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1.
Currently, very few aquaculture operations are employing airlift pump technology for water recirculation, aeration, and waste removal. This is likely due to the poor design and lower efficiency of traditional airlift design, the limited amount of research effort that has been invested in improving performance capabilities of air lift pumps and the general lack of awareness of the industry about the inherent advantages of airlift systems. A new efficient airlift pump is hydrodynamically designed by incorporating the Volume of Fluid (VOF) multi-phase model along with the K-ε turbulence model utilizing Computational Fluid Dynamics (CFD) tools. The pump is designed to offer a substantial reduction in total energy usage as well as an improved quality of the culture products in order to make it attractive to aquaculture industry. In this study, both numerical and experimental investigations were carried out for airlift systems operating under two different submergence ratios of 50% and 90% in a lab setting using 2.54 cm diameter pumps. Also, the performance of a large-scale pumps of 10.16 cm diameters were also tested in an aquaculture raceway to determine its effect on the operation. The numerical results were found to be in agreement with the experiments within ±20% which is considered very reasonable for multiphase flow analysis. The present study was found to present a great tool for modelling the airlift pump performance, and potentially proposing new designs. 相似文献
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M. Kreuzer S. Müller L. Mazzolini R. E. Messikommer I. D. M. Gangnat 《British poultry science》2020,61(1):33-42
ABSTRACT1. Although fattening dual-purpose types or male layer hybrid chickens appears more ethical than the common practice of culling day-old male layer chicks, the lower feed efficiency of these birds raises concerns. Replacing feed ingredients that compete with food production by those of lower value for human nutrition would be beneficial.2. Lohmann Dual (LD), a modern dual-purpose type, Lohmann Brown (LB), a male layer hybrid, and Hubbard JA 957 (HU), a slow-growing broiler type, were fattened for nine weeks on two diets (control or ?20% crude protein; n = 6 × 12 birds). Growth, carcass and meat quality were analysed.3. Growth performance of HU exceeded that of LD and especially of LB. The growth depression caused by the low-protein diet fed to LD (?7%) was only half of that found in HU (?13%). The LD fed the control diet had the same feed efficiency as the HU fed the low-protein diet. Even the LB had a lower performance and feed efficiency with the low-protein diet in growth. There was a gradient in carcass properties (weight, dressing percentage, breast meat yield, breast proportion and breast angle) from HU to LD to LB, with some additional adverse effects of the low-protein diet especially in HU. There were some breed differences in fatty acid profile in the intramuscular fat.4. In conclusion, the dual-purpose type used complied with regulations for Swiss organic poultry systems in terms of growth rate and was found to respond less when fed a low-protein diet than the slow-growing broiler type. The LB males were inferior in all growth and carcass quality traits. Future studies need to determine the exact protein and amino acid requirements of dual-purpose and layer hybrid chickens and the economic feasibility of the systems, especially for organic farming. 相似文献
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通过对砂光机导向辊动态性能的临界转速分别进行传统计算和有限元分析验证,分析两者之间的差别以及产生误差的原因,从而对导向辊的设计及合理使用提供理论依据。 相似文献
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为改善打后筛分工艺,降低投资运行成本,方便维护保养,对比分析了分别以振筛和滚筒为关键筛分设备的两种打后筛分工艺,从工艺设计依据、质量分析、投资运行、维护保养和持续改进等方面阐述了滚筒式打后筛分工艺的特性.结果表明,该工艺具有成熟的理论和实践基础,工序本身不会引起片烟过多的造碎和卷曲,而且在设备投资、维护保养和改进空间等方面,具有振筛式打后筛分工艺所无法比较的优越性. 相似文献
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林诚魁 《中国农村水利水电》1995,(10)
碾压混凝土具有施工速度快,水泥用量少,投资省等明显的优点。国内的理论研究和工程实践都取得了突飞猛进的进展,在防渗问题方面也进行了卓有成效的探索,如福建省几座已建成的碾压混凝土坝均采用不同的防渗类型。文章结合福建省重点工程连江山仔水利枢纽工程碾压混凝土坝的施工情况,介绍了能够充分发挥碾压混凝土坝快速施工特点的悬臂钢模、改性混凝土的施工方法,论述了喷丙乳砂浆作为碾压混凝土坝上游主防渗体与这一施工特点相统一所具有的优越性。 相似文献
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介绍了电控LPG-柴油双燃料内燃机供给系统的设计,柴油分别采用机械泵和电磁铁执行器供给,LPG采用电控顺序喷射方式供给。同时对控制系统进行了硬件和软件设计,对软件的功能进行详细的说明,最后对双燃料内燃机进行标定试验,论证了柴油的电控喷射对降低烟度排放的影响。 相似文献
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