共查询到20条相似文献，搜索用时 46 毫秒
1.
为优化径向透平动叶片的结构型式,有效提高透平工作效率,本文基于Ansys-Fluent软件构建振荡水柱波能发电装置径向冲击式透平的三维瞬态全流域数值模型,通过改变透平动叶片吸力面型式,研究了正弦往复入射气流条件下动叶片厚度差异对透平扭矩、压强等参量的影响及其对透平输入系数、扭矩系数和周期平均效率等非定常性能评价参数的影响。在保证压力面型式不变情况下,研究了5种动叶片厚度分别为7 mm、13 mm、16 mm、19 mm和22 mm的透平在呼气、吸气阶段的非定常工作性能,结果表明：不同动叶片厚度的透平的非定常工作性能存在较大差异,动叶片厚度为13 mm的透平非定常工作性能最优,最大峰值效率可达47.7%。 相似文献
2.
为揭示多级压气机中上下游叶轮对中间叶片叠加气动影响特性,阐述不同叠加干涉情况下下游叶轮进气角度变化,采用数值方法模拟了一级轴流和一级离心组成的组合压气机非定常流场。详细讨论了上游动叶尾迹和下游动叶势流对中间导流叶栅段气流非定常流动的异频和同频叠加干涉特性,依据计算结果,直观地展示了静叶通道中两种干涉间相互激励和抑制作用的位置和时间,与数学公式的推导结果相互印证。研究结果表明:当上下游动叶对中间静叶段异频干涉时,干涉的激励、抑制区域的轴向位置随时间发生变化;当上下游动叶对中间静叶干涉频率相同时,干涉的相互激励、抑制区域的轴向位置不随时间发生变化,但干涉的激励、抑制区域的轴向位置受时序位置影响。另外,上游动叶尾迹与下游离心叶轮势流的不同叠加情况,决定着下游离心叶轮进口相对气流角的大小及波动幅值。 相似文献
3.
为了得到桶基础承受风、浪动荷载的承载性能,结合我国东海地质条件,统计中国东海2010—2020年浅、深海风速和最大海浪数据,通过计算得到风浪荷载并制成ABAQUS软件幅值曲线施加到海上风电吸力桶基础上,分析了吸力桶基础在动荷载作用下的承载特性。结果表明：吸力桶基础受风、浪荷载影响明显,桶基础迎力面受到风浪动荷载产生拉拔现象。在浅海区,桶基础在风浪荷载作用下桶身自上而下变形不协调,风浪荷载最大的10月份桶基础迎力面最大位移超出了规范0.02D的限制,基础失稳;桶基础背力面受压变形较小。在深海区,桶基础在风浪荷载作用下桶身自上而下变形相对协调,施加风浪荷载后桶体迎力面最大位移为14.9 mm,整体上迎力面位移比背力面位移大4 mm,桶体处于稳定状态。相较浅海区的吸力桶单桶结构,深海区吸力桶结构由于尺寸增加,桶体的稳定性得到提高,说明吸力桶结构的尺寸对稳定性起决定性作用。 相似文献
4.
《海洋技术学报》2021,40(4)
为获取高升力系数和升阻比的舵翼外形特征参数,本文以某型水下机器人舵翼为研究对象,将其表征量简化为展弦比、梢根比、前缘后掠角、攻角和剖面翼型5个设计参数。采用计算流体力学方法(CFD)模拟了流速为2 kn时,平板翼型厚度为6 mm的常见平面形状舵翼在不同来流下的流场情况,得到舵翼平面形状参数与其水动力性能和铰链力矩之间的变化规律和相对灵敏度,并对基于径向基函数模型(RBF)的优化结果进行分析,随后对比了不同剖面翼型对舵翼性能的影响。研究结果表明:攻角为6°左右时,舵翼可获得最佳水动力性能;剖面翼型对舵翼的水动力性能有较大影响,NACA00xx系列翼型可以显著提升舵翼的升阻比,并且翼型厚度越小,性能越佳;舵翼面积一定的条件下,后掠形舵翼具有优良的水动力性能,但铰链力矩较大;攻角较小时,梯形舵翼表现出较好的水动力性能,铰链力矩很小;攻角较大时,切尖三角形舵翼水动力性能与后掠舵翼基本持平,铰链力矩适中。 相似文献
5.
冲击式空气透平是振荡水柱式波能发电装置的二级能量转换装置,具有自启动性能好、在大流量系数区保持较高效率等优势,近年来应用越来越广泛。有学者提出在冲击式透平动叶片尖端安装环结构的设计,可以改善动叶片叶尖间隙处的气流流动形态,提高透平的工作性能。依托于此观点,构建了安装有环结构的冲击式透平的三维定常数值模型,并通过网格数量无关性及试验数据,验证了该数值模型的准确性与可靠性,随后开展了一系列仿真计算。此外,研究了不同环结构厚度对冲击式空气透平输入系数、扭矩系数及透平效率的影响规律,确定最优结构参数,该优化结果可为实际工程应用中冲击式空气透平的结构选型提供可靠依据。后续将对端板、嵌槽等其他尖端结构展开研究,实现冲击式透平的进一步优化。 相似文献
6.
针对用于海上风力发电机的伞式吸力锚基础(USAF)实际条件下的受力特点,采用数值模拟方法,基于大型通用有限元软件ABAQUS构建数值计算模型,对伞式吸力锚基础在H-V、H-T、V-T荷载平面内以及H-V-T非共面复合加载模式下的承载特性进行分析,进而推导其破坏包络面数学表达式。分析中采用固定位移比加载法进行复合加载,并将桶顶位移作为失效破坏标准。结果表明：(1)拟定的应力归一化复合加载破坏包络面椭圆曲线方程可以较好地模拟不同主筒长径比USAF在不同荷载空间内的破坏包络面形式;(2)H-T空间内USAF复合承载性能随主筒长径比(L/D)的增大而提高,而H-V、V-T空间内变化不明显;(3)绘制了H-V-T空间内USAF三维破坏包络面,可根据实际受荷状态与包络面之间的相对位置关系,评价实际工况下伞式吸力锚基础的稳定性。 相似文献
7.
为了提高潮汐机组双向发电的综合性能,研究了采用单侧、双侧导叶两种形式对贯流式潮汐机组水力性能的影响。基于N-S方程和RNG k-ε湍流模型,采用SIMPLIC算法,分别对采用单侧导叶、双侧导叶方案的水轮机全流道进行了三维定常数值模拟,分析了正向、反向发电时水轮机的内部流动状况。对不同导叶开度下水轮机的水头、流量和力矩等参数进行计算。结果表明,采用双侧导叶时,虽然正向发电效率有所降低,但反向发电的效率大大提高。 相似文献
8.
《海洋湖沼通报》2016,(5)
为研究颗粒粒径对深海采矿提升泵工作性能影响,采用RNGκ-ε湍流模型和Hinze-Tchen颗粒湍流粘性系数模型,运用Fluent软件对采矿提升泵内固液两相流进行数值模拟,比较不同的颗粒粒径对采矿提升泵内颗粒浓度、速度、压力分布的影响,进而分析颗粒粒径对扬程、效率等工作性能的影响,指导深海采矿提升泵的设计。研究结果表明:在转速、流量、颗粒体积分数不变情况下,随着颗粒粒径增大,泵的扬程和效率都逐渐下降;叶轮叶片中前部流道内浆体的颗粒浓度大幅上升,叶轮流道内颗粒动态沉积更加严重,叶轮流道过流面积随之减小,反而加大了叶轮流道内贯流的相对速度,从而有效地抑制了边界层分离的发生,但在叶轮叶片中后部压力面上浆体压力下降幅度较大,泵内浆体总压逐渐下降,扬程随之减小;在叶轮出口处,流道内固液两相流的速度差异增大,在叶轮出口处形成的射流-尾迹结构增强,并在空间导叶流道内形成更加明显的二次流及漩涡,从而加大水力损失,降低效率。实验证实了数值模拟方法的可行性及准确性。 相似文献
9.
导管桨的尾流不稳定性在其性能评价中非常重要,不但是其能否提供稳定推力的保证,而且也与螺旋桨的尾流噪声直接相关。为了改善导管桨的尾流,提高尾流稳定性,并优化导管桨的流场脉动,根据座头鲸鳍肢前缘结节的仿生原理,对导管桨叶片的导边进行改进,提出了两种仿生桨型,采用IDDES湍流模型对低进速系数下常规导管桨和仿生叶片导管桨进行数值模拟,探究叶片构型对导管桨性能和尾流不稳定性的影响。计算结果表明,前缘结节可以有效降低叶片受力波动的幅值和叶片所受合力的主频域峰值,具有较大结节的叶片对导管桨尾流有明显的优化作用,在尾流远场中扩大了流动稳定区,延后了尾流处涡破碎的发生,改善了能量谱密度的频域分布。进一步,大前缘结节叶片导管桨应用在低速工况下时,可以大量减少尾流泄涡区域的二次涡产生,这是由于前缘结节提升了相邻涡互感的强度,使得尾流更加稳定,而小结节叶片仿生桨型对导管桨尾流则无明显优化作用。研究方法和成果可为螺旋桨尤其是导管桨尾流不稳定性研究提供参考,不仅验证了前缘结节在导管桨叶片应用的合理性,而且揭示了其优化尾流稳定性的机理。 相似文献
10.
为了准确设计高压涡轮盘和叶尖间隙,从概率的角度进行了涡轮盘径向变形的分析。介绍了高精度高效率的非线性动态概率分析的极值响应面方法(Extremum Response Surface Method, ERSM),并建立了其数学模型。考虑材料属性和边界条件的非线性,以及热载荷和离心载荷的动态性,基于ERSM对涡轮盘径向变形进行了非线性动态概率分析,得到了输入输出参数的分布特征和影响涡轮盘径向动态变形的主要因素。最后,通过方法比较,验证了ERSM在保证计算精度的前提下能大大提高计算速度,节约计算时间,改善计算效率。为进行更有效的涡轮盘设计和优化,改善叶尖间隙设计和控制的合理性提供了有效依据。 相似文献
11.
Arne Schnack-Friedrichsen Angela M. Davis Jim D. Bennell Dei G. Huws 《Marine Georesources & Geotechnology》2001,19(4):221-243
The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths. 相似文献
12.
Shigehisa Nakamura 《Marine Geodesy》2000,23(1):55-61
Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone. 相似文献
13.
The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics. 相似文献
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15.
《海洋学报(英文版)》2014,(9):F0003-F0003
<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology, 相似文献
16.
The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance. 相似文献
17.
Coastal inundation associated with extreme sea levels is the main factor which leads to the loss of life and property whenever a severe tropical cyclonic storm hits the Indian coasts. The Andhra and Orissa coasts are most vulnerable for coastal inundation due to extreme rise in sea levels associated with tropical cyclones. Loss of life may be minimized if extreme sea levels and associated coastal flooding is predicted well in advance. Keeping this in view, location specific coastal inundation models are developed and applied for the Andhra and Orissa coasts of India. Several numerical experiments are carried out using the data of past severe cyclones that struck these regions. The simulated inland inundation distances are found to be in general agreement with the reported flooding. 相似文献
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19.
Hoi-Soo Jung Kap-Sik Jeong Yong-Shik Chu Sung-Hyun Park Ki-Hyune Kim 《Marine Georesources & Geotechnology》2001,19(3):181-195
Grain size and water content in box-core sediments from the Clarion-Clipperton fracture zone (C-C zone) in the northeast equatorial Pacific were analyzed in detail to understand the downcore variations across a hiatus between Quaternary and Tertiary layers. Grain-size distributions in the topmost core sediments show two modes: a coarse mode (peaked at 50 μm) and a fine mode (at 2-25 μm). The coarse mode disappears gradually with depth accompanied by the dissolution of siliceous fossil tests, whereas the fine mode coarsens due to the formation of authigenic minerals. Water content increases abruptly across a color boundary between an upper pale brown layer and a lower dark brown layer that is the hiatus between Quaternary and Tertiary layers. Abundant smectites and microvoid molds, which are created by the prolonged fossil dissolution in the underlying sediment, are attributed for the abrupt downcore variation of water content. Overall variations in grain size and water content in the topmost core sediments in the western C-C zone are possibly constrained by the dissolution of biogenic siliceous fossils. Variations in geotechnical properties related to these changes must be considered in the design of nodule collectors. 相似文献
20.
Shigehisa Nakamura 《Marine Geodesy》2001,24(1):27-33
This article concerns an interrelation between the sea levels and the western boundary flow near a tectonic boundary in a local zone in the Northwestern Pacific. In this zone, sea level variations at stations located on the coast facing the Pacific are studied to find the interrelation between variations of the Kurosio flow as an index of the distance of the flow axis off a specific coast. The result is discussed after data processing of the monthly means of the sea levels, and a notice is taken of variations caused by active crustal upheavals during a seismic event, a local earthquake. 相似文献