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Global Search of a Three-dimensional Low Solidity Circular Cascade Diffuser for Centrifugal Blowers by Meta-model Assisted Optimization

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Journal of Thermal Science 2018年第2期27卷 111-116页

作者： Daisaku Sakaguchi Daiki Sakue min thaw tun Nagasaki University 1-14 Bunkyo-machi Nagasaki 852-8521 Japan Yangon Technological University Insein Road East Gyogone Insein Township Yangon

A three-dimensional blade of a low solidity circular cascade diffuser in centrifugal blowers is designed by means of a multi-point optimization technique. The optimization aims at improving static pressure coefficient at a design point and at a small flow rate condition. Moreover, a clear definition of secondary flow expressed by positive radial velocity at hub side is taken into consideration in constraints. The number of design parameters for three-dimensional blade reaches to 10 in this study, such as a radial gap, a radial chord length and mean camber angle distribution of the LSD blade with five control points, control point between hub and shroud with two design freedom. Optimization results show clear Pareto front and selected optimum design shows good improvement of pressure rise in diffuser at small flow rate conditions. It is found that three-dimensional blade has advantage to stabilize the secondary flow effect with improving pressure recovery of the low solidity circular cascade diffuser.

关键词：优化技术三维串联固态离心元模型搜索圆形

Flow Range Enhancement by Secondary Flow Effect in Low Solidity Circular Cascade Diffusers

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Journal of Thermal Science 2014年第4期23卷 391-400页

作者： Daisaku Sakaguchi min thaw tun Kanata Mizokoshi Daiki Kishikawa Nagasaki Japan

High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confirm the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser(LSD) in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow ef

关键词：二次流动流量范围扩散器密实度多目标优化叶片扩压器设计流量粒子图像测速仪

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侵蚀和冻融环境下水泥土强度的试验研究

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兰州交通大学学报 2014年第4期33卷 89-92,104页

作者：杨暾赖天文兰州交通大学土木工程学院甘肃兰州730070

某些特殊地区的水泥土地基既受到环境侵蚀又受到冻融循环的影响.通过室内试验的方法,研究水泥土先经受不同浓度和不同pH值的侵蚀性溶液侵蚀下,经过反复冻融后水泥土的强度特征,并探讨其强度改变的机理.试验结果表明,水泥土的强度特性受... 详细信息

某些特殊地区的水泥土地基既受到环境侵蚀又受到冻融循环的影响.通过室内试验的方法,研究水泥土先经受不同浓度和不同pH值的侵蚀性溶液侵蚀下,经过反复冻融后水泥土的强度特征,并探讨其强度改变的机理.试验结果表明,水泥土的强度特性受水化学作用和冻融循环的双重影响,其中水化学作用的影响贯穿全过程,冻融的影响与冻融循环次数关系紧密.结果可为特殊环境地基的设计与工程应用提供指导作用.

关键词：水泥土环境侵蚀冻融循环无侧限抗压强度