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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

HEAT IGNITION MODELLING TO AN ENERGETIC PARTICLE EXPOSED TO A THERMAL PLASMA

Get access (open in a dialog) DOI: 10.1615/IHTC11.4530
pages 451-456

Resumo

Ignition and enhanced burn of solid or liquid propellants using a thermal plasma as an external heat source is a concept of growing interest. Up to now the majority of work has been concentrated on experiments. However, the experimental results provide only limited information.
Based on most common approximations on particle heat transfer exposed to thermal plasma and considering a typical range of Reynolds number and situations without and with evaporation, an attempt is made in this paper to simulate the heat ignition process encountered in the calculation of the heat transfer rate to a single energetic sphere under plasma condition. The approach used is theoretical.
In order to maintain this study relevant to related practical problems, the computations were first carried out for the relaxation time of the thermal boundary layer around the particle whose size is in the order of millimeters. A model is applied in which the surface exposed to the thermal plasma is assumed to form a plasma boundary layer, named vapour shield, which is characterized by large temperature and density gradients. To understand the nature of the ignition mechanisms, numerical simulations were also carried out for the energetic particle without vapor shield immersed in plasma and the conventional heat ignition of an energetic particle.
These theoretical analyses show that a fraction of the incident energy is absorbed into the boundary layer and the net heat flux to the surface will be reduced, the delay time of ignition will be extended compared to that of particle without vapor shield. However, the delay time of ignition is still less than that of conventional heat ignition. From the results presented here it seems that the burn process of the propellant will be affected by the development of the boundary layer, and the burning rate may be limited by the flame vapor shield at the combustion flame temperature.