10.4.
COMPRESSOR
The compressor has five axial stages and one centrifugal stage. The inlet guide vanes and the
first and second stage stator vanes in the compressor vary their angle of attack according to compressor
speed. The centrifugal impeller is mounted aft and on the same shaft as the axial compressor. One of
the major design differences of the T700 is that the axial-compressor rotor stage blades and disks are
one-piece castings. This means better rotor integrity and also easier buildup and overhaul. The
compressor has very few blades, 332 total. This is about one-third the number in comparable current
engines. Stages one and five have borescope ports for inspections. Just aft of the centrifugal impeller is
the diffuser passage.
10.5.
COMBUSTOR
The annular combustion chamber is located aft of the diffuser. Engine durability and time
between overhauls (TBO) are directly related to the heat of the combustor. If the combustor can
develop the power required at a lower temperature, component service life can be increased.
The combustor has twelve vaporizing fuel injectors and two atomizing start-fuel nozzles.
The axial type vaporizing combustor operates with a lower peak temperature factor. Axial flow ensures
minimum liner area and hence minimizes the amount of secondary cooling air to be mixed into the hot
gas stream. The annular combustion chamber can be seen in figure 10.1.
10.6.
GAS GENERATOR TURBINE
The T700 gas generator turbine is a two-stage, air-cooled, high-performance, axial-flow
turbine. The modular concept has been used in the gas generator turbine design for ease of assembly
and maintenance. The turbine is divided into easily accessible submodules consisting of the first stage
turbine nozzle and the turbine rotor.
The first stage nozzle submodule consists of 24 air-cooled cast vane segments brazed in pairs.
These twelve pairs are assembled to the inner support and held in place by a retaining ring with bolts.
The rotor submodule consists of the turbine rotor combined with the second nozzles,
supports, and shrouds. Both first and second stage disks, cooling plates, and turbine blades are clamped
by
260
Previous Page
