Air cycle system with variable mix recuperator

Abstract

An open air cycle machine includes a compressor, a pair of heat exchangers, an expander, and a bypass system that can selectively recirculate the expanded, cooled airflow prior to entering the compartment being cooled. One of the heat exchangers is regenerative, and the bypass system directs the expanded airflow through the regenerative heat exchanger to further cool the compressed airflow prior to entering the expander. The bypass system includes a bypass duct and a mixer, and the mixer has a valve and a controller.

1 . An air cycle system for providing a conditioned airflow to a compartment having at least one inlet and at least one outlet, comprising: 
 a supply duct for fluidly communicating with the inlet;    a return duct for fluidly communicating with the outlet;    a compressor in fluid communication with said return duct;    a first heat exchanger in fluid communication with said compressor;    a second heat exchanger in fluid communication with said first heat exchanger;    an expander in fluid communication with said second heat exchanger;    a bypass duct downstream of said expander and in fluid communication with said compressor via a counter-path through said second heat exchanger;    a valve in fluid communication with said bypass duct via a first route and in fluid communication with said supply duct via a second route.    
   
   
       2 . The air cycle system of  claim 1 , wherein said return duct is in fluid communication with said compressor via said counter-path through said second heat exchanger.  
   
   
       3 . The air cycle system of  claim 1 , wherein said return duct is in fluid communication with said compressor directly from the outlet.  
   
   
       4 . The air cycle system of  claim 1 , wherein said valve routes a portion of the airflow to said supply duct and a portion of the airflow to said bypass duct.  
   
   
       5 . The air cycle system of  claim 1 , wherein said valve selectively routes all of the airflow to one of said bypass duct and said supply duct.  
   
   
       6 . The air cycle system of  claim 1 , wherein said controller selects between said first route and said second route based on at least one operating condition.  
   
   
       7 . The air cycle system of  claim 1 , wherein said controller selects between said first route and said second route based on a plurality of operating conditions.  
   
   
       8 . The air cycle system of  claim 1 , wherein said bypass duct is in fluid communication with the return duct through said valve.  
   
   
       9 . The air cycle system of  claim 1 , further comprising a water separator between said second heat exchanger and said expander and a motor for powering said compressor, wherein said expander is connected to said motor and provides work back to said motor.  
   
   
       10 . The air cycle system of  claim 1 , further comprising a controller connected to said valve, said controller operating said valve to select from at least one of said first route and said second route.  
   
   
       11 . An air cycle system, comprising: 
 a compartment having at least one inlet and at least one outlet;    a supply duct for fluidly communicating with said inlet;    a return duct for fluidly communicating with said outlet;    a compressor in fluid communication with said return duct;    a first heat exchanger in fluid communication with said compressor;    a second heat exchanger in fluid communication with said first heat exchanger;    an expander in fluid communication with said second heat exchanger; and    a bypass system between said expander and said supply duct and in fluid communication with said compressor via a counter-path through said second heat exchanger.    
   
   
       12 . The air cycle system of  claim 11 , wherein said bypass system comprises a bypass duct and a mixer having a valve and a controller, wherein said valve has a first route in fluid communication with said bypass duct and a second route in fluid communication with said supply duct and wherein said controller operates said valve to select from at least one of said first route and said second route.  
   
   
       13 . The air cycle system of  claim 12 , wherein said valve routes a portion of the airflow to said supply duct and a portion of the airflow to said bypass duct.  
   
   
       14 . The air cycle system of  claim 12 , wherein said bypass duct is in fluid communication with the return duct by a third route through said valve.  
   
   
       15 . The air cycle system of  claim 14 , wherein said controller selects between said routes and based on at least one operating condition.  
   
   
       16 . The air cycle system of  claim 11 , wherein said return duct is in fluid communication with said compressor via at least one of said counter-path through said second heat exchanger and directly from said outlet.  
   
   
       17 . The air cycle system of  claim 11 , wherein said valve selectively routes all of the airflow to one of said bypass duct and said supply duct.  
   
   
       18 . The air cycle system of  claim 11 , further comprising a water separator between said second heat exchanger and said expander and a motor for powering said compressor.  
   
   
       19 . An improved open air cycle system comprising a supply duct, a return duct, a compressor in fluid communication with said return duct, an ambient first heat exchanger in fluid communication with said compressor, a regenerative heat exchanger in fluid communication with said ambient heat exchanger, and an expander in fluid communication with said regenerative heat exchanger, wherein the improvement comprises: 
 a bypass system between said expander and said supply duct and in fluid communication with said compressor via a counter-path through said second heat exchanger.    
   
   
       20 . The open air cycle system of  claim 19 , wherein said bypass system comprises a bypass duct and a mixer having a valve and a controller, wherein said valve has a first route in fluid communication with said bypass duct and a second route in fluid communication with said supply duct and wherein said controller operates said valve to select from at least one of said first route and said second route.  
   
   
       21 . The open air cycle system of  claim 19 , wherein said return duct further comprises an ambient port with a flow control device.  
   
   
       22 . The open air cycle system of  claim 21 , wherein said flow control device is comprised of a flapper valve, wherein said compressor to pulls air from an ambient environment through said flapper valve.