Study on the Effectiveness of the Tap Water Method with Water Vapor Elimination in Reducing Generation of Nano-sized Wear Particles from Railway Wheel-Rail Contact: Air Quality Analysis

This study investigates the effectiveness of the tap water method in reducing nano-sized wear particles (mass concentration) from wheel-rail contact for air quality improvement, by using a small-sized twin-disk rig at train speeds of 45 and 80 km/h. A diffusion dryer is used to eliminate the water vapor expected to be generated due to frictional heat in tap water application. To verify the effectiveness of tap water application, the experiment was repeated twice for each rotational speed under dry and wet conditions. A Fast Mobility Particle Sizer (FMPS) was used to measure the mass concentration of particles in the 5.6 to 560 nm range, and mean values were used to calculate particle size mass distribution and PM0.035, PM0.1, and PM0.56 to analyze air quality improvement. The results showed that mass concentrations of particles below 35 nm in size were reduced at both train speeds, and this is deemed to be the effect of water vapor elimination using the diffusion dryer. The reduction rates were 50% or higher at most particle sizes, and over 95% for PM0.56, higher than results from earlier studies. Therefore, the tap water method is deemed to be effective in improving air quality through the actual reduction of nano-sized wear particles generated in wheel-rail contact.