摘要
为了研究文丘里施肥器在压差较大的情况下产生的临界空化对微灌系统灌水器的工作压力影响,试验选取并研究了DN25型文丘里施肥器在吸肥过程中发生的空化现象,测试了7个不同进口压力水平下文丘里施肥器的吸肥流量随进出口压差变化的规律,同时采用动态应变仪测得了对应工况下施肥器喉部和扩散段外侧的应变数据,比较分析了应变数据的标准差与吸肥流量之间的关系,以及文丘里施肥器发生空化时内部流动特性变化规律.试验结果表明,当进口压力在0.20 MPa以下时,文丘里施肥器内部未发生空化;当进口压力在0.20 MPa以上时,吸肥流量增大至某稳定值时所对应的临界最大压差与进口压力呈线性关系,此时文丘里施肥器内部发生临界空化.当进口压力超过临界最大压差时,应变标准差随进出口压差变化的趋势曲线呈M型,且M型曲线的3个特征拐点对应的进出口压差均与其进口压力呈线性关系.
In Venturi injector,the critical cavitation caused by large pressure difference will result in poor fertigation uniformity.Experimental investigation was conducted to study the cavitation phenomenon of DN25 Venturi injector.For seven different inlet pressure values,the changes of suction flow rate were measured under different pressure differences between inlet and outlet.The strain values on the enternal surface of throat and diffusion portions were detected by dynamics strain indicator.Stan-dard deviations of the strain values were calculated to analyze the relationship between the suction flow rate and the internal characteristics of the cavitating flow.The results show that critical cavitation occurs in Venturi injector when inlet pressure is below 0.20 MPa.As inlet pressure exceeds 0.20 MPa,the critical maximum pressure difference has linear relationship with inlet pressure,and critical cavitation occurs in Venturi injector.When inlet pressure is larger than the critical maximum pressure diffe-rence,the variation curves of strain standard deviation versus pressure difference appear to be ＂M＂,where three inflection points of ＂M＂ are linear with inlet pressure,respectively.
出处
《排灌机械工程学报》
EI
北大核心
2013年第8期724-728,共5页
Journal of Drainage and Irrigation Machinery Engineering
基金
高等学校博士学科点专项科研基金资助课题(20120008110047)
国家863计划项目(2011AA100506)
关键词
文丘里施肥器
吸肥流量
空化
进口压力
试验
Venturi injector
suction flow rate
cavitation
inlet pressure
experiment
