潮流能水平轴水轮机在剪切来流下的水动力分析

采用基于计算流体力学方法的全尺度数值模拟计算,建立了适用于潮流能水轮机模拟的剪切来流环境,通过数值计算结果,对潮流能水轮机随时间变化的宏观力和流场特征进行了系统分析,探索水轮机在复杂工况下的水动力特性规律。结果表明,水轮机整个叶轮的总体平均受力在剪切流工况中未受到明显影响; 单个叶片的瞬态轴向力系数和瞬态轴向扭矩系数在旋转周期内出现了明显的周期性变化,且周期性变化幅值随转速增大而增大; 非定常的瞬时轴向扭矩和力的周期性振荡容易引起单个叶片的结构性振动,可能对水轮机的机械结构造成影响。     

转速对2524铝合金搅拌摩擦点焊组织与性能的影响

对2524铝合金薄板进行搭接搅拌摩擦点焊试验, 研究了搅拌头转速对其组织与性能的影响。结果表明, 随转速增加, 焊点外侧飞边越加严重, 组织畸变程度增加, 焊核区宽度增大, 有效连接宽度先增大后减小。母材区硬度最大, 热影响区硬度最低;在焊核区内, 显微硬度随转速增加而增大, 当转速为1 100 r/min时达到最大133.9HV, 而热影响区在300 r/min时硬度最大。在单向拉伸试验中, 接头剪切强度随转速增加先增大后减小, 在700 r/min时达到最大值3 510 N;接头呈现出两种断裂模式: 即低转速下平行于两板面断裂和高转速下沿倾斜方向断裂;断口呈现明显的剪切韧窝形态, 韧窝小而浅, 焊接接头为韧性断裂。     

Alloy optimisation of bainitic steel for large plastic mould

Based on the phase transformation theories, especially the T₀ concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s^??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm.     

酸性废水中As(Ⅲ)、Cu(Ⅱ)与铁粉的反应行为

在Fe-As(Ⅲ)-Cu(Ⅱ)-H₂O体系中, 研究了酸性废水中As(Ⅲ)、Cu(Ⅱ)与金属铁粉的反应行为, 考察了反应过程中As在气、液、固三相中的分配比。结果表明, As(Ⅲ)和Cu(Ⅱ)离子被Fe还原为单质As和Cu后, As、Cu进一步结合成Cu₅As₂等金属间化合物, 从而促进As(Ⅲ)沉淀反应的发生, 且无AsH3生成。在反应时间40min、铁粉过量系数1.2、溶液初始pH=0.0、温度40 ℃、Cu/As摩尔比1.0条件下, As在气、液、固三相中的分配比分别为0、20.7%和79.3%, 沉砷率为79.3%。     

基于AMESim的液压马达加载系统研究

液压马达作为液压系统的执行元件在工程机械上广泛应用,针对液压马达加载工况下的输出特性,利用Simulink和AMESim软件对系统进行联合仿真建模,并对系统的运行状态、控制性能、回收性能进行研究,对液压马达加载系统的设计和改进具有重要的参考意义。     

Physicochemical characteristics,antioxidant capacity and thermodynamic properties of purple-fleshed potatos dried by radio frequency energy

Abstract

The impacts of using radio frequency (RF) energy to dry purple-fleshed potatoes were investigated and compared to infrared radiation (IR) and microwave (MW) drying techniques. The gelatinization rate, color, flavor, morphological, and structural characteristics, thermodynamic properties, as well as antioxidant capacity were examined. The results indicated that the drying time of RF (70?min) and MW (21?min) were shorter than IR (105?min). The gelatinization ratio of MW, RF, and IR were 94.4?±?2.0, 88.3?±?1.4, and 64.5?±?1.1%, respectively. The degree of crystallization of purple-fleshed potato powder decreased with all three drying methods. RF-dried potatoes were able to retain higher polyphenols (loss rate: 4.3%), total anthocyanin (3.7%), and total flavonoid content (35.1%), whereas IR showed the lowest retention. The content of polyphenols also decreased significantly. Furthermore, after RF heating, the scavenging of free radicals was higher compared to MW and IR.     

除尘器新型褶式滤筒的结构优化及系列化设计

以新型褶式滤筒为研究对象,选取滤筒褶数N_2、褶夹角θ、褶高h、过滤风速v为影响因子,除尘器压力损失为响应值,基于响应曲面法分析影响因子对压力损失的影响,建立滤筒除尘器压力损失的预测模型并得到滤筒褶皱结构最优参数。以滤筒内径D、筒体高度D_1为标准尺寸,依据相关国家标准设计滤筒筒体部分;以锥体高度D_2、锥体上圆直径D_3为系列尺寸,利用尺寸变化法设计锥体部分;通过Access软件建立滤筒产品数据库。结果表明:当θ=5.2°,N_2=50,v=0.01 m/s,h=0.035 m时,除尘器压力损失最低;当D_1=1 000 mm,D=320 mm时,D_2和D_3最佳值分别为600,130 mm,故采用D_2/D_1=0.6,D_3/D=0.4的比值设计相应滤筒锥体系列。     

轨腰仿生自分层防腐梯度涂料合成及影响因素和结构探究

目的仿荷藕结构及功能,制备一种自分层防腐涂料。方法合成聚氨酯改性环氧树脂(PU/EP)及氟硅改性丙烯酸树脂(氟硅改性PAA),将两种树脂共混形成自分层涂料。通过铅笔硬度测试、机械性能测试、接触角测试、耐老化测试、划格法附着力测试、电化学阻抗测试等,分别评价两种树脂比例、混合溶剂比例对涂膜自分层行为及性能的影响,并通过SEM-EDS、红外光谱等表征技术分析涂膜分层后的结构。结果当PU/EP∶氟硅改性PAA=1∶1时,接触角达到96.0°,柔韧性为0.5 mm,耐冲击为50 cm,附着力等级为1,失光率降至19%;乙酸丁酯(NBAC)∶正丁醇(NBA)=4∶6时,涂膜分层情况良好,接触角达到107.7°,浸泡水中48 h耐水性无变化,失光率降至17%。SEM-EDS、红外光谱分析表明,自分层涂膜上层为氟硅改性PAA、底层为PU/EP,中间存在过渡涂层,过渡层两种树脂中的─COOH、─OH、环氧基发生反应,使整个涂层更具稳定性。经由EIS分析,在3.5%NaCl溶液中浸泡40天后,腐蚀介质没有渗透涂膜到达基底金属界面。结论制备的轨腰仿生自分层涂膜的机械性能、附着力、疏水性、耐老化、防腐蚀性能优异,涂膜结构稳定。