Improved algorithms for circulation-control airfoils in transonic flow

The Sonic Surface in the Inter-Blade Channel of the Last Stage Rotor Wheel in the Steam Turbine of Large Output

“…The sonic line closes around the leading edge in this case (started supersonic flow), near the stagnation point. The situation between the subsonic and started supersonic inlet flow (unstarted supersonic flow) represents much more complex issue [6] with unsteady behaviour and manifestation of flow field instability. The next paragraphs are focused mainly on flow fields in such turbine cascade geometries, where the inlet flow is subsonic, and thus the sonic line connects the pressure and suction side of the adjacent profiles.…”

“…The shape of sonic line in the case of cascades consisting of flat profiles (similar to the profile in the Figure 13 The sets of profile cascades intended for even longer rotor blades usually work with supersonic inlet flow field. The process of the further sonic line formation is well known and has been described by Dvorak [6]. [7].…”

“…An example is shown in the interferometric picture in the Figure 15. The transition from unstarted to started flow is unsteady process in which even the bistability effects appear [6]. The unsteady behaviour of the flow field naturally has an impact on the sonic line.…”

“…by Safarik [2], [3], Shapiro [4] or Thompson [5]. Interesting overview of various analytical solutions of sonic line shape in symmetric and asymmetric channels provides the work of Dvorak [6]. The solution of the shape of sonic line in the narrowest part of an inter-blade channel is based on knowledge of the channel curvature in the region of channel throat.…”