Semi-empirical modeling of volumetric efficiency in engines equipped with variable valve timing system

Volumetric efficiency and air charge estimation is one of the most demanding tasks in control of today's internal combustion engines.Specifically,using three-way catalytic converter involves strict control of the air/fuel ratio around the stoichiometric point and hence requires an accurate model for air charge estimation.However,high degrees of complexity and nonlinearity of the gas flow in the internal combustion engine make air charge estimation a challenging task.This is more obvious in engines with variable valve timing systems in which gas flow is more complex and depends on more functional variables.This results in models that are either quite empirical(such as look-up tables),not having interpretability and extrapolation capability,or physically based models which are not appropriate for onboard applications.Solving these problems,a novel semi-empirical model was proposed in this work which only needed engine speed,load,and valves timings for volumetric efficiency prediction.The accuracy and generalizability of the model is shown by its test on numerical and experimental data from three distinct engines.Normalized test errors are 0.0316,0.0152 and 0.24 for the three engines,respectively.Also the performance and complexity of the model were compared with neural networks as typical black box models.While the complexity of the model is less than half of the complexity of neural networks,and its computational cost is approximately 0.12 of that of neural networks and its prediction capability in the considered case studies is usually more.These results show the superiority of the proposed model over conventional black box models such as neural networks in terms of accuracy,generalizability and computational cost.

DYNAMIC MODEL AND SIMULATION OF A NOVEL ELECTRO-HYDRAULIC FULLY VARIABLE VALVE SYSTEM FOR FOUR-STROKE AUTOMOTIVE ENGINES

In modem four-stroke engine technology, variable valve timing and lift control offers potential benefits for making a high-performance engine. A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced. The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented. Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control. Consequently the engine performance on different loads and speeds will be significantly increased. The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.

MODELING, VALIDATION AND OPTIMAL DESIGN OF THE CLAMPING FORCE CONTROL VALVE USED IN CONTINUOUSLY VARIABLE TRANSMISSION

Associated dynamic performance of the clamping force control valve used in continuously variable transmission （CVT） is optimized. Firstly, the structure and working principle of the valve are analyzed, and then a dynamic model is set up by means of mechanism analysis. For the purpose of checking the validity of the modeling method, a prototype workpiece of the valve is manufactured for comparison test, and its simulation result follows the experimental result quite well. An associated performance index is founded considering the response time, overshoot and saving energy, and five structural parameters are selected to adjust for deriving the optimal associated performance index. The optimization problem is solved by the genetic algorithm （GA） with necessary constraints. Finally, the properties of the optimized valve are compared with those of the prototype workpiece, and the results prove that the dynamic performance indexes of the optimized valve are much better than those of the prototype workpiece.

发动机可变气门正时阀的微分先行的PID控制算法

为优化发动机可变气门正时(VVT)阀原有的控制,提出了微分先行的比例积分微分(PID)控制算法。分析了VVT阀的工作原理与机械结构,测定了VVT阀的关键参数。建立了数学模型与Simulink仿真模型,借助于Matlab/Simulink平台。用实机平台与仿真平台,验证所提出的控制算法。结果表明:在VVT阀控制中,面对目标期望值的波动,与传统PID算法相比,在阶跃测试时,微分先行PID算法超调量降低0.8%,静态误差降低0.15%;在追踪测试时,其超调量降低1%,静态误差降低0.15%。因此,本算法完成了对VVT阀的优化控制。

The Energy Balance of the Electro-Hydraulic Linear Actuation System

The variable gas exchange valve actuation systems have been developed in order to improve the efficiency of the combustion process. The electro-hydraulic valve actuation （EHVA） systems have good power to weight ratio, high maximum force and good controllability. The disadvantages are limited frequency bandwidth and energy recovery. Each component of the EHVA system has certain energy consumption, which is characteristic to the component. In this study the power consumptions of the components are investigated by means of the simulation. The investigated components are a hydraulic pump, a hydraulic accumulator, a control valve, and hydraulic lines connecting the components. The pressure losses caused by the oil flow are most significant in the control valves, 50-60% of the total energy consumption. If the stored kinetic energy of the actuator and moving oil masses could be reused, the energy consumption could be up to 25% better.

Simulation and experimental study of electro-pneumatic valve used in air-powered engine

To evaluate the performance of newly designed electro-pneumatic valves (EPVs) for the air-powered engine (APE) and study laws of parameters affecting them, a simulation model was established based on the thermodynamics and mechanics theories. Experiments were set up to determine the instantaneous effective orifice area of solenoid valve by the constant volume discharge method. The simulation model was also validated by comparing the measured displacement curve with the simulated displacement curve of the valve in the pressure of 0.16 and 0.49 MPa. Simulation and experimental results showed that maximum working frequency of the designed EPV could reach 30 Hz corresponding to 2000 r/min of engine rotating speed. Based on simulation results, impacts of temperature and pressure of control air on delay time, full opening/closing time and seating velocity of EPV were analyzed. The simulation model could also act as EPV simulation prototype in designing the air exchange control system of APE.

Design of a hybrid magnetomotive force electromechanical valve actuator

We propose a novel axis-symmetric modified hybrid permanent magnet(PM)/electromagnet(EM) magnetomotive force actuator for a variable valve timing camless engine. The design provides a large magnetic force with low energy consumption, low coil inductance, PM demagnetization isolation, and improved transient response. Simulation and experimental results confirm forces of about 200 N(in the presence of coil current) at the equilibrium position and 500 N(in the absence of coil current) at the armature seat. We compared our proposed design with a double solenoid valve actuator(DSVA). The finite element method(FEM) designs of the DSVA and our proposed valve actuator were validated by experiments performed on manufactured prototypes.

A new method to measure the concentration of argon-xenon gas mixture

RGAs are widely used in molec Background RGAs are widely used in molecular component examination,impurity analysis,leak detection and test of vacuum system performance.However,RGAs have different sensitivities to different gases,and the sensitivities can change quickly and depend on so many parameters,which make its ability severely limited.Methods In thiswork we established a newpractical method to precisely measure noble gas ratio of argon-xenon gasmixture.Gaseous argon and xenon were controlled,respectively,by two mass flow controller(MFC).A variable leak valve(VLV)was used to introduce the gas mixture sample into the RGA measurement chamber.Gas mixtures with xenon concentration from 200ppm to 20000ppm(by mass)were introduced and tested by RGA.Results The time stability of RGA-measurement system was optimized to 2.1%.A good linearity of MFC-RGA response was achieved,verifying the reliability of RGA in measuring noble gas mixture with component concentration down to several hundred ppm level.Conclusions Since the approach we used in our experiment is gas-species independent,we believe that it can be popularized to other gas species when properly applied.