On the Use of VVT Strategy for the Maximum Volumetric Efficiency in Turbocharged Diesel Engines

This paper presents a variable valve lifting methodology for turbocharged diesel engines. For this purpose, the diesel engine is modeled based on a modified mean-value engine modeling. An optimal control strategy is used for maximum volumetric efficiency acquirement. Using camless valve train strategy makes better fuel economy and improved air intake characteristics throughout the engine operating map. The system is capable of continuously, independently and virtually controlling all standard parameters of variable valve motion. This permits optimization of valve events for any operating condition without compromise. The optimized intake valve profile is determined, to have the best volumetric efficiency and proper operation for each running condition based on the existing model make use of numerical techniques. The model used in this paper is validated using simulation results of references. The model treats the cylinder and the manifolds as thermodynamic control volumes by using the filling and emptying method, solving energy and mass conservation equations with sub models for intake manifold, variable valve timing, cylinder breathing dynamics and turbocharger including turbine and compressor. This model is a crank angle based dynamic nonlinear model of a four-cylinder turbocharged (TC) diesel engine, which captures the interactions among the VVT actuation, the turbocharger dynamics and the cylinder-to-cylinder breathing characteristics. The model have been implemented in Matlab/Simulink and tested. This work shows the results obtained for air management control in a turbocharged diesel engine, specifically, manifold pressure and air mass flow. These variables are often required to achieve better power performance and lower emissions.