等离子枪体喷嘴结构和尺寸对电弧能量的影响

为了研究等离子枪体喷嘴结构和尺寸对电弧能量特征的影响,建立了等离子电弧的数学模型,并采用计算流体动力学（CFD）软件求解了等离子流体质量、动量及能量守恒方程和麦克斯韦方程组.通过对等离子枪体的电弧模型进行求解,得到了等离子电弧沿轴向的温度和速度分布.在此基础上研究了喷嘴通道长度、喷嘴直径和喷嘴压缩角对等离子枪体电弧的影响.结果表明：喷嘴通道长度的增加对等离子电弧的压缩效果影响较小;喷嘴孔径的减小对电弧的压缩效果则很明显.当通道比为1~1.2时,电弧温度和流动速度比较稳定,对阳极表面压力较小,对焊接成形有利.     

单螺杆压缩机星轮夹具的设计与分析

分析并设计了单螺杆压缩机星轮的夹具,应用三维建模软件建立了星轮夹具的三维实体模型,并利用有限元分析软件对不同厚度的夹具在工作过程中产生的位移变化进行了分析及比较.最终确定了夹具的最佳厚度为11.5 mm或12.5 mm.     

激光沉积制备钛基梯度耐磨涂层组织和性能研究

为了提高Ti6Al4V钛合金的高温耐磨特性,在Ti6Al4V钛合金表面利用激光沉积制造原位生成TiC颗粒增强相的方法制备了钛基梯度涂层。观察了耐磨梯度涂层的微观组织,测量了涂层和Ti6Al4V基材在500℃条件下的摩擦磨损性能及其显微硬度,并对涂层的强化机制和磨损机理进行了分析。结果表明,原位自生的TiC颗粒增强相均匀弥散分布在基体中,从基材到涂层顶部分别呈现粗大树枝晶、较大的颗粒状晶体、相对细小的颗粒状晶体形态。显微硬度分析显示涂层硬度保持在400～450HV之间,由基材到表层呈梯度上升趋势。涂层表现出较好的高温耐磨特性,和基材的磨损体积比为2.86。TiC颗粒的弥散分布强化和激光沉积基体组织的细晶强化是显微硬度和高温耐磨性提高的主要原因。     

Geometric structures and hydrogen storage properties of M2B7 (M=Be,Mg, Ca) clusters

Based on the density functional theory, we investigate the electronic properties of the clusters M₂B₇ (M = Be, Mg, Ca) and their hydrogen storage properties systematically in this paper. Extensive global search results show that the global minimal structures of the three systems (Be₂B₇, Mg₂B₇ and Ca₂B₇) are heptagonal biconical structure, and the two alkaline earth metals are located at the top of the biconical. Chemical bonding analyses show that M₂B₇ clusters have 6σ and 6π delocalized electrons, which are doubly aromatic. At the wB97XD level, the three systems have good hydrogen storage capabilities. The hydrogen storage density of Be₂B₇ is as high as 23.03 wt%, while Mg₂B₇ and Ca₂B₇ also far exceed the hydrogen storage target set by the U.S. Department of Energy in 2017. Their average adsorption energies of H₂ molecules all ranged from 0.1 eV/H₂ to 0.48 eV/H₂, which is fall in between physisorption and chemisorption. Extensive Born Oppenheimer molecular dynamics (BOMD) simulations show that the H₂ molecules of the three systems can be completely released at a certain temperature. Therefore, M₂B₇ systems can achieve reversible adsorption of H₂ molecules at normal temperature and pressure. It can be seen that the B₇ clusters modified by alkaline earth metals may become a promising new nano-hydrogen storage material.     

Effect of changing injection pressure on Mahua oil and biodiesel combustion with CeO2 nanoparticle blend on CI engine performance and emission characteristics

Alternative fuels have sparked a lot of interest as oil deposits have decreased and environmental concerns have grown. Biodiesel is an alternative fuel that is being researched as a possible replacement for fossil fuels. In the current investigation, the combustion performance, and emission characteristics of CI(Compression Ignition) engine were examined by changing the fuel injection pressure (180, 200, 220 and 240 bar). The biodiesel (B20) used in this analysis was obtained from Mahua oil at 20% v/v blended with neat diesel (20% Mahua Biodiesel + 80% Diesel). CeO₂(Cerium Oxide) nanoparticles were introduced to the B20 fuel at four distinct concentrations are 25, 50, 75, and 100 ppm. Performance characteristics such as BTE(Brake Thermal Efficiency) and BSFC(Brake Specific Fuel Consumption) were inferior to diesel, at 240 bar B20 with 25 ppm CeO₂ indicated 1.9% increased BTE and 3.8% reduced BSFC compared B20 and 6% lower EGT (Exhaust Gas Temperature) compared diesel. At 200 bar, fuel samples indicated slightly higher In-Cylinder pressure and lower HRR (Heat release rate) compared to diesel. At 200 bar FIP(Fuel Injection Pressure), HC(Hydro Carbon) and CO(Carbon Monoxide) emissions were reduced significantly compared to diesel. The largest reduction in smoke opacity and NOx(Nitrous Oxide) emissions were observed at 240 bar with 75 ppm dosage, but CO₂(Carbon Dioxide) emissions were higher at 220 bar.     

修井机车架有限元分析

根据修井机使用的环境、配套设备的尺寸要求及交通运输车辆国标对修井机车体进行了整体设计,包括汽车型式、主要尺寸和参数的设计。利用SolidWorks三维建模软件建立车架的仿真模型。根据平衡悬架的性能,建立了平衡悬架的三种模型并分析了三种模型的瞬态动响应特性,找到最符合平衡悬架特性的模型。应用有限元分析软件ANSYS对车架进行简化并与平衡悬架进行结构静力学联合仿真,校核设计的车架是否符合修井机的使用要求。     

螺杆转子盘铣刀铣削表面粗糙度预测

螺杆转子主要应用在压缩机、螺杆泵等设备中,其表面质量对使用性能及工作寿命起到关键性作用。工艺参数为影响螺杆转子表面粗糙度的主要因素之一。为了探究工艺参数对螺旋曲面铣削表面质量的影响规律,设计转子铣削实验,获取预测及实验对比样本。利用改进的北方苍鹰搜索算法(INGO)对BP神经网络的初始权值和阈值进行优化,以便提高铣削后的多头螺杆转子表面粗糙度的预测精度。通过实验结果验证所提出算法的预测精度。结果表明,提出的预测模型在平均训练精度及预测精度等方面均优于GRU神经网络及CNN-GRU神经网络模型,其中平均训练精度及预测精度分别约为94.502%和95.523%。故提出的算法具有较高的预测精度,可为合理选择螺杆转子铣削加工的工艺参数提供理论依据。     

The effects of BaTiO3 on the handleability and mechanical strength of the prepared piezoelectric calcium phosphate silicate for bone tissue engineering

Natural bone is a piezoelectric material that can generate electrical signals when subjected to an external force. Although many studies have attempted to develop piezoelectric biomaterials for bone regeneration, post-treatment steps, such as sintering, are always needed. In this study, we prepared an injectable and piezoelectric bone substitute based on nanosized BaTiO₃ (nBT)-added calcium phosphate silicate (CPS). The impacts of nBT on the CPS handleability and mechanical strength were characterized, and show that adding nBT could improve the CPS handleability but affect the CPS mechanical strength in a concentration-dependent manner (from 25.3 ± 1.0 MPa for 10BC to 13.5 ± 1.0 MPa for 40BC). In addition, our approach could fabricate a piezoelectric bone substitute with comparable piezoelectricity to the native bone without any post-treatment. The in vitro analyses demonstrated that nBT/CPS was biocompatible and could promote osteoblast differentiation. In conclusion, our results strongly indicate that the injectable formulation based on nBT/CPS can be a promising candidate in bone tissue engineering, and further research is needed to investigate the biomaterial's performance in bone defect animal models.     

Optimal planning for industrial park-integrated energy system with hydrogen energy industry chain

Establishing an industrial park-integrated energy system (IN-IES) is an effective way to reduce carbon emission, reduce energy supply cost and improve system flexibility. However, the modeling of hydrogen storage in traditional IN-IES is relatively rough. In order to solve this problem, an IN-IES with hydrogen energy industry chain (HEIC) is proposed in this paper. Hydrogen production, transportation, and storage technologies are applied in HEIC. Firstly, a novel long-term hydrogen storage model considering different time steps is presented. Secondly, hydrogen compressor models considering different pressure ratios are further employed. On this basis, the impact of the HEIC on the planning and operation results of IN-IES is studied. Finally, the superiority and the effectiveness of the proposed model and planning method are verified by simulation cases.