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近海拖网渔船推进系统探讨——前置导管螺旋桨的论证与设计 总被引：1，自引：0，他引：1
以山东１０４总吨钢质拖网渔船为母型船，对其进行了四种推进装置的设计与分析论证，筛选出适应近海拖网渔船多工况的较佳推进装置。通过对楚思德Ｂ型桨（以下简称Ｂ型桨）、１９Ａ导管桨（以下简称导管桨）、楚思德Ｂ型桨配双级变速齿轮箱（以下简称双级变速Ｂ型桨）以及１９Ａ导管桨配双级变速齿轮箱（以下简称双级变速导管桨）这四种推进装置的设计比较得出：双级变速导管桨最佳，双级变速Ｂ型桨次之，导管桨又比Ｂ型桨为优。以Ｂ型桨为基准，拖网时导管桨拖力增加２０．５％，双级变速Ｂ型桨增加为２８．２％，双级变速导管桨增加为４４．５％；从效率上看，以Ｂ型桨为基准，导管桨效率提高为２．５％，双级变速Ｂ型桨提高为６．３％，双级变速导管桨提高为７．５％。双级变速导管桨明显优于其他三种，可充分利用主机功率；但普通导管的剥蚀严重，因此在上述设计论证的基础上将导管前置，前置导管能减少空泡剥蚀，同时使尾流均一化和稳定化，有利于减小船体阻力和提高推进效率 相似文献
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设计导管螺旋桨中的几个问题 总被引：1，自引：0，他引：1
导管螺旋桨作为一种特种推进器正发挥着越来越大的作用。由于它最适用于拖轮(推轮)和拖网渔船这一类负荷比较重的推进装置上，因此这一简便可靠的节能推进器在渔业上得到了广泛的应用。本文对导管螺旋桨图谱设计中的几个问题作一概要的探讨，并对几种推进装置的性能作了比较。 相似文献
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本文阐述了导管螺旋桨推进装置的工作原理，导管桨和导管的选型，可按捕捞业时网具阻力Ｒ网和船体阻力Ｒ的比值大小来决定自由航行状态，拖网状态，折状态三种设计工况，并指出应导管桨的空泡腐蚀进行研究。 相似文献
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根据目前拖网渔船在节能方面的需要,采用导管螺旋桨以改善渔船的推进性能,并对导管螺旋桨的设计和具体应用的优的缺点作初步的探讨。 相似文献
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导流管主要参数对导管桨性能的影响 总被引：1，自引：0，他引：1
１前言导管螺旋桨问世至今，已得到了广泛的推广和应用、由于其最显著的特点是在重载时有较高的效率．因而在渔业生产中特别适宜于拖网渔船。目前，在我国的拖网渔船中导管桨正日益得到推广．它和普通桨比较。在拖网工况时。拖力可提高３０％左右，而在自由航行工况时航速几乎相当。使得这一特种推进器越来越受到渔民的欢迎。在设计导管桨中、目前用得较多的是两种类型的导管：代表机翼型剖面Ｎｏ．１９Ａ导管和代表折角型的上海交通大学ＪＤ７７０４导管。实践证明，只要导管的主要参数（如导管的长径比、收缩系数、扩散系数等）选择恰当，… 相似文献
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本文根据木质拖网渔船改装固定导管桨前后的试验及生产实践情况，阐述了装用导管桨节能的可行性，提出了对木质船体结构加强及固定导管桨的安装要求。 相似文献
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如图所示，当发动机2运转带动抽水机3工作时，网箱体1外含氧丰富的水，自吸水口4吸入，从出水口5输出。从5输出的水与从空气吸收管6吸入到喷射器7内的空气进行气水混合，并经导管8及喷嘴9，引入到缺氧的网箱体1内进行高效率的充气。曝气设备安装在网箱体1外，是为了有效地利用网箱内的空间以便充气。连接喷嘴的导管具有可挠性，不会因为通过喷嘴进行气水混合时折损导管。 相似文献
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本文介绍了在三艘实船上采用渐缩管(矩形截面)的进气导管型式，以提高气体流速、增加进气量为目的，已成功地代替了原6135船用非增压柴油机采用空气滤清器及进气总管的结构，使6135船用非增压柴油机节油率达5～6％(约提高柴油机功率7～10马力)左右。此外，文中推荐的进气导管的实用算式还具有一定的通用性等等，可供有关人员参考。 相似文献
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- 1. Recreational power boating is growing in popularity in North America. This activity is known to have lethal and sub‐lethal effects on aquatic wildlife and freshwater turtles may be particularly sensitive to this activity.
- 2. This study reports on patterns of traumatic injuries inflicted by powerboat propellers to northern map turtles (Graptemys geographica) from two sites differing in boat traffic intensity in Ontario, Canada.
- 3. The relative vulnerability of turtles was assessed, in light of seasonal patterns in boat traffic, as a function of sex‐ and age‐specific movement patterns, habitat use, and basking behaviour obtained by radio‐telemetry. Population viability analyses (PVA) were also conducted to evaluate the potential demographic consequences of mortality induced by powerboats.
- 4. The prevalence of propeller injuries was two to nine times higher in adult females than in adult males and juvenile females. Patterns of movement, habitat use, and aquatic basking indicated that adult females are more exposed to collisions with boats. PVA showed that boat‐induced mortality in adult females could lead to rapid population extinction if the risk of mortality when hit by a boat is greater than 10%.
- 5. The results of this study showed that recreational power boating is a serious threat to northern map turtles, even under moderate boat traffic. The need to adopt measures restricting boat traffic in areas important to turtles is discussed. Copyright © 2009 John Wiley & Sons, Ltd.
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为了探究潜水推流器作用下八边形养殖池内的污物聚集特点,本研究利用物理模型试验的方法,研究潜水推流器不同的布设角度θ、布设距离比d/a (中垂线模式：d1为推流器叶轮轴线中点与最近的池壁之间的距离,a1为八边形养殖池长边边长;对角线模式：d2为推流器叶轮轴线中点与最近的短边边长之间的距离,a2为八边形养殖池排污口与最近的短边边长之间的距离)、推流器数量n和布设模式对八边形养殖池内污物聚集的影响。试验利用高清相机记录养殖池内的污物分布情况,并使用MATLAB分析计算污物与池中心的距离。实验中通过比较不同工况下污物与池中心距离的最大值的大小,衡量养殖池集污性能的优劣。结果显示,潜水推流器的布设角度θ、布设距离比d/a、推流器数量n以及布设模式都影响池内污物聚集的效果。在本研究设置的布设距离比工况下,潜水推流器布设角度θ为45°时集污效果最优,而当布设角度θ大于70°时,随着布设角度增加,八边形养殖池周边出现集污死角,残饵及粪便距离排污口中心变远且饲料离散程度变大;在30°、40°、45°、50°工况下,污物聚集效果随布设距离比d/a的增大逐渐增强,当布设距离比为1/2时集污效果最好。养殖池集污性能随潜水推流器数量的增加而整体呈现增强的趋势,尤其是潜水推流器数量从1增加至2时,集污性能明显提升,但是持续增加后,集污性能不再有明显的提升。其余设置条件相同的情况下,对角线布设模式下的养殖池集污性能明显优于中垂线布设模式。研究表明,潜水推流器采取对角线模式,布设时不少于2个,布设角度θ为45°附近,此时八边形养殖池集污性能较优。研究结果可为八边形养殖池内潜水推流器的布设方式提供依据与指导。 相似文献
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为了对4种不同开口大小的六边形开口方形人工鱼礁在4种迎流角度下数值模拟和水槽模型试验的阻力系数进行对比验证,分别利用水槽模型和数值模拟试验方法对4种不同开口比（γty=0.0625,0.14,0.25,0.39）六边形开口方形人工鱼礁在4种迎流角度（θ=0°,15°,30°,45°）状态下的阻力进行测定,并计算两种方法的阻力系数。结果表明：（1）在数值模拟和水槽模型试验中,人工鱼礁模型阻力均随着开口比的增大而减小;礁体迎流角度的变化可改变礁体阻力,且在4种迎流角度下,人工鱼礁阻力在θ=30°时最大。（2）人工鱼礁数值模拟与水槽模型试验中,当θ为15°、30°和45°时,阻力系数均随着开口比的增加而增加,具有明显的线性关系,且阻力系数在迎流角度θ=30°时最大。（3）数值模拟与模型试验阻力的相对误差在0.12%~17.18%,平均误差7.43%;礁体阻力系数的相对误差在0.03%~14.64%,平均误差5.26%。阻力及阻力系数误差均在20%以下。水槽模型试验与数值模拟阻力和阻力系数相关系数R分别为0.99和0.80,P<0.001,具有极强的相关性。因此,利用数值模拟精细化研究人工鱼礁水动力性能是可行的。 相似文献
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Michael H. Meeuwig Christopher S. Guy Wade A. Fredenberg 《Ecology of Freshwater Fish》2011,20(2):315-325
Abstract – Bull trout, a species of char listed as threatened under the US Endangered Species Act, have been displaced from portions of their historic range following the introduction of nonnative lake trout. It has been suggested that competitive exclusion as a result of trophic overlap between bull trout and lake trout may be the causal mechanism associated with displacement of bull trout. This study used stable isotope data to evaluate trophic relationships among native bull trout, nonnative lake trout and other fishes in seven lakes in Glacier National Park (GNP), Montana. Bull trout and lake trout had greater δ15N values relative to other fishes among lakes (δ15N ≥ 3.0‰). Lake trout had greater δ15N values relative to bull trout (δ15N = +1.0‰). Bull trout had greater δ13C values relative to lake trout in six of the seven lakes examined. Although both bull trout and lake trout had greater δ15N values relative to other fishes within lakes in GNP, differences in δ15N and δ13C between bull trout and lake trout suggest that they are consuming different prey species or similar prey species in different proportions. Therefore, displacement of bull trout as a direct result of complete overlap in food resource use is not anticipated unless diet shifts occur or food resources become limiting. Additionally, future studies should evaluate food habits to identify important prey species and sources of partial dietary overlap between bull trout and lake trout. 相似文献
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Yukihiro Kitade Michiko Nakamura Hirotoshi Endo Satoru Fukuda Kazuyoshi Kuwano Naotsune Saga 《Fisheries Science》2006,72(3):639-645
ABSTRACT: A cDNA ( PyARP4 ) containing an open reading frame for a protein of 573 amino acids was identified in the marine red alga Porphyra yezoensis . The conceptual PyARP4 protein exhibits significant similarity to actin-related protein (ARP) 4 in the terrestrial plant Arabidopsis . Comparison of the deduced amino acid sequence showed moderate sequence identity (30%) to a conventional actin in P. yezoensis , as seen in comparisons between ARP and conventional actins of other organisms. A putative bipartite nuclear localization signal and an actin motif were found within the PyARP4 amino acid sequence. In a phylogenetic analysis, the PyARP4 was found to cluster with the ARP4 of other organisms. The expression level of PyARP4 did not change significantly among four developmental stages of life cycle and was lower than that of a conventional actin. This cDNA therefore may serve as a useful internal standard in gene expression analyses of differentially expressed genes in P. yezoensis . 相似文献