AXIAL PLANE AIRFOIL CASCADE. GRAPHICS FOR ENERGETICAL AND CAVITATIONAL ANALYSIS IN INCOMPRESSIBLE IDEAL/PERFECT FLUID

Abstract

The work continues the discussions of a previous presentation (Fluid Mechanics and Its Applications – Caius Iacob Colloquium, Brasov 2006, cited as reference) regarding the operation of the program CASCADExpert in order to describe energetic and cavitational behavior of a plane airfoils cascade (NACA 8410, NACA 0010).The first part of this work partially restores the theoretical and calculation background, which was detailed in the cited paper. Starting from 3D surfaces created for Cpmin (βIN, βS), CL (βIN, βS), CD (βIN, βS), at t/L =const., lines of equal value can be built. For Cpmin as example, these representations allow fast and reliable determination of dangerous cavitational regimes of the cascade. The curves CFtang > 0, CFtang < 0, were built in the same manner, in different frames and that may give an insight into the operating field in which significant forces occur from active torque composition. The analysis took into consideration the classical curves for a plane cascade profiles having a constant stagger angle βS = const. and as parameter ratio t / L = 0.5, 0.75, 1.00, 1.25 or at constant ratio t / L = constant having as parameter the stagger angle βS = 30°, 60°, 90°, 120°. Finally, the calculations and representation were oriented towards design so there were built curves of equal value for CFtang , CFaxial, Cpmin in the field δU-βIN, as well as synthetic images valuable for the designers of axial hydraulic machines, as they explicitly indicate the areas recommended for the machine's operating system, or the avoidable ones.