摘要:

The species balance equation is written for the perturbation of the species from equilibrium. This yields a form which is particularly useful in elucidating the relative roles of mixing and kinetics in turbulent diffusion flames and it appears to be a very well-conditioned equation for obtaining the amount of non-equilibrium. A novel linearization of the kinetic rate results in ready estimates for the amount of non-equilibrium and a criterion for the onset of a diffuse reaction zone. The general approach appears to have some value for other types of turbulent combustion and results in a very direct derivation of the Bray-Moss formula for the reaction rate in premixed turbulent flames.

ISSN:0010-2202    

DOI:10.1080/00102207908946870

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The major species disposition of nitrogen from pyridine, added to a propane-argon-oxygen stream burned in a jet-stirred reactor, was investigated. Fuel/oxidant equivalence ratio ranged from 0.9 to 1.5, residence time from 10-50 ms, and temperature from 1500-1900 K. Nitrogen mass fraction relative to propane plus pyridine was normally 0.01, in a few cases 0.02. Molecular nitrogen (measured by gas chromatography) included with nitrogen oxides (chemiluminescent analyzer) and ammonia and hydrogen cyanide (wet chemistry) indicated for each reactor setting a complete nitrogen balance consistent with an estimated random error of approximately 10 percent. Examination of accumulated results for over 20 best-quality cases suggested no systematic imbalance. The results were consistent with data from comparison runs using atmospheric air oxidant (hence no molecular nitrogen measurement) with fuel nitrogen provided in the form of pyridine again.

ISSN:0010-2202    

DOI:10.1080/00102207908946871

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Accelerated ageing studies for three composite propellant formulations, namely polystyrene (PS)/ ammonium perchlorate (AP), polymethylmethacrylate (PMMA)/AP and poly phenol formaldehyde (PPF)/AP have been carried out in the temperature range of 55-125°C. Measurements of the ultimate compression strength (Uc) and isothermal decomposition rate (TD rate) were monitored as a function of storage time and temperature. The change inUcwas found to be linearly dependent on the change in TD rate irrespective of the propellant systems. Analysis of the results further revealed that the cause of ageing for bothUcand burning rate (r) is the thermal decomposition of the propellant. The safe-life for the change in mechanical properties was found to be higher compared to the change inrfor PS and PMMA based propellants.

ISSN:0010-2202    

DOI:10.1080/00102207908946872

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The influence of fuel composition on smoke emission/combustor wall temperatures has been studied in a laboratory-scale gas-turbine-type combustor over the range of operating conditions of modern turbine combustors and as a function of combustor design. Fuel hydrogen content is shown to give the best prediction of smoke emission and of variations in flame tube wall temperature caused by changes in flame radiation. The major finding is that the influence of fuel composition on smoke emission/flame radiation falls virtually to zero at combustor pressures above about 10 bar. Significant reduction in sensitivity to fuel composition can also be obtained by varying combustor design and are tentatively correlated with increasing combustion intensity. The implication of these effects for aircraft operation is discussed and an explanation for the results is put forward based on changes in the chemical mechanisms leading to soot formation.

ISSN:0010-2202    

DOI:10.1080/00102207908946873

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The use of computer based prediction procedures to assist design is still virtually unknown. This paper argues that faced with the enormous complexity of typical design problems, the combustion engineer would be more than satisfied if he had access now to general prediction procedures of only qualitative precision. It contends that existing turbulence and combustion modelling can provide this. The need for computer economy is the controlling factor and the present lack of a procedure combining economy with geometric flexibility is only too apparent. The paper outlines two immediate priorities for combustion model improvement: the need for careful validation of manageable simulations of the effects of fluctuating density, and the necessity to allow for non-equilibrium of the overall reaction in diffusion flames. The latter requirement is supported by recent validation evidence.

ISSN:0010-2202    

DOI:10.1080/00102207908946874

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The properties of flames supported by pyrolysis of commercially available urethane mattress foams are described. The flame shape, flame growth, some species concentrations, solid and gas phase temperatures, and mass loss are measured during a six minute period after ignition. Functional descriptions of these empirical histories of the flame radius and height, flame spread and mass loss rates are presented. Using a simple cone-cylinder model for the flame shape, measured temperatures, soot volume fraction and H2O and CO2concentrations, flame emisstvities in the homogeneous, nongray approximation are calculated. With this information the radiant heat transfer to the urethane and the surroundings is predicted. From comparison between predicted and experimental mass pyrolysis rates, convective heating of the mattress is shown to be negligible. Comparisons are also made with independent measurements of radiant flux and mass loss. Good agreement is obtained.

ISSN:0010-2202    

DOI:10.1080/00102207908946875

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The reaction between NO2and CO has been studied in a single pulse shock tube in the temperature range 950-1500 °K and at a total concentration of approximately 2.5× 10−5moles/cc. Both the measured ratios of ([CO2]/[CO])1 and ([NO]/[NO2])1 have been used in separate series of experiments to examine the reaction

ISSN:0010-2202    

DOI:10.1080/00102207908946876

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Although the detailed oxidation chemistry of carbon monoxide, hydrogen and methane is understood, present understanding of the high temperature oxidation of more realistic fuels and fuels derived from the conversion of coal and other fossil forms is very limited. Studies are currently underway to elucidate oxidation mechanisms of the higher order aliphatics and olefins. However, less research is directed towards evaluating the detailed oxidation mechanisms of the aromatics. Fuels derived from coal and other fossil fuels characteristically have aromatic contents which vary from about 35 to 85 percent. Although under laboratory controlled conditions it should be possible to burn these fuels with respectable combustion efficiencies, it must be recognized that aromatics are notorious for soot and coke formation. Sooting can cause operational difficulties by increasing flame radiation to surfaces which must remain cool, as well as by coating surfaces and thus reducing overall heat transfer rates. Further, although it is expected that complex compounds can be formed during the oxidation of the aromatics, it is not known explicitly which compounds are formed, whether they can survive in cool zones of an actual combustion process, or whether they will be environmentally acceptable. As well as providing an extension of an earlier review (Minkoff and Tipper, 1962), the present communication is intended as a brief review of aromatic oxidation to aid researchers interested in the combustion problem posed by these compounds.

ISSN:0010-2202    

DOI:10.1080/00102207908946877

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor