A screw pump comprising a housing defining a chamber and two screw rotors. Wherein each screw rotor comprises a rotor shaft and at least two displacement elements connected with the rotor shaft. Each displacement element having at least one helical protrusion. One of the displacement elements is a suction-side displacement element arranged in a suction-side section of the chamber. Another one of the displacement elements is a pressure-side displacement element arranged in a pressure-side section of the chamber. The suction-side displacement element is designed tapering in the conveying direction. The clearance between the pressure-side displacement element and the pressure-side section of the chamber at least partly decreases in the conveying direction. Furthermore, a screw rotor, a method of manufacturing a screw rotor and a use of a screw pump or a screw rotor.

A blower assembly includes, but is not limited to, a blower housing defining a blower chamber and including a gas inlet and a gas outlet; a first rotor positioned within the blower chamber and adapted for rotation therein, the first rotor including a first shaft and at least two lobes defining a first lobe profile; and a second rotor positioned within the blower chamber and adapted for rotation therein, the second rotor including a second shaft and at least two lobes defining a second lobe profile, wherein the first and second rotors are formed from a metal having a coefficient of thermal expansion from about 1 (10.sup.6 in/in*K) to about 13 (10.sup.6 in/in*K), and wherein at least one of the outer surface of the first rotor, the outer surface of the second rotor, or the blower chamber includes a coating.

A first coating layer formed by tin plating is formed on a compression chamber-side end face of a baseplate of one scroll and a surface of a spiral wall, a second coating layer formed by nickel-phosphorus plating is formed on a compression chamber-side end face of a baseplate of another scroll and a surface of a spiral wall, a wall height of the spiral wall of the other scroll is higher than a wall height of the spiral wall of the one scroll, and the first coating layer at the tip of the spiral wall of the one scroll and the second coating layer of the baseplate of the other scroll are separated from each other, and the first coating layer of the baseplate of the one scroll and the second coating layer at the tip of the spiral wall of the other scroll are in contact with each other.

A scroll compressor includes a compressor housing containing an orbiting scroll member, a non-orbiting scroll member, bands disposed between the non-orbiting scroll member and the compressor housing, a suction chamber, a discharge chamber, and one or more intermediate injection chamber defined by the bands. The non-orbiting scroll member includes one or more intermediate injection ports fluidly connecting the one or more intermediate injection chambers to at least one compression pocket formed by the intermeshed scroll members. A heating, ventilation, air conditioning, and refrigeration system includes a refrigerant circuit with a condenser, an expander, an evaporator, and the scroll compressor fluidly connected. A method of making a scroll compressor includes placing an upper portion of a compressor housing over a non-orbiting scroll member with bands disposed therebetween, and interference fitting the upper portion onto the non-orbiting scroll member via the bands.

A first coating layer formed by tin plating is formed on a compression chamber-side end face of a baseplate of one scroll and a surface of a spiral wall, a second coating layer formed by nickel-phosphorus plating is formed on a compression chamber-side end face of a baseplate of another scroll and a surface of a spiral wall, a wall height of the spiral wall of the other scroll is higher than a wall height of the spiral wall of the one scroll, and the first coating layer at the tip of the spiral wall of the one scroll and the second coating layer of the baseplate of the other scroll are separated from each other, and the first coating layer of the baseplate of the one scroll and the second coating layer at the tip of the spiral wall of the other scroll are in contact with each other.