A comprehensive review of measurements and data analysis of laminar burning velocities for various fuel+air mixtures

The laminar burning velocity is a fundamental property of combustible mixtures important for kinetic model validation as well as for practical applications. Many efforts are directed towards its accurate determination. The heat flux method is one of the commonly recognized methods for measuring laminar burning velocity, however, the information on the accuracy of the method is scattered in the literature. In the present work, an attempt was made to summarize and extend the available information on the different factors contributing to the experimental uncertainty of the heat flux method. Experimental setup of the Lund University group, typical for the heat flux community, and the procedures used to determine the burning velocity are described. Furthermore, the influence of different uncertainty factors, originating from each part of the setup, is analyzed. Asymmetric heat fluxes and the method for determining flame surface area were found to give an important contribution to the total error. As a ...

Experimental Uncertainties of the Heat Flux Method for Measuring Burning Velocities

Yet another kinetic mechanism for hydrogen combustion

Simulation of entrained flow gasification with advanced coal conversion submodels. Part 1: Pyrolysis

Cellular ceramics produced by rapid prototyping and replication

The lean premixed combustion of hydrogen and carbon monoxide (H2/CO) mixtures within a porous inert media model-burner was investigated for ranges of H2/CO volumetric ratios from 2 to 4, inert volumetric concentrations in the fuel stream from 85% to 90%, thermal loads of 400 kW/m2 (2 kW) and 1000 kW/m2 (5 kW), constant reactants temperature of 673 K and an equivalence ratio of ϕ = 05 Experimental measurements and numerical predictions of temperature profiles and temperature gradients along the axial center-line of the combustion zone are presented and the thermal flame thickness is estimated and analyzed for the effect of thermal load, inert components in the fuel stream and H2/CO ratios The adopted numerical model uses a volume-averaged approach and solves both the gas- and solid-phase energy balances explicitly and accounts for the radiative heat transport in the solid-phase The thermal flame thickness results are compared with the respective laminar free flame values and differences between the flame thickness of free flames and flames inside a porous inert media are discussed

Investigation on the thermal flame thickness for lean premixed combustion of low calorific H2/CO mixtures within porous inert media

Laminar burning velocity measurements using the Heat Flux method and numerical predictions of iso-octane/ethanol blends for different preheat temperatures

The increasing need for more efficient and less emissive technologies has shifted the focus of combustion research towards technologies involving combustion in porous inert media. Although burners of this type have started to be examined and characterized over the past years, nonintrusive experimental methods are needed to describe the actual processes taking place inside the porous structure. In the present work, the technique of laser induced fluorescence (LIF) is employed to visualize the flame stabilization process inside porous media combustion, utilizing the excitation and subsequent detection of the hydroxyl radical (OH). In order to perform planar measurements inside the porous combustion zone, optical access along the porous structure had to be accomplished. Optical access along the porous structure allowed the laser beam to reach the probe volume and to detect sufficient fluorescence amount. This was realized by creating a thin gap of similar width as the porous cavities. The optical gap size and positioning were chosen so as to yield the most suitable configuration for a sufficient signal to noise ratio without significant disturbance of the combustion process in the porous reaction zone. The experiments were conducted for various thermal loads and excess air ratios for methane/air combustion. The main scope of this work is to demonstrate how the flame structure is influenced by the thermal load and the equivalence ratio over a wide operational range. The flame stabilization in the porous inert medium at fixed position, which is almost independent of the flow rate in some cases, is also observed. Moreover, an experimental characterization of the wide, stable operating conditions of the porous burner is given, along with the description of the flame zone inside the porous matrix.

Analysis of the flame structure for lean methane–air combustion in porous inert media by resolving the hydroxyl radical

An experimental and numerical investigation of a laminar confined and inverse diffusion flame (IDF) with pure oxygen as oxidizer considering global stoichiometry of partial oxidation processes is presented. The present burner setup allows studying the structure of the high temperature oxidation zone and the subsequent reforming region in a simplified geometry considering typical operating conditions as found in large scale gasifiers for the production of synthesis gas out of different hydrocarbon feedstocks. The use of pure O2 as oxidizer leads to extremely high temperatures and higher concentrations of radiating species, i.e. H2O and CO2, compared to a partial oxidation process with air as oxidizer. Hence the flame structure is strongly influenced by radiation and diffusion effects. The scope of this paper is to determine how the Soret effect and the radiative heat transfer at high temperatures in combination with low strain rates in the downstream region influences the flame structure. In this respect the radiation model and potential self-absorption of radiating species become of major importance for the numerical predictions. In the experimental part the flame structure was studied with a planar OH-laser-induced fluorescence (LIF) setup, while the temperature was determined by a two-line LIF approach using the rotational temperature of the OH radical. The correlation between OH concentration and temperature was used as an indicator for comparison purposes. In the numerical part two-dimensional laminar CFD calculations with detailed chemistry and transport were performed and the numerical results show the importance of the Soret effect. The optically thin radiation model yields good agreement with the experiments at high strain rates close to the nozzle, but the radiation model underpredicts the temperature further downstream at low strain rates with potentially significant self-absorption of the radiating species.

S. Voss

Papers

Investigation on the thermal flame thickness for lean premixed combustion of low calorific H2/CO mixtures within porous inert media

Laminar burning velocity measurements using the Heat Flux method and numerical predictions of iso-octane/ethanol blends for different preheat temperatures

Analysis of the flame structure for lean methane–air combustion in porous inert media by resolving the hydroxyl radical

Experimental and numerical study of rich inverse diffusion flame structure

Determination of laminar burning velocities for lean low calorific H2/N2 and H2/CO/N2 gas mixtures