| Nissan is seizing the initiative
in clean diesel for the US. The OEM is developing catalyst technologies
to meet California’s ultra-stringent SULEV emissions standards.
Several US states have already adopted California’s legislation
and more are set to follow. Any OEM in compliance with California’s
limits will have greater access to the emerging US diesel market.
Unlike some competitors’ urea-based systems, Nissan’s new
catalyst uses stored hydrocarbons (HC) to reduce NOx into harmless nitrogen.
Nissan said: “This HC-NOx trap catalyst will be able to achieve
cleaner diesel emissions that meet SULEV standards.”
Cutting NOx emissions is the main challenge: SULEV limits are 70 per cent
lower than those of Tier II BIN 5, itself more stringent than proposals
for Euro VI. Nissan’s strategy combines the catalyst, cleaner combustion
and advanced engine control.
Nissan’s HC-NOx catalyst, located between the oxidation catalyst
and DPF, stores NOx and HC under lean conditions. Under rich conditions,
the HC converts NOx into nitrogen gas, purging the catalyst in the process.
Lower temperature, pre-mixed combustion minimises NOx and particle formation
at source. However, pre-mixed, or near-homogenous combustion takes complex
management to keep fuel economy and avoid misfires.
The catalyst could also help future Nissan-Renault vehicles meet Euro
VI. Nissan said: “This technology is applicable to the global market,
including Europe.” |
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