This study presents a thermoelectric conversion system (TCS) for a scramjet engine, based on the supercritical carbon dioxide (SCO2) closed Brayton cycle (CBC). A coupled model is developed, integrating the scramjet engine's combustion chamber, wall cooling channels, and the SCO2 CBC. The system's performance is analyzed under a free-stream Mach number of 7.7, with compressor outlet pressure (pC,out) varying from 17.5 MPa to 30 MPa, while considering the impact of working fluid mass flow rate (m) and recompression split ratio (xRC). The results indicate that there are crossover points in the performance between the regenerative CBC (Reg.CBC) and recompression CBC (Rec.CBC) as pC,out varies. Specifically, when pC,out is below a certain threshold, the Reg.CBC performs better, while the Rec.CBC achieves superior performance when pC,out exceeds this value. Within the parameter range studied, the optimal performance for the Reg.CBC corresponds to a thermal efficiency (7th) of 32.33 %, net power (Pnet) of 492.01 kW, and cooling fuel mass flow rate (mfc) of 0.490 kg/s. The optimal performance for the Rec.CBC corresponds to a 7th of 35.65 %, Pnet of 541.12 kW, and mfc of 0.471 kg/s.
Accurate assessment of the wake effect of wind farm clusters is of great significance for the development of wind power bases, yet there is currently a deficiency in numerical simulation methods with high accuracy and simple modeling. To address this issue, a numerical simulation framework for large wind-farm wakes based on a wind farm parameterization model is proposed, and is then implemented based on the open-source CFD software OpenFOAM. In this framework, a newly proposed wind farm equivalent roughness model is adopted to parameterize wind farms and incorporated into the simulation via the wall stress model. To validate the method, the large-eddy simulation based on the actuator disk model resolving all the turbines in the wind farm is taken as a benchmark. Thirty two cases including spanwise infinite wind farms and finite wind farms with different streamwise turbine spacings, spanwise turbine spacings, wind turbine thrust coefficients, and roughness lengths of ground surface are set to analyze the sensitivity of the framework to different wind farm parameters. Results show that the proposed method predicts the velocity deficit and turbulence intensity downstream of the wind farm accurately. Compared to the classical wake superposition model, the prediction accuracy of the velocity deficit is improved by more than 30 %. Furthermore, without resolving the turbines using fine mesh, the framework shows a high potential to reduce computational costs compared with the turbine-resolved simulation.
有效挖掘故障演化的过程有利于分析和总结故障传播规律.本文提出了基于LSTM-BO模型和SPRT算法,利用SCADA历史数据研究风电机组早期故障演化过程的分析方法.首先使用Pearson相关系数法挖掘SC ADA数据各监测变量之间的映射关系,获得LSTM-BO网络所需的输入—输出关系对;其次是依赖LSTM网络强大的时序特征提取能力,将预处理后的SCADA数据送入LSTM网络进行训练,从而得到相应的正常行为模型;最后,依赖SPRT在序贯测试方面的优势,将各监测变量模型预测值与实际监测值之间的偏差看作序贯测试的对象,并对其测试结果进行滑动窗口观测,以异常点数目占观测窗口宽度的比值为度量指标,得到SCADA数据部分重要监测变量在故障发生前的演化过程.实例分析结果表明,所提方法能够有效提取故障演化的过程,为后续演化规律的分析提供指导.
重力热管以其极佳的传热能力广泛应用于工程领域,而对于单根热管传热性能的提升则能够更好地提高换热设备的效率.本文通过数值模拟方法,分析了重力热管参数变化对其传热特性的影响.结果表明:VOF(Volume of Fluid)模型能够捕捉重力热管内部的蒸发冷凝现象;热管热阻随着充液率或加热功率的增大而减小;在一定范围内,热管热阻随热管内径增大而减小,随冷凝段长度增大而先增大后减小,但冷凝段长度过小会导致气液循环效果变差,因此,在实际设计中应考虑热管传热极限及安全长度比,保证热管的安全运行.
In a high thrust-weight-ratio aero-engine, turbine blades are exposed to extremely high temperature and pressure which sets higher demands in the blade cooling technology. To boost film-cooling effectiveness, an accurate, efficient, and all-sided inspection of film cooling holes is urgently requested to ensure the quality of turbine blades. The tiny size of film-cooling holes adds to extreme difficulties in the inspection process both by contact and non-contact measurement. This paper proposed a non-contact measuring technique to cope with the inspection of turbine blades. A specially designed light-field camera with a small field of view and proper depth of field is applied to resolve a 3D geometry of film cooling holes. The technique uses one light field camera to capture images of the blade surface. 3D light-field reconstruction algoritm is applied and point cloud of the blade is generated. Due to the compactness of the non-contact single light-field imaging system, information inside the holes becomes attainable. By precisely controlling the relative pose of the camera to the blade surface, the device can obtain hole diamter and outlet angle with an accuracy of ± 0.03mm and ±1°17'respectively. The average time consumed for reconstructing one film cooling hole is about 5 seconds.
建立了离心泵用推力滑动轴承的物理模型,编写数值计算程序并对不同结构参数的轴承进行数值仿真分析.通过仿真结果发现,内径为14mm、外径为28mm的轴承最佳扇形瓦块数为6、最佳楔形进口高度为28μm、最佳楔形区域占比为0.4.通过对不同润滑膜厚度的轴承进行数值仿真,发现轴承承载力和摩擦力矩均随着润滑膜厚度的增加而不断减小.在推力滑动轴承设计过程中,需对轴承的结构及润滑膜厚度进行优化设计以达到最佳的性能,以防止出现因承载力不足导致轴承失效的状况,此次仿真结果为轴承设计提供了参考.
民机在降雨环境下的起飞和爬升过程中,雨水和飞行迎角耦合形成的复杂进气畸变对发动机性能有着不可忽视的影响,探究降雨浓度和飞行迎角对发动机风扇性能的影响具有积极意义.以某小型高涵道比涡扇发动机为研究对象,基于两相流原理,利用数值模拟方法研究了不同飞行迎角和大气雨浓度对进气道、风扇级的影响.结果表明,在适航规定要求的大气雨浓度和飞行迎角的共同影响下,飞行迎角增大使得雨滴在风扇各通道内周向分布不均匀,受进气总压畸变影响的通道内雨滴数目减少,非畸变区通道内雨滴数目增加,且迎角越大,雨滴分布越不均匀.雨水没有明显增强受总压畸变影响通道内的流场畸变程度,而是主要恶化总压畸变影响较弱区域的风扇和出口导叶的性能.
The valve gasket for aero-engine is prone to creep under extreme conditions such as high temperature and high pressure. The creep failure of the gasket leads to valve leakage, which seriously threatens the safe and reliable operation of aero-engine. Aiming at the creep failure of FEP gasket in use, a timehardening creep model of valve gasket seal is established. The effects of time, operating pressure, material and structural parameters on the creep and sealing properties of FEP gaskets are analyzed. The results show that the compression rebound rate of gaskets decreases with the increase of time, and small compression rebound rate will decrease the sealing performance. The creep behavior of FEP gasket increases with the increase of operating pressure. Reducing the fillet radius can reduce the probability of shear failure, but also reduce the contact stress. Increasing the height of the boss can reduce the deformation behavior of the gasket, but reduce the contact stress on the sealing surface. When the gasket bevel angle is 85° , the creep property and contact stress of the gasket are higher than those of other sizes. But large bevel angle leads to the gasket unsticking. Replacing the FEP material with the polyimide material can improve the creep resistance of gaskets and the contact stress of sealing surface. Considering the service life and sealing effect of gasket, the material is replaced with polyimide plastic, the fillet radius is 0.20mm, the bevel angle is 85°and the boss height is 0.2mm.
为了提高轴流压缩机内流场气流品质,降低压缩机现场运行产生的噪声,本文提出了一种在压缩机出口下游管道壁面安装降噪结构的方案.根据轴流压缩机噪声特性,利用马大猷教授提出的穿孔板吸声理论,同时考虑切向流及高声强的影响,设计了一种双层穿孔板,采用流管法测试了样件的吸声性能,最后在压缩机现场运行过程中对降噪结构上、下游截面进行了噪声测量.结果表明:降噪结构穿孔板在设计的频率范围内具有良好的吸声性能,其下游截面的噪声明显降低.
流动特性实验是研究轴流压气机气动性能的重要手段,而轴流压气机气动性能测试台是进行压气机试验研究的工具.文章结合国内外轴流压气机试验台的现状,总结了轴流压气机的进气系统、排气系统、驱动系统以及常用流场测量技术,分析了在设计轴流压气机试验台和实验布置时需要考虑的因素,并对轴流压气机试验台的发展趋势进行了展望.
基于国内外涡扇发动机及其部件特性研究结果,本文旨在以双转子高涵道比涡扇发动机E3某型号为研究对象,通过GasTurbTM仿真平台,建立动态部件模型.基于相似理论及模化原理,在核心机工作点匹配约束条件下,对其部件特性进行研究,从而获得航空发动机在非稳定工况下的整机性能和工作特性.研究结果表明:在其他条件一定的情况下,双转子发动机的核心机效率和流量随高低压转子转速的增大而增大,伴随着涡轮前温度的升高,推力逐渐增大,耗油率先增大后减小;高压压气机的增压比偏离设计值的程度对油耗影响较为明显.
用于笔记本电脑的微型高速多翼风机系统,存在风量与风压不能完全匹配而影响笔记本电脑高速运行时的散热效果.本研究采用数值分析与实验研究相结合的方法,在不改变风机其它结构参数的情况下,设计了5种不同上进风口直径的方案,详细分析了不同上进风口结构参数对微型离心风机内部流动特征和气动性能的影响.研究结果表明:上进风口直径对风机的性能影响程度较大,适当增大上进风口直径,能够改善进气条件,提升风机的气动性能.当上进口直径与叶轮内径之比为0.96时,风机的气动性能最优.继续增大上进风口直径,风机进口气流对叶道内的流动的扰动加剧,风机性能有所下降.相比于原型机,采用较优进口结构的风机最大风量提升了4.8％.在1.915m3/h工况下,静压提升19.6％.
本文通过全周非定常三维CFD数值模拟方法研究了进口总压畸变在离心压气机中传播的非定常特性与时空演化过程.结果表明,主叶片在一个流动周期中通过畸变区域的过程是"低速流体团附着、沿伸、脱离",分流叶片为"附着、扩大、消散".畸变区造成的非匀速冲击使叶片承受较大的周期性交变应力,使得主叶片前缘对进口总压畸变引起的流场不均匀性更为敏感;总压畸变对离心叶轮中间叶高以下区域影响较小,但在靠近叶顶区域时,影响叶片压力面的静压分布,使其产生不均匀的压力波动;通过求解绝对坐标系下的时均流线,发现畸变主要影响叶展位置较大区域的流线,靠近叶顶区域的流线偏转程度较大,靠近叶根区域的流线最为均匀.
本文首先采用数值模拟方法开展高速离心压缩机叶轮出口下游背压脉动的流场响应特性研究,分析指出高转速离心叶轮的气动性能波动随着背压脉动频率的增加而增大,但不同背压脉动频率下各时刻的流场分布具有相似结构.然后采用动态模态分解(DMD)方法对背压脉动下非定常流动的模态场进行分析,不同脉动频率下的非定常流场均包含叶轮转频的各阶谐波模态,流场响应的零阶模态为反映平均流场的基本模态,各阶谐波模态均为极限环模态,其它均为近似极限环振荡或衰减模态,流场响应的非定常成分主要由一阶谐波模态贡献.DMD分析结果表明:DMD方法能够对叶轮非定常流场变化特性进行降阶解构及准确预测.
本文以两支点弹性支承的转子系统为研究对象,基于旋转梁理论和有限元理论建立了转子系统动力学模型,在此基础上给出了应变能的计算公式,分别对转子和弹性支承进行了应变能分析,通过数值仿真分析了支点支承刚度、刚度不对称对转子系统的模态振型及相应的应变能分布的影响规律.研究结果表明:1)当支承刚度与转子刚度相近时,支承刚度变化对于转子系统动力特性变化非常敏感,系统模态振型和应变能分布随着支承刚度的增减将会表现出很大的差异.2)转子的应变能系数η可作为区分系统模态振型的重要参数.当η小于20％,转子基本不发生变形,视为刚体振型;在η超过80％时,变形主要发生在转轴上,可视为完全弯曲振型;η在20％～80％的范围,视为转子-支承的耦合振型.本文研究为弹性支承设计以及带弹支的转子系统的结构设计、运行和维护提供理论参考.
提出了一种利用6控制点5阶Bezier多项式对完全对称翼型进行表达的参数化设计方法,并通过6个无量纲的横纵坐标控制系数和翼型最大相对厚度控制翼型型线.采用Fortran语言编写翼型参数化设计程序代码,并与ICEM网格划分和Fluent流场仿真一起集成到Isight自动优化平台,利用多岛遗传算法对相应的目标函数进行求解,实现了完全对称翼型的优化设计.以相对厚度为16％的椭圆翼型为参考,取4°、8°和12°为设计攻角,在Re=2.5×106的条件下,设计得到一款翼型A.与参考翼型对比结果显示,优化翼型A的型线接近菱形,其载荷在x/c?(0.04,0.3)的区域减小,而在x/c?(0.3,0.96)的区域增加,沿弦线方向载荷分布更加均衡.此外,在设计攻角下,优化翼型A的升阻比分别增加了28.56％和17.64％,在非设计攻角下,其气动性能也得到显著提升,印证了构建的优化设计方法的可靠性,为其他复杂可逆翼型的优化设计奠定了良好的理论基础.
In this paper, the numerical simulation method is used to study the flow resistance law of u-shaped channels under rotating conditions based on similarity theory. The study compares three geometric models:real model, completely similar model and incompletely similar model for cooling typical U-shaped channels inside turbine rotating blades. The completely similar model is geometrically 4.8 times magnification of the real model, and the rotation radius ratio of the real model is 5.4 times that of the incomplete similar model. It is found that the friction factor of the completely similar model increases with the rotation number, and the difference varies from 6％to 38％. The friction factor of the model after incomplete similarity amplification decreases with the increase of rotation number, and the difference varies from-2％ to-30％. The friction factor of the laboratory imperfectly similar amplification model combined the effects of the above two laws, and the predicted difference was within 12％. This study provides a theoretical basis for subsequent experiments related to flow resistance.
为准确、定量评估某发动机弹性密封件贴合面的轴向变形,首先建立贴合组件的模型,随后对模型中的各零部件赋予导热系数与材料,施加初始温度、换热系数等边界条件,计算出四种恶劣工况下精确的温度场分布,随后将温度场分布作为输入条件导入结构求解的模型中求解,输入材料的热膨胀系数和弹性模量,施加轴向力载荷时考虑2g的正反方向的过载,分别求出极限情况下的两个大的组件中端面的轴向变形,最后进行求差,得到最大的轴向相对变形量,从而为进一步评估压缩量对弹性密封的影响提供了科学的定量依据.
为研究整体涡旋流畸变对轴流-离心组合式压气机喘振特性的影响,本文采用气腔模型来研究压气机出口的容腔效应,分别模拟了均匀进气以及不同旋流强度的正向及负向整体涡旋流畸变作用下,组合式压气机的喘振过程.研究发现,正向整体涡旋流畸变作用下,离心叶轮进口截面近盘侧存在强度较大、范围较广的正向旋流,一定程度上抑制了叶轮内的流动分离;相反地,负向整体涡旋流畸变作用下,离心叶轮进口截面近盘侧存在强度较大、范围较广的负向旋流,使叶轮内的流动分离加剧甚至引发回流,使得压气机系统进入深度喘振工况.正向整体涡旋流畸变的旋流强度越大,组合式压气机的喘振圈及喘振频率越小;负向整体涡旋流畸变作用下,旋流强度越大,喘振圈越大、喘振频率越高.
如何高效地控制和优化流体管网系统,实现流体管网系统的最优运行状态,是流体管网系统控制优化研究的重点.本文以某管网控制系统中的空气试验系统为例,首先建立精准的流体管网模型,对空气系统进行建模与仿真计算,再通过智能优化的方法驱动仿真模型,寻找最佳试验方案并给出控制策略.最后,结合模糊控制,提升试验系统的智能化和自动化程度.结果表明,本文采用的方式可以对试验工况进行合理排序并给出最优控制策略,结合模糊控制达到精准控制的目的.该方法可以大幅度降低管网系统对人员经验的依赖程度,为管网系统的全面自动化、智能化转型打下坚实的基础.
