Hide/Show Apps

Veter boyunca modüle edilen vurumlu uç enjeksiyonu yönteminin uç girdabı aerodinamiği ve kontrolüne etkisinin deneysel incelenmesi

Download
2011
Mercan, Bayram
Uzol, Oğuz
Ostovan, Yashar
This study investigates the effect of chordwise modulated tip injection on the flow and turbulence characteristics of the tip vortex through experimental measurements. This injection technique involves spanwise jets at the tip that are issued from a series of holes along the chord line normal to the freestream flow direction. The injection mass flow rate from each hole is individually controlled using computer driven solenoid valves and therefore the flow injection geometrical pattern at the tip can be adjusted to any desired waveform shape, with any proper injection velocity. Four different scenarios are investigated including baseline no-injection, triangular, sinusoidal and uniform injection patterns. The experiments are performed in a blowdown wind tunnel for a half-wing geometry that has a NACA 0015 airfoil profile with an aspect ratio of three as well as for a low pressure turbine linear cascade that has a T106 profile. Measurements are performed using Constant Temperature Anemometry, Kiel-probe traverses and Stereoscopic PIV techniques. Current data show consistent trends with previously observed effects of steady uniform tip injection such as the upward and outward motion of the vortex as well as increased levels of turbulence within the vortex core. The vortex size gets bigger with injection and the total pressure levels get reduced significantly near the vortex core. However, this increase is not continuous and in fact the levels drop down after a certain injection momentum coefficient or injection pattern is reached. The injection pattern also seems to affect the tip vortex characteristics significantly. It is observed that there might be an optimum injection pattern that could minimize the effects of the tip vortex on the wing. Cascade measurements show that, aside from the 50% plane, which is not affected much, injection reduces the extent and width of the low momentum loss region downstream of the blades regardless of the waveform. However, the magnitude and distribution of this reduction varies depending on the waveform. 85% and 95% span planes seem to get affected in a different manner. Most probably due to the fact that 85% plane is more affected by a possible passage vortex whereas 95% plane is more in the leakage vortex zone