摘要:

There is increased interest in, and concern about, deposition and corrosion phenomena in combustion systems containing inorganic condensible vapors and particles ( salts, ash). To meet the need for a computationally tractable deposition rate theory general enough to embrace multielement/ component situations of current and future gas turbine and magnetogasdynamic interest, we present a multicomponent chemically “ frozen” boundary layer ( CFBL) deposition theory and demonstrate its applicability to the special case of Na2SC4deposition from seeded laboratory burner combustion products. The coupled effects of Fick (concentration) diffusion and Soret (thermal) diffusion are included, along with explicit corrections for effects of variable properties and free stream turbulence. The present formulation is sufficiently general to include the transport of particles provided they are small enough to be formally treated as heavy molecules. Quantitative criteria developed to delineate the domain of validity of CFBL-rate theory (Section 5) suggest considerable practical promise for the present framework, which is characterized by relatively modest demands for new input information and computer time.

ISSN:0010-2202    

DOI:10.1080/00102207908946899

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A general model is developed to describe the mass transport and heterogeneous chemistry which occurs during the gasification of porous coal char. The pore branching sequence depicts that each pore that reaches the exterior surface of the particle is the trunk of a tree. The gasification rate per pore tree is obtained analytically. The effects of Knudsen diffusion, continuum diffusion, and both adsorption and desorption kinetics are included. Each physical mechanism may limit the gasification rate within some range of pore size, particle size, gas temperature and gas pressure. The gasification rate per pore tree is integrated over a pore distribution function to determine the total gasification rate. In general, no single mechanism controls the entire gasification process. However, the known results of existing models are recovered in the extreme limits of kinetic and diffusion controlled gasification.

ISSN:0010-2202    

DOI:10.1080/00102207908946900

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The basic heterogeneous reaction rates for the oxidation of porous carbon char have been inferred from existing laboratory data. These rates have been used to verify the basic transport model described in Part I. Empirical verification has been obtained for temperalures between 630 and 2270° K, particle sizes between 4μ and 89μ diameter and for chars from high, intermediaie and low rank coals. The pressure dependence of the transport model has been verified only in the range of 0.1 to 0.2 atm of O2. Additional low pressure laboratory data are necessary in order to verify the basic model over a wider pressure range.

ISSN:0010-2202    

DOI:10.1080/00102207908946901

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A detailed chemical kinetic mechanism, involving 26 chemical species and 84 elementary reactions, is proposed for the oxidation of methanol. Within the scope of this mechanism, turbulent flow reactor and shock tube experimental data are used to determine rate expressions for several of the important reactions involving CH3OH and its intermediate product species, CH2OH. Calculations using the proposed mechanism and elementary reaction rates accurately reproduce experimental results over a combined temperature range of 1000-2180K, for fuel-air equivalence ratios between 0.05 and 3.0 and for pressures between 1 and 5 atmospheres. The resulting chemical kinetic model is then employed, together with an unsteady, one-dimensional numerical model for flame propagation, to predict the laminar flame speed of a stoichiometric methanol-air mixture. The calculated laminar flame speed is 44+ 2 cm/ sec and is in good agreement with experimentally observed values.

ISSN:0010-2202    

DOI:10.1080/00102207908946902

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

This paper reports on the measurement and analysis of time resolved thermal radiation from combustion of methane, ethane, and propane clouds formed from laboratory scale vapor samples initially contained within a soap bubble. The time scale of the radiant heat pulse was found to be the same as that of the fluid mechanical motion (Fay and Lewis, 1976). The time-integrated radiant energy flux, expressed as a fraction of the initial fuel heating value, was between 0.09 and 0.15 for these fuels, with some dependence on initial fuel volume. The radiation was correlated by a grey gas model, which assumed a uniform time-dependent temperature in a spherical cloud and a time-independent absorption coefficient. The grey gas temperature decreased monotonically during and after the period of combustion. The absorption coefficient was found to be a function of the initial fuel volume and fuel type; it was between 10−3and 10−2cm−1and decreased slightly with increasing initial fuel volume.

ISSN:0010-2202    

DOI:10.1080/00102207908946903

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The results of an investigation of the projectile impact sensitivity of a deflagrating composite explosive are described. The tests consisted in impacting small cylinders of the propellant with flat-ended projectiles of different diameters fired from guns at various velocities, and observing the impact reaction by an open-shutter camera, photocell, post inspection and weighing of the propellant fragments. The critical ( minimum) impact velocity required to produce a sustained reaction in the propellant decreased with increasing projectile diameter. The nature of the reaction depended on the diameter. At small diameters, the induced reaction was always detonation; whereas at the largest diameter the reaction was deflagration, whose intensity increased with increasing impact velocity. A higher critical velocity then again resulted in detonation. A model based on hot spot initiation in which a pressure-dependent effective hot spot concentration determines the rate of buildup of reaction after ignition is postulated to explain the results. Rapid pressure buildup causes detonation; whereas a low buildup rate allows rarefaction loss which results only in deflagration. The critical velocity threshold for inducing the ignition reaction is consistent with the critical energy concept.

ISSN:0010-2202    

DOI:10.1080/00102207908946904

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The ability of high- and low-carbon ashes to reduce NO levels in a synthetic flue gas stream has been examined in the temperature range from 350 to 1100 C. High-carbon ash removed all of the NO (up to 340 ppm) from the gas stream, while low-carbon ash had no effect on the NO level of the gases. The carbonaceous material in the ash, possibly in conjunction with CO formation processes, appears to play a major role in the depletion reactions. The gas phase CO, however, does not appear to have a significant role in these reduction processes.

ISSN:0010-2202    

DOI:10.1080/00102207908946905

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor