This revision removes contradictory seat-angle conventions and unsupported universal flow, spring, clearance, failure and repair claims. It retains one source-explicit ideal area ledger and a connected engine-style prescribed-motion section.
Ideal Poppet Curtain-Area Explorer
Enter a declared valve-seat diameter and maximum prescribed lift. The worksheet compares ideal curtain area with circular seat-port area and reports the algebraic equal-area lift; it does not predict flow, discharge coefficient, timing, force or valve suitability.
Equation Used
- D is the declared valve-seat/port diameter used by both ideal equations.
- h is the declared maximum axial lift and not a cam profile, timing specification or safe setting.
- The ideal curtain is treated as circumference pi D multiplied by axial lift h.
- Circular port area ignores stem, guide, throat and downstream restrictions.
- The reported limiting area is only the smaller of two geometric areas; no discharge coefficient is applied.
- Animation phase prescribes a normalized 0-to-h-to-0 cycle and does not represent entered rpm or real time.
- Seat angle/profile, contact band, stem diameter, guide clearance, spring preload/rate/surge, cam law, follower dynamics, lash, inertia, pressure, temperature, fluid properties, compressibility, Reynolds/Mach number, discharge coefficient, mass/volume flow, leakage, wear, heat transfer, lubrication, materials, fatigue, manufacturing, installation, adjustment, maintenance and safe operation are excluded.
Replaces conflicting seat-angle and free-Cd effective-area claims with one source-explicit ideal curtain-area ledger and explicit exclusions.
A guided stem moves the head axially from its seat
US 3,466,009 describes an engine poppet-valve assembly with a port and seat ring, a head on a stem, a stem guide, and a spring and retainer that urge the head closed. US 4,187,059 likewise describes a guided spring-loaded poppet moving axially into and off a seat.
The connected section uses a generic prescribed axial actuator only to display that motion. The phase interpolates from zero to the entered maximum lift and back; it is not a cam law, actuator design, machine speed or dynamic response.
Area geometry is not valve selection
Poppet valves appear in engines, pumps and fluid-control hardware, but their materials, actuation, seats, guides, ports and operating conditions differ. This generic geometry cannot transfer performance or settings among products.
Use the actual valve and equipment manufacturer's drawings, rated data and procedures for selection, operation and service.
Use one source-explicit ideal curtain relation
A NASA propulsion-control report states this simple poppet flow-area relation with D as valve-seat diameter and h as lift. The worksheet separately computes circular seat-port area A_port=pi D²/4 and reports only the smaller geometric area.
The equal-area lift is an algebraic crossover within this ideal two-area comparison. It is not a universal optimum or proof that actual flow stops changing there.
A transparent ideal-geometry example
For D=36 mm and h=9 mm, circular port area and ideal curtain area are both 1,017.9 mm². The equal-area lift is 36/4=9.00 mm. No flow rate follows because pressure, fluid state, discharge behavior and actual port geometry are not entered.
Real discharge behavior requires test data and operating conditions
NASA's Poppet Valve Discharge Coefficients report presents coefficient data against dimensionless stroke x/d and distinguishes seat geometry and reference areas. A free slider for discharge coefficient cannot turn a geometric area into capacity without the applicable test basis, pressure ratio and fluid model.
The ideal curtain omits seat angle and face shape, stem and guide blockage, throat contours and adjacent passages. The former universal lift percentages, flow claims, leakage comparisons, spring loads, RPM limits, clearances, seat widths, materials, fatigue counts, brand examples, fault diagnoses and repair instructions are removed.
Poppet-area questions
Is limiting geometric area a flow capacity?
No.
Why is seat angle absent?
The retained NASA relation is explicitly A=pi D h and avoids the former conflicting angle convention.
Is h=D/4 the best lift?
No. It is only where the two ideal areas are equal.
Does the animation represent machine speed?
No. It is normalized prescribed motion.
Poppet-valve geometry and topology references
- NASA propulsion-control report (1982): states simple-poppet flow area A=pi D h.
- NASA, Poppet Valve Discharge Coefficients: coefficient dependence on stroke ratio, seat geometry and reference area.
- US 3,466,009: engine port, seat ring, valve head, stem, guide, spring and retainer topology.
- US 4,187,059: guided spring-loaded poppet moving axially into and off a seat.
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