5种泵停留时间分布实验研究

Residence time distribution of five pumps

采用脉冲示踪法对轴流泵、单级离心泵、多级离心泵、液压隔膜泵、三柱塞计量泵的停留时间分布(RTD)进行了实验研究。实验结果表明:轴流泵RTD呈单峰分布,无死区,返混程度与等径空管接近;离心泵RTD呈单峰分布,有死区,多级离心泵返混程度大于单级,单级大于等径空管;隔膜泵RTD呈单峰分布,三柱塞泵呈三峰分布,二者都有死区存在;各类泵RTD特征均由其机械结构和运转方式决定;各类泵的返混均受流量影响,其返混程度随流量的减小而增大,叶片式泵较容积式泵更明显;各类泵的平均停留时间均与流量成反比,并与空时吻合较好;各类泵中,轴流泵返混最小,其他4种泵均存在一定死区,流型介于平推流和全混流之间。

The residence time distribution（ RTD） of five pumps,axial flow pump（ AFP）,single-stage centrifugal pump（ SSCP）,multiple-stage centrifugal pump（ MSCP）,diaphragm pump（ DP） and three-plunger pump（ TPP）was investigated based on pulse tracer method. According to the experimental results,the RTD curve of AFP shows unimodal distribution without dead zone. The back-mixing of AFP is close to the blank pipe with equal diameter and volume. The RTD of centrifugal pump acts as unimodal distribution with dead zone. The back-mixing of MSCP is greater than SSCP,and SSCP is greater than the blank pipe. The RTD curve of DP is single-peak but TPP is trimodal,dead zone is found in both of them. The RTD is determined by its mechanical structure and operating mode. The back-mixing of five pumps is all affected by the flow rate,which increases with the flow rate declining.The back-mixing of vane pumps is affected more obviously than volumetric pumps by the flow rate. The mean residence time of five pumps is all in inverse proportion to the flow rate,and all in good agreement with the space time. The back-mixing of AFP is the lowest in five pumps. The flow patterns of other four pumps are all between plug flow and complete mixing flow,and the dead zone exists in them.