"A secondary flow (turbine drive gases) is exhausthed throug the nozzle base and adds to the recirculating flow to increase the base pressure and the overall nozzle efficiency."
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/1998017...
Had to curl it, since pdf.js always froze before loading it. For some reason the column layout is broken so quoting the text required quite a lot of hand editing.