Numerical simulation of cavitation characteristics of Venturi injector
CHENG Qian, HUANG Xiuqiao, LI Hao, HAN Qibiao
Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences/Key Laboratory of Water-saving Agriculture of Henan Province, Xinxiang, Henan 453002, China
Abstract：The cavitation characteristics of one post-optimized Venturi injector were investigated by numerical simulation, in order to explore declination in the injection performance caused by cavitation and to reveal the mechanism of energy loss in the flow field of Venturi injector. Results show that when the pressure difference across the Venturi increases, the suction pressure decreases continuously and the suction flow rate rises. Once the suction pressure decreases to the minimum, the suction pressure will keep constant, so does the suction flow rate. Then if the pressure difference is increased further, cavitation will occur in the junction between the throat and the diffuser firstly, and then and expand downstream gradually along the diffuser wall. By contrasting the total hydraulic heads at various cross-sections along the Venturi injector axis at different pressure conditions, the energy loss at the throat increases with increasing pressure difference, but it is about half the total energy. Once the cavitation occurs, the energy loss at the throat will keep constant, while the energy loss across the diffuser will be enlarged. This is because cavitation development can deteriorate the flow condition in the diffuser and produce large-scale vortices around the cavities, which consume even more energy. The increased energy consumption results in a sudden and rapid decrease in the injection efficiency.
[1]韩启彪, 黄兴法, 刘洪禄,等. 6种文丘里施肥器吸肥性能比较分析[J]. 农业机械学报, 2013,44(4):113-117,136. HAN Qibiao,HUANG Xingfa,LIU Honglu,et al. Comparative analysis on fertilization performance of six Venturi injectors[J]. Transactions of the CSAM, 2013,44(4):113-117,136.(in Chinese)[2]封俊, 沈雪民, 刘春和,等. 文丘里滴灌施肥器水力性能的研究[J]. 节水灌溉, 1992(1):41-43. FENG Jun, SHEN Xuemin, LIU Chunhe, et al. Research on the hydraulic performance of Venturi injector in drip irrigation[J]. Water saving irrigation, 1992(1):41-43.(in Chinese)[3]金永奎, 夏春华, 方部玲. 文丘里施肥器系列的研制[J]. 中国农村水利水电, 2006(5):14-16,20. JIN Yongkui, XIA Chunhua, FANG Buling. Research and development of Venturi fertilizer applicator series[J]. China rural water and hydropower, 2006(5):14-17,20.(in Chinese)[4]LIMA NETO I E, De MELO PORTO R. Performance of low-cost ejectors[J]. Journal of irrigation & drainage engineering, 2004,130(2):122-128.[5]王淼, 黄兴法, 李光永. 文丘里施肥器性能数值模拟研究[J]. 农业工程学报, 2006, 22(7):27-31. WANG Miao, HUANG Xingfa, LI Guangyong. Numerical simulation of characteristics of Venturi injector[J]. Transactions of the CSAE, 2006,22(7):27-31.(in Chinese)[6]孙艳琦, 牛文全. 文丘里管结构参数对其水力性能的影响[J]. 西北农林科技大学学报(自然科学版), 2010,38(2):211-218. SUN Yanqi, NIU Wenquan. Effects of Venturi structural parameters on the hydraulic performance[J]. Journal of Northwest A&F University(nat sci ed), 2010,38(2):211-218.(in Chinese)[7]严海军, 陈燕, 初晓一,等. 文丘里施肥器结构参数优化对吸肥性能的影响[J]. 排灌机械工程学报, 2013, 31(2):162-166,179. YAN Haijun, CHEN Yan, CHU Xiaoyi, et al. Influence of optimization of structural parameters on injection performance of Venture injector[J]. Journal of drainage and irrigation machinery engineering, 2013,31(2):162-166,179.(in Chinese)[8]范兴科, 孔令阳. 文丘里施肥器能量转化关系[J]. 排灌机械工程学报, 2013,31(6):528-533. FAN Xingke, KONG Lingyang. Relationship of energy conversion for Venturi injector[J]. Journal of drainage and irrigation machinery engineering, 2013,31(6):528-533.(in Chinese)[9]XU Yuncheng, CHEN Yan, HE Jianqiang, et al. Detection of cavitation in a Venturi injector with a combined method of strain gauges and numerical simulation[J]. Journal of fluids engineering, 2014,136(8):081302.[10]XU Yuncheng, CHEN Yan, WANG Zijun, et al. Investigation of the cavitation fluctuation characteristics in a Venturi injector[J]. Fluid dynamics research, 2015,47(2):25506.[11]FENG Weimin, CHENG Qian, GUO Zhiwei, et al. Simulation of cavitation performance of an axial flow pump with inlet guide vanes[J]. Advances in mechanical engineering, 2016,8(6):1-8.[12]曹国凭, 张耀宗, 陈举烽. 气、液两相流在水平管道中水头损失的实验研究[J]. 河北理工学院学报, 2006,28(3):118-120,125. CAO Guoping, ZHANG Yaozong, CHEN Jufeng. The Experimental research on head loss of two phase gas-liquid flow in the level line[J]. Journal of Hebei Institute of Technology, 2006,28(3):118-120,125.(in Chinese)
