Investigation on transient switching strategy of diesel engine sequential turbocharging system

For reducing soot emission in transient state, the optimal transient switching strategy of the diesel engine sequential turbocharging (STC) system was investigated. In the transient switching experiments, the diesel engine performance parameters and soot emission were measured when the delay time between the air valve open and the gas valve open is 0 s, 0.5 s, 1.5 s and 2.5 s, respectively, during the controlled turbocharger switch-in process. The experiment results showed that the engine speed waved evidently and the soot emission deteriorated when the air valve and gas valve opened simultaneously; However, the longer the switching delay time was, the more the engine speed waved, the more the main turbocharger pressure dropped and the more the transient soot emission increased. The optimal transient switching strategy is obtained based on the analysis of the engine performance parameters and soot emission at switching condition.