Techno-economic analysis for rustic electrification in Egypt using multi-source renewable energy based on PV/ wind/ FC

A technical-economic investigation based on mathematical modeling, simulation, and optimization approach is employed in this research to assemble an island combined renewable energy systems (CRES) consists of solar PV/Wind/Fuel Cell (FC) of a small-scale countryside area in Egypt. The intent of the proposed island CRES is to boost the share of renewable energy in the energy mix and to study the possibility of using fuel cells as a storage/backup system instead of using battery banks.Three combinations of CRES are presented in this research to select the most optimum one. The combinations of the hybrid systems are PV/FC, PV/WT/FC, and WT/FC. The performance and the total cost of the suggested CRES were optimized using Firefly Algorithm (FA). The results obtained from the FA are compared with those obtained from the Shuffled Frog Leaping Algorithm (SFLA) and the particle swarm optimization (PSO).The selected case study area with latitude and longitude of (29.0214 N, 30.8714 E) is identified for economic viability in this work.The simulation outcomes show that the solar PV/Wind/Fuel Cell combination incorporated with an electrolyzer for hydrogen production grants the excellent performance. The proposed system is economically viable with a levelized cost of energy of 0.47 $/kWh.     

换能器结构参数对聚合物超声塑化黏弹生热的影响

为研究超声换能器结构参数对聚合物超声塑化过程黏弹性生热的影响，首先确定超声黏弹性生热系统的组成，进行纵振超声换能器结构设计；然后分析超声黏弹性生热过程及超声黏弹性生热原理；最后采用单一变量法分析超声换能器的主要结构参数对其纵振频率及工具头前端质点最大振幅的影响，将其实际输出的纵振激励加载于熔融聚合物，研究其结构参数对聚合物超声黏弹性生热过程及达到聚合物玻璃化转变温度所用时间的影响。结果表明，随纵振激励作用时间的增加，聚合物温度非线性升高；放大比对聚合物温度变化影响最大，前盖板厚度和工具头长度次之，影响最小的是变幅杆长度。     

生物可降解PCL/PLA开孔发泡材料制备及吸油性能

以聚己内酯（PCL）为基体，添加不同含量聚乳酸（PLA）熔融共混制备具有不同分散相形态的PCL/PLA共混物，利用超临界二氧化碳（scCO₂）微孔发泡工艺制备不同发泡倍率和开孔率的PCL/PLA多孔材料用于吸油应用。针对边长3 mm正方体样品溶解度实验发现100 min后CO₂在PCL中已达到饱和吸附状态。PLA分散相含量的增加显著增大了PCL/PLA共混物泡孔密度，并使共混泡孔尺寸减小且分布更加均匀；发泡温度升高6℃，泡孔尺寸增大50%，发泡倍率增大38%，开孔率减小了20%。PCL/PLA开孔材料具有明显的亲油疏水性，发泡倍率越高，疏水性越好；针对花生油和硅油的吸油实验发现材料吸油率与发泡倍率和开孔率整体呈正比，实际吸油量高于理论计算值，10次循环吸油测试后样品吸油率仅降低8.5%，材料吸油量与油品特性黏度关系不大。     

Joining ZTA ceramic by using Dy2O3-Al2O3-SiO2 glass ceramic filler

In this paper, a novel Dy₂O₃-Al₂O₃-SiO₂ (DAS) glass ceramic was designed and prepared for joining zirconia toughened alumina (ZTA) ceramic. The crystallization, thermal expansion behavior and wetting behavior of the DAS glass filler were studied. The effect of cooling rate and joining temperature on the microstructure and flexural strength of joints was investigated. The results show that slow cooling rate (15 °C/min) leads to crystallization of brazing seam, which causes the formation of pores in the joints due to the large density difference between the glass and the crystalline phases. The dissolution of ZrO₂ from ZTA substrate into the filler during joining process improves the mismatch of the coefficient of thermal expansion (CTE) between the brazing seam and substrate. The maximum flexural strength of 535 MPa is obtained when the joining temperature and cooling rate are 1475 °C and 50 °C/min, respectively.     

超声滚压参数对18CrNiMo7-6齿轮钢表面性能的影响

目的研究在不同加工参数下,对18CrNiMo7-6齿轮钢进行超声滚压加工后表层质量的变化,并得出其显著性顺序。建立表面粗糙度的解析模型,研究进给量、滚压次数和初始表面粗糙度对表面质量的影响,并与试验结果作对比。方法采用车刀将固定在车床卡盘上的18CrNiMo7-6齿轮钢棒状材料的端面进行精车后,采用超声滚压试验装置对精车后端面进行加工处理。采用三维形貌测量仪等专用设备,对加工完成后的试样表面表面粗糙度、表层显微硬度、表面二维形貌和表层残余应力等进行检测,然后利用正交试验,寻找对试样表面粗糙度影响的显著性因素,建立表面粗糙度的解析模型,对比试验数据和解析模型数据,研究超声滚压对表面粗糙度、表面二维形貌、表层显微硬度和表层残余应力的影响。结果得到的显著性顺序为进给量、主轴转速、次数、振幅、静压力,并且前述给出的粗糙度解析模型可以较好地预测超声滚压后的表面粗糙度,计算得到的理论数据与试验数据较为接近。试样表面的粗糙度Ra由车削加工的3.003μm减小为0.468μm,齿轮钢表层形成了明显的加工硬化层,其深度约为260μm;表层显微硬度从未处理的360.9HV升至417.6HV,比率为15.7%;表层内形成了勺形分布的残余应力,在距离表层60μm处,最大残余压应力形成,为–790.97 MPa,残余压应力层深度达到了800μm。结论超声滚压加工可以显著提高18CrNiMo7-6齿轮钢试样的表面性能,其中以滚压进给量的影响最为显著。     

Early flame propagation of hydrogen enriched methane-air mixtures at quasi laminar conditions in a rapid compression expansion machine

The temporal evolution of the kinematic properties of hydrogen enriched, lean premixed methane-air flames was studied experimentally in a rapid compression expansion machine (RCEM) during transient operation. Schlieren imaging was used to capture the flame front propagation, while the temporally evolving flow field was simultaneously acquired by particle image velocimetry (PIV). A statistical analysis based on probability density functions (PDFs) of non-dimensional formulations of the flame curvature, stretch rate and displacement speed was performed to study the effect of the onset of flame instabilities on the aerodynamic characteristics of the propagating flame kernel. It was found that initial perturbations stemming from the presence of the spark plug electrodes and from the gas expansion led to the formation of large scale cusps related to the hydrodynamic instability, which is manifested by a notable negative skewness of the curvature PDF, validating recent numerical findings. Under the influence of thermal-diffusive effects, small scale cellular structures develop along the flame front beyond a certain radius, with their appearance shifting to earlier times with increasing hydrogen content or for leaner mixtures. The increasing width of the normalized curvature and stretch rate PDFs is proposed as an indicator for the onset of this type of instability. The adopted methodology allows to track the self-acceleration of the propagating flame front effecting from hydrogen enrichment of methane. The findings of this study provide valuable physical insight and aid in the development of more accurate models, capable of capturing these complex phenomena.     

被动湍流控制圆柱驰振能量收集的等效电路研究

为更好的预测驰振压电能量收获机的性能,首先建立了等效电路仿真模型(ECM)并通过实验验证,最大误差不超过10%。采用该方法分析了被动湍流控制(PTC)下圆柱驰振压电能量收集的仿真模型,且该方法可将驰振能量转化系统的质量-弹簧-阻尼(M-C-K)控制方程中各参数用等效电路的电子元件来表示,从而可以分析过往仿真手段所不能解决的直流电路耦合问题。其次,从能量收集效率角度分析了交流-直流等效电路中临界风速(Ucr)随外接载荷的变化规律,及输出电压与功率随不同风速和外界载荷的变化规律。结果表明,交流电路中Ucr随载荷的增大先增大后减小,直流电路中Ucr随载荷的增大逐渐减小。当风速达到Ucr的最大值时,驰振在任一电阻下均会发生。U≥Ucr时,驰振出现锁定现象,输出电压和功率均随着风速的增大而增大。当风速过大时,增长率有减小趋势。输出电压均随着电阻的增大而增大,功率随电阻的增大先增大后减小。相比于交流电路,直流电路的最佳负载由1.1 MΩ提高到2.0 MΩ,同时功率峰值从0.08 mW降低到0.04 mW。     

Effect of Ti content on the microstructure and mechanical properties of laser clad Ti/B4C/dr40-based composite coatings on shaft parts surface

As a transmission part, the service life of the shaft parts directly affects the machining efficiency and economic benefit, and requires higher surface hardness and wear resistance. In this study, the Ti/B₄C/dr40 composite powder was cladded on the shaft part surface via laser cladding to improve the microhardness and wear resistance. The microstructure evolution and phase structure were analyzed to reveal the strengthening mechanism of Ti and B₄C on dr40 coating. The Ti/B₄C/dr40 composite coating with low defects and good interface metallurgical bonding quality between coating and substrate was prepared on the 45# steel shaft part. The results show that the main phase in the Ti/B₄C/dr40 composite coating is TiC, TiB₂, Cr₂C₃, (Ti, Cr) C, (Ti, Cr, Fe, Ni) (C, B). With the addition content of Ti increasing, the grain densifies, the sieve-reticular structure and small strip phase at grain boundary and intergranular area change as massive phase. Moreover, the microhardness improves up to 2.05 times than that of dr40 coating. The in-situ synthesis of carbides and borides are evenly distributed in the coating, which improves the deformation resistance of the coating. In addition, the precipitation and solid solution strengthening caused by reinforcement phase also enhanced matrix strength for supporting reinforcement phases, improving the coating wear resistance.     

独立焦化干熄炉效率分析与改良措施

立足于独立焦化厂的干熄焦余热发电系统,为提高余热回收质量,采用热平衡分析法与火用平衡分析法对干熄炉系统的余热回收效率进行了计算与分析。干熄炉系统实际工况下的热效率与火用效率分别为79.59%和84.81%,低于设计工况的81.75%和89.06%。实际工况下干熄炉内部换热火用损失为9.88%,高于设计工况下的5.46%。分析表明焦炭烧损率是影响干熄炉系统火用效率的主要因素,干熄炉内部换热火用损失降低了干熄炉余热回收效率。优化循环气体的成分、含量和流速是提高干熄炉系统能量回收效率的主要措施。