免费泵亲和定律计算器
使用亲和定律计算泵在不同转速下的性能。
New Flow Rate (Q2)
120.7 m³/h
New Flow Rate (Q2) vs Original Flow Rate (Q1)
公式
## Pump Affinity Laws The affinity laws predict how centrifugal pump performance changes with rotational speed or impeller diameter. They are essential for variable-speed pump sizing. ### Speed Change Laws **Q2/Q1 = N2/N1** (flow scales linearly) **H2/H1 = (N2/N1)²** (head scales with speed squared) **P2/P1 = (N2/N1)³** (power scales with speed cubed) The same relationships apply for impeller diameter changes (replacing N with D). The cubic power relationship makes VFDs very effective for energy savings.
计算示例
A pump at 1450 RPM delivers 100 m³/h at 30 m head, consuming 15 kW. Speed increased to 1750 RPM.
- 01Speed ratio = 1750 / 1450 = 1.2069
- 02Q2 = 100 × 1.2069 = 120.7 m³/h
- 03H2 = 30 × 1.2069² = 30 × 1.4566 = 43.7 m
- 04P2 = 15 × 1.2069³ = 15 × 1.7581 = 26.37 kW
常见问题
How accurate are the affinity laws?
The affinity laws are quite accurate for small speed changes (±20%). For large changes, pump efficiency may shift, making the power prediction less accurate. The flow and head laws remain reasonably accurate.
Can I use affinity laws for positive displacement pumps?
No. Affinity laws apply only to centrifugal (rotodynamic) pumps. For positive displacement pumps, flow is directly proportional to speed, but head is independent of speed.
Why does power increase with the cube of speed?
Flow increases linearly and head increases with the square. Since power = flow × head × density × g / efficiency, and both flow and head increase with speed, power increases as speed cubed.
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