Calculator
Enter your airflow and targets. The tool sizes the cyclone using standard proportions, then estimates pressure drop, fan power, and a rough cut size.
Formula used
This tool uses standard cyclone proportions and simple engineering estimates to size the body and predict basic performance. Geometry follows a high-efficiency layout where inlet width a = 0.20D and inlet height b = 0.50D, so the inlet area is Ain = a·b = 0.10D².
- Q = Vin · Ain ⇒ D = √( Q / (0.10 · Vin) ) (with Q in m³/s).
- Pressure drop: ΔP = Eu · (ρ · Vin² / 2).
- Fan power: P = (Q · ΔP) / η.
- Inlet Reynolds number: Re = (ρ · Vin · Dh) / μ, using Dh ≈ 2ab/(a+b).
- Rough cut size (simplified Lapple-style): d50 ≈ √( (9 μ b) / (2π Ne ρp Vin) ).
Notes: The cut-size estimate is approximate and depends on dust distribution, leakage, roughness, and real cyclone design details. Use it for comparisons, then validate with manufacturer curves when possible.
How to use this calculator
- Measure or select your blower airflow at working static pressure.
- Pick an inlet velocity that fits your ducting and noise goals.
- Use air properties for your temperature, or keep defaults.
- Enter a realistic particle density for your dust or chaff.
- Click Calculate to get cyclone dimensions and estimates.
- If pressure drop is too high, reduce Eu or velocity.
- Export a CSV or PDF after you see results.
Example data table
| Scenario | Airflow | Velocity | Diameter D | ΔP | Fan kW | Cut size d50 |
|---|---|---|---|---|---|---|
| Small shed collector | 700 cfm | 18 m/s | 0.428 m | 1,264 Pa | 1.03 | 5.3 µm |
| Greenhouse cleanup | 1200 m³/h | 18 m/s | 0.430 m | 1,264 Pa | 0.70 | 5.3 µm |
| Large workshop duct | 0.60 m³/s | 20 m/s | 0.548 m | 1,560 Pa | 1.56 | 5.4 µm |
Why cyclone sizing matters in garden work
Garden shops generate mixed debris: soil dust, compost fines, mulch fibers, and sanding powder. A cyclone sized too small raises losses and noise, while one too large can let fines escape. Proper sizing keeps inlet momentum high enough for separation, yet low enough for your blower to sustain flow. It also reduces filter loading, which extends bag life and maintains suction during long cleanup sessions daily.
Selecting airflow and inlet velocity
Start with the airflow your fan delivers at real duct resistance, not the free-air rating. Choose an inlet velocity that matches your duct diameter and acceptable sound levels, commonly 15 to 22 m/s. Higher velocity increases separation but also increases pressure drop. If you frequently collect heavier chips, you can favor lower velocity and rely on gravity settling in the bin. Colder air slightly raises drop.
Dimensions that support predictable separation
The calculator uses proven high-efficiency proportions so every dimension scales from cyclone diameter. Inlet width and height define inlet area, the cone height promotes gradual contraction, and the vortex finder controls short-circuiting to the outlet. Use the generated dimensions to sketch sheet-metal patterns or select a commercial unit. Keep joints sealed and add a smooth inlet transition to minimize turbulence. Aim for a tight, round outlet.
Reading pressure drop and fan power
Pressure drop is estimated from an Euler number multiplied by dynamic pressure. Compare the result with your fan curve to confirm that target airflow is achievable. The power estimate converts flow and pressure into shaft demand using fan efficiency. If power looks high, reduce inlet velocity, shorten duct runs, enlarge elbows, or use a larger cyclone diameter. Always account for filter or muffler losses extra downstream.
Using cut size for practical dust control
The cut size metric indicates the particle diameter collected at roughly fifty percent efficiency, offering a quick comparison between scenarios. Finer capture improves when particle density increases, gas viscosity decreases, or effective turns rise. For garden use, focus on capturing nuisance respirable dust from dry soil and potting mixes. Validate performance by checking bin contents and observing visible haze near the exhaust during sweeping and potting.
FAQs
What airflow should I enter?
Use the airflow your blower delivers at working static pressure, measured in the installed duct system. Free-air ratings are usually higher and will oversize the cyclone.
What inlet velocity is best for garden dust?
Most systems perform well around 15–22 m/s. Lower values reduce noise and pressure drop, while higher values can improve separation if your fan can hold the flow.
Why is the pressure drop only an estimate?
It uses an Euler-number relationship with inlet velocity and gas density. Real losses change with roughness, leaks, inlet shape, bin level, and downstream filters.
Can I use this for wet leaves or sludge?
Cyclones work best with dry particulates. Wet material can stick, bridge, and increase re-entrainment. If moisture is unavoidable, add a pre-separator or moisture trap and clean the cone regularly.
How do I interpret the cut size d50?
d50 is the approximate particle size collected at 50% efficiency under simplified assumptions. Use it to compare setups, not as a guarantee. Validate with visible exhaust haze and filter loading.
What if the cyclone is too tall for my space?
Reduce diameter only if you can maintain airflow, or choose a lower-profile design. You can also relocate the bin, use a side inlet, or install the cyclone outdoors with weather protection.