Adaptive engine with boost spool

A gas turbine engine comprising:

• a first spool comprising a first compressor rotationally driven by a first turbine via a first shaft;
• a first primary combustor;
• a first diffuser having walls that diverge towards the first primary combustor, wherein the first compressor, the first diffuser, and the first primary combustor are arranged in series to provide a compressed airflow discharged from the first compressor to the first primary combustor via the first diffuser;
• a boost spool comprising a boost compressor rotationally driven by a boost turbine via a boost shaft;
• a secondary combustor disposed downstream from the boost compressor and upstream from the boost turbine;
• a plurality of inlet ducts fluidly coupling the first diffuser to the boost compressor of the boost spool;
• a plurality of outlet ducts fluidly coupling the boost turbine to the first diffuser;
• and
• a plurality of struts circumferentially spaced within the first diffuser, each strut extending from a radially inner wall of the first diffuser to a radially outer wall of the first diffuser;
• wherein:
• the boost compressor is fluidly coupled to the first diffuser to receive at least a portion of the compressed airflow from the first diffuser;
• the boost compressor, the secondary combustor, and the boost turbine are arranged in series to provide a compressed boost airflow discharged from the boost compressor to the secondary combustor and a combusted boost airflow from the secondary combustor to the boost turbine;
• the boost turbine is fluidly coupled to the first diffuser to discharge an expanded airflow to the first diffuser;
• and
• each outlet duct of the plurality of outlet ducts has a discharge area, and wherein the discharge areas are circumferentially distributed between the radially inner wall and the radially outer wall of the first diffuser and formed by one of the struts, such that the expanded airflow from the boost turbine and the compressed airflow from the first compressor are mixed within the first diffuser.