火箭发动机射流动力学仿真研究

本文基于计算流体动力学理论,利用数值仿真手段,对火箭发动机燃气射流流场进行了仿真研究,探索火焰尾流结构和参数分布特征;并对火箭发射过程导流槽内部燃气射流特性参数分布进行数值模拟,结合实测结果,揭示数值仿真应用于火箭发射场导流槽设计的可行性。     

火箭发动机射流动力学仿真研究

本文基于计算流体动力学理论,利用数值仿真手段,对火箭发动机燃气射流流场进行了仿真研究,探索火焰尾流结构和参数分布特征;并对火箭发射过程导流槽内部燃气射流特性参数分布进行数值模拟,结合实测结果,揭示数值仿真应用于火箭发射场导流槽设计的可行性.     

某双阀芯电液比例多路阀主阀进口节流流场及阀口压降特性研究

以某系列双阀芯电液比例多路阀为研究对象,采用CFD流场仿真技术和PIV可视化测速技术对不同阀口开度和流量下的主阀沿进口流道、节流口、阀腔的流场进行了流体仿真和试验可视化研究。应用Fluent软件仿真研究了主阀进口节流流场分布并得出阀口压降特性;采用PIV试验研究的手段对流场分析结果加以验证,应用2D-PIV技术获得主阀腔内部一个截面上的流场分布,并通过相似理论计算得出阀口压降特性。CFD流场仿真和PIV试验结果表明：该双阀芯电液比例多路阀主阀出油环形腔内会形成较大旋涡,且阀口开度和流量对主阀进口节流内部流场结构和阀口压降特性有重要的影响。研究结果对定性分析双阀芯电液比例多路阀主阀内能量损失和噪声、主阀的结构和流道的设计以及优化具有重要实际意义,为CFD技术和PIV技术在双阀芯多路阀领域的应用研究提供了参考。     

小流量射流流量计的数值模拟与设计

射流流量计是一种测量下限极低,无机械可动部件,且不受恶劣环境影响的振荡式流量计,能够较好地解决小流量测量问题,应用前景广阔。但是现有的射流流量计的测量下限比理论值高很多,且缺乏完整的结构参数设计和性能优化设计准则的指导,限制了其应用价值。文中以气体小流量射流振荡器为研究对象,采用理论研究、仿真分析和实验验证相结合的研究方法,研制出一种适合于测量气体小流量的射流流量计。     

小口径旋进旋涡流量计的结构优化

根据已有的DN25旋进旋涡流量计的结构参数,设计了DN20小型旋进旋涡流量计,而后借助ANSYS Fluent流体仿真对DN20小型旋进旋涡流量计进行了结构与流场关系的研究。通过正交试验,获得了DN20小型流量计不同结构的内部流场及其信息,分析了流量计工作范围内旋涡规律和流量之间的关系;进一步更换不同测量横截面,查看压力场及其变化规律,与原结构方案的测量截面进行比较,选定最优测量截面与测量点,为DN20流量计产品研发提供了理论依据。     

列状多孔整流器在水平浮子流量计中的应用

流量的测量精度受流量计上游速度分布的影响极大。仪表是在流体速度充分发展的条件下设计和校正的, 而流体的扰动如偏流、二次流、旋转流都能引起系统误差。在前置管段安装整流器是解决直管段不够的有效途径。根据计算流体力学分析了水平式浮子流量计浮子抖动的原因,设计了安放在流量计内部的列状整流器,给出并比较了安装和未装整流器情况下的内部流场变化的仿真结果,同时评估了整流器的整流效果。为了验证其整流效果, 该整流器在两种不同口径的水平浮子流量计中进行现场试验,结果表明列状整流器能降低仪表的不确定度达0．5％以上。     

临界流量计内部流场理论计算研究

为了获得临界流量计内的流场参数分布情况,按照理想气体一维绝热流动基本关系式建立了临界流量计内部流场的理论计算方法,得到流场参数的计算公式。以公式为基础,分析了流量计输入条件改变引起内部参数变化的规律。计算了某流量计内的流场,得到主要参数沿轴向的分布。找到一种通过公式计算最大允许背压比的方法,能获得正确的计算结果。该流场理论计算研究过程对临界流量计的设计具有一定参考意义。     

沉降离心机流场分析与结构改进

沉降离心机的生产能力取决于流体的运动形式与运动速率,因此对沉降离心机内部流场的研究有助于沉降离心机的结构优化设计。本文采用流体计算力学技术对沉降离心机在稳定工作状态下的内部流场进行仿真分析,解释在实际生产过程中出现的一些现象,并对沉降离心机结构作出若干处优化。通过沉降离心机结构改进前后的流场仿真分析研究对比,为优化后的沉降离心机的性能可靠性提供一定的理论依据。     

偏导射流阀前置级流场特征参数的仿真计算

根据偏导射流阀前置级的结构以及内部油液的流动特性,将前置级射流过程分为两个阶段。采用标准k-e模型对前置级流场进行了两相流二维数值计算,对两次射流过程中油液的流动形态以及流场压力和速度分布特点展开研究。分析得出,初次射流为自由紊动射流,二次射流为冲击射流,并发现在偏转板处于中位时两接收腔外侧圆弧拐角低压区处出现空化现象。偏导射流阀实际工作过程中偏转板会发生偏移,因此,建立了不同偏移量下的仿真模型,分析了不同偏移量下流场信息的变化规律,获得了前置级流场的压力云图以及对应的速度矢量图。利用仿真结果中两接收腔压力值和V形槽两侧壁静态压力数据,分别计算出了前置级流场的压力增益和液动力的大小。为偏导射流阀基础特性的深入分析奠定了基础,并对该类阀设计的改进和优化具有理论指导意义。     

高压喷嘴的射流仿真研究

针对高压喷嘴射流发散快以及速度稳定性差等问题,将Fluent仿真技术应用到高压喷嘴的流场分析中.根据高压喷嘴结构特点,为喷嘴及外部喷射区域建立了轴对称的几何模型;并根据喷射过程中流体速度的变化情况进行了网格的划分与加密,然后对高压喷嘴的淹没与非淹没射流流场以及不同收缩角时的非淹没射流流场进行了仿真分析;在流体理论的基础上提取了各种情况下的速度分布图,并对其结果进行了对比分析.研究结果表明,收缩角的不同对喷嘴流场的轴线的速度变化影响较大,当收缩角为10°时流场速度的稳定性最好;此外,通过对淹没射流与非淹没射流的流场情况进行比较,得出了非淹没射流对速度的集中更为理想的结论;仿真分析结果也为高压喷嘴结构及喷射形式的选取提供了一定的依据.     

Bipolar corona assisted jet flow for fluidic application

In this paper, we present a study on a jet flow, assisted by low net charge ion wind from bipolar corona discharge setup. The ion wind is simultaneously generated from both positive and negative electrodes placed in parallel, adding momentum to the bulk flow directed alongside the electrodes and focused in the middle of interelectrode space. The electrodes are connected to a single battery-operated power source in a symmetrical arrangement, where the electrode creating charged ions of one polarity also serves as the reference electrode to establish the electric field required for ion creation by the opposite electrode, and vice versa. Multiphysics numerical simulation is carried out with programmable open source OpenFOAM, where the measured current-voltage is applied as a boundary condition to simulate the electrohydrodynamics flow. The jet flow inside the device is verified by hotwire anemometry using hotwires embedded within the device, with the measured values in good agreement with simulation. The corona discharge helped to focus the jet and increased the flow peak velocity from 1.41 m/s to 2.42 m/s with only 27.1 mW of consumed discharge power. The device is robust, ready-to-use and minimal in cost. In addition, as the oppositely charged corona flows are self-neutralized, the generated air flow remains neutral and therefore does not attach to a particular target, which expands the application range. These are important features, which can contribute to the development of multi-axis fluidic inertial sensors, fluidic amplifiers, micro blowers, gas mixing, coupling and analysis with space constraints and/or where neutralized discharge process is required, such as circulatory flow heat transfer or the formation of low charged aerosol for inhalation and charged particle deposition.     

高速点阵式脉冲喷射发生器的无传感器控制

为提高标识设备关键部件—高速点阵式脉冲喷射发生器的性能以改善喷印效果,在建立喷射器数学模型的基础上,设计了滑模观测器.通过观测器构成反馈系统,在不增加硬件成本的前提下实现对高速脉冲喷射器的无传感器控制,使其能够准确跟踪理想轨迹,降低阀芯与静铁的冲击速度,并消除振动和噪音.实验结果表明,喷射器工作过程中阀芯与定位静铁的冲击速度由开环控制的0.55 m/s降到了闭环控制的0.02 m/s,振动和噪音基本消失,喷射效果明显改善.对钢铁产品进行的喷码实验显示,设计的喷射器的性能可以满足实际生产需要.研究过程为高速脉冲喷射器控制单元的设计提供了理论基础.     

喷嘴宽度对偏转板射流阀射流效率影响的仿真分析

利用Pro/E和Fluent软件对不同λ₁(喷嘴宽度D₁与导流窗口最小宽度H₁的比值)的偏转板射流阀进行几何建模与流场仿真,得到不同λ₁ 下偏转板射流阀内部射流速度、压力云图和射流流场的速度、压力分布特征;通过分析仿真数据得到λ₁对供油流量Q_S、射流流量Q_J、射流流量效率η_J的影响规律。研究发现,喷嘴喷射出的部分油液由于受到V形导流斜面的作用沿着V形导流斜面反向运动,从而使喷向接收口的有效射流流量减小,同时在偏转板入口两侧出现漩涡和能量损失;随着λ₁增大,供油流量Q_S近似线性增大,而射流流量Q_J先增大后又减小;当λ₁=1时射流流量Q_J取得最大值12.5 kg/s,对应的射流流量效率η_J最大为77.6%。研究结果为偏转板射流伺服阀的效率提高及结构优化设计提供理论依据与参考。     

Numerical modeling of internal flow in a fluidic oscillator

A numerical investigation of a fluidic oscillator was performed to understand the unsteady internal flow field and geometrical effects on the performance using three-dimensional unsteady Reynolds-averaged Navier-Stokes equations. Effects of the two geometrical parameters, i.e., the inlet width of the mixing chamber and outlet throat width, on peak jet velocity ratio at the exit and pressure drop through the oscillator, were evaluated. The unsteady simulation was performed using shear stress transport turbulence model with air as working fluid at Reynolds number 30000. Computational results showed good qualitative and quantitative agreements with available experimental results for the flow structure and frequency of the oscillating jet. Results of the parametric study suggested that the inlet width affected significantly the flow in the fluidic oscillator, while effects of the throat width on the performance parameters were not remarkable.     

电导式相关流量计应用于油井井下流量测量

本文提出了一种新型的电导相关流量计,其敏感元件采用两个电导传感器,该流量能够应用于高含水油井的油水两相流流量测量,在多相流动实验装置上进行的实验表明,该流量计测量的流速范围宽,线性好,该流量计已经在大庆油田进行现场试验,使用该流量计在井下测量的油水的总流量与地面计量结果对比良好。     

A mini fluidic oscillating flowmeter

This paper presents a mini fluidic oscillating flowmeter. This device is composed of three microfluidic laminar bistable amplifiers. The microfluidic amplifiers are connected in such a way that the measured flow through the mini fluidic oscillating flowmeter generates a periodical pressure signal with a high value of SNR (signal to noise ratio). The frequency of the pressure signal is proportional to the measured flow. The mini fluidic oscillating flowmeter works with gas or liquid. To calibrate the mini fluidic oscillating flowmeter, for gas flows, a volumetric flowmeter was used. To calibrate it for liquid flows, an experimental test bench was realized. The gas operating range of the mini fluidic oscillating flowmeter is up to Re=1500 starting from Re=200; the liquid operating range is up to Re=5700 starting from Re=170. The maximum error of the measurement is <2% of the full scale value, the reading error is <3% for gas flows and <3.8% for liquid flows.     

Numerical simulation ultrahigh waterjet (WJ) flow field with the high-frequency velocity vibration at the nozzle inlet

This paper presents an investigation of ultrahigh pressure waterjet (WJ) flow field with the high-frequency velocity vibration at the nozzle inlet by computational fluid dynamics method. The velocity field of the flow inside the WJ nozzle is obtained. The influence of vibration parameters, such as amplitude and frequency on the flow field are studied. The results of investigation indicate that the flow velocity at the WJ nozzle outlet has almost the same vibrating type with the inlet velocity vibration. During a vibration cycle, the velocity field of the flow is changing greatly. The serials value of the vibration frequency and amplitude are taken to test their influence on the flow field. The simulation results show that the flow field also changes greatly with the different frequency and amplitude. Based on the obtained results, the mechanism of system pressure vibration influence on the water jet flow field inside the WJ nozzle is obtained, and a new method is provided to optimize the machining process with the aim to improve the machine efficiency and surface quality of the work piece.     

Theoretical study of vertical slug flow measurement by data fusion from electromagnetic flowmeter and electrical resistance tomography

Electrical resistance tomography (ERT) can be used to obtain the conductivity distribution or the phase distribution of gas/liquid flows (e.g. slug flow). Using proper parameter models and flow regime identification models, the measurement of phase size, void fraction, and pattern recognition can be realized. Electromagnetic flowmeters have been used to measure conductive single-phase liquid flows. However, neither ERT nor electromagnetic flowmeters (EMF) can provide accurate measurement of gas/liquid two-phase flows. This paper presents an approach to fuse the information from ERT and an electromagnetic flowmeter. A model for the measurement signal from the electromagnetic flowmeter has been developed based on the flow pattern and the phase distributions, which are obtained from the reconstructed images of ERT, aiming to reduce the measurement error of the electromagnetic flowmeter and enhance the measurement accuracy. Through the simulation research of virtual current density distribution, the feasibility of fusion of electromagnetic flowmeter and ERT to measure gas/liquid two-phase vertical slug flow is verified. By theoretical analysis, the relationship between the output of electromagnetic flowmeter and flow parameters is established. The electrical potential difference of the electromagnetic flowmeter, average velocity, volume flow rate and gas void fraction between the bubble size and location are also investigated. The fusion approach can be used to measure vertical slug flows.     

基于ARM的智能电磁流量计转换器的研制

提出了一种基于ARM的电磁流量计转换器的设计方案,详细说明了模拟信号处理放大电路[1]、励磁模块和智能处理单元的设计,采用模块化软件设计方法,实现多种功能。采用标准表比较法对样机进行了标定试验,结果表明在0.4 m/s以上的流速只需单直线线性校正,精度即可达1%。     

Experimental and numerical study on a novel thermal mass flowmeter that is insensitive to radial flow velocity distribution

A novel thermal mass flowmeter (TMF) is proposed by improving the composition and structure of the probe in this study. An experimental setup was developed to compare the effects of installation angles on the measurement characteristics of the novel and traditional TMF (flow velocity range of 1.0–8.0 m/s), and three-dimensional numerical models were established to compare the effects of axial positions and insertion depths on the measurement characteristics of novel and traditional TMF (flow velocity range of 0.05–8.0 m/s). The experimental results show that when the installation angle changes from 0° to 90°, the maximum power variation of traditional TMF is 16.5%, while that of the novel TMF is only 0.6%. The simulation results show that when the axial position changes from 9 to 1 m, the maximum power variation of traditional TMF is 11.5%, while that of the novel TMF is only 3.8%. When the insertion depth of the velocity sensor translates from the pipe center to 0.10 m upward, the maximum power variation of traditional TMF is 91.6%. The novel TMF is installed by thread or flange compression, with a fixed and unique insertion depth of D/2, there is no change in the insertion depth during measurement. In conclusion, the effect of the flow velocity distribution on the measurement characteristics is significantly reduced in the novel TMF compared to the traditional TMF, the measurement results are more accurate.