Abstract
KEYWORDS:
NOx sensor, NOx adsorber, lambda control, air-fuel ratio, storage capacity
ABSTRACT:
NOx catalyst has been developed to solve one of the most important and difficult problems of lean burn engines: as the leaner is the combustion, much NOx is emitted.
The nitrogen oxide emissions (especially N2O) have an increasing contribution to acid rain, smog, greenhouse effect and to the depletion of the protective ozone layer. NOx also produce several negative and serious health effects through its aspiration in the respiratory system.
While engine HC and CO emission can be further controlled by catalytic after treatment, achieving stringent NOx emissions standards under lean (oxidizing) conditions founded in Gasoline Direct Injection GDI, or Diesel engines is a very difficult task.
The aim of this paper is to develop a more deeply insight in the control and measurement aspects involving the NOx level sensing and reduction for lean burn, GDI or Diesel engines. Basically, the control strategies for lean mixtures are not limited to Diesel or GDI engines, but fundamentally include SI engines which have a NOx catalyzer and conventional air fuel mixtures with 60% air excess, in fact 60% fuel deficiency. Comparatively, modern Diesel engines can cover a range from 18.1 to 100 in air/fuel ratio.