Axial Airflow and Hub Position Configurator¶
Run the Axial Airflow and Hub Position Configurator MicroSim Fullscreen
This sketch is built on the FanPedia MicroSim kit. To run it in the
p5.js editor, add the ../shared-libs/ files it loads
(fanpedia-sim.css, fanpedia-core.js, fanpedia-p5.js, fan-drawings.js),
or their published URLs, to the editor's index.html before pasting
ch08-axial-airflow-hub-configurator.js.
About This MicroSim¶
An axial fan order has to say which way the air goes, and that one choice fixes two more words on the order. FanPedia gives each airflow code an alternative name based on where the hub faces, and its left hand and right hand pages pair each code with a hub bore (FanPedia PDF pp. 36–43):
| Airflow code | Air path | Hub position | Hub bore |
|---|---|---|---|
| PM | Through the impeller, then over the motor | Hub on intake side | Reverse bore hub |
| MP | Over the motor, then through the impeller | Hub on discharge side | Standard bore hub |
Impeller hand (left or right) and pitch type (fixed or adjustable) do not change the rule. A reversible impeller runs standard flow as MP and reverse flow as PM (FanPedia PDF p. 41).
The sim shows a side view of a direct-drive axial fan with the motor at the left of the tube and the impeller at the right. For each of eight orders, in a fixed order, you choose the hub position and the hub bore and press Check. Until you do, the fan is drawn without its hub and the ends of the tube are not labeled. After Check, the hub appears with its boss highlighted, the ends are labeled Intake and Discharge, and the air moves from intake to discharge: right to left for PM, left to right for MP. The heavier blade edge is the leading edge, which always faces the intake.
| # | Order | Hub position | Hub bore |
|---|---|---|---|
| 1 | Airflow = PM, adjustable pitch | Intake side | Reverse bore |
| 2 | Airflow = MP, fixed pitch cast | Discharge side | Standard bore |
| 3 | Air passes over the motor first, then through the impeller | Discharge side | Standard bore |
| 4 | Air passes through the impeller first, then over the motor | Intake side | Reverse bore |
| 5 | Reversible impeller, standard flow | Discharge side | Standard bore |
| 6 | Reversible impeller, reverse flow | Intake side | Reverse bore |
| 7 | Right hand adjustable pitch impeller, airflow = MP | Discharge side | Standard bore |
| 8 | Left hand fixed cast impeller, airflow = PM | Intake side | Reverse bore |
Each order has one scored attempt and counts as correct only when both answers are right. Mastery is 7 of 8 orders correct on the first attempt. There is no retry of a single order; Start over restarts the whole set.
After order 8 the free model (Explore mode) unlocks. It has two settings: the airflow code (PM or MP) and the rotation (correct for the impeller, or reversed). With the correct rotation, air enters at the leading edges and leaves at the discharge. With the rotation reversed, the intended airflow arrow is crossed out and the sim reads "Wrong rotation: no airflow in the proper direction (FanPedia note 2)." Rotation is always labeled as viewed from the discharge side. The rotation arrow is a symbol for "as the impeller needs" or "reversed"; the actual direction depends on the impeller hand, which this sim does not set.
How to Use¶
- Read the order. Choose Intake side or Discharge side for the hub, and Standard bore or Reverse bore for the hub bore. Your choice is marked with a ✓ and a heavier outline.
- Press Check (or Enter). A correct order reads "✓ Correct." with the reason, in a box with a solid green border. A wrong one reads "✗ Not quite." with the right hub position and bore and the reason, in a box with a dashed red border. "Orders correct: n of 8" keeps the running count.
- Press Next order (or Enter) and repeat. After order 8, press Open free model. The panel shows the first-attempt score, the mastery line and any missed orders.
- In the free model, switch the airflow between PM and MP and watch the Intake and Discharge labels and the hub label change; then set the rotation to Reversed and see the airflow stop in the intended direction. The free model is never scored. Start over returns to order 1 and clears the score.
Keyboard: I and D choose the hub side, S and R choose the bore, Enter checks the order and then goes to the next one. Tab reaches every button and, in the free model, both menus.
Data label: "Source: FanPedia PDF pp. 36–43", at the bottom left of the drawing.
Iframe Embed Code¶
You can add this MicroSim to any web page by adding this to your HTML:
<iframe src="https://moroshek.github.io/FanTASTIC-textbook/sims/ch08-axial-airflow-hub-configurator/main.html"
height="589px"
width="100%"
scrolling="no"></iframe>
Lesson Plan¶
Learning Objective¶
The learner will apply FanPedia's axial airflow rules to state the hub position and hub bore for an axial fan order, given its airflow code or air path, with at least 7 of 8 orders correct (Bloom: Apply, verb: apply).
Audience¶
Adult professional development: new application engineers, sales staff, representatives and facilities staff.
Duration¶
10-15 minutes
Prerequisites¶
- Axial impeller and blade leading edge (Chapter 8)
- Airflow = PM and airflow = MP; hub on intake side and hub on discharge side (Chapter 8)
- Standard bore hub and reverse bore hub; reversible impeller (Chapter 8)
- Rotation viewed from the discharge side (Chapter 8)
Activities¶
- Orders (5-7 min): Work through the eight orders. Before each Check, say the air path out loud ("impeller, then motor") and name the build.
- Review (2-3 min): For any missed order, reread its reason and the section "Hub on Intake Side and Hub on Discharge Side". Note that orders 7 and 8 add an impeller hand that does not change the answer.
- Free model (3-5 min): Switch PM and MP and note which end becomes the intake. Then reverse the rotation and explain why the result is no useful airflow rather than less airflow.
Common Misconceptions Addressed¶
- "Hub on intake" means the motor is on the intake side: in PM the air meets the impeller first, so the motor is on the discharge side of the impeller.
- PM and MP are rotation codes: they are airflow codes, read left to right as the air's path; rotation is a separate setting in the free model.
- A reversible impeller has a fixed hub position: orders 5 and 6 give the same impeller two answers, one for each flow mode.
- Running an axial impeller backward gives less airflow in the same direction: the free model shows no airflow in the proper direction, as FanPedia's note says.
Assessment¶
- The running line "Orders correct: n of 8" counts orders with both answers right. At the end the sim shows "First-attempt score: n of 8" and the mastery line; mastery is 7 of 8 orders on the first (and only) attempt.
- Running the free model is exploration, not evidence. Follow-up question: a customer orders a reversible fan for supply in summer and exhaust in winter; which hub position does each mode have?
References¶
- FanPedia: The Fan & Blower Encyclopedia (PDF) - pp. 36–43 give the axial airflow codes, the "aka" hub names, the reversible impeller modes and the standard and reverse bore hubs.
- FanPedia online - Twin City Fan's reference on fan types, arrangements and axial fan configuration.
- Axial fan design (Wikipedia) - background on axial impellers, blades and hubs.