Slanted silencers typically require 24% more headroom than MoJets®
If additional head room is available in a tunnel, then additional thrust can be produced by specifying larger-diameter jet fans, or simply by moving the jet fans away from the bounding tunnel surfaces (soffit and side-walls).
The jet fan thrust is reduced by slanted silencers
This is due to flow separation at the junction between the slanted silencers and the fan housing, and because of horizontal reaction forces generated at the downstream silencer due to flow impingement and aerodynamic friction.
Premature fan bearing failure
Vibration due to flow separation within slanted silencers can cause premature fan bearing failure.
Additional power consumption
Due to internal flow separation, impingement and friction losses, jet fans with slanted silencers absorb more power than conventional jet fans.
Restricted silencer length
Due to the requirement not to encroach upon the tunnel traffic gauge, silencer lengths are limited with slanted silencers. This restricts the sound attenuation that can be achieved.
| Technology | Deflect jet | Compact | No jet throw extension | No noise regeneration | No deflector metal fatigue risk | No additional power | No loss of bench thrust | No risk of bearing damage |
|---|---|---|---|---|---|---|---|---|
| MoJet | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
| Conventional | ❌ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ | ✔ |
| Deflectors | ✔ | ✔ | ❌ | ❌ | ❌ | ❌ | ❌ | ✔ |
| Slanted silencers | ✔ | ❌ | ✔ | ✔ | ✔ | ❌ | ❌ | ❌ |
None of these drawbacks are present with the MoJet®, which is the most modern jet fan technology available for enhancing in-tunnel thrust.
View our technical paper on jet fan technology
Discover the benefits of the MoJet®
The reversible MoJet® tunnel ventilation system can increase the in-tunnel aerodynamic thrust by up to 100%
