Thrush Aircraft S2R–T660 Maintenance Manual page 76

THRUSH AIRCRAFT INC - T660 TURBO THRUSH
AIRCRAFT MAINTENANCE MANUAL
A row of stator vanes, located between each stage of compression, diffuses the air, raises its static
pressure and directs it to the next stage of compression. The compressed air passes through
diffuser tubes, which turn the air through ninety degrees in direction and convert velocity to static
pressure. The diffused air then passes through straightening vanes to the annulus surrounding the
combustion chamber liner assembly.
The combustion chamber liner is an annular, heat resistant alloy; domed at the front end where it is
supported inside the gas generator case by the 14 fuel manifold adapter sheaths and both igniters.
The rear end of the combustion chamber is open and is supported by the large and small exit ducts.
The liner assembly has perforations of various sizes that allow entry of compressor delivery air. The
flow of air changes direction 180 degrees as it enters and mixes with fuel. The fuel/air mixture is
ignited and the resultant expanding gases are directed to the turbines. The location of the liner
eliminates the need for a long shaft between the compressor and the compressor turbine, thus
reducing the overall length and weight of the engine.
Fuel is injected into the combustion chamber liner through 14 simplex nozzles supplied by a dual
manifold consisting of primary and secondary transfer tubes and adapters. Two spark igniters that
protrude into the liner ignite the fuel/air mixture. The resultant gases expand from the liner, reverse
direction in the exit duct zone, and pass through the compressor turbine inlet guide vanes to the
single-stage compressor turbine. The guide vanes ensure that the expanding gases impinge on the
turbine blades at the most optimum angle, with minimum loss of energy.
The still expanding hot gases from the gas generator are still directed forward to the power turbine
inlet guide vane which directs, at the most optimum angle, the gas flow onto the power turbine
which drives the propeller shaft via a two-stage reduction gear box.
The compressor and power turbines are located in the approximate center of the engine with their
respective shafts extending in opposite directions. This feature provides for simplified installation
and inspection procedures. The exhaust gas from the power turbine is collected and ducted in the
bifurcated exhaust duct assembly and directed to atmosphere via twin opposed exhaust stubs.
Interturbine temperature (T5) is monitored by an integral bus bar, probe and harness assembly
installed between the compressor and power turbines with the probes projecting into the gas path.
A terminal block mounted on the gas generator case provides a connection point to cockpit
instrumentation.
All engine-driven accessories, with the exception of the propeller governor, overspeed governor
and NP tachometer-generator, are mounted on the accessory gearbox at the rear of the engine.
4 – 3
Effective: 12/17/03