US Patent 11988098 Increasing surge margin and compression efficiency via shaft power transfer

In a gas turbine engine of the type having a high-pressure (HP) spool and a low-pressure (LP) spool, methods of increasing surge margin and compression efficiency at a given thrust are provided. One method increases compression efficiency and includes transferring mechanical power from the HP spool to the LP spool to reduce a corrected speed of a HP compressor therein and raise a working line of a LP compressor therein. Another method increases surge margin and includes transferring mechanical power from the LP spool to the HP spool to increase a corrected speed of a HP compressor therein and lower a working line of a LP compressor therein.