Research on the Control Strategy of Variable Nozzle Turbocharger for Natural Gas Engine

A variable nozzle turbocharger (VNT) was applied to a 2.2-liter L4 natural gas engine,and a VNT control system was designed to operate it.Based on VNT matching test results,a VNT control strategy was studied,in which VNT adjustment is carried out through pre-calibrated VNT handling rod position,combined with a closed-loop target boost pressure feedback using proportional-integral-derivative(PID) algorithm.Experimental results showed that the VNT control system presented in this thesis can lead to optimized ...     

Investigation of the optimum differential gear ratio for real driving cycles by experiment design and genetic algorithm

Experiment statistical method and genetic algorithms based optimization method are used to obtain the optimum differential gear ratio for heavy truck that provides best fuel consumption when changing the working condition that affects its torque and speed range. The aim of the study is to obtain the optimum differential gear ratio with fast and accurate optimization calculation without affecting drivability characteristics of the vehicle according to certain driving cycles that represent the new working conditions of the truck. The study is carried on a mining dump truck YT3621 with 9 forward shift manual transmission. Two loading conditions,no load and 40 t,and four on road real driving cycles have been discussed. The truck powertrain is modeled using GT-drive,and DOE-post processing tool of the GT-suite is used for DOE analysis and genetic algorithm optimization.     

Optimal tracking control for automatic transmission shift process

In order to improve the shift quality, a linear quadratic optimal tracking control algorithm for automatic transmission shift process is proposed. The dynamic equations of the shift process are derived using a Lagrange method. And a powertrain model is built in the Matlab/Simulink and verified by the measurements. Considering the shift jerk and friction loss during the shift process, the tracking trajectories of the turbine speed and output shaft speed are defined. Furthermore, the linear quadratic optimal tracking control performance index is proposed. Based on the Pontryagin's minimum principle, the optimal control law of the shift process is presented. Finally, the simulation study of the 1-2 upshift process under different load conditions is carried out with the powertrain model. The simulation results demonstrate that the shift jerk and friction loss can be significantly reduced by applying the proposed optimal tracking control method.     

Optimizing Spray and Combustion in Diesel Engine by Multidimensional Numerical Simulation

The calculation of spray and combustion in diesel engines is described by using the softwares FIRE and BOOST. The application of the resulting computational method to the simulation of fuel spray and breakup, mixture formation and combustion in a heavy duty diesel is presented. According to detailed insight into the governing processes provided by the simulation results, various aspects of the dependence of the spray propagation and combustion on the chamber geometry and spray angle are discussed. Then, global cylinderaveraged pressure traces are extracted from the space and time resolved field quantities and compared to incylinder pressure measurements. Finally, an optimized configuration of the chamber geometry and spray angle with a new injection rate of higher injection pressure is proposed.     

基于对置活塞发动机的液压混合动力系统仿真研究

基于对置活塞二冲程(OP2S)发动机独特的结构特点,新型液压混合动力系统将OP2S发动机与液压泵集成在一起,取消了传统液压混合动力车辆的动力分流机构,驱动过程中根据不同的行驶工况同时或分时输出机械能或液压能来驱动车辆,在液压混合动力车辆上具有独特的应用优势。运用AMESim仿真软件搭建系统仿真模型进行了能量管理策略的仿真分析。研究结果表明:在一个NEDC循环工况内,新型混合动力车辆可以实现驾驶员对车速的控制要求,并在车辆减速制动时回收制动能用于车辆的再次启动加速,为同时兼顾车辆制动能回收与燃油经济性的优化目标,最优切换车速点为25 km/h。     

液压驱动式泵-喷嘴系统特性研究

对一种电子控制液压驱动式泵-喷嘴供油系统进行了建模与仿真,在AMEsim环境下使用机械、液压和控制部件的标准元件搭建仿真模型,用一维集总参数法进行仿真计算.利用试验测出的柱塞升程和柱塞腔内压力以及循环供油量检验模型的准确性和精度,在此基础上通过对仿真模型的优化,计算了不同控制参数下的喷油规律,对该喷油器的改进设计及其与发动机的合理匹配和供油系统控制策略的研究具有一定的指导意义.     

某型柴油机高压共轨喷油器结构改进仿真分析

针对某型柴油机共轨喷油器改进设计的需求,建立了喷油器的数值仿真模型,研究了喷油器针阀质量、控制腔容积及供油道长径比对喷油器特性的影响.研究表明在保证针阀结构强度的情况下,针阀质量应该更小;控制腔容积在满足针阀升程要求等条件下也应更小;在确定长径比的条件下,合理安排喷油器的尺寸结构,适度增加供油管的长度和直径可以降低喷油器内部的压力波动.研究为该型喷油器的改进设计提供了技术支撑.     

用"缸平移"法提高柴油机模型实时性的方法研究

为了解决柴油机ECU硬件在环仿真时,柴油机模型的精确度和实时性的矛盾,提出了基于充排法的柴油机＂缸平移＂建模方法.在Matlab/Simulink中建立基于充排法的柴油机模型,假设发动机全部气缸以相同方式工作,通过＂缸平移＂法获得＂缸平移＂模型.分别将充排法的发动机模型和＂缸平移＂模型下载到dSPACE Autobox中进行实时仿真,试验表明应用＂缸平移＂方法建立的柴油机模型可以使系统的仿真速度提高三倍.     

通过进气道优化改进柴油机的性能

利用仿真软件FIRE建立了6V150柴油机进气道的三维仿真模型，在用稳流吹风实验验证了仿真的结果后，分析了进气道内部的三维流场，然后采用缩小气门杆后部气流停滞区的方法提高了进气道的流量，而且该方法对气缸盖布置及进气门结构的影响也很小。最后，在仿真软件BOOST建立的整机仿真模型中，对柴油机的性能进行了分析。分析结果显示，在保证空燃比不变的前提下，在柴油机进气量增加的同时也加大其燃油量，可以提高柴油机的有效功率和指示平均有效压力(IMEP)，改进了柴油机的动力性。     

氧传感器参考电平自适应空燃比闭环控制方法研究

为了解决开关式氧传感器空燃比闭环控制点的漂移问题，建立了开关式氧传感器闭环控制的数学模型，并分析了氧传感器信号参考电平对空燃比闭环控制的影响，据此，提出了氧传感器参考电平自适应空燃比闭环控制方法，在发动机上试验了氧传感器参考电平对空燃比的影响规律，并进行了氧传感器参考电平的优化试验，结果表明，氧传感器参考电平自适应控制方法可以有效避免空燃比闭控制点随发动机工况变化的漂移问题，有效地降低了汽油机的排放。