Screw compressor-expander machine

Abstract

A plural screw compressor-expander machine has a casing ( 10 ) in the interior of which are mounted intermeshing helical rotors ( 11 and 12 ). The rotors ( 11 and 12 ) are supported at each end in bearings in the end walls of the casing. The interior of the casing is divided by a transverse partition ( 14 ) into a relatively longer compressor portion ( 1 ) and a shorter expander portion ( 5 ). The higher pressure ports ( 16, 18 ) of the compressor and expander portions are adjacent the partition, on opposite sides of a plane through the rotor axes. Similarly, the lower pressure ports ( 15, 17 ) are on opposite sides of the plane through the rotor axes but adjacent the end walls. This arrangement reduces the loads on the bearings of the rotors.

1 . a plural-screw expander-compressor machine comprising intermeshing first and second helically-profiled rotors mounted for rotation in opposite directions in a housing by means of bearings at the opposite ends of the rotors, the interior of the housing being divided by a transverse partition into a compressor portion and an expander portion, the rotors extending through the partition and having circularly profiled portions where they extend through the partition, the two housing portions each having a higher pressure port and a lower pressure port, the higher pressure ports being adjacent the partition and on opposite sides of the rotors.  
   
   
       2 . A machine according to  claim 1 , wherein the compressor portions of the rotors have the same profile as the expander portions thereof.  
   
   
       3 . A machine according to  claim 1 , wherein helical lobes of the first rotor make sealing contact on both sides with the second rotor.  
   
   
       4 . A machine according to  claim 1  wherein the partition extends into an annular groove of each rotor.  
   
   
       5 . A refrigeration system comprising an evaporator, a cooler or condenser and a machine according to any preceding claim, the compressor portion being connected to deliver refrigerant from the evaporator under increased pressure to the cooler or condenser and the expander portion being connected to receive refrigerant from the cooler or condenser and to deliver it at reduced pressure to the evaporator.  
   
   
       6 . A system according to  claim 5  and including a mechanical power connection to drive the machine or take power therefrom.  
   
   
       7 . (canceled)  
   
   
       8 . A plural-screw compressor-expander machine comprising intermeshing first and second helically-profiled rotors mounted for rotation in opposite directions in a housing, the housing defining an expansion chamber and a compressor chamber, the rotors extending through both chambers, the chambers being separated and each having an inlet and an outlet, one of the rotors having a connection for supplying or taking off mechanical power.  
   
   
       9 . A fuel-cell installation comprising at least one fuel cell, a supply of pressurised fuel for the fuel-cell, a plural-screw expander-compressor machine comprising intermeshing first and second helically-profiled rotors mounted for rotation in opposite directions in a housing by means of bearings at the opposite ends of the rotors, the interior of the housing being divided by a transverse partition into a compressor portion and an expander portion, the rotors extending through the partition and having circularly profiled portions where they extend through the partition, the two housing portions each having a higher pressure port and a lower pressure port, the compressor portion of the machine being connected to deliver compressed air to the fuel-cell or cells and the expander portion of the machine being connected to receive pressurised exhaust from the fuel-cell or cells.  
   
   
       10 . A fuel-cell installation comprising at least one fuel cell, a plural-screw expander-compressor machine comprising intermeshing first and second helically-profiled rotors mounted for rotation in opposite directions in a housing by means of bearings at the opposite ends of the rotors, the interior of the housing being divided by a transverse partition into a compressor portion and an expander portion, the rotors extending through the partition and having circularly profiled portions where they extend through the partition, the two housing portions each having a higher pressure port and a lower pressure port, the higher pressure ports being adjacent the partition and on opposite sides of the rotors, the compressor portion of the machine for supplying air under pressure to the fuel-cell or cells for expanding exhaust gas from the fuel-cell installation.