Ricardo was contracted by the UK Department for Transport (DfT), to develop a “proof-of-concept” system for measuring mass and number of non-exhaust emissions (NEE) of particles, under real-world driving conditions. The project is planned to comprise three phases. The initial, recently completed phase, saw the development of on-board approaches to sample and measure brake (and also tyre wear) particles from light-duty vehicles. Brake wear particles were sampled from a Volkswagen Caddy van, extracted from a fixed volume created by enclosing the pad and disc. Three different enclosure designs were developed. Particles produced by braking events were continuously transported, near-isokinetically, from the sampling point to a sample tunnel, where measurements of number-weighted particle size distributions were determined by two Dekati ELPI+ systems. ELPI+ systems function by separating particles into different size ranges according to their inertial properties. Particles are charged at the ELPI+ inlet. Charges carried by the particles are transferred to electrometers associated with each size range, allowing real-time size distribution and number concentration data to be acquired. One ELPI+ was heated, with the other at ambient temperature, further allowing discrimination between particle volatilities. A Dekati eFilter based upon diffusion charging was used to provide a cumulative PM mass sample and a real-time mass signal. Filters collected were subjected to basic chemical analyses. To avoid particle losses from the brake enclosure, and to manage temperatures, a constant stream of HEPA filtered air was supplied to move particles to the sample tunnel, this also providing positive pressure within the enclosure and preventing particle ingress from ambient air. Consequently, background particle levels were negligible. Measurements were made on the chassis dynamometer from a bespoke drive cycle constructed to produce high particle emissions, from road tests in an urban area, and from repeated braking events on a test track. Results showed strong signals of particle release from brakes in response to braking pressure signals and road speed data recorded from the vehicle On-Board Diagnostics, with both solid and volatile particles produced. Particle number emissions from brakes were of a similar order to published values from brake dynamometer testing, while mass emissions sampling efficiency appeared to be consistent with collecting PM2.5.
Mr. Jon Andersson, Global Technical Expert Emissions Measurements and Standrads, Ricardo UK, Automotive and Industrial; Dr. Louisa Kramer, Senior Consultant, Ricardo Energy and Environment; Mr. Michael Campbell, Principal Consultant, Ricardo Energy and Environment; Dr. Ian Marshall, Associate Director, Ricardo Energy and Environment; Mr. Jason Southgate, Principal Consultant, Ricardo Energy and Environment; Dr. John Norris, Principal Consultant, Ricardo Energy and Environment; Mr. Gary Waite, Principal Engineer - Chassis, Ricardo UK, Automotive and Industrial; Mr. Simon de Vries, Development Engineer, Ricardo UK, Automotive and Industrial; Dr. David Miles, Head of Environmental Standards, UK Department for Transport; Dr. Claudio Chesi, Senior Technical Specialist, UK Department for Transport; Dr. David Deakin, Technical Director, Arup AECOM Consortium