Abstract
Only four parameters are needed to describe the characteristics of turbomachines completely. This concept is used to present maximum obtainable efficiencies and the optimum design geometry of turbines as function of specific speed, specific diameter, Mach number, and Reynolds number, based on the state-of-the-art knowledge. Additionally, other aspects such as unit weight and rotor stresses are discussed. Some of the information is preliminary because of limited information on loss relations for turbines, particularly at low Reynolds number and high Mach numbers.