Study On Generating Method Of Uniform Airflow Field Based On Reverse Wind Tunnel Principle And Rotation

Airflow field test technology is an important means of aerodynamic research,and it is an indispensable part in the field of aerospace,energy utilization,transportation,environmental protection,and architecture.At present,wind tunnel is the main means of airflow field test.But the research scope of conventional wind tunnel is limited.On the one hand,the construction and operation of wind tunnel require a lot of manpower and financial resources.On another hand,it cannot simulate a variety of extreme conditions and complex environment,which will restrict the development of related industries.Therefore,the research of new airflow test method to achieve the detection for achieveing device operation performance in high-speed airflow and complex environment has important engineering significance and academic value.This thesis is derived from the "Double First-class" discipline platform construction project of Chongqing University “Energy Equipment and Device Safety test platform in Multi-extreme Conditions".Based on reverse wind tunnel principle and rotation,a generating method of uniform airflow field is proposed in this thesis.Different to wind tunnel,high-speed airflow is generated in the shrinkage duct by circumferential driving.At the same time,the asymmetric uniform-flow accelerating shrinkage duct and non-uniform honeycomb are used to overcome the flow field deviation caused by rotating motion and then ensure the quality of the airflow field.Furthermore,by the generation of complex environment in the test space and the introduction of test high voltage,the comprehensive airflow field test conditions,which combines the high-speed airflow,complex environment and even high-voltage,is created.By exploring the basic physical process,the generating method of uniform airflow field based on rotation is studied by means of theoretical analysis,numerical calculation and experimental verification from the perspective of airflow field distribution.The main research work and achievements are listed as follows:(1)The principle innovation of generating method of uniform airflow field based on rotation is analyzed,and the schematic design is completed.Based on the principle of relative motion,the generation mode of relative velocity and the offset characteristics of airflow field in this method are studied.(2)The physical and mathematical models of the generating method of uniform airflow field based on rotation are summarized and established.By using the numerical computation method which combines the reference frame with dynamic and static multi-area patched grid model,the distribution characteristics of three-dimensional rotating flow field in test space is studied.Furthermore,the generation and recovery of rotating wake in the test space is analyzed from axial and radial dimensions,and the influence of rotating wake on the test flow field is evaluated.(3)Based on the asymmetric uniform-flow accelerating shrinkage duct and non-uniform honeycomb,the airflow field uniformity optimization method is proposed for rotating airflow field.As first,the acceleration and uniform effects of the asymmetric uniform-flow accelerating shrinkage duct and influencing factors are studied.Secondly,guided by the flow field uniformity indexes including dynamic pressure coefficient,flow deviation angle and axial static pressure gradient,the flow field uniformity is optimized by using orthogonal experimental design and virtual objective optimization method.Then,according to the analysis of the resistance characteristics of the non-uniform honeycomb,the flow field uniformity design method based non-uniform honeycomb damper compensation is studied.Finally,the uniformity optimization method for rotating airflow field is summarized into four steps: design of scaling model,structure design of shrinkage duct,rotating wake evaluation,and airflow field uniformity optimization.(4)Taking the high-speed train roof insulator as example,the equivalence of uniform airflow field based on rotation and linear airflow field is studied both in single-phase flow condition and two-phase flow condition.By the study of Reynolds number distribution characteristics on insulator surface,the equivalence of uniform airflow field based on rotation under single-phase airflow is analyzed.Furthermore,according to the analysis of typical working conditions,the concept,implementation,and classification of airflow field test in complex environment are summarized.Based on the two-fluid multiphase flow model,the collision and accumulation characteristics of experimental particles in gas-liquid/gas-solid two-phase rotating flow field are comparative studied,which proves the equivalence of uniform airflow field based on rotation in two-phase flow.(5)High-speed icing tests of insulators were carried out in the Multi-functional Artificial Climate Laboratory of Chongqing University.The results show that the calculated values of ice mass and ice thickness on insulator surface in uniform airflow field based on rotation have little difference with the icing test results.The results prove the uniform airflow field based on rotation has good equivalence in accumulative airflow field experiment in complex environment such as icing,and the accuracy of the numerical results is verified.