高压共轨喷油器电磁阀液力特性研究

高压共轨系统喷油器电磁阀是高压共轨系统的关键技术,为进一步了解其液力特性,本研究基于Hydsim软件平台,针对2进油量孔的大流量电磁阀喷油器结构建立仿真模型,通过试验校验了模型的准确性,并通过模拟仿真方法,分析了控制量孔的结构对大流量喷油器液力特性的影响。

高压共轨喷油系统液力特性的仿真研究

利用AVL公司的Hydsim软件建立了高压共轨喷油系统液力过程的仿真模型,对高压共轨喷油系统液力过程进行了仿真计算。通过研究喷油器结构参数对系统液力特性的影响,总结了其对高压共轨喷油系统燃油喷射特性的影响。提出了高压共轨喷油系统的改进方向。

三缸单作用柱塞泵动力端结构参数对液力特性的影响研究

三缸单作用往复泵是广泛使用的流体输送设备,其动力端结构参数对泵的液力特性影响较大。在柱塞泵动力端运动及受力分析的基础之上,分析了动力端连杆比结构参数对压力参数的影响,以及对流量脉动特性的影响,为三缸单作用往复泵的优化设计提供借鉴参考。

GDI喷油器结构参数对液力响应特性的影响

利用AMESim软件建立了GDI喷油器机械液压系统动力学仿真模型,研究了不同燃油温度、燃油压力、喷孔直径以及喷孔个数下单因素对液力响应特性的影响。结果表明:燃油压力、喷孔结构对GDI喷油器喷油速率影响很大,喷孔直径与喷孔个数对针阀关闭时刻影响较大,而燃油压力对针阀开闭均有影响。基于响应曲面分析方法研究了单因素交互作用对喷油器液力响应的影响规律。结果表明:喷孔直径与燃油压力、喷孔直径与喷孔个数、喷孔个数与燃油压力间交互作用对最大喷油量影响显著,为GDI喷油器优化设计提供了理论参考。

应用项目中的液力变矩器选型

液力变矩器液力特性对车辆性能有重要的影响。本文描述了在应用项目中液力变矩器液力特性选型的过程中,除了车辆动力性和燃油经济性之外的主要影响因素,比如橡皮带效应、高原因素、低温因素和爬行能力。此外,扭转减震特性的选择也做了简要的介绍。

浅论风力发电液力机械传动装置的特点及设计

随着科学技术的不断发展和进步,风力发电成为当前主要的发电方式之一,在人们的生产生活中发挥着越来越重要的作用,而风力发电液力机械装置是风力发电的重要装置之一。该文对风力发电液力机械传动装置的特性及设计进行研究,以期优化风力发电液力机械传动装置的设计,进而提高风力发电的可控性和高效性。

基于AMESIM的电液VVA系统仿真研究

以某汽油机可变气门驱动系统(VVA)为研究对象,利用AMESim软件建立仿真模型,研究VVA系统的液力特性,并在此基础上研究液压油温度和泄漏对VVA系统性能的影响。分析结果表明:通过控制电磁阀的开关时刻,可以实现气门升程和相位连续可变;气门关闭速度随温度降低而减小;液力系统泄漏量增加,会造成气门升程降低。

Analysis and Experimental Identification of Torsional Dynamic Characteristics of Hydrodynamic Torque Converter

The subsection linear torsional model of hydrodynamic torque converter was established and further simplified. According to the identification theory, the frequency characteristic was achieved with the Matlab/ Ident toolbox. Then parametric model was established by adopting the subsection linearization method, and the damp value was estimated. The curve and function of damp changing with speed ratio was also established by fitting. In order to validate the identification results, the experimental output was compared with the output of the model in which torque was chosen as input signal and speed as output signal in Matlab/Ident toolbox. It was shown that model output is in good agreement with experimental output.

Thermogravimetric characteristics and different kinetic models for medical waste composition containing polyvinyl chloride-transfusion tube

Thermogravimetric study of medical transfusion tube （MTT） waste containing polyvinyl chloride （PVC） was carried out using the thermogravimetric analyser （TGA） with N2, at different heating rates of 5, 10, 20, 30, 50 ℃/min. The purpose is to obtain pyrolysis characteristics and kinetic parameters of medical waste. The experimental results indicate that the pyrolysis behavior of the MTT sample is in agreement with its main ingredient of PVC, appearing two stair stepping stages. The influence of the additives in MTT on pyrolysis behavior was also revealed, which could improve MTT pyrolysis at lower temperature in the first stage, and cause obvious unsmoothness and asymmetry of the second DTG peak. Four n-order kinetic models of Coats-Redfern, Ozawa, Kissinger and Freeman-carroll were used to get the kinetic parameters. Furthermore, a novel ＂two-step four-reaction model＂ was established to simulate the whole continuous process. The different methods and the kinetic parameters thus obtained were discussed and compared with each other in literatures. The reasons of deviation among kinetic values were tried to be elucidated. The new established model could more satisfactorily describe the pyrolysis process of MTT, being more mechanistic and conveniently serving for the engineering.

Experimental study on pressure fluctuation characteristics of slug flow in horizontal curved tubes

In order to study the pressure characteristics of slug flow in horizontal curved tubes,two kinds of curved tubes with central angle 45° and 90° respectively are studied,of which are with 0. 5m circumference and 26 mm inner diameter are used. When the superficial liquid velocity or the superficial gas velocity is constant,the pressure fluctuations and the probability distribution of the average velocity of slug flow are clear for all of the five experimental conditions. The results of experiment show that the pressure characteristics of slug flow in curved tubes have periodic fluctuations. With the rise of central angle,the period of pressure fluctuation is more obvious. The system pressure of the slug flow increases with the increasing of superficial liquid/gas velocity. Meanwhile,the probability distribution of pressure signal shows regularity,such as unimodal,bimodal or multimodal.

Alkaline extraction characteristics of steelmaking slag batch in NH_4Cl solution under environmental pressure

In order to obtain better carbonation effect, extraction behavior of slag batch is necessary to study. Relevant parameters like selective extraction yield were originally discussed. The relationship between selective extraction yield and conversion ratio was systemically focused on. The results show that alkaline earth metal conversion ratio is changed with leaching time and NH4CI concentration by first order exponential, and the maximum conversion for calcium keeps about 68% at 120 min in 0.4 mol/L NH4C1 solution, while leaching temperature and particle size have a linear effect on conversion ratio. Selective extraction yield of calcium is more than 93%, and the value of Mg is less than 5%. Apparent layer bands of silicon and calcium appear in the surface area through morphology detection of slag after leaching, and the case for 38-75 μm slag batch is more obvious than 75 150 μm slag and slag with larger particle size when leaching in 0.4 mol/L NH4Cl solution for 90 rain at 60 ℃.

Characteristics of vibration liquefaction of saturated medium sandy soil with silt

In order to understand and master the dynamic characteristics of sandy soil with different silt contents, the authors carried out many indoor dynamic triaxial tests for five groups of sandy with silt which took from Panjin and Xiamen. Under the conditions of consolidation pressure of 100 kPa, 200 kPa, 300 kPa, stationary vibration frequency H=1 and cyclic loading, the authors found that the effective cohesion increases and the effective internal friction angle decreases with the increase of the silt contents. During the liquefied scope, the cementation and the strength have been increased with the increase of the silt contents.

Fluid structure interaction for circulation valve of hydraulic shock absorber

Based on the working principle and the damping characteristic of hydraulic shock absorber, a fluid structure interaction method was presented, which was used to analyze the microcosmic and high-frequency processing mechanism of fluid structure interaction between circulation valve and liquid of hydraulic shock absorber. The fluid mesh distortion was controlled by the CEL language, and the fluid struc^tre interaction mathematical model was established. The finite element model was established by ANSYS CFX software and was analyzed by dynamic mesh technique. The local sensitive computational area was meshed by prismatic grid, which could reduce the negative volume problem during the simulation. The circulation valve and liquid of hydraulic shock absorber were simulated and analyzed under the condition of sinusoidal inlet velocity loads. Flow characteristic and dynamics characteristic were obtained. The pressure distribution and the displacement of circulation value were obtained, and the acceleration curve of circulation valve was simulated and analyzed. The conformity of the final simulation results with the experimental datum indicates that this method is accurate and reliable to analyze the dynamics characteristic between circulation valve and liquid of hydraulic shock absorber, which can provide a theoretical foundation for optimizing hydraulic shock absorber in the future.

Hydrodynamics and Mass Transfer of Oily Micro-emulsions in An External Loop Airlift Reactor

This study reports an experimental investigation on hydrodynamics and mass transfer characteristics in a 15.6x10-3 m3 external loop airlift reactor for oil-in-water micro-emulsions with oil to water volume ratio （φ） rang- ing from 3% to 7% （by volume）. For comparative purposes, experiments were also carried out with water. Increase in φ of micro-emulsion systems results in an increment in the gas holdup and a decrease in the volumetric gas-liquid oxygen transfer coefficient and liquid circulation velocity, attributed to the escalation in the viscosity of mi- cro-emulsions. The gas holdup and volumetric mass transfer coefficient for micro-emulsion systems are signifi- cantly higher than that of water system. Two correlations are developed to predict the gas holdup and oxygen trans- fer coefficient

Analysis of the nonlinear dynamic characteristics of two-phase flow based on an improved matrix pencil method

Gas–liquid two-phase flow is complex and has uncertainty in phase interfaces, which make the two-phase flow look very complicated. Even though the flow behavior(e.g. coalescence, crushing and separation) of single bubble or bubble groups in the liquid phase looks random, combining some established characteristics and methodologies can find regularities among the randomness. In order to excavate the nonlinear dynamic characteristics of gas–liquid two-phase flow, the authors developed an improved matrix pencil(IMP) method to analyze the pressure difference signals of the two-phase flow. This paper elucidates the influence of signal length on MP calculation results and the anti-noise-interference ability of the MP method. An IMP algorithm was applied to the fluctuation signals of gas–liquid two-phase flow to extract the mode frequency and damping ratio, which were combined with the component energy index(CEI) entropy to identify the different flow patterns. It is also found that frequency, damping ratio, CEI entropy and stability diagram together not only identify flow patterns, but also provide a new way to examine and understand the evolution mechanism of physical dynamics embedded in flow patterns. Combining these characteristics and methods, the evolution of the nonlinear dynamic physical behavior of gas bubbles is revealed.

Effects of atomization parameters of dust removal nozzles on the de-dusting results for different dust sources

In order to obtain appropriate spray pressure and enhance the spraying and dust removal efficiency, various factors including the dust characteristics, nozzle spraying angle, effective spraying range, water consumption and droplet size are taken into account. The dust characteristics from different mines and atomization parameters of different pressure nozzles were measured. It was found that the internal pressure of coal cutters and roadheaders should be kept at 2 MPa, which could ensure large droplet size, large spraying angle and low water consumption and hence realizing a large-area covering and capture for large particle dusts. However, the external spray pressure should be kept at 4 MPa for smaller droplet size and longer effective spraying range, leading to effective dust removal in the operator zone. The spray pressure of support moving, drawing opening, and stage loader on a fully mechanized caving face and stage loader on a fully mechanized driving face should be kept at 8 MPa, under which the nozzles have long effective spraying range, high water flow and small droplet size for the rapid capture of instantaneous, high-concentration and small size dust groups. From the applications on the caving and driving faces in the coal mines, it is indicated that the optimization of spray pressure in different spraying positions could effectively enhance dust removal efficiency. Selecting appropriate nozzles according to the dust characteristics at different positions is also favorable for dust removal efficiency. With the selected nozzles under optimal pressures, the removal rates of both total dust and respirable dust could reach over70%, showing a significant de-dusting effect.

Blood flow analysis in tapered stenosed arteries with pseudoplastic characteristics

In this paper, the blood flow through a tapered artery with a stenosis by considering axially non-symmetric but radially symmetric mild stenosis on blood flow characteristics is analyzed, assuming the flow is steady and blood is treated as Williamson fluid. Per- turbation solutions have been evaluated for velocity, resistance impedance, wall shear stress and shearing stress at the stenosis throat. The graphical results of different type of tapered arteries （i.e. converging tapering, diverging tapering, non-tapered artery） have been examined for different parameters of interest.

Effects of Interfaces on Dynamics in Micro-Fluidic Devices：Slip-Boundaries' Impact on Rotation Characteristics of Polar Liquid Film Motors

A new approach for exploring effects of interfaces on polar liquids is presented. Their impact on the polar liquid film motor(PLFM) – a novel micro-fluidic device – is studied. We account for the interface's impact by modeling slip boundary effects on the PLFM's electro-hydro-dynamical rotations. Our analytical results show as k = l_s/R increases(with ls denoting the slip length resulting from the interface's impact on the film's properties, k >-1 and R denoting the film's radius):(a) PLFMs subsequently exhibit rotation characteristics under "negative-", "no-", "partial-" and"perfect-" slip boundary conditions;(b) The maximum value of the linear velocity of the steady rotating film increases linearly and its location approaches the film's border;(c) The decay of the angular velocities' dependency on the distance from the center of the film slows down, resulting in a macroscopic flow near the boundary. With our calculated rotation speed distributions consistent with the existing experimental ones, research aiming at fitting computed to measured distributions promises identifying the factors affecting ls, e.g., solid-fluid potential interactions and surface roughness.The consistency also is advantageous for optimizing PLFM's applications as micro-washers, centrifuges, mixers in the lab-on-a-chip.

Investigation on structure and dynamic property of liquid Pd-Cu-Ni-P alloys using ab initio molecular dynamics simulation

Based on the short-range order,it is found that the abundance of the P-centered P-transition-metal clusters are the common feature among the liquid Pd-Cu-Ni-P alloys,and hence this feature alone could not uncover the underlying mechanisms of the variation of glass forming ability among the liquid alloys.For the so called similar elements such as Cu and Ni,their behaviors are significantly different when interacting with Pd or P atoms.Cu has weak bonding with both Pd and P while Ni has very strong bonding with P but nearly no bonding with Pd.The different bonding characters thus underlie the phenomenon that in the best glass formers the ratio of the two similar elements often deviates from 1:1.Only if the parameters of chemical short-range order of Cu and Ni around P become closest to each other the best glass forming ability is reached.It is also illustrated that the calculated dynamic properties are very helpful to locate the composition of the best glass former.