不同发射深度下喷管燃气射流特性研究

为了探索发射水深对发动机水下点火流场特性的影响机制,该文数值研究了不同水深条件下发动机水下点火时实验喷管气水两相流场的非定常演化过程.研究结果表明:射流初期,高密度水介质对喷管出口高温燃气泡强剪切流具有阻滞作用,导致了流场中的压力以及射流产生的推力波动比较剧烈;随着射流的发展,流场中的压力及射流产生的推力波动趋于平缓,波动幅值与频率也随之降低;喷管推力随工作水深的增加而减小,并且推力随时间的变化规律与喷管进口燃气总压变化趋势一致.     

大型水轮发电机组推力轴承油膜特性分析

以渔子溪电站水轮机组为例,应用ARMD软件,通过改变镜板的转速、所受的轴向推力大小,得到推力轴承的油膜压力、油膜剪应力、油膜刚度和阻尼等的变化规律。结果表明推力轴承的油膜压力、油膜剪应力、油膜刚度和阻尼均随着轴向推力的增大而增大;随着镜板转速的增大而增大,在飞逸转速附近均急剧增大。     

基于桩间土拱效应的抗滑桩设计推力分析

抗滑桩设计推力的计算是滑坡治理工程的关键,决定了治理工程的成败。在分析抗滑桩桩间土拱效应形成机理的基础上,推导了考虑桩间土拱效应的抗滑桩设计推力计算公式,并与常规设桩处的剩余推力进行对比,分析了滑面倾角、桩截面尺寸和桩间距对抗滑桩设计推力的影响。结果表明:随着滑面倾角的增大,设计推力曲线先为水平线,而后呈对称的抛物线形,而且存在使设计推力为0和最大值的滑面倾角;抗滑桩的设计推力随着桩高度的增大以直线形式单调减小,随着桩宽度的增大以抛物线形式单调增加,随着桩间距的增大而单调减小。最后,通过工程实例验证了基于桩间土拱效应的抗滑桩设计推力计算方法的合理性。     

水下钻孔爆破水击波衰减规律及大坝动力响应特征分析

为研究青狮潭水库附近水下钻孔爆破施工对大坝的影响,采用多物理场仿真软件COMSOL模拟水下钻孔爆破作用过程,建立数值仿真计算模型,对水下钻孔爆破过程中水击波的传播衰减特征进行分析,同时分析水下钻孔爆破过程中地震波作用下水库大坝的动力响应特征。结果表明,在水下钻孔爆破产生的水击波和地震波协同作用下,水域中峰值振动速度随着爆心距增加而呈指数型衰减,水下钻孔爆破水击波的影响范围约200 m;大坝迎爆面底部的动应力响应和峰值应力最明显,振动速度达0.201 cm/s,峰值应力达0.013 MPa。研究结果可为评估水下钻孔爆破过程中水中建（构）筑物的稳定性提供数据支撑。     

自制晶体管汽车点火装置

汽车发动机是靠喷进气缸内的汽油通过火花塞点火燃烧推动活塞而做功的。因此,它的效率与点火线圈火花塞的点火能力直接有关。点火快,燃烧猛,推力大,效率就高。我处学习先进经验,用晶体管自制成点火装置,从去年8月开始先后在13辆汽车上试点使用,收到     

不同岩性下TBM滚刀破岩过程离散元分析

为了研究全断面岩石掘进机(TBM)的滚刀在不同岩性下的破岩机理,将考虑胶结尺寸的微观接触模型植入离散元软件,模拟了4种岩性下不同滚刀刃数的破岩过程,探究岩性、滚刀刃数对破岩效率的影响。模拟结果表明:不同滚刀刃数下的破岩过程可以分为3个阶段,即加载阶段、卸载阶段及残余跃进阶段;胶结破坏类型主要呈拉剪破坏与压剪破坏两种;滚刀破岩过程中受到的阻力可以用峰值法向推力表示,阻力大小取决于岩性,破岩阻力随着岩石单轴抗压强度的增大而增大;通过胶结破岩比能耗来评价破岩效率,对于坚硬岩,三滚刀破岩效率最高,对于强度较低的岩石,采用单滚刀破岩效率更高。     

导弹垂直发射出筒过程中通气空泡流研究

将通气空泡技术应用于导弹水下垂直发射出筒过程,通气空泡是高速航行体获得稳定空泡的一种重要技术。采用基于Mixture多相流模型的有限体积法求解RANS方程,结合动网格技术,对水下垂直发射导弹出筒过程的轴对称流场进行了数值模拟,研究导弹的流体动力特性和通气空泡的演化。结果表明通气空泡可减小导弹出筒过程中的阻力和改善导弹的流体动力载荷。     

摩阻对混凝土压缩试件受力状态影响分析

为研究混凝土压缩试验中钢压板与试件间摩阻对混凝土受压状态的影响,采用Ｎａｊａｒ损伤理论方法,基于ＣＤＰ模型建立了混凝土棱柱体和立方体单轴压缩的数值模型。分析了混凝土试块破坏特征和应力应变分布状态,绘制受压过程应力－应变曲线。计算结果表明,混凝土试件单轴压缩时弹性阶段受摩擦力影响相对较小,棱柱体峰值应力随着摩擦系数增大而减小,峰值应变则随之增大;立方体峰值应力和峰值应变均随着摩擦系数增大而增大。棱柱体和立方体的竖向应力和应变沿高度和宽度分布随着摩擦系数的增大越不均匀,当摩擦系数不大于0．5时,在棱柱体中间位置粘贴应变片所测得竖向应变与理想状态较为接近。采用数值模拟方法可有效分析混凝土压缩试件在摩阻作用下的受力状态,研究结论可为混凝土单轴压缩试验提供理论支撑。     

等幅循环加载历史后混凝土动态特性试验

对经历不同频率(0、0.5、2.0 Hz)循环加载历史后的混凝土进行了不同应变速率(10-5、10-4、10-3/s)下的单轴压缩试验,研究了循环加载历史下不同循环频率对混凝土峰值应力、峰值应变、弹性模量的影响.研究结果表明:混凝土的峰值应力随着应变速率的提高而增大,随着循环频率的提高先增大后减小;混凝土的峰值应变随着应变速率的提高而增大,随着循环频率的提高而减小;混凝土的弹性模量随着应变速率的提高总体变化规律不明显,随着循环频率的提高先增大后减小.     

TBM刀盘及滚刀施工机理试验研究

为进一步丰富并探索TBM刀盘及滚刀破岩与受力特征施工机理,结合TBM掘进工程实践进行了全面试验研究。结果表明:贯入度与刀盘推力及滚刀径向力间均呈二次抛物线关系,加大刀盘推力及滚刀径向力,增大贯入度有利于降低破岩能耗;刀盘振动基频与平均振幅较低,最大振幅相对较大,与滚刀破岩机理相一致。盘型滚刀破岩机理具有剪切破坏特征。双刃滚刀径向破岩峰值力远超刀盘总推力分配均值,峰值力较均值增大较多;正滚钝刀贯入度相同时,由是削破碎大块岩体而在能耗上更为经济,适当加大滚刀尖角有利于破岩增效及延长刀具寿命。试验研究成果全面、可靠,对刀盘及滚刀研发与优化技术改造具有重要意义。     

PARAMETRIC STUDY ON THE THRUST OF BUBBLY WATER RAMJET WITH A CONVERGING-DIVERGING NOZZLE

To predict the thrust of bubbly water ramjet with a converging-diverging nozzle, the physical processes occurring in the diffuser, mixing chamber and nozzle were analyzed. The mathematical models were constructed separately under the restrictions of certain assumptions. The bubbly nozzle flow was examined using a two-fluid model and accomplished by specifying the water velocity distribution in the nozzle. The numerical analysis of flow field in the nozzle shows that the Mach number at the throat is 1.009, near unity, and supersonic bubble flow appears behind the throat. There is greater thrust produced by bubbly water ramjet, compared with single-phase air ramjets. Subsequently, the influences of vessel velocity, air mass flow rate, inlet area A_m, area ratio (i.e., mixing chamber to inlet area A_m/A_i), and initial bubble radius on the thrust were emphatically investigated. Results indicate that the thrust increases with the increase of air mass flow rate, inlet area and the area ratio, and the decrease of initial bubble radius. However, the thrust weakly depends on the vessel velocity. These analytical and numerical results are useful for further investigation of bubbly water ramjet engine.     

水轮发电机组推力轴承油槽内流动及传热特性研究

为解决推力轴承瓦温过高的问题,采用数值模拟方法分析了某水轮发电机组推力轴承内循环冷却系统油槽内润滑油的流动及传热特性。结果表明,靠近镜板处油流速度大,远离镜板位置油流速度小;镜板内缘压力最低,沿着推力轴瓦径向向外压力逐渐增大;初始瓦温、初始油温一定时,随着水温降低,整体油温下降幅度并不大。根据研究结果,对推力轴承内循环冷却系统提出适当增大冷却器U型管直线段的长度、增大冷却器管径、提高冷却水的压力和流量、加大油冷却器铜管间距的改进建议。     

关于水轮机蜗壳结构不平衡水推力初步研究

为研究内水压力作用下水轮机蜗壳产生的不平衡水推力,采用裸壳和三维实际结构2种计算模型进行有限元计算分析。结果表明：进口附近有伸缩节无止推环的保压蜗壳在运行期座环要承担较大不平衡水推力的受力状态与施工期受力状态有较大差别;垫层蜗壳蜗向局部设垫层时,座环承担的不平衡水推力明显大于垫层全包时的不平衡水推力。应重视不平衡水推力的不利影响。     

黄河大柳树水利枢纽工程高面板堆石坝的渗流稳定性

高面板堆石坝具有很高的抗冲能力 ,即使在强震时面板全部失效或在正常运行时灌浆全部失效 ,渗流量都不足以冲动坝体堆石。工程实践及计算证明 ,堆石坝只有漏水问题 ,但坝体堆石不会被渗流冲失导致失事。     

混流式水轮机转轮倒置安装轴向水推力的计算

目前大中型水电站混流式水轮机轴向水推力大，尾水管中涡带所产生的压力脉动常引起机组振动。如水轮机转化倒置安装，将向下的轴向水推力改为向上，可以抵消机组转动部分的重量；如改变尾水管形状，可以消除涡带压力脉动，减小机组振动。以漫湾电站为例，经过计算说明正常安装与倒置安装轴向推力轴承负荷可大大减小。但倒置安装后其结构问题尚需进一步研究。     

Institutional Characteristics for International Cooperation in Water Resources

Agenda 21 calls for integrated management of water resources with catchments or sub-basins as the unit of management. There has been a steady evolution in the arrangements for cooperation in the man agement of international river basins over the last two centuries. Rather than aiming at a standardized set-up for all the international river basins, basin organizations can best be allowed to grow in phases according to the emerging needs of the respective basins. For healthy working of international basin organizations negotiations between the participating countries will be the principal thrust. Nevertheless, provision for arbitration for resolution of disputes will be desirable. The internation al non-governmental professional organizations have also steadily grown in different subject areas. They will be able to provide expert inputs into the workin g of the basin organizations. The river basin organizations and regional water m anagement bodies will need a global common platform for exchanging their experiences and for developing common global strategies. A World Water Council can provide such an umbrella set-up with its General Assembly comprising international basin entities, regional bodies, international professional associations and the UN agencies dealing with water .     

Modelling upstream fish passage in standard box culverts: Interplay between turbulence,fish kinematics,and energetics

Box culverts are common hydraulic structures along rivers and streams, in rural and urban water systems. The expertise in fish‐friendly culvert design is limited, sometimes leading to adverse impact on the catchment ecosystem or to uneconomical structures. Basic dimensional considerations highlight a number of key parameters relevant to any laboratory modelling of upstream fish passage, including the ratio of fish speed fluctuations to fluid velocity fluctuations, the ratios of fish dimensions to turbulent length scale, and the fish species. Alternately, the equation of conservation of momentum may be applied to an individual fish, yielding some deterministic estimate of instantaneous thrust and power expended during fish swimming, including the associated energy consumption. The rate of work required by the fish to deliver thrust is proportional to the cube of the local fluid velocity, and the model results demonstrate the key role of slow‐velocity regions in which fish will minimize their energy consumption when swimming upstream.     

Hydrodynamic performance of distributed pump-jet propulsion system for underwater vehicle

A type of distributed pump-jet propulsion system （DPJP） is developed with two or four specially designed pump-jet pods located around the axisymmetric underwater vehicle body symmetrically. The flow field is numerically simulated by solving the RANS equations with the finite volume method. The computational method is validated by comparing the calculated hull resistances of the SUBOFF AFF-3 model and the open water performance of a ducted propeller with experimental data. The hydrodynamic performances of the DPJP with different axial or radial positions and numbers of pump-jet pods are obtained to analyze the interactions between the hull and the pump-jet pods. It is shown in the calculated results that the decrease of the distance between the pods and the hull leads to an increase both in the efficiency of the pods and the thrust deduction factor due to the effect of the stern wake. And, a negative thrust deduction factor can be obtained by locating the DPJP at the parallel middle body near the aftbody of the vehicle to improve the hydrodynamic performance of the DPJP. Besides, the increase of the number of pods will cause a remarkable decrease of the total propulsive efficiency of the DPJP with the pods mounted on the stern planes, while a small decline of the total propulsive efficiency of the DPJP is observed with the pods mounted on the parallel middle body.     

地下PCCP管道的止推设计

供水工程的地下管道与水利水电工程的其他压力管道工作条件虽然大致相同，但其止推设计同以往主要使用镇墩相比，却显得非常经济，又极为简便，很值得我们借鉴，结合万家寨引黄工程PCCP管的运用，介绍了美国供水工程协会（AWWA）颁发的《混凝土压力管道手册》（《M9手册》）中止推设计的部分内容，有许多独特之处，不仅为地下管道的止推设计提供了理论基础和具体计算方法，有些方面还可供其他压力管道的止推设计参考。     

基于在线数据的抽水蓄能机组推力油膜综合厚度研究

随着我国建设的抽水蓄能电站不断增加,且抽水蓄能机组经常面临工况的急剧转换,从机械设计上抽水蓄能电机的推力轴承采用中心支撑和双向高速运行,因此推力轴承部件成为抽水蓄能机组运行过程中重点监测对象,如何对其进行安全监控与管理就变得尤为重要。推力轴承处频繁出现的故障现象就是推力瓦存在着刮瓦现象,这种现象如果恶化就会导致推力瓦烧瓦事故,造成这种现象的原因很可能是机组在低速旋转时,由于推力油膜形成条件变差所致。为了更好地实现对推力轴承油膜厚度的实时监测,消除电站运行安全隐患,充分发挥其经济效益,本文提出一种基于在线数据的抽水蓄能机组推力油膜综合厚度研究,并利用抽水蓄能电站的推力轴承状态监测实际运行数据,对其进行系统分析,为抽水蓄能电站优化运行的监控和管理提供了重要的参考依据,保障机组的安全平稳运行。