Bootstrap systems

Aircraft air conditioning systems often use the work of expansion to assist the compression process in what is termed a 'bootstrap' system. In this case two-stage compression is used with one stage driven entirely by the expander power and the other by an external power source. 

If the machinery used in the compressor and expander were compatible with an external power source, such as a high-speed electric motor, a single shaft could be used to combine power from the expansion turbine and motor, and deliver it to the compressor in what is known as a 'powered-bootstrap' system (see below). Suitable high-speed switched reluctance electric motors are now available, and have been used for some air cycle systems with duties up to 40kW. 

 
Click on icon to down load schematic of a boot-strap system. 
 
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