Optimal Design and Experimental Verification of Low Radiation Noise of Gearbox

Reducing the radiated noise of a gearbox is a difficult problem in aviation,navigation,machinery,and other fields.Structural improvement is the main means of noise reduction for a gearbox,and it is realized primarily through contribution analysis and structure optimization.However,these approaches have certain limitations.In this study,a low-noise design method for a gearbox that combines the two approaches is proposed,and experimental verification is performed.First,a finite element/boundary element model is established using a single-stage herringbone gearbox.Considering the vibration excitation of the gear system,the radiation noise of a single-stage gearbox is predicted based on the modal acoustic transfer vector(MATV)method.Subsequently,the maximum field point of the radiated noise is determined,and the acoustic transfer vector(ATV)analysis and modal acoustic contribution(MAC)analysis are conducted to determine the region that contributes significantly to the radiated noise of the field point.The optimization region is selected through the panel acoustic contribution(PAC)analysis.Next,to reduce the normal speed in the optimization region,topology optimization is performed.According to the topology optimization results,four different noise reduction structures are added to the gearbox,and the low-noise optimization models are established respectively.Finally,by measuring the radiated noise of the gearbox before and after optimization under a given working condition,the validity of the radiated noise prediction method and the low-noise optimization design method are verified by comparing the simulation and experimental data.A comparison of the four optimization models proves that the noise reduction effect can be achieved only by adding a noise reduction structure to the center of the density nephogram.

Theoretical analysis and experimental research on non-cavitation noise modulation mechanism of underwater counter-rotation propeller

The underwater counter-rotation propeller non-cavitation noise has an obvious mod- ulation characteristic which is due to the interaction of flow and blade. A modulation mecha- nism is presented in this paper. A sound pressure spectrum model is presented to describe its non-cavitation noise with application of generalized acoustic analogy method, the modulation mechanism is expressed with the improvement of sound pressure model. The power spectrum and modulation spectrum are presented by numerical simulation. Theoretical analysis and nu- merical simulation results are verified by the cavitation tunnel experiment. The modulation model of counter-rotation propeller is beneficial to the prediction modulation characteristics and identification of underwater high-speed vehicles.

Theoretical analysis and experimental research on port/starboard discrimination in towed line array

The theoretical analysis and experimental research on Port/Starboard (P/S) discrimination in towed line array are proposed. Two methods resolving the P/S ambiguity with hydrophone triplets are introduced. By processing experimental data, the theoretical analysis is verified. The processing algorithm is extended to broadband signal. The research results show that the method based on optimum beamforming with triplets can be used to remove the port/starboard ambiguity. Also because of the simplicity of the method, it is expected to be implemented in practical towed line array sonar.

Refined modeling and experimental verification of a torque motor for an electro-hydraulic servo valve

The Permanent Magnet Torque Motor(PMTM)is the key electro-mechanical conversion device in an Electro-Hydraulic Servo Valve(EHSV).In this work,a refined model of a PMTM is developed,considering the non-working air-gaps between the upper or lower yoke and the armature,the fringing effect at the limiting holes,and the nonlinear permeability of soft magnetic material.Based on the refined model,the influences of various factors on the calculation accuracy of the magnetic flux at the pole surfaces of the armature and the output torque are investigated.For verifying the validity of the refined model,a Finite Element Analysis(FEA)of the PMTM is conducted,and a test platform is constructed.Compared with existing models,the refined model can better reveal the intrinsic mechanism of the PMTM,and its calculations are more consistent with the FEA results.The experimental results of the armature deflection displacement show that the refined model can accurately describe the output characteristics of the PMTM.

Theoretical modeling and experimental verifications of the single-compressor-driven three-stage Stirling-type pulse tube cryocooler

This paper establishes a theoretical model of the single-compressor-driven (SCD) three-stage Stirlingtype pulse tube cryocooler (SPTC) and conducts experimental verifications. The main differences between the SCD type and the multi-compressor-driven (MCD) crycooler are analyzed, such as the distribution of the input acoustic power in each stage and the optimization of the operating parameters, in which both advantages and difficulties of the former are stressed. The effects of the dynamic temperatures are considered to improve the accuracy of the simulation at very low temperatures, and a specific simulation example aiming at 10 K is given in which quantitative analyses are provided. A SCD threestage SPTC is developed based on the theoretical analyses and with a total input acoustic power of 371.58 W, which reaches a no-load temperature of 8.82 K and can simultaneously achieve the cooling capacities of 2.4 W at 70 K, 0.17 W at 25 K, and 0.05 W at 10 K. The performance of the SCD three-stage SPTC is slightly poorer than that of its MCD counterpart developed in the same laboratory, but the advantages of lightweight and compactness make the former more attractive to practical applications.

落石被动柔性防护网非线性静力设计方法及验证

被动柔性防护网是一种常见的落石灾害防治措施。针对当前落石被动柔性防护网尚无适用的工程化设计方法的现状,以非线性计算过程中结构内能与设计防护能级相等作为加载完成的判别准则,建立了落石被动柔性防护网的非线性静力设计方法。基于LS-DYNA对250~5000 kJ共8种常用能级的被动柔性防护网开展非线性动力分析,明确了冲击力的分布范围及相对大小,形成了适用于不同能级落石被动柔性防护网非线性静力设计的荷载模式。为了有效模拟被动柔性防护网特殊的受力特征,开发了由索单元与受拉弹簧单元组成的非线性耗能单元用于耗能器模拟,开发了内部由多段索单元组成的滑移索单元用于滑移边界以及网环单元模拟。基于对网片冲击试验的反演和3500 kJ被动柔性防护网的设计及足尺冲击试验检验,验证了所提出的落石被动柔性防护网非线性静力设计方法的有效性。

高压喷射注浆桥梁纠偏影响因素显著性分析

采用高压喷射注浆联合应力释放的方法,对已偏移桥梁墩台进行纠偏是一项切实可行的技术措施。为提高桥梁纠偏效率,快速恢复高速铁路正常安全运营,在分析高压喷射注浆桥梁纠偏原理基础上,建立了桥梁纠偏理论模型;基于弹性地基梁理论,推导了桥墩顶部位移计算解析式,分析了影响桥梁纠偏效率的主要因素;通过正交试验设计方法,探讨了桥梁纠偏影响因素的显著性,并以现场典型工程案例进行了验证。结果表明:影响桥梁纠偏效率的主要因素为土体地基系数、超孔隙水压力和注浆施工深度。施作应力释放系统后土体地基系数减小,桥墩日纠偏量由0.42 mm快速增至1.04 mm,增幅为148.8%;注浆压力由20 MPa增至25 MPa,产生的超孔隙水压力增大,桥墩日纠偏量由0.39 mm增至0.86 mm,增幅为118.2%;注浆施工深度由19 m增至24 m,桥墩日纠偏量由0.24 mm增至0.40 mm,增幅为69.5%。土体地基系数对桥梁纠偏效率的影响最显著,其次为高压喷射注浆产生的超孔隙水压力,注浆施工深度的影响最小。研究成果可为提高桥梁纠偏效率提供理论依据。

矿井提升罐笼自发电装置的设计与仿真分析

矿井提升罐笼在煤矿的开采过程中工作环境复杂,在运行中需要对矿井提升系统进行监测、照明和内部监控。但罐笼直接供电的难度大,供电时间短,电池需要频繁的进行更换和检修。针对上述问题,进行了一种矿井提升罐笼自发电装置的研发,该装置能够将矿井提升机系统运行时产生的部分机械能转化为电能,对罐笼顶部的蓄电池充电。在满足罐笼内照明需求和保障罐笼运行时监控用电的要求下,确定方案的可行性并进行三维建模,其次采用ANSYS WORKBENCH对整体装置进行动力学分析及摩擦轮进行各阶模态分析,避免共振影响,然后对摩擦轮聚氨酯外圈进行磨损仿真以确保装置材料强度的可靠性。最后对实验样机进行测试,以此满足罐笼内用电需求,对于提升罐笼内部人员安全具有重要意义。

分叉波导开裂问题结构改进设计

本文针对某雷达天线系统的分叉波导开裂问题提出了三种结构改进方案,对三种结构改进方案进行模态和振动仿真分析,对比三种方案的一阶模态和最大应力值得出该分叉波导的最佳结构改进方案,并试验验证方案的有效性。

基于离心机平台的加速度−温度综合环境试验系统设计

为在现有转臂式结构的离心机平台上拓展温度试验能力,文章提出一种加速度−温度综合环境试验系统的设计方法。针对温度箱内因离心过载和科氏加速度的影响而导致的温度场分布不均匀,采用调整温度箱热源位置和增加风轮风量等手段进行流场干预;通过对温度箱的结构强度仿真及试验验证该系统的工作性能。结果表明:该试验系统可进行加速度为0g~45g、常温~130℃的加速度−温度综合环境试验,监测温度偏差控制在±5℃范围内。以上研究可为加速度−温度综合环境试验系统的设计提供参考。

基于拓扑优化理论下汽车轮毂结构轻量化设计

汽车轮毂结构轻量化设计是在保持轮毂功能和性能不变的前提下,尽可能降低其质量,从而减轻整车重量,提高燃油经济性和行驶性能。该文采用OptiStruct通过对轮毂结构进行建模和网格划分,确定了有限元分析的计算模型。然后,在考虑强度、刚度和质量等多个设计约束条件的基础上,利用OptiStruct进行调整材料分布和形状,充分利用材料的受力特性和结构优势,实现了轮毂质量的有效降低,同时保证了其强度和刚度的需求。通过对优化后的汽车轮毂材料进行静态加载测试、动态加载测试和耐久性测试,验证轮毂在实际使用中的稳定性和可靠性,结果表明,优化设计方案能够满足汽车轮毂在各种工况下的设计要求。该研究为汽车轮毂轻量化设计提供了一种有效的方法和技术支持,在汽车工程领域具有一定的理论和实践意义,为汽车轮毂轻量化设计和工程应用提供了有益的参考和借鉴。

UHPC加固钢筋混凝土梁抗弯承载力试验研究

为研究普通钢筋混凝土梁不同受力区域加固超高性能混凝土(UHPC)后抗弯承载力的变化情况,设计、制作了3根试验梁[未加固钢筋混凝土梁(RC)、受压区UHPC加固梁(UC)和受拉区UHPC加固梁(UT)],采用四点加载法进行抗弯试验,分析加固前后试验梁的破坏模式、荷载-挠度曲线及承载力变化规律。结果表明:试验梁UC和UT相较于RC,刚度和承载力大幅提高,其中承载力分别提高61.2%和96.9%;提出了钢筋混凝土梁受压区、受拉区(考虑纤维贡献)加固UHPC后的抗弯承载力简化计算公式,计算值和试验值误差小于5%,具有较高的计算精度和适用性。

风机过滤单元送风均匀性理论分析及实验研究

分析了造成风机过滤单元风速不均匀的几个结构因素,对常见的风速不均匀度的计算方法进行了对比,探讨了其各自的适用范围,认为采用RSD(相对标准偏差)来评估不均匀性在现阶段是合适的。同时对影响风机过滤单元风速不均匀性的因素进行了理论分析,提出了将风速波动分为低频、中频和高频三种类型,指出滤纸打折形成的中频波动是起主导作用的因素,采样测试时需要基于该频率进行采样才能得到较为稳定的结果。综合考虑测试准确性和测试时间成本,建议10×10的测点数量较为合适。基于以上的测点布置和计算方式,通过实验的方式对一些常见参数对风速不均匀的影响进行了测试研究,发现距出风面的距离对结果有显著影响。

方形硬壳锂离子电池产热性能的实验量化分析

针对方形硬壳锂离子电池的产热行为表征问题,结合理论分析与实验研究提出了一种量化分析新方法——热补偿法。探讨了电池产热性能与荷电状态、工作电流、温度的曲线关系。发现电池的产热性能、温升幅度等均随工作电流的降低和温度的升高而减弱,但放电效率却随之增大;电池生热率与工作电流、温度分别呈二次非线性关系。相比于采用传统Bernardi模型测算电池产热,“热补偿法”精度高达94%,且成本低、易操作,具备市场推广潜力。

Experimental Study of Churning Losses in Swash Plate Axial Piston Pump

The problem of the churning loss in swash plate axial piston machines is investigated through experimental measurement and theoretical analysis. Several works surrounding churning loss in hydraulic components have been proposed in the past, but few have conducted experimental studies and accounted for both dry and wet housing conditions. In this study,a specialized experimental setup is established, which includes a transparent test pump diligently designed for performing various functions of tests. The test pump can work as a real pump without losing any actual features of pump operation. The torque loss in both the dry housing pump and wet housing pump is measured in terms of the shaft speed and its predictive model is also developed analytically. The comparisons between measured and calculated torque loss are presented, showing how speed influences torque loss in both conditions. The advantage/disadvantages of the two cases are summarized. The significance of the test setup is highlighted by verifying the proposed model, which can advance the understanding of energy losses of high speed pumps in future.

Micro Model of Carbon Fiber/Cyanate Ester Composites and Analysis of Machining Damage Mechanism

Machining damage occurs on the surface of carbon fiber reinforced polymer (CFRP) composites during processing. In the current simulation model of CFRP, the initial defects on the carbon fiber and the periodic random distribution of the reinforcement phase in the matrix are not considered in detail, which makes the characteristics of the cutting model significantly different from the actual processing conditions. In this paper, a novel three-phase model of carbon fiber/cyanate ester composites is proposed to simulate the machining damage of the composites. The periodic random distribution of the carbon fiber reinforced phase in the matrix was realized using a double perturbation algorithm. To achieve the stochastic distribution of the strength of a single carbon fiber, a novel method that combines the Weibull intensity distribution theory with the Monte Carlo method is presented. The mechanical properties of the cyanate matrix were characterized by fitting the stress-strain curves, and the cohesive zone model was employed to simulate the interface. Based on the model, the machining damage mechanism of the composites was revealed using finite element simulations and by conducting a theoretical analysis. Furthermore, the milling surfaces of the composites were observed using a scanning electron microscope, to verify the accuracy of the simulation results. In this study, the simulations and theoretical analysis of the carbon fiber/cyanate ester composite processing were carried out based on a novel three-phase model, which revealed the material failure and machining damage mechanism more accurately.

Comparison between experimental and analytical results for seesaw energy dissipation systems using fluid viscous dampers

This paper presents results of experimental and numerical investigations of a seesaw energy dissipation system （SEDS） using fluid viscous dampers （FVDs）. To confirm the characteristics of the FVDs used in the tests, harmonic dynamic loading tests were conducted in advance of the flee vibration tests and the shaking table tests. Shaking table tests were conducted to demonstrate the damping capacity of the SEDS under random excitations such as seismic waves, and the results showed SEDSs have sufficient damping capacity for reducing the seismic response of flames. Free vibration tests were conducted to confirm the reliability of simplified analysis. Time history response analyses were also conducted and the results are in close agreement with shaking table test results.

跨临界CO_(2)热泵干燥系统研究现状与进展

干燥工艺在工、农业生产中耗能巨大,研究和应用实践表明相比于其他干燥技术,热泵干燥技术具有较好的节能效果和经济效益。CO_(2)作为自然工质对环境友好,而且跨临界CO_(2)循环放热过程具有明显的温度滑移,相比常规工质冷凝温度恒定的亚临界循环,更适合用于热泵干燥工艺。本文阐述了跨临界CO_(2)热泵干燥系统的研究现状,从CO_(2)热泵干燥应用的可行性、系统模型建立与关键参数分析、实验研究及系统优化等方面进行了深入讨论,总结各种CO_(2)热泵干燥系统优化方式的优缺点,提出了目前跨临界CO_(2)热泵干燥系统研究中存在的问题,为CO_(2)热泵干燥技术未来的研究应用提供参考。

离心脱开型斜撑离合器脱开转速计算及试验验证

脱开转速是斜撑离合器的主要技术指标,对斜撑离合器的使用寿命和主机安全性有重要影响。介绍了离心脱开型斜撑离合器的结构,建立力学分析模型,推导出离心脱开型斜撑离合器脱开转速的计算公式,并以某典型型号离合器为例进行脱开转速理论计算,同时提出了一种试验方法测试该型号离合器脱开转速,理论计算值与试验值基本一致,验证了脱开转速理论计算方法的正确性。

基于热路法的自然冷却永磁同步电机定子温度计算

为获取电机运行时的温升情况,本文使用热路法对一台自然冷却永磁同步电机定子的温度进行计算。在Maxwell中进行二维电磁场仿真,得到电机定子的损耗。将电机定子分为多个部件,使用简化圆筒T型热路模型并结合立方体热路模型搭建各部件的单元模型,在计算各部件的相关热阻后,得到电机定子的热路模型。根据热平衡原理建立温度场线性方程组,求解电机定子的温度。在Fluent中建立电机定子的三维简化模型,给予材料属性、边界条件及其他相关设置后,进行电机稳态温度场仿真。最后对电机进行温升实验,使电机在额定工况下运行至热平衡状态后,进行实验测量。将热路法计算的结果与实验和仿真结果进行对比分析,验证了热路法的正确性。