Research On Modeling Technique For Performance Simulation And Optimization Of Two-Stage Turbocharged Diesel Engine Under Transient Operations

This research was based on a developmental project of a two-stage sequenciallyturbocharged diesel engine. A modeling method was proposed which can accurately track andpredict engine performances during a transient load step while in the same time satisfingmultiply controls restrains. This solved the key problems of utilizing GT-power to simulateengine performances under a transient load step.The rules and procedure of turbocharger selection and matching were summarized, anevaluation system was also established. The application, matching and controls of varioustwo-stage turbocharging systems were studied.According to the actual structure sizes and the dyno test data of a diesel engine, theGT-power simulation models of both steady state and transient process were established, withdetailed description to the important submodules and parameter settings. The steady stateperformance simulation model was correlated with the dyno measurement data. The preditionerror was shown within3%for engine performance parameters, while the error onturbocharger operating parameters was within5%.Based on the calibrated steady state performance simulation model in GT-power, atransient process simulation model was then established. The simulation procedure for atwo-stage sequentially turbocharged diesel engine was established which meets therequirements of multiply restrains control. The EGR control module which can realize thereal-time control of the opening of the EGR valve was exploited for the transient load step.The required AFR was controlled real-time by regulating the fuel injection quantity cycle bycycle. The control method of in-cylinder combustion parameters was also proposed under thetransient load step, and the calculation procedures fuel injection quantity and combustionparameters were developed. The sub-models developed in this research were implementedinto the GT-Power transient simulation model. Simulation results indicate that all theboundary condition restrains were well maintained and the model was proven to be highlyaccurate and reliable.Implemented all the above, the transient load step performance of the diesel engine waspredicted and optimized for different VGT control strategies. The outcomes of this researchcan be utilized as a numerical pre-calibration tool and the results provide guidances andoptimization directions for the calibration of the diesel engine for transient processes.