Preliminary Study On The Dropsizing Of Kerosene Atomization In Supersonic Airstream By Double-spectral Imaging

In this thesis, a fine-online measurement of droplet size two-dimensional distribution in supersonic atomization field was studied to provide basic reference data for the design and evaluation of kerosene scramjet combustion chamber. Scramjet is the primary key technology of hypersonic vehicle. It’s one of the lead edge of the world. It’s challenging for the study of kerosene’s supersonic atomization, combustion phenomenon and droplet size measurement which involve large span and multiple discipline. It is the key issues for the development of kerosene scramjet, but the jet breakup and atomization is one of the most difficult and unresolved fundamental problems of hydrodynamics. On the basis of the existing spray field of laser measurement technology, such as phase Doppler technique (PDA), light scattering, interferometry, diffraction and holography etc, a new measurement of laser dropsizing of kerosene injected into a supersonic airstram by dual-spectral imaging method which is a combination of planar laser-induced fluorescence (PLIF) and Mie light scattering with high spatial and temporal resolution is studied. The method utilizes the relationship between PLIF intensity and the droplet diameter and the relationship between Mie scattering light intensity and droplet diameter, to measure Sauter mean diameter (SMD) two-dimensional distribution of the spray field. Firstly, the basic principles of PLIF/Mie double spectral imaging measurements was introduced and the measurement system of particle size distribution for kerosene’s supersonic atomization was designed, including the supersonic wind tunnel, the experimental platform for low spray field, conversion system for laser sheet, the imaging system and timing control etc. A test was performed on the experiment platform of low and the result proved that the measurement of dual-spectral imaging is feasible. Compared with other measurement methods, dual-spectral imaging measurement method has great advantages. It can obtain the transient information of droplet size two-dimensional distribution. Secondly, the particle size inversion and error analysis of the double spectral imaging technique have discussed detailedly. when the inversion of particle size, the type and parameters of droplets for test between one of droplets for calibration should be close or should not deviate too much. Finally, a numerical simulation and optimization of kerosene atomization in supersonic airstream based on the grey system theory was performed before the experimental measurements for experimental convenience and providing information and basis for measurement calibration and error estimation. The liquid kerosene atomization was numerical simulated by FLUENT software while the angle of jet-flow, the diameter of nozzle, the velocity of jet-flow were considered as independent parameters. The penetration depth of the spray, it’s range of diffusion and it’s sauter mean diameter were acquired by a group of orthogonal experiments. The optimum atomization parameters were obtained.In this dissertation, the main innovations are as follows. First and foremost,the PLIF/Mie double-spectral imaging technique was used to measure the droplet size of kerosene injected into a supersonic airstream. Secondly, A particle size inversion model for PLIF/Mie double-spectral imaging technique was used, and inversion error was quantitatively analyzed, which can provide a basis for the arrangement of particle size measurement system, what’s more, a numerical simulation and optimization method of kerosene atomization in supersonic airstream based on a combination of the gray system theory and orthogonal design was used, which can provide a basis for the design of the supersonic wind tunnel and verify the accuracy of the measurement results.