Turbine cooling air from a centrifugal compressor

A gas turbine engine turbine cooling system (137) includes an impeller (32) and a diffuser (42) directly downstream of the impeller (32), a bleed for bleeding clean cooling air (97) from downstream of the diffuser (42), and one or more channels (150) in fluid communication with the bleed. Each of the channels (150) having a generally radially extending section (162) followed by a generally axially aftwardly extending section (163) terminating at an annular cooling air plenum (164) connected to accelerators (165). The radially and axially aftwardly extending sections (162, 163) may be connected by a bend section (173) of the cooling air channel (150) and the axially aftwardly extending section (163) may be angled radially inwardly going from the bend section (173) to the cooling air plenum (164). Each of the cooling channels (150) includes an inner wall (152) formed by a forward end wall (96) extending radially outwardly from an inner combustor casing (47), an annular cover (120) covering a radially inner portion (108) of the forward end wall (96), and the inner combustor casing (47).