共查询到20条相似文献，搜索用时 15 毫秒
1.
Reaction thrust of water jet for conical nozzles 总被引：1，自引：0，他引：1
Clear knowledge on the reaction thrust of water jet is valuable for better design of water jet propulsion system. In
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions． 相似文献
this paper, theoretical, numerical and experimental studies were carried out to investigate the effects of the nozzle geometry
as well as the inlet conditions on the reaction thrust of water jet. Comparison analyses reveal that the reaction thrust has a
direct proportional relationship with the product of the inlet pressure, the square of flow rate and two-thirds power exponent
of the input power. The results also indicate that the diameter of the cylinder column for the conical nozzle has great influence
on the reaction thrust characteristics. In addition, the best values of the half cone angle and the cylinder column length exist
to make the reaction thrust reach its maximum under the same inlet conditions． 相似文献
2.
为研究微小孔径气体受限冲击射流的换热特性,采用电阻丝加热方形酚醛树脂薄板作为模拟发热芯片的换热表面,沿对角线均匀布置热电偶以采集表面温度分布。以3mm孔径的圆形单孔及1mm孔径两种不同排列的圆形多孔喷射板对发热面进行中低Re数的射流冲击换热实验．通过改变风数及高度孔径比等参数得到了批数的径向分布及驻点区的换热特性,为射流冲击换热在封装芯片冷却上的应用提供了实验基础。 相似文献
3.
喷嘴是水射流切割系统的关键元件，通过研究一级喷嘴直径、二级喷嘴直径、混合腔直径和喉管距、系统工作压力、磨料直径大小等对轴向射流速度的影响，为水切割喷嘴的优化设计奠定了基础，其结果可为高压水切割工具的设计提供参考依据。 相似文献
4.
70t底吹氩钢包水模型实验 总被引：1，自引：0，他引：1
针对某钢厂70 t底吹氩钢包进行水模型实验,通过测定不同吹气量下的混匀时间来优化其最佳喷吹位置及示踪剂最佳加入位置;卷渣模拟实验来确定临界卷渣喷吹量。实验研究表明,最佳喷吹位置为原孔及与原孔成180°方向上0.6R处双吹,该喷吹方式下示踪剂最佳加入位置为钢包中心;单吹临界卷渣吹气量为270 L/m in,双吹临界卷渣吹气量为320 L/m in。 相似文献
5.
With the development of ski-jump energy dissipation for high and large discharge among the hydraulic projects, the effects of characteristics of water flow on energy dissipation are increasingly important. In the present study, the effects of aeration and the initial water thickness on axial velocity attenuation of jet flow were analyzed, using variance analysis and numerical calculated methods. From the analysis of test data, both of the air concentration and initial water thickness are sensitive factors for the axial velocity attenuation of jet flow along the axial way, and there is no significant interaction effect between the aeration and initial water thickness. Aeration has a more significant effect on the axial velocity attenuation of jet flow. Decreasing the initial water thickness of jet flow can reduce the length of jet core, and make the initial position of axial velocity attenuation closer to the nozzle exit. The numerical calculation results show that aeration can contribute to the enhancement of entrainment ability of jet flow, which may improve the interaction between jet flow and surroundings. For ski-jump energy dissipation among the hydraulic projects, combining aeration with decreasing initial water thickness of jet flow is an effective way to enhance the rate of axial velocity attenuation. 相似文献
6.
Aiming at the problem of air-cooled condenser output limit,a spray humidification system was presented to reduce the inlet air temperature.The pressure atomizing nozzle TF8 was chosen for inlet air spr... 相似文献
7.
Simulation investigation on fluid characteristics of the water hydraulic jet pipe servo valve (WHJPSV) is conducted through a commercial computational fluid dynamics (CFD) software package FLUENT. In particular, the factors to fluid characteristics of WHJPSV are addressed, which include diameter combination of jet pipe and receiver pipe, jet pipe nozzle clearance, angle between two jet receiver pipes and deflection angle of the jet pipe. It is concluded from the results that: (i) Structural parameters have ... 相似文献
8.
卢义玉 《重庆大学学报(英文版)》2002,1(1):11-15
A new type jet, the oscillating & deflecting jet, is put forward and its oscillating and deflecting characteristics are investigated. The nozzle of the self-oscillating & deflecting water jet consists of an upstream nozzle, a downstream nozzle, an oscillating chamber and two switches. It is experimentally shown that the deflective angle may reach 9.53 degree. The generated pressure fluctuation is very regular and the jet can efficiently increase the ability for breaking and cutting by eliminating the water cushion effect associated with a continuous jet. 相似文献
9.
前混合水射流喷丸强化表面粗糙度预测 总被引：1，自引：0，他引：1
选择对喷丸表面粗糙度起主要影响作用的喷丸压力、喷嘴扫描速度和靶距3个因素,各6个水平,选用直径为0.25 mm的玻璃弹丸,应用前混合水射流对2A11铝合金进行喷丸试验;采用针描法和SJ-201 Surface Roughness Tester测量喷丸表面粗糙度;基于表面粗糙度试验数据,应用多元线性回归和多项式回归分析方法建立喷丸表面粗糙度数学模型,并将模型应用于喷丸表面粗糙度预测,研究表明:多元线性回归预测模型,计算精度高、泛化能力强、预测效果好,平均相对误差为13.37％,能够满足工业生产对喷丸表面粗糙度预测精度的要求,具有较大的实用价值. 相似文献
10.
Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes
(CNTs) have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical
property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper,
an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used
as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid
dynamics (CFD) simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size
and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the micro-pin-fin heat
sink were obtained, and the heat removal efficiency was evaluated. 相似文献
11.
Flow visualization and hot-wire measurement techniques were combined to investigate the influence of the size and number of tabs on jet flow field and vortex structure generation mechanism. Streamwise vortices generated by the tabs of different sizes and numbers were ob- served from the flow visualization images. Combined with flow visualization, hot-wire measurement gave a quantitative insight of the effect of various tabbed jet flows. Instantaneous two-component velocity signals （longitudinal and transverse velocity components） at different cross sections along radius direction and streamwise direction with different tabbed jet nozzles were measured using hot-wire anemometer. Average flow field parameters of tabbed jet flow such as mean velocity, turbulence intensity, vorticity were analyzed and the effects of tabs with different sizes and numbers were compared with that of circular no-tab jet flow. It is revealed that the generation of a series of counter-rotating quasi-streamwise vortices, azimuthal vortices and double-row azi-muthal vortex are the reasons for mixing enhancement of tabbed turbulent jet flow. 相似文献
12.
雾化喷嘴在工业喷淋塔内起重要作用,雾化的优劣直接影响烟气净化效率和填料表面的利用率。试验采用喷淋强度试验装置,对旋流式压力雾化喷嘴的不同条件下喷淋强度进行了系统研究,探讨了其影响因素,并建立了液雾流场分布函数表达式,为烟气净化中旋流喷嘴的设计提供依据。 相似文献
13.
INTRODUCTION The use of dimethyl ether (DME) as an alterna-tive fuel appears to be a promising approach for si-multaneously minimizing NOx and soot emissionfrom conventional diesel engines. The lowself-ignition temperature of 508 K and the high oxy-gen content of 34.8 percent (mass fraction) are twomajor factors characterizing low soot and unburnedtotal hydrocarbon (THC) emissions. Since the firstintroduction of the concept by Sorenson and Mik-kelsen (19… 相似文献
14.
建立和分析了U型真空管集热器的热效率的表达式,并在FLUENT中建立动态仿真模型,利用模型分析了U型管的入口流速和结构尺寸、太阳辐照度对真空管内温度场的影响.结果表明:减小入口流速和U型管内径、增加太阳辐射量和U型管的长度都可以使真空管的出口平均温度增高.该分析结果可对U型玻璃真空管的优化设计、参数匹配等方面提供理论支撑. 相似文献
15.
油菜素内酯提高小麦萌发期间抗盐性机理初探 总被引：8，自引：0，他引：8
通过实验确定0.1mg/L BR为盐胁迫下提高小麦抗盐性的最适浸种浓度；在不同浓度NaCl处理下，0.1mg/L BR浸种的小麦胚芽鞘长度、地上部分高度、根长、根数、地上部分干重、根干重均明显高于同等浓度NaCl处理的清水浸种的小麦；地上部分膜透性也明显降低。 相似文献
16.
针对高功率激光焊接过程中的气体保护问题,设计了三管组合保护气嘴结构。对保护气嘴的倾角以及三管气嘴的间距进行精确设计,三管组合保护气嘴通过三向活动导向臂与焊接头固定,并且可以很方便的调节气管方向及与焊缝的位置。通过和单管及双管保护气管的焊接效果相比较,三管组合保护气嘴结构可以得到光亮、平整的焊缝效果。 相似文献
17.
Guang-ming Chen Li-xia Liang Li-ming Tang Xiao-xiao Xu Zhi-jiang Zhu Qi Chen 《浙江大学学报(A卷英文版)》2009,10(11):1678-1682
An adjustable ejector expansion device for a CO2 heat pump water heater （HPWP） is proposed to improve the system performance. It has been designed to investigate experimentally the effects of the motive nozzle throat area of the ejector, entrained flow pressure, back pressure and primary flow pressure on the entrainment ratio. Experiments based on different motive nozzle throat areas were conducted and the results of the prototype ejector using CO2 as working fluid are presented. The results show that an adjustable ejector can achieve high performance and work well in a wide range of working conditions. 相似文献
18.
等离子割炬工作原理复杂,喷嘴在冷却水温度场和流场耦合作用下工作,实物实验难度较大,文章采用CFD软件针对两种割炬喷嘴进行数值模拟,分析在不同冷却水流速度下的温度云图和温度曲线图,确定喷嘴结构,给出建议冷却水流速度。 相似文献
19.
This paper establishes a 3D numerical model for 15# hydropower house of the Three Gorges Project (TGP) and performs a nonlinear static and dynamic damage analysis. In this numerical model, a coupling model of finite and infinite elements for simulating infinite foundation of hydropower station is adopted. A plastic-damage model based on continuum damage mechanics, which includes the softening and damage behavior under tension is considered for the concrete material. The dynamic equilibrium equations of motion are solved by using the HilberHughes-Taylor (HHT) time integration method. Firstly, the static damage response analysis of the hydropower station is conducted due to high tensile stress resulting from large water head and diameter of an inlet pipe. Then, on the basis of static simulation, the dynamic damage analysis of hydropower house subjected to earthquake motion is simulated. Numerical results show that under large water head and diameter of an inlet pipe of the project, the damages are mainly located near the top of the spiral case from the inlet section to the 0° section; under combined loadings of static loads and earthquake, the damages of the concrete surrounding the spiral case increase insignificantly; however, some damages occur on the side walls of the main powerhouse. 相似文献
20.
本溪钢铁公司炼钢厂在“连铸＋热轧”工艺生产低碳钢时,对在其钢板上表面中心和边部出现长度与宽度不等的其延伸方向与轧制方向相同的线状缺陷问题进行了研究。通过对保护渣、浸入式水口深度、水口氩气量、冶炼炉次和水口偏流等影响因素的分析与改进,将该类线状缺陷的出现几率由0．169％下降到0．051％。 相似文献