Experimental investigation of liquid jet injection into Mach 6 hypersonic crossflow

The injection of a liquid jet into a crossing Mach 6 air flow is investigated. Experiments were conducted on a sharp leading edge flat plate with flush mounted injectors. Water jets were introduced through different nozzle shapes at relevant jet-to-air momentum–flux ratios. Sufficient temporal resolution to capture small scale effects was obtained by high-speed recording, while directional illumination allowed variation in field of view. Shock pattern and flow topology were visualized by Schlieren-technique. Correlations are proposed on relating water jet penetration height and lateral extension with the injection ratio and orifice diameter for circular injector jets. Penetration height and lateral extension are compared for different injector shapes at relevant jet-to-air momentum–flux ratios showing that penetration height and lateral extension decrease and increase, respectively, with injector’s aspect ratio. Probability density function analysis has shown that the mixing of the jet with the crossflow is completed at a distance of x/d _j  ~ 40, independent of the momentum–flux ratio. Mean velocity profiles related with the liquid jet have been extracted by means of an ensemble correlation PIV algorithm. Finally, frequency analyses of the jet breakup and fluctuating shock pattern are performed using a Fast Fourier algorithm and characteristic Strouhal numbers of St = 0.18 for the liquid jet breakup and of St = 0.011 for the separation shock fluctuation are obtained.     

Initiation of cavitation by injection of hot steam into a cold liquid jet

The problem of the dynamics of a hot steam bubble in the nonuniform flowfield of a plane cold liquid jet is considered. The motion of the bubble along the symmetry axis is analyzed with allowance for nonequilibrium condensation and heat conduction by the steam and the liquid. The domain of jet and steam parameters corresponding to the dynamic cavitation bubble initiation mode, is evaluated.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 91–100, September–October, 1995.     

Experimental analysis of volatile liquid injection into a fluidized bed

Experiments were conducted on a lab-scale fluidized bed to study the distribution of liquid ethanol injected into fluidized catalyst particles. Electrical capacitance measurements were used to study the liquid distribution inside the bed, and a new method was developed to determine the liquid content inside fluidized beds of fluid catalytic cracking particles. The results shed light on the complex liquid injection region and reveal the strong effect of superficial gas velocity on liquid distribution inside the fluidized bed, which is also affected by the imbibition of liquid inside particle pores. Particle internal porosity was found to play a major role when the changing mass of liquid in the bed was monitored. The results also showed that the duration of liquid injection affected liquid–solid contact inside the bed and that liquid–solid mixing was not homogeneous during the limited liquid injection time.     

脉冲液体射流泵能量平衡试验研究

根据脉冲液体射流泵主要流动部件的能量损失压力比,对其能量平衡进行试验,研究了主要过流部件的能量转化与脉冲频率之间的关系。与恒定液体射流泵试验数据进行对比,证明了脉冲频率、脉冲装置对脉冲液体射流泵的主要流动部件的能量损失压力比有一定的影响;且脉冲射流是提高射流泵传能及传质效率的有效途径。     

Experimental investigation of inclined liquid water jet flow onto vertically located superhydrophobic surfaces

In this study, the behaviour of an inclined water jet, which is impinged onto hydrophobic and superhydrophobic surfaces, has been investigated experimentally. Water jet was impinged with different inclination angles (15°–45°) onto five different hydrophobic surfaces made of rough polymer, which were held vertically. The water contact angles on these surfaces were measured as 102°, 112°, 123°, 145° and 167° showing that the last surface was superhydrophobic. Two different nozzles with 1.75 and 4 mm in diameters were used to create the water jet. Water jet velocity was within the range of 0.5–5 m/s, thus the Weber number varied from 5 to 650 and Reynolds number from 500 to 8,000 during the experiments. Hydrophobic surfaces reflected the liquid jet depending on the surface contact angle, jet inclination angle and the Weber number. The variation of the reflection angle with the Weber number showed a maximum value for a constant jet angle. The maximum value of the reflection angle was nearly equal to half of the jet angle. It was determined that the viscous drag decreases as the contact angle of the hydrophobic surface increases. The drag force on the wall is reduced dramatically with superhydrophobic surfaces. The amount of reduction of the average shear stress on the wall was about 40%, when the contact angle of the surface was increased from 145° to 167°. The area of the spreading water layer decreased as the contact angle of the surface increased and as the jet inclination angle, Weber number and Reynolds number decreased.     

Experimental investigation of liquid jet outflow into a plane ventilated channel in self-oscillatory regimes

The results of an experimental investigation of self-oscillatory jet outflow into a plane channel with air injection in its dead-ended part are presented. It is found that at fixed channel geometry and water supply system the main flow parameters depend on the air injection rate and the relative cavity volume. It is shown that with increase in the gas injection at a fixed cavity volume the self-oscillation intensity monotonically increases and the oscillations considerably change in nature, whereas the Strouhal number varies only slightly. At a fixed air injection coefficient the self-oscillation amplitude decreases with increase in the cavity volume and the self-oscillations stop at a certain threshold value. The flow pattern evolution with increase in the injection coefficient is studied in detail using high-speed filming. The developed surge flow pattern is described in detail.     

Experimental investigation flow structure and hydraulic resistance of a cylindrical duct with injection a fan slot jet

The paper describes results of an experimental study of pressure and velocity fields arising during normal injection of a radial slot jet into ducted flow. The experiments were carried out for slots of two different widths and for injection parameters varying in a broad range. The pressure profile along the duct length plotted in generalized coordinates was found to be quite a universal distribution. Experimental correlations for the minimum rarefaction in the separation region behind the injected jet were obtained, and comparison was made with the results of simplest numerical analysis. Results of measurements of local hydraulic losses are presented for the duct section where the normal injection of the slot jet was organized. The experimental data are shown to be underestimated compared with the results predicted by the theory of perfect mixing for a ducted flow with mass supply. The possible reasons of hydraulic losses coefficient behavior are discussed.     

N2双流体细水雾抑制管道瓦斯爆炸实验研究

为了在较低压力下获得较小粒径的细水雾,降低喷雾抑爆系统的运行成本,提高系统的适用性和抑爆效率,自行搭建了尺寸为120 mm×120 mm×840 mm的透明有机玻璃瓦斯爆炸管道实验平台。采用双流体喷嘴将N₂和细水雾送入试验管道,通过调节喷雾压力和喷雾时间开展了双流体细水雾抑制瓦斯爆炸实验研究,从火焰速度、瓦斯爆炸超压2个方面探讨双流体细水雾的抑爆有效性。实验结果表明:N₂双流体细水雾抑爆效果明显,可以减小瓦斯爆炸强度;随着喷雾时间的延长,爆炸火焰的速度峰值逐渐下降,爆炸超压峰值逐渐下降,平均升压速率逐渐降低;当N₂压力为0.4 MPa、喷雾时间为3 s时,速度峰值比不喷雾时下降60.39%,爆炸超压峰值下降37.76%。     

Optimal penetration of a liquid jet into an obstacle

The velocity distribution and cross-sectional area along a jet which will assure maximum depth of penetration are found for a given jet energy within the framework of the hydrodynamic theory of liquid jet penetration into an obstacle. Also found is the velocity distribution along the jet which will assure ultimate tension of its elements upon approaching the obstacle. The possibility is exhibited of applying the theory elucidated to construct cumulative charges with elevated punch-through capacity.     

近场水下爆炸气泡脉动及水射流的实验与数值模拟研究

海上作战时,近场水下爆炸形成的水射流能造成水面舰船结构的严重局部毁伤。为了研究近场爆炸时舰船底部水射流的形成机理及规律,开展了TNT当量2.5 g的炸药在固支方板底部不同爆距下起爆的水下爆炸实验。结果表明,气泡坍塌形成水射流的过程随着爆距的增加由吸附式向非吸附式转化。接着,基于ABAQUS软件采用CEL方法开展了系列数值模拟,结果表明:爆距在0.821～0.867倍最大气泡半径时,存在吸附式射流向非吸附式射流转化的临界点;固支方板加快了气泡坍塌的进程,炸药与钢板间的距离越小则射流形成的时间越早;射流形成过程中最大速度和射流击中钢板时速度均随着爆距的增大先增大后减小,并在临界点附近达到最大值,射流速度最大可达621 m/s,射流击中钢板时速度最大可达269 m/s。最后,给出了射流开始形成时间、射流最大速度、射流最大速度出现时间、射流击中钢板速度和射流击中钢板时间与距离参数的函数关系式。     

球体入水空泡演变和运动特性影响试验研究

为了探究表面粗糙度对球体入水空泡演变及运动特性的影响,基于实验室开放水槽试验系统,选取了5种表面粗糙度的球体,使用高速摄像机记录入水过程,并得到了各个球体的入水空泡、喷溅的演变过程以及运动特性的变化。发现入水空泡和喷溅的闭合都会给球体一个负方向的加速度。通过对比不同表面粗糙度球体的位移、速度、加速度曲线,发现表面粗糙度最大的球体在砰击阶段结束后,其速度会明显小于其他球体,并且表面粗糙度对球体运动的影响主要体现在入水早期。分析了上述各球体的入水空泡闭合后,与自由面相连的空泡的收缩运动,发现其收缩速度和加速度曲线均会出现极大值点,呈现出球体表面粗糙度越大出现得越早的趋势。

     

Experimental study on turbulent natural convection heat transfer in water with sub-millimeter-bubble injection

Using thermocouples and a particle tracking velocimetry technique, temperature and velocity measurements are conducted to investigate flow and heat transfer characteristics of turbulent natural convection from a vertical heated plate in water with sub-millimeter-bubble injection. Hydrogen-bubbles generated by the electrolysis of water are used as the sub-millimeter-bubbles. In the turbulent region, the heat transfer deterioration occurs for a bubble flow rate Q = 33 mm³/s, while the heat transfer enhancement occurs for Q = 56 mm³/s. Temperature and velocity measurements suggest that the former is caused by a delay of the transition due to the bubble-induced upward flow. On the other hand, the latter is mainly due to two factors: one is the enhancement of the rotation of eddies in the outer layer, and the other is the increase in the gradient of the streamwise liquid velocity at the heated wall. These are caused by bubbles, which are located in the inner layer, rising at high speed.     

用于爆轰驱动的射流起爆实验研究

爆轰驱动激波风洞的自由来流模拟范围与驱动气体的爆轰极限密切相关,爆轰极限越宽则模拟范围越大。驱动气体一般是通过点火管进行起爆的,提高点火管的起爆能力可以拓宽爆轰极限。为了提高点火管起爆能力,就点火管口径、点火气体爆轰敏感性和单/双点火管3种因素的影响进行了实验研究。在不同的点火管初始条件下,对驱动段波速进行了测量。结论如下:(1)提高点火管口径可以显著提升起爆能力;(2)点火气体爆轰敏感性对起爆能力有影响,点火管为缩径内型面时,低敏感性气体起爆能力更强,点火管为等径内型面时则低敏感性气体和高敏感性气体的起爆能力大体持平;(3)在保证射流同步的前提下,双点火管能够提高起爆能力,为保证射流同步性需使用化学恰当比的氢氧混气等爆轰敏感性强的点火气体。     

An experimental study of steam injection into a uniform water flow through porous media

An experimental study of steam injection into a porous media was carried out in a 2-dimensional plane porous channel. The steam was injected into a uniform downward water flow in a vertically aligned porous channel. The steam-water interface was carefully observed to understand the underlying physics. Two steam injection rate bounds were found for a given water flow rate and water subcooling. The upper bound is the steam flow rate at which the steam zone grows without limit and the lower bound is the steam flow rate at which a steam zone is just initiated. The bounds were determined experimentally for a porous channel with different permeabilities and thermal conductivities. For large particle size, chaotic oscillation of steam water interface was observed. The oscillation is believed to enhance heat and momentum transfer mechanisms. The steam zone size and shape were measured to evaluate heat transfer characteristics. The average Nusselt number is presented in terms of steam and water Reynolds numbers and the Stefan number.     

Mixing of gases due to injection of a low-pressure jet into a cross-flow

A gas jet injected into a channel is simulated numerically. The dependence of the mixing efficiency on the injection orifice aspect ratio, jet screening, and the ratio of the injected and channel gas densities is established. The mixing efficiency is estimated in terms of the mean concentration across the jet.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 67–74, May–June, 1996.     

Experimental investigation of over-expanded supersonic steam jet submerged in quiescent water

This study was designed to determine the behaviour of an over-expanded supersonic steam jet in quiescent water. Only two shapes of steam plume were observed and an analytical model was constructed. The axial and radial temperature distributions were measured in the steam plume and in the surrounding water. The flow pattern and temperature distributions were influenced mainly by steam mass flux and water temperature. The results confirmed the occurrence of compression and expansion waves in the steam plume, and indicated that the temperature distributions reflected the steam plume shapes. The axial temperature distributions in the forepart of the steam plume were independent of water temperature. Empirical correlations were found that predicted the dimensionless axial and radial temperatures of the turbulent jet region. Moreover, prediction of the steam plume length by the dimensionless axial temperature showed good agreement with the experimental results.     

Interfacial structure in an air–water planar bubble jet

The objective of the current study is to better understand the interfacial structure and its development in an air–water planar bubble jet, as well as to provide a unique benchmark data set for a 3D thermal-hydraulic analysis code. Both flow visualization and local measurements were performed in three characteristic flow conditions at four elevations along a test section with a cross section of 200 mm in width and 10 mm in gap. A high-speed digital video camera was applied in the flow visualization study to capture the flow structures and bubble interaction phenomena, while a miniaturized four-sensor conductivity probe was used to acquire the time-averaged local void fraction, interfacial velocity, and bubble number frequency. Also, the interfacial area concentration and the averaged bubble Sauter mean diameter were obtained from the local measurements. The lateral bubble transport and bubble interaction mechanisms were clearly demonstrated in the acquired data.