摘要:

A simplified model has been developed for the flame-spreading over the surface of the flat double-base propellant in the turbulent boundary layer which was experimentally studied in Part I. The model is based on the heat transfer from the gas-phase to the solid-phase and a critical temperature ignition criterion. The flow during flame-spreading was simulated by the flow in the turbulent boundary layer with blowing in the present model and the heat transfer with blowing has been experimentally studied. The blowing effect of burned gas on the heat transfer coefficient is found to be important for the flame-spreading in the boundary layer. The flame-spreading distance and the distribution of the unburned surface temperatures were predicted by the present model. In addition, the secondary ignition, which occurred in the unburned region downstream far from the flame front, was predicted for a low main stream velocity by the present model. The results were in good agreement with the experimental results.

ISSN:0010-2202    

DOI:10.1080/00102208208952536

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A model for predicting physical characteristics of combustion in the recirculating, chemically-reacting flow in the base region of a rocket exhaust plume is described. The nozzle jet and the free stream are considered as supersonic or subsonic, mixing turbulently to form an axisymmetric and compressible free-boundary layer. The turbulence is accounted for by a two-equation model, which solves the transport equations for the local kinetic energy of the fluctuating motion and its dissipation rate. Full account is taken of heat-transfer effects, and a detailed finite-rate chemical-kinetics scheme is included, which allows for any number of species. Simultaneous solutions of the elliptic differential equations are obtained by a finite-difference technique, and the chemical-kinetic equations are solved by a procedure developed by Pratt and Wormeck (1976). The prediction procedure, composed of the mathematical model and its solution algorithm, is applied to predict the helds of variables for representative supersonic-missile flight conditions, with subsonic recirculating base-flow, and a full description of the chemistry. The results are presented and discussed.

ISSN:0010-2202    

DOI:10.1080/00102208208952537

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Data on the overall conversion of coal-nitrogen to NOxwere obtained at 1250 K and 1750 K for a residence time of one second. The conversion of coal-nitrogen to NOxdecreased monotonically with increasing fuel/oxygen equivalence ratio and decreased slightly with increasing temperature. Oxidation experiments were also carried out on char in order to separate the contribution to NOxemissions of the char from that of the volatiles. The char used was prepared by the pyrolysis of coal at a temperature and residence time corresponding to those of oxidation experiments. The conversion to NOxof char-nitrogen was lower than the corresponding value for coal-nitrogen. It was found that volatilized nitrogen compounds accounted for a major fraction of NOxproduced from coal-nitrogen, especially at high temperatures and low fuel/oxygen equivalence ratios.

ISSN:0010-2202    

DOI:10.1080/00102208208952538

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A systematic study was undertaken on the combustion and thermal decomposition of pelletized Ammonium Perchlorate (AP) to investigate the effects of pelletizing pressure and dwell time. At constant pressure, increasing the dwell time results in an increase in the burning rate up to a maximum and thereafter decreases it. The dwell time required for the pellets to have maximum burning rate is a function of pressure. The maximum burning rate is the same for all the pressures used and is also unaffected by increasing, to the range 90–250 μ, the particle size of AP used. In order to explain the occurrence of a maximum in burning rate, pellets were examined for their thermal sensitivities, physical nature and the changes occurring during pelletization with dwell time and pressure. The variations are argued in terms of increasing density, formation of defects such as dislocations leading to an increase in the number of reactive sites, followed by their partial annihilation at longer dwell times due to flow of material during pelletization.

ISSN:0010-2202    

DOI:10.1080/00102208208952539

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The aim of the present work is to carry out parametric analysis of unsteady combustion of composite propellants taking into account all the experimentally observed phenomena. The theoretical analysis is based on the time scale analysis of pressure transient, propellant, condensed phase reactions, gasphase and ammonium perchlorate particle size. Three influence factors relating to gasphase heat feed back and condensed phase energy release are used as independently variable parameters. The influence of each of these influence factors on the predicted dynamic burning rate is found. A mechanism of unsteady combustion of composite propellant subjected to rapid depressurization is postulated. The predicted dynamic burning rates are compared with the available experimental results.

ISSN:0010-2202    

DOI:10.1080/00102208208952540

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Measured amounts of oil were added to the engine cylinder of a single-cylinder CFR engine to determine the effect of oil layers on exhaust hydrocarbon emissions. The exhaust hydrocarbon concentration increased in proportion to the amount of oil added when the engine was fueled on isooctane. Addition of 0·6 cm3of oil produced an increase of 1000 ppmC in exhaust hydrocarbon emissions at a coolant temperature of 320°K. Gas chromatographic analysis of the exhaust determined that fuel and fuel oxidation species, not oil oxidation products, were responsible for most of the increase. Similar experiments performed with propane fuel showed no increase in exhaust emissions when oil was added to the cylinder. These measurements have determined that the increase in tailpipe hydrocarbon concentration consists of fuel related species and is proportional to both the amount of oil added and the solubility of the fuel in the oil. Thus, we believe that the principal source of this increase in exhaust hydrocarbon concentration is the dissolving of fuel in the oil layer during compression with subsequent release into cooling burned gas during the expansion stroke.

ISSN:0010-2202    

DOI:10.1080/00102208208952541

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A spatially homogeneous explosion with chain branching is studied using the method of activation energy asymptotics. The model consists of a chain branching reaction which is followed by a chain termination reaction. Both these reactions are considered exothermic, in general, with the former having a large and the latter an O(l) amount of activation energy. We examine the complete range of values of A, the reaction rate ratio of these two reactions. The object is to calculate the induction period of such branched chain explosions. Wherever appropriate, two types of situations are considered: the chain carrier at the beginning of the branching reaction is present in (i) small (ii) moderate amounts. It is found that the results may differ substantially depending on the range of values of A and the conditions (i) and (ii).

ISSN:0010-2202    

DOI:10.1080/00102208208952542

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The influence of temperature fluctuations on the Arrhenius model for chemical reactions is estimated for idealized low-level turbulence and large values of non-dimensional activation energy.

ISSN:0010-2202    

DOI:10.1080/00102208208952543

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Numerical solutions for the problem of a free convection, diffusion flame burning on a vertical fuel surface have been obtained for Lewis number from 0·05 to 10. Results are presented for the effect of Lewis number on the temperature and concentration profiles and on the burning rate.

ISSN:0010-2202    

DOI:10.1080/00102208208952544

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor