Compressor

Abstract

A dry-compressing compressor comprises two screw rotors in a housing defining a suction chamber. At a compressor inlet of the compressor preferably atmospheric pressure prevails and at a compressor outlet of the compressor preferably a pressure of more than 2 bars (absolute) prevails. For each screw rotor at least one displacement element including a helical recess defining a plurality of windings is provided. The at least one displacement element per screw rotor has a single-pass asymmetrical profile.

What is claimed is: 
     
         1 . A dry-compressing compressor comprising
 a housing defining a suction chamber and having a compressor inlet where preferably atmospheric pressure prevails and a compressor outlet where preferably a pressure of at least 2 bars (absolute), preferably at least 5 bars (absolute) prevails,   two screw rotors arranged in the suction chamber and each having at least one displacement element including a helical recess for defining a plurality of windings,   wherein at least one displacement element per screw rotor has a single-pass asymmetrical profile,   the screw rotors have no internal cooling of the rotors, and   the housing has a mean heat flow density of less than 80000 W/m 2  in the area of the displacement elements.   
     
     
         2 . The dry-compressing compressor according to  claim 1 , wherein the profiles are configured such that not blowhole is formed. 
     
     
         3 . The dry-compressing compressor according to  claim 1 , wherein the profiles of the at least one displacement element of each screw rotor are configured a Quimby profile. 
     
     
         4 . The dry-compressing compressor according to  claim 1 , wherein a displacement element arranged near the outlet of the vacuum pump has symmetrical profile. 
     
     
         5 . The dry-compressing compressor according to  claim 1 , wherein at least one displacement element per screw rotor and/or in the case of a plurality of displacement elements per screw rotor said displacement elements jointly comprise a number (n) of windings which is larger than the ratio of outlet pressure (p out ) to inlet pressure (p in ) such that 
       
         
           
             
               n 
               > 
               
                 Pout 
                 Pin 
               
             
           
         
         
           
             preferably 
           
         
         
           
             
               n 
               > 
               
                 
                   Pout 
                   Pin 
                 
                 + 
                 4. 
               
             
           
         
         
           
             
               applies 
               . 
             
           
         
       
     
     
         6 . The dry-compressing compressor according to  claim 1 , wherein the installed volume ratio between the delivery volume of the inlet stage (V in ) and the outlet stage (V out ) is adapted to the pressure ratio between inlet pressure (p in ) and outlet pressure (p out ) such that the following applies: 
       
         
           
             
               
                 V 
                 i 
               
               = 
               
                 
                   Vin 
                   Vout 
                 
                 = 
                 
                   
                     ( 
                     
                       Pout 
                       Pin 
                     
                     ) 
                   
                   
                     1 
                      
                     
                       / 
                     
                      
                     k 
                   
                 
               
             
           
         
         wherein n has a value of k−0.3 to k+0.3 and k is the isotropic exponent of the gas mixture to be delivered. 
       
     
     
         7 . The dry-compressing compressor according to  claim 1 , wherein the displacement elements include at least one area where the volume of the inlet stage (V in ) decreases to a precompression volume (V VK ) in a small rotation angle range, wherein the ratio between inlet volume (V in ) and the volume of the precompression (V VK ) is related to the internal volume ratio (v i ) of the compressor 
       
         
           
             
               
                 v 
                 VK 
               
               = 
               
                 
                   Vin 
                   Vout 
                 
                 = 
                 
                   
                     ( 
                     
                       v 
                       i 
                     
                     ) 
                   
                   
                     1 
                      
                     
                       / 
                     
                      
                     j 
                   
                 
               
             
           
         
       
       wherein j=2 to 5. 
     
     
         8 . The dry-compressing compressor according to  claim 7 , wherein the compression from the inlet volume (V in ) to the precompression volume (V VK ) takes place during one and a half to three rotor revolutions (windings). 
     
     
         9 . The dry-compressing compressor according to  claim 1 , wherein at least one displacement element per screw rotor and/or in the case of a plurality of displacement elements per screw rotor said displacement elements jointly have a ratio of length (L) to diameter (D) for which the following applies 
       
         
           
             
               
                 L 
                 D 
               
               > 
               
                 
                   Pout 
                   
                     2 
                      
                     Pin 
                   
                 
                 - 
                 2 
               
             
           
         
         
           
             
               and 
                
               
                   
               
                
               in 
                
               
                   
               
                
               particular 
             
           
         
         
           
             
               
                 L 
                 D 
               
               > 
               
                 
                   Pout 
                   
                     2 
                      
                     Pin 
                   
                 
                 - 
                 1 
               
             
           
         
       
     
     
         10 . The dry-compressing compressor according to  claim 1 , wherein the pitch of the windings of the displacement elements varies, preferably changes and particularly preferably decreases from the compressor inlet to the compressor outlet. 
     
     
         11 . The dry-compressing compressor according to  claim 1 , wherein the head and the foot diameter of the rotor preferably continuously changes, wherein the rotor is in particular of a conical configuration. 
     
     
         12 . The dry-compressing compressor according to  claim 1 , wherein the pressure ratio 
       
         
           
             
               Pout 
               Pin 
             
           
         
       
       between outlet and inlet pressure is at least 5. 
     
     
         13 . The dry-compressing compressor according to  claim 1 , wherein two screw rotors with parallel axes are provided. 
     
     
         14 . The dry-compressing compressor according to  claim 1 , wherein at the compressor inlet in particular inside the housing a gas collection chamber is provided. 
     
     
         15 . The dry-compressing compressor according to  claim 1 , wherein at the compressor outlet a gas collection chamber is provided in particular inside the housing. 
     
     
         16 . The dry-compressing compressor according to  claim 1 , wherein in the housing roller bearings and preferably seals are arranged on both sides of the two screw rotors. 
     
     
         17 . The dry-compressing compressor according to  claim 1 , wherein for synchronizing the two screw rotors a synchronization gear is provided. 
     
     
         18 . The dry-compressing compressor according to  claim 1 , wherein the speed of the screw rotors is higher than 
       
         
           
             
               
                 3 
                  
                 
                   , 
                 
                  
                 000 
                  
                 
                     
                 
                  
                 
                   1 
                   min 
                 
               
               , 
             
           
         
       
       
         
           
             
               
                 1 
                 min 
               
               , 
             
           
         
       
       
         
           
             
               
                 1 
                 min 
               
               . 
             
           
         
       
     
     
         19 . The dry-compressing compressor according to  claim 1 , wherein the one displacement element is configured as a discharge-side displacement element and for each screw rotor at least one further displacement element is provided. 
     
     
         20 . The dry-compressing compressor according to  claim 1 , wherein between an upper surface of the displacement element and an inner surface of the suction chamber a gap with a height of 0.03 mm to 0.2 mm is formed. 
     
     
         21 . The dry-compressing compressor according to  claim 1 , wherein the suction-side displacement elements have a constant pitch along their overall length. 
     
     
         22 . The dry-compressing compressor according to  claim 1 , wherein each screw rotor comprises a rotor shaft supporting the at least one displacement element. 
     
     
         23 . The dry-compressing compressor according to  claim 1 , wherein the displacement elements of a screw rotor are of an integral configuration. 
     
     
         24 . The dry-compressing compressor according to  claim 1 , wherein the screw rotors and in particular the at least one displacement element per screw rotor have a smaller expansion coefficient that the housing, wherein the expansion coefficient of the housing is in particular at least larger than that of the screw rotors and/or the at least one displacement element. 
     
     
         25 . The dry-compressing compressor according to  claim 1 , wherein the screw rotors do not comprise any ducts through which in particular a liquid coolant flows. 
     
     
         26 . The dry-compressing compressor according to  claim 1 , wherein the screw rotors are of a solid configuration. 
     
     
         27 . The dry-compressing compressor according to  claim 1 , wherein a temperature difference in the area of the discharge-side displacement elements between the latter and the housing during normal operation is smaller than 50 K. 
     
     
         28 . The dry-compressing compressor according to  claim 1 , wherein the distance between the area where 5 ° A) to 20% of the outlet pressure prevails and the last winding of the discharge-side displacement element is at least 20% to 30% of the rotor length. 
     
     
         29 . The dry-compressing compressor according to  claim 1 , wherein a gap between the edges of at least one of the displacement elements preferably has a gap height of 0.1 to 0.3 mm.