About 40% of air resistance is owed to bogies and wheels. They are therefore among the most promising areas for reducing running resistance of high-speed vehicles. The bogie fairings reduce air drag by eliminating flow separations at unshielded bogies and by shielding bogie components that would otherwise protrude into the rapid airflow along train sides. Due to the increased surface area using bogie fairings, frictional drag will be slightly greater. Since the form or pressure drag as predominating drag fraction is diminished, fitting a vehicle with bogie fairings will produce a significant reduction in drag as a whole.

Results of the ETR 500 test series

The full scale test series performed on the Italian ETR 500 with fairings revealed reductions in running resistance of approximately 10 % compared to the standard configuration without fairings. This figure refers to a speed range of 100 to 300 km/h and the train configuration planned to operate on the Italy – France routes, consisting of 2 locomotives and 8 trailer cars and which has a total length of 249.7 m. Reduced scale tests on a 1:7.5 model of ETR 500 using different fairing geometries indicate that the drag reduction could be further increased if the fairing design was aimed for the aerodynamic optimisation and not only for the retrofitting on the existing bogies.

Conclusion

A reduction potential of approximately 10% is confirmed by studies performed in the 1930s as well as Japanese experience from today’s Shinkansen 300X research train. In today’s high-speed trains running resistance accounts for over 60% of the energy consumption. This share will rise even more as further increases in speed are achieved. Bogie fairings therefore offer an overall energy efficiency potential of 6% per vehicle (and even more in the future).

Noise reduction

The DB, SNCF, FS joint research project aims at reducing noise emission originating from the bogie by 2 dB(A). It is not known whether this goal was achieved with the experimental bogie fairings tested in Italy.