A duct is provided and includes a tubular member having an inlet portion, an outlet portion and a central portion interposed between the inlet and outlet portions and a tributary tubular member fluidly coupled to the tubular member at the central portion. The tributary tubular member includes first and second torus sectors defining first and second apertures, respectively, through which an upstream end of the central portion extends. The second torus sector is disposed within the first torus sector to define a sectioned toroidal annulus about the first and second apertures and between an exterior surface of the second torus sector and an interior surface of the first torus sector.

A duct is provided and includes a tubular member having an inlet portion, an outlet portion and a central portion interposed between the inlet and outlet portions and a tributary tubular member fluidly coupled to the tubular member at the central portion. The tributary tubular member includes first and second torus sectors defining first and second apertures, respectively, through which an upstream end of the central portion extends. The second torus sector is disposed within the first torus sector to define a sectioned toroidal annulus about the first and second apertures and between an exterior surface of the second torus sector and an interior surface of the first torus sector.

A forward secant swirl tube may be used to separate heavier particles such as oil and moisture from an air flow. The swirl tube includes a central hub having a centerline and a circular perimeter. An outer circular housing extends from an inlet edge to an outlet edge. A plurality of vanes extends from the central hub to the outer housing. The vanes are equally spaced around the central hub. Each vane has an inlet transition portion connected to a discharge portion. The top edge of the inlet transition portion of each vane is offset from the centerline of the central hub forming a forward secant line with respect to the centerline of the central hub and a direction of spin induced by the plurality of vanes.

A forward secant swirl tube may be used to separate heavier particles such as oil and moisture from an air flow. The swirl tube includes a central hub having a centerline and a circular perimeter. An outer circular housing extends from an inlet edge to an outlet edge. A plurality of vanes extends from the central hub to the outer housing. The vanes are equally spaced around the central hub. Each vane has an inlet transition portion connected to a discharge portion. The top edge of the inlet transition portion of each vane is offset from the centerline of the central hub forming a forward secant line with respect to the centerline of the central hub and a direction of spin induced by the plurality of vanes.

A combined heat and power system and method of operation is provided. The system includes a combustion chamber configured to directly combust solid organic material. A compressor turbine is fluidly coupled to the combustion chamber. An expansion turbine is fluidly coupled to the combustion chamber. In an embodiment, the system has a low turbine pressure ratio.

A combined heat and power system and method of operation is provided. The system includes a combustion chamber configured to directly combust solid organic material. A compressor turbine is fluidly coupled to the combustion chamber. An expansion turbine is fluidly coupled to the combustion chamber. In an embodiment, the system has a low turbine pressure ratio.

A cyclone unit is for separating liquid and particles from a suction flow. A main flow inlet to the outer housing of the cyclone unit includes an opening. The transition between the main flow inlet and the outer housing at this opening has, at least for a portion of the opening, a radius of curvature of at least 0.5 mm. The large radius of curvature prevents the formation of static water drops.

A cyclone unit is for separating liquid and particles from a suction flow. A main flow inlet to the outer housing of the cyclone unit includes an opening. The transition between the main flow inlet and the outer housing at this opening has, at least for a portion of the opening, a radius of curvature of at least 0.5 mm. The large radius of curvature prevents the formation of static water drops.

A wet vacuum cleaner uses a cyclone unit for separating liquid and particles from a suction flow. A main flow inlet to a cyclone chamber is spaced internally from its respective end by a separation distance. The separation distance is at least 0.1 times (effective/equivalent) diameter of the main flow inlet, which assists in preventing formation of large droplets which follows a path to a main flow outlet.

A wet vacuum cleaner uses a cyclone unit for separating liquid and particles from a suction flow. A main flow inlet to a cyclone chamber is spaced internally from its respective end by a separation distance. The separation distance is at least 0.1 times (effective/equivalent) diameter of the main flow inlet, which assists in preventing formation of large droplets which follows a path to a main flow outlet.