Ageing of catalytic exhaust gas aftertreatment systems for compression ignition engines is conducted on the engine dyno for stationary engine tests. Such tests are characterised by time and cost savings in comparion to on-road road ageing tests. Diesel oxidation catalysts (DOCs), Diesel particulate filters (DPFs) and selective catalytic reduction systems (SCR) are submitted to ageing tests.
Ageing of oxidation catalysts (DOC) is conducted over work cycles with elevated exhaust temperature. The temperature and mass flow of the exhaust can be regulated, depending on the test requirements.
Ageing of particulate filters (DPFs) uses an accelerated ageing procedure. Exhaust with an elevated number of solid particles enters the filter, which shortens the time required for accumulation of particles in the filter. Next, an active regeneration of the filter is carried out, which, to intensify the ageing effect, can be conducted at an elevated temperature.
Ageing of selective catalytic reduction systems (SCR) is carried out over cycles with varying mass flow parameters, exhaust temperatures and quantities of AdBlue dosing. The temperature and the changes in the degree of SCR ammonia saturation lead to faster ageing.
Ageing procedures are characterised by cyclic measurements of reactor and filter efficiency during emission tests. Such tests can be conducted on an engine on the engine dyno equipped with an emissions analysis system, or with the TWC mounted on a vehicle in the exhaust emission laboratory. Emissions test can be conducted according to standardised procedures, for example, type approval procedures, or according to individual procedures created for a particular test plan.