基于Lighthill方程的球阀气体内漏喷流声场数值模拟

建立考虑喷流扰动速度影响的Lighthill气动力声学方程.采用二阶加权平均中心差分隐格式方法,对不同内漏间隙下球阀气体内漏喷流声场进行了数值模拟.数值模拟结果表明,球阀内漏喷流流动伴随喷流噪声的产生.对于球阀结构,在发生内漏时存在二次截流,二次截流点为喷流噪声强度最高的位置.球阀通孔与阀体通道形成的过流空间是喷流噪声最强的区域.球阀下游流道喷流噪声强度要高于上游.模拟结果为球阀内漏声学检测提供了依据.     

球阀气体内漏的声场数值模拟及实验研究

以Lighthill气动力声学方程作为控制方程,采用有限差分法,对不同内漏度和压力差下的球阀气体内漏喷流声场进行了数值模拟。得出它们对球阀气体内漏喷流声场强度和传播特性的影响,确定了球阀气体内漏声场强度最高的位置。数值模拟表明,二次截流处附近的内漏噪声最强,噪声能随着内漏度和压力差的增大而增强,这为球阀气体内漏声学检测与定量分析提供了理论依据。同时采用声学方法对球阀的内漏发声进行了实验研究。实验结果也验证了数值模拟的正确性。     

气体管道泄漏声源产生机理仿真研究

以Lighthill气动声学方程为基础,采用时域差分方法,对不同泄漏孔直径的管道气体泄漏声场进行了数值模拟。数值模拟结果表明,在泄漏孔处,泄漏孔直径、内压对声强影响成线性关系。模拟结果为管道气体泄漏的声发射检测提供依据。     

辐射声场无反射边界模拟方法的数值分析

边界条件是声学计算的重要问题,声学计算中常用无反射边界模拟自由声场。目前无反射边界主要的模拟方法有辐射边界法、特性声阻抗法与PML法。研究无反射边界的声学数值计算,总结了三种无反射边界的理论基础,以平面波入射的自由声场为算例,对三种边界的吸声能力与应用等问题进行了分析和总结,论证了对于入射角度较大的问题,PML法具有最好的无反射能力,辐射边界法与特性声阻抗法则会产生较大的误差。     

驾驶室结构振动及其声固耦合噪声响应分析

利用有限元分析软件ANSYS和声学分析软件SYSNO ISE对卡车驾驶室的振动与内部声场耦合做了数值计算分析研究。介绍了振动频响分析方法,动力学计算与声学边界元模型耦合的具体步骤。通过计算分析,分别研究了驾驶室结构的声固耦合模型与非耦合模型对室内声场的影响,从而找出在不同的壁板厚度条件下,声固耦合作用对室内噪声的影响,以及驾驶室内声场的变化规律。     

涡扇发动机位置对外吹式增升效果影响的数值模拟

基于CFD技术,对涡扇发动机相对机翼轴向和垂直安装位置对增升效果的影响进行了数值模拟.从数值模拟结果可以看出,涡扇发动机喷流对增升效果的影响主要体现在:喷管喷流对襟翼的冲击,流经襟翼翼缝的高速喷流对杌翼上表面气流的引射作用及喷管喷流压力对机翼下表面流动的影响等方面.从发动机相对机翼位置方面分析,发动机相对机翼的轴向位置存在一个使升力系数达到最大的最佳位置,而在垂直方向,发动机越靠近机翼升力系数越大.     

基于计算流体力学计算结果的穿孔管消声器声学性能研究

为了准确研究温度与气体流动对某轿车穿孔管消声器声学性能的影响,建立消声器的结构模型与内部流体域模型,并分别划分流体域的计算流体力学(Computational fluid dynamics,CFD)网格与声学有限元网格。利用Fluent软件对消声器内部的温度场与气流速度场进行仿真计算。通过网格映射的方法,将CFD网格上温度、气流速度等数据转移到声学网格中,以CFD计算结果作为声场分析的边界条件,应用声学软件LMS Virtual.Lab Acoustics对消声器内部声场进行数值模拟,得到传递损失曲线。研究结果表明,介质温度升高使传递损失曲线向高频方向移动;存在气体流动时传递损失曲线向低频方向移动,传递损失也有所增加,尤其是在20~200 Hz的低频段内变化较为明显,但总体来看变化幅度不大。     

齿轮箱声固耦合系统面板贡献度分析

针对某型齿轮箱,提出一种基于声学贡献度分析的减振降噪设计方法.建立了齿轮箱有限元模型,计算其结构模态.将齿轮箱有限元网格作为结构网格和声学边界网格,在LMS Virtual.Lab下用边界元法求解真实工况激励下的辐射声场.利用声学贡献度分析,找到贡献度最大的面板,修改其设计参数.修改结构后,声场中某点噪声峰值降低8.2...     

基于CFD动网格技术的闸阀快速关闭特性研究

以核电站DN150闸阀为研究对象,针对该阀门在5 s的快关过程中,特定开度下的阀门内部流动特性,利用CFD动网格技术开展闸阀瞬态关闭过程数值模拟研究,得出了闸阀内部流动的压力、速度、涡量等分布,为闸阀的内部结构设计优化及关闭速度优化改进提供理论依据。     

空调器室外机流场和噪声特性

针对分体空调室外机空气侧流场和声场的特点,采用计算流体动力学(CFD)的方法对该系统的气体流动进行数值模拟。详细分析了轴流风扇流道内部和出口的速度分布,并利用激光微粒图像测速(PIV)手段,验证数值模拟结果,模拟结果与PIV测量值吻合较好。在CFD数值模拟的基础上,运用Lowson模型预估系统的离散频率噪声,预估值与测量值吻合较好。CFD技术能够有效地分析室外机空气侧流场特性,并为进行气动声学分析提供依据。     

微非对称结构燃油伺服阀压漂特性

偏导射流伺服阀前置级结构形式对压力漂移有极大影响。根据前置级结构参数的计算公式及伯努利方程,建立简化后前置级数学模型。以某款燃油电液伺服阀为研究对象,着重分析劈尖、接受口内侧边、接受口外侧边及V形槽等结构非对称性的影响。采用数值模拟的方式对不同回油压力及不同结构非对称条件下的前置级流场特性和压力漂移进行了仿真研究。通过PIV技术进行了流场可视化实验,验证了数学模型及仿真结果,得到了该款电液伺服阀零漂最大的工况及大小,并对改善偏导射流伺服阀的零漂提供了一定的参考依据。     

天然气管道球阀内漏发声机理及检测试验

球阀作为高压天然气输送管道的主要设备,其内漏时的喷流气体会产生声发射信号,通过研究该声发射信号特征规律将有助于阀门内漏流量量化检测。针对这一问题,进行了天然气输送管道球阀内漏发声机理和检测试验研究,分析了阀门内漏声发射现象产生的机理和内漏流量检测评价方法。在此基础上,应用声发射检测系统对3种不同尺寸内漏球阀进行了检测试验,通过试验分析了球阀在不同内漏流量下的声发射信号频谱特征分布规律,并采用小波包分析方法进行信号特征参数(信息熵、均方根、频域峰值)提取。拟合特征参数与内漏流量关系曲线,采用R~2(确定系数)指标对曲线拟合程度进行评价,评价结果表明,采用均方根值(root mean square,简称RMS)的曲线拟合程度最高(R2为0.979),可以用于天然气输送管道球阀内漏流量的量化检测。     

气体管道泄漏声源特性声发射试验研究

对气体管道泄漏孔处声源进行了声发射检测试验,分析了气体泄漏产生声发射的原因,通过对不同泄漏孔直径、不同泄漏内压情况下的声发射信号处理与分析,得出气体管道泄漏声源的频率范围及幅度随管道内部压力、泄漏孔径的变化影响规律,并与管道气体泄漏的数值模拟结果进行了对比分析,试验研究结果为气体管道泄漏声发射检测提供依据。     

Investigation of the relationship between internal fluid leakage through a valve and the acoustic emission generated from the leakage

The detection of acoustic emission (AE) signals produced by liquid and gas leakage through valves can be related directly to the qualitative leakage rate. This allows for cost estimation of losses in processes for several industries. However, to find out the relationship between qualitative leakage rate and AE signal large amounts of experimental data is needed. This paper presents a theoretical investigation of the acoustic emission to detect the internal leakage rate through a valve and experimental validation. The AE signals generated by internal liquid and gas leakage through valves were characterised. The effect of the influenced factors of leakage rates, inlet pressure levels, valve sizes and valve types, on AE parameter, AE_RMS, were studied and explained. The results of theoretical and experimental showed that AE signal power computed from the power spectral density (PSD) correlated well with influenced factors of leakage rates. Finally, a novel and inexpensive AE instrument has been invented for predicting qualitative leakage rate using a micro processor and derived relationship.     

A relative calibration method for a valve leakage rate measurement system

This paper presents a relative calibration method for an internal valve leakage rate measurement system using both microcontroller and acoustic emission (AE) methods. An air jet was selected to calibrate because it provides a frequency spectrum similar to the AE spectrum obtained from the valve leak, especially in the frequency range of 100-300 kHz. Three AE sensors mounted on a valve were used to validate the system calibration. Ratios between the average energy (AErms) were obtained from each pair of sensors, and these ratios were used to transfer the leakage AErms value. Subsequence, its performance to predict the leakage rate in the laboratory and in the field was tested. The error is less than 5% in almost cases. Its benefit is to reduce the recalibration time when a part of measurement system is changed. Accordingly, inexpensive equipment including an AE sensor was built, and its system performance was revealed.     

偏转板射流阀压力特性数值模拟分析

运用CFD软件对某型号偏转板射流阀内部不同阀口参数组合下的压力特性进行数值计算和分析,得出偏转板射流阀输出压力特性随不同阀口结构参数组合的变化规律。计算发现： 供油压力为4 MPa 时,λ1≈0.6,1.5≤λ2≤2,1≤λ3≤1.5组合下偏转板射流阀输出压力增益较大,输出压力特性曲线与偏转板位移成线性关系,研究结果可为偏转板射流伺服阀的工程设计和优化提供理论依据与参考。     

离心泵流动诱导噪声的数值预测

通过计算流体力学(Computational fluid dynamics,CFD)结合声振耦合求解方法针对一离心泵所产生的流动诱导噪声在泵壳外部的辐射情况进行数值预测。蜗壳内壁面上的非定常压力脉动监测值显示出蜗舌附近区域的脉动幅值较大,而在远离蜗舌位置处的脉动相对变化较小,在叶片扫掠频率及其谐频下的压力脉动要明显高于其他频率。通过声振耦合计算之后得到的泵壳外部声场辐射结果来看,当斯特劳哈尔数Sr=4时,由于该处所对应的压力脉动频率与泵壳结构的第四阶固有频率接近,可能会在声场与结构之间发生小幅共振,进而使得外场辐射噪声较大,也说明泵壳结构的振动模态对声场计算结果影响十分显著。通过外场监测点上叠加后的总声压级结果显示,各点基本上在60 dB上下波动,外场噪声辐射是泵内流体的压力脉动与壳体结构模态综合作用的结果。     

基于声发射理论的安全阀气体内漏信号特征研究

基于声发射理论,研究安全阀气体内漏情况下的信号特征。设计搭建了安全阀内漏模拟试验台和安全阀内漏声发射信号检测系统,通过理论分析和试验研究的方法,模拟了安全阀密封面划伤、密封面出现单个漏孔、密封面出现多个漏孔等内漏情况,研究了这些情况下声发射信号的频谱特征,泄漏率对于声发射信号特征参数平均信号电平(ASL)的影响,以及泄漏率与平均信号电平之间的量化关系,为实现安全阀内漏在线监测奠定基础。     

Design and experimental research of internal leakage detection device of buried pipeline ball valve based on valve cavity pressure detection

Valve is a key control component in the oil and gas long-distance pipelines, and the internal leakage detection of the valve has important research significance and application value. In this paper, a new method for detecting internal leakage of the buried pipeline ball valve based on the pressure change of the valve cavity was proposed. Firstly, a simplified internal leakage model of ball valve was established, and the change law of valve cavity pressure under different openings was obtained by finite element simulation. Secondly, a set of detection device was designed based on the internal leakage principle of buried ball valve and an experimental platform of ball valve internal leakage was built. Then, the pressure signal of the ball valve cavity under different openings and different pressures was collected by the pressure sensor, and the relationship between the power source pressure, the opening and the time required for the valve cavity pressure to reach equilibrium was established. Finally, the internal leakage degree of ball valve was simulated by ball valve opening and the Back Propagation (BP) neural network was selected to invert the ball valve opening. The inversion results showed that the maximum relative error of the liquid and gas experiment were 13.4% and 19.1%, respectively. The inversion results also verified the feasibility of BP neural network in the inversion calculation of the internal leakage degree of the ball valve, which provides guidance for the study of the classification of the internal leakage degree. The experiment and inversion results show that the proposed method can realize the detection of the internal leakage of the buried ball valve, which provides application reference in practice.