铸造镁合金Mg-Zn-Y-Zr-Ca在模拟体液中的腐蚀行为

采用光学显微镜和扫描电子显微镜研究了铸态Mg-3Zn-0.6Y-0.5Zr-0.3Ca(质量分数/%)合金的显微组织,采用失重法测试了合金在模拟体液中浸泡不同时间的生物腐蚀性能,并对合金的腐蚀行为进行分析。结果表明,Mg-3Zn-0.6Y-0.5Zr-0.3Ca合金中沿晶界连续分布的Mg3YZn6相对合金的腐蚀具有作为微阴极加速基体腐蚀或抑制腐蚀扩展的双重作用。Mg-3Zn-0.6Y-0.5Zr-0.3Ca合金的腐蚀过程分为3个阶段:晶界附近溶质原子贫化区形成几微米宽的腐蚀凹槽,在富Zr-贫Zr区形成大量腐蚀斑点,腐蚀凹槽和腐蚀斑点相互扩展破坏基体。

Gd对心血管支架用Mg-Zn-Gd-Zr合金的腐蚀性能的影响

为了改善Mg-Zn-Zr三元合金的耐腐蚀性能,通过添加稀土元素Gd制备含量分别为0%、1%、2%和3%的Mg-4Zn-x Gd-0.4Zr四元镁合金。使用光学显微镜、X射线衍射仪、扫描电镜、电化学工作站以及浸泡实验,研究了在模拟血液中四元合金的腐蚀性能。结果表明,添加Gd元素以后,合金中出现了Mg3Gd新相,合金的晶粒得到了细化,同时合金的耐腐蚀性能有了很大的提高。Mg-4Zn-1Gd-0.4Zr在本次研究中表现出了最优异的耐腐蚀性能。

面向复杂智能制造的多维时空建模方法与应用

为了解决复杂智能制造流程、技术和系统的综合建模问题,提出多维时空建模方法和基础建模元素,包括坐标矩阵、伴随矩阵、伴随关系、伴随指数、扩展矩阵、影子矩阵、属性矩阵、N方矩阵、关联定参法则、关联参数转化法则,在此基础上提出面向智能制造抽象过程和结构的类簇、类、对象,提出面向智能制造具体过程和结构的智能制造数据优化、智能制造信息无损压缩和有损压缩、智能制造数据清洗、智能制造反求和逆向工程,进一步提出带有时空耦合、时空反馈的智能制造复杂结构软硬件的逻辑和空间结构建模方法,带有矛盾流程和矛盾结构、模糊流程和模糊结构及带有时间和条件约束的复杂时序数据和管理流程的综合建模方法.实现了对具有多个组件、多个模块、多个制造设备、多个制造流程、多种制造材料、多种制造工艺的复杂构件和大规模软件进行实例逻辑建模和实例空间结构建模.最后通过对亚萨合莱智能概念锁和钥匙的复杂智能制造流程、功能、原理进行综合建模和反求,说明面向复杂智能制造的多维时空建模方法具有有效性、实用性和功能性.

Effect of tip geometry and tip clearance on aerodynamic performance of a linear compressor cascade

The tip leakage flow between a blade and a casing wall has a strong impact on compressor pressure rise capability, efficiency, and stability. Consequently, there is a strong motivation to look for means to minimize its impact on performance. This paper presents the potential of passive tip leakage flow control to increase the aerodynamic performance of highly loaded compressor blades. Experimental investigations on a linear compressor cascade equipped with blade winglets mounted to the blade tips have been carried out. Results for a variation of the tip clearance and the winglet geometry are presented. Current results indicate that the use of proper tip winglets in a compressor cascade can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction-side winglets are aerodynamically superior to the pressure-side or combined winglets. The suction-side winglets are capable of reducing the exit total pressure loss associated with the tip leakage flow and the passage secondary flow to a significant degree.

Effect of blade tip winglet on the performance of a highly loaded transonic compressor rotor

The tip leakage flow has an important influence on the performance of transonic com- pressor. Blade tip winglet has been proved to be an effective method to control the tip leakage flow in compressor, while the physical mechanisms of blade tip winglet have been poorly understood. A numerical study for a highly loaded transonic compressor rotor has been conducted to understand the effect of varying the location of blade tip wing]et on the performance of the rotor. Two kinds of tip winglet were designed and investigated. The effects of blade tip winglet on the compressor over- all performance, stability and tip flow structure were presented and discussed, It is found that the interaction of the tip winglet with the flow in the tip region is different when the winglet is located at suction-side or pressure-side of the blade tip. Results indicate that the suction-side winglet （SW） is ineffective to improve the performance of compressor rotor. In addition, a significant stall range extension equivalent to 33.74% with a very small penalty in efficiency can be obtained by the pressure-side winglet （PW）. An attempt has been made to explain the fundamental mechanisms of blade tip winglet in detail.

Research Progress of Tip Winglet Technology in Compressor

In the present study,the research progress of tip winglets that control tip clearance leakage flow in compressors is reviewed.Firstly,the effects of tip leakage flow on the aerodynamic performance of the compressor are presented.Subsequently,the development of tip winglet technology is reviewed.Next,a series of studies on compressor tip winglet technology are conducted.Besides,the effects of tip winglets on the aerodynamic performance of rectangular cascades of low-speed and high-subsonic compressors,subsonic compressor rotor and transonic compressor rotor are discussed,respectively,and the control effect of tip winglet technology combined with tip groove design on tip leakage is investigated.Lastly,the subsequent development direction and research prospect of compressor tip winglet technology are presented.

叶尖小翼结合凹槽对跨声速压气机转子间隙流场的影响

为了揭示叶尖小翼结合叶顶凹槽对跨声速压气机转子气动性能的影响机理,采用数值模拟方法研究了NASA Rotor35附加不同凹槽型叶尖小翼的气动特性,并在分析Rotor35失稳机制的基础上探究了叶尖小翼结合叶顶凹槽的扩稳机理。研究结果表明:不同深度的凹槽型小翼均使得压气机转子总压比和等熵效率有所降低。随着凹槽深度的增加,压气机转子失速裕度先增大后减小,存在最佳深度的凹槽型小翼使压气机转子失速裕度增加5.4%。凹槽型小翼方案中压气机转子叶尖负荷降低,叶尖泄漏涡强度减弱,转子叶尖通道激波后移,叶尖泄漏涡与激波干涉后发生螺旋型破裂,降低了波/涡干涉所导致的通道堵塞程度及抑制了叶片吸力面附面层分离是其扩稳的机制所在。

Effect of Winglet Geometry Arrangement and Incidence on Tip Clearance Control in a Compressor Cascade

An experimental study is conducted to investigate the influences of blade tip winglet on the flow field of a compressor cascade. The tests are performed in a low speed linear cascade with stationary endwall, with three blade tip configurations, including the baseline tip, the suction-side winglet tip and the pressure-side winglet tip. The flowfield downstream of the cascade is measured using five-hole probe, from which the three-dimensional velocity field, vorticity field and pressure field are obtained. Static pressure measurements are made on the endwall above the blade row using pressure taps embedded in the plywood endwall. All measurements are made at both design and off-design conditions for tip clearance level of about 2 percent of the blade chord. The results revealed the incidence variation significantly affects the secondary flow and the associated loss field downstream of the cascade, where the tip leakage vortex and passage vortex exist as the major contributors on the field. The winglet geometry arrangements can change the trajectory of the tip leakage vortex. The suction-side winglet tip blade provides a lower overall total pressure loss coefficient when compared to the baseline tip blade and pressure-side winglet tip blade at all incidence angles.