Study On The Hybrid Turbocharging System In A Vehicle Engine

Turbocharging system is a necessary accessory of vehicle engine for energy-saving and environmental protection.To solve the matching problem of steady and transient operating conditions between the turbochargers and the engines, many turbocharging technologies are emerging. These techniques include waste-gated turbocharging, variable geometry turbocharging, sequential turbocharging and hybrid turbocharging, etc. In recent years, hybrid turbocharging is a favored new technology in several developed countries, which can effectively solve the inherent shortcomings of traditional turbocharging. The hybrid turbocharging system consists of a turbocharger with a high speed electronic motor integrated into the turbocharger shaft, and an energy storage device. The project of hybrid turbocharging system has very important technical and economic research value.According to matching requirements of light vehicle diesel engine, the analysis model of exhaust gas energy is obtained through qualitative analysis of exhaust gas energy in turbocharged diesel engine. The control model of hybrid turbocharging system in steady engine condition is achieved on the basis of the analysis model. In this control model high speed motor can adjust the exhaust gas energy to improve the performance of engine by motor driving or braking. Then the overall layout of the system is examined, which can lay the foundation for simulation and design.Simulation is an effective means of engine design, therefore the numerical model of turbocharged engine is necessary to establish. The model of wastegated turbocharged diesel engine is set up by the boundary conditions and the thermodynamic models of various engine components, then experiments validate the rationality of numerical model.The numerical model of hybrid turbocharged diesel engine is obtained by modifying the turbocharging system of wastegated turbocharged diesel engine. Then the numerical model is used to simulate the steady condition of engine. The adjusting strategy for exhaust gas energy of hybrid turbocharged diesel engine can be obtained through simulation. The further research is carried out on parameter optimization of the turbocharging system and adjustment of the advanced exhaust angle. Analysis of energy flow is of great significance to properly distribute the energy share and improve the performance of the turbocharging system. Mapping with the GRNN neural network manifests that this method is appropriate to mapping control of hybrid turbocharging system in the steady condition of engine.Transient condition is an important area of research on turbocharged engine, so this dissertation establishes the transient model of hybrid turbocharging system, and analyzes the transient performance for hybrid turbocharging system about various parameters by simulation, then simulates the transient performance with fuzzy PID control. The simulation results confirm that the measures about the adjustment of parameters and fuzzy PID control can improve the transient characteristics of hybrid turbocharging system.The next research process is to design the component structure of hybrid turbocharging system when the main structural parameters have been determined by simulation. The system design is divided into the part of rotor, bearings, seals, cooling jacket and electrical motor, etc., and ultimately a virtual prototype has been designed. The calculation of the rotor vibration in critical speed can be performed by finite element analysis when the detailed parameters of the structure are determined. The calculation results of critical vibration can confirm that the structural design is reasonable, and will provide useful data for later test and engine matching.In order to obtain the performance of prototype, the newly developed hybrid turbocharging system is experimented in a pneumatic test bed. These experiments include the shaft vibration test, the compressor equal flow rate test, mechanical efficiency test, acceleration test, thermal load test and smoke emission test. Preliminary experiments confirm that the new design of the hybrid turbocharging system is feasible, and the experiments provide a practical basis for the future promotion of the project.