Axial-flow turbines and radial-inflow turbines are the two most common types of dynamic turbines. The flow streamlines through the blade rows of an axial-flow turbine have essentially a constant radius, whereas there is a substantial reduction in radius through the radial-inflow turbine. A less common type of dynamic turbine is the radial-outflow turbine, where there is a substantial increase in radius through the blade rows. Since the work done on the fluid depends directly on the change in fluid angular momentum across the rotor, the radial-outflow turbine has a substantial disadvantage relative to the radial-inflow turbine due to its lower rotor inlet radius. Indeed, radial-outflow turbine's higher rotor discharge radius places it at a substantial disadvantage relative to both the axial-flow turbine and the radial-inflow turbine. This writer's experience with the radial-outflow turbine is limited to a single case. A combination of the methods described in this book appeared to be reasonably effective in estimating its performance, but the questionable accuracy of the experimental performance data available introduced too much uncertainty to recommend a design and analysis procedure for that type. Hence, this book will address only the axial-flow and radial-inflow turbine types, where sufficient experimental data has been available to validate the procedures recommended.
