| Autor: |
Welby G. Courtney |
| Rok vydání: |
1963 |
| Předmět: |
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| Zdroj: |
Symposium (International) on Combustion. 9:799-810 |
| ISSN: |
0082-0784 |
| DOI: |
10.1016/s0082-0784(63)80087-9 |
| Popis: |
No definitive experimental work has been done with condensation via homogeneous nucleation and very little work apparently has been done with condensation in nozzle flow, where the complications of a dynamic system are added. A review is given of the theories of homogeneous nucleation and of growth during condensation from the vapor phase. At the present time the usefulness of these theories remains uncertain or at least quite arguable. The principal current theoretical problems are the kinetic and thermodynamic behavior of ultra-small particles and particularly the accommodation coefficients for the growth of these particles and the possibility of non-Maxwellian vapor-particle collisions when growth is rapid. A detailed theoretical analysis of condensation in nozzles requires solution of the differential equations of nozzle flow together with nucleation-growth kinetics. With rocket nozzles the influence of chemical reactions among the variety of vapor species on nozzle aerodynamics and particularly on nucleation and growth kinetics must be included. The mathematical equations relating nucleation kinetics to chemical reactions are briefly noted in this paper, but the relevant specific rate constants are unknown. A semiquantitative insight into condensation in nozzles may be obtained by comparing supersaturations and the simple model of liquid-drop homogeneous nucleation and collision-frequency growth kinetics to the local residence times in the nozzle. This comparison suggests that nonsteadystate nucleation may be a bottleneck in certain cases and that even if particles are nucleated their subsequent growth may be too slow to permit appreciable condensation in the short times available in a nozzle. Clarification will require exact solution of the flow equations together with the 100 or so differential equations describing nonsteady-state nucleation [Eq. (2)] or an equation describing condensation [e.g., Eq. (28)]. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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