Tech Briefs

Robust, Optimal Subsonic Airfoil Shapes

A method has been developed to create an airfoil robust enough to operate satisfactorily in different environments. This method determines a robust, optimal, subsonic airfoil shape, beginning with an arbitrary initial airfoil shape, and imposes the necessary constraints on the design. Also, this method is flexible and extendible to a larger class of requirements and changes in constraints imposed.

In one embodiment, process steps include providing a specification of a desired pressure value at each of a sequence of selected locations on the surface of a turbine airfoil; providing an initial airfoil shape; providing a statement of at least one constraint to which a final airfoil shape must conform; using computational fluid dynamics (CFD) to estimate a pressure value at each of the selected perimeter locations for the initial airfoil shape; using CFD to determine the pressure distribution for the airfoil shapes that are small perturbations to the initial airfoil shape; and using an estimation method, such as a neural network, a support vector machine, or a combination thereof, to construct a response surface that models the pressure distribution as a function of the airfoil shape using the CFD data. Other process steps include using an optimization algorithm to search the response surface for the airfoil shape having the required pressure distribution, and providing at least one of an alphanumeric description and a graphical description of the modified airfoil shape.

Constraints may be drawn from the following group, or may be one or more other suitable constraints: vortex shedding strength from the trailing edge of the airfoil is no greater than a selected threshold value; a difference between any resonant frequency of the airfoil and the vortex shedding frequency is at least equal to a threshold frequency difference; mass of the airfoil is no larger than a threshold mass value; and pressure value at each of a sequence of selected locations along the surface of the airfoil differs from a corresponding reference pressure value by no more than a threshold pressure difference value. This work was done by Man Mohan Rai of Ames Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to the Ames Technology Partnerships Division at 1-855-NASA-BIZ (1-855-6272-249). ARC-14586-2

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