Stratified Exhaust Gas Recirculation in a S. I. Engine 860318
Stratified Exhaust Gas Recirculation (SEGR) can enable a spark ignition engine to tolerate more exhaust gas recirculation than when the EGR is premised in the intake manifold. Experiments were conducted on a VW aircoaled engine modified to incorporate exhaust gas transfer ports in the cylinder walls. A unique arrangement of interconnected ports allowed the exhaust blow-down pressure from one cylinder to push EGR into a high swirl velocity during the intake stroke of an opposite cylinder. In-cylinder swirl of the EGR was the stratification mechanism. Evidence of effective stratification is that the engine could tolerate 262 SEGR via the ports but could tolerate only 10% EGR via the intake manifold.
The benefit of SEGR is improvement in part-load fuel economy. Efficient part-load operation may be achieved by controlling the amount of SEGR, rather than by throttling the intake. Thus pumping loss is decreased. Gains in fuel economy were measured at 10% in the experimental engine.