摘要:

Heterogeneous processes have been identified as important in determining levels of exhaust emissions from liquid-fueled gas turbine engines. From correlations of NO and CO emissions indices with differential fuel injection pressure, a simplified physical model of the spray combustion process in a turbine combustor has been developed. This model not only is consistent with previous experimental data obtained in this laboratory, but also assists in understanding the successes and failures of analytical combustor models available in the open literature.

ISSN:0010-2202    

DOI:10.1080/00102207308946634

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A 0.83 cm porous sphere, coated with a thin film of liquid fuel, was used for the measurement of preignition vaporization rates and incipient ignition temperatures for three fuels:n-octane,n-decane, and ethanol. The vaporization rate was measured using a feed line to the center of the sphere, supplied with fuel from a variable flow ratesyringe pump. Measurements were carried out in a specially constructed furnace where the temperature and ambient oxygen concentration could be adjusted for a wide range of values. Pre-ignition evaporation rates could be predicted with reasonable accuracy for temperatures that were near the ignition point using analysis that does not include chemical reactions. The calculations accounted for the influence of free convection and radiation. Data showing the influence of ambient oxygen concentration on the measured incipient ignition temperature agreed qualitatively with previous theoretical predictions. The influence of wall radiation on ignition temperature was relatively small for the sphere size tested and appears to be negligible for spray sized droplets. However, ignition data obtained from large spheres, of the size used in the present work, can only be used as a lower limit for the ignition point of small droplets. The present data also differs from previous results which were obtained using fuel droplets impinging on a hot surface.

ISSN:0010-2202    

DOI:10.1080/00102207308946635

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Experiments were performed using a shock tube in which both pure polymer and propellant specimens, mounted on the end wall, are suddenly exposed to a hot stagnant gas at about 1800 °K and 47 atm. The test gas consists of oxygen/nitrogen mixtures in which the oxygen mole fraction is varied from 0.18 to 1.00. The resultant ignition delay is observed to increase sharply as the mole fraction of oxygen is reduced and typical ignitability limits are 0.2 ˜ 0.3 mole fraction or 10 ˜ 15 atm oxygen partial pressure. Ignition delay time is found to be sensitive to total pressure as well as partial pressure. The effect of imbedded oxidizer is found to be significant when the ambient oxygen mole fraction is below 0.5 mole fraction. The theoretical ignition delay predictions of the gas phase and heterogeneous theories are shown to be too close for the experimental data to distinguish between them. A simple flat-surface stagnant exposure (a one-dimensional model) is found to be inadequate to resolve the question as to the dominant reaction in the ignition mechanism.

ISSN:0010-2202    

DOI:10.1080/00102207308946636

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

The problem of nonmetallized AP/composite propellant combustion is studied with the aim of coherently interpreting apparently diverse experimental data. Three fundamental hypotheses are introduced: the extent of propellant degradation at the vaporization step has to be specified through a scientific criterion; condensed phase degradation of AP to vaporizable fragments is the overall rate-limiting reaction; the rate of combustion in the gas phase is controlled by diffusive-mixing processes. Theoretical predictions of the regression rates of AP are seen to match well with experimental observations (both hot-plate pyrolysis and single-crystal deflagration). Theoretical curves of regression rate are presented for a typical composite propellant. The gas phase processes are discussed qualitatively. It is seen through analyses that either of the two familiar models for the gas phase (flame sheet approximation and uniform combustion) describes the general behavior adequately, hence de-emphasizing the role of gas phase details in propellant combustion.

ISSN:0010-2202    

DOI:10.1080/00102207308946637

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor