16　空化系數(過去曾用"氣蝕系數")σ：表征水輪機空化發生條件和性能的無因次系數.17　吸出高度Hs ：水輪機規定的空化基準面至尾水位的高度.

1 Technical Renovation: Technical measures shall be taken to improve, replace or rebuild hydropower station equipment or facilities so as to enhance its advancedness, rationality, economy and reliability, and call it technological reformation.2 Renewal and renovation: Replacement of new equipment, the same installed capacity, due to improved performance, increased efficiency to increase annual power generation, known as the renovation .3 capacity transformation: all or part of the unit equipment technological transformation, increased installed capacity, due to improved performance, Increased efficiency and increased capacity to increase annual power generation, known as capacity expansion transformation. Expansion unit is also one of the ways to capacity transformation .4 capacity reduction transformation: all or part of the unit equipment technological transformation, reduced installed capacity, due to performance Improve the efficiency and increase annual power generation, known as capacity reduction transformation.5 output power (or output power) Pout or P: the mechanical power output of the turbine shaft, or the generator output power output terminal.6 rated power ( Or rated output) Pr or PN: at rated head and rated speed turbine power continuous issued by the power of its rated power, common symbol Pr; rated power , Rated speed and rated power factor generator continuous power is the generator rated power, common symbol PN 7. 7 Rated head Hr: Turbine at rated speed, the rated power output of small water head. 8 Rated speed nr: Steady speed selected by Hydro-generator set according to design of hydropower station. 9 Runaway speed nR: **** speed when turbine is out of control and shaft load moment is zero .10 Rated flow rate Qr: Turbine Flow at rated power at rated head and rated speed 11 Nominal diameter of turbine (true machine or model) runner D1: For Francis turbine Diameter at the intersection of the front and lower ring of the inlet side of the vane; for shaft Flow and cross-flow turbine is the runner chamber diameter intersecting the blade axis; for a bucket-type turbine it refers to the pitch circle diameter of the runner.12 Flow-through components: From the inlet of the turbine diversion chamber to the outlet of the drain, where Cavitation (historically "cavitation"): Cavitation is the process by which cavitation occurs when localized pressure in the runner drops to a critical pressure (generally close to the vapor pressure) It is the general term for the bubbles, the accumulation of bubbles, the flow, the division, and the collapse process.14 Cavitation (used to be "cavitation damage" in the past): The material of flow-through parts due to cavitation is damaged.15 Abrasion: Under the water turbine flow through the parts surface erosion and sediment damage caused by the combined effect of damage to the material.
16 cavitation coefficient ("cavitation coefficient" used in the past) σ: dimensionless factor characterizing the conditions and performance of turbine cavitation 17 suction height Hs: altitude of the turbine from the cavitation plane to the tailwater level.