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 air cleaner of this disclosure includes a hollow case, a filter element, and an opening end member. The hollow case defines an expanded space; the filter element defines an upstream-side expanded space and a downstream-side expanded space in the expanded space; the case includes an intake port configured to bring an upstream-side duct into communication with the upstream-side expanded space; the opening end member is formed from a material having an air permeability in a range of 0.3 to 100 sec/300 cc, and is integrated on an inner side of the intake port so as to project into the upstream-side expanded space and so as to extend a duct wall of the intake port; and D representing a diameter of the opening end member and L representing a length thereof satisfy 0.25D≦L≦2.0D.

A stern drive is for propelling a marine vessel in water. The stern drive is configured to power a propulsor located below the surface of the water. The stern drive comprises an internal combustion engine that powers a driveshaft that axially extends through a transom of the marine vessel; an exhaust manifold that conveys exhaust gas from the internal combustion engine; and an elongated exhaust conduit that redirects the exhaust gas from the exhaust manifold transversely with respect to the driveshaft. The elongated exhaust conduit conveys the exhaust gas to an upstream exhaust outlet that discharges the exhaust gas through the transom below the surface of the water and then to a downstream exhaust outlet that is spaced apart from and is located vertically higher than the upstream exhaust outlet. The elongated exhaust conduit functions as a water lift muffler during operation of the stern drive.

An exhaust muffler has an exhaust inlet, an exhaust outlet, as well as a catalytic converter which, in the flow direction, is disposed between the exhaust inlet and the exhaust outlet. The catalytic converter has at least one throughflow body which includes at least one wire body. At least one first component region of the throughflow body is coated with a catalytically functioning coating. The throughflow body moreover has a second component region which in terms of volume has a smaller quantity of catalytically functioning coating than the first component region.

An exhaust gas treatment system for an internal combustion engine includes an exhaust gas pathway configured to receive exhaust gas from the internal combustion engine, a first treatment element positioned within the exhaust gas pathway, a first injector configured to introduce a first reductant into the exhaust gas pathway upstream of the first treatment element, a second injector configured to introduce a second reductant into the exhaust gas pathway downstream of the first treatment element, a second treatment element positioned within the exhaust gas pathway downstream of the second injector, the second treatment element including a SCR element, and a controller configured to periodically initiate a desulfuring regeneration cycle by increasing a concentration of hydrocarbons in the exhaust gas and increasing the flow of the first reductant through the first injector to oxidize sulfur contamination in the first treatment element at temperatures between 400 and 500 degrees Celsius.

An exhaust silencer includes a housing defining an interior and a tube disposed in the interior and defining an opening. A gas-flow deflector is configured to heat shield an interior wall of the housing from exhaust gases exiting the opening. The deflector has a deflector plate and a riser. The riser has a first portion connected to the interior wall and a second portion connected to a backside of the deflector plate to suspend the deflector plate in the interior such that the backside is completely spaced from the interior wall to form an insulating airgap therebetween.

An exhaust silencer includes a housing defining an interior and a tube disposed in the interior and defining an opening. A gas-flow deflector is configured to heat shield an interior wall of the housing from exhaust gases exiting the opening. The deflector has a deflector plate and a riser. The riser has a first portion connected to the interior wall and a second portion connected to a backside of the deflector plate to suspend the deflector plate in the interior such that the backside is completely spaced from the interior wall to form an insulating airgap therebetween.

A sound suppression apparatus for installation inside a gas transport duct is provided. The sound suppression apparatus comprises a resistive sound-absorbing element (110) and a housing providing a reactive sound-attenuating element (130) communicating with a surrounding of the apparatus via opening in an outer surface of the housing. An outer surface of the sound suppression apparatus comprises an outer surface of the resistive sound-absorbing element and the outer surface of the housing. A gas transport duct comprising the sound suppression apparatus is also provided.

A sound suppression apparatus for installation inside a gas transport duct is provided. The sound suppression apparatus comprises a resistive sound-absorbing element (110) and a housing providing a reactive sound-attenuating element (130) communicating with a surrounding of the apparatus via opening in an outer surface of the housing. An outer surface of the sound suppression apparatus comprises an outer surface of the resistive sound-absorbing element and the outer surface of the housing. A gas transport duct comprising the sound suppression apparatus is also provided.

A muffler includes a first chamber, a second chamber, an extender tube, a reverse flow tube, and a separation chamber. The first chamber is coupled to an exhaust inlet of the muffler. The extender tube is coupled to the first chamber and the second chamber. The exhaust gas flows from the first chamber to the second chamber through the extender tube in a first direction. The reverse flow tube coupled to the second chamber. The exhaust gas flows through the second chamber from the extender tube to the reverse flow tube in a second direction different than the first direction. The separation chamber that provides spatial separation between the first and second chamber.