摘要:

The problem of the burning of a monopropellant droplet has been studied considering variable properties. It is shown that the burning rates as obtained by using constant property assumption compare well with those obtained by considering variation of properties, provided the constant properties are evaluated at a suitable average temperature. The exponentpin the correlationṀa∼Ṙsap(Ṁais a dimensionless mass flow rate andRsais a dimensionless droplet radius) is shown to vary between the limits 1 and 2;p= 1 for pure vaporization andp= 2 for strong burning. The same limits are attained for very large activation energy and/or very small droplet radius, and for very small activation energy and/or very large droplet radius respectively. A simple explicit expression forṀain terms ofṘsaB(transfer number) and τc(the centroid of the reaction rate) is suggested.

ISSN:0010-2202    

DOI:10.1080/00102206908952187

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The extension of the quasi-steady radially symmetric theory of liquid-droplet vaporization and homogeneous combustion to solid fuels and additives requires several basic modifications. One relatively simple extension, undertaken here, permits the gasification process al the two-phase interface to be modelled not by adiabatic sublimation, but by finite-rate heterogeneous chemical reaction. Such an extension by itself allows the burning of solid spheres of carbon to be adequately described. In particular, for carbon spheres, surface reactions involving production of carbon monoxide (by consumption of oxygen or by reduction of carbon dioxide) and of carbon dioxide (by consumption of oxygen) may be coupled with a bipropellant homogeneous reaction between carbon monoxide and oxygen. More general results for the net mass transfer rate (the Sherwood number) with nonequilibrium reversible heterogeneous reactions than previously obtained are presented. Further, closed-form results are derived for special cases of simultaneous gas-phase and surface reactions. Invariance of the Sherwood number to details of the chemistry in several circumstances indicates that gross agreement between theory and experiment is possible even with incorrect models of the kinetics. Finally, reasons for the success of “additive times” in predicting lifetimes of particles gasified under rate processes are presented.

ISSN:0010-2202    

DOI:10.1080/00102206908952188

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

An integral method is developed to treat by ordinary differential equations the problem of lime-wise development of the viscous, heat and mass conducting layer over the leading edge of a volatile droplet instantaneously immersed in a gas stream. Attention is restricted to the vicinity of the stagnation point. Weak reactions in the sense of small heat release and major species consumption, characteristic of the induction period, are treated.

ISSN:0010-2202    

DOI:10.1080/00102206908952189

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102206908952190

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The influence of hydrogen concentration on the characteristics of fully developed self-sustained detonation waves propagating in H2—CO—O2mixtures at one atmosphere initial pressure was experimentally investigated by means of Q-switched pulsed laser schlieren photography. The main aspects of interest were the reaction zone thickness and the detailed wave front structure. The concentration of CO in the fuel ranged from zero to 97.5 % by volume; pure CO—O2mixtures did not detonate. A rotating prism Q-switched laser was modified to achieve the synchronization purpose, thus the need for an expensive electro-optical Q-switching device was eliminated. The laser schlieren photographs indicate that the wave front becomes nonplanar and the spacing between the transverse waves becomes larger as H2is replaced by CO in H2—O2mixtures. It is suggested that weak shocks, produced by secondary explosions, are the propagating mechanism for the trailing portion of the transverse waves. Experimental results show that the reaction zone thickness increases sharply with increasing CO concentration only when the CO concentration exceeds about 75% of the total fuel. A simple relationship between the reaction zone thickness and the hydrogen concentration in the mixture is formed. It is also demonstrated that the reaction zone thickness is affected by the channel size; it becomes thicker in smaller channels.

ISSN:0010-2202    

DOI:10.1080/00102206908952191

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor