摘要:

The effect of small additions of oxygen to the fuel on formation of soot in methane-air diffusion flames was studied over a range of flow rates and of burner diameters. The flames studied were shorter than those of previous studies, purely blue or blue and yellow without soot escape. Heights of various distinctive features were measured, and composition and temperature profiles were obtained; the distinctive features include.onset and termination of visible emission of radiation and deposition of material on a quartz filament inserted into the flame. The results indicate negligible influences of oxygen addition and thereby suggest that ions from the primary mechanism CH+Orarr;CHO++e-are unimportant in soot formation in these flames. A simplified one-step kinetic model accounting for buoyancy and momentum was developed and employed to obtain estimates of overall rate parameters for flame attributes related to soot formation.

ISSN:0010-2202    

DOI:10.1080/00102208608923869

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A one-dimensional burning wave in a monopropellant particle bed is studied. Approximate analytical solutions are obtained assuming low Mach number flow, rapid burning and efficient heat transfer between the particles and the gas. A preheat zone, where compression heats the gas, precedes the burning zone. A conducting layer occurs in the vicinity of the leading edge of the burning zone. In the remainder of the burning zone, the temperature remains constant and the particles burn up.

ISSN:0010-2202    

DOI:10.1080/00102208608923870

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Abstract-The wall temperature at which a premixed methanol/air mixture ignited was determined as a certain measure of ignition delay in a quartz tube around 1000 K as a function of equivalence ratio under several different flow velocities. The kinetic model of methanol combustion proposed by Westbrook and Dryer (1979) was successfully applied for analysing the ignition process. When a small amount of NO2was added, the temperature decreased appreciably; this was analysed in terms of the above combustion model combined with a series of reactions initiated by the hydrogen atom abstraction from methanol by NO2: CH3OH + NO2→CH2OH + HNO2. The corresponding rate constant was determined as 1011.3±0.3exp[-22.6(kcaI.mol-1)/RT] cm3 mol-1s-1in the temperature range of 900-1100 K.

ISSN:0010-2202    

DOI:10.1080/00102208608923871

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Abstract-An aerothermochemical model for graphite nozzle recession and heat-transfer processes in solid-propellant rocket motors has been developed. The model considers the turbulent boundary-layer flow in the nozzle, heterogeneous reactions at the nozzle surface, and transient heat-conduction processes in the nozzle material. Mass transfer across the highly-accelerated turbulent boundary layer shows only a weak dependence on the Schmidt number of the diffusing species. Both frozen and chemical equilibrium boundary-layer assumptions were considered. H2O is found to be the dominant oxidizing species, with CO2being of secondary importance. Concentration profiles of H2O across the boundary layer are not significantly affected by gas-phase reactions, implying that the graphite recession process is relatively independent of gas-phase reactions. The model has been verified with experimental data. Good agreement has been obtained for both recession and temperature measurements.

ISSN:0010-2202    

DOI:10.1080/00102208608923872

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Abstract-The effects of engine deposit layers on the product gas emissions from combustion bombs manufactured from engine combustion chambers were studied for various fuel-deposit systems. Nine fuels (methane, ethane, propane, n-butane, n-pentane, n-hexane, benzene, n-heptane and iso-octane) were tested in combination with two in-situ engine deposit layers-one thin (0.0017 cm) and one thick (∼0.05-0.1 cm). Gas samples from the reactors were analyzed by gas chromatography. For the thin deposit, the results show that the principal exhaust effluent is unburnt fuel. Additionally, as the solubility of the fuel is increased, the HC emission increases in direct proportion to the change in relative solubility and the absolute HC level can be estimated from the deposit composition and estimated fuel solubility. For the thick deposit, the results show that the principal exhaust effluent is also unburnt fuel, that the exhaust HC level increases with fuel solubility and that a small fraction of the HC emission may arise from the porous structure of the deposit. Additionally, however, they show that the exhaust HC emission decreases as the loading and sampling times of the reactor are reduced and is proportional to the square root of the loading time, suggesting that time-dependent loading processes will be important at the proportionally shorter time scales of engines even at the elevated temperature found in typical engine combustion chambers.

ISSN:0010-2202    

DOI:10.1080/00102208608923873

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The mole fractions of the C1-C3hydrocarbons, CO, Co2, N2, and O2in laminar methane-air flames at one atmosphere pressure have been measured. The experiments wereperformed on a flat-flame burner as a function of fuel-air equivalence ratio, flame temperature, co-added ethylene or ethane fuel, and flame inhibitor. CFaBr. Samples were obtained as a function of height above the burner surface using an uncooled quartz probe and were analyzed by gas chromatography. Measurements of the perturbation of the species mole fractions caused by the probe sampling technique were performed. Concentration-distance profiles have been obtained for five fuel-rich ((l)= 1.47-1.51) and one lcan ((l)=0.75) Rame. Product peak concentrations are compared with those from computer-modeled adiabatic flames, indicating the usefulness of the species profile data in testing kinetic mechanisms of methane combustion.

ISSN:0010-2202    

DOI:10.1080/00102208608923874

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor