摘要:

Emission and extinction measurements in the visible and U.V. were performed along the axis of vertical unconfined fuel oil flames produced on a variable swirl burner. The flow rate of the fuel was around 6 Kg/hr and the theoretical equivalence ratios was varied from 0.9 to 1.15. The emissions due to the radicals OH, CH and C2were compared with the continuum emission due to the soot particles. The profiles of the brightness and colour temperature were obtained from the measurements of the absolute intensity of the continuum in the spectral range 4000÷8000A. The colour temperature was much higher than the brightness temperature near the burner nozzle while the difference decreased in the final part of the flames. In the first part of the flame the monochromatic extinction coefficient at λ = 6500Å decreases, due to fuel droplets, which are evaporating, but increases downstream where the soot formation process prevails. The study of its spectral variation in the range 4000Å-8000Å allows the determination of the dispersion exponent n (defined by the expression K = K0λ-n) in the different regions of the flames. It was almost equal to zero near the burner nozzle, where the droplets prevail, equal to 1.5 in the final part of the flames and had a more complex behaviour in the intermediate regions. The monochromatic emissivity and true temperature profiles were also obtained from the above data and are discussed, in comparison with the measured extinction, and with reference to the flame structure, droplets evaporation and soot formation processes.

ISSN:0010-2202    

DOI:10.1080/00102208008952369

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The ignitability of a fuel droplet in a reactive oxygen/fuel-vapor/inert environment simulating the spray interior is studied using large activation energy asymptotics. The cold boundary difficulty is removed by recognizing that ignition occurs at a finite radial distance which can be physically prescribed. A set of universal ignition Damköhler number curves have been numerically generated and subsequently fitted to yield an explicit ignition criterion suitable for incorporation into spray modeling.

ISSN:0010-2202    

DOI:10.1080/00102208008952370

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A divided-chamber, stratified-charge engine was operated at different speeds and loads, and with two prechamber nozzle sizes. Pressure was recorded and flame propagation was filmed through a transparent head. For each condition, several sets of data were taken and the experimental scatter identified. Pressure and flame propagation were then computed with a two-dimensional model and compared with the measured ones. Several quantities which influence the computed results were not directly measured in the experiment and assumptions had to be made about them in the model. They include amount and state of cylinder air and residual products, turbulence, and wall heat transfer. A turbulent diffusivity, an overall reaction rate, and a wall heat loss proportional to the heat released thus were adopted in the model. The same set of model constants was used for all cases and, through successive iterations, adequate agreement of computed and measured results was obtained. For this specific engine design and set of operating conditions, it was found necessary to account for the turbulence generated by the prechamber jet in order to reproduce main chamber combustion properly. In spite of uncertainties about both the measured quantities and the model, this first detailed comparison of engine combustion data also shows again that the model can be used to interpret and extrapolate engine data. Such capabilities are useful in the stages of development and optimization of engines.

ISSN:0010-2202    

DOI:10.1080/00102208008952371

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Measurements of the fluctuating temperature in a heated round turbulent free jet have been performed with the aid of a fine wire thermocouple compensated for the effects of thermal inertia. The use of particularly fine thermocouple wires (12.7 μm in diameter) and of digital signal processing represent special features of the experiment. Data are reported for the mean, rms, probability density function, spatial correlation, energy spectrum and, with some reservation, dissipation of the fluctuating temperature. Where possible these are compared with the data of other workers.

ISSN:0010-2202    

DOI:10.1080/00102208008952372

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The gas velocity profiles in front of the leading edges of flames propagating across methanol at initial temperatures Ti from -5°C to 35°C were measured by using high-speed schlieren photography combined with a hot gas tracer technique. For Tlmuch lower than the flash point Tlf, any appreciable gas movement could not be observed in front of the leading flame edge. Therefore, as considered in previous studies, preheating in this case was supposed to be mainly caused by convection in the liquid phase. For Tlslightly lower than Tlf, the maximum value of the extrapolated gas velocity across the flame front was found to be a fairly high value. This result could be consistently intepreted by considering the increase of the methanol vapor concentration in front of the leading flame edge due to preheating. For Tlabove Tlf, the experimentally predicted aspects of the gas movements near the leading flame edges were found to coincide with the theoretically predicted aspects for the flame propagation through layered mixtures.

ISSN:0010-2202    

DOI:10.1080/00102208008952373

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0010-2202    

DOI:10.1080/00102208008952374

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor