Abstract
Four of these Particulate Reduction Systems (PMS) were tested on a passenger car and one of them on a HDV. Expectation of the research team was that they would reach at least a PM-reduction of 30% under all realistic operating conditions. The standard German filter test procedure for PMS was performed but moreover, the response to various operating conditions was tested including worst case situations. Besides the legislated CO, NOx and PM exhaust-gas emissions, also the particle count and NO2 were measured. The best filtration efficiency with one PMS was indeed 63%. However, under critical but realistic conditions filtration of 3 of 4 PMS was measured substantially lower than the expected 30 %, depending on operating conditions and prior history, and could even completely fail. Scatter between repeated cycles was very large and results were not reproducible. Even worse, with all 4 PMS deposited soot, stored in these systems during light load operation was intermittently blown-off. Due to these stochastic phenomena the behaviour of these systems is hardly predictable. Furthermore the provision of NO2, through catalysis ahead of the filter or in the filter matrix, is inherent in these systems. Some of this secondary NO2 is emitted. Cost/benefit ratio is high compared to full-flow filters and Diesel engines equipped with partial-flow filters are inferior to SI engines regarding global warming potential. Based on these findings it is concluded that the sustainable performance of partial-flow filters is not yet determined.
Highlights
Full-flow filters (FFF) have become a standard
Specyfikacja niemiecka [5], reduction measured over 3 New European Driving Cycles którą przyjęła Holandia i inne kraje, bazuje na trzykrotnych (NEDC) in the new state, after 2000 km, and after 4000 km pomiarach redukcji emisji cząstek stałych w testach NEDC
The filtration decreases substantially for both systems after the first city driving period. This deterioration continues in the second stage but is mostly corrected through regeneration during the so-called worst case test (WC)
Summary
Wall flow honeycomb filter media, used in this concept are reaching filtration efficiencies exceeding 99.9% [1]. These are fitted ex-factory to European passenger cars and USA trucks [2, 3]. Retrofit filter systems with active regeneration, a prerequisite for dependable operation, are still rather complex, bulky and costly and prohibitive for retrofitting in-use passenger cars. To diminish emissions, in countries with a high Diesel car population, environmental policy requires simpler and less costly retrofit systems. These shall enable at least 30% curtailment of the particle mass (PM) emission, and correspondingly
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