Experiences with partial-flow filters to reduce the solid particle emissions from diesel engines

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.

Physico-Chemical Characterization of Fine and Ultrafine Particles Emitted during Diesel Particulate Filter Active Regeneration of Euro5 Diesel Vehicles

“…The main role of the DOC is to oxidize CO and unburnt organic compounds. The DOC, however, oxidizes NO to form NO 2 , which assists PM oxidation in the DPF. − The operation principle of DPF systems is based on the separation of the airborne particles from the gas stream through filtration or physical deposition (i.e., inertial impaction, interception, Brownian diffusion, and thermophoresis mechanisms). ,− …”

Evaluation of toxicity of hydrocarbons emitted by Euro 3 and Euro 6 vehicles at idle conditions by means of equivalent toxicity coefficients

“…Research on filtration 33 efficiency for various types of available particulate filters are presented in publication. 37 They show that three out of four tested filters do not meet the assumed expectations. Their filtration efficiency in the tests carried out was below 30%.…”