ABSTRACT
This paper presents a numerical investigation of the effect of DBDA length on film
cooling performance downstream a circular hole scheme over a gas turbine vane
pressure side. The investigated scheme is that of a set of two DBDAs installed
downstream a cooling jet injection hole to damp the effect of the Counter Rotating
Vortex Pair (CRVP) accompanying the injected cooling jet. The simulation has been
carried out assuming one row of circular holes of a diameter D spaced at 4.5 D in the
cross-stream direction and inclined at 22⁰ with the vane pressure side surface. The
actuators are located at 0.5 D downstream the injection hole and spaced at a
distance = 0.25 D. Five cases of different electrode's length ranging from 1.5 D to 12
D have been investigated under different applied voltages in the range from 10 kV to
60 kV. In all those cases both the blowing and density ratios are assumed constant
at values equal 1 and 2, respectively. Then, the effect of changing the blowing ratio
on the performance has been studied for the case which exhibit optimum
performance where maximum surface effectiveness is achieved for specific actuator
length and applied voltage. The obtained results show that, for each considered
actuator length, the surface average effectiveness was enhanced with the increase of
the applied voltage to a certain limit where a maximum value was obtained, and then
the effectiveness decreased with the increase of the voltage. The results indicate that
this limit varies with the actuator length in such a way that, the longer the actuator the
lower the voltage at which maximum surface average effectiveness occurs.