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Tunnel and Jet Fans | SDS, SDS(R) & PYHL-14A | YONGFAN
Longitudinal Propulsion · Jet Thrust

Tunnel and Jet Fans: Longitudinal Ventilation and Space Induction

Tunnel and jet fans operate by momentum transfer rather than duct static pressure: high-velocity discharge jets induce surrounding air mass movement along tunnels or across open underground spaces.

Compare YONGFAN SDS (unidirectional, 191 to 3,046 N thrust, 7.9 to 71.8 m³/s), SDS(R) (100% reversible within 30s), and PYHL-14A jet-induction car park fans (280 °C / 30 min fire rating) across aerodynamic thrust formulas, silencer acoustics, mounting brackets and emergency smoke control.

3 Key Series SDS · SDS(R) · PYHL-14A
Thrust Scope 191 – 3,046 N Static Thrust
Jet Velocity 16.0 – 45.5 m/s Exit Jet
Emergency Smoke 280 °C / 30 min · GB/T 13351
Choose a Tunnel / Jet Fan Review Thrust Principles
Longitudinal tunnel jet fan installation in modern traffic tunnel
Momentum Transfer Propulsion SDS · SDS(R) Reversible · Integrated 1D/2D Silencers
01 / Aerodynamic Physics

Tunnel Fans Move Air by Momentum Transfer, Not Duct Resistance

In longitudinal tunnel and space-induction systems, there are no connecting duct runs. The fan discharges a high-velocity air jet that entrains and pushes the entire tunnel air column toward portals or shafts.

Standard duct fan selection relies on static pressure (ΔPs) to overcome duct friction and component losses. For tunnel and jet fans, the decisive engineering parameter is Thrust (Newtons) and Jet Velocity ($V_j$).

As the high-velocity jet leaves the fan nozzle at 16 to 45.5 m/s, it transfers momentum to the slower ambient air column, creating an induced longitudinal velocity ($V_t$) through the tunnel bore or parking deck. The effective thrust delivered to the air column depends on the velocity differential, tunnel cross-section ratio, and wall/ceiling installation clearances.

YONGFAN manufactures heavy-duty tunnel equipment: the SDS Series (unidirectional, 191–3,046 N), the SDS(R) Series (100% reversible within 30s), and the PYHL-14A Series for enclosed parking garages with 280 °C / 30 min fire certification.

Tunnel ventilation jet fan testing and mounting brackets
Longitudinal jet induction profile, mounting brackets and safety chain hardware.

High Static Thrust Output

Develops 191 to 3,046 N of static thrust across Ø630 to Ø1600 mm sizes, moving thousands of tons of tunnel air column without distribution ducts.

Thrust Scope: 191–3,046 N · ISO 13350 Tested

SDS(R) 100% Reversibility

Symmetrical aerodynamic impeller allows full airflow reversal within 30 seconds for bidirectional tunnels or emergency smoke redirection.

Reversal: 100% thrust reversed within 30s

Integrated 1D / 2D Silencers

Factory-mounted acoustic silencers (1D or 2D length) achieve 9 to 14 dB(A) sound attenuation, keeping roadside acoustic levels within safety limits.

Acoustics: -9 to -14 dB(A) attenuation

Emergency Fire Rating

Class H insulation and certified high-temperature motor enclosures guarantee full continuous thrust during 280 °C / 30 min tunnel fire emergencies.

Fire Rating: 280 °C / 30 min certified build

Tunnel & Jet Fan Selection Architecture

Select based on tunnel traffic type, reversibility, parking deck layout, and required emergency smoke containment strategy.

01 SDS: Unidirectional Traffic Tunnels
02 SDS(R): 100% Reversible Tunnels
03 PYHL-14A: Ductless Car Parks
04 Effective Thrust $N_e$ Equation
02 / Technical Metrics

Effective Thrust $N_e$: The True Metric of Tunnel Performance

Catalog static thrust ($N_s$) is measured at zero tunnel air velocity. In a moving tunnel airstream, effective thrust ($N_e$) governs longitudinal ventilation.
Spectrum 01 / SDS Series

SDS Unidirectional Scope

7.9 to 71.8 m³/s airflow, 191 to 3,046 N static thrust, and 16.0 to 45.5 m/s jet velocity across Ø630 to Ø1600 mm diameters. Motors range from 4 to 90 kW (Class H, IP55, 380V).

Spectrum 02 / SDS(R) Reversible

SDS(R) Reversible Scope

100% reversible aerodynamic profile with 4–6% thrust penalty vs SDS. Reversal occurs within 30s without motor damage for bi-directional road tunnels.

Spectrum 03 / PYHL-14A Induction

PYHL-14A Space Induction

Sizes 2.5A to 14A for enclosed car parks, metro concourses, and shopping malls. 280 °C / 30 min smoke rating provides reliable emergency extraction without ductwork.

Effective Thrust Formula: $N_e = N_s imes (1 – V_t/V_j) imes C_2 imes C_3$

ISO 13350 / GB/T 13351 longitudinal calculation protocol.

Calculation Model
Velocity Differential: $(1 – V_t/V_j)$
Dynamic Momentum
Accounts for relative velocity between jet ($V_j$) and moving tunnel air ($V_t$).
Area Ratio Factor: $C_2$
Expansion Ratio
Ratio of fan outlet nozzle area to tunnel cross-sectional bore area.
Installation Clearance: $C_3$
Wall / Ceiling Loss
Reduction factor due to boundary layer friction near tunnel ceiling or walls.
1. Tunnel Geometry Cross-section ($m^2$) & length (m)
2. Critical Velocity $V_k$ smoke backlayering limit
3. Total Thrust Required Sum of $N_e$ overcoming drag
4. Fan Selection & Silencer SDS vs SDS(R) & 1D/2D silencers
03 / Product Lineup

Choose the Tunnel Fan Family by Thrust and Traffic Flow

Detailed engineering review of SDS unidirectional, SDS(R) reversible, and PYHL-14A car-park jet-induction fans.
Family 01 · SDS Series Unidirectional · Up to 3,046 N Thrust

SDS Series Unidirectional Tunnel Jet Fan

The SDS Series Tunnel Jet Fan is engineered for unidirectional highway, railway, and metro transit tunnels requiring high longitudinal propulsion and smoke purging capacity.

Published performance spans 7.9 to 71.8 m³/s airflow (28,440 to 258,480 m³/h), 191 to 3,046 N static thrust, and 16.0 to 45.5 m/s jet discharge velocity across impeller diameters from Ø630 to Ø1600 mm. Powered by heavy-duty 4 to 90 kW Class H motors (IP55), SDS fans feature factory-fitted 1D or 2D cylindrical silencers reducing sound levels by -9 to -14 dB(A), heavy hot-dip galvanized casings, and tested compliance with GB/T 13351 and ISO 13350.

Thrust & Jet Velocity
191 – 3,046 N · 16.0 – 45.5 m/s
Diameters & Power
Ø630 – Ø1600 mm · 4 – 90 kW
Silencer Attenuation
1D / 2D Silencers: -9 to -14 dB(A)
Fire Temperature Rating
280 °C / 30 min (Class H Insulation)
Traffic Flow Restriction: SDS is aerodynamically optimized for single-direction thrust. If the tunnel operates with bi-directional traffic or requires smoke reversal against headwinds, specify SDS(R).
View SDS Product Details Request SDS Sizing
SDS Standard Frame Scope
SDS-No.6.3 ~ 8.0 Ø630 – Ø800 mm 191 – 680 N
SDS-No.9.0 ~ 11.2 Ø900 – Ø1120 mm 520 – 1,450 N
SDS-No.12.5 ~ 14 Ø1250 – Ø1400 mm 1,100 – 2,280 N
SDS-No.16.0 Ø1600 mm Up to 3,046 N

*Hot-dip galvanized casing, mounting brackets & safety chains included.

Family 02 · SDS(R) Series 100% Reversible · Bi-Directional Tunnels

SDS(R) Series Reversible Tunnel Jet Fan

The SDS(R) Series Reversible Tunnel Jet Fan provides full 100% bidirectional thrust capability for tunnels with two-way traffic flows or systems requiring rapid emergency airflow reversal.

Constructed with symmetrical aerofoil blades and dual-ended bellmouths, SDS(R) allows electrical motor reversal within 30 seconds to redirect smoke plumes away from trapped motorists. Due to symmetrical blade profiling, it exhibits a minor 4–6% thrust penalty compared to unidirectional SDS fans for the same motor kW, covering diameters from Ø630 to Ø1600 mm and powers from 4 to 90 kW.

Reversibility Performance
100% Full Thrust in Both Directions
Reversal Time
≤30 seconds switchover time
Thrust Difference vs SDS
~4–6% lower thrust per motor kW
Standards & Fire Rating
280 °C / 30 min · ISO 13350 tested
VFD / Starter Coordination: Rapid reversal requires coordinated starter controls or dynamic braking VFD drives to prevent motor inrush current spikes during 30s direction switches.
View SDS(R) Details Request SDS(R) Sizing
SDS(R) Standard Scope
SDS(R)-6.3 ~ 8.0 Ø630 – Ø800 mm 180 – 640 N
SDS(R)-9.0 ~ 11.2 Ø900 – Ø1120 mm 490 – 1,380 N
SDS(R)-12.5 ~ 14 Ø1250 – Ø1400 mm 1,040 – 2,150 N
SDS(R)-16.0 Ø1600 mm Up to 2,880 N

*Symmetrical silencers on both ends ensure balanced forward/reverse acoustics.

Family 03 · PYHL-14A Space Induction · 280 °C / 30 min Fire

PYHL-14A Jet-Induction Fan (Car Parks & Concourse)

The PYHL-14A Jet-Induction Fan eliminates complex duct networks in enclosed underground car parks, metro public areas, logistics basements, and shopping malls by using high-momentum induction air jets.

Available in sizes 2.5A to 14A, PYHL-14A fans are suspended from ceiling slabs at strategic intervals, sweeping vehicle exhaust gases (CO/NOx) toward main exhaust shafts during normal ventilation. In a fire emergency, the certified 280 °C / 30 min build maintains smoke plume direction, preventing smoke spread into emergency escape corridors.

Application Target
Ductless underground car parks & malls
Sizes & Mounting
Sizes 2.5A – 14A · Ceiling suspended
Fire Certification
280 °C / 30 min continuous smoke duty
Duct Savings
Eliminates 80%+ sheet metal ductwork
Car Park Headroom Note: Slimline low-profile casing ensures installation within tight car-park ceiling clear heights without obstructing vehicle navigation.
View PYHL-14A Details Request Car Park CFD Sizing
Car Park System Scope
PYHL-2.5A ~ 4.0A Small Bays CO Exhaust Induction
PYHL-5.0A ~ 8.0A Medium Decks Main Driveway Thrust
PYHL-10A ~ 14A Large Basements High-Velocity Transfer

*CFD smoke simulation layout support provided upon request.

04 / Selection Matrix

Tunnel & Jet Fan Family Routing & Comparison Table

Cross-reference YONGFAN SDS, SDS(R) and PYHL-14A fans by application duty, documented aerodynamic boundary, and first technical input to confirm.
Product Family What It Solves Published Capability First Input to Confirm Specification Action
SDS Series Tunnel Jet Fan Unidirectional
Longitudinal propulsion in unidirectional highway and rail tunnels
191–3,046 N Thrust · 7.9–71.8 m³/s · Ø630–1600 mm
 Required total thrust ($N_e$), tunnel cross-section ($m^2$), and traffic direction Configure SDS
SDS(R) Series Reversible Jet Fan 100% Reversible
Longitudinal ventilation in bi-directional traffic tunnels & reversible smoke control
100% Reversible thrust · Reversal ≤30s · Ø630–1600 mm
 Bi-directional traffic profile and maximum switchover time Configure SDS(R)
PYHL-14A Jet-Induction Fan Car Park Induction
Ductless space induction in underground car parks, metro concourses & malls
Sizes 2.5A–14A · 280 °C / 30 min Fire Rating
 Car park layout, ceiling headroom, and CO/smoke extraction zoning Configure PYHL-14A
Rule 01

Traffic Profile Match

Specify SDS for one-way traffic tunnels. Specify SDS(R) for two-way traffic or bidirectional emergency smoke purging.

Rule 02

Car Park Induction

For parking decks, choose PYHL-14A to eliminate ductwork clashes with plumbing/sprinkler runs while maintaining 280 °C / 30 min smoke duty.

Rule 03

Silencer Length (1D vs 2D)

Select 1D silencers for compact mounting clearance; select 2D silencers for maximum acoustic reduction (-14 dB(A)) near tunnel portals.

Rule 04

Effective Thrust Verification

Never rely solely on static thrust ($N_s$). Calculate $N_e$ with moving air velocity ($V_t$) and wall boundary friction factors ($C_3$).

05 / Procurement Protocol

Project Data Required for Tunnel & Jet Fan Selection

Provide tunnel cross-section, traffic speed, portal wind pressure, and fire temperature requirements before requesting fan sizing.
STEP 01

Tunnel Dimensions & Flow

Provide length (m), cross-section ($m^2$), portal elevation, and design longitudinal velocity ($V_t$).

STEP 02

Thrust & Reversibility

Confirm calculated total thrust (N) and whether 100% reversible operation (SDS(R)) is required.

STEP 03

Mounting & Clearances

Specify ceiling clearance, wall standoff distance, anchor bolt load ratings, and safety chain brackets.

STEP 04

Emergency Smoke & Noise

Confirm fire temperature rating (280 °C / 30 min), silencer package (1D/2D), and 380V/50Hz supply.

Engineering Checklist

12 Parameters for Tunnel & Jet Fan Selection

Send your tunnel or car park parameters. YONGFAN application engineers will verify effective thrust calculations, fan spacing, and submittal drawings.

1. Tunnel / Car Park Cross-Section ($m^2$)
2. Tunnel Length & Longitudinal Grade
3. Design Tunnel Velocity ($V_t$ m/s)
4. Total Thrust Required (N)
5. Traffic Flow (One-Way vs. Two-Way)
6. SDS Unidirectional vs. SDS(R) Reversible
7. Silencer Specification (1D or 2D)
8. Emergency Fire Duty (280 °C / 30 min)
9. Ceiling Clear Height Limits (mm)
10. Ambient Air Conditions & Humidity
11. Power Supply (380 V / 50 Hz 3-Phase)
12. Mounting Bracket & Safety Anchor Needs
06 / Manufacturing Consistency

YONGFAN Tunnel Fan Manufacturing & Thrust Rig Testing

Full-scale thrust rig testing to ISO 13350, dynamic balancing of cast alloy impellers, hot-dip galvanizing, and Class H motor verification ensure reliable operation.
Precision Fabrication

Impeller Dynamic Balancing

Cast aluminum aerofoil impellers undergo dynamic balancing to ISO G2.5 standards, preventing high-speed vibration in suspended installations.

Thrust Rig Verification

ISO 13350 Thrust Testing

Fans are measured on dedicated thrust test rigs to verify static thrust (N), discharge jet velocity, electrical power factor, and acoustic attenuation.

Corrosion Protection

Hot-Dip Galvanized Casings

Heavy steel casings and silencers receive hot-dip galvanizing or multi-coat epoxy systems to resist harsh tunnel exhaust atmospheres and vehicle washdown.

Safety Hardware

100% Bracket & Safety Chains

Every tunnel jet fan includes structural anti-vibration mounting brackets, high-tensile anchor hardware, and redundant stainless-steel safety chains.

Bespoke Tunnel Engineering: Full CFD simulation modeling, custom pitch angles, dual-speed motors, and tunnel SCADA integration diagrams provided upon request. Configured Dispatch: Lead times quoted based on model, frame size, motor build, quantity and project specifications.
07 / Engineering Knowledge

Tunnel & Jet Fans Frequently Asked Questions

Direct engineering answers regarding thrust calculation, SDS vs SDS(R) differences, silencer effectiveness, and car-park induction design.

Why are tunnel fans rated in Newtons (thrust) rather than Pa?

Because tunnel fans operate without ductwork: they propel air longitudinally through open space via momentum transfer. Static thrust (N) directly measures the propulsion force exerted on the tunnel air column.

What is the difference between SDS and SDS(R)?

SDS is unidirectional for one-way traffic tunnels. SDS(R) is 100% reversible within 30 seconds for two-way traffic or bidirectional emergency smoke management, with a ~4–6% thrust penalty vs SDS.

What is the thrust and airflow range of the SDS family?

SDS covers 191 to 3,046 N static thrust and 7.9 to 71.8 m³/s airflow (28,440–258,480 m³/h) with discharge velocities from 16.0 to 45.5 m/s.

How much noise reduction do the 1D and 2D silencers provide?

Factory-mounted cylindrical silencers provide -9 to -14 dB(A) acoustic attenuation depending on silencer length (1D or 2D).

How does PYHL-14A work in car parks?

PYHL-14A produces high-velocity induction jets that sweep CO and smoke across open parking bays toward main vertical exhaust risers, eliminating bulky sheet metal duct runs.

Are YONGFAN tunnel fans fire rated?

Yes. SDS, SDS(R) and PYHL-14A are built with Class H insulation and high-temperature bearings certified for 280 °C / 30 min continuous smoke exhaust.

How is the effective thrust ($N_e$) calculated?

Using $N_e = N_s imes (1 – V_t/V_j) imes C_2 imes C_3$, where $N_s$ is static thrust, $V_t$ is tunnel velocity, $V_j$ is jet exit speed, $C_2$ is cross-section ratio, and $C_3$ is installation friction.

What safety mounting hardware is supplied?

All units include anti-vibration ceiling brackets, high-tensile anchor hardware, and redundant stainless-steel safety drop chains to guarantee structural retention.

Can SDS fans be used in metro train tunnels?

Yes. SDS and SDS(R) fans are widely installed in subway tunnels, underground rail corridors, and portal transition zones to manage piston-effect airflows and emergency smoke.

08 / Application Boundaries

Tunnel & Jet Fans Are Specialized Longitudinal Systems

Specify a jet fan when air must be propelled through open un-ducted tunnels or parking decks. For ducted networks, select conventional in-line fans.
Boundary 01 / Ducted Car Parks

Ducted Mixed-Flow

If the basement uses a traditional ducted exhaust distribution network, specify SWF-II or HL3-2A instead of jet induction.

Boundary 02 / Shaft Exhaust Fans

Main Riser Axial Fans

Tunnel portal and shaft extraction stations require massive stationary DTF Axial Fans or 4-72 Centrifugal Fans to discharge air outside.

Boundary 03 / Rooftop Exhaust

DWT Roof Fans

If exhausting directly through building roof slabs, select weatherproof DWT-I or DWT-II Roof Fans.

Boundary 04 / Hazardous Atmosphere

Explosion-Proof Jet Fans

If flammable gases (methane, solvent vapors) are present, specify certified Explosion-Proof Tunnel Jet Fans with ExdIIBT4 ratings.

09 / Engineering Handoff

Select the Right Tunnel / Jet Fan for Your Project

You do not need to calculate effective thrust alone. Send your tunnel cross-section, length, portal wind conditions and emergency fire criteria — our application engineers will confirm the optimal SDS, SDS(R) or PYHL-14A fan layout and provide complete submittal packages.

Tunnel Cross-Section ($m^2$) & Length (m) Static & Effective Thrust (N) SDS (Unidirectional) vs. SDS(R) (Reversible) PYHL-14A Car Park Induction 1D / 2D Silencer Package 280 °C / 30 min Smoke Duty 380 V / 50 Hz 3-Phase
Request a Tunnel Fan Quote Go to Selection Center Contact Technical Support
Tunnel ventilation engineers reviewing longitudinal jet fan layouts
Direct Application Engineering Support
Thrust verification calculations, acoustic silencer models, mounting drawings & CFD layout assistance.
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