Abstract: A rotary screw compressor for oil-free air, wherein at least one of the shaft journals (11) of the rotors (10) has a seal arrangement between the rotor (10d) and an oil-lubricated bearing (12). The seal arrangement includes at least three frictionless seals (13, 14, 15) separated by annular chambers (16,17). The outermost annular chamber (17) is connected to a source of pressurized air through a supply channel (19) for supplying blocking air to the seal, and another (16) of the annular chambers communicates with a withdrawal channel (18).

Abstract: The invention relates to a method for achieving an optimal energy exchange in regenerative heat exchange between the combustion air and precooled, wet flue gases from a cooling device. By letting the moisture in said flue gases be condensed on the heat transfer surfaces the moisture will be transferred over to the air side where it is vaporized, resulting in some advantages, e.g. an increased energy exchange. According to the invention it has turned out to be possible to achieve a further increase of the energy exchange in a simple way by ensuring that the heat transfer surfaces of the flue gas side become really water-soaked when on the flue gas side, e.g. by letting the condensed water from the precooling device (15) drip or flow down onto the heat transfert surfaces such that said surfaces will remain wet during the entire passage through the combustion air side (10).

Abstract: In a rotary screw machine, a shaft journal (7) of one of the rotors (6) is mounted in main thrust bearings (9, 10) and a balancing thrust bearing (11 ), the latter being located outermost on the shaft journal (7). The main thrust bearings (9, 10) are clamped towards the low pressure end of the machine. The balancing thrust bearing (11) is affected by a thrust balancing device for counter-acting the gas forces on the rotor (6), thereby reducing the force that has to be transferred by the main thrust bearing.

Abstract: A rotary displacement compressor has an adjustable regulator (22) which determines the internal volume ratio of the compressor. The regulator (22) is adjusted in response to the sound level of a sound of compressed working medium, which is sensed by a sound sensor (26) located adjacent to the outlet port (20 ) of the compressor.

Abstract: A rotor for a rotary screw machine has helical lobes (12) and grooves (14). A shell structure (18) forming the external surface of the rotor is made of pressed metal power. The rotor is manufactured by cold isostatic pressing of a powder in a vessel having a surface shaping rotor. The pressure is applied radially by means of a cast bag in which high pressure liquids acts. After the pressing process, the rotor blank is sintered and attached to a shaft (16).

Abstract: The invention relates to a rotary screw machine in which the shaft journals (20, 22) of the rotors (10) are journalled in a main thrust bearing (24) and a thrust balancing bearing (26). The thrust balancing bearing (26) is preloaded by springs (36) and by fluid pressure means (40, 44). According to the invention the fluid pressure means (40, 44) can excert a force on the thrust balancing bearing (26) in either axial direction. This increases the possibility for an optimal distribution of the forces on the thrust bearings (24, 26) at various running conditions.

Abstract: A method of manufacturing rotors having helical lands and intermediate grooves wherein a multi-layer rotor body (2) is moulded or otherwise formed on a shaft (1) to only a small degree of accuracy, whereafter an outer layer (3) of polymer-based material is moulded on the rotor body to a high degree of accuracy. For the purpose of eliminating shrinkage-induced distortion of the lands of the rotor body (2) subsequent to applying the outer layer, the rotor body is produced in a multiple of layers (21, 22), by casting or like moulding processes, with each of the body layers having a thickness which is greater than that of the high accuracy outer layer (3).

Abstract: The invention relates to a machine of the rotary screw type for a gaseous medium having a compression section and an expansion section driving the compression section. According to the invention both the compression section and the expansion section are located in one single working space in which two rotors (14, 16) operate. The machine has a low pressure port (32), a high pressure port (30) and intermediate pressure port means (34).

Abstract: A screw rotor machine which incorporates a sound silencing device in the vicinity of the inlet and/or outlet port. The sound silencing device comprises a De Laval nozzle (8) having a valve body (9) which is movable axially in relation to the nozzle. When the machine is shut-down, the valve body (9) lies sealingly against the opening (8A) of the nozzle. When increasing the capacity of the machine to full load, the valve body (9) moves in the opening direction under the influence of a damping force and against the action of a substantially constant spring force (14), so as to maintain a flow rate immediately beneath the sound of speed in the smallest area (8A) of the nozzle (8).

Abstract: The invention relates to a rotary screw compressor with liquid-injection means. The axes of the rotors (18, 20) are in a horizontal plane and the inlet channel (26) reaches the compressor from below. According to the invention there are provided means for preventing that liquid leaking out from the working space of the compressor through the inlet port (46) reaches the inlet channel (26). These means include partition walls (34, 36) mounted in an inlet chamber (28) connecting the inlet channel (26) to the inlet port (46).

Abstract: The rotary positive displacement compressor has an intermediate port (42) for fluid from an intermediate pressure channel (30) and has a bleed port (44) for recirculation of partly compressed fluid through a return channel (32). It is suggested to provide the compressor with valve means (36), selectively adjustable between two end positions. In a first end position it opens up a direct communication between these channels (30, 32) and opens the bleed port (44), whereby fluid flows directly from the intermediate pressure channel (30) to the return channel (32) simultaneously as fluid within the working space of the compressor flows to the return channel (32) through the intermediate port (42) as well as through the bleed port (44). In a second end position the bleed port (44) is closed and said direct communication is blocked. The disclosure also relates to a refrigeration plant comprising such a compressor.

Abstract: The invention relates to a pressure actuated lift valve in a rotary screw machine mounted in one of the end walls of the machine, e.g. for the purpose of controlling the built-in volume ratio of the machine. The valve contains a cylindrical valve member 11 displaceable in an axial boring 13 and an actuating piston 12 in a cylinder 14. The boring 13 extends between the working space 24 of the machine and said cylinder 14. Through channels 20, 21, 22 pressure fluid is supplied to the cylinder 14 whereby the actuating piston 12 affects the valve member 11 to take an open or a closed position.By making the actuating means as a unit separate from the valve member 11 the manufacture is facilitated.

Abstract: A rotary screw compressor has meshing male (2) and female (4) rotors operating in a working space limited by a high pressure end section (6), a low pressure end section (8) and a barrel section extending therebetween. The rotors (2, 4) have shaft extensions (22, 24, 26, 28) journalled in bearings (30, 32, 34, 36) in the end sections (6, 8). Oil is supplied to the bearing chambers (38, 40, 42, 44) for lubricating and cooling the bearings. The chambers (42, 44) in the low pressure end section (8) are drained to the working space through a first channel (50) and a first opening (52) in the walls (16) of the working space, and the chambers (38, 40) in the high pressure end section (6) are drained to the working space through a second channel (46) and a second opening (48) in the walls (16) of the working space.

Abstract: The invention relates to a rotary displacement compressor having volume ratio regulation. A connection channel (8,9,10) connects the working space of the compressor to the pressure channel (5). In the channel (8,9,10) there is provided means (13) for sensing the direction of flow through the channel. The direction of flow is an indication of whether there is over or under compression. Signals from the flow direction sensing means (13) affect the position of a movable edge (29) of the outlet port (32) so that this edge (29) will move to a position where the internal compression complies with the outlet pressure. By using the direction of flow as the governing parameter for the volume ratio regulation instead of the pressure difference or the power consumption of the prime mover according to known technique, a more accurate adaption of the volume ratio to the outlet pressure is achieved.

Abstract: A rotor for a rotary screw machine having helical lobes and intermediate grooves, the rotor having a core including a shaft 1 of a first material and a rotor body 2 of a second material mounted on the shaft. The surface of the rotor is coated with a plastic layer 3.

Abstract: A screw rotor machine comprises a pair of intermeshing rotors (3) having helical lands and intervening grooves and a casing with a working space generally comprised of two intersecting bores, each enclosing one of the rotors (3). Each rotor (3) has a cylindrical projection (9) passing through a hole (8) in an end wall (5) at the high pressure end of the machine into a bearing chamber. To prevent gas leakage from the working space to the bearing chamber there is provided an annular element (15; 23) surrounding each rotor projection (9) and non-rotatably fixed to the casing. The annular element is provided with one axial (19; 24) and one radial (20; 21) sealing surface, one surface (19; 21) cooperating with the casing and the other surface (20; 24) cooperating with the rotor projection (9) by a slight or zero contact force. The annular element (15; 23) is movable almost without friction in the direction of the contact force.

Abstract: A pack of heat transfer plates (2,3) are intended for heat exchangers, preferably for rotary regenerative air preheaters. The plates have mutually parallel S-shaped double ridges (21,22;31,32) and the plates are arranged in the pack (1) so that the double ridges of one plate intersect the double ridges of an adjacent plate and extend symmetrically and obliquely in mutually opposite directions relative to the main flow directions (6) of the heat exchanging media. The throttling effect normally manifest at the double-ridge intersections (24) is avoided by orienting the plates (2,3) so that each pair of double ridges which converge onto an intersection (24) presents a part (21) of the double ridge of the one plate (2) which projects into an intermediate channel, and also a part (32) of the double ridge of the other plate (3) which projects from the intermediate channel.

Abstract: A rotary screw compressor with a lift valve comprising a valve member having two rigidly connected cylindrical sections of different diameter. The valve member is displaceably mounted in a valve housing extending through the high pressure end wall of the compressor. The valve housing sealingly surrounds each of the cylindrical sections. The section of the smaller diameter and the corresponding part of the valve housing face the working space of the machine. The lift valve is mounted such that the direction of motion of the valve member is inclined relative to the axial direction of the compressor.

Abstract: A method for producing selectively controlled pressure pulses in a mass of gas, particularly contained in a space of large dimensions. To achieve a sufficiently high power in the pulses, the pulses are generated by a valveless displacement machine in which the pressure when the machine opens towards its outlet port differs from the pressure of the mass of gas. The pulse is generated as the working fluid, due to said pressure difference, flows at high velocity through the outlet port. An acoustic power of the generated pulses of up to 20 kW can be attained by the method. The invention also concerns a rotary displacement machine for performing the method.

Abstract: A housing (1) of a rotary machine comprises a low-pressure side (2) and a high-pressure side (3), working-fluid inlet and outlet channels, and at least one rotor (7), which when the machine is working is urged by a working fluid towards the low-pressure side (2). The rotor includes a thrust balancing arrangement (15, 16) for relieving the load on the thrust bearings (11) of the machine, through the medium of an auxiliary bearing (17) and in dependence on pressure fluid supplied to the thrust balancing arrangement, the pressure of which fluid is contingent on the operating conditions of the machine. A relatively large part of the axial load is taken-up by an auxiliary thrust bearing (17), which is readily replaceable. The auxiliary bearing (17) is mounted on an outermost part of the rotor journal shaft (18), on the high-pressure side (3) of the rotor, between a detachable locking device (27) for the auxiliary bearing (17) and the thrust balancing arrangement.