This disclosure relates generally to an exhaust component having an opening formed within a wall that is covered with a membrane that is moveable in response to pressure fluctuations to reduce noise.
Vehicle exhaust systems direct exhaust gases generated by an internal combustion engine to the external environment. These systems are comprised of various components such as pipes, converters, catalysts, filters, etc., which are used to reduce emissions. The overall system and/or the components are capable of generating undesirable noise as a result of resonating frequencies. Different approaches have been used to address this issue. For example, components such as mufflers, resonators, valves, etc., have been incorporated into exhaust systems in an attempt to attenuate certain resonance frequencies generated by the exhaust system. Including additional components can be expensive and increases weight, while also introducing new sources for noise generation.
A vehicle exhaust system according to an exemplary aspect of the present disclosure includes, among other things, an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity. At least one hole is formed in the exhaust component to extend through the wall of the exhaust component from the outer surface to the inner surface. A membrane is configured to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.
In a further non-limiting embodiment of the foregoing vehicle exhaust system, the membrane is made from a flexible material.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the flexible material can withstand temperatures within a range of 500-850 degrees Celsius.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the wall comprises a rigid structure that has a first compliance and the membrane comprises a flexible structure that has a second compliance that is greater than the first compliance, and wherein the membrane elastically deforms in response to pressure changes within the internal exhaust component cavity.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the membrane is impermeable.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the wall is impermeable.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the at least one hole is positioned at a pressure anti-node.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the at least one hole comprises a plurality of holes that are each positioned at a pressure anti-node and which are each covered by a corresponding membrane.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the exhaust component comprises a pipe having an overall pipe length extending from a first pipe end to a second pipe end, and wherein the at least one hole is positioned at a pressure anti-node location that is approximately 25%, 50%, or 75% of the overall pipe length.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the at least one hole comprises a plurality of holes that are each positioned at one of the pressure anti-node locations.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, each hole is covered by a separate membrane.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the membrane has both stiffness and damping and the pressure fluctuations cause the membrane to move and absorb energy from an oscillating wave resulting in lower downstream pressure oscillations.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the stiffness and damping are adjusted such that a resonant frequency of the membrane is tuned to provide maximum suppression of the downstream pressure oscillations.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the membrane is made from a flexible material that is impermeable and elastically deformable.
In a further non-limiting embodiment of any of the foregoing vehicle exhaust systems, the outer surface of the wall and the membrane are directly exposed to external atmosphere.
A method according to still another exemplary aspect of the present disclosure includes, among other things: providing an exhaust component comprising a wall having an outer surface and an inner surface that defines an internal exhaust component cavity; forming at least one hole in the exhaust component to extend through the wall from the outer surface to the inner surface; and positioning a membrane to overlap the at least one hole, wherein the membrane is moveable relative to the wall in response to pressure fluctuations.
In a further non-limiting embodiment of the foregoing method, the method includes forming the membrane from a flexible material that is impermeable, elastically deformable, and can withstand temperatures within a range of 500-850 degrees Celsius.
In a further non-limiting embodiment of any of the foregoing methods, the wall comprises a rigid structure that has a first compliance and the membrane comprises a flexible structure that has a second compliance that is greater than the first compliance, and wherein the membrane elastically deforms in response to pressure changes within the internal exhaust component cavity.
In a further non-limiting embodiment of any of the foregoing methods, the method includes positioning the at least one hole at a pressure anti-node.
In a further non-limiting embodiment of any of the foregoing methods, the at least one hole comprises a plurality of holes, and including positioning each hole at a pressure anti-node, covering each hole with a separate membrane, and adjusting stiffness and damping of the membrane such that a resonant frequency of the membrane is tuned to provide maximum suppression of downstream pressure oscillations.
The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.
The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows:
This disclosure details an exemplary exhaust component having an opening formed within a wall that is covered with a membrane, which is moveable in response to pressure fluctuations to reduce resonance noise.
The exhaust system 10 includes at least one acoustic damping membrane 18 (shown schematically in
At least one hole 28 is formed in the pipe 20 to extend through a thickness of a wall 30 of the pipe 20 from the outer surface 22 to the inner surface 24. The membrane 18 is formed from a flexible material and is configured to overlap the hole 28. The membrane 18 moveable relative to the wall 30 in response to pressure fluctuations. It should be understood that while the membrane 18 is shown as being used with a pipe 20, the membrane 18 could also be used in any of the various exhaust components 14 as needed, such as in a muffler or in a pipe that is mounted within a muffler, for example.
As discussed above, the membrane 18 is made from a flexible material and is impermeable such that no fluids, i.e. liquid or gas, can pass through the membrane 18. Depending on the application location, the maximum temperature requirements for the flexible membrane 18 could be anywhere from 500-850° C. For lower temperature applications, e.g. less than 600° C., the flexible membrane 18 be made using a copper-beryllium alloy. For applications above 600° C., a stainless-steel membrane, made from 304SS for example, could be used. Obviously, other materials may be used as appropriate. For colder applications, e.g. less than 260° C., silicone could be used for example.
In one example, the wall 30 comprises a rigid structure that has a first compliance and the membrane 18 comprises a flexible structure that has a second compliance that is greater than the first compliance. The membrane 18 elastically deforms in response to pressure changes within the internal exhaust component cavity 26. As such, the membrane 18 has a rest position, where the membrane 18 lies generally flat and/or conforms to a shape of the wall 30 along the outer surface 22, and an active position where the pressure fluctuations within the exhaust component cause portions of the membrane 18 to move relative to the wall 30, e.g. expand and/or contract, before returning the rest position.
The outer surface 22 of the wall 30 and an outer surface 36 of the membrane are both directly exposed to external atmosphere. As discussed above, the membrane 18 is made from a flexible material that is impermeable. The wall 30 of the exhaust component 20 is also impermeable. As such, none of the exhaust gas flowing through the exhaust component 20 can leak out or escape to the external atmosphere. This also prevents any fluid or debris from getting into the exhaust component 20 via the hole 28.
In one example, the at least one hole 28 comprises a single or only hole 28 in the pipe 20. In another example, the at least one hole 28 comprises a plurality of holes 28 that are formed within the pipe 20. In one example, the hole 28 is positioned at a pressure anti-node. When multiple holes 28 are provided, each hole 28 can be positioned at a pressure anti-node, with each hole 28 being covered by a separate membrane 18.
In another example, the at least one hole comprises only a first hole 28 and a second hole 28′ that extend entirely through the wall 30. In this example, the first hole 28 is positioned at the location that is approximately 50% of the pipe length L and the second hole 28′ is positioned at location that is approximately 75% of the pipe length from one end or 25% from an opposite end as optionally indicated at one of two possible locations in
As shown in
For a configuration with a flexible membrane 18 formed from a thin stainless steel diaphragm, the membrane 18 may be welded to the adjoining pipe 20, for example.
The subject disclosure uses one or more flexible patches or membranes 18 on a pipe 20 whose resonances are to be suppressed. The membrane 18 is elastic and impermeable such that exhaust gas does not leak out under a body of the vehicle, which avoids any possibility of undesirable odor, CO intrusion, high thermal effects, etc. The flexible membranes 18 are located at the pressure anti-node locations 38 to provide maximum effect. Several such flexible membranes 18 can be provided in order to address several pipe modes or one pipe mode more effectively.
The compliance of the flexible membrane 18 is much greater than that of the adjoining pipe 20. As such, the flexible membrane 18 will deform in reaction to the changing pressure. Additionally, there is no increased radiated noise or flow noise, or back pressure compared to prior solutions that utilize a porous member open to the atmosphere combined with a deflector to eliminate leakage of the exhaust gas.
Although a specific component relationship is illustrated in the figures of this disclosure, the illustrations are not intended to limit this disclosure. In other words, the placement and orientation of the various components shown could vary within the scope of this disclosure. In addition, the various figures accompanying this disclosure are not necessarily to scale, and some features may be exaggerated or minimized to show certain details of a particular component.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.