摘要:

A model for predicting flame ignition and blowout in a combustor primary zone is presented. The model employs a Monte Carlo calculation procedure to follow a chemical reaction through a mixing process to account for composition nonuniformities in the primary zone. The fuel oxidation process is described by an overall kinetic rate equation. The model is used to predict the lean ignition and blowout limits of premixed turbulent flames; the effect of composition nonuniformity on the lean ignition limit is explored using an assumed distribution of fuel fraction. The predicted trends are verified using data from the literature and by experimental work on an atmospheric pressure, constant cross-sectional area tubular combustor. Data on the effects of variations in inlet temperature, reference velocity and mixture uniformity on the lean ignition and blowout limits of gaseous propane-air flames are presented. The variations of the predicted lean limits with mixture temperature, pressure and velocity compare favorably with experimental magnitudes and trends. With increased mixture nonuniformity, the model predictions and the data show a substantial reduction in the lean ignition limit.

ISSN:0010-2202    

DOI:10.1080/00102208008952435

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Further experiments on cyclic, unsteady, transonic flow with heat addition are described. The heat addition is produced by condensation by homogeneous nucleation of water vapor or ethanol in the throat region of a Laval nozzle. Different carrier gases are used and frequencies of pressure fluctuations up to 22 kHz are found. Terms in a dimensional analysis that had previously not been investigated were studied. The new terms included different Damkohler parameters and the ratio of the specific heats. Under certain conditions condensation at M<I was observed. A qualitative description of the process and estimates of the frequency yielded satisfactory results.

ISSN:0010-2202    

DOI:10.1080/00102208008952436

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

It is shown that similarity solutions in strong buoyant plumes (plane or axisymmctric) exist if a local characteristic turbulent diffusion coefficient varies inversely proportional to the square of the local gas density in the plume. The similarity formulation implies that the proper dependent variable for the temperature (density) defect is ΔT/0(Δρ/ρ), where ΔT( Δρ) is the temperature (density) defect from the ambient temperature (density), T0(ρ0), and ρ is the local density in the plume. The same variable is applicable further downstream from the source when the plume becomes weak. The form of the variable, ΔT/T0, proposed for both strong and weak plumes is different from the form of the variable, ΔT/T( Δρ/ρ0), previously used for weak plumes. Long experience with strong plumes from fires and recent experimental results of temperature variations along the plume axis support the use of the variable ΔT/T0. The similarity solution is consistent with Morton's (1965) model of strong plumes and the form of the entrainment function for strong density variations in plumes or jets proposed by Ricou and Spalding (1961). In a subsequent paper, a simple model will be presented, based on the similarity solutions, to predict flame heights and the location of the virtual source in turbulent diffusion flames (momentum or buoyancy controlled). The model is similar to Steward's (1970), developed for buoyancy controlled flames.

ISSN:0010-2202    

DOI:10.1080/00102208008952437

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The combustion of char particles including the effects of external mass transfer, surface reaction, pore diffusion, and pore growth is analyzed theoretically. A random pore model is used to relate pore surface area, pore volume and effective diffusivity to the local burnoff. The equations for oxygen concentration and burnoff as functions of time and position are solved analytically for the limiting case of strong diffusional limitations (high temperature or particle size) and numerically for the general case. The results include the variation of particle size and density with burnoff under conditions pertinent to pulverized and fluidized combustion. The analysis is compared with previous analyses from the literature.

ISSN:0010-2202    

DOI:10.1080/00102208008952438

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208008952439

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A laser spectrophone operated at 514.5 nm has been shown to accurately monitor the “graphitic” carbon component of the airborne particulate emitted in the exhaust from a 2.3 liter Opel diesel vehicle. The mass-specific absorption coefficient of the graphitic-like material is 8.9±0.5 m2/g at 514.5 nm, in excellent agreement with values for similar material from other combustion sources. Since the laser spectrophone can apparently be used to quantitatively measure light absorption by airborne “graphitic” particulate material, it may also be generally useful as a monitor of “graphitic” particulate mass loading, regardless of combustion source.

ISSN:0010-2202    

DOI:10.1080/00102208008952440

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

It becomes more difficult and expensive to design and test new combustors for large jet engines which require increasing mass flow rates and temperature and pressure levels. Therefore, it is important to study the scaling laws of combustor performance and to provide the modeling rules for practical use for the development and application of engines. This paper deals with the modeling theory of combustion chambers. Based on similarity principles and some typical combustion mechanisms, different rules for combustor modeling, are systematically suggested, particularly for the modeling of gas turbine combustors. These rules may be applied to the design and testing of combustion systems. Moreover as the theory has extensively correlated with the operating parameters of the combustor, it may also be used to predict the combustor performance.

ISSN:0010-2202    

DOI:10.1080/00102208008952441

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Carbon monoxide and temperature have been measured in the post-flame region of laminar, pre-mixed methane/air flat flames at atmospheric pressure using both laser absorption spectroscopy and conventional probe techniques. The laser absorption measurements employed a tunable diode laser to record fully resolved absorption lines in the fundamental band of CO near 4.7 microns. Probe measurements were made with thermocouples and sampling microprobes (uncooled quartz and water-cooled stainless steel). The extracted gases were analyzed for CO and CO2using NDIR instruments. The laser absorption measurements of CO in rich flames were in good agreement with chemical equilibrium calculations based on metered fuel and air flow-rates and measured local temperature. In lean flames, measured levels of CO exceeded equilibrium values, as expected, due to incomplete reaction of CO to CO2near the flame front. Temperatures inferred from the relative absorption in lines from different vibrational levels were in good agreement with thermocouple measurements. The sampling measurements in all flames yielded total carbon consistent with input stoichiometry, but indicated some conversion of CO to CO2in both probes, with the extent of conversion depending on pressure in the probe.

ISSN:0010-2202    

DOI:10.1080/00102208008952442

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A brief summary of the previous experimental studies on the ignition of methane in shock tubes is given by way of introduction. The ignition delay characteristics of methane-oxygen mixtures highly diluted with argon were studied behind reflected shock waves. Ignition was identified by pressure rise and visible light emissions using piezoelectric transducers and photomultiplier detection respectively. The measurements covered a temperature range of 1600-2100 K and a pressure range of 1 to 6 atm. The equivalence ratio was varied from 0.2 to 5.0. The following expression

ISSN:0010-2202    

DOI:10.1080/00102208008952443

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor