A novel shaft-less double suction mini pump

A novel double suction shaft-less mini pump was developed for heat control of small energy systems in this study.The mini pump impeller with an exit diameter of 40 mm was combined with the motor rotor supported by the hybrid dynamic bearing.The specific speed of the pump was 125 min-1 m3 min-1 m.The hydraulic performance of the pump was investigated experimen-tally under four rotational speeds.From the test results,it was recognized that the pump could provide a flow discharge of 5 L/min and head of 1.5 m,w...     

Air-source heat pump coupled with economized vapor injection scroll compressor and ejector:Design and experimental research

Ejector can utilize high pressure energy from liquid mechanism,it can be used in heat pump system coupled with economized vapor injection(EVI)scroll compressor.When running under low temperature conditions,the performance of the EVI system with ejector can be improved further.In this paper,the design method of the heat pump system with ejector is presented,and the process for designing the heat pump with ejector(EVIe)was summarized.One prototype heat pump was designed under the condition of the evaporation ...     

Preparation,characterization and salt-resistance of a coal based super absorbent composite

Potassium humate was extracted from brown coal.A novel super absorbent composite,poly (acrylic acid-co-acrylamide)/potassium humate (PAA-AM/KHA),was prepared by graft polymerization of acrylic acid,acrylamide and coal based potassium humate using N,N'-methylenebisacrylamide as a crosslinker and potassium peroxydisulfate as an initiator.The effects of reaction temperature,degree of neutralization of the poly (acrylic acid) and the amounts of crosslinker,initiator and potassium humate were investigated.Salt resistance tests were also carried out.The composite prepared under optimal conditions had a potassium humate content of 10% and exhibited a water absorption of 770 g/g in distilled water,and 349,286 and 41 g/g in 0.5 mol/L KC1,MgCl2 and AlCl3 solutions respectively.The results indicate that the salt resistance of PAA-AM/KHA was superior to that of poly (acrylic acid-co-acrylamide) because of the collaborative effect of functional groups of the coal based potassium humate.The PAA-AM/KHA micro powder was characterized by IR spectroscopy and the micrographic surface was characterized by scanning electron microscopy.Introduction of potassium humate into the poly (acrylic acid-co-acrylamide) structure creates a composite more suitable for use as a water-managing material in the renewal of arid and desert environments.The salt resisting property of the composite is improved,production costs are reduced and the growth stimulant effect is still present.     

危险传染病应急诊疗病房通风管道的优化设计

针对危险传染病的应急诊疗,研制出移动式危险传染病应急诊疗病房,为降低危险传染病应急诊疗病房的整体质量及棚顶的压力,以通风口的质量最轻为目标函数,以各个进气支路的进气量相等为约束条件,结合沿程阻力损失系数与管路横截面边长的关系式推导出通风管道约束函数关系式,利用MATLAB优化工具箱对模型求解,优化得到通风管道的最佳尺寸.根据优化设计结果设计了通风管道,满足实际使用要求.     

光催化-Fenton工艺处理废纸制浆废水

为有效处理废纸制浆废水,采用氙灯照射下的光催化-Fenton技术,研究不同反应器、曝气、草酸钾、H2O2投加方式和废水质量浓度对光-Fenton工艺去除废水中TOC或吸光度的影响.结果表明,提高光照强度可提高TOC去除率;添加适量的草酸钾可提高处理效果;H2O2分两次投加可取得较好的处理效果,大大减少对催化剂的需求;在处理过程中使废水暴露于空气可提高有机物的脱氯效果,但曝气对处理效果并无益处.对于TOC为185 mg/L左右的废纸制浆废水,在[H2O2]=1000 mg/L、[Fe(Ⅱ)]=100 mg/L、pH=3.0、温度为30℃的条件下,经过30 min处理,废水的TOC可去除63%以上.     

圆管层流脉动流动的数值模拟

为研究圆管层流脉动流动特性,建立了二维非稳态轴对称模型,对壁温恒定、入口速度周期性变化的流体进行数值模拟.分析了速度振幅和频率对层流流动的影响,得到了频率和振幅对压力、温度、壁面摩擦系数影响的规律.研究表明:脉动流动时,压力、温度、壁面摩擦系数围绕相同Re下稳态流动时的数值波动;压力与速度之间存在相位差;压力、壁面摩擦系数的波动与速度振幅和频率成正比;温度的波动与速度振幅成正比,与频率呈反比;当流体脉动的频率和振幅足够大时,会在近壁面处出现回流,并且出现回流的时间会随着频率和振幅的增大而增长.     

数控超声磨削陶瓷叶片型面刀位轨迹计算

介绍了陶瓷超声磨削加工现状,建立了平行直纹面数学模型.分析了用圆柱磨轮四轴数控超声磨削平行直纹面时原理误差,并提出减小误差的措施,计算出磨轮空间轨迹,并进行陶瓷叶片型面超声磨削加工工艺试验.试验结果表明,超声磨削加工陶瓷叶片型面是可行的,所完成的刀位计算可有效减小原理误差.     

城市污水的层流换热特性理论

为有效利用城市污水热能,以污水源热泵系统中的流动工质——城市污水为研究对象,通过理论分析的方法,对其层流状态下的换热特性进行理论推导和实验验证.结果表明:污水作为热泵的冷热源,有良好的换热特性,推导得出的换热准则关联式h=4.53λ/D,为污水源热泵系统设计提供依据,同时为应用污水余热技术提供理论基础.     

OFDM快速频偏估计方法

提出一种基于前导符号为L等分结构的OFDM快速频偏估计的新方法,该方法只需一个OFDM符号作为前导符号,数据开销较小.接收端先用相关求相角的方法完成细频偏估计,再对经过细频偏补偿后的前导数据进行符号重构,然后对重构符号采用L点FFT运算,通过寻找频域信号峰值,对剩余频偏进行估计,从而完成粗频偏估计.为进一步降低系统的计算开销,采用了多级判决方式.计算机仿真表明,该方案具有计算复杂度低,估计性能较高的优点.     

HP nonlinear guidance law design based on smooth sliding mode control

To eliminate the perturbation of interceptor detection induced by aerodynamic heating,the head pursuit (HP) guidance law for three-dimensional interception was presented. The guidance law positioned the interceptor ahead of the target on its flight trajectory,and the speed of interceptor was required to be lower than that of the target. On the basis of a novel head pursuit three-dimensional guidance model,a nonlinear guidance law was developed based on smooth sliding mode control theory. At the same time,a special observer was designed to estimate the target acceleration,and a numerical example on maneuvering ballistic target interception verified the effectiveness of the presented guidance law.