A method of elimination of undesired resonant points of microstrip antenna by cutting U-shaped slot on the ground

A method is proposed to eliminate undesired resonant points of a dual-layer circular polarization microstrip antenna, the frequency of which is 2.42 GHz. The simulation results show that there are two undesired resonant points, the frequencies of which are both greater than the resonant frequency. One is around 4.4 GHz, while the other is around 5.8 GHz. As they would disturb the proper functioning of the antenna, the paper will eliminate the undesired resonant points by cutting U-shaped slots on the ground, Size of the slot is half of the wavelength of corresponding frequency point if slot is cut on the patch, while it is a quarter of the wavelength if there is a opening port on the slot. The simulation results show that it＇s effective to eliminate the undesired resonant points in this way.

Double U-Shaped Slots Loaded Stacked Patch Antenna for Multiband Operation

The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequency bands. The total size of the antenna is 39.25 × 29.25 mm2. The multiband stacked patch antenna is studied and designed using IE3D simulator. For verification of simulation results, the antenna is analyzed by circuit theory concept. The simulated return loss, radiation pattern and gain are presented. Simulated results show that the antenna can be designed to cover the frequency bands from (4.24 GHz to 4.50 GHz, 5.02 GHz to 5.25 GHz) in C-band application, (7.84 GHz to 8.23 GHz) in X-band and (12.16 GHz to 12.35 GHz, 14.25 GHz to 14.76 GHz, 15.25 GHz to 15.51 GHz, 17.52 GHz to 17.86 GHz) in Ku band applications. The bandwidths of each band of the proposed antenna are 5.9%, 4.5%, 4.83%, 2.36%, 3.53%, 1.68% and 1.91%. Similarly the gains of the proposed band are 2.80 dBi, 4.39 dBi, 4.54 dBi, 10.26 dBi, 8.36 dBi and 9.91 dBi, respectively.

Experimental Study and 3D CFD Analysis on the Optimization of Throttle Angle for a Convergent Vortex Tube

Seven adjustments of convergent-type Vortex Tube （VT） with different throttle angles were applied. The adjustments were made to analyze the influences of such angles on cold and hot temperature drops as well as flow structures inside the VTs. An experimental setup was designed, and tests were performed on different convergent VT configurations at injection pressures ranging from 0.45 to 0.65 MPa. The angles of the throttle valve were arranged between 30° to 90°, and the numbers of injection nozzles ranged between 2 and 6. Laboratory results indicated that the maximum hot and cold temperature drops ranged from 23.24 to 35 K and from 22.87 to 32.88 K, respectively, at four injection nozzles. Results also showed that temperature drop is a function of hot throttle valve angle with the maximum hot and cold temperature drops depending on the angle applied. We used graphs to demonstrate the changes in the cold and hot temperature drops with respect to hot throttle angle values. These values were interpreted and evaluated to determine the optimum angle, which was 60°. The CFD outputs agreed very well with the laboratory results. The proposed CFD results can help future researchers gain good insights into the complicated separation process taking place inside the VTs.

缝隙节流液体静压轴承油膜刚度系数的研究

油膜刚度系数是液体静压轴承的关键性能参数之一。针对缝隙节流液体静压轴承,推导了其油膜承载力的解析表达式,并在此基础上进一步推导了油膜刚度系数的解析表达式。相比于传统经验公式,采用该表达式的计算结果与实验结果更吻合。通过分析应用案例可知:油膜承载力与节流参数、主轴离心率均呈正相关关系;油膜正向刚度系数随着离心率的增大而减小,油膜交叉刚度系数随着离心率的增大而增大,并且正向刚度系数明显大于交叉刚度系数。利用该轴承油膜刚度系数的表达式,可以通过测量轴承运行过程中的轴心位置,实时得到轴承油膜刚度系数,从而对缝隙节流液体静压轴承的运行进行有效监控。

长槽道内文丘里湿气流量测量虚高特性

为了研究节流装置结构参数对湿气流量测量虚高特性的影响,设计了与传统文丘里管结构相对的边壁绕流型长槽道内文丘里节流装置,并对其湿气测量特性进行了实验研究,对比分析了节流装置水力直径和管道液相分布对虚高的影响。实验研究和理论分析表明,气相对液相加速的摩阻压降是影响虚高的重要因素,在相同工况条件下,节流装置流通区域的水力直径越小,液相分布越均匀,气液两相混合越充分,虚高值越大。对节流装置结构参数对虚高的影响进行了较为细致的分析,为基于边壁绕流型节流装置的湿气流量计的结构优化设计奠定了基础。

基于AMESim的油缸缓冲装置的研究

针对液压驱动活塞式消防泵的油缸,提出采用截面为矩形的恒截面和变截面组合的节流槽作为油缸缓冲装置,分析了该缓冲结构的数学模型,通过AMESim软件对缓冲油缸的工作过程进行了仿真,分析了节流槽参数对缓冲效果的影响,结果表明:节流槽的宽度、深度和个数越小,缓冲末速度越小,但缓冲压力峰值越高;反之,缓冲压力峰值越低,但建立缓冲压力时间越长,且末速度也越大。因此,需要合理地选择油缸缓冲结构的参数。

U型节流槽流量特性多目标优化

以某内滑阀内部流场为研究对象,利用Fluent软件的Standard k-ε湍流模型对液压冲击机构进行仿真分析。通过改变节流槽的深度、宽度及半圆轴长度等,分析节流槽结构参数对其流量特性的影响。利用拉丁方试验设计获得相应结构参数下的特征试验方案与仿真结果,利用Kriging插值法求得在整个尺寸范围内的试验结果,再利用遗传优化算法得到满足流量快速响应特性和压力冲击性能的U型节流槽Parato解集,选取特定节流槽结构参数对优化结果进行验证。仿真结果表明:优化后的U型节流槽结构可在保证流量快速性要求的同时降低阀口的压力冲击。

普通汽车加装自动变档系统的探索

对现有普通手动变速器汽车的自动变档改造做了一些探索.提出了几种具体应用方案,并介绍了其中一种的机械及电控原理,给出了此系统的电子控制原理图.其系统结构紧凑,操控可靠性高,具有一定的使用价值.

多路换向阀节流槽流场的CFD解析

针对整体式多路换向阀在换向过程中存在较大液力冲击及能耗的问题,在阀芯处开节流槽以减小其对液压系统的影响,基于FLUENT对阀体内的复杂流场进行仿真及分析。完成多路换向阀内部流场的三维建模,通过对其不同开口度进行数值仿真计算,得到油液速度场中高速射流区域的变化趋势;并对三角形、矩形、半圆形节流槽对应的流场进行可视化对比分析,结果表明矩形节流槽缓解冲击力和降低噪音的效果最好。对多路阀节流槽形状设计具有一定参考价值。

斜轴式定量柱塞泵的动态特性仿真分析

以某型斜轴式定量柱塞泵为研究对象,基于节流槽结构设计及其内流场特征,结合渐扩形节流槽面积的确定原则,使用端盖节流槽面积计算公式,在性能仿真软件中搭建了柱塞泵性能仿真模型,针对影响其动态特性的几个关键因素进行变参分析,得到了有益的结论。

Analysis and design of compact printed monopole UWB antennas with multiple notched bands

This paper presents three compact ultra-wideband(UWB)antennas fed by coplanar waveguide(CPW).The proposed antennas consist of a planar circular patch monopole UWB antenna and multiple etched slots on the feed line.Simulation by Ansoft high frequency structure simulator(HFSS)10.0 shows that the in-band impedances are quite stable and satisfactory.Rejected narrow frequency bands are further obtained within the wideband width by inserting U-shaped slots into the fed line of the antennas.The antennas have a dimension of 50mm by 40mm by 1.5mm.The simulation and measurement results show that the proposed antennas have stable directional radiation patterns,very low profile and low fabrication cost,which are suitable for the UWB system.

异形反馈槽对比例节流阀特性的影响

研究了不同反馈槽形状下Valvistor型比例节流阀的流量特性,为实现执行器多级流量控制提供参考。建立了比例节流阀数学模型和多学科联合仿真模型,并通过试验验证了模型的准确性。在此基础上,分析了不同反馈槽形状和参数对阀动静态特性的影响。结果表明:反馈槽形状不同,比例节流阀流量特性不同;当反馈槽形状为倒梯形时,阀初始流量增益小,有利于执行器平稳启动;当反馈槽形状为双矩形组合时,阀具有良好的微动控制特性;同时,比例节流阀响应速度随反馈槽面积增益的增大而变快,但较大面积增益和较小预开口量会降低阀的稳定性。