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European transient cycle and natural gas engines: results and comments from the first tests
ISSN: 0148-7191, e-ISSN: 2688-3627
Published September 12, 1999 by Consiglio Nazionale delle Ricerche in Italy
Incoming regulation with the Euro3 phase introduces for the first time in Europe a transient test procedure named European Transient Cycle (ETC) for emission measurement of heavy duty engines. The results of the tests carried out on the Iveco 8469.21 natural gas engine according to the new procedure are discussed in this paper.
The comparison between transient test cycle and typical city bus operation, shows that the test procedure is representative of the real driving conditions. The additional requirement to run several tests with different gas qualities is discussed as well as the necessary adaptive control strategies.
The possibility of stoichiometric CNG engines with three-way catalyst and multi-point injection to meet the expected Enhanced Environmentally Friendly Vehicle (EEV) limits has been demonstrated as well as the capability to fulfill the test validation criteria.
The new regulation requires a very expensive dynamic test bench coupled to a dilution tunnel. The accuracy of an alternative measuring procedure has been also evaluated. The estimates effectuated on the base of real-time sampling of the raw tailpipe emissions resulted accurate enough compared with the measurements performed with full-flow dilution tunnel.
The Instituto Motori a dynamic test bench using an eddy current dynamometer, instead of an asynchronous machine, has been realised. The attempt to perform the new European transient cycle with this equipment has been only partially successful. In fact, even if the system including the eddy current brake has not been able to meet the test validation criteria, it can be usefully employed for engine development in dynamic conditions, unless of motored phases.