Improving Transient Diesel Performance with E-Supercharging and Multiple-Input Multiple-Output Controls

Torque transients are challenging for turbocharged diesel engines. Engine torque response is limited by the lag in air flow, restricting the rate at which fuel can be delivered to avoid high engine-out soot emissions. Electrified forced induction systems (EFIS) offer a solution to address this challenge. In this study, an electrified supercharger (e-supercharger) is utilized in addition to the stock turbocharger on a 4.5-L 4-cylinder diesel engine to create a two-stage boosting system. Two control strategies were studied for e-supercharger control during engine transients, a model-based single-input single-output (SISO) controller and a model-based robust multiple-input multiple-output (MIMO) controller. Constant speed load acceptance (CSLA) experiments and emulated drive-cycles were performed to evaluate the performance of each control method. In-cylinder pressure measurements were acquired and apparent heat release calculations were performed and analyzed to better understand the transient engine response. The e-supercharged two-stage boosted engine demonstrated significant improvements over the baseline engine when using both control approaches. The rate of transient power generation was improved by as much as 59.4% resulting in reduced engine speed droop and decreased engine speed recovery time. Transient engine-out soot emissions were also reduced. Although both control approaches improved transient response relative to the baseline engine, the MIMO controller showed the greatest potential for future improvements.