| Hypersonic vehicle has increasingly become a research hotspot in aerospace industry.The development of hypersonic vehicle technology is inseparable from digital design method,which relies on accurate numerical simulation model,and the establishment and verification of the model are inseparable from a large number of experimental data.Hypersonic flow field is highly inhomogeneous and unsteady complex flow.The flow parameters vary greatly,which requires high measurement technology.Because the wind tunnel equipment in our country are generally equipped with traditional contact equipment such as force balance,thermocouple and pressure sensor,these measuring methods can only measure the temperature and pressure on the surface of aircraft model,and cannot give the fine structure in the boundary layer of hypersonic flow field,which makes it more difficult to obtain reliable calculation and experimental verification results.Planner Laser Induced Fluorescence(PLIF)technology is one of the most widely used and promising visualization measurement methods for flow field.It has the advantages of non-contact(non-interference flow field),high spatial-temporal resolution(ns-level time resolution,micron-level spatial resolution)and good tracer follow-up.In order to meet the needs of hypersonic flow field measurement,the method of toluene PLIF flow field visualization is studied in this paper.Firstly,the relationship between the intensity of laser-induced toluene fluorescence signal and laser energy,molecular density of toluene,pressure and background gas composition was studied by theoretical analysis of laser-induced fluorescence spectrum.Secondly,on the basis of theoretical research,a toluene PLIF flow field display system is designed and constructed,which mainly consists of laser and optical system,tracer generation system,signal acquisition system and timing control system.Secondly,the influence of the spectral characteristics of toluene and the parameters of laser energy,delay and the number density of toluene particles on the intensity of fluorescence signal was studied experimentally by using the flow field display system.Finally,PLIF flow visualization experiments were carried out under the conditions of normal temperature,atmospheric pressure,constant laser energy and nitrogen as background gas.The transient structure of flow field was clearly displayed and the spatial distribution of flow field density was obtained.The work of this paper lays a foundation for the research of hypersonic flow visualization technology and provides support for the development of numerical simulation model of hypersonic flow field. |
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