Compressor for co2 cycle with at least two cascade compression stages for assuring supercritical conditions

Abstract

The compressor is used for processing a CO2 flow; a first compressor stage has a first row of blades with a first number of blades and a second compressor stage, downstream the first compressor stage, has a second row of blades with a second number of blades; the number of blades of the first compressor stage is less than the number of blades of the second compressor stage; there is an annular gap between the first row of blades and the second row of blades; the first compression stage is designed so to assure that the CO2 flow is in supercritical condition, preferably close to CO2 critical point, at its outlet, and so that the second compressor stage process CO2 in supercritical condition.

What is claimed is: 
     
         1 . A method for compressing a CO2 flow using a compressor, comprising:
 a first compression step for compressing the CO2 flow to a supercritical condition through a first compressor stage so to generate a supercritical CO2 flow;   a second compression step for compressing the supercritical CO2 flow through a second compressor stage;   wherein the first compression step is such that, at the end of compression, CO2 is close to critical point (Pc, Tc);   wherein between the first compression step and the second compression step there is an isoenthalpic step that maintains substantially constant both total pressure and static pressure.   
     
     
         2 . The method of  claim 1 , wherein the first compression step is such that, at the end of compression, thermodynamic state point of CO2, on a T-s diagram, is located outside the saturation dome, approximately near CO2 critical point (Pc, Tc). 
     
     
         3 . The method of  claim 2 , wherein at the end of the first compression step, the pressure is equal or higher than saturation pressure plus a predetermined pressure margin, the pressure margin being related to pressure drop inside the second rotary compressor stage. 
     
     
         4 . The method of  claim 1 , wherein the first compression step is followed by one or more compressing steps of compressing CO2 flow. 
     
     
         5 . The method of  claim 1 , wherein the first compression step has a pressure ratio smaller than the second compression step. 
     
     
         6 . A method of compressing a fluid, comprising:
 in a compressor,
 providing a rotor having a first row of blades and a second row of blades spaced axially apart from the first set of blades to create a gap; 
 directing the fluid through the first row of blades; 
 directing the fluid from the first row of blades across the gap; and 
 directing the fluid from the gap through the second row of blades after the gap. 
   
     
     
         7 . The method of  claim 6 , wherein the first row of blades is at a different circumferential position than the second row of blades. 
     
     
         9 . The method of  claim 6 , wherein the trailing edge of the first row of blades is circumferentially offset from the leading edge of the second row of blades. 
     
     
         10 . The method of  claim 6 , wherein the trailing edge of the first row of blades and the leading edge of the second row of blades are not axially aligned. 
     
     
         11 . The method of  claim 6 , wherein the gap resides between the trailing edge of the first row of blades and the trailing edge of the second row of blades. 
     
     
         12 . The method of  claim 6 , wherein the gap has a length that is at least equal to a height of a leading edge of the first row of blades. 
     
     
         13 . The method of  claim 6 , wherein the gap has a length that is less than two times a height of a leading edge of the first row of blades. 
     
     
         14 . The method of  claim 6 , wherein the rotor has twice as many blades in the second row as the first row. 
     
     
         15 . A method, comprising:
 compressing a fluid by,
 directing a flow of fluid across an inducer type blade found on a rotor in a compressor; and 
 then, directing the flow of fluid across an exducer type of blade found on the rotor downstream of the inducer type of blade, 
   wherein the flow of fluid transits a gap after exiting the inducer type of blade and before entering the exducer type of blade.   
     
     
         16 . The method of  claim 15 , wherein the gap has a length that at least equal to a height of a leading edge of the inducer type of blade. 
     
     
         17 . The method of  claim 15 , wherein the gap has a length that is less than two times a height of a leading edge of the inducer type of blade. 
     
     
         18 . The method of  claim 15 , wherein the inducer type of blade and the exducer type of blade are circumferentially offset from one another. 
     
     
         19 . The method of  claim 15 , wherein the inducer type of blade has a trailing edge that is circumferentially offset from a leading edge of the exducer type of blade. 
     
     
         20 . The method of  claim 15 , further comprising:
 directing the flow of fluid through inlet guide vanes found upstream of the inducer type of blades.