Measurement And Analysis Of The Transient Emission Spectra Of Epoxypropane In The Process Of DDT

Spectral technique is an important method for transient measurement, which can obtain the characters and microinformation of the sample; It is also a powerful way to understand the microscopic mechanism and control the reaction process of the sample in the fast reaction. Anyway spectroscopy plays a vital role in the fields of shock compression and detonation.In this paper ,firstly,we have solved the key problems of the synchronization of the measuring system,the weak light detection ,the calibration of the wavelength and spectral intensity of the system and prevention of wrong trigger.Then using an advanced intensified CCD spectroscopic detector and a self-made electrical single pulse trigger ,the transient spectrum measuring technique for the research of the microscopic mechanism of the process of deflagration to detonation transition (DDT) of gaseous fuel has been established.Using this apparatus we have detected instantaneous emssion spectrum in epoxypropane deflagration detonation transition process.The exposure time of the spectra can be as short as microseconds to nanoseconds, the resolution of the spectra can reach 0.2 ran, and the wavelength range of the spectra is 200-900nm.By using this technique and with the 150g/mm grating of spectrometer,emission spectra of epoxypropane in the DDT process with exposure time of microseconds to nanoseconds have been acquired from different side windows and the end window of an explosion shock tube. Results show that at the beginning of the DDT process, the emitted light was very weak and the line spectra of atoms were observed mainly; in the middle process of the DDT, the emitted light became strong and the spectra observed consist of line spectra of atoms,band spectra of molecules plus the continuous spectrum of the thermal radiation; when the detonation was formed, the emitted light got very strong , and the spectra acquired consist of both line spectra of atoms and band spectra of molecules superimposed on the strong continuum of the thermal radiation .In addition,the higher resolution spectra of the epoxypropane in the process of DDT were also detected with 1200g/mm grating.According to characteristic electronic spectral bands of some molecules and radicals composed of C,H and O atoms,by analyzing the higher resolution spectra obtained,the main intermediate reaction products CO,CHO,OH, CH and C2 of the epoxypropane in DDT process have been identified.Using the corrected data of the higher resolution spectra measured from six different side windows of the shock tube,curves of the optical radiant intensity of main reaction produsts versus the DDT distance from the ignition point have been obtained.These curves reflect the spatial evolution of the reaction products during the DDT process.After comparing and analyzing the data obtained,the molecule CO,the radicals CHO ,CH,C2 and OH have been determined as main species which affect the DDT process greatly.In the end of the paper,for obtain the temperature of detonation,the emission light is transmitted by optic fiber(implanted in the explosives) and the spectrum is measured with the visible light band.The detonation temperature is derived from fitting the calculated emission spectrum of the temporal detonation processes with Plunck blackbody formula by least squares principle.The instantaneous spectrum measuring technique is a powerful way to obtain microscopic information about the fast reaction process of the fuel materials.The information of spectra about the DDT microscopic process of epoxypropane in this paper may provide scientific basis for the microscopic mechanism analysis of epoxypropane.