Optimization of Performance of Oxygen Storage Component (OSC) for NO Reduction in Three Way Catalysts to Achieve BS VI Emission Norms

Current restrictions on environmental pollution worldwide has created the need for new methodologies and technology development which should not only ensure ultra-low emission level from different categories of engine but should also use less fuel resulting in lower carbon dioxide (CO₂) emissions. The state-of-art technology to achieve ultra-low emissions placed after engine in exhaust line is a ‘catalytic converter’. Catalytic converter is an after treatment device which typically oxidizes or reduces the toxic pollutants emitted by any engine to carbon dioxide (CO₂), nitrogen (N₂) and water (H₂O). Catalytic converters used in Gasoline / CNG operated vehicles contains oxygen storage component as a key component for supplying oxygen in rich mode of operation and the oxygen concentration release rate is function of gas concentration and air to fuel ratio (A/F) or lambda (λ). Conventionally, the vehicles (two wheelers) operated using mechanical method such as carburetor, a source for injection fuel in the engine and the lambda range produced from this method is of wide window (0.95-1.06). The catalyst located downstream the engine needs an optimum amount of oxygen storage component required to supply oxygen in rich mode of operation and excess oxygen concentration released during these period results in to a significant drop in oxygen storage capacity (OSC). The drop in OSC corresponds to drop in NO_x conversion efficiency.

Moving from BS IV to BS VI, the NO_x conversion requirement is over 90% including deterioration factor limit and thus requires a tight control in terms of lambda as well as oxygen storage component optimization. The lambda control can be achieved by switching from mechanical method of injection to electronic method i.e. electronic fuel injection (EFI) and subsequently the need for oxygen storage component optimization is required.

Illustrative case studies has been presented in this paper, to demonstrate the role of oxygen storage component in NO_x conversion.