共查询到19条相似文献,搜索用时 109 毫秒
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目的 冷喷涂过程中喷嘴内流道关键尺寸是影响粒子加速的重要因素。虽然喷嘴下游长度与扩张比是喷嘴的2个最重要参量,但目前对喷嘴优化设计的研究仍有深入空间,比如喷嘴下游形状。方法 本文利用计算流体动力学的软件ANSYS/Fluent进行数值模拟研究,在与传统锥形下游相比较后,设计了钟形下游与喇叭形下游喷嘴。同时研究了喷嘴下游形状对气流与粒子加速行为的影响。结果 对于钟形下游喷嘴,其气流速度在过喉部后迅速增加到较高数值,随后变化缓慢;对于喇叭形下游喷嘴,其气流速度在过喉部后先增加缓慢,直至截面积开始快速增加时,气流速度迅速增加;喷嘴下游形状对粒子撞击基板时的速度有一定影响,且随着喷嘴下游长度和粉末粒度的变化而改变。对于Cu粉,当为下游100 mm短喷嘴时,锥形下游喷嘴对10~20 μm的粒子加速效果最好。当粉末在20 μm以上时,喇叭形下游喷嘴的加速效果最好。对于下游220 mm长喷嘴,钟形下游喷嘴对10~30 μm的粒子加速效果最好。当粉末在30 μm以上时,锥形下游喷嘴的加速效果最好。对于Al粉,当为下游220 mm长喷嘴时,钟形下游喷嘴对10~50 μm的粒子加速效果最好,喇叭形下游喷嘴加速效果最差。结论 冷喷涂喷嘴下游形状对气体与粒子加速有显著的影响。 相似文献
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对于非垂直入射的颗粒在冷喷涂沉积过程中产生的残余应力进行研究,旨在分析该状况下残余应力的变化趋势及其对沉积特性的影响.采用ABAQUS/Explicit有限元分析软件,以Al/A1作为粒子和基体的材料进行模拟,研究了粒子倾斜冲击对残余应力的影响,并添加无限元素层以增强数值稳定性.结果表明:颗粒以不同角度沉积基体的过程分... 相似文献
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基于Euler法的冷喷涂粒子与基体高速冲击过程数值分析 总被引:2,自引:0,他引:2
利用非线性动力分析软件LS-DYNA,对冷喷涂中铜粒子与铜基体的碰撞过程进行了数值分析.研究冷喷涂过程中沉积粒子与被喷涂基体的变形行为.结果表明:使用Lagrange法,当粒子撞击速度过大时,网格的过度畸变会导致计算的终止,其计算结果与实验结果相比有一定差距.而采用Euler法计算得到的铜粒子与铜基体在碰撞结束后的沉积形貌与实验观察吻合很好,表明模拟结果相对于Lagrange法的计算结果更为精确.此外,Euler法能准确的模拟多粒子共同撞击基体的过程,数值计算得到的多粒子涂层内部结构与实验结果也能很好的吻合. 相似文献
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在喷管出口和基板之间外加电场来加速带电颗粒,并对带电纳米铜颗粒进行电场辅助冷喷涂气固两相流数值研究,分析在气流和电场力的综合作用下颗粒粒径、电荷量、基板电压等参数对颗粒速度的影响。结果表明,电场辅助冷喷涂不适合微米级颗粒,但非常适合纳米颗粒喷涂,且粒径越小,颗粒撞击速度越大,电场力加速效果越显著;颗粒电荷量、基板电压越大,颗粒撞击速度越高。 相似文献
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为研究多喷嘴射流泵性能和内部流场特征,设计了不同结构的多喷嘴射流泵试验模型.采用k-ε湍流模型和壁面函数法对不同参数下的多喷嘴射流泵进行了数值模拟,模拟结果表明,喷嘴数和喷嘴角度及喉嘴距对射流泵工作性能影响较大;在吸入室及喉管入口处湍动能较大.利用PIV系统对不同结构射流泵内部流场进行了三维测量,获得了射流泵对称面流场的速度矢量和湍动能等值线图.试验结果表明,其速度梯度衰减得愈快,工作流体和被吸流体混合距离越短.验证了多喷嘴射流泵可缩短喉管长度.测量结果证明数值模拟的正确性,为多喷嘴射流泵理论研究和合理设计提供了理论依据. 相似文献
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This study investigates the effect of substrate size on the supersonic jet flow regime, particle acceleration and temperature distribution within the substrate in cold spraying. A computational fluid dynamics approach is employed in the present work to achieve this objective. The simulated results show that substrate diameter has some effect on the gas flow regime and the consequent particle motion. When the substrate diameter is smaller than the nozzle exit diameter, the thickness of the bow shock formed in front of the substrate is rather small, which contributes to increase the particle impact velocity. With increasing the substrate diameter, the bow shock thickness increases gradually up to the point at which the substrate diameter is beyond the nozzle exit diameter. A further increase beyond this has almost no effect on the flow regime and the bow shock thickness. Besides, the current numerical work also reveals that the temperature distribution within the substrate can be significantly influenced by substrate thickness. With an increase in substrate thickness, the substrate temperature presents a downward trend, which means that higher inlet temperature may be required for thick substrate to achieve the same preheating effect. 相似文献
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S. V. Klinkov V. F. Kosarev V. N. Zaikovskii 《Journal of Thermal Spray Technology》2011,20(4):837-844
Traditionally, in cold spray two-phase supersonic jet formed with the help of converging-diverging nozzle are used. In this
study an alternative design of cold spray nozzle is proposed in which a high velocity two-phase flow is created using an intense
flow swirling in a constant section barrel (cylinder) with double-edged bevel exit. As a result, a high velocity gas-powder
mixture jet is produced presenting a fan-shaped jet spreading at a large angle in one plane and approximately of equal size
along the normal to this plane. This results in greater angles of particle deposition and, hence, in larger deposition widths,
with the maximum width of deposition spot reaching 25 barrel diameters. The performed experimental study proves the new nozzle
design to be appropriate for deposition of cold-sprayed coatings. 相似文献
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为提高磨料射流抛光加工过程中的可靠性和效率,对在磨料射流加工中起到重要作用的喷嘴进行研究具有重要的意义。该文在分析喷嘴射流机理的基础上,针对典型的喷嘴进行仿真研究,得到了喷嘴内部压力场和速度场的分布情况,同时采用有限元对喷嘴结构参数进行数值模拟分析与比较,得出不同结构参数对于流体性能的影响。最后对该仿真方法的可靠性进行了实验验证,并给出了误差率,证明了在该文中所使用的仿真方法具有可靠性,为进一步研究磨料射流喷嘴提供了实用的价值和有效的方法。 相似文献
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以结晶器表面的钢液流速和结晶器内的射流冲击深度作为参考指标,基于FLUENT对邯钢宽厚板坯连铸结晶器内流场进行数值模拟,研究该连铸机所用的A水口的性能及在该水口作用下的拉速、水口浸入深度对结晶器内流场的影响。结果表明:在A水口的作用下结晶器的表面流速大,射流冲击深度则较小,有较大的卷渣可能性;最大结晶器表面流速随着拉速的增大而逐渐增大,射流冲击深度则逐渐减小;结晶器表面流速随着水口浸入深度的增加而减小,射流冲击深度则增大;根据邯钢宽厚板坯连铸机的实际生产条件,在拉速较大时,应将A水口替换为平行水口;在使用A水口时,在适当降低拉速的同时,水口浸入深度也应适当增大。 相似文献
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Wen-Ya Li Shuo Yin Xueping Guo Hanlin Liao Xiao-Fang Wang Christian Coddet 《Journal of Thermal Spray Technology》2012,21(1):41-48
During cold spraying (CS), heat exchange between the hot driving gas and the solid bodies, e.g., spray nozzle and substrate,
results in the temperature redistribution within the solid bodies. In this study, numerical and experimental investigations
on the heating behavior of the substrate and nozzle wall were conducted to clarify the temperature distribution within the
solid bodies in CS. The results show that after heating by the hot gas, the highest temperature presents at the center point
of the substrate and decreases toward the substrate back surface and edge. With increasing standoff distance or decreasing
inlet temperature, the substrate temperature decreases gradually, but the temperature gradient within the substrate changes
little. The numerical results are consistent with the experimental measurements. Besides, it is also found that increasing
the substrate size (diameter) can lead to the gradual increment in the substrate temperature. Moreover, the numerical study
on the temperature distribution within the nozzle wall reveals that the highest temperature presents at the throat section
of the nozzle and that the nozzle material significantly affects the temperature distribution within the nozzle wall. 相似文献