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A gas turbine engine centrifugal compressor axial forward thrust apparatus bleeds impeller tip aft bleed flow from between an annular centrifugal compressor impeller of a high pressure rotor and a diffuser directly downstream of the impeller. The apparatus then uses the aft bleed flow to pressurize

A gas turbine engine centrifugal compressor axial forward thrust apparatus bleeds impeller tip aft bleed flow from between an annular centrifugal compressor impeller of a high pressure rotor and a diffuser directly downstream of the impeller. The apparatus then uses the aft bleed flow to pressurize an annular cavity extending radially between an inner combustor casing and the rotor and extending axially between forward and aft thrust balance seals. Forward and aft thrust balance lands are in sealing engagement with the forward and aft thrust balance seals on the high pressure rotor respectively. An annular stator plenum in fluid communication with the annular cavity is bounded in part by a forward end wall having conical diffusion holes therethrough which may be axially or circumferentially or axially and circumferentially angled. The forward thrust balance seal may be on an aft conical arm of the impeller.

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1. A gas turbine engine centrifugal compressor axial forward thrust apparatus comprising: an annular centrifugal compressor impeller of a high pressure rotor,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and a diffuser directly downstream of the impeller,

1. A gas turbine engine centrifugal compressor axial forward thrust apparatus comprising: an annular centrifugal compressor impeller of a high pressure rotor,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and a diffuser directly downstream of the impeller,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between an inner combustor casing and the high pressure rotor and extending axially between a forward thrust balance seal on the impeller and an aft thrust balance seal and the forward thrust balance seal being located on an aft conical arm of the impeller of the rotor. 2. An apparatus as claimed in claim 1, further comprising: an annular stator plenum in fluid communication with the annular cavity,the annular stator plenum bounded in part by a forward end wall, andthe pressurizing means including conical diffusion holes in the forward end wall. 3. An apparatus as claimed in claim 2, further comprising the conical diffusion holes being axially or circumferentially or axially and circumferentially angled. 4. A gas turbine engine centrifugal compressor axial forward thrust apparatus comprising: an annular centrifugal compressor impeller of a high pressure rotor,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and a diffuser directly downstream of the impeller,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between an inner combustor casing and the high pressure rotor and extending axially between forward and aft thrust balance seals,an annular stator plenum in fluid communication with the annular cavity,the annular stator plenum bounded in part by a forward end wall,the pressurizing means including conical diffusion holes in the forward end wall, andangled metering holes in the inner combustor casing between the annular stator plenum and the annular cavity. 5. An apparatus as claimed in claim 4, further comprising the metering holes being circumferentially angled. 6. An apparatus as claimed in claim 1, further comprising a forward thrust balance land in sealing engagement with the forward thrust balance seal on a radially inner surface of the inner combustor casing and an aft thrust balance land in sealing engagement with the aft thrust balance seal. 7. A gas turbine engine centrifugal compressor axial forward thrust apparatus comprising: an annular centrifugal compressor impeller of a high pressure rotor,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and a diffuser directly downstream of the impeller,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between an inner combustor casing and the high pressure rotor and extending axially between forward and aft thrust balance seals,a forward thrust balance land in sealing engagement with the forward thrust balance seal on a radially inner surface of the inner combustor casing,an aft thrust balance land in sealing engagement with the aft thrust balance seal, andthe forward thrust balance seal located on an aft conical arm of the impeller of the rotor. 8. An apparatus as claimed in claim 7, further comprising: an annular stator plenum in fluid communication with the annular cavity,the annular stator plenum bounded in part by a forward end wall, andthe pressurizing means including conical diffusion holes in the forward end wall. 9. An apparatus as claimed in claim 8, further comprising the conical diffusion holes being axially or circumferentially or axially and circumferentially angled. 10. An apparatus as claimed in claim 8, further comprising angled metering holes in the inner combustor casing between the annular stator plenum and the annular cavity. 11. An apparatus as claimed in claim 10, further comprising the metering holes being circumferentially angled. 12. A gas turbine engine assembly comprising: a combustor between a high pressure compressor and a high pressure turbine,a high pressure rotor including a centrifugal compressor having an annular centrifugal compressor impeller directly adjacent to and upstream of a diffuser,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and the diffuser,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between the inner combustor casing and the high pressure rotor and extending axially between a forward thrust balance seal on the impeller and an aft thrust balance seal and the forward thrust balance seal being located on an aft conical arm of the impeller of the rotor. 13. An assembly as claimed in claim 12, further comprising: an annular combustor stator assembly including a forward end wall extending radially outwardly from and joined to the inner combustor casing,a radially outer portion of the forward end wall being an aft wall of the diffuser,a stator plenum disposed between and in fluid communication with the impeller and the annular cavity, andthe stator plenum being in part bounded by a radially inner portion of the forward end wall. 14. An assembly as claimed in claim 13, further comprising the pressurizing means including conical diffusion holes in the radially inner portion of the forward end wall. 15. An assembly as claimed in claim 14, further comprising the conical diffusion holes being axially or circumferentially or axially and circumferentially angled. 16. An assembly as claimed in claim 14, further comprising the stator plenum being bounded by the radially inner portion of the forward end wall and an annular cover spaced axially aftwardly of the radially inner portion of the forward end wall. 17. A gas turbine engine assembly comprising: a combustor between a high pressure compressor and a high pressure turbine,a high pressure rotor including a centrifugal compressor having an annular centrifugal compressor impeller directly adjacent to and upstream of a diffuser,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and the diffuser,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between the inner combustor casing and the high pressure rotor and extending axially between forward and aft thrust balance seals,an annular combustor stator assembly including a forward end wall extending radially outwardly from and joined to the inner combustor casing,a radially outer portion of the forward end wall being an aft wall of the diffuser,a stator plenum disposed between and in fluid communication with the impeller and the annular cavity,the stator plenum in part bounded by a radially inner portion of the forward end wall,the pressurizing means including conical diffusion holes in the radially inner portion of the forward end wall,the stator plenum being bounded by the radially inner portion of the forward end wall and an annular cover spaced axially aftwardly of the radially inner portion of the forward end wall, andangled metering holes in the inner combustor casing between the annular stator plenum and the annular cavity. 18. An assembly as claimed in claim 17, further comprising the metering holes being circumferentially angled. 19. An assembly as claimed in claim 12, further comprising a forward thrust balance land in sealing engagement with the forward thrust balance seal on a radially inner surface of the inner combustor casing and an aft thrust balance land in sealing engagement with the aft thrust balance seal. 20. A gas turbine engine assembly comprising: a combustor between a high pressure compressor and a high pressure turbine,a high pressure rotor including a centrifugal compressor having an annular centrifugal compressor impeller directly adjacent to and upstream of a diffuser,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and the diffuser,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between the inner combustor casing and the high pressure rotor and extending axially between forward and aft thrust balance seals,a forward thrust balance land in sealing engagement with the forward thrust balance seal on a radially inner surface of the inner combustor casing and an aft thrust balance land in sealing engagement with the aft thrust balance seal, andthe forward thrust balance seal being located on an aft conical arm of the impeller of the rotor. 21. An assembly as claimed in claim 20, further comprising an annular stator plenum in fluid communication with the annular cavity and bounded in part by a forward end wall and the pressurizing means including conical diffusion holes in the forward end wall. 22. An assembly as claimed in claim 21, further comprising the conical diffusion holes being axially or circumferentially or axially and circumferentially angled. 23. An assembly as claimed in claim 22, further comprising angled metering holes in the inner combustor casing between the annular stator plenum and the annular cavity. 24. An assembly as claimed in claim 23, further comprising the metering holes being circumferentially angled. 25. A gas turbine engine assembly comprising: a combustor between a high pressure compressor and a high pressure turbine,a high pressure rotor including a centrifugal compressor having an annular centrifugal compressor impeller directly adjacent to and upstream of a diffuser,an impeller bleed means for bleeding impeller tip aft bleed flow from between the impeller and the diffuser,a pressurizing means for using the aft bleed flow to pressurize an annular cavity extending radially between the inner combustor casing and the high pressure rotor and extending axially between forward and aft thrust balance seals,a cooling air bleed means for bleeding clean cooling air from a bleed location downstream of an outlet of the diffuser,one or more channels in fluid communication with the cooling air bleed means,each of the one or more channels having a generally radially extending section followed by a generally axially aftwardly extending section, andthe one or more channels in fluid communication with an annular cooling air plenum having one or more accelerators. 26. An assembly as claimed in claim 25, further comprising the cooling air bleed means including an annular manifold in fluid communication with a bleed location downstream of an outlet of the diffuser where compressor discharge pressure air enters a deswirl cascade along an internal radius portion. 27. An assembly as claimed in claim 25, further comprising: an annular combustor stator assembly including a radially extending forward end wall extending radially outwardly from and joined to the inner combustor casing,a radially outer portion of the forward end wall being an aft wall of the diffuser,a stator plenum disposed between and in fluid communication with the impeller and the annular cavity, andthe stator plenum being in part bounded by a radially inner portion of the forward end wall. 28. An assembly as claimed in claim 27, further comprising the pressurizing means including conical diffusion holes in the radially inner portion of the forward end wall. 29. An assembly as claimed in claim 28, further comprising the conical diffusion holes being axially or circumferentially or axially and circumferentially angled. 30. An assembly as claimed in claim 28, further comprising the stator plenum being bounded by the radially inner portion of the forward end wall and an annular cover spaced axially aftwardly of the radially inner portion of the forward end wall. 31. An assembly as claimed in claim 29, further comprising angled metering holes in the inner combustor casing between the annular stator plenum and the annular cavity. 32. An assembly as claimed in claim 31, further comprising the metering holes being circumferentially angled. 33. An assembly as claimed in claim 30, further comprising: each of the cooling channels having a channel inner wall running along a radially outer portion of the forward end wall, the annular cover, and the inner combustor casing;the annular cover including a cover aft wall having a circular wall section followed by a conical wall section;circumferentially spaced apart channel side walls attached to and extending outwardly from the channel inner wall; anda channel outer wall spaced outwardly from the channel inner wall and attached to the channel side walls. 34. An assembly as claimed in claim 30, further comprising each of the cooling channels terminating at an aft conical section of the inner combustor casing between the annular cooling air plenum the cooling channels and cooling air apertures in the aft conical section. 35. An assembly as claimed in claim 34, further comprising a forward thrust balance land in sealing engagement with the forward thrust balance seal on a radially inner surface of the inner combustor casing and an aft thrust balance land in sealing engagement with the aft thrust balance seal. 36. An assembly as claimed in claim 35, further comprising the forward thrust balance seal being located on an aft conical arm of the impeller of the rotor. 37. An assembly as claimed in claim 36, further comprising an annular stator plenum in fluid communication with the annular cavity and bounded in part by a forward end wall and the pressurizing means including conical diffusion holes in the forward end wall. 38. An assembly as claimed in claim 36, further comprising the conical diffusion holes being axially or circumferentially or axially and circumferentially angled. 39. An assembly as claimed in claim 38, further comprising angled metering holes in the inner combustor casing between the annular stator plenum and the annular cavity. 40. An assembly as claimed in claim 39, further comprising the metering holes being circumferentially angled.