共查询到18条相似文献,搜索用时 207 毫秒
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磨料射流在水利水电、石油工程和海洋资源开发等领域有着广泛的应用,研究射流的冲蚀特性和破坏物料机制对提高水射流利用效率具有重要意义。利用自行研制的实验装置,研究了围压条件下自振空化、文丘里和锥形3种喷嘴形成的磨料射流冲蚀特性,分析了空化磨料射流冲蚀物料的机制。结果表明:自振空化喷嘴和文丘里喷嘴的冲蚀效果优于锥形喷嘴,空化作用有助于提高磨料射流的冲蚀效果;磨料射流的冲蚀效率随围压的增大而降低,主要原因是围压对纯水射流和空化磨料射流的压力脉动和冲击力具有抑制作用。分析认为,空化磨料射流冲蚀破碎物料的机制主要包括冲蚀、气蚀和共混磨蚀3 种作用。 相似文献
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陈颂英胡涛曲延鹏曾兆强李文珂刘春武 《工程热物理学报》2014,(10):1964-1967
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
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自激脉冲射流喷嘴参数对装置能耗影响分析 总被引:2,自引:0,他引:2
为揭示喷嘴各参数变化对低压大流量自激振荡脉冲射流装置能耗的影响,本文借助数值模拟的方式,对自激振荡脉冲射流喷嘴的能耗问题进行了探讨,根据各结构参数和运行参数变化对腔内速度矢量场、腔内空化区形状即压力场、以及脉冲射流频率影响的分析结果,得到了如下论断:在合适的工况下,上喷嘴入口速度的降低将同比例降低下喷嘴出口的能量输出,上喷嘴压力提高与下喷嘴射流动能的增加成三倍关系.经过与试验结果对照,验证了这一结论,这一结果对于优化设计自激振荡脉冲射流喷嘴,指导自激喷嘴工业化设计具有重要的价值. 相似文献
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《低温与超导》2016,(2)
文章对采用两段式喷嘴的引射器及其两相流引射制冷系统在不同工况、不同几何尺寸条件下进行了实验研究。实验结果表明,在实验工况固定的条件下,采用两段式喷嘴的CO_2两相流引射制冷系统的COP随引射器第一喉部直径的增大而增大,引射比随第一喉部直径的增大而减小;系统COP和引射比随引射器中间连接直径的增大而减小。对于固定几何尺寸的引射器,系统COP随气冷器出口压力的升高而增大,引射比随气冷器出口压力的升高先减小后增大,在9MPa时引射比最小。与传统的CO_2制冷系统相比,采用两段式喷嘴的CO2两相流引射制冷系统的COP在不同工况的条件下均高于传统系统的COP,最大可提高约15%。 相似文献
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An experimental study of the generation of pressure fluctuations in a well acoustic emitter with nozzles of various shapes has been carried out. The effect of a smooth nozzle inlet section on the generation amplitude, the optimum jet length, and the outlet diameter has been studied. The formation of a region of reverse currents connecting to the cavity in the nozzle between the channel wall and the jet periphery has been considered. A significant increase in the generation amplitude produced at the smooth nozzle inlet and the formation of a uniform velocity profile in the nozzle channel have been observed. 相似文献
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L. S. Kotousov 《Technical Physics》2005,50(9):1112-1118
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
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The near flow field of small aspect ratio elliptic turbulent free jets (issuing from nozzle and orifice) was experimentally
studied using a 2D PIV Two point velocity correla tions in these jets revealed the extent and orientation of the large scale
structures in th e major and minor planes. The spatial filtering of the instantaneous velocity field using Gaussian convolution
kernel shows that while a single large vortex ring circumscribing the jet seems to be present at the exit of nozzle, the orifice
jet exhibited a number of smaller vortex ring pairs close to jet exit. The smaller length scale observed in the case of the
orifice jet is rep resentative of the smaller azimuthal vor tex rings that generate axial vortex field as they are convected.
This results in the axis-switching in th e case of orifice jet and may have a mechanism differ ent from the self induction
process as observed in the case of contoured nozzle jet flow. 相似文献
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以水为介质,建立了液体流动的混合物多相流模型及空化模型,运用CFD方法对水平圆管内伴随有水力空化现象的受迫对流换热过程进行了数值研究,详细分析了管道入口压力、入口温度和限流孔与管道直径比等因素对水力空化及对流换热过程的影响规律。数值模拟结果表明,空化现象出现在圆管喉部(限流孔)壁面附近区域;与相同流量下无空化时的传热相比,在发生空化现象的区域,传热壁面被蒸汽所覆盖导致传热急剧恶化,而在远离空化发生区域的下游位置,由于空化的扰流作用使得加热壁面与流体之间的传热得到明显改善。 相似文献
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The present study investigates the effects of the orifice nozzle number and the inlet pressure experimentally on the cooling performance of the counter flow-type vortex tube. The energy generation has been conducted using a stream-tek generator (model GNMD-KIT) with different numbers of nozzles (2, 3, and 6), an aspect ratio of 1:6, and an inner diameter of 7.5 mm. In the experiments, for each of the orifices, inlet pressures have been adjusted from 200–600 kPa. The energy separation investigated here focuses on the cold temperature difference and coefficient of performance for cooling. The experimental results concluded in this article prove that the greatest effect of nozzle number is for three nozzles, and hence, that nozzle number could affect the energy separation efficiently. A comparison of the present experiments with other published works has been conducted. An analytical study of the characteristics equation has been carried out to evaluate the best correlation of the ratio of cold temperature difference to the inlet temperature as a function of pressure, cold mass fraction, and nozzle number. 相似文献
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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