| Nowadays, with the rise in oil prices and increasing concern of environmental problem, energy-saving and emission-reduction has became an important policy for many countries. The oil consumed by the vehicle accounts for a great proportion in the oil consumption of the world. An engine management with three-way catalyst and closed-loop structures is indispensable. To meet the requirement for emission, power and fuel efficiency, the air/fuel must be controlled accurately, which is based on the precise estimation of inducted air mass.First of all, in this paper, we do further study on the computational model of the charge efficiency with turbocharger and VVT system simultaneously. In order to improve the computational accuracy of the charge efficiency, this paper divide the residual gas fraction to the gas mass that goes through both valves during the valve overlap(either backflow of burned gas or scavenging of burned gas) and the residual gas mass staying in the cylinder from on cycle to the next one,which could divide the gas mass always staying in the cylinder and the gas mass that goes to the inlet manifold then comes back to the cylinder. The mass and pressure of the residual gas fraction can be calculated by computing the mass of every fraction.Secondly, use ASCET to design the entire computational model of the charge efficiency. Then the simulation model of a 1.3T dual VVT engine was established by using GT-Power software and the accuracy and reliability of the model was verified. Use the GT-Power model to simulate real engine to analyze the impact of different target boost pressure and the target VVT phase on engine performance, and to get the optimal VVT phase.Finally, compare and analyze the computational model of the charge efficiency through the GT-Power model simulation and engine bench test respectively. The simulation results and experimental data show that the computational of the charge efficiency has been improved with the new computational model. |
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