The invention pertains to a screw compressor with two screw rotors that are rotatably held in a rotor housing with parallel axes, each of which has a profile section with screw-shaped ribs and grooves. The ribs and grooves of the rotors mesh together, forming a seal, and the gas volumes contained between them and the rotor housing are conveyed and compressed when the rotors are operated.
In screw rotors of this type, the design of the profiles has until now focused on creating the largest possible volumes for the gas to be compressed, located between the rotors and the rotor housing, relative to a given outer rotor profile diameter. In other words, as high a rotor profile volumetric utilization as possible has been sought.
In contrast, the aim of the present invention is to provide a screw compressor that is suitable for the compression of gas to very high pressures, typically in the 30 to 50 bar range, and that can be operated primarily as the last stage of a multi-stage compressor system, in particular a three-stage compressor system. At such high pressures, the rotors are subjected to high lateral forces that act to bend the rotors away from each other due to the gas volume contained between them and the housing under high pressure. This can negatively affect the seal between the rotors, and thus to a loss of efficiency. Also, due to the separation of the rotors, the radial gap between the rotors and the rotor housing can not be as tightly toleranced as desirable to attain a good seal and a high efficiency.
Thus, the object of the invention is to provide a screw compressor that is suitable primarily for operation at high compressive pressures. The solution to this objective is indicated in claim 1. The dependent claims refer to further advantageous embodiments of the invention.
It was found that the design of the rotors indicated in the claims leads to an especially favorable relationship between the bending stiffness of the rotors on one hand and the volume of the contained compressed gas, which creates the bending forces, in the screw notches of the rotors on the other.
One embodiment of the invention is explained in more detail below with the help of the drawings. Shown are:
The screw compressor shown as an exemplary embodiment in
The upper rotor 3 in
The screw compressor described is preferred to be a “dry-running” compressor, i.e. in which no lubricating, cooling or sealing oil is fed to the compression chamber. Despite this fact, the rotor profiles mesh with one another without touching and form a seal nevertheless. This is an advantage for all applications in which the compressed gas must be completely free of oil. Oil is only fed external to the compression chamber, i.e. outside the zone sealed off by the seals 11. The oil is used to lubricate the drive gear (not shown), the bearings 13, 15 and the synchronizing transmission 17, 19.
In
Furthermore,
This is not larger, and is preferably smaller than 0.15 times the diameter Da of the outer circle Ka. The same applies to the eight ribs 9′ and the grooves 9″ separating them for the lower rotor (secondary rotor) 9, i.e. the tooth height H is also not larger than 0.15 times the outer profile diameter Da in this case.
As the screw compressor shown in
Number | Date | Country | Kind |
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10 2005 058 698.8 | Dec 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/005556 | 6/9/2006 | WO | 00 | 5/20/2008 |