MoJet® Design Options

MoJet® Design Options

MoJets® allow the ventilation designer much more design flexibility than with conventional jetfans. This design flexibility can make all the difference to a successful ventilation design. Some typical design options are presented below.

Shorter longitudinal distances between fans

MoJets® can be arranged at typically half the longitudinal distance between successive fans, compared to conventional jetfans. This is because the jet dissipates into the tunnel air much more rapidly with the MoJet®, compared to a conventional jetfan. Shorter longitudinal distances allow reductions in cable lengths, and hence significant savings.

Changed fan diameter

Since MoJets® deliver greater in-tunnel aerodynamic thrust than conventional jetfans, a smaller fan diameter may be selected while still delivering the required thrust. MoJets® can be installed very close to tunnel walls and soffits, with only minimal clearance for maintenance and tolerances being required. This may allow the designer to increase the fan diameter, while still not encroaching upon the traffic space. Increasing the fan diameter allows additional thrust to be obtained, or to significantly reduce the power consumption for the same thrust. It may also be possible to specify four-pole motors to reduce the fan speed while still achieving the required thrust – this can reduce the power consumption and the noise emissions substantially.

Jet Alignment

MoJet® nozzles can be installed at a defined angle about the fan axis, to throw the jet in any preferred direction – for example, towards the corner  between the tunnel wall and floor. This can be a very useful device for enhancing the thrust, by avoiding the bounding tunnel surfaces. MoJet® nozzles can also be set at an angle in order to reduce the interference of adjacent jets, thus enhancing the installation factor.

Single or Dual MoJet® Nozzles

In many tunnels, there is a preferred direction of traffic movement, which is also the usual direction of ventilation. Some (limited) ventilation capacity may still be required in the opposite direction, in order to reduce the risk of smoke being re-ingested into the neighbouring portal. For such applications, a single MoJet® nozzle can be specified for the fans. Where full thrust reversibility is required, dual MoJet® nozzles should be specified.

Silencer Lengths

MoJet® nozzles contain silencing material, and can be designed to any required length to satisfy acoustic requirements.

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