Effects of nozzle inner surface roughness on the cavitation erosion characteristics of high speed submerged jets
Effects of nozzle inner surface roughness on the cavitation erosion characteristics of high speed submerged jets
复制标题
喷嘴内表面粗糙度对高速浸没射流空蚀特性的影响
DOI：
10.1016/j.expthermflusci.2016.01.009
复制
发表时间：
2016-06-01
影响因子：
3.2
通讯作者：
Fang, Zhenlong
中科院分区：
文献类型：
--
作者：
Li, Deng;Kang, Yong;Fang, Zhenlong
空泡射流由于其强大的冲蚀能力而被广泛应用于各种场合。为了最大限度地发挥空化射流的冲蚀能力，首次从冲蚀强度和冲蚀效率两个方面对喷嘴内表面粗糙度对淹没空化射流冲蚀特性的影响进行了实验研究。通过使用六个不同表面粗糙度值（0.8 μ m、1.6 μ m、3.2 μ m、6.3 μ m、12.5 μ m和25 μ m）的风琴管空化喷嘴将浸没射流冲击到纯铝（1070 A）试样上，测量和分析了在不同入口压力和喷射距离下的质量损失和比能耗。并对各进气压力下最佳射距下的冲蚀试样宏观形貌进行了显示和分析。结果表明，表面粗糙度可以有很大的影响，空蚀强度在最佳间距附近的空蚀和空蚀效率的间距超过最佳。表面粗糙度对空蚀的影响是有利还是不利，主要取决于决定粘性底层厚度的入口压力。更具体地，在10 MPa和15 MPa的入口压力下，12.5 μ m的表面粗糙度值对于在约50 mm的喷距处获得最强的冲蚀强度和最大效率是最好的;而在入口压力为20 MPa和25 MPa时，粗糙度值6.3 μ m代替12.5 μ m成为最佳粗糙度值，最佳间距增加到60 mm。间距超过最佳值后，特别是在相对较低的入口压力下，比能耗大大增加，表明冲蚀效率显著降低。结果表明：表面过于光滑不利于空泡的形成，导致空蚀强度减弱;表面过于粗糙，导致能量耗散大，射流发散，导致空蚀强度显著降低。根据实验结果，存在一个最佳的内表面粗糙度值，以获得最强的侵蚀空蚀能力的淹没空化射流。(C)2016 Elsevier Inc. All rights reserved.
Cavitating jet is now being widely used in a variety of situations due to its strong aggressive erosion ability. In order to push the erosion capability to a maximum, the effects of nozzle inner surface roughness on the cavitation erosion characteristics of submerged cavitating jets were experimentally investigated for the first time with respect to aggressive erosion intensity and efficiency. By impinging the submerged jets on specimens of pure aluminum (1070A) using six organ-pipe cavitating nozzles of different surface roughness values (0.8 mu m , 1.6 mu m, 3.2 mu m, 6.3 mu m, 12.5 mu m, and 25 mu m), the mass loss and specific energy consumption at various inlet pressures and standoff distances were measured and analyzed. And the macroscopic appearances of eroded specimens at optimum standoff distances corresponding to each inlet pressure were displayed and analyzed. Results show that surface roughness can have great effects on cavitation erosion intensity at standoff distances around the optimum and on erosion efficiency at standoff distances exceeding the optimum. The influence of surface roughness on cavitation erosion, adverse or advantageous, depends largely on the inlet pressure which determines the viscous sublayer thickness. More specifically, at inlet pressure of 10 MPa and 15 MPa, surface roughness value of 12.5 mu m is the best for achieving the strongest erosion intensity and maximum efficiency at standoff distance around 50 mm; while at inlet pressure of 20 MPa and 25 MPa, roughness value of 6.3 mu m replaces 12.5 mu m to be the best one with the optimum standoff distance increased to 60 mm. After standoff distance exceeds the optimum value, the specific energy consumption greatly increases, especially at relative lower inlet pressures, indicating a dramatic decrease of erosion efficiency. It can be concluded that excessive smooth surface is not conducive to the formation of cavitation bubbles, leading to an attenuated intensity of cavitation erosion; while excessive rough surface causes much energy dissipation and leads to divergent jets, resulting in a significant reduction of erosion intensity. According to the experimental results, there exists an optimum inner surface roughness value to achieve the strongest aggressive cavitation erosion capability for submerged cavitating jets. (C) 2016 Elsevier Inc. All rights reserved.