טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentEpshtein Mark
SubjectInlet Guide Vane Separation Control Using Dielectric Barrier
Discharge Plasma Actuators
DepartmentDepartment of Mechanical Engineering
Supervisor Professor David Greenblatt
Full Thesis textFull thesis text - English Version


Abstract

Inlet guide vanes (IGVs) are a common component in both axial and radial compressors, fans and blowers. They impart swirl to the incoming flow and, if the vanes are variable (VIGVs), act as a flow throttling mechanism. However, IGVs have limitations resulting from highly complex three-dimensional flow separation processes at high stagger angles.

The introduction of periodic perturbations at flow instability frequencies is known to ameliorate flow separation on airfoils and wings, but their effect has never been demonstrated on an annular IGV cascade.

To study this, a transparent axial flow facility was built with 10 symmetric constant chord VIGVs mounted directly upstream of an axial fan; one guide vane was equipped with surface pressure ports. Dielectric barrier discharge (DBD) plasma actuators were installed at the leading-edges of all 10 guide vanes and pulsed in an attempt to exploit flow instabilities.

Large negative deflection of the IGVs revealed a complex three dimensional flow pattern that included spanwise flow at the leading edge with corner separation at the tip and two dimensional separation in the middle of the blade which was (incidentally) remarkably similar to that on the single vane deflected at smaller negative angles. This flow pattern was partially caused by the constant chord design of the IGVs as opposed to the usual constant solidity design. Nevertheless, Pulsed perturbations eliminated the two dimensional separation but failed to reduce the endwall separation; this control effect also somewhat affected the similarity with the single blade configuration due to overall changes in system conditions. Furthermore, at a smaller angle the plasma effect was comparable to the boundary layer tripping triggered by the presence of the actuator. Also, the entire system exhibited a curious nonlinear transient response due to complex rotor stator interaction which suggested that active flow control in multi staged machines might require simultaneous control on all stages.