This paper describes an alternative catalyst aging process using a hot gas test stand for thermal aging. The solution presented is characterized by a burner technology that is combined with a combustion enhancement, which allows stoichiometric and rich operating conditions to simulate engine exhaust gases. The resulting efficiency was increased and the operation limits were broadened, compared to combustion engines that are typically used for catalyst aging. The primary modification that enabled this achievement was the recirculation of exhaust gas downstream from catalyst back to the burner.
The burner allows the running simplified dynamic durability cycles, which are the standard bench cycle that is defined by the legislation as alternative aging procedure and the fuel shut-off simulation cycle ZDAKW. The hot gas test stand approach has been compared to the conventional engine test bench method. Comparisons of catalysts aged on the hot gas bench and an engine dynamometer showed similar results within the tolerance band.
An urban driving cycle was also run on the test bench with a diesel exhaust system that included a particulate filter working in regeneration mode. The drive cycle simulation on the test bench was able to provide an exhaust gas temperature profile within the catalyst, which represented the same thermal load as in the vehicle. The aging progress was monitored by a dynamic light-off measurement procedure.
The capability to produce heavily aged three-way catalysts on the test bench down to the OBD limit was also investigated. The profile of catalyst damage and the resulting effect on oxygen storage capacity and emissions, could be varied by adjusting the bench aging parameters.