Performance prediction for turbomachines
In this computer-aided study, existing methods of determining the fluid flow in axial flow turbomachines are examined, and the Consistent Loss Model of Bosman and Marsh is here applied to both duct flow and intrablade applications of the Streamline Curvature technique. The resulting equations are presented in a form similar to that of the conventional equations, thus providing for easy modification of existing Streamline Curvature method computer programs. Interpretation of the equations shows that the mean flow through a blade row passage cannot follow a parabolic path between the blade inlet and outlet flow angles, as is commonly assumed, but must maintain as continuous the streamwise derivative of angular momentum. Procedures are described to design three-dimensional blade shapes from basic aero foil data, and to derive realistic intrablade mean stream surfaces, including allowances for flow deviation and secondary flow. Numerical techniques are presented which have been developed for closely-spaced intrablade calculation grids, to obtain faster convergence than by conventional schemes in Streamline Curvature calculations. The computer program is intended for analysing multi-stage axial flow compressors; tests are presented of simple analytical cases and experimental data for isolated rows of blades, of a' swan-necked' duct, and of a three-row experimental compressor. Three-dimensional flow calculation methods are reviewed with reference to the limitations inherent in applying them to axial flow turbomachines. Suggestions are made for future work.