Measurements in support of modelling the VELA-2 experimental facilities

This document reports the results of measurements conducted at the VELA-2 laboratories of the JRC in February 2007. The aim of the experimental campaign was to provide the necessary experimental data to model aerosol processes from the vehicle's exhaust tailpipe to the sampling point at the full dilution tunnel. The measurements included particle and temperature profiles at the tailpipe, at the end of the exhaust gas transfer tube to the dilution tunnel (anaconda), at the diaphragm of the dilution tunnel, 1,5 tunnel diameters downstream the diaphragm and 10 tunnel diameters downstream the diaphragm (normal sampling point). Two steady state speeds were used (50 and 120 km/h) and flow rates at the dilution tunnel of 6 and 12 m3/min. Non-volatile and total particle number and mass concentrations were measured according to the protocol of the Particulate Measurement Programme. The results showed that the main changes of particle number distributions are observed along the transfer tube from the tailpipe to the dilution tunnel (anaconda). Afterwards the particle number distributions remain almost constant. However, low dilution at the dilution tunnel (flow rate of 6 m3/min) leads to a further small particle number distribution change.