增大脚阀空行程的再生制动策略研究与测试

基于开关量脚阀的并联制动能量回收方案无法根据制动踏板开度调整回收扭矩,在提高制动能量回收率的同时无法兼顾制动性能,故提出基于模拟量脚阀的并联制动能量回收方案。首先通过分析传统车辆制动力曲线特性增大脚阀空行程,完成脚阀开发;其次根据ECE法规计算能量回收扭矩边界,完成样车改制;最后针对样车开展回收效果评价及相关制动性能试验,测得该回收策略下的制动能量回收效果有显著提升,且制动效能满足法规要求,主观评价在驾驶员可接受范围内。表明该回收方案具有一定的工程应用价值。

基于AMESim的模拟电空阀建模及仿真

介绍了模拟电空阀的结构和工作原理;运用AMESim软件对CRH2动车组制动系统里的模拟电空阀进行建模,并进行了仿真,对仿真结果进行了分析并且与实验数据进行了对比。结果表明:该模型正确可靠,对该阀特性研究奠定了基础。

“中原之星”号动力分散型电动车组空电联合制动

以“中原之星”电动车组空电联合制动为例,系统介绍了动力分散型电动车组一种空电联合制动模式,并对其试验以及使用情况做了介绍,阐述了它的优越性。试验表明,制动系统满足设计要求,安全可靠,且能自动优先并最大限度地利用再生制动能力。

CFD gas–liquid simulation of oriented valve tray

Computational fluid dynamics(CFD) has recently emerged as an effective tool for the investigation of the hydraulic parameters and efficiency of tray towers.The computation domain was established for two types of oriented valves within a tray and meshed into two parts with different grid types and sizes.The volume fraction correlation concerning inter-phase momentum transfer source was fitted based on experimental data,and built in UDF for simulation.The flow pattern of oriented valve tray under different operating conditions was simulated under Eulerian-Eulerian framework with realizable k-ε model.The predicted liquid height from CFD simulation was in good agreement with the results of pressure drop and volume fraction correlations.Meanwhile,the velocity distribution and volume fraction of the two phases were demonstrated and analyzed,which are useful in design and analysis of the column trays.

Numerical Simulation on a Throttle Governing System with Hydraulic Butterfly Valves in a Marine Environment

Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.

Numerical Study on Flow-induced Noise for a Steam Stop-valve Using Large Eddy Simulation

The noise induced by the fluctuant saturated steam flow under 250 °C in a stop-valve was numerically studied.The simulation was carried out using computational fluid dynamics（CFD） and ACTRAN.The acoustic field was investigated with Lighthill＇s acoustic analogy based on the properties of the flow field obtained using a large-eddy simulation that employs the LES-WALE dynamic model as the sub-grid-scale model.Firstly,the validation of mesh was well conducted,illustrating that two million elements were sufficient in this situation.Secondly,the treatment of the steam was deliberated,and conclusions indicate that when predicting the flow-induced noise of the stop-valve,the steam can be treated as incompressible gas at a low inlet velocity.Thirdly,the flow-induced noises under different inlet velocities were compared.The findings reveal it has remarkable influence on the flow-induced noises.Lastly,whether or not the heat preservation of the wall has influence on the noise was taken into account.The results show that heat preservation of the wall had little influence.

Numerical Simulation and Analysis of Gas Flow Field in Serrated Valve Column

A three-dimensional computational fluid dynamics （CFD） model for gas flow through a serrated valve tray was presented. The flow field, as well as the dry-pressure drop of the valve under the full-opening condition was simulated based on the proposed model by using FLUENT 6.0 software. Compared with the values of dry-pressure dro.p in different turbulent models, the.simulated.results using RNG κ-ε model are in reasonable agreement with experimental data, indicating that RNG κ-ε model is suitable in simulating gas flow through the serrated valve tray. Then the CFD model combining RNG κ-ε model was used to study the three-dimensional gas flow through the considered serrated valve tray. The simulated results showed that various eddies existed on the serrated valve tray, and both the eddy and the non-eddy areas were nearly equal. The existence of addendum can decrease the eddy area caused by gas passing through the lateral outlet slots. The size of eddies can be reduced by optimizing the distance between valves.

Experimental and simulated studies on hydraulic buffering valve for ZF-4WG308 power-shift transmission

The structure and working principle of a hydraulic buffering valve for a power-shift transmission ZF-4WG308 were studied comprehensively, and a model of the hydraulic buffering valve was developed with AMESim. A bench test was conducted on a buffering valve for transmissions(ZF-4WG308) and the test results agree well with the simulated results. Further more, the influences of the key parameters of the valve on the buffering performance were also studied in details.

基于FW366/FW367的电阀模拟器设计

FW366/FW367是浙大中控ECS-100组态系统中两款数字式I/O卡件,能够非常方便实现大规模电阀控制。但在生产实际中由于没有专用的电阀调试工具,使组态软件调试工作量较大、故障诊断不直观。为了解决这一生产实际问题,提出了基于FW366/FW367的电阀模拟器设计。硬件部分选用ARM STM32F103C8T6为逻辑芯片,一方面接收FW367卡件输出的开阀或关阀命令,另一方面驱动28BYJ-48型步进电机执行开阀、关阀操作,并把阀门操作信号通过继电器输出到FW366输入卡件,实现硬件设计;软件部分利用ARM芯片的I/O中断功能,快速响应开阀、关阀命令,并结合阀位行程开关位置,判断是否需要执行开阀或关阀动作。实验结果表明,电阀模拟器能够替代在线运行的真实阀门,模拟执行开阀、关阀命令及阀门操作信号反馈等功能。

Improved Water Network Macroscopic Model Utilising Auto-Control Adjusting Valve by PLS

In order to overcome the low precision and weak applicability problems of the current municipal water network state simulation model, the water network structure is studied. Since the telemetry system has been applied increasingly in the water network, and in order to reflect the network operational condition more accurately, a new water network macroscopic model is developed by taking the auto-control adjusting valve opening state into consideration. Then for highly correlated or collinear independent variables in the model, the partial least squares (PLS) regression method provides a model solution which can distinguish between the system information and the noisy data. Finally, a hypothetical water network is introduced for validating the model. The simulation results show that the relative error is less than 5.2%, indicating that the model is efficient and feasible, and has better generalization performance.

Research on the Response Characteristics of Solenoid Valve of the Air-jet Loom by Simulation

Solenoid valve is one of the executive parts of weft insertion control system. According to the response characteristics of the solenoid valve, an improved design becomes a necessity. Firstly, the numerical model was established after analyzing the solenoid valve during its start-up and shut-down. Comparing the simulation data with the practical data, it is verified that the numerical simulation model has a high feasibility. Secondly, excitation voltage and spring pre-compression were adjusted respectively, and the response rules after adjusting were investigated. The research of the study shows: the response time tends to be inverse proportional to the excitation voltage during start-up, and it becomes a constant value with the increase of the excitation voltage; the response time is proportional to the spring pre-compression when the solenoid valve starts up, it is inverse proportional to spring pre-compression when the solenoid valve shuts down. And the total response time is a constant value with the increase of the spring pre-compression. Therefore, the value of the excitation voltage and the spring pre-compression should be selected when the curve is becoming flatten. The results of the research can provide the reference to the further development of the solenoid valve.

Influence of filler morphology on percolation threshold of isotropical conductive adhesives (ICA)

Different aspect ratio silver nano-structured materials including nanocubes,nanorods and nanowires were prepared by micro-waved assisted glycol reduction method.Different characterization methods including SEM and XRD were processed on these nanomaterials.Isotropical conductive adhesives(ICA) were developed by using these Ag nanomaterials as conductive fillers.It was found that the conductivity and thermal conductivity percolation threshold of the ICA depended on the morphologies of the fillers,lower percolation threshold could be obtained by using higher aspect ratio filler.A modified percolation threshold theory was put forward to explain and simulate the experiment results,the simulated results could match the experiment results very well.