摘要:

—Experimental results are reported concerning the axial temperature profile, the exit conversion and NOxemission levels of a catalytic combustor for various inlet temperatures, velocities and fuel–air ratios.

ISSN:0010-2202    

DOI:10.1080/00102208108547507

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—This paper summarizes experimental results obtained during the study of the production of nitrogen oxides in a well stirred reactor burning hydrocarbons. First, the particular problem of NO and NO2probing has been addressed, and it has been shown experimentally that NO → NO2conversion actually occurs within the probe; but this conversion does not explain all the NO2measured, and a less important consumption of NOxNO + NO2also occurs. Second, Fenimore's “prompt NO” mechanism has been shown to be non negligible even for fuel lean combustion, at low residence times within the combustor. Some theoretical examination leads to the conclusion that both HCN production by CH + N2→ HCN + N and CH2+N2→ HCN + NH should be considered. Experimental results have shown also that the “prompt NO” depends on the fuel used. Finally, a detailed study of water addition on the NOxproduction with two different fuels at different equivalence ratio have shown that the water effect is not always purely thermal. In addition, it seems that this effect on the “prompt NO” can be well predicted using a chemical scheme involving the two reactions cited above.

ISSN:0010-2202    

DOI:10.1080/00102208108547508

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Three activation energies of comparable size are identified amongst the total of twelve that are present in a six-step reaction scheme for H2-O2combustion. Unique scalings for the inner and outer variables in an asymptotic model of a streamwise diffusion flame are found, based on the large activation energy limit. The resultant maximum-temperature versus Damköhler-number relationship is like the middle branch of the familiarS-curve, although the flame is of the near-equilibrium reaction-broadened type. The significance of these results in relation to flame extinction and theoretical modelling is commented upon.

ISSN:0010-2202    

DOI:10.1080/00102208108547509

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Measurements of a conserved scalar have been made in a horizontal, hydrogen turbulent diffusion flame burning in a co-flowing stream of air. Laser light scattered by refractory seeding particles was a measure of the fuel element mass fraction (the mixture fraction). Present values of the mean mixture fraction agree well with those obtained by probe-sampling. Results have been presented both as conventional statistics and as Favre or density-weighted statistics. Probability density functions of the mixture fraction are near Gaussian on the centre-line and are strongly skewed on the edge of the shear flow. Conversion to temperature probability density functions yielded results which were in qualitative agreement with those obtained by other techniques. These probability density functions revealed a widely-spread instantaneous reaction zone throughout the flame with combustion being indicated on the centre-line close to the nozzle. Spectra of the scalar fluctuations were also obtained.

ISSN:0010-2202    

DOI:10.1080/00102208108547510

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Hydrocarbons remaining in a wall quench layer have been proposed as a major source of hydrocarbon emissions in spark-ignited internal combustion engines (Daniel and Wentworth, 1962). Additional experiments using wall mounted sampling valves were subsequently carried out by Daniel (1967), Müller and von Watzdorf (1968), Weisset al.(1979), and Henningsen and Qvale (1980). Our paper presents the results of an experimental study of the quench layer also using a wall mounted sampling valve. The valve was electrohydraulically actuated and had uniquely small leakage and crevice characteristics. Our results do not support the contention that the wall quench layer is a major source of exhaust emissions. Hydrocarbons from other sources, as yet not quantified, such as those emitted from ring crevices, deposits or oil films appear to be likely contributors to exhaust hydrocarbons (Wentworth, 1971; Haskell and Legate, 1972; and Kaiseret al., 1980).

ISSN:0010-2202    

DOI:10.1080/00102208108547511

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—A second order closure theory developed earlier is used to study the processes influencing the turbulent velocity field in a premixed turbulent flame with degrees of heat release of practical interest. The flow field is chosen so that the time-averaged flame structure is one-dimensional and statistically stationary. Earlier work suggests that in the absence of turbulence production due to Reynolds stresses as is the case in a flame orthogonal to the oncoming reactants, the case we consider, dilatation resulting from heat release reduces the level of turbulence. In contrast it is shown here that with sufficient heat release turbulence increases on passage through the flame because of a buoyancy production mechanism arising from the self-induced, mean pressure gradient. This mechanism overwhelms the effects of dilatation at temperature ratios characteristic of combustion. The same buoyancy mechanism also causes counter-gradient diffusion as predicted in an earlier paper and as observed in recent experiments. Here adjustments are made to some aspects of the modelling required in the theory in order to achieve reasonable agreement with these new experimental results. Calculations are then carried out to establish the significance of the production of turbulence by this buoyancy mechanism at heat release rates characteristic of combusting flows. The physical interpretation of the present results and their importance in prediction methods for turbulent combustion involving premixed reactants are discussed.

ISSN:0010-2202    

DOI:10.1080/00102208108547512

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—A simple mathematical model is developed for propane fireballs, based closely on previous models for methane. The model predicts that LPG fireballs involving hundreds of tons of fuel can cause serious burns and start fires one kilometre or more away. Experimental facts are needed to improve the accuracy of such predictions.

ISSN:0010-2202    

DOI:10.1080/00102208108547513

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Thermal behaviour of ammonium perchlorate-aluminium composites is studied using differential thermal analysis, thermogravimetry and differential scanning calorimetry. Electrical resistivity studies throw light on the mechanism of ammonium perchlorate decomposition at different aluminium contents. The differences observed in burning behaviour by earlier authors is explained in terms of porosity and thermal conductivity of the composite.

ISSN:0010-2202    

DOI:10.1080/00102208108547514

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

—Activation energy asymptotics is applied to the problem of a premixed flame in which a finite porous solid is used to transfer heat from the burnt gas to the preheat zone. Global heat losses are permitted and the phenomena of blow-off and flashback are identified.

ISSN:0010-2202    

DOI:10.1080/00102208108547515

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor