An experimental investigation into pre-swirl effectiveness
and receiver hole discharge coefficient characteristics for a
high radius injection pre-swirl cooling systems was carried out
on a physically representative experimental rig with a 450 mm
diameter rotor. The receiver holes and pre-swirl nozzle were
located at a radius of 181 mm and 180 mm respectively. The
experimental work was mainly conducted at 5000-12000 rpm,
4 bar absolute pressure and 1.132 kg/s air supply. The
maximum air supply temperature was 190ºC.
Pressure and temperature distributions in the pre-swirl
system were examined with an emphasis on the velocity
effectiveness of the pre-swirl system as a whole and on the
discharge coefficients of the rotating 'receiver holes' in the
rotor. The results showed that the velocity effectiveness
increased with increasing swirl ratio resulting in reduced blade
cooling flow temperature. Different seal flow configurations
caused very different effectiveness at different speeds, but
outflow through the inner and outer seals always gave the
highest effectiveness compared other configurations.
Increasing the seal flow rate reduced the effectiveness. For the
coefficient of discharge, except for the low speed range, it
increased with increase in swirl ratio for most speeds.