摘要:

The steady propagation of a convex laminar flame front in long channels is under consideration. In comparison to the previous theoretical efforts by Zel'dovich (1944), Tsien (1951), Chernyi (1954) and Borisov (1978) the existence of a stagnation zone fixed with respect to the flame front is taken into account. The flame front is supposed to be a hydrodynamic discontinuity with the known normal rate of propagation through the cold gas; the boundary surface of the stagnation zone is considered as a discontinuity of the tangential component of velocity, i.e. as a vortex sheet

ISSN:0010-2202    

DOI:10.1080/00102208008952419

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A simple and reliable gas chromatographic technique has been developed for the measurement of the concentrations of the nitrogenous species N2, NO, NH3, N2O and HCN in combustion products. Separations of the above species, along with H2, CH4, CO, CO2, and H2O were accomplished on a two column combination of Porapak T and molecular sieve 5A. The choice of the columns was based on an exhaustive literature survey, as well as tests on possible packing combinations. The separations were carried out at three constant temperature conditions of 28, 50 and 150°C. Lower detection limits of approximately 100 ppm were achieved for all of the species (200 ppm for Nha). Probe sampling in a flat flame burner supplied typical combustion product gas mixtures with various levels of the species of interest. Reliability of the nitric oxide concentration measurements was demonstrated by NO yields comparable to previous investigators in addition to nitrogen balances on lean NH3/CH4/O2/Ar flames. Nitrogen dioxide was not detected in the combustion products; however, the results were not conclusive due to the breakdown of NO2in the column.

ISSN:0010-2202    

DOI:10.1080/00102208008952420

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The combustion of a turbulent homogeneous mixture of propane and air within a duct having a stationary one-dimensional mean flow is modelled. Under the conditions chosen for the study, chemical kinetics factors are important and a relatively detailed chemical model is needed. A semi-global model for the combustion of hydrocarbon is used and simplifying assumptions are made which reduce the system of independent variables to that of temperature and CO2mass fraction. A two-dimensional probability density function is introduced to close the mean chemical production terms. The required equations for Favre averaged temperature, CO2mass fraction, turbulence kinetic energy and the mean square fluctuation of the temperature are solved numerically. Predictions are made of the profiles of mean quantities through the combustion zone under different initial temperature, turbulence intensities and dissipation length scales.

ISSN:0010-2202    

DOI:10.1080/00102208008952421

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A theoretical examination is made of the ignition of explosives by a hot, stagnant gas pocket (hot spot), such as may be produced in a porous material by impact or shock. The effect of the various factors that control the surface heating and ignition event over a wide range of conditions (including reaction buildup) are discussed. At low pressures the heat flux and ignition characteristics are controlled by the gas properties (for fixed material kinetics). The computed ignition energies of several explosives at 3 msec ignition time are in general agreement with the low pressure gas compression measurements of Bryan and Noonan. On the other hand, under high (shock) pressure conditions, the gas pocket size and material thermal conductivity also affect the ignition characteristics, and the effect of hot spot size is dominant. It is shown that relatively large gas pockets cannot ignite the material in microsec time periods, The calculations thus provide a detailed semiquantitative explanation of the experimental observation that gaseous heating at adiabatically compressed voids is not the cause of initiation of a shocked explosive.

ISSN:0010-2202    

DOI:10.1080/00102208008952422

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This paper is concerned with a study on pollutant emissions from a gas turbine during its transient operation. Exhaust gases of a small gas turbine are measured and analyzed during its accelerating and decelerating phases. Based on the results, the relation between the formation of pollutants and the thermodynamic and aerodynamic characteristics of the gas turbine are discussed. The total amount of NOx, CO and THC obtained by the analysis is compared with the amount estimated from the emission characteristics of the stabilized operation.

ISSN:0010-2202    

DOI:10.1080/00102208008952423

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The unsteady one-dimensional laminar isobaric propagation of a flame toward a wall, through a homogeneous fuel-lean premixture, characterized by large activation temperature, is examined under a Shvab-Zeldovich-type formulation, via numerical integration by the method of lines with spline interpolation. In particular, the effect of the boundary thermal constraint and of the Lewis-Semenov number, on the propagation in the immediate vicinity of a noncatalytic impervious planar wall parallel to the flame, is examined. Both an isothermal-wall constraint, for a series of values ranging from the initial cold temperature of the unburned premixture to the bulk-burned-gas temperature, and also an adiabatic-wall constraint, are considered. Persistence of unburned residual fuel, and occurrence of either large wall temperature or large wall heat transfer, are insights of interest in the context of current and proposed internal-combustion automotive engines. It is found that the largest gas-phase temperatures tend to be achieved at intermediate wall temperatures, for thermal diffusivity greater than mass diffusivity. In such cases, the release of chemical exothermicity, to enhance a “base enthalpy” of the premixture already augmented by significant heat transfer from the wall, leads to gas temperatures appreciably in excess of the bulk-gas adiabatic flame temperature. Inferences are drawn from the gas-phase aerothermochemistry concerning trade-offs in design requirements for ceramic-type, low-heat-transfer cylinder components.

ISSN:0010-2202    

DOI:10.1080/00102208008952424

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The combustion characteristics of freely-falling and suspended mono-sized coal-oil mixture (COM) droplets in heated air were investigated by studying the quenched samples using scanning electron microscope. Parameters varied include the volatility of the oil, the concentration and size of the coal particles, the residence time, the intensity of blowing, and the effects of water and surfactant addition. Results substantiate the formation of coat particle agglomerates upon depletion of the volatile oil components, and emphasize the importance of oil volatility and external convective motion on COM combustion. In particular agglomeration is not expected to be a serious problem for COM with No. 6 oil, although addition of oils with higher volatility widens the volatility differentials between the oil and coal components such that the agglomerate formation, heating, ignition, and thereby the total burning times are significantly prolonged. Addition of water may cause droplet swelling and fragmentation due to internal bubbling which, however, can be inhibited by moderate amount of internal circulation induced by the external convective motion. The possibility that agglomeration may be prevented under high pressure combustion is also discussed.

ISSN:0010-2202    

DOI:10.1080/00102208008952425

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A new technique is presented for predicting the generally neglected Soret and Dufour flux effects in laminar one-dimensional premixed gaseous flames. The time-dependent flame equations are transformed into a form which permits their solution to be directly obtained using methods in the literature that have been utilized for the classical-type flame problem in which the additional transport fluxes are neglected. Computed results, using the transformed equations, shed light upon the important role that thermal diffusion can play in accurately predicting the characteristics of hydrogen-air flames.

ISSN:0010-2202    

DOI:10.1080/00102208008952426

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The systematic addition of alcohol to the fuel and the incorporation of a catalyst on the surface of a Cooperative Fuel Research (CFR) diesel combustion chamber significantly suppressed soot formation. These effects were additive under the experimental conditions with 40–80 percent soot reduction observed.

ISSN:0010-2202    

DOI:10.1080/00102208008952427

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor