THE ANALYSIS OF THERMAL DISSOCIATION OF HYDRAZINE
| Autor: | Cheng-Hsien Shen, 沈政憲 |
|---|---|
| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 Hydrazine is widely used in many industries especially in rocket propulsion. The main purpose of this thesis is to develop a homogeneous detailed hydrazine decomposition mechanism. Detailed kinetic modeling was used to justify the mechanism with the half-life times of hydrazine decomposition measured by Michel’s shock tube experiment at 1100K-1600K and 6atm-10atm. Statistical method of solution mapping was employed to simplify the modeling process. The present verified N/H mechanism involves 12 species and 29 elementary reactions. The results calculated by the proposed mechanism adequately satisfy Michel’s observation of hydrazine decomposition at all conditions. From path analysis, after NH2 first produced by (R-14) initially, the reaction N2H4+NH2→N2H3+NH3 (R60) follows by the branching reaction N2H3+M→NH+NH2+M (R56) were significant for N2H4 dissociation at low temperatures(900K-1000K). It appears a long induction period of hydrazine decomposition. That is, the characteristics of chain reaction appeared as NH2 to be the chain carrier. At higher temperatures, the rate of (R-14) as well as the rates of the dissociation of intermediate species including NH2 rapidly increased. The characteristics of “chain reaction” diminished and the overall reaction behavior is closing to first-order decay. In this analysis, the pressure effect on reaction path was not obvious, however, it increases the decomposition rate of hydrazine. By matching the calculated half-life times and modeling the dissociation of hydrazine as a first-order decay process ( ), this research deduced the overall rate constants at three different pressures with Arrehnius expression as K1,1atm=9.30xE+10exp(-157(kJ/mole)/RT); at P=1atm K1,5atm=7.58xE+11exp(-173(kJ/mole)/RT); at P=5 atm K1,10atm=2.09xE+12exp(-179(kJ/mole)/RT);at P=10atm. at temperatures 1000K-1600K, which the apparent activation energy was increased with increasing pressures. The mechanism of N/H/O reaction system with 21 species and 125 elementary reactions was also constructed to simulate the effect of water addition to the dissociation of hydrazine. The results showed the presence of water do not alter the dissociation path and acted as a thermal sink at the temperatures investigated. Water addition and increasing pressure suppress the equilibrium ammonia dissociation ratio (Xd), an index related to hydrazine thruster’s performance. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|