This book provides easy access to the updated information on the analysis, design, operation, pollution impact and selection criteria of hydraulic and detailing the performance of the hydraulic, gas and steam components of the main energy conversion systems. Many of these fluid operating machines, in spite of their length in service, achieve continuous improvements in terms of performance, efficiency and emission control, by taking advantage of new technologies: electronic control, new materials, experimental facilities, computer models, etc.... Indeed, during the last decades, they have successfully faced the current two main constraints: a better efficiency together with a reduced environmental impact. Giancarlo Ferrari is full professor hydraulic and thermal machines at the Politecnico di Milano, where he is engaged with teaching, research and consulting activities in energy transformations, fluid-dynamics and combustion processes occurring in fluid operating machines.