Waveguide or flow guide surfaces can improve the efficiency of fluid flow through tubes or over surfaces. When incorporated in a tube, the waveguides improve flow and function as sound absorbers making them useful in engine mufflers, firearm silencer/suppressors and jet engine exhaust attenuators. On surfaces, the waveguides can reduce fluid drag and find use on projectiles (e.g., bullets), airfoils for aircraft, and land borne vehicles. The waveguide array in either a tubular chamber or on a surface comprises a plurality of successive wave-like undulations inclined generally in the direction of flow and when employed in tubes extending inwardly to permit an unobstructed path for the fluid gas from entry to exit. The waves define annular wave cavities between their successive inwardly extending edges and the wall of the chamber with each cavity having a cavity mouth open to the unobstructed path. The waveguides are sized and spaced so that gas vortices are created within the cavities when gas flow occurs which vortices create a fluid boundary layer that assists the gas flow.

An exhaust muffler is made up of a plurality of layers including an exhaust passage pipe and expansion chambers, and includes a front assembly and a rear assembly sub-assembled separately from the front assembly. The front assembly includes a front exhaust passage pipe, a front muffler body disposed in covering relation to the outside of the front exhaust passage pipe and cooperating with the front exhaust passage pipe in making up double-walled pipes, and an exhaust valve disposed in the front exhaust passage pipe. The rear assembly includes a rear exhaust passage pipe and a rear muffler body disposed in covering relation to the outside of the rear exhaust passage pipe and cooperating with the rear exhaust passage pipe in making up double-walled pipes. There is thus provided an exhaust device for an internal combustion engine in which the accuracy of a position where the exhaust valve is installed is high.

An exhaust after-treatment assembly for an engine system is provided. The exhaust after-treatment assembly includes a housing having an inlet port, an outlet port, a catalyst disposed within a cavity defined by the housing, and a muffler assembly disposed within the cavity downstream of the catalyst. The muffler assembly includes one or more baffle plates disposed longitudinally spaced from one another within the housing to define at least a first resonator chamber and a second resonator chamber. Each of the baffle plates defines an openings aligned to one another about a longitudinal axis of the housing. Further, a resonator tube extends through the openings of the baffle plates and includes an inlet, a perforated portion and one or more outlet ports formed in a wall of the resonator tube. The perforated portion and the outlet ports, respectively in fluid communication with the second resonator chamber and the first resonator chamber.

There is provided a muffler structure of a saddle-type vehicle. The muffler structure is disposed at a downstream side of an exhaust pipe extending from an exhaust port of a cylinder head. A pipe is connected to the exhaust pipe and inserted into a muffler main body. The muffler main body includes a cylindrical portion and a reduced diameter portion joined to a downstream side end portion of the cylindrical portion and having a diameter reduced toward the downstream side thereof. The pipe includes a center pipe passing through the cylindrical portion, and a tail pipe disposed in the reduced diameter portion. An expansion chamber is formed by a space in the reduced diameter portion in the vicinity of the tail pipe.

An exhaust muffler includes first and second pipes which extend through a casing, and which are disposed so that a downstream end of the first pipe faces an upstream end of the second pipe, wherein the downstream end of the first pipe and the upstream end of the second pipe are disposed so as to be spaced from each other in an axial direction, one end part of a support member having a circular cross section that has a smaller diameter than those of the first and the second pipes is fixed to one of a first lid member covering an opening at the downstream end of the first pipe and a second lid member covering an opening at the upstream end of the second pipe, and the other end part of the support member is slidably fitted to the other of the first and the second lid members.

An engine muffler apparatus for reducing noise and pollution from small gas engines such as those on landscaping tools includes an outer housing having a central neck extension with a principal aperture extending through to an outer housing cavity. The neck extension is selectively engageable with an exhaust of a small gas engine. The outer housing cavity has a plurality of vent apertures. An intake extension tube and a medial tube are coupled to the outer housing cavity. The medial tube has a medial cavity. A first filtering medium is coupled within the medial cavity and filters pollutants passing therethrough. A second filtering medium is coupled within the outer housing cavity outside of the medial tube and dampens sound waves passing through the apparatus from the exhaust.

An exhaust pipe includes a tubular portion and a space forming portion. The tubular portion forms an exhaust flow path in an exhaust system of an internal combustion engine. The tubular portion has a tubular shape. The space forming portion is provided along at least one of an inner surface and an outer surface of the tubular portion and forms at least one branch space between the space forming portion and the tubular portion. The at least one branch space communicates with the exhaust flow path and has a function as a side-branch muffler. The at least one branch space includes a space with a length that is one third or more of an entire length of the exhaust system.

A muffler unit includes: an inner cylinder connected with a first exhaust pipe; a first outlet pipe that is connected with a downstream end of the inner cylinder and through which exhaust gas is discharged; an outer cylinder that houses thereinside the inner cylinder and defines, between the outer cylinder and an outer surface of the inner cylinder, an expansion chamber communicating with the second exhaust pipe; and a second outlet pipe that houses thereinside the first outlet pipe and defines, between the second outlet pipe and an outer surface of the first outlet pipe, a path connected with the expansion chamber to thereby be used for discharging the exhaust gas. Accordingly, there is provided the muffler unit having a size reduced compared with a configuration including two mufflers disposed in parallel with each other.

A device for reducing airborne and structure-borne sound has a flow channel with a flow channel wall (22, 22′, 22″) and at least one resonator chamber (40, 40′, 40″) adjacent the flow channel wall (22, 22′, 22″). The flow channel wall is formed by a sound absorber (30, 30′, 30″) at least in a part bordering the resonator chamber (40, 40′, 40″). The sound absorber (30, 30′, 30″) is covered towards the resonator chamber (40, 40′, 40″) by an acoustically reflecting inner wall (42, 42′, 42″) of the resonator chamber with at least one wall aperture (44, 44′, 44″). Openings (32, 32′, 32″) completely covers the wall aperture (44, 44′, 44″) of the inner wall (42, 42′, 42″) of the resonator chamber such that sound waves flowing through the flow channel must pass the sound absorber (30, 30′, 30″) to enter the resonator chamber (40, 40′, 40″).

An exhaust device includes a housing, first and second pipes, and a spacer. The first and second pipes are at least partially disposed within the housing. The first and second pipes include respective first and second surfaces. A portion of the second pipe is disposed inside the first pipe. The first and second surfaces cooperate to define an annular volume into which the spacer is disposed to prevent direct communication between the first and second pipes. One of the first and second pipes is fluidly connected to an exhaust gas inlet. The other of the first and second pipes is fluidly connected to an exhaust gas outlet. One of the first and second surfaces defines a radial indentation. The other of the first and second surfaces defines a radial protrusion. The spacer is disposed at least partially within the radial indentation and is in direct communication with the radial protrusion.