block diagram of a conventional air compressor system 100. The air compressor system 100 includes an air compressor 102 and an inlet conduit 104. The inlet conduit 104 includes an aperture 106. The air compressor 102 can be any conventional air compressor (e.g., piston, rotary-screw, vane, centrifugal, axial, and any other type of conventional air compressor). The inlet conduit 104 defines the aperture 106 that extends entirely through the length of the inlet conduit 104 from an ambient air supply to the air compressor 102. In operation, the air compressor 102 draws ambient air through the inlet conduit 104 via the aperture 106 such that the ambient air fills the air compressor 102 and is compressed by the air compressor 102.
The conventional air compressor system 100 does not include a method or system for noise attenuation. Accordingly, the sound waves generated by the air compressor 102 are not reduced, and experimental results have shown the noise generated by the conventional air compressor system 100 can be as high as approximately 165 dB in the inlet conduit 104. The experimental results will be further described with reference to FIG. 3.
Generally, when the air compressor system 100 is started and begins to compress air without a system for noise attenuation, the sound pressure level in the ambient environment can increase by 2 dB. Generally, when a large volume (e.g., 3 liters or greater) is added to the inlet conduit, the sound pressure level in the ambient environment increases by less than 2 dB.
FIG. 1B is a block diagram of a noise attenuation system 120 for the air compressor 102 with an inlet conduit 122 including the expansion volume 110 near an ambient environment. The inlet conduit 122 includes an aperture 124. The inlet conduit 122 is substantially similar to the inlet conduit 104 with the addition of the expansion volume 110. The aperture 124 is substantially similar to the aperture 106. The expansion volume 110 is a small volume (e.g., less than 2 liters) and is coupled in line with the inlet conduit 122. The expansion volume 110 and the inlet conduit 122 can be a single component; however, the expansion volume 110 and the inlet conduit 122 can be separate components coupled together by a wide variety of suitable known attachment mechanisms. The expansion volume 110 is located closer to the aperture 124 than it is to the air compressor 102.
The expansion volume 110 provides a space in which the sound waves generated by the air compressor 102 fill the expansion volume 110. The expansion volume 110 allows the sound waves to collide with the walls of the expansion volume 110 and with other sound waves, thereby reducing the amplitude of the sound waves. When sound waves of the same resonant frequency collide with each other, the sound waves cancel each other out, thereby further reducing the amplitude of the sound waves before reaching the ambient environment. Experimental results have shown that including the expansion volume 110 closer to the ambient air can result in noise reduction when the air compressor 102 is run at higher frequencies (e.g., greater than 100 Hertz (Hz)). However, experimental results have also shown that the effectiveness of the expansion volume 110 decreases as the expansion volume 110 moves closer to the ambient environment. The experimental results are further described with reference to FIG. 3.
FIG. 1C is a block diagram of a noise attenuation system 140 for the air compressor 102 with an inlet conduit 142 including the expansion volume 110 near the air compressor 102. The inlet conduit 142 includes an aperture 144. The inlet conduit 142 is substantially similar to the inlet conduit 104 with the addition of the expansion volume 110. The aperture 144 is substantially similar to the aperture 106. The expansion volume 110 is a small volume (e.g., less than 2 liters) and is coupled in line with the inlet conduit 142. The expansion volume 110 and the inlet conduit 142 can be a single component; however, the expansion volume 110 and the inlet conduit 142 can be separate components coupled together by a wide variety of suitable known attachment mechanisms. The expansion volume 110 is located closer to the air compressor 102 than it is to the ambient environment.
The expansion volume 110 provides a space in which the sound waves generated by the air compressor 102 fill the expansion volume 110. The expansion volume 110 allows the sound waves to collide with the walls of the expansion volume 110 and with other sound waves, thereby reducing the amplitude of the sound waves. When sound waves of the same resonant frequency collide with each other, the sound waves cancel each other out, thereby further reducing the amplitude of the sound waves. Experimental results have shown that including the expansion volume 110 close to the air compressor 102 can result in noise reduction when the air compressor 102 is run at frequencies greater than 50 Hz. The experimental results are further described with reference to FIG. 3.
FIG. 1D is a block diagram of a noise attenuation system 160 for the air compressor 102 with an inlet conduit 162 including a resonator 170. The inlet conduit 162 includes an aperture 164. The inlet conduit 162 is substantially similar to the inlet conduit 104 with the addition of the resonator 170. The aperture 164 is substantially similar to the aperture 106. The resonator 170 is a small volume (e.g., less than 2 liters) and is coupled to the inlet conduit 162 by a side branch (e.g., the resonator 170 is not located in line with inlet conduit 162). Examples of the resonator 170 include a Helmholtz resonator and a quarter-wave tube resonator. The resonator 170 and the inlet conduit 162 can be a single component; however, the resonator 170 and the inlet conduit 162 can be separate components coupled together by a wide variety of suitable known attachment mechanisms. The resonator 170 is located anywhere along the inlet conduit 162.
The resonator 170 functions similarly to the expansion volume 110 by providing a space in which the sound waves traveling into the inlet conduit 162 from the air compressor 102 can fill the resonator 170 by passing through the side branch. The resonator 170 can absorb sound waves at the resonant frequency of the resonator 170. Accordingly, using a resonator 170 has been shown to reduce noise in the air compressor 102 when the air compressor 102 is run at frequencies lower than 50 Hz. Experimental results will be further described with reference to FIG. 3.
FIG. 2 is a block diagram of a noise attenuation system 200 for the air compressor 102 with an inlet conduit 202 including the expansion volume 110 and a valve 206, according to some embodiments. The inlet conduit 202 is substantially similar to the inlet conduit 104 with the addition of the expansion volume 110 and the valve 206. The inlet conduit 202 includes an aperture 204. The aperture 204 is substantially similar to the aperture 106. The expansion volume 110 is a small volume (e.g., less than 2 liters) and is coupled in line with the inlet conduit 202. The expansion volume 110 and the inlet conduit 202 can be a single component; however, the expansion volume 110 and the inlet conduit 202 can be separate components coupled together by a wide variety of suitable known attachment mechanisms. The expansion volume 110 is located closer to the air compressor 102 than it is to the ambient air.
The valve 206 is located between the expansion volume 110 and the ambient air and is in fluid communication with the aperture 204. In some embodiments, the valve 206 is located close to the air compressor 102 (e.g., within 0-25% of the length of the inlet conduit 202 extending from the air compressor). In some embodiments, the valve 206 is located close to the ambient environment (e.g., within 0-25% of the inlet conduit 202 extending from the ambient environment). The valve 206 can be any type of valve configured to regulate flow through an aperture. Non-limiting examples of the valve 206 include a throttling valve, a pressure relief valve (for example, in the form of a bleed valve), or any other kind of valve designed to regulate flow.
In embodiments where the valve 206 is a throttling valve, the valve 206 can provide full air flow (e.g., a fully open valve 206) such that the noise attenuation system 200 functions in a manner substantially similar to that of the noise attenuation system 140. The valve 206 can also stop air flow (e.g., a fully closed valve 206), thereby preventing the air compressor 102 from drawing in ambient air. The valve 206 can also provide air flow at any rate between a fully open valve 206 and a fully closed valve 206 such that sounds waves traveling from the expansion volume 110 toward the ambient environment can be controlled to provide for noise attenuation. The valve 206 can be adjusted to meet the needs of the user using the air compressor 102. For example, if the user is running the air compressor 102 at a high frequency, the user may need to compensate for additional noise by adjusting the valve 206. Furthermore, the user may run the air compressor 102 at a lower frequency at a later time, and the user may adjust for the change in noise from the aperture 204 by adjusting the valve 206. In some embodiments, the valve 206 may be controlled by a computer or controller to automatically adjust the valve 206 to compensate for noise emanating from the aperture 204. For example, the controller may control one or more actuators configured to adjust the position of the valve 206 to allow for more or less airflow. The controller may instruct the one or more actuators based on a threshold noise level. In some embodiments, when the actual noise level is greater than the threshold noise level, the controller may instruct the one or more actuators to move the valve 206 toward the closed position to allow less airflow, thereby reducing the noise level until the threshold noise level is reached. In addition, when the actual noise level is less than the threshold noise level, the controller may instruct the one or more actuators to move the valve 206 toward the open position to allow more airflow, thereby increasing the noise level until the threshold noise level is reached. The threshold noise level may be adjusted based on noise in the ambient environment (e.g., noise not generated by a compressor)
In embodiments where the valve 206 is a bleed valve, the valve 206 can be designed to allow air to escape from the inlet conduit 202 when the air pressure in the inlet conduit 202 is higher than a specified level. The amount can be based on the noise attenuation achieved at certain air pressures. If the air pressure in the inlet conduit 202 rises above the specified level, the valve 206 opens and the air is released from the valve 206 until the air pressure is reduced below the specified level. When the air pressure is below the specified level, the valve 206 closes and allows air to continue to flow toward the expansion volume 110.
FIG. 3 is an illustration of a chart 300 showing the noise attenuation of the systems of FIGS. 1-2. As shown, the chart 300 compares the engine speed of a vehicle measured in revolutions per minute (RPM) (on the x-axis 302) to the sound pressure level generated by the air compressor 102 at the inlet conduit (on the y-axis 304). Generally, when the air compressor 102 is in a vehicle, the engine of the vehicle drives the air compressor 102 (e.g., as the engine works harder, the air compressor 102 works harder). The curve 306 was generated experimentally using the conventional air compressor system 100, the curve 308 was generated experimentally using the noise attenuation system 140, and the curve 310 was generated experimentally using the noise attenuation system 200.
Generally, peaks on any of the curves on the chart 300 indicate a local point of resonance in the system, which results in a loud noise emanating from the inlet conduit. Furthermore, low points on any of the curves on the chart 300 indicate a local point of maximum noise attenuation (e.g., the lowest noise). For example, the peak 314 on the curve 306 indicates that a loud noise (approximately 165 dB) emanates from the aperture 106 when the engine is running at approximately 1000 RPM. In contrast, the low point 312 on the curve 306 indicates that the noise emanating from the aperture 106 is lower (approximately 163 dB) when the engine is running at approximately 1050 RPM.
As indicated by the curve 306, the air compressor system 100 (which does not include any noise attenuation) is generally the loudest system, with the minimum noise level of approximately 159 dB occurring at approximately 600 RPM. The noise attenuation system 140 provides for lower noise (e.g., between approximately 152 dB and approximately 159 dB) emanating from the aperture 124 as compared with the noise from the air compressor system 100. Experimental results have shown that the noise emanating from the noise attenuation system 120 and the noise attenuation system 160 exhibit curves that fall between the curve 306 and the curve 308, indicating that the noise attenuation system 140 is more effective at attenuating noise than the noise attenuation system 120 or the noise attenuation system 160. Accordingly, the curves for the noise attenuation system 120 and the noise attenuation system 160 are not shown on the chart 300.
The curve 310 was generated from experimental results from the noise attenuation system 200 that incorporates the expansion volume 110 near the air compressor 102 and the valve 206 between the expansion volume 110 and the air supply. The valve 206 provides a user with the capability to continuously adjust the size of the aperture 204 such that the sound waves in the noise attenuation system 200 are captured or cancelled by the expansion volume 110, thereby attenuating the noise that would otherwise occur without the operation of the valve 206. Accordingly, the noise attenuation system 200 creates a smoother curve than the air compressor system 100 and the noise attenuation system 120, resulting in a more constant noise profile as the air compressor 102 works at different engine RPM levels. Furthermore, the overall noise created by the noise attenuation system 200 is lower than the air compressor system 100 and the noise attenuation systems 120, 140, and 160.

III. Construction of Example Embodiments

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed but rather as descriptions of features specific to particular implementations. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
As utilized herein, the terms “approximately,” “substantially” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.
The terms “coupled,” “connected,” and the like, as used herein, mean the joining of two components directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two components or the two components and any additional intermediate components being integrally formed as a single unitary body with one another, with the two components, or with the two components and any additional intermediate components being attached to one another.
It is important to note that the construction and arrangement of the system shown in the various example implementations is illustrative only and not restrictive in character. All changes and modifications that come within the spirit and/or scope of the described implementations are desired to be protected. It should be understood that some features may not be necessary, and implementations lacking the various features may be contemplated as within the scope of the application, the scope being defined by the claims that follow. When the language a “portion” is used, the item can include a portion and/or the entire item unless specifically stated to the contrary.
Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated.
Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. For example, elements shown as integrally formed may be constructed of multiple components or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any method processes may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.

Claims

What is claimed is:

1. A system for attenuating sound, comprising:

an air compressor comprising an inlet, the inlet in fluid communication with an ambient environment;

an inlet conduit extending from the inlet to the ambient environment;

an expansion volume in fluid communication with the inlet conduit; and

a valve located between the expansion volume and the ambient environment, the valve configured to regulate a flow of sound waves from the expansion volume, thereby attenuating the sound from the air compressor entering the ambient environment.

2. The system of claim 1, wherein the valve is configured to substantially eliminate resonance from the sound of the air compressor entering the ambient environment.

3. The system of claim 2, wherein the inlet conduit comprises a conduit outer diameter and the expansion volume comprises a volume outer diameter, the volume outer diameter being larger than the conduit outer diameter.

4. The system of claim 1, wherein the valve is a throttling valve.

5. The system of claim 1, wherein the valve is a pressure relief valve.

6. The system of claim 2, wherein the valve is located within 0-25% of a length of the inlet conduit extending from the air compressor.

7. The system of claim 2, wherein the valve is located within 0-25% of a length inlet conduit extending from the ambient environment.

8. A system for attenuating sound, comprising:

an inlet conduit extending from the inlet to the ambient environment;

an expansion volume in fluid communication with the inlet conduit;

a valve located between the expansion volume and the ambient environment, the valve configured to regulate a flow of sound waves from the expansion volume, thereby attenuating the sound from the air compressor entering the ambient environment; and

a controller configured to control operation of the valve.

9. The system of claim 8, wherein the valve is configured to substantially eliminate resonance from the sound of the air compressor entering the ambient environment.

10. The system of claim 8, wherein the controller is configured to adjust the valve based on the sound from the air compressor.

11. The system of claim 10, wherein the inlet conduit comprises a conduit outer diameter and the expansion volume comprises a volume outer diameter, the volume outer diameter being larger than the conduit outer diameter.

12. The system of claim 11, wherein the valve is a throttling valve.

13. The system of claim 11, wherein the valve is a pressure relief valve.

14. The system of claim 11, wherein the valve is located within 0-25% of a length of the inlet conduit extending from the air compressor.

15. The system of claim 11, wherein the valve is located within 0-25% of a length inlet conduit extending from the ambient environment.

16. A compressor, comprising:

an inlet, in fluid communication with an ambient environment;

an inlet conduit extending from the inlet to the ambient environment;

an expansion volume in fluid communication with the inlet conduit; and

a valve located between the expansion volume and the ambient environment, the valve configured to regulate a flow of sound waves from the expansion volume, thereby attenuating a sound from the compressor entering the ambient environment.

17. The compressor of claim 16, wherein the valve is configured to substantially eliminate resonance from the sound of the compressor entering the ambient environment.

18. The compressor of claim 16, wherein the inlet conduit comprises a conduit outer diameter and the expansion volume comprises a volume outer diameter, the volume outer diameter being larger than the conduit outer diameter.

19. The compressor of claim 17, wherein the valve is a throttling valve.

20. The compressor of claim 17, wherein the valve is a pressure relief valve.