Preparation and property of seal coating for gas turbine compressor

Double-layer structure of seal coating which consisted of a Ni5Al bond coating and a Ni25 graphite top coating were prepared on steel substrate of gas turbine compressor cylinder block.Bond coating was prepared by atmospheric plasma spraying and top coating was prepared by flame spraying.The microstructure,mechanical properties and abradability of the coating were characterized by scanning elec-tron microscope(SEM),hardness tester,universal testing machine,thermal shock testing machine and abradability testing machine.The res-ults show that the overall spraying structure of the seal coating is uniform,the nickel metal phase is the skeleton supporting the entire coat-ing,and the coating is well bonded without separation.The seal coating has a bonding strength of not less than 7.7 MPa,excellent thermal stability,and thermal shock resistance cycle numbers at 500℃more than 50;the scratch length,deepest invasion depth and wear amount of the coating increase with rise of test temperature,with almost no coating adhesion,indicating that the seal coating has excellent abradability.

Decorating ketjen black with ultra-small Mo_(2)C nanoparticles to enhance polysulfides chemisorption and redox kinetics for lithium-sulfur batteries

The low sulfur utilization and fast capacity fading resulting from the sluggish redox reaction and abominable polysulfides shuttle greatly hinder the practical applications of lithium-sulfur(Li-S) batteries.Herein, we develop a facile "in-situ growth" method to decorate ultra-small Mo2 C nanoparticles(USMo2 C) on the surface of Ketjen Black(KB) to functionalize the commercial polypropylene(PP) separators,which can accelerate the redox kinetics of lithium polysulfides conversion and effectively increase the utilization of sulfur for Li-S batteries. Importantly, the US-Mo2 C nanoparticles have abundant sites for chemical adsorption towards polysulfides and the conductive carbon networks of KB have cross-linked pore channels, which can promote electron transport and provide physical barrier and volume expansion space for polysulfides. Due to the combined effects of the US-Mo2 C and KB, Li-S cells employing the multifunctional PP separators modified with KB/US-Mo2 C composite(KB/US-Mo2 C@PP) exhibit a high specific capacity(1212.8 mAh g^(-1) at 0.2 C), and maintain a reversible capacity of 1053.3 m Ah g^(-1) after 100 cycles.More importantly, the KB/US-Mo2 C@PP cells with higher sulfur mass loading of 4.9 mg cm^(-2) have superb areal capacity of 2.3 mAh cm^(-2). This work offers a novel and promising perspective for high-performance Li-S batteries from both the shuttle effect and the complex polysulfides conversion.

Ultra-fast phosphating synthesis of metastable crystalline phase-controllable ultra-small MPX/CNT(M = Pd, Pt, Ru) for polyalcohol electrooxidation

A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small(<5 nm)noble metal phosphides(MPX/CNT,M=Pd,Pt,Ru)which are successfully produced in just 75 s for the first time.The catalytic performance of the catalysts can be optimized by controlling the nanomaterials as the metastable crystalline phases.By altering the phosphorus source under the same conditions,the hexagonal structured Pd_(7)P_(3)(NaH_(2)PO_(2).H_(2)O as P source)and monoclinic structured Pd_(6)P(Na_(4)P_(2)O_(7) as P source)can be prepared successfully.Both of them exhibit excellent polyol oxidation performance in alkaline media.Monoclinic Pd_(6)P/CNT and hexagonal Pd_(7)P_(3)/CNT have large ECSA which are confirmed as 82.1 m2 g^(-1)and 86.2 m2 g^(-1),respectively.Hexagonal Pd_(7)P_(3)/CNT has the highest mass activity of 6.14 A mgPd^(-1)(3.21 A mgPd^(-1)for Pd_(6)P/CNT)for GOR,which far exceeded Pt/C(2.81 A mgPt^(-1)).Meanwhile,the mass activity of monoclinic Pt_(5)P_(2)/CNT for EGOR achieved 12.4 A mg_(Pt)^(-1),which far exceeded Pt/C(6.8 A mg_(Pt)^(-1)).The stability test proved that the activity decay of these catalysts was negligible after the 12-hour durability test.Meanwhile,they have excellent CO anti-poisoning abilities.

Graphene-supported ultra-small Co_3O_4 nanoparticles for high-performance supercapacitors

Ultra-small Co_3O_4 nanoparticles/graphene hybrid material had been synthesized by a facile hydrothermal route and consequent calcination process.The as-obtained ultra-small Co_3O_4 nanoparticles with their sizes of 5–8 nm are tightly anchored on the surface of graphene(GNS).Benefiting from the ultra-small size of Co_3O_4 nanoparticles,the high interconnectivity of hybrid material as well as the high conductive networks constructed by GNS,which can provide a fast and efficient transportation of electron and electrolyte ions for the overall electrode,the as-prepared hybrid material exhibits a high specific capacitance of 462 F·g^(-1) at 5 m V·s^(-1) compared with pure Co_3O_4(193 F·g^(-1)),and retained 88.2% of its initial capacitance after 2000 cycles,indicating a promising electrode material for supercapacitors.

Phytic acid-derived fabrication of ultra-small MoP nanoparticles for efficient CO methanation: Effects of P/Mo ratios

Molybdenum phosphide(MoP) catalyst has been widely applied in hydrogenation reactions, while the preparation of unsupported MoP catalysts with ultra-small size and large specific surface area(SBET) is still challenging. Herein, we have provided a facile method for preparing a series of MoP-x(x=P/Mo ratios ranging from 1 to 5) catalysts by pyrolyzing phytic acid(PA)-derived Mo complexes in a H2 atmosphere. The physicochemical properties and the catalytic activity of MoP catalysts were investigated. The results showed that the obtained MoP-5 catalyst had the largest SBETand exhibited ultra-small nanoparticle diameter of 3.6 nm, which ascribed to the chelation of PA and the confinement of deposited products.As the content of PA increased, the synthetic mechanism of MoP was also affected, which led to the difference in the valence of surface Mo species. The characterization results further confirmed that Moδ+ sites in MoP catalysts are active sites for methanation reaction and its content on the surface of MoP-x catalysts determines the catalytic activity.

Hybrid URANS/LES Method of Flow Fields in Axial-flow Compressor Rotor Rotor

Accurate and efficient prediction of the aerodynamic performance and flow details of axial-flow com-pressors is of great engineering application value for the aerodynamic design and flow control of axial-flow compres-sors.In this work,a delayed detached eddy simulation method is developed and applied to numerically simulate the tur-bulent channel flow and the aerodynamic performance of NASA Rotor 35.Several acceleration techniques including parallel implementation are also used to speed up the iteration convergence.The mean velocity distribution and Reyn-olds stress distribution in the boundary layer of turbulent channel flow and the aerodynamic performance curve of NASA Rotor 35 are predicted.The good agreement between the present delayed detached eddy simulation results and the available direct numerical simulation results or experimental data confirms the effectiveness of the developed meth-od in the accurate and efficient prediction of complex flow in turbomachinery.

涡轮压缩膨胀机的设计与性能分析

随着人们环境保护意识的加强,天然工质制冷剂重新受到研究人员的关注。空气是一种安全且对环境绝对友好的天然制冷剂,未来,压缩空气制冷循环有望成为传统蒸气压缩制冷循环的潜在替代品。压缩膨胀机作为压缩空气制冷的核心部件,其工作效率对机组性能有直接影响。为了设计出能够配合膨胀机高效工作的离心压缩机,需要对传统的设计方法进行一些修正。本文将质量、动量、能量守恒与射流尾迹区理论相结合,并将传统的离心压缩机相关参数推广到较低压力的范围中,提出了一种与现有的涡轮膨胀机相匹配的离心压缩机几何参数的设计方法。使用该方法为现有的膨胀机设计了对应的离心压缩机,并利用其他学者分析过的离心压缩机模型对该方法进行验证,利用计算流体力学方法(CFD)对压缩膨胀机变工况下的工作性能及对膨胀功的利用率进行模拟分析。按本方法设计的离心压缩机在设计工况下能够以高于92%的效率利用膨胀机的输出功。在变工况条件下能够以高于88%的效率利用膨胀机的输出功,并且在设计质量流量附近能够顺利运行。

离心式压气机变工况模拟及轴向力变化机理分析

在相继增压系统切换过程中增压器轴向力的变化会严重影响其稳定性,以Garrett TBP4增压器的压气机端为研究对象,建立了压气机全流道计算域并划分多面体网格,设计7个工况,利用CFD研究了相继增压系统切换过程中的切换时间、切换转速、切换出口压力变化对压气机轴向力的影响规律,同时结合内部流场分析轴向力变化机理。结果表明:切换时间主要影响轴向力的突增时刻,切换转速幅值主要影响最终轴向力的大小,切换出口压力幅值主要影响轴向力突增与否;叶片轴向力受流场影响最大。

车用柴油机高压比宽流量增压器研制

目的 对于单级高压比宽流量增压器,为适应发动机强化指标,进行一系列的改进设计。方法 利用仿真设计与试验相结合的方法,对高海拔环境应用增压器进行改进设计。通过理论推导,确定压气机及涡轮的气动性能优化设计方法,开展高稳定裕度转子轴承系统设计方法研究与验证。结果 匹配高压比宽流量增压器的发动机与原机相比,高原功率恢复了17%,发动机排气温度降低了7%,增压器转速降低了13%。结论 在原机的基础上设计了压比为4.6的宽流量高性能涡轮增压器,成功实现了高压比宽流量增压器的设计,满足了发动机平原、高原不同环境的运行需求。

直线压缩机及关键技术研究进展

介绍了小型低温制冷机用直线压缩机的结构和动力学理论,结合国内外近20年来的文献和报道,总结了国内外主要研究单位的直线压缩机研究进展。对影响直线压缩机的关键因素如磁路设计、支撑结构、间隙密封技术进行了总结,最后指出当前小型低温制冷机用直线压缩机的未来研究趋势。

双螺杆压缩机工作性能测试实验平台搭建及教学应用

为提升“过程流体机械”实验教学的高阶性、创新性、挑战度,设计开发了双螺杆压缩机工作性能测试实验平台。该平台可实现工作性能测试、示功(p-V)图绘制等常规实验,并支持开展变工况调节特性分析以及啮合副型面优化设计验证等研究性实验。平台硬件部分根据啮合副型面特征设计了传感器布置方案;软件部分基于LabVIEW软件完成在变载工况下绘制p-V图、计算指示功率及分析效率等数据处理功能。该平台应用于实验教学可为培养学生的工程实践创新能力提供保障。

基于驻留时间控制的压气机叶片前缘砂带磨削研究

提出了一种面向叶片前缘廓形精准控制的机器人砂带磨削加工方法.以轴流压气机叶片为研究对象,结合半赫兹接触理论和有限元仿真获取了柔性磨具和叶片前缘的接触区域内的应力分布,基于Preston方程求解材料去除函数.遍历刀位点对控制点的磨削深度,建立全局材料去除矩阵,搭建驻留时间求解非线性方程组.采用带有阻尼因子的Tikhonov正则化消除大型稀疏病态矩阵对求解精度波动的影响,将所求驻留时间转换为对应刀位点的进给速度,生成机器人加工代码.磨削试验结果表明,基于驻留时间控制的机器人砂带磨削方法能够实现给定允差范围内叶片前缘廓形的精准加工,型面误差可以控制在0.02mm以内.

光学舱推进剂补加过程的热分析仿真与试验研究

推进剂补加是确保光学舱在轨长寿命工作的重要功能,补加过程面临的热环境条件比以往任务恶劣,全过程热控制十分必要。针对光学舱推进剂补加过程的复杂传热新问题,建立包含压气机、液冷模块和环路热管等部件的光学舱平台集成热数学模型,进行热分析仿真研究,并开展系统级热试验。对比高温和低温2种补加条件的瞬态热分析和热试验结果,研究传热关系和温度变化规律;针对热试验中垂直热管因重力因素从不运行至运行的瞬态过程,提出一种变热导率仿真方法;提出高温补加优化设计方案并进行在轨预示。结果表明:瞬态仿真结果与试验结果吻合良好,验证了热分析方法和仿真模型的准确性和有效性;在轨补加采用压气机本体预热并启动2套环路热管,压气机的最高温度≤34.1℃,预热总功耗50 Wh,满足指标要求。研究结果对于光学舱停靠空间站期间的推进剂补加流程设计具有一定参考价值。

两级液环压缩机内流场及外特性

采用数值模拟与试验相结合的方法,以2SY-6两级液环压缩机为研究对象,对多级液环压缩机在不同工况、不同叶轮宽度比下内流场及性能进行对比分析,结果表明:二级叶轮叶片载荷小于一级叶轮,其排气口区域锯齿形气液交界面较一级叶轮更为光滑.一级叶轮吸气口区域回流强度相对于二级叶轮吸气口区域更强,一级叶轮吸气口区域湍动能明显大于二级叶轮.等外径设计的二级叶轮进出口压缩比远小于一级叶轮,二级叶轮的做功能力小于一级叶轮.由于一级叶轮的进出口压缩比较大且均位于效率极值点的右侧,一级叶轮效率随泵的压缩比增大而逐渐下降,而二级叶轮压缩比范围包含极值点,所以其效率先增后减.液环压缩机随着二级叶轮宽度的增大,其吸气能力越强,各个工况下的流量均逐渐增大.低压缩比工况下的效率随k值减小逐渐增大,高压缩比工况下的效率随k值减小先增后减.随首次级叶轮宽度比k值的减小,二级叶轮的压缩比曲线逐渐向上平移,而一级叶轮的压缩比曲线逐渐向下平移.随泵出口压力的增大,首次级叶轮压缩比的比值曲线下降趋于平缓,k值为2.2时两级叶轮压缩比的比值趋于1.1.

基于Flow Simulation的某发动机涡轮压气机流场与效率分析

涡轮机内部流场对涡轮增压器的性能和效率有着重要影响,采用SolidWorks Flow Simulation模块对某发动机涡轮压气机侧流场和压气效率分析。在六种不同空气体积流量工况下,体积流量为0.29时,压气机效率最高,达到80%左右。模型的建模和流体分析均在SolidWorks环境下,分析效率高,为涡轮增压器设计和优化提供了支撑。

海洋平台振动设备所在区域结构优化设计分析

海洋平台上有很多振动设备如压缩机、泵等,这些设备内部转子的往复运动导致高频振动,对平台结构、杆件的稳定造成影响,长期振动下使平台结构出现疲劳,同时设备振动会产生噪音和震感,对平台上的人员身心健康也造成严重影响。文章基于渤海某平台,相关数据均来源于该平台。通过对该平台在压缩机作用下的振动响应,研究压缩机振动对平台的影响,优化该区域结构设计。

基于功率流有限元法的涡旋压缩机振动特性研究

针对涡旋压缩机内部振动传递路径复杂,采用传统的传递函数法往往不能真实地描述振动产生与传递的本质问题,引入功率流有限元法从能量角度分析振动传递特性,进行涡旋压缩机内部振动产生、传递与空间分布的可视化研究。在分析涡旋压缩机的动力拓扑关系基础上建立激励源,提取与振动响应模型并进行仿真分析;利用实体试验和响应分析结果对比进行模型有效性分析;在验证后的模型上定义8个能量输出面,分析谐波与激励作用下上支撑和下支撑的振动能量传递特性,并且计算节点的功率流矢量确定振源的空间分布。结果表明,涡旋压缩机曲轴在运转到280°时,振动频率在1 000 Hz与1 890 Hz时振动能量传递率较高,上支撑能量分布均匀并集于自身,下支撑能量集中于支脚并向外传递。研究方法和研究成果对于涡旋压缩机振动分布及传递、振动控制和优化设计等方面具有一定借鉴意义。

燃料电池空压机气磁悬浮系统的协同控制研究

针对燃料电池空压机目前存在的驱动和支承问题,提出一种箔片动压轴承和动力磁轴承一体化的气磁悬浮型空压机。基于空压机的结构组成,建立空压机磁悬浮支承力、气悬浮支承力以及空压机转子动力学数学模型;基于燃料电池空压机转子系统动力学模型的状态空间方程,设计抗干扰强的协同控制器,并对它进行了转速、驱动转矩、转子悬浮位移以及电磁调节力等关键物理量的仿真分析。结果表明:协同控制在响应、抗干扰以及鲁棒性方面的控制优于PID控制。基于协同控制和PID控制建立了控制实验平台,并对空压机转子的气磁悬浮进行分析,进一步验证了协同控制具有优良的控制效果和良好的控制性能。

基于数字孪生技术的往复式空气压缩机效率预测方法研究

通过建立往复式空气压缩机数字孪生体模型,实现压缩机效率预测和参数寻优的方法,具有灵活、成本低、通用性好的优势.但是在多变量条件下,传统的基于BP神经网络孪生模型训练时间长、工作量大,寻优过程易陷入局部最优解,不易实现全局最优.针对传统孪生体模型存在的问题,提出了基于CIWOA-BPNN算法的孪生体模型构建方法,通过主成分分析法确定孪生体模型关键指标,在BPNN模型基础之上引入改进的鲸鱼优化算法.研究表明,基于CIWOA-BPNN算法的孪生体模型有效避免了BPNN模型陷入局部最优解.用CIWOA-BPNN算法预测压缩机效率相对误差小于0.6%,决定系数为0.99775,与传统模型相比大幅提升了预测精度.

解决农产品配送“断链”的光伏冷链小车设计

在现有普通农用电动货运三轮车的基础上,通过增加1.3m^(3)保温车厢、600Wp太阳能电池板、4块12V100Ah蓄电池、110W直流压缩机等设备,先计算车厢从35℃降至-10℃所需要的冷量,再综合验证组件与蓄电池满足小车一天的制冷与行驶需求。通过精确的系统匹配及智能温度控制,改造成太阳能智能冷链物流小车,很好的解决了现在冷链物流配送中“最后一公里”空缺的问题,经过测试达到设计要求。本车可直接开到田间地头,有方便快捷、耐用、不付电费、造价低等优势,是现代农业物流冷链运输必不可少的中转设备,实现了农村鲜活农产品采摘−物流中心−用户的无缝对接。