首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到17条相似文献,搜索用时 125 毫秒
1.
水力空化是一种新型污水处理技术,但目前研究较多的孔板、文丘里管等简单的空化发生装置处理效果不甚理想。本文提出高压对冲空化射流强化有机物降解的概念,并开发了一种新型污水处理装置,并以含典型染料罗丹明B的废水降解为例,进行了系统实验研究.结果表明:高压对冲空化射流对含有罗丹B的废水有良好降解效果.单独采用高压对冲空化射流技术,罗丹明B降解过程符合一阶反应动力学特性,最优条件下罗丹明B降解率可达到71%.与单喷嘴射流相比,射流对冲作用可以将罗丹明B降解率提高1.3倍.对冲空化射流与过氧化氢氧化在罗丹明B降解过程中存在相互强化作用。高压对冲空化射流装置在能量利用率方面存在明显优势.本文的研究结果可为水力空化在污水处理领域的实际应用提供数据支撑.  相似文献   

2.
宝石喷嘴是影响超高压水射流切割系统工作效率的重要部件,而宝石内部的空化直接影响射流的形成,也是宝石磨损的重要原因之一。对400 MPa压力范围内宝石孔内部的空化两相流进行了数值模拟,阐述了射流在宝石内的形成过程,分析了长径比、压力和入口形状对宝石内空化的影响,并在相应压力下对宝石喷嘴的磨损进行了实验研究。结果表明:宝石内部的空化发展程度随着长径比的增大而减弱;在一定的长径比范围内,空化可以发展到喷嘴出口,并最终使射流的初始直径小于喷嘴直径,且在此条件下当压力升高时,射流的初始直径增大;良好的入口形线可以降低空化的发展程度;宝石入口的磨损较出口更显著,空蚀和高压水的冲蚀造成了宝石孔边缘形状的破坏,这种破坏随着压力的升高而加剧,选择合适的长径比是减少冲蚀磨损的有效途径。  相似文献   

3.
针对聚变堆第一壁钨材料的加工问题,开展前混合磨料射流切割钨试验,研究切面表面形貌,分析 射流压力和切割速度对切面粗糙度、切面光滑区深度的影响。结果表明:切割速度对粗糙度影响较大,减小切割 速度可以降低切面粗糙度;射流压力对粗糙度影响略小,提高射流压力可以增加切面光滑区深度,改善切面质量。 试验发现切面存在拖尾纹、残余楔角和冲蚀凹坑等现象,需要通过喷嘴角度补偿等方法予以抑制或消除,以提高 切面加工质量。  相似文献   

4.
采用自行设计的自激脉冲空化射流喷嘴和试验测试系统进行了一系列低压大流量空化射流试验,得到了一组喷嘴结构参数,使得喷嘴在入口压力为0.95~1.13 MPa时能产生较为明显的脉冲效果。通过试验获得了随入口压力升高腔室内部流场变化规律,并对试验中喷嘴腔室内部压力突降现象进行分析。试验表明自激脉冲空化射流的打击力是连续射流的1.3~1.6倍。  相似文献   

5.
本文对不同喷嘴组合方式时超高压射流井底流场特性进行数值模拟.根据得出的井底流场的速度矢量图和井底压力分布图,分析超高压钻头喷嘴组合形式对流场结构及钻进效果的影响.结果表明,三个垂直的边喷嘴组合破岩效率较高,但清洗井底效果不佳,冲蚀井壁严重;中心加一个喷嘴可解决清洗井底及冲蚀井壁的问题,但要求高压流体排量增加;两个垂直边...  相似文献   

6.
在超高压水射流切割过程中,射流结构是设备工作效率及损耗程度的决定性因素,本文针对400MPa范围内超高压水射流结构进行了数值模拟及实验研究,得到了相关因素对其具体影响。结果表明:超高压水射流的流束可分为几个特征各不相同的区域;射流的发散程度随着压力和宝石孔径的增大而增大;喷嘴形状对射流结构具有显著的影响,渐扩的锥形出口及倾斜的出口端面有助于增强射流的集束性;宝石孔内的空化直接影响了射流的形成;空化加剧了宝石的磨损,随着宝石孔入口的磨损程度提高,水射流趋于发散。  相似文献   

7.
叙述了喷射式制冷的研究意义;详细介绍了射流泵代替压缩机和节流装置的几种运用及其国内外发展现状;其中重点介绍了射流泵结构对其性能的影响。通过研究国内外的相关文献,主要从喷嘴、混合室、扩压室三方面进行综述,分析结果表明,喷嘴结构和混合室尺寸存在使射流泵性能最优的最佳值,两者对射流泵性能起着决定作用。  相似文献   

8.
两种喷嘴喷射性能的试验研究   总被引:2,自引:0,他引:2  
为比较自激振荡脉冲喷嘴和连续射流喷嘴的喷射性能,利用自行搭建的喷嘴性能测试装置对两种喷嘴的喷射性能进行了试验研究,实测了不同压力下两种喷嘴的时均喷液量,分析了不同口径的连续射流喷嘴和自激脉冲喷嘴的喷射特性,主要探讨了连续射流喷嘴、自激喷头下喷嘴直径对喷嘴喷液性能的影响,并进行了两种射流打击油泥样本的对比试验.试验结果表明,时均喷液特性相似的连续射流和脉冲射流在冲击油泥样本时,相同时间下脉冲射流的冲击破坏范围要大于连续射流,根据试验中油泥的屈服破坏过程,确定了射流有效打击力的临界值,建立射流清洗油泥时有效射程的经验估算式.  相似文献   

9.
为了提高射流抛光的加工效率,设计了一种矩形喷嘴结构,基于并行去除方式来提高工件的去除效率。根据流体力学基本理论,分析了矩形喷嘴冲击射流流场的结构特性,并对其流场分布进行了定量计算。基于射流去除理论,建立了矩形喷嘴的材料去除理论模型,并对去除量分布进行了计算与比较。详细分析了矩形喷嘴结构参数与去除量之间的关系,在此基础上对矩形喷嘴进行了优化,结果表明,矩形喷嘴长宽比控制在10左右能够得到很好的去除效果。  相似文献   

10.
空心旋转液体射流初始阶段特性的实验研究   总被引:1,自引:0,他引:1  
以空心旋转射流的理论模型为基础[1],通过实验对旋流喷嘴射流特性做进一步深入的研究,特别是实际射流形状的变化规律及喷嘴初始参数的变化规律.结果表明,旋流喷嘴的初始参数和空心射流内外表面压力差是决定射流形状的主要因素。  相似文献   

11.
In this paper, the cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating flow in a Venturi reactor are investigated experimentally under different cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale cavitation flow structure, is applied to investigate the choked cavitating flow dynamics. The POD results show that two mechanisms, re-entrant jet flow mechanism and shock wave mechanism, govern the shedding and collapse of cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various cavitation regions induced by the choked cavitating flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for cavitation applications such as water treatment.  相似文献   

12.
Traditional abrasive fluid jet polishing (FJP) is limited by its high-pressure equipment, unstable material removal rate, and applicability to ultra-smooth surfaces because of the evident air turbulence, fluid expansion, and a large polishing spot in high-pressure FJP. This paper presents a novel cavitation fluid jet polishing (CFJP) method and process based on FJP technology. It can implement high-efficiency polishing on small-scale surfaces in a low-pressure environment. CFJP uses the purposely designed polishing equipment with a sealed chamber, which can generate a cavitation effect in negative pressure environment. Moreover, the collapse of cavitation bubbles can spray out a high-energy microjet and shock wave to enhance the material removal. Its feasibility is verified through researching the flow behavior and the cavitation results of the negative pressure cavitation machining of pure water in reversing suction flow. The mechanism is analyzed through a computational fluid dynamics simulation. Thus, its cavitation and surface removal mechanisms in the vertical CFJP and inclined CFJP are studied. A series of polishing experiments on different materials and polishing parameters are conducted to validate its polishing performance compared with FJP. The maximum removal depth increases, and surface roughness gradually decreases with increasing negative outlet pressures. The surface becomes smooth with the increase of polishing time. The experimental results confirm that the CFJP process can realize a high material removal rate and smooth surface with low energy consumption in the low-pressure environment, together with compatible surface roughness to FJP.  相似文献   

13.
Water jets accelerated by differently configured convergent nozzles of diameters ranging from 4.5 to 5.0 mm are studied. The excess pressure at the nozzle inlet varies from 5 × 103 to 3.5 × 106 Pa. Velocity measurements are carried out with a spring dynamometer and a free-running Pelton microturbine. The jet strength at the outlet of the nozzle is found to increase by a factor of 4.0–4.5 compared with the water flow strength at the inlet, which depends on the excess pressure and volume flow at the inlet. Reasons for such an effect and a possible source of the additional energy are considered. The 2D Bernoulli equation used instead of the 1D equation routinely applied in nozzle analysis leads to a negative value of the excess pressure at the nozzle exit section and in the jet. Gas evolution and cavitation enhance this effect because of a decrease in the jet density. As a result, the jet is accelerated not only by the inlet pressure but also due to the fact that the potential energy of the flowing medium decreases because of a decrease in its absolute pressure down to the technical vacuum level. The contraction of the jet by the atmospheric air and the establishment of the equilibrium (in air) pressure in the water jet eventually raise its kinetic energy through the internal energy of the air.  相似文献   

14.
采用强脉冲激光器设计液体环境下刚性壁面空蚀实验平台,改变液体中含气量,利用高速相机观察不同含气量条件下激光空泡在壁面附近的脉动过程,并对刚性壁面造成的空蚀结果进行了观测。实验研究发现,随着液体中相对空气含量的提高,激光空泡脉动的最大尺寸增大,空泡的膨胀运动变剧烈,溃灭运动速度降低,空泡的溃灭强度降低,从而影响到溃灭冲击波和壁面微射流对刚性壁面的冲击速度,减弱了壁面空蚀,而液体中含气量的提高能够降低激光空泡对刚性壁面的空蚀程度。  相似文献   

15.
The present study numerically investigates liquid-jet characteristics of acoustic cavitation during emulsification in water/gallium/air and water/silicone oil/air systems. It is found that a high-speed liquid jet is generated when acoustic cavitation occurs near a minute droplet of one liquid in another. The velocity of liquid jet significantly depends on the ultrasonic pressure monotonically increasing as the pressure amplitude increases. Also, the initial distance between cavitation bubble and liquid droplet affects the jet velocity significantly. The results revealed that the velocity takes maximum values when the initial distance between the droplet and cavitation bubble is moderate. Surprisingly, the liquid jet direction was found to depend on the droplet properties. Specifically, the direction of liquid jet is toward the droplet in the case of water/gallium/air system, and vice versa the jet is directed from the droplet in the case of water/silicone oil/air system. The jet directionality can be explained by location of the high-pressure spot generated during the bubble contraction.  相似文献   

16.
An experimental investigation was conducted to study the mechanics of material removal in waterjet and abrasive waterjet (AWJ) piercing processes in a birefringent polymer material. A two-dimensional dynamic photoelasticity experimental set-up was developed and utilized to record the photoelastic stress patterns associated with jet piercing. The fringe patterns recorded by the high-speed camera were used to identify the transient stress fields adjacent to holes pierced. A comparative study of material-removal mechanisms with pure-waterjet and abrasive-waterjet impacting and piercing show that a waterjet contributes to the macrocraking and scooping action of that material, whereas an abrasive waterjet contributes to microcrack nucleation, micromachining, and subsequently erosion.  相似文献   

17.
Hydrodynamic cavitation (HC) in the Venturi nozzle, apart from the harmful influence on the devices, can be used to improve a range of industrial processes, such as biofuel generation, emulsion preparation, and wastewater treatment. The present investigation deals with the influence of dissolved air in Venturi cavitating flow based on numerical and experimental approaches. The experimental campaigns have been done in a closed-loop water tunnel equipped with a Venturi test section. The post-processing techniques such as Fast Fourier Transform (FFT), Power Spectral Density (PSD), temporal/spatial Grey Level distribution and mean value grey level distribution are employed to analyse the experimental observations and measurement. The URANS numerical method is modified based on the Density Corrected-Based Model (DCM) to be more adaptable for flows with high differences in density. The results approve the remarkable effect of dissolved air on the configuration of the cavity, its evolution process, and transient/averaged characteristics. It is observed that the incipient point and ratio of sheet cavity length to cloud cavity length are changed. Furthermore, the flow velocity inside of the sheet and cloud cavities is different; as well as, the higher content of dissolved air leads to slower flow velocity inside the cloud cavity. In addition, the shedding frequency is significantly reduced in case of higher level of air content.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号