转动输送管制备半固态ZL101合金浆料

采用转动输送管方法制备了半固态ZL101合金浆料,并对不同工艺参数条件下的合金微观组织形成和演化过程进行了研究.试验结果表明,控制浇注温度(640 ℃)、输送管转速(232 r/min)、结晶器冷却强度(结晶器预热470 ℃)等工艺参数,能得到圆整的半固态显微结构,适当的浇注温度和输送管转速可以提高熔融态合金的有效形核数目,降低结晶器冷却强度有利于初生α相呈近球形生长.     

盾构管片拼装机设计研究

在盾构施工过程中,随着盾构机的开挖、推进和出碴,开挖后的隧道需要用洞外预制好的钢筋混凝土管片进行永久性支护。管片拼装机的功能就是将管片准确地放到恰当的位置,并能安全快速地把管片组装成所定形式。     

Environmental contamination and hospital‐acquired infection: factors that are easily overlooked

There is an ongoing debate about the reasons for and factors contributing to healthcare‐associated infection (HAI). Different solutions have been proposed over time to control the spread of HAI, with more focus on hand hygiene than on other aspects such as preventing the aerial dissemination of bacteria. Yet, it emerges that there is a need for a more pluralistic approach to infection control; one that reflects the complexity of the systems associated with HAI and involves multidisciplinary teams including hospital doctors, infection control nurses, microbiologists, architects, and engineers with expertise in building design and facilities management. This study reviews the knowledge base on the role that environmental contamination plays in the transmission of HAI, with the aim of raising awareness regarding infection control issues that are frequently overlooked. From the discussion presented in the study, it is clear that many unknowns persist regarding aerial dissemination of bacteria, and its control via cleaning and disinfection of the clinical environment. There is a paucity of good‐quality epidemiological data, making it difficult for healthcare authorities to develop evidence‐based policies. Consequently, there is a strong need for carefully designed studies to determine the impact of environmental contamination on the spread of HAI.     

Using energy audits to investigate the impacts of common air-conditioning design and installation issues on peak power demand and energy consumption in Austin, Texas

This study presents an analysis of a unique dataset of 4971 energy audits performed on homes in Austin, Texas in 2009–2010. We quantify the prevalence of typical air-conditioner design and installation issues such as low efficiency, oversizing, duct leakage, and low measured capacity, and estimate the impacts that resolving these issues would have on peak power demand and cooling energy consumption. We estimate that air-conditioner use in single-family residences currently accounts for 17–18% of peak demand in Austin, and we found that improving equipment efficiency alone could save up to 205 MW, or 8%, of peak demand. We estimate that 31% of systems in this study were oversized, leading to up to 41 MW of excess peak demand. Replacing oversized systems with correctly sized higher efficiency units has the potential for further savings of up to 81 MW. We estimate that the mean system could achieve 18% and 20% in cooling energy savings by sealing duct leaks and servicing their air-conditioning units to achieve 100% of nominal capacity, respectively. Although this analysis is limited to the City of Austin, understanding the methods described herein could allow electric utilities in similar climates to make better-informed decisions when considering efficiency improvement programs.     

永宏PLC在风管生产线中的应用

本文在介绍了风管机生产线系统的基础上,基于满足系统所需要的工艺的情况下,永宏FBs系列PLC的中断及高速脉冲输出功能,使本系统稳定高效率的运行的解决方案。     

共同沟的通风设计

介绍共同沟通设计的几种方式，着重说明通风方式的选择，防火分区、通风分区的划分、通风温度的确定、通风量的计算及通风系统等几个方面的问题。     

紫外老化箱风道及试验箱结构的优化设计

本文就BUV2000C型紫外老化箱进行CFD数值模拟仿真,对其试验室箱体及风道截面温度分布图及流场轨迹图进行了分析,发现温度偏差较大,箱体内空气流场紊乱。在此基础上,提出一种风道及试验箱排风口结构的改进设计方案,用仿真软件建立试验箱及风道模型后对其进行气体流场及温度分布模拟,得到了温度偏差较小的模拟结果。为BUV2000C型老化箱的优化设计提供了有价值的参考。     

Effects of the ventilation duct arrangement and duct geometry on ventilation performance in a subway tunnel

This study has investigated numerically the effects of the ventilation duct number and duct geometry on duct ventilation performance in a subway tunnel. A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train, which was validated against the model tunnel experimental data in a previous study, is adopted to simulate train-induced unsteady tunnel flows. For the tunnel and subway train geometries that are exactly the same as those used in the model tunnel experimental test, but with the ventilation ducts being connected to the tunnel ceiling, the three-dimensional tunnel flows are simulated numerically under five different ventilation duct numbers and two different duct geometries. The numerical results reveal that: (1) for a given total area of openings, the ventilation duct number has little influence on the total mass flow of the air sucked into the tunnel through the ventilation ducts while the total mass flow of the air pushed out of the tunnel through the ducts increases remarkably with the increase in the duct number; (2) with the increase of the distance between a specific ventilation duct and the tunnel inlet the suction mass flow through the duct decreases significantly while the exhaust mass flow through the duct increases greatly, i.e., the location of a specific duct has a strong impact on the total suction and exhaust mass flows through the ventilation duct; (3) as the linkage angle between the tunnel ceiling and the upstream side wall of a duct is changed from 90° to 45°, the size of the re-circulation area inside the duct is much reduced when the train approaches the duct and thus the amount of air pushed out of the duct is greatly increased (i.e. the exhaust effect through the duct is remarkably strengthened).     

Effects of nozzle-strut integrated design concepton on the subsonic turbine stage flowfield

In order to shorten aero-engine axial length,substituting the traditional long chord thick strut design accompanied with the traditional low pressure（LP） stage nozzle,LP turbine is integrated with intermediate turbine duct（ITD）.In the current paper,five vanes of the first stage LP turbine nozzle is replaced with loaded struts for supporting the engine shaft,and providing oil pipes circumferentially which fulfilled the areo-engine structure requirement.However,their bulky geometric size represents a more effective obstacle to flow from high pressure（HP） turbine rotor.These five struts give obvious influence for not only the LP turbine nozzle but also the flowfield within the ITD,and hence cause higher loss.Numerical investigation has been undertaken to observe the influence of the Nozzle-Strut integrated design concept on the flowfield within the ITD and the nearby nozzle blades.According to the computational results,three main conclusions are finally obtained.Firstly,a noticeable low speed area is formed near the strut＇s leading edge,which is no doubt caused by the potential flow effects.Secondly,more severe radial migration of boundary layer flow adjacent to the strut＇s pressure side have been found near the nozzle＇s trailing edge.Such boundary layer migration is obvious,especially close to the shroud domain.Meanwhile,radial pressure gradient aggravates this phenomenon.Thirdly,velocity distribution along the strut＇s pressure side on nozzle＇s suction surface differs,which means loading variation of the nozzle.And it will no doubt cause nonuniform flowfield faced by the downstream rotor blade.     

Effects of rising angle on upstream blades and intermediate turbine duct

With the improvement of requirement, design and manufacture technology, aero-engines for the future are characterized by further reduction in fuel consumption, cost, but increment in propulsion efficiency, which leads to ultra-high bypass ratio. The intermediate turbine duct (ITD), which connects the high pressure turbine (HPT) with the low pressure turbine (LPT), has a critical impact on the overall performances of such future engines. Therefore, it becomes more and more urgent to master the design technique of aggressive, even super-aggressive ITDs. Over the last years, a lot of research works about the flow mechanism in the diffuser ducts were carried out. Many achievements were reported, but further investigation should be performed. With the aid of numerical method, this paper focuses on the change of performance and flow field of ITD, as well as nearby turbines, brought by rising angle (RA). Eight ITDs with the same area ratio and length, but different RAs ranges from 8 degrees to 45 degrees, are compared.According to the investigation, flow field, especially outlet Ma of swirl blade is influenced by RA under potential effect, which is advisable for designers to modify HPT rotor blades after changing ITD. In addition to that, low velocity area moves towards upstream until the first bend as RA increases, while pressure loss distribution at S2 stream surface shows that hub boundary layer is more sensitive to RA, and casing layer keeps almost constant. On the other hand, the overall total pressure loss could keep nearly equivalent among different RA cases, which implies the importance of optimization.