The Shape of Turbomachines and the Ongoing Role of Specific Speed

A wide-ranging taxonomy of turbomachinery types is given. The requirements of steam turbines and aircraft engines established a traditional approach to aerodynamic design analyzing orthogonal planes. Computers facilitated this and led to a greater reliance on Computational Fluid Dynamics, offering exciting developments in three dimensional modeling. A balance should be sought between analytical, computational and experimental work. In work on an axial flow pump rig photographic investigations of cavitation over the rotor tip have given insights including the very abrupt collapse of cavitation bubbles. Although essential for supersonic regions blade sweep can also be used effectively at lower speeds and can provide significant performance improvements. Further integration of the design and research communities should lead to an improved understanding and predictability. One such area is the unexpected appearance of streamwise vortices on blade suction surfaces. This provides a good base for understanding blade sweep and its effects.