石门拱坝坝基渗流分析

通过对坝基渗流观测资料的分析，揭示了两种不同防渗设计之扬压力、渗流量的变化规律，指出加强排水是降低渗透压力，解决扬压值陡升的有效途径。     

管袋堤坝波浪作用下波浪压力的数值模拟研究

波浪作用是影响管袋筑坝的最主要外部荷载,关系到管袋结构的安全与稳定。为了解管袋堤坝在波浪作用下的波浪压力,基于流体力学计算软件FLUENT建立数值水槽模型,通过设定不同的边界条件,采用源造波法模拟不同波高、周期、水深、坡率下波浪与管袋坝面的相互作用,计算管袋受力和波陡、坡率之间的关系,并拟合相应关系曲线得到管袋坝的受力和波陡、坡率之间的函数关系式。结果表明,该方法的结果与物理试验过程中获得的规律相符,具有一定的实用性。     

滑动挡板式越浪发电装置结构受力研究

研究在正向规则波入射下不同斜坡高度及不同水深情况时越浪式波浪发电装置的受力规律。在波浪水槽中进行模型试验;使用FLOW-3D软件进行数值模拟,通过对不同波高、不同波浪周期、极端工况进行数值模拟,得出不同波浪要素下斜坡的受力规律。通过对试验结果和模拟结果的对比分析得出:越浪斜坡在波浪入射过程中受力有先后顺序;斜坡在波浪作用下的周期受力数值在一定范围内波动;斜坡在波浪作用下波浪要素条件不变时,斜坡受力与斜坡高度、试验水深有关,呈线性关系。试验结果对滑动挡板式越浪发电装置结构的设计提供依据。     

增压6缸柴油机排气压力波变化规律的试验研究

针对某增压6缸柴油机进行了不同负荷特性下的排气压力波测量,分析了不同负荷特性下排气压力波的变化规律.试验结果表明:对于增压6缸柴油机,当配气相位相同时,在不同的负荷特性下,排气压力波平均值的变化规律是相同的,排气压力波平均值随着扭矩的增加而增大;不同转速下相同扭矩测试点的排气压力波平均值进行横向对比时以及在外特性上,排气压力波平均值随着转速的增加而增高.在不同的负荷特性下,排气压力波强度的变化规律是相同的,排气压力波强度随着扭矩的增加而增高;不同转速下相同扭矩测试点的排气压力渡强度进行横向对比时,排气压力波强度随着转速的增加而增高,但是在外特性上,随着转速的增加,排气压力波强度先增加后减小.     

垂直管内水蒸气与水接触时凝结所诱导的压力波特性实验研究

实验研究了水蒸气直接接触凝结诱导的压力波特性。实验是在质量流速0~150 kg/(m~2·s),压力0.2~0.4MPa的饱和蒸汽条件下,用直径为8 mm的喷嘴,将蒸汽喷入到存有凝结水的垂直管的流动模型中进行的,管内水温和压力范围分别为30~70℃和0.11~0.15 MPa。实验通过检测壁面压力信号来捕获压力波动信号。系统分析了低蒸汽质量流速时,压力波随时间的高幅值低频率变化规律。获得了压力波幅值随蒸汽质量流速和过冷水温度的定量变化关系。揭示了压力波动信号的概率密度、函数分布、偏度系数和峭度系数的变化规律。     

增压柴油机排气压力波的对比试验研究

为了对某增压六缸发动机的性能做进一步的改进,对其涡轮入口处和排气支管出口处的排气压力波变化规律进行了试验研究.试验结果表明,涡轮入口处和排气支管出口处的排气压力波平均值变化规律相同:在不同的负荷特性下,排气压力波平均值都随着扭矩的增大而增大;不同转速下相同扭矩测试点的排气压力波平均值,都随着转速的增大而增大.在不同的负荷特性下,涡轮入口处和排气支管出口处的排气压力波强度变化规律不相同,涡轮入口的压力排气波强度要大于排气支管出口处的排气压力波强度.     

根据喷油压力波形特征判断燃油喷射装置故障部位

通过ZB-2型柴油机燃油喷射系统故障诊断仪(即柴油机燃油压力波检测仪)对DF4型机车柴油机燃油压力波的检测,在对大量检测事例进行跟踪、统计、分析的基础上,揭示出燃油压力波的检测波形与该缸喷射装置质量状态的对应关系,并据此确定故障部位,为故障处理提供参考.     

可控脉冲增压系统对D6114柴油机性能影响研究

可控脉冲增压系统可以实现气缸相对排气容积的调节,具有兼顾发动机高低转速工况的优势。本文针对D6114ZLQB型柴油机,建立了该发动机可控脉冲增压系统GT-POWER仿真模型,通过不同排气容积条件下发动机性能试验校核了仿真模型。计算研究了不同转速下可控脉冲增压排气系统排气压力波和进气压力变化规律,探讨了脉冲增压系统和准定压增压系统在不同转速下的适应情况。通过仿真计算研究了可控脉冲增压系统对柴油机性能的影响,确定了可变脉冲增压系统的切换边界。     

飞秒激光加工微孔工艺技术研究

主要对飞秒激光在平板上加工微孔时的影响因素进行阐述、研究,通过试验验证了焦点位置微量变化对加工孔径的影响;同时验证了不同压力压缩气体对飞秒激光加工时的影响,选出最优辅助气体气吹压力;研究了微孔锥度影响因素,总结出焦点位置、扫描时间与微孔锥度的关系;最后将研究出的因素关系运用到批量打孔试验中,验证了该工艺技术的加工稳定性。     

气波引射装置真空度实验研究

为了研究转速及高、中压喷嘴间偏转距离对气波引射装置性能的影响,分析两个参数与低压端口真空度间的变化规律。设定高压进气压力为1.5 MPa,低压、中压和高压端口宽度分别为63,37和44 mm,高压与低压端口间固壁段宽度为14 mm。实验研究了当转速分别为2 500,3 000,3 500以及4 000 r/min,偏转距离分别为10,18和26 mm时,中压出口压力与低压端口真空度之间的关系。结果表明:在恒定转速条件下,低压端口处真空度与中压出口压力呈负相关关系;当中压出口压力恒定时,随着设备转速的增加,真空度先增大后减小。在中压压力一定的情况下,当转速较低时真空度随偏转距离增大而减小,当转速较高时真空度随着偏转距离的增大呈现先减小后增大的趋势,偏转距离对真空度具有显著影响,且存在最优值,最优值与设备转速相关。此外,真空度与设备引射率近似呈正比例关系,即引射率和增压比呈负相关关系。     

Reflection and refraction of plane wave at the interface between elastic and thermoelastic media with three-phase-lag model

The problem of reflection and refraction phenomenon due to longitudinal and transverse waves incident obliquely at a plane interface between uniform elastic solid half-space and thermoelastic solid with three-phase-lag model half-space has been studied. In thermoelastic solid medium, potential functions are introduced to represent two longitudinal waves and one transverse wave. The amplitude ratios of various reflected and refracted waves to that of incident wave are derived. These amplitude ratios are further used to find the expressions of energy ratios of various reflected and refracted waves to that of incident wave. The graphical representation is given for these energy ratios for different directions of propagation. The law of conservation of energy at the interface is verified.     

水位骤变条件下河流崩岸模型试验及机理研究

为研究水位骤变条件下河流崩岸的形成机理,结合现场调研及室内模型试验,分析了水位骤变条件下河流崩岸过程及孔隙水压力的变化规律。结果表明,在水位上升过程中,水土结合部位易产生裂缝,并不断拓展形成贯穿性裂缝,影响岸坡结构完整性,同时局部区域产生坍塌现象形成临空面,为后续坡体大规模坍塌提供条件;水位骤降后,由于水体惯性牵引,坡脚掏空,失去支撑,坡体发生整体下滑(由试验前的45°坍塌成31°),产生条崩现象;在库区水位骤降时,坡体内孔隙水压的消散速度低于坡前水位骤降速度,土体内外形成较大的水压力梯度(孔隙水压力),进而诱发大规模崩岸。揭示的河流崩岸内在机制,对于库岸安全管理具有较大的参考价值与实际意义。     

Delay or removal of aneurysm formation in the Anaconda wave energy extraction device

Any distensible tube inflated beyond a critical pressure will experience aneurysm formation. The Anaconda wave energy device consists of a pressurised flooded tube, which when excited with an external incident wave of appropriate frequency, for the set inflation pressure, permits generation of internal bulge waves that provide the mechanism for more efficient wave energy extraction. The distensible tube must be designed to have structural integrity and to facilitate the bulge wave matching the incident wave. The bulge wave speed is governed by internal fluid density and tube distensibility. The latter is readily shown to be dependent upon volume–pressure gradient within the tube. With application of a displacement–pressure based finite element formulation the likelihood of aneurysm and its delay or avoidance can be investigated. The strain energy functions selected for use with the finite element analysis are the Yeoh and third-order Ogden model as these formulations have been previously shown by the authors to satisfy the required Maxwell equal area rule and provide the most consistent predictions when using different mixes of experimental stress-strain data. After summarising a representative set of known wave energy extraction devices, to appreciate how different Anaconda is, the paper looks at the extent and mode of deployment of an outer inextensible reinforcement to provide bulge waves of appropriate speed whilst also overcoming the onset of aneurysms within the Anaconda tube.     

碳烟捕集泡沫陶瓷吸声性能的试验研究

分析碳烟捕集泡沫陶瓷材料的吸声原理,获得泡沫陶瓷吸声系数与泡沫陶瓷的孔径、孔隙率、试样厚度和入射波的频率有关。利用驻波管法测量两组不同参数的泡沫陶瓷的吸声系数,试验结果进一步验证了泡沫陶瓷的结构参数和入射频率对吸声系数和消声性能的影响。     

Numerical simulation and theoretical analysis of premixed low-velocity filtration combustion

This paper investigates combustion wave characteristics of lean premixtures in a porous medium burner. Heat recuperation originated by the porous medium is examined by an one-dimensional numerical model. Attention is focused on the influences of solid properties, heat loss, equivalence ratio, etc., on the combustion wave speed and the maximum combustion temperature attained in the wave. Based on the flame sheet assumption a relationship between the combustion wave speed and the maximum combustion temperature is given. Then an approach from the laminar premixed flame theory is applied and the entire flame zone is divided into a pre-heating region and a reaction region, and treated separately. In this way, the second relationship between the two parameters is deduced. Thus a closed analytical solution for the combustion wave speed and the maximum combustion temperature is obtained. Over a wide range of working conditions, the numerical predictions and theoretical results show qualitative agreements with experimental data available from the literature. The results reveal that the mechanism of superadiabatic combustion is attributed to the overlapping of the thermal wave and combustion wave under certain conditions.     

Analysis of coupled-waves structure and propagation characteristics in hydrogen-assisted kerosene-air two-phase rotating detonation wave

In order to investigate the structure and propagation characteristics of hydrogen-assisted kerosene (liquid phase)-air rotating detonation, a modified solver based on OpenFOAM^? was proposed and utilized to simulate detonation in the mixture of hydrogen, liquid kerosene and air. The obtained results show that evaporation waves exist in the discrete liquid mist detonation, and the coupled-waves structure formed by the evaporation wave (EW) and the incident shock wave (ISW) propagates upstream. By analyzing the overall and instantaneous propagation characteristics, it is found that the propagation speed of the detonation wave increases with the increase of the equivalence ratio at the fuel rich state. Increasing the droplet size will cause the evaporation wave to be further downstream relative to the ISW, resulting in lower evaporating pressure. The effect of EW on ISW is accomplished by the blast wave traveling upstream which is generated by droplet reaction, while EW is influenced by the ISW by modulating the droplet enthalpy and the pressure attenuation following ISW. Part of the droplet reaction energy is held in the gap between the EW and ISW, consequently the gap acts as an energy storage piston, regulating the ISW and EW propagation speeds. The combustion of droplets with smaller sizes imposes more positive feedback on their evaporation, and increasing the total temperature of the premixed gas promotes the interaction between the EW and the ISW, resulting in a more steady propagating overall structure.     

人工降雨条件下坡面流试验分析

采用5个固定坡度的试验水槽和人工降雨系统模拟了不同坡度和雨强下的坡面薄层水流,分析其水动力学特性随坡度和雨强的变化规律,为坡面侵蚀理论提供了试验依据.研究结果表明,人工降雨条件下坡面薄层水流各水力学特性与坡度和雨强呈较好的函数关系.     

Horizontal pressure gradient and Soret effects on the onset of thermosolutal porous convection

The intricacies of a constant horizontal pressure gradient on the onset of Soret-driven thermosolutal porous convection have been investigated. The resulting generalized eigenvalue problem is solved numerically using the Galerkin method and also the condition for the onset is obtained in a closed-form using a single-term Galerkin method with trigonometric trial function. The results obtained from both methods are found to be in good agreement. The effect of increasing horizontal pressure gradient, Lewis number, Soret parameter, and the Vadasz number is to hasten, while the increase in the solute Darcy–Rayleigh number is to delay the onset of oscillatory convection. The presence of the horizontal pressure gradient is found to decrease the threshold value of solute Darcy–Rayleigh number beyond which the instability sets in as oscillatory. Moreover, the horizontal pressure gradient imparts a conflicting behavior on the critical wave number and critical frequency of oscillations. The numerical results attained under the limiting cases are shown to be in excellent agreement with the published ones.     

Reflection of plane wave in a micropolar thermoelastic solid half-space with diffusion

In this article, the governing equations of micropolar thermoelasticity with diffusion are formulated in the context of Lord–Shulman theory of generalized thermoelasticity. The plane wave solutions of these equations indicate the existence of six plane waves, namely, coupled longitudinal displacement (CLD) wave, coupled thermal wave, coupled mass diffusion wave, coupled transverse microrotational wave, coupled transverse displacement wave, and longidudinal microrotational wave. Reflection of CLD wave from a stress-free thermally insulated/isothermal surface is considered. The appropriate potentials of incident and reflected waves satisfy the required boundary conditions at a stress-free thermally insulated/isothermal surface to obtain the reflection coe?cients of various reflected waves for an incident CLD wave and to obtain an extension of Snell’s law. The expressions for energy ratios of various reflected waves are also obtained. A particular material aluminum–epoxy composite is chosen to compute the values of reflection coe?cients and energy ratios of reflected waves. The effects of diffusion and thermal parameters are observed on the reflection coe?cients and energy ratios.