高低频不同电压条件下腔室内CCP冷等离子体源的仿真分析

等离子体的状态的变化特征,特别是在双频情况下,是PECVD工艺设备的一项重要指标,这促使人们用不同的方法对它们进行研究。本文使用CFD-ACE 商业软件建立了二维流体模型对N2等离子体进行仿真。首先在高频13.56MHz,高频电压300V,低频电压0V的条件下描述了等离子体,特别是在鞘层部位的电势、电子数量密度、氮自由基和电子温度,分布的基本特征。在此基础上,讨论了高频电压分别是200V,300V,400V时及低频0.3MHz,低频电压分别是500V,600V,700V时对等离子体密度的影响。结论表明,在电极表面形成了约3mm厚的鞘层,在鞘层内电势和电子温度随时间和空间变化较大,而在非鞘层区域内电势跟随电极电压的变化而变化,但几乎不随空间变化,电子温度也只在很小的范围内变化。氮自由基的数量密度也受射频电压的调制,但相对变化很小。等离子体密度仅在鞘层区域内随时间发生变化,所以通过比较主等离子体区参数可以看出,等离子体的密度随着高频电压升高,随低频电压的升高略有下降,同时x方向和y方向的均匀性将会发生变化。因此,在其他条件不变的情况下需要选择合适的高低频电压来获得高密度和均匀性均合乎要求的等离子体。     

大面积VHF-PECVD反应室喷淋式平板电极间电场和流场数值模拟

以大面积喷淋式平板电极甚高频等离子体增强化学气相沉积(VHF-PECVD)反应室为研究对象,利用FlexPDE和CFD-ACE+商业软件,对反应室电极间的电场和流场分布进行了数值模拟。根据数值模拟结果可知:对于大面积喷淋式平板电极VHF-PECVD反应室,电极间气体流速分布呈现管流特征,而气压分布和电场分布具有类似的分布规律,即在大面积电极中央区域电场较强气压较高,而电极边缘区域电场较弱气压较低;另外,反应室采用喷淋式平板电极进行反应气体馈入,气体总流量、工作气压和电极间距是调节电极间气压分布均匀性的重要参量,采用大电极间距、高工作气压,以及小的气体总流量有助于获得均匀的气压分布。     

A Three-Dimensional Navier-Stokes–Based Numerical Model for Squeeze-Film Dampers. Part 1—Effects of Gaseous Cavitation on Pressure Distribution and Damping Coefficients without Consideration of Inertia

Even though most published results detailing damper behavior consider only the liquid phase, the cavitation process in the lubricant film, when it happens, is critical for the damper's performance. A number of modeling approaches, such as the half-Sommerfeld and Elrod models, were proposed in order to account for the effects of cavitation on the pressure generation, without directly simulating the cavitation process. Based on the experimental data, a few other homogeneous cavitation models have also been developed. All these models are based on the classical Reynolds equation. In this article, a three-dimensional numerical model is developed and validated in connection with the operation of a two-phase squeeze-film damper. The full Navier-Stokes equations (NSE), coupled with a homogeneous cavitation model, is solved to simulate the flow of the two-phase lubricant film and the associated pressures. The pressure variation on the journal surface and the gas concentration distribution in the lubricating fluid (cavitated region) will be presented. The damping coefficients predicted by the NSE model are compared to the ones that resulted from the application of the Reynolds equation.     

基于回归正交设计的ICP刻蚀机工艺腔室流场特性分析

为研究感应耦合等离子体(IcP)刻蚀机工艺腔室结构对流场特性的影响,采用回归正交设计方法对腔室半径、腔室高度、进气口半径以及进气流量4个设计参数进行试验设计,利用商业软件CFD-AcE 建立IcP刻蚀机工艺腔室二维流场仿真模型.定义了静电卡盘上方气压分布均匀性评价函数,通过对试验结果的回归分析,确定了关键参数对气压分布均匀性影响程度的定量关系,并由此建立了拟合度较高的二次回归方程.结果表明腔室高度为最显著影响因素.经过验证可见,回归方程的计算结果与仿真分析结果保持了较高的一致性,可以为结构与工艺条件相近的刻蚀机、化学气相沉积(CVD)设备以及氧化/扩散系统的结构研究与设计提供参考.     

基于CFD的收缩型喷嘴的喷油仿真研究

为了解决航天器运动部件润滑失效的问题,将按需喷墨打印技术（DOD）应用于空间机构的润滑油主动补充系统.通过运用CFD-ACE数值仿真软件,结合计算流体力学（CFD）的理论和流体体积算法（VOF）中的分段线性界面重构技术（PLIC）,对油滴从收缩型喷嘴（锥角约为43°）中形成到喷射进入稀薄大气中的过程进行气液两相流体的仿真分析.在相同的驱动电压条件下,分别对粘度,表面张力,以及喷嘴直径对油滴喷射行为的影响进行分析;提出油滴的体积等效计算方法.仿真数据和图像分析表明：此喷嘴结构,随着粘度的增加,油滴的喷出速度减小,体积也减小;随着表面张力的增加,油滴的喷出速度减小,体积增大.合理选择喷嘴直径是油滴能否有效喷出的关键因素.     

Damping and added mass coefficients for a squeeze film damper using the full 3-D Navier-Stokes equation

Direct and cross-coupled damping coefficients are developed for the 2π-film, π-film (Gumbel cavitation condition) and homogeneous two-phase mixture films in a squeeze film damper. The numerical simulation uses the CFD-ACE+ commercial software, which employs a finite volume method for the discretization of the Navier-Stokes equations (NSE). In order to determine the dynamic coefficients, the NSE is combined with a finite perturbation method applied to the ‘equivalent journal’ of the damper. It was found that for the 2π-film and the Gumbel conditions, the damping coefficients exhibit linear characteristics, while the homogeneous cavitation model yields nonlinear coefficients. Using the CFD-ACE+, the inertia/added mass coefficients are derived for the limiting cases of the short and long dampers, respectively. The first set of forces is calculated by setting the fluid density to its actual value. The second set of forces is calculated when the density of the fluid is set close to zero (1E-10 kg/m³), thus practically eliminating the effects of the inertia terms. Subtracting the two sets of forces from each other, allows the determination of the inertia component contribution and the corresponding inertia coefficients. By varying the density, dynamic viscosity and whirling speed, it was found that the inertia coefficients follow a single curve represented by a function dependent on the modified Reynolds number, Re*. The inertia coefficients presented in this study are compared with the ones reported by other researchers that used the modified Reynolds equation. Some differences were found between the NSE based results and the Reynolds equation based outcomes. This is attributed to the three-dimensional effects introduced by the totality of the terms comprised in the full NSE.     

一种空间压电润滑装置的建模与仿真

提出一种主动按需供油的压电润滑装置,以解决航天器运动部件润滑失效问题。首先运用有限元分析软件ANSYS对压电振子进行了瞬态分析,再利用多相流流体软件CFD-ACE+建立喷嘴气-液两相流体模型。最后对液滴喷射过程进行数值模拟,以考察脉冲电压幅值变化对各喷射参数的影响。数值模拟结果表明,增加脉冲电压幅值,可增加液滴长度和速度,但对液滴产生时间影响不大。     

ICP刻蚀机反应腔室气流仿真研究

感应耦合等离子体(ICP)刻蚀机反应腔室的气流分布是影响等离子体分布与刻蚀工艺均匀性的重要原因之一.使用商业软件CFD-ACE 中的连续流体与热传递模型,对反应腔室中气流分布进行了仿真研究,讨论了不同质量流量(50～250 cm3/min)入口条件下电极表面附近气压分布情况,同时讨论了不同腔室高度(H=0.08,0.12,0.14m)对气流分布均匀性的影响.研究发现电极表面附近气压分布呈现中心高边缘低的特征,并随入口质量流量的增加而升高;气流分布均匀性随腔室高度增加而有所提高,而同时平均密度却会下降.通过对比发现3D与2D模型仿真结果基本一致.     

A Three-Dimensional Navier-Stokes-Based Numerical Model for Squeeze Film Dampers. Part 2—Effects of Gaseous Cavitation on the Behavior of the Squeeze Film Damper

The damping coefficients for a squeeze film damper (SFD) were determined and discussed in Part 1 using the full Navier-Stokes equations (NSE) coupled with a homogeneous cavitation model. In this continuation, Part 2, article these coefficients are introduced into the governing equations of motion to determine the trajectory of the rotor and its stability. The nonlinear response of the damper predicted by the NSE model is compared to results obtained from the application of the Reynolds equation. The influences of gas mass concentration as well as that of the amount of imbalance on transmissibility and eccentricity of the damper are also investigated.     

波动载荷下频率对液体静压支承系统的影响

利用CFD-ACE+对液体静压支承进行数值模拟,并与理论公式进行对比,得到的流场结果与实际相吻合;同时揭示了波动载荷作用下,频率对液体静压支承系统动态特性的影响.结果表明:波动载荷作用下,频率对油膜厚度、承载力以及动刚度有不同程度的影响.这也为液体静压支承的可靠性设计提供了依据.