Reduction of Air/Wind Energy Transfer to High Speed Trains
Vehicle designs have traditionally incorporated linear shapes to reduce aerodynamic forces. I.e. base region pressure drag, parasite drag, wake vortex shedding and pressure rise at underpasses and tunnels. However, wind is a non-linear force that increases vehicle instabilities, adding greater rolling resistance, fuel consumption and damage/wear to wheels or tires. For high speed trains (HSTs, >200km/hr.) these instabilities cause wheel flanges to alternatively scrub and release the rail, causing costly corrugation damage.
This proposal intends to relieve three fundamental problems facing HSTs (or highway vehicles longer than 8 meters).
Open Country Operations:
HSTs at speed create base pressure drag regions between carriages and at the train rear. Non-linear gusting and swirling winds striking the vehicle will create vortex shedding and instability increasing rail scrubbing and rolling resistance.
HSTs approaching and departing under/over pass environs create a distinct pressure rise and fall. A static pulse of energy is formed that transfers to various “grab” points along its length (e.g. gaps between carriages) as it passes. The pulse incites vibration and harmonics that cascade the length of the train through the carriage couplings.
An energy pulse will develop similar to overpasses. However, on entering air is confined by the tunnel walls and pressures rise drastically, similar to a piston in a cylinder. This pressure will continue to rise as a function of speed, tunnel length and venting capabilities until speed is reduced or the tunnel exit approaches allowing for rapid pressure release.
The proposed solution incorporates random surface placement of irregular shaped vortex generators (VGs) (Figure A) to reduce aerodynamic drag forces, the detrimental formation of harmonic, resonant frequencies and tunnel induced pressure rise damage.
The elongated nose of the HST locomotives requires special attention.
Random patterns of smaller VGs at the tip of the locomotive will be followed by progressively larger VGs up to the widest and tallest cross-section of the locomotive. The smaller VGs disturb the initial local onset airflow allowing larger VGs mounted downstream to continue to lift and spin the airflow. Additional VGs added in random patterns along the roof and sides of the carriages will reduce side vortices and aerodynamic drag. HST bluff surfaces would also be fitted with Airtabs® around the perimeter to address base pressure drag. (Figure B)
Construction: Injection molded plastic, composite or metal alloy. Attached by double sided tape or weld.
Cost: Inexpensive to manufacture and install.
Competition: None. No competitive products on the market.
Device Placement: See Figures. VGs on tunnel walls may be beneficial. Tunnel dependent. Analysis required.
Fuel: Less drag increases fuel efficiency.
Improved Aerodynamics: Yields reduced dirt and snow buildup, less weight, reduced cleaning costs.
Wheels/Tires: Reduced wheel scrubbing, less corrugation, increased life span, reduced maintenance costs.
Engine Life: Enhanced vehicle stability improves engine performance through reduced small frequency load variations.
Design Safety: Devices shaped for friendly passenger interface.
Other Benefits: Reduce aerodynamic impact on adjacent bike trails, crossings and pedestrians.