During the past three decades advances have been made in the fluid dynamic and thermodynamic design and understanding of radial flow turbomachines. Radial turbomachines possess their own distinctive characteristics, and present the engineer with as full a range of complexities as any fluid flow problem. This book describes the current technology and design methods for centrifugal compressors and radial turbines working in compressible flow. These are of particular relevance to gas turbine engines, internal combustion engine turbochargers, process compressors and cryogenic expanders. The aerodynamic design of the turbomachine is preliminary design to the specification of blade forms and computational fluid dynamic analysis of vane and blade passage flows. The treatment throughout is modern, with full recognition of current computer-aided design methods. However throughout the book a clear separation is made between the fundamental gas dynamics and the empiricism necessary to close the gap between theory and practice in situations of such complexity. Computer program listings for preliminary design are included. The problems posed by specific applications are dealt with in details: for example, techniques for the suppression of surge in centrifugal compressors and a consequent widening of the operating range, and the problems of pulse operation of radial turbines as encountered in turbocharger applications. The book contains comprehensive surveys of the literature in all these fields.