摘要:

The principle of heat recirculation in combustion systems is analyzed for the case where no direct mixing of reactants and products occurs. The concept leads to a general treatment, the restriction of associating flame temperature with the initial mixture stoichiometry and fuel heating value being removed in burners which rely on an enthalpy excess over initial and final states. This has important consequences particularly for reactants of very low heat content. Otherwise nonflammable mixtures may be burned by recirculating heat so as to increase the temperature in the reaction zone without generating a high final temperature.

ISSN:0010-2202    

DOI:10.1080/00102207308946644

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Experimental composition maps have been obtained of four H2-air turbulent diffusion flames of varying diameter but constant Reynolds number. Nitric oxide levels were found to scale with a characteristic “jet time,” modified to include the effects of buoyancy on flame shape. A comparison is made between present measurements, those of Kent and Bilger (1972), and a simple model of NO formation. The results suggest that the rate of NO formation is not predictable on the basis of fluctuating adiabatic equilibrium kinetics but requires consideration of turbulent combustion in detail and possibly the effects of excess radical concentrations.

ISSN:0010-2202    

DOI:10.1080/00102207308946645

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A theoretical model describing radiative ignition of a solid fuel is constructed and is numerically analyzed. The model includes the effects of gas phase reaction and a finite value of the absorption coefficient of the solid (in-depth absorption of incident radiation). It is found that the gas phase reaction must be included in the model in order to understand radiative ignition of a solid fuel and to find its ignition boundary. The in-depth absorption of the incident radiation by a solid fuel significantly affects the ignition delay time. The results indicate that there is a finite range of values for pyrolysis or gas phase reaction activation energy for which ignition will occur. This finding has a direct bearing on efforts to reduce material ignitability.

ISSN:0010-2202    

DOI:10.1080/00102207308946646

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Chemiluminescence in the visible has indicated the production of electronically excited products in the low pressure reactions of alkaline earlh metals with oxygen, halogens, halogen compounds and other oxidants. Thermochemical calculations on many such systems have indicated energy release more than adequate for electronic excitation of the product molecules. Comparisons of radiative lifetimes, rates of chemical reaction and col-lisional de-excitation indicate the possibility of population inversion and chemical laser action based on such electronically excited product molecules.

ISSN:0010-2202    

DOI:10.1080/00102207308946647

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A model of boron ignition treating the inhibiting effect of a boric oxide coating has been developed. Transient differential equations describing the generation and removal of the oxide and associated thermal effects along with heat transfer between the particle and surroundings have been derived, converted to difference form and programmed for computer solution for determination of ignition limits and ignition times. Predictions for particles studied by Macek in a flat-flame burner have been compared with experimental results—agreement is good for dry gas cases, but poor when the gas stream includes water. The program has been used to predict effects of initial oxide thickness, particle size, pressure, oxygen content, initial particle temperature, gas temperature and surroundings radiation temperature on ignition. In addition, the original differential equations have been treated by a stability analysis to determine ignition limits—excellent agreement is found between results obtained with the stability analysis and the numerical analysis.

ISSN:0010-2202    

DOI:10.1080/00102207308946648

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Flame velocities in premixed sprays were predicted either from an exact theoretical model in which both a realistic size distribution of droplets and their equations of motion were considered or from simplified models in which either of the above factors or both were replaced by appropriate assumptions. As a result, considerable differences in motion and burning position were predicted between droplets of different sizes even for a rather fine spray. Though the simplified models give results qualitatively similar to the exact one, quantitatively the models in which the equations of motion of droplets are replaced by the assumption of constant-velocity motions of droplets give higher flame velocities, while the models with the assumption of zero-relative velocities between droplets and gas give flame velocities lower than the exact model. The simplified theoretical model in which the spray is replaced by a monodisperse droplet cloud moving with a constant speed gives flame velocities sufficiently close to (hose obtained with the exact model. The thermal eddy diffusivity in the flame zone appears to be close to that in approach flow for a lean mixture ratio around flame stability limit, being amplified to an increasing extent from the value in approach flow as the mixture ratio increases richwards.

ISSN:0010-2202    

DOI:10.1080/00102207308946649

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

The kinetic operation of a thermal exhaust manifold reactor is investigated experimentally utilizing a steady flow vitiated engine exhaust plus secondary air mixture. Engine conditions are simulated by exactly duplicating the gas temperature and the mole fractions of hydrogen, oxygen, and carbon monoxide. These parameters are independently variable, and thus the important chemical processes may be studied individually. Preliminary results have elucidated the source of luminosity (a phenomenon noted during engine experiments) and tend to confirm the importance of hydrogen in the ignition process.

ISSN:0010-2202    

DOI:10.1080/00102207308946650

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

While ions are known to exist in hot hydrocarbon flames, their initial point of production has been uncertain. Ion production arises when a low temperature (800 °C) blue flame, characterized by formaldehyde chemiluminescence, undergoes transformation with increased oxygen concentration into a green flame. The low temperature green flame is also accompanied by CH and C2visible emission.

ISSN:0010-2202    

DOI:10.1080/00102207308946651

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

An experimental sandwich study was conducted using hydroxyl terminated polybutadiene (HTPB) binder, compacted polycrystalline ammonium perchlorate (AP) and the catalysts copper chromite (Harshaw Catalyst CuO202) and iron oxide (ferric oxide). Cinephotomacrography at a latent magnification of 2:1 was used, and the pressure range studied was 600 to 3200 psia. Catalysts were added in the binder, in the oxidizer, or at the binder-oxidizer interface. Several conclusions concerning the mechanism of catalytic activity and the behavior of composite propellants were deduced from a careful examination of the film and the associated sandwich burn rates. Comparisons were made between previous results, obtained with carboxyl terminated polybutadiene (CTPB) at 600 and 2000 psia, and the present study using HTPB.

ISSN:0010-2202    

DOI:10.1080/00102207308946652

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor