Ultrasonic Flowmeter Path Design And Optimization Of Flow Field Downstream Flow Conditioner

The flow rate is one of the three major measurement parameters in the field of industrial automation,and the accuracy and stability of the measurement results are critical.Ultrasonic flowmeters are commonly used as flow measurement devices,and their performance is directly affected by the path structure and flow field development.Thus,this dissertation focuses on the study of"ultrasonic flowmeter path design and optimization of flow field downstream flow conditioner"to study the theory of 3D single-path and multi-path design of ultrasonic flowmeters,performance evaluation and flow field optimization methods for typical flow conditioners.The research work has important academic value and practical significance for improving the accuracy of fluid measurement and accelerating the development of intelligent manufacturing and equipment technology.The research is funded by the Guangdong Provincial Science and Technology Plan Project(2016A040403044)and the Guangzhou Science and Technology Plan Project(2013J4400064).The dissertation discusses the domestic and foreign research progress from the aspects of the influence of transit-time ultrasonic flowmeter accuracy factors,the structure of ultrasonic flowmeter path,and the influence of flow conditioner on the flow field,and determines the research contents.The primary work includes:?Make an exploration of 3D single-path design method of the transit-time ultrasonic flowmeter to improve the adaptability of single-path to irregular flow fields.The average relative error and standard error of flow measurement are proposed as the evaluation indexes of single-path performance,which comprehensively reflects the adaptability of the path to irregular flow fields.The formulas for the calculation of the minimum number of path-segments,the distance between each path-segment and the center of the pipe,and the angles between the same or opposite side of the adjacent path-segment of 2D model are derived to design the single-path 2D model.The calculation examples show that the path designed with the priority of the path coverage rate can effectively increase the path length,and the path coverage rate can be2.7 times of commonly used representative paths,which helps to improve the adaptation of the path to flow field changes.Besides,the path designed with the priority of structure technology,while increasing the path length,covers 2.6 times of the maximum coverage rate of commonly used representative paths.?Make an exploratory study of 3D multi-path design method of the transit-time ultrasonic flowmeter to improve the adaptability of multi-path to irregular flow fields.The number of paths,the average number of path reflections,the path coverage rate,the average relative error of flow measurement,and the standard error of flow measurement are proposed as multi-path performance evaluation indicators to measure multi-path adaptation to irregular flow fields.The formulas such as the number of paths,the number of path-segments in each path,the number of multi-path 2D model combinations,etc.are deduced to realize multi-path2D model modeling and solution.The universal coordinate calculation formula to calculate the coordinates of each channel node are derived,and the nodal coordinate adjustment method are studied to avoid transducer position conflict.Besides,each single path's velocity weighting coefficient is calculated to realize the 3D multi-path.The deduction of the example shows that the design path only needs 1/3 of the number of transducers when it is consistent with parallel path coverage.In addition,the design path uses only 0.67 of the number of cross-multichannel transducers,achieving more than 5.46 times its coverage.?In-depth study of CFD-based flow regulator evaluation method and flow field optimization strategy.By constructing a universal flow conditioner research model and using CFD technology to easily obtain the flow velocity information downstream the conditioner,the performance of the flow conditioner can be quickly evaluated.The simulation analysis and optimization of the performance of a typical flow conditioner are studied.A hollow window conditioner is proposed.The blades at the internal intersection of the Etoile conditioner are deleted and the blades near the wall are added.The flow field downstream the conditioner is effectively improved when the Reynolds number is 5.84×10~4 and 5.84×10~5.An equal-diameter porous conditioner is proposed to reduce the number of apertures and pitch diameters from 10to 7 to improve the manufacturability of the condtitioner,and to improve the flow field in the large Reynolds number and near-conditioner region by changing the center four holes size.The design of the combined conditioner based on orthogonal design is studied.The orthogonal design method is used to design the frontal member length,front and rear end spacing,and blade hollow diameter of the combined conditioner to rapidly distinguish the primary and secondary factors that affect the performance of the conditioner,reducing the number of tests,and quickly finding out the optimal combination conditioner.The optimization of the flow conditioner manufacturability is explored.The formula for calculating the total number of connections for multiple connection points under the intuitive connection method(two or two blades are connected once)is derived,and two optimization methods to effectively reduce the number of connections between the blades by flexing the blade slotting position are proposed,reducing the number of connections from 112 times to 64 times,10 times.?The dissertation also carries out research on channel design method and flow field optimization strategy of transit-time ultrasonic flowmeter.The process priority 3D single-path ultrasonic flowmeter designed under the guidance of 3D single-path design theory is verified by the Guangzhou Energy Inspection and Research Institute.3D single-path flow meter design theory meets manufacturability with an error of less than±0.81%in 0.2~10.0m~3/h.Based on the 3D multi-path design theory,the process priority 3D multi-path ultrasonic flow meter prototype design results show that the design theory of the multi-path flow meter meets the manufacturability,and the indication error is less than±0.97%in 12 to 1200 m~3/h.The M-type flow conditioner is made using the hollow window conditioner as a reference,and the NEL conditioner is selected with the guide for the equal diameter porous conditioner to improve the performance of the flow meter in the DN20 water flow standard device test system.Both achieved very good rectification effects.The ultrasonic path design theory and the flow field optimization strategy all achieve the expected results in practical applications,which proves the validity and applicability of the methods studied in this dissertation.