Design Method and Performance Effects of Curvature-Smooth Centrifugal Compressor Blades

Blade curvature has an important effect on the pressure distribution over the blade surface as well as the quality of airfoil machining, but curvature smoothing method in design environments is little studied. A new geometry generator is developed for the design of curvature-smooth airfoils. The sections of an airfoil can be initially designed by a conventional method, and each of the sections is then regenerated by fitting a fifth order B-spline curve. The first order differential of the curvature with respect to arc length of the blade surface is used as a curvature smoothness measure. The distance between discrete points and the curve, and the integral of the square of the first derivative along the streamwise section curve are simultaneously minimized in the fitting process. The design of a transonic centrifugal compressor for turbocharger application is presented to study the effects of the curvature-smooth blade on centrifugal compressor performance. A numerical study was carried out and the results are discussed.