|M.Sc Student||Rozenblum Vladimir|
|Subject||Computational Study of Infrared Emission from Rocket|
|Department||Department of Aerospace Engineering||Supervisor||Professor Josef Stricker|
|Full Thesis text|
This paper presents a research of radiation inversion methods and aims at developing new and reliable techniques to find chemical concentration of IR-active species and thermodynamic data of rocket plumes.
Since measurements of the radiation spectrum (with necessary wavelengths range and resolution) of exhaust plumes are practically not found in academic literature, we implemented simulation of radiation emission. The radiance simulation was developed in the study and was based on the methods described in scientific literature. The simulation used the given profiles of temperature and partial pressure of the IR-active species.
We used a number of algorithms to achieve the temperature and partial pressure profiles by inversion of the radiation field:
1) A method based on Abel transformation. In the cylindrical coordinate system the spectral radiance intensity and spectral transmittance expressions become equivalent to the formula of the Abel transformation. The Abel method provides good performances of 10% accuracy in the temperature calculation (based on the temperature and partial pressure profiles) and down to 30% accuracy in calculating the partial pressure of the dominant IR-active species.
2) If the spectral radiance intensity and spectral transmittance are known, we can also use a "direct" method. The temperature and partial pressure received from the relation of the spectral intensity and spectral transmittance. This method provides the same accuracies of the Abel method, but requires more computational time.
3) In addition, we suggested a method to determine of the temperature and the partial pressure based on the measurements of spectral radiation intensity only on two wave-numbers. The temperature was obtained from correlation of spectral radiation intensity measured in two wave-numbers. The partial pressure was calculated by comparison between measured and calculated spectral radiation intensity by iteration process. The accuracy of this method was lower than the accuracy of two previous methods.
We examined the above methods with five radiation profiles and compared the performance of these methods for 5 different initial profiles of temperatures and partial pressure. The best results were achieved for smooth profiles of temperature and partial pressure. For temperature and partial pressure profiles with periodic behavior transformation the errors were even more serious.
In this work we performed radiation simulation/inversion with 4 species: H2O, CO2, CO and HCl.
The research of rocket plumes with the use of radiation inversion is barely covered in academic literature. Therefore, the methods presented in the thesis are an important instrument for the study of rocket plumes.