An acoustic silencer for dampening unwanted resonant and pressure pulses in a pipe or duct work and includes an expansion chamber having an enclosed volume through which a pipe or duct work extends, thereby defining an annular volume within the enclosed volume between the process pipe and the expansion chamber. An insert disposed within the annular volume extends along the length of the process pipe and forms an acoustic volume within the annular volume and defines a resonant passage length that is of a length so as to dampen one or more frequencies of the process pipe. An opening is formed through the process pipe along the length of the process pipe that extends through the expansion chamber and is in fluidic communication with the acoustic volume.

A muffler for exhaust gases of a combustion engine includes walls forming a chamber through which the exhaust gases pass, a first inlet in the walls of the chamber configured to receive the exhaust gases from an exhaust duct of the engine, a first outlet in the walls of the chamber through which the exhaust gases exit the chamber, and a conduit having a second inlet and a second outlet, wherein a substantial length of the conduit is positioned within the chamber.

An exhaust aftertreatment system may include an injector, an aftertreatment device and a mixer assembly. The injector may be configured to inject a fluid into an exhaust passageway that receives exhaust gas from a combustion engine. The aftertreatment device may be disposed in the exhaust passageway downstream of the injector. The mixer assembly may be disposed in the exhaust passageway upstream of the aftertreatment device and may include a first stage having a plurality of parallel plates and a second stage connected to the first stage and disposed downstream of the first stage. The second stage may include an auger blade. The mixer assembly may divide an exhaust stream into at least two flow paths.

In the present disclosure is proposed a novel sound attenuating element for, at least in part, providing adequate or preferably improved sound attenuating properties without excessively impeding flow while being susceptible to automated or machine assisted manufacturing or for providing the public with a useful alternative. The novel sound attenuating element is formed at least in part by an assembly of a plurality of components which are successively connected to each other, which each exhibit a curved shape, and which form at least one non-planar ruled surface when assembled.

A bilayler metamaterial silencer allows substantial fluid through the apparatus, while mitigating the propagation of sound through the apparatus, and while providing a form factor that is significantly more compact than previously-known devices. Moreover, illustrative embodiments allow a designer to specify one or both of the frequency or frequencies at which the apparatus mitigates sound propagation, and/or the bandwidth around the frequency or frequencies at which the apparatus mitigates sound propagation.

An exhaust-gas treatment arrangement for an exhaust system of an internal-combustion engine includes a diesel internal-combustion engine. The arrangement includes a first exhaust-gas treatment unit and, downstream of the first exhaust-gas treatment unit, an exhaust-gas treatment assembly. The first exhaust-gas treatment unit and the exhaust-gas treatment assembly are arranged axially succeeding one another in the direction of a longitudinal axis of a flow path encompassing the first exhaust-gas treatment unit and the exhaust-gas treatment assembly. A hydrocarbon-feeding assembly is provided for feeding hydrocarbon into exhaust gas flowing in the flow path. The hydrocarbon-feeding assembly includes a hydrocarbon-dispensing unit dispensing hydrocarbon into the flow path downstream of the first exhaust-gas treatment unit and upstream of the exhaust-gas treatment assembly. A swirl-flow-generating unit is provided in the flow path upstream of the hydrocarbon-dispensing unit.

An SCR system includes a box body, a urea nozzle and a mixer. The mixer is arranged inside the box body, and is cylindrical, and the first end of the mixer faces the urea nozzle. The mixer comprises a check ring, a swirl tube and a perforated pipe which are connected in sequence. The check ring is arranged close to the urea nozzle, and is provided with a plurality of first through holes. Multiple second through holes are formed in the swirl tube, and multiple third through holes are formed in the perforated pipe. The mixer further comprises a retaining ring, an inner ring of the retaining ring is connected to an outer wall of the swirl tube and/or the perforated pipe, and an outer ring of the retaining ring is connected to an inner wall of the box body. Also provided is an engine.