激光衍射法在喷嘴雾化特性测量中的应用研究

介绍了一种在线激光测量仪器装置及其测量原理和数据处理方法。在数据处理中引入分布函数 ,大大提高了计算速度。最后给出实验中实际测量超声波喷嘴燃油雾化粒子尺寸分布的数据 ,并根据结果分析了所测的超声波喷嘴雾化特性     

基于80C196单片机的超声波淤泥界面测定仪

利用超声波测量淤泥界面是一种精度较高，费用低廉的测量技术。本文阐述了利用包络线法测量污泥厚度的原理．介绍了实现该原理的系统构成和硬、软件的设计方案，并提出了适合单片机的数据处理算法。     

超声速雾化粒径二维分布测量系统设计

为获得航空煤油在超声速气流中喷射雾化后粒径二维分布信息,设计了基于PLIF/Mie双光谱成像法的测量系统。介绍了PLIF/Mie双光谱测量原理,设计了测量实验平台,包括超声速风洞、煤油喷射系统、光路、成像系统和时序控制单元等。实验表明,该测量系统能应用于超声速雾化场的粒径二维分布测量研究。     

超声波在纳米金属粉末制备中的应用与发展

对近年来超声波在纳米金属粉末制备中的应用与研究进展作了比较全面和详细的综述。其中着重介绍了与超声波有关的纳米金属粉末制备方法，包括了超声波雾化法、超声波化学沉淀法、超声波电化学法、超声波还原法、超声波溶胶凝胶法、超声波微乳液法、超声波模板法，并就这些方法中超声波作用的机理、特点和影响因素以及上述方法的技术问题和发展趋势进行了讨论。     

超声波流量计反射声道测量精度的数值模拟

为找到天然气输送过程中超声波流量计的误差来源，从气体流速分布角度分析超声波流量计反射声道的测量精度影响，根据工艺流程，建立管道模型，利用计算流体力学方法，获得管道内流场分布，分析了90°弯头和三通下游流速分布情况，以速度分布校正系数（k系数）的变化随雷诺数变化越小的声道测量精度越高作为衡量声道测量精度的方法，在90°弯头下游40D处分析了反射声道类型、声道分布方式以及声道入射角度对声道测量精度的影响。研究结果表明：（1）单反射和三反射的k系数稳定性优于双反射；（2）反射声道分布方式中k系数的稳定性，单反射2、4优于单反射1、3，双反射3优于双反射2、4优于双反射1，三反射2优于三反射1;(3)声道入射角度对单反射2、4和双反射1及三反射2的k系数稳定性几乎无影响，而对双反射2、4影响较明显。结论认为，该研究结果可为反射型超声波流量计的声道提供更合理的选择。     

新型细水雾灭火喷嘴的仿真及试验

为了解决细水雾喷头喷雾保护半径小的问题,研制了一种新颖的两级雾化高压细水雾灭火喷嘴。计算了索太尔雾滴直径DSM、喷嘴流速、流量和充分雾化距离。在CFD仿真中,将两级雾化喷嘴的速度场和水体积分数分布与单级雾化喷嘴的对应仿真结果分别进行对比,并优化了两级雾化喷嘴的结构参数。试验测量了DSM、喷雾速度、喷雾密度分布并和仿真结果进行对比验证。研究表明,优化设计后两级雾化喷嘴的喷雾保护半径为0.34 m,喷雾密度分布均匀;具有多喷嘴的两级雾化细水雾喷头的喷雾保护半径可以超过2 m,在消防领域具有实用价值。     

AG2.0型超声波蒸发传感器应用及检定方法研究

文章从AG2.0型超声波蒸发传感器的系统结构和工作原理出发,详细介绍了该传感器的测量环境和技术参数,分析了业务应用的正确方法。根据实际检定工作,研究了AG2.0型超声波蒸发传感器的检定方法,展示了蒸发传感器现场检定实例。结果表明:由于测量环境的改变,AG2.0型超声波蒸发传感器测得的蒸发水位比实际值偏小,需将蒸发水位订正1.019的系数;检定中,注意蒸发零位值、检定和数据处理方法的变化,避免引起检定结论误判。     

基于超声波传感器的无线液位测量系统

针对诸多行业储液罐液位测量的特点和技术要求,设计了一种基于超声波传感器的无线液位测量系统.系统由液位检测模块、无线数传模块和上位机工作站组成.传感器将接收到的信号经数据处理后由无线数传模块送上位机工作站,工作站是由VC设计的一个数据处理平台,具有多路液位显示、超限报警、数据存储和打印等功能.     

基于LabVIEW的超声波相关法流速流量测量仪

讨论和分析了相关法超声波流量计的测量原理和数学模型，据此完成了相关法超声波流速流量测量虚拟仪器系统的结构设计和基于Lab-VIEW的软件设计，通过对该系统进行软件模块测试和系统信号仿真实验，论证了将虚拟仪器技术应用于超声波相关法流量测量领域的可行性，在相关法超声波流量计的理论研究和实验开发上具有一定的应用价值。     

基于超声波传感器的风速风向测量研究

针对传统风速仪测量过程中存在精度差、稳定性低等一些问题,设计了一种基于超声波传感器的风向风速测量系统。硬件部分主要设计了超声波发射的DDS驱动电路、信号接收调理放大电路、滤波电路以及ARM控制电路等。系统采用CPLD和AD9754产生高精度的驱动信号,同时采用32位的ARM STM32实现对数据的处理以及外围通信的功能。实验结果表明,该系统在数据处理方面速度快,具有较高的稳定性和精确度,可以满足工程应用要求。     

An experimental study on the effect of square grooves on decay characteristics of a supersonic jet from a circular nozzle

In this experimental work, the effect of square grooves on the structure of a supersonic jet emanating from a circular nozzle has been investigated at three different nozzle inlet total pressures i.e 360 kPa, 550 kPa and 720 kPa. The nominal exit Mach number is 1.8. A new empirical relation for predicting the supersonic core length for grooved nozzle has been suggested. Further, a new parameter “groove effectiveness” has also been suggested to quantify the effect of the groove by using the total pressure data in the supersonic core length. Experimental results suggest that at higher nozzle inlet total pressure, the groove effectiveness plays a minor role. From the jet centreline total pressure data, supersonic core length, the locations at which 50 % and 90 % decay occurs have been obtained. It has been observed that higher groove effectiveness is associated with smaller values of supersonic core length, L_50% and L_90%. Schlieren images of the jet structure shows unsymmetrical shock pattern of jets emanating from a single grooved nozzle.     

An experimental study of supersonic dual coaxial free jet

A supersonic dual coaxial jet has been employed popularly for various industrial purposes, such as gasdynamic laser, supersonic ejector, noise control and enhancement of mixing. Detailed characteristics of supersonic dual coaxial jets issuing from an inner supersonic nozzle and outer sonic nozzles with various ejection angles are experimentally investigated. Three important parameters, such as pressure ratios of the inner and outer nozzles, and outer nozzle ejection angle, are chosen for a better understanding of jet structures in the present study. The results obtained from the present experimental study show that the Mach disk diameter becomes smaller, and the Mach disk moves toward the nozzle exit, and the length of the first shock cell decreases with the pressure ratio of the outer nozzle. It was also found that the highly underexpanded outer jet produces a new oblique shock wave, which makes jet structure much more complicated. On the other hand the outer jet ejection angle affects the structure of the inner jet structure less than the pressure ratio of the outer nozzle, relatively.     

An experimental study of the nozzle lip thickness effect on supersonic jet screech tones

It is well known that screech tones of supersonic jet are generated by a feedback loop driven by the instability waves. Near the nozzle lip where the supersonic jet mixing layer is receptive to external excitation, acoustic disturbances impinging on this area excite the instability waves. This fact implies that the nozzle lip thickness can influence the screech tones of supersonic jet. The objective of the present study is to experimentally investigate the effect of nozzle-lip thickness on screech tones of supersonic jets issuing from a convergent-divergent nozzle. A baffle plate was installed at the nozzle exit to change the nozzle-lip thickness. Detailed acoustic measurement and flow visualization were made to specify the screech tones. The results obtained obviously show that nozzle-lip thickness significantly affects the screech tones of supersonic jet, strongly depending on whether the jet at the nozzle exit is over-expanded or under-expanded.     

Experimental study on hysteresis phenomena of shock wave structure in an over-expanded axisymmetric jet

In recent studies on two-dimensional supersonic jets, it is reported that the hysteresis phenomenon for the reflection type of shock waves in the jet flow field is occurred under the quasi-steady flow condition and this phenomenon is affected by the transitional pressure ratio between the regular reflection and Mach reflection. However, so far, there are few researches on the hysteresis phenomenon for the transition of shock waves between regular and Mach reflection in over-expanded supersonic jets and the phenomenon has not been investigated satisfactorily. Therefore, the purpose of this study is to clarify the hysteresis phenomena for the reflection type of shock wave in the over-expanded axi-symmetric supersonic jet experimentally, and to discuss the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time. Furthermore, the effect of Mach number at the nozzle exit on hysteresis loop was investigated for two kinds of nozzle.     

A computational analysis of unsteady transonic/supersonic flows over backward facing step in air jet nozzle

A transonic/supersonic axisymmetric backward facing step nozzle flow in an air-jet loom has been analyzed numerically by using a time accurate characteristic based upwind flux difference splitting compressible Navier-Stokes method. The unsteady pressure and Mach number behavior along the center line of the main nozzle were analyzed by periodic inlet condition changes to simulate the intermittent flow inside main nozzle of an air-jet loom.     

收缩喷嘴内部流道型线对射流流场的影响

为研究收缩喷嘴内部流道形成对射流流场的气体动特性参数的影响，根据可压缩流体轴对称N-S方程，采用非结构网格和二阶精度的有限体积法，对不同内部流道形线的喷嘴自由射流进行数值模拟。亚声速射流采用RNGk-ε湍流模型，超声速射流采用S-A湍流模型，计算结果与实验较吻合。在亚声速流动中，收缩喷嘴的收缩角大小会影响其对射流的阻滞效果，内部流道形线设计为维多辛斯基曲线可以获得更好的流场动特性参数，有利于提高喷嘴的工作效率。在超声速流动中，喷嘴流道型线对出口膨胀波的角度与强弱影响较大，要根据射流的有效作用区域选择合适的喷嘴，才能使能量的损失最小。若要获得较佳的外部流场参数，优化喷嘴内部流道设计十分重要。     

Study on drug powder acceleration in a micro shock tube

Recently, micro shock tubes have been widely used in the medical engineering. The needle-free drug delivery device which mainly consists of a micro shock tube and an expanded nozzle has been produced to inject drug powders into human and animal bodies without any sharp metal needles. The drug powders were delivered by obtaining high momentum, which can be done by accelerating drug powders in the micro shock tube and supersonic nozzle. The particle-gas flows are induced by the incident shock wave developing by rupturing the diaphragm in the micro shock tube and again accelerated in the supersonic nozzle. The momentum of injected drug particles should be strictly controlled otherwise patients will suffer from skin injury or hurt. Even though micro shock tubes have been investigated in the past several decades, the detailed studies on particle-gas flows in the micro shock tube were rare to date due to the micro size and difficult experimental operation on micro shock tubes. In this paper, the experimental and numerical studies were carried out on investigating particle-gas flows in a designed micro shock tube. Particle tracking velocimetry (PTV) was performed to calculated particle average velocity at the exit of the supersonic nozzle. The nozzle flows were analyzed by obtaining instantaneous particle fields. The particle number density ratio was also investigated in the test section. The numerical simulations were performed by calculating unsteady Naver-Stokes equations on compressible flows and using fully implicit finite volume schemes. Discrete phase model (DPM) was used for simulating particle-gas flows in the micro shock tube. Particle diameter and density were varied to investigate their effects on the particle-gas flows. Unsteady particle-gas flows and shock wave propagation were obtained in details in the micro shock tube for present experimental and numerical studies.     

Li/Li2 supersonic nozzle beam

The characterization of a lithium supersonic nozzle beam has been made using spectroscopic techniques. It is found that at a stagnation pressure of 5.3 kPa (40 Torr) and a nozzle throat diameter of 0.4 mm the ground state vibrational population of Li(2) can be described by a Boltzmann distribution with T(v)= (195+/-30) K. The rotational temperature is found to be T(r)= (70+/-20) K by band shape analysis. Measurements by quadrupole mass spectrometer indicate that approximately 10-mol. % Li(2) dimers are present far downstream for an oven body temperature of 1370 K in the supersonic nozzle expansion. This measured mole fraction is in agreement with the existing dimerization theory.     

二维超音速喷管型线设计仿真研究

采用计算软件FLUENT,对四种经典收缩段型线下的流场特性进行数值模拟,为选择超声速风洞收缩段的型线提供依据。基于特征线理论,利用解析法完成超音速喷管膨胀段型线设计,通过分析总压恢复系数及均匀度等流场参数,确定型线膨胀角角度及喷管长度。结果表明,收缩段型线选用双三次曲线,膨胀角度3.5°的情况下,超音速喷管出口达到了设计要求马赫数,并获得了较好的气流品质。