According to the Euro 7 proposal, particle emissions from passenger car brakes will be limited as their contribution to particle emissions in urban areas is significant with increasing trend. There are less studies available on city buses than on passenger cars but particle emissions from city buses are subject of research in a European funded project (Aerosolfd). Within this project a driving cycle for city buses is developed based on an extended short trip methodology. Real world driving measurements with buses in two European cities (Valladolid and Ancona) were conducted to generate a database for real world driving conditions. The real world database is analyzed regarding its joint speed-acceleration-distribution and disc temperature distributions. Based on this database, a driving cycle is developed that represents real world driving of city buses in those cities. Therefore, the velocity time series of those measurements is divided into short trips (section from one stop to n-th stop). The duration distribution of the trips is used make a pre selection of the short trips. The trips from this pre selection are assembled in all possible combinations. The joint speed-acceleration-distribution of all trip combinations is calculated and compared to the real world database. The short trips with smallest deviation between the joint speed-acceleration-distributions are chosen as candidate cycles and cycles for all bus line are generated from these candidate cycles. The cycles are tested on a CV-dynamometer with particle measurement devices to determine particle mass emission factors, particle number emission factors as well as size distributions.
Dr.-Ing. Hartmut Niemann, Research Application Engineer, Link Engineering Co.