Measurement Characteristics Of Cone Flowmeter Based On Bioic NN-Smooth Surface

In the field of industry,agriculture and daily life,differential pressure flowmeter has been widely used and plays a very important role in the field of flow measurement.As a kind of side wall contraction throttling device,the cone flowmeter has the characteristics of high precision,anti-fouling,stable performance and short requirements for the front and rear straight pipe sections compared with the central contraction throttling devices such as standard orifice plates and Venturi tubes.It has certain advantages in sewage measurement,wet gas measurement in oil and gas fields,wet steam measurement in power plants,and multiphase flow measurement.At the same time,its emergence has also made a qualitative leap in the improvement of differential pressure flowmeters.However,although the pressure loss of the cone flowmeter is lower than that of the standard orifice flowmeter,it is higher than that of the Venturi flowmeter.In order to achieve the research goal of high precision and low pressure loss measurement of the cone throttling device,based on the principle of bionics,this paper designs different kinds of new cone throttling devices with bionic non-smooth surface structure.Through the combination of experiment and numerical simulation,the measurement characteristics of two kinds of cone throttling devices with smooth and non-smooth structural surfaces are explored,and the drag reduction mechanism of cone bionic non-smooth surface is revealed.The main results and understandings are as follows:(1)The design method of bionic non-smooth surface structure of cone throttling element is proposed,and the optimal non-smooth bionic structure parameters are determined.Firstly,the cone and test section of the cone throttling device were designed.Secondly,based on the bionics theory,the surface structure of the animal was abstracted and standardized,and the structural parameters of the bionic non-smooth surface were determined in combination with the actual situation.The basic physical model of the non-smooth structure and the three-dimensional model of the cone throttling device were established to provide model support for the experiment.According to the design principle of the bionic non-smooth surface structure of the cone,the discharge coefficient and the pressure loss coefficient are used as the test indexes.Four factors(non-smooth shape,diameter/width,depth/height,spacing of non-smooth structure)and three levels of orthogonal test are selected as the experimental methods to analyze the drag reduction characteristics of bionic non-smooth surface structure.The results show that through range and variance analysis,the primary and secondary order of the optimization effects of the four factors of bionic non-smooth surface structure is:non-smooth structure shape>spacing>diameter/width>height/depth,and the optimal combination is riblet-3 structure,that is,riblet non-smooth shape.When the diameter/width of the non-smooth structure is 0.6mm,the depth/height is 0.6mm,and the spacing is 0.8mm,the drag reduction effect is the best.(2)The influence of bionic non-smooth surface structure on the measurement characteristics of the cone throttling device was obtained.The effects of different non-smooth surface structures on the pressure loss,pressure loss coefficient and discharge coefficient of the cone were compared.In the experiment,nine different bionic non-smooth surface cones and smooth surface cone models were selected for research.Because non-smooth morphology is the dominant factor,it has the most significant influence on the measurement characteristics of the cone throttling device.Therefore,the optimization effect is mainly analyzed by comparing different structural forms.The results show that within the scope of this study(speed v=0.4～5.2m/s),the convex structure has a certain effect on the cone optimization,the optimization effect of the dimple structure is not ideal,and the optimization effect of the riblet structure is the most significant.Compared with the cone throttling device with smooth surface,the pressure loss of the riblet-3 surface structure is reduced by 27.0%,the discharge coefficient is increased by 16.1%,and the pressure loss coefficient is reduced by 26.7%.The accuracy and stability of the cone throttling device are improved while reducing the pressure loss.(3)The vortex structure characteristics and variation law of the cone are clarified,and the drag reduction mechanism of the non-smooth structure of the riblets on the cone throttling device is revealed.The numerical simulation schemes of smooth cone flowmeter and bionic flowmeter are determined.The turbulence model adopts SST k-ω model,and the boundary conditions of numerical simulation are determined by experiments.Through the analysis of the velocity,vorticity and resistance of the bionic non-smooth cone surface,the influence of the riblet surface structure on the flow near the wall of the cone is elaborated in detail.Due to the influence of the ’bearing’ effect formed by the rotating fluid inside the riblet,the friction form between the fluid and the wall surface is changed,and the riblet structure reduces the total resistance by greatly reducing the pressure difference resistance of the cone,so that the riblet surface structure has good drag reduction characteristics.The research results can provide theoretical guidance for the further optimization of the bionic surface.