Pulsair-a Method for Exhaust System Induction of Secondary Air for Emission Control

The Pulsair concept utilizes inherent exhaust system pressure pulsations to induce secondary air into reciprocating engine exhaust ports for oxidation of unburned hydrocarbons and carbon monoxide. High-speed check valves are actuated by subambient exhaust pressures which arise from reflected exhaust “blowdown” pressure waves. For multicylinder engines, a single check valve set can be used effectively to supply air to an entire exhaust manifold.

Experiments with V-8 engines and simple acoustic wave theory have been used to define system fundamentals and design techniques for obtaining high induced airflow rates at specified engine speeds. Procedures are outlined for adapting the concept to L-4, L-6, and V-6 engines.

The Pulsair system does not affect net engine power and is potentially less complex than typical air pump systems. Sufficient air can be induced to meet the expected secondary air requirements for many exhaust aftertreatment systems; however, some modifications to conventional exhaust systems may be necessary. For example, Pulsair rates as high as 60% of engine airflow have been demonstrated by modifying the exhaust crossover of a V-8 engine.