อัปเดต 2026-09-07

Centrifugal pump

H–Q curve

A pump defined by its head–flow (H–Q) curve. The operating point is where the curve crosses the system resistance.

เมื่อไรจึงใช้

Any rotodynamic pump with a known performance curve.

ค่าที่ต้องกรอก

ค่า	คำอธิบาย
Curve points	H–Q pairs (or a fitted curve). Import from the pump catalog library, provenance-stamped.
Speed	Rated speed; scaled by affinity laws for variable-speed runs.
NPSHr	Optional — enables an NPSH-margin check against NPSHa.

คำนวณอย่างไร

The pump link contributes a head gain H(Q) into the energy equation; the solver finds the flow where the pump curve crosses the system resistance. Variable speed rescales the curve by the affinity laws, and NPSH available is checked against NPSH required.

สมการ

Pump head curve

H_{p} (Q) = h_{0} - r Q^{2}

h₀ = shutoff head, r = curve coefficient (fitted from the curve points). The operating point is where H_p(Q) meets the system head.

Affinity laws (speed change)

\frac{Q _{2}}{Q _{1}} = \frac{N _{2}}{N _{1}}, \frac{H _{2}}{H _{1}} = (\frac{N _{2}}{N _{1}})^{2}, \frac{P _{2}}{P _{1}} = (\frac{N _{2}}{N _{1}})^{3}

How a trimmed / VFD speed ratio N₂/N₁ rescales the base curve.

NPSH available & margin

N P S H_{a} = \frac{p _{a t m} - p _{v}}{ρ g} + z_{s} - h_{f, s}, N P S H_{a} - N P S H_{r} > 0

p_v = vapor pressure, z_s and h_{f,s} = suction static head and friction. A negative margin means cavitation risk.

ข้อควรระวัง

noteA reservoir→pump→tank line with NO junction used to return Q=0 (a determinate per-link solve now handles it).

ที่เกี่ยวข้อง

Variable-speed pump Pump (marching engine)Auto-sizing & goal-seek

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