Quantification of PM Emissions from Railways Results from Tests on different Test Benches for Rolling Stock

Railways are considered as a key transport system to counter the climate change because many railway tracks are already electrified and thus, the emissions from combustion processes could be eliminated. However, railways still emit particles due to abrasions and wear effects. The main sources are brakes, the wheel-rail contact and the contact between pantograph and contact wire. Information about the quantities of emitted particles at present are rare and the published data of PM10 emissions vary by a factor of ten. To improve the database and to eliminate uncertainties a series of tests on a pantograph test rig, a wheel-rail test bench and a brake test bench has been conducted in order to quantify the PM emissions from the abrasion process. Furthermore, chemical analysis of emitted particles have been done to receive information about the ingredients of the abrasion.
The tests on a pantograph test rig have been performed at Politecnico di Milano, Italy in July 2022. From this PM10 emission factors in the range of 0.14 – 0.62 g/km could be determined. The deviations are caused by differences in the contribution of electric arcs dependent on the applied contact force, driving speed and current intensity. The diameter of emitted particles is an indicator for the wear mechanism that causes the emission.
The tests on a wheel-rail test bench have been performed at DB Systemtechnik GmbH, Germany in August 2022. This includes a series of tests in order to quantify the emissions for a large number of real driving situations. A variation of train speed, axle load as well as of the curve radius has been applied. The emission monitoring covered the observation of particle mass of fractions PM10, PM2.5 and PM1, the continuous observation of the particle size distribution in the range of 5.6 nm to 35 µm as well as filter sampling in order to enable a chemical analysis of the particles composition. Dependent on the applied test configuration the emissions of the wheel-rail contact were determined in the range of 0.33 to 5.57 g/km. The average proportions of PM2.5 and PM1 in the PM10 emissions were 87.5% and 68.46% respectively. While in straight-line driving and in wide curves the number of axles is the most dominant parameter, in tight curves the bogie length becomes more relevant.
During 2022, a brake test bench has been set up at the Institute for Structural Durability and Rail Vehicle Technology, Graz University of Technology. The brake test bench can be used to test friction brakes for rail vehicles, with the possibility of also testing brake systems for commercial vehicles, passenger cars and aviation. A motor accelerates the power train of the test bench to any speed in the range of 0 - 3'000 min-1. This makes it possible to test the brakes of high-speed trains too, which are operated at a maximum speed of 500 km/h.
The brake caliper unit (or block brake unit) is mounted on a pendulum-mounted frame, which is supported on the ground by a load cell. Based on the measured force, the braking torque and subsequently the frictional force are inferred. The maximum braking torque is 35 kNm with a maximum braking power of 1.2 MW.
With this test bench disc brakes, block brakes and wheel disc brakes will be tested in March and May 2023, as well as the associated brake calipers, brackets and brake carriers.
The results arrived from this tests will be presented in this paper also.

This work is supported by German Centre for Rail Traffic Research at the Federal Railway Authority.