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Impeller Type Classifier

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About This MicroSim

Naming an impeller from a description follows a fixed order: first the air path (outward, straight through, or partway), then for a centrifugal impeller the blade shape against rotation, and for an axial impeller the pitch type, material and flow modes. This sorter gives you ten descriptions like the ones on field photos and catalog pages, one at a time in shuffled order, and six bins:

  1. Backward inclined (centrifugal)
  2. Forward curved (centrifugal)
  3. Mixed flow
  4. Axial, fixed pitch
  5. Axial, adjustable pitch
  6. Axial, reversible
# Card (short name) Bin
1 Flat, single-thickness blades whose tips trail rotation; air leaves at a right angle to the shaft Backward inclined (centrifugal)
2 Many short, shallow blades curved with rotation, held by an end ring and tie rods Forward curved (centrifugal)
3 Airfoil blades tapering from the front plate to the hub end; air leaves partly along the shaft Mixed flow
4 Cast impeller with blades formed at one angle Axial, fixed pitch
5 Separate blades whose shanks clamp into the hub Axial, adjustable pitch
6 One impeller in two modes: standard flow MP and reverse flow PM Axial, reversible
7 Fiberglass blades on an aluminum hub, the "F4/F6" impeller Axial, adjustable pitch
8 Fiberglass "TF" impeller with molded blades Axial, fixed pitch
9 SWSI wheel with backward-tilted flat blades in an inline (tubular) centrifugal fan Backward inclined (centrifugal)
10 "TCTA" impeller from FanPedia's axial impeller types Axial, fixed pitch

Each card gets one scored placement. The placement locks, the card turns green with a solid border and "✓ Correct: ." or red with a dashed border and "✗ This one is .", followed by the reason, and a chip with ✓ or ✗ lands in the bin you chose. Misplaced cards go to a review pile. After card 10 the summary shows the first-attempt score (n of 10), the mastery line and the review pile with each card's correct bin. Redo review pile runs those cards again, unscored; the review pile never changes the score. Mastery is 8 of 10 on the first attempt.

How to Use

  1. Read the card and ask the starting question: where does the air go, and what do the blades look like?
  2. Press the bin button (or key 1 to 6). Read the verdict and the reason.
  3. Press Next card (or Enter). After card 10, press Show summary.
  4. On the summary, press Redo review pile to place the misplaced cards again (not scored), or Start over to reshuffle all ten cards and clear the score.

Keyboard: keys 1 to 6 place the card in that bin; Enter goes to the next card. Tab reaches every button.

Data label: "Source: FanPedia PDF pp. 6, 31–35, 41", at the bottom left of the drawing.

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Lesson Plan

Learning Objective

The learner will classify written descriptions of impellers into the impeller types named in Chapter 8, with at least 8 of 10 correct on the first attempt (Bloom: Understand, verb: classify).

Audience

Adult professional development: new application engineers, sales staff, representatives and facilities staff.

Duration

10 minutes

Prerequisites

  • Centrifugal, axial and mixed flow impellers (Chapter 8)
  • Backward inclined and forward curved impellers; single width single inlet (Chapter 8)
  • Fixed pitch, adjustable pitch, fiberglass axial and reversible impellers (Chapter 8)

Activities

  1. Sort (5 min): Place all ten cards. Before each placement, say the air path first, then the blade feature that decides the bin.
  2. Review pile (2-3 min): Redo the misplaced cards and read each reason.
  3. Discussion (2 min): Why is card 9 centrifugal even though the fan is tubular? Why is card 7 adjustable even though it is fiberglass?

Common Misconceptions Addressed

  • Many narrow blades always means forward curved: card 2 is decided by blade tips pointing with rotation, not by blade count.
  • Any impeller in a tubular housing is axial: card 9 is a backward inclined wheel in an inline centrifugal fan.
  • Adjustable pitch means the blades can be changed while the fan runs: card 5 describes blade shanks clamped into the hub, so the angle is reset by re-clamping the blades, a hardware adjustment rather than a running control.
  • Fiberglass impellers are always fixed pitch: card 7 (F4/F6) is adjustable, card 8 (TF) is fixed.

Assessment

  • The running line "Cards correct: n of 10" counts first placements. At the end the sim shows "First-attempt score: n of 10" and the mastery line; mastery is 8 of 10 on the first attempt. The review pile is practice and does not change the score.
  • Follow-up question: a photo shows a tubular fan with a wheel whose blades taper toward the hub. Which two bins are possible, and what would you look for to decide?

References

  1. FanPedia: The Fan & Blower Encyclopedia (PDF) - p. 31 (centrifugal impeller captions), pp. 6 and 32 (mixed flow), pp. 33–35 (axial impeller types, fixed and adjustable), p. 41 (reversible impeller).
  2. FanPedia online - Twin City Fan's reference on impeller types.
  3. Centrifugal fan (Wikipedia) - background on backward inclined and forward curved blades.
  4. Axial fan design (Wikipedia) - background on axial impellers and blade pitch.