摘要:

The equilibrium compositions of the products of combustion of brown coals from the Rhineland (West Germany) have been calculated over a wide range of temperatures and stoichiometrics. Special attention has been given to the fate of the mineral matter in the coals and, in particular, to species containing the elements Na, K, S and Ca. The results show that the species of importance at equilibrium are very much a function of the initial composition of the coal but that the important species can be categorized broadly as a function of temperature and stoichiometry. For the condensed phases, sulphates predominate at all temperatures under fuel-lean conditions. For fuel-rich conditions carbonates, sulphides, and oxides and hydroxides are of chief importance in the low (<110O K), middle (1000-1200 K) and high (< 100 K) temperature ranges respectively. Silicates and silica are the most persistent condensed species, occurring across a very wide range of temperatures and stoichiometrics. The calculations are consistent with boiler fouling mechanisms that have been proposed to explain observations made with the Rheinisch-Westfälisches Elektrizitätswerk experimental combustion rig.

ISSN:0010-2202    

DOI:10.1080/00102208508960372

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper describes a computational study of the ignition of methane mixtures by selective ignition energy deposition. In this work the ignition energy was added as an initial condition to the combustible mixture in a specific manner, either in the form of heat or a combination of heat and selected, highly reactive atoms or molecules. The resulting induction time for the ignition of homogeneous combustion was found to decrease with increasing fraction of ignition energy deposited into dissociation for the same total ignition energy at a given equivalence ratio. In addition to these calculations performed at constant energy, other calculations were performed where equal amounts of the radicals H, O, and OH were added to assess the effect of direct addition of these radicals on the induction time. Oxygen atoms yielded the shortest induction time in the stoichiometric case and hydrogen atoms yielded the shortest induction time in the lean case. Hydroxyl radicals yielded by far the longest induction time in both cases

ISSN:0010-2202    

DOI:10.1080/00102208508960373

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A comprehensive aerothermochemical model for the process of C/C nozzle recession has been developed. The analysis accounts for both diffusion and chemical kinetics effects on the recession process. The gas-phase conservation equations are Favre-averaged to account for variable density effects. The turbulence modeling consists of a two-equation (K-ϕ) turbulence closure model for the final averaged gas-phase conservation equations. The solid-phase equations consist of the transient heat-conduction equation For the C/C nozzle with a recessing surface. The governing set of equations is solved numerically. Predicted results compared well with Geisler's experiment data. The recession process was found to be limited by the diffusion of oxidizing species such as H2O and CO2to the nozzle surface. Chemical kinetics limited the recession rate only in the initial period when the nozzle surface temperatures were low. The recession rate was found to increase with increasing concentration of oxidizing species in the propellant exhaust, increasing chamber pressure, or increasing surface roughness.

ISSN:0010-2202    

DOI:10.1080/00102208508960374

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The comparison of soot limits of axisymmetrical laminar diffusion flames stabilized in two different flow fields, i.e., stretching and non-stretching (parallel) flow, revealed that soot emission is suppressed more effectively in the former flow. From the experimental results that flame heights were hardly affected by the flow field difference, it was inferred that such an effect of the stretching flow is attributed to the flow acceleration which leads to the shortening of fuel residence time in the soot-forming region and, therefore, to the effective suppression of soot particle growth

ISSN:0010-2202    

DOI:10.1080/00102208508960375

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

We present a limiting system of equations to describe combustion processes at low Mach number in either confined or unbounded regions and numerically solve these equations for the case of a flame propagating in a closed vessel. This system allows for large heat release, substantial temperature and density variations, and substantial interaction with the hydrodynamic flow field, including the effects of turbulence. This limiting system is much simpler than the complete system of equations of compressible reacting gas flow since the detailed effects of acoustic waves have been removed. Using a combination of random vortex techniques and flame propagation algorithms specially designed for turbulent combustion, we describe a numerical method to solve these zero Mach number equations. We use this method to analyze the competing effects of viscosity, exothermicity, boundary conditions and pressure on the rate of combustion for a flame propagating in a swirling flow inside a square.

ISSN:0010-2202    

DOI:10.1080/00102208508960376

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Soot production in premixed flames of multicomponent fuels is modeled by combining (1) the experimental observation that for pure fuels the soot volume fraction varies exponentially with equivalence ratio, and (2) the assumption that soot production by each fuel component if independent of the presence of the other components, except in the sharing of the available oxidizer. Soot thresholds calculated from this model are in excellent agreement with available experimental data.

ISSN:0010-2202    

DOI:10.1080/00102208508960377

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A probe containing both an ionization sensor and a luminosity sensor was installed in place of a glow plug in both an Oldsmobile and a Volkswagen diesel engine in order to evaluate these two devices as “start-of-ignition” markers. Information on ignition delay relative to injection timing might well be the key item in fuel scheduling to effect maximum fuel efficiency and reduced exhaust emissions. The results indicated that at low engine RPM both sensors responded simultaneously, but at high RPM, independent of load, there was a noticeable and repeatable delay of the ionization gage signal. Also, the ionization sensor signal showed larger cycle-to-cycle variations in both shape and peak amplitude than the luminosity sensor making application of that signal to produce a reliable marker more difficult. The luminosity sensor showed consistent behavior under all test conditions.

ISSN:0010-2202    

DOI:10.1080/00102208508960378

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

In a demonstration experiment, the vapor and liquid disiributions in a hollow-cone spray have been separately photographed using laser-excited fluoresent dopants which form organic exciplexes. In color photographs, the Fluorescence from the liquid appears blue-green and the fluorescence from the vapor appears purple. With high-speed black and while film, “stopped action” pictures of the liquid and/or vapor portions of the spray were obtained. This technique may lead to the development of real-lime visualization diagnostics For evaporating fuel sprays.

ISSN:0010-2202    

DOI:10.1080/00102208508960379

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Flame spread rates over pooled methanol and pooled gasoline were compared with flame spread rates over a porous surface saturated with these fuels. If the surface temperature was above the fuel flashpoint, the flame spread rate over a fuel-soaked porous surface was the same as for pooled fuel. Just below the flashpoint, flame spread was slower over a porous surface, since liquid flow was restricted. Far below the flashpoint, the flame spread over the porous surface more rapidly than over pooled fuel. For highly volatile fuels, such as methanol-5 percent isopentane mixture, the rate of flame spread depended on lime available for development of a flammable vapor layer over the liquid.

ISSN:0010-2202    

DOI:10.1080/00102208508960380

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor