离心泵汽蚀比转速数值的大小限制疑问？ 经验显示气蚀比转速越高，泵的允许操作区越窄。低于11000（美制单位）的泵比其它泵运行更稳定。美国水力协会推荐在小流量范围nss的限制为8500，但是在应用中往往把此值限制在11000（小流量范围）。 suction specific speed may be used to determine what pump geometry - radial, mixed flow or axial - to use for maximum efficiency and prevent cavitation. suction specific speed is commonly used as a basis for estimating the safe operating range of a pump. suction specific speed is dimensionless and are expressed as nss = ω q1/2 / npsha3/4 (1) where nss = suction specific speed ω = pump shaft rotational speed (rpm) q = flow rate capacity (m3/h, l/s, m3/min, us gpm, british gpm) at best efficiency point bep npsha = available net positive suction head (m, ft) specific suction speed can be compared with specific speed but instead of using the total head of the pump, the available net positive suction head n.p.s.h.a is used. as a rule of thumb the specific suction speed should be below 8500 (calculated with us gpm) to avoid cavitation. online specific suction speed pump calculator the calculator below can used to calculate pump specific speed: ω - pump shaft rotational speed (rpm) q - flow rate (m3/h, l/s, m3/min, us gpm, british gpm) npshr - required net positive suction head (m, ft) note! when comparing pumps and their documentation be aware of the units used. suction specific speed - ss - is useful in determining the required operating conditions on the suction side of the pump. for geometrically similar pumps the ss have the same value. empirical studies indicates that higher suction specific speed is, the narrower is the safe operating range from its best efficiency point (bep). pump models with ssd (us units) less than 11000 have more stable operation and are more reliable. 查看更多
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