摘要:

Experiments on well-ventilated cross-piles of wood sticks burning in room air show that the instantaneous mass of the pile normalized with respect to the initial mass is proportional to time/(individual stick thickness)1.6. Experiments conducted by the present authors on isolated α-cellulose cylinders burning free convectively in room air indicate that while the normalized instantaneous mass correlates with (t/d1.6), the internal temperature profiles correlate with (t/d2) —tanddrespectively denoting time after ignition and specimen diameter. In this paper an approximate analysis is presented to explain this behavior as a consequence of the interaction of heat conduction and finite rate kinetics of thermal decomposition. If Miis the initial mass (gms), α is thermal diffusivity of the wood species (cm2/sec) and the stick sizedis in centimeters, it is shown that the rate of burning can be estimated as 0.9268Miα0.8/d1.6gm/sec.

ISSN:0010-2202    

DOI:10.1080/00102207008952229

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

In this paper the topic of investigation is the extent of internal convection caused by the flow of pyrolysis gases in a decomposing α-cellulosic body. The argument is proposed and applied to data obtained on cellulose cylinders as well as all the available burning rate data of the literature. The primary conclusion of this work is that, all too frequently, in transient pyrolysis of cellulosic bodies, the energy flux by the internal convection can rival that by the inward conduction.

ISSN:0010-2202    

DOI:10.1080/00102207008952230

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A study was made of the numerical solutions of the equations representing heating of a reactive, homogeneous, opaque solid by a constant flux of energy. Depletion of reactants was considered. Critical conditions for attainment of ignition were defined in terms of behavior of the surface temperature due to self heating after termination of external heating. For a wide range of physical and chemical parameters, it was found that: (1) critical conditions were relatively insensitive to reaction order; (2) the critical ignition temperature has an upper limit approximately equal to the adiabatic solid phase reaction temperature; (3) for activation energies below a critical value, typically 20 kcal/mole, heating cannot produce ignition unless the adiabatic thermal explosion time of the solid is unacceptably short; (4) critical ignition conditions are correlated to an accuracy of 4 % by empirical expressions including the physical and chemical properties and based on simple heat balance arguments.

ISSN:0010-2202    

DOI:10.1080/00102207008952231

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The effects of the velocity vector upon the combustion processes in a liquid rocket are examined concerning their influence on linear stability. These effects, which have often been neglected in the past, are shown to potentially have extreme importance in stability criteria for both longitudinal and transverse modes. The magnitude of velocity effects is shown in some cases to require new analytical treatment of the system stability and to possibly require new interpretation of past experiments.

ISSN:0010-2202    

DOI:10.1080/00102207008952232

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The droplet vaporization, wake burning, and chemical kinetics processes are investigated theoretically with a view toward explanation of a mechanism which can cause combustion instability in liquid propellant rockets. Past research efforts and a new treatment of the unsteady vaporization process are drawn together lo provide a reasonably unified picture of unsteady mechanisms. It is shown that while vaporization can be an important contributor to chamber stability criteria, it cannot be the major supporting mechanism. Other processes are indicated which hold more promise for future research.

ISSN:0010-2202    

DOI:10.1080/00102207008952233

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A model is formulated for radiant ignition of a solid propellant, accounting for in-depth absorption of radiation and surface reaction between solid fuel and gaseous oxidizer. Mathematical solutions are obtained in the limit of infinite absorption coefficient. From calculated surface temperature histories, several ignition criteria are compared. Conditions are established under which the choice of ignition criterion influences ignition time; it is shown that ignition times based on constant ignition temperature can be greatly in error at high heating rates. From the dimensionless parametric solutions, dependence of ignition time on oxidizer concentration, pressure and other quantities is extracted. At low pressures and equal solid and gas temperatures, oxidizer mass fraction and pressure affect ignition time only through their effect on oxidizer concentration, but at high pressure or under shock-tube ignition conditions, the additional effect of pressure on transport properties becomes increasingly important. Chemical kinetics constitute the principal factor determining ignition time, while oxidizer diffusion rate imposes a limit on attainment of ignition without significantly affecting ignition time.

ISSN:0010-2202    

DOI:10.1080/00102207008952234

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor