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。     

流化床撞击流气流粉碎机拉瓦尔喷管研究

流化床撞击流气流粉碎是对矿物进行超细粉碎的重要方法,喷管是其最关键部件之一.根据流体力学理论对流化床气流粉碎喷管进行了研究,提出了轴对称撞击流速度势函数表达式和喷管直径变化方程,并根据相关理论对超声速拉瓦尔喷管进行了设计和制造.实验证明,采用该喷管对煤进行超细粉碎,在喷管入口压力为0.7 Mpa～1.0 Mpa、转速分级轮转速＞2400r/min条件下,粉碎产品中以粒径小于2 μm的颗粒为主,对煤具有良好的超细粉碎效果.     

流化床撞击流气流粉碎机拉瓦尔喷管研究

流化床撞击流气流粉碎是对矿物进行超细粉碎的重要方法，喷管是其最关键部件之一。根据流体力学理论对流化床气流粉碎喷管进行了研究，提出了轴对称撞击流速度势函数表达式和喷管直径变化方程，并根据相关理论对超声速拉瓦尔喷管进行了设计和制造。实验证明，采用该喷管对煤进行超细粉碎，在喷管人口压力为0．7MPa～1．0MPa、转速分级轮转速〉2400r／min条件下，粉碎产品中以粒径小于2μm的颗粒为主，对煤具有良好的超细粉碎效果。     

低比转速离心泵叶轮叶片型线的拟合研究

现有的离心泵叶轮叶片型线设计方法复杂烦琐,且叶片型线没有具体的方程形式,难以对叶片型线进行调整.通过对由传统方法所设计的叶片型线进行多种多项式曲线和指数曲线拟合,比较各种曲线的拟合精度,结果表明：指数曲线适合于叶片型线,其拟合最大相对偏差0.95％,满足工程需求;实现采用指数曲线对叶片型线进行设计,保证型线过渡光滑,且便于叶片结构参数修改和叶片型线局部调整.     

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。     

气动热环境下喷管射流流场模拟

采用Witoszynski、Foelsch法及边界层修正量等因素对(4～6)马赫喷管型线进行设计,将所设计喷管射流及实验区流场环境进行模拟;通过改变喷管实验区入出口压力比,探讨最佳稳定流场时所对应的入出口压力比。为明确风洞实验中构件附近流场的准确分布,在实验区放置球锥模型,对比分析所设计喷管射流场及远场边界条件下的流场品质,探究实验区壁面及喷管模型对稳定气流的影响大小。同时,分析球锥构件半锥角的改变对喷管实验区射流的影响。研究结果表明:所设计喷管及实验区的流场都能保证高马赫、高品质稳定气流,验证了喷管型线设计的合理;两种环境下球锥模型附近的速度场、温度场及压力场分布差异明显,实现后续模拟构件在风洞实验的高温应变及模态等特性的结果更精确;喷管实验区流场中不同半锥角的构件温度分布规律结果对飞行器头部热防护的措施可提供理论参考。     

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。     

某风洞半柔壁喷管电液伺服系统设计

在跨超声速风洞中,喷管是保证试验段获得设计马赫数均匀气流的重要部件。与固块喷管相比,柔壁喷管可在执行机构驱动下连续调节型面,不仅可以缩短不同型面之间的调整时间,还可以在风洞运行中开展连续变马赫数试验。该文分析比较了柔壁喷管型面执行机构不同驱动方式的特点,针对国内首套全伺服液压缸驱动的半柔壁喷管,开展了液压伺服系统和电气控制系统设计,包括液压动力元件配置、恒压油源设计、电气控制系统方案。采用非对称阀控非对称缸技术、同步并联远程恒压供油技术、基于带轴控制器的数字伺服比例阀的分布式控制技术,以满足多液压轴柔壁喷管控制系统的需要。     

基于FLUENT的火箭发动机喷管流场数值模拟

根据火箭发动机喷管设计要求及限制条件,给出喷管型面设计方法。采用计算流体力学(CFD)方法,用单方程(Spalart—Allmaras)湍流模型,借助FLUENT软件对喷管在主要工作状况下的流场特征进行了数值模拟,得到了喷管壁面上的马赫数分布图、压强分布图、流线分布图等计算结果,并对其进行了分析和总结。为固体火箭发动机喷管的设计与研究提供有效参考。     

基于B样条曲线的双螺杆压缩机转子型线设计

为了克服双螺杆压缩机转子型线设计中型线参数调整不便等缺点,利用自由曲线易于修改的优点,提出将三次B样条曲线作为转子组成齿曲线设计性能更优的转子型线的设计方法。分别对新设计的转子型线和GHH型线所构成的压缩机内部流场进行CFD仿真分析,结果表明:在相同条件下,运用三次B样条曲线设计的压缩机横向泄露更小,出口压力更高。最后通过实验验证了模拟仿真结果的有效性,说明将自由曲线引入到转子型线设计中有助于拓宽转子齿曲线的组成形式和设计高效型线。     

Transitional behavior of a supersonic flow in a two-dimensional diffuser

Two-dimensional blow-down type supersonic wind tunnel was designed and built to investigate the transient behavior of the startup of a supersonic flow from rest. The contour of the divergent part of the nozzle was determined by the MOC calculation. The converging part of the nozzle, upstream of the throat was contoured to make the flow profile uniform at the throat. The flow characteristics of the steady supersonic condition were visualized using the highspeed schlieren photography. The Mach number was evaluated from the oblique shock wave angle on a sharp wedge with half angle of 5 degree. The measured Mach number was 2.4 and was slightly less than the value predicted by the design calculation. The initial transient behavior of the nozzle was recorded by a high-speed digital video camera with schlieren technique. The measured transition time from standstill to a steady supersonic flow was estimated by analyzing the serial images. Typical transition time was approximately O.1sec.     

Optimal design of supersonic nozzle contour for altitude test facility

This paper develops a robust and practical design for supersonic nozzles to be used in an altitude engine test facility. Although many studies have been conducted on nozzle design, none of these present a robust yet practical and simple method for designing supersonic nozzles. This research attempts to develop such design for supersonic nozzles by combining method of characteristics (MOC), optimization algorithm, and computational fluid dynamics analysis for design verification. Preliminary design optimal techniques were adopted to reduce nozzle length while keeping the exit area constant in the design. Optimization produced a smooth flow by generating a parallel and uniform flow at the exit. A two-dimensional model was initially used because of the axisymmetrical characteristic of the flow in this study. The optimal nozzle was designed for the operation of a test facility at Mach number 2.3 and altitude of 7 km. The optimal design produced a uniform and parallel flow at the given test condition.     

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.     

缩扩型超音速喷管的设计与仿真

缩扩型的拉瓦尔喷管可以使通过其的气流获得超音速,出口速度的大小以及气流是否稳定是决定拉瓦尔喷管性能优劣的关键因素.通过Fluent软件对拉瓦尔喷管的相关流场进行了数值仿真,分析了入口压力、面积比、收缩段型面及扩张段的锥角对喷管出流速度的影响,可为喷嘴的设计提供理论指导.     

The TTP Transonic wind tunnel Mach number uniformity analysis

The distribution of the Mach number in the test section of the Brazilian Pilot Transonic Wind Tunnel was evaluated for the subsonic, transonic and low supersonic regimes. A convergent–divergent nozzle was designed and manufactured to increase the TTP envelope up to Mach number 1.3. Static and total pressures of the airflow are input quantities for the isentropic equation used for Mach number estimation. Static pressure measurements at the test section stations are accomplished by a centreline pressure probe and by distributing pressure taps along the upper and lower walls. Data reduction includes the evaluation of the uncertainties associated with the measured quantities, as well as their propagation to the output quantity, by employing the Monte Carlo method. Least squares fitting is applied to the experimental data in order to supply Mach number calibration curves. Sources of error causing non-uniform flow for Mach number equal to 1.3 are pointed out.     

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.     

The effect of the secondary annular stream on supersonic jet

The present study addresses an experimental investigation of the near field flow structures of supersonic, dual, coaxial, free, jet, which is discharged from the coaxial annular nozzle. The secondary stream is made from the annular nozzle of a design Mach number of 1.0 and the primary inner stream from a convergent-divergent nozzle. The objective of the present study is to investigate the interactions between the secondary stream and inner supersonic jets. The resulting flow fields are quantified by pitot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the primary jet are varied to obtain over-expanded flows and moderately under-expanded flows at the exit of the coaxial nozzle. The pressure ratio of the secondary annular stream is varied between 1.0 and 4.0. The results show that the secondary annular stream significantly changes the Mach disc diameter and location, and the impact pressure distributions. The effects of the secondary annular stream on the primary supersonic jet flow are strongly dependent on whether the primary jet is underexpanded or over-expanded at the exit of the coaxial nozzle.     

一种可调叶片喷嘴结构设计与性能分析

通过跨音速喷嘴内流动机理的分析,针对某中低温地热能发电系统中透平膨胀机的运行条件,设计了与之匹配的叶片喷嘴,提出了一种新颖的叶片喷嘴调节结构形式.采用数值计算方法,研究叶片不同头部型线和不同喉部位置对喷嘴内流动及其性能的影响以适应调节机构的要求.研究结果表明:在满足工程设计要求的前提下,头部型线及喉部位置对叶片喷嘴气动性能的影响都比较小,改型后的直线圆弧型跨音速可调叶片喷嘴具有良好的变工况性能.     

气溶性射流对钢板污垢清洗的应用研究

为了获得更好的清洗效果和节能环保,提出了一种新型的射流方式——气溶性射流。基于流体力学和气溶性射流的工作原理,根据气溶性射流的特性和喷嘴的几何特征,研究了气液相的流动特性方程,得到了气溶性射流的速度分布规律。利用自行设计的超音速喷嘴组装的带电气溶性射流实验装置对钢板进行清洗,经简易检测表明：气溶性射流喷嘴产生的超音速极大地提高了洗涤效率,与同流量的喷嘴相比,效率提高近10倍,具有广泛的应用前景。