What a jet fan is
A jet (impulse) fan creates a high-velocity jet that entrains the surrounding air. Several fans, placed under the slab according to the calculation, form a stable flow from the supply openings to the exhaust shaft. Synonyms found in design documents: impulse fan, jet-stream fan, jet fan.
Wolter series
| Series | Type | Sizes | Thrust (high / low speed) | Airflow | Fire resistance |
|---|---|---|---|---|---|
| JFUO / JFRO | axial, low oval casing with silencers | 300, 370; casing L 2,250 mm or S 1,200 mm; height 343–415 mm | JFUO: 28/7 — 68/17 N; JFRO: 24/6 — 53/13 N | 2,448–9,504 m³/h | F300, F400 (120 min) |
| JFUC / JFRC | axial, round casing 1,800 mm long | 280, 315, 355, 400; casing Ø 400–506 mm | JFUC: 18/5 — 85/21 N; JFRC: 15/4 — 73/18 N | 1,800–11,016 m³/h | F300, F400 (120 min) |
| JFC | radial, with nozzle and adjustable deflector | thrust classes 30–100 N; height 221–325 mm | 31/7.7 — 104/26 N | 2,664–10,656 m³/h | F300; F400 — on request |
The letter U means a unidirectional fan, R — a fully reversible one (guide vanes on both sides). Reversing makes it possible to change the flow direction depending on where the fire is.
JFUO / JFRO — for car parks with limited headroom
The casing is built as a single silencer of oval cross-section. A two-speed motor (2,880 / 1,440 rpm, IP55) provides economical ventilation at low speed and full thrust during a fire. An important operating advantage: the motor and impeller unit slides out of the casing, so maintenance does not require removing the fan. The long casing L reduces noise — important for residential complexes.
JFUC / JFRC — the highest thrust among axial fans
The round casing, 1,800 mm long, acts as a silencer along its entire length. Guide vanes on the discharge side tilt the jet downwards so that the flow passes under the slab beams. Fewer, more powerful fans simplify cable routes and controls.
JFC — when there is hardly any headroom
A radial impeller with a nozzle forms a flat jet at a casing height from 221 mm. An adjustable deflector directs the flow under the beams or along the slab. Motor 1,440 / 720 rpm.
How jet fans are selected
The number and layout of the fans are determined by calculation and, for smoke extraction, as a rule by CFD modelling. The calculation takes into account the car park geometry and beams, the positions of the shafts, the design fire size, evacuation scenarios and the requirements of DBN V.2.3-15 (the Ukrainian State Building Norm for car parks and garages). For more detail, see the section on jet fan (impulse) ventilation of car parks.
Documentation
The technical data are taken from the manufacturer’s brochure “Jet Fans” (2019). Documents for a specific version are provided during selection.