Velocity burning data, temperature

PHYSICAL VARIABLES. There has not yet been any adequate study of the effects of pressure, so only changes in temperature and in the nature of the turbulent flow can be considered. The small amount of data available shows that turbulent burning velocity changes with temperature in very nearly the same way as laminar burning velocity. For instance, the values of Heiligenstaedt (12) for coke oven gas-air mixtures, over the range 10° to 400° C., can be correlated within 10% by the Reynolds number of the flow when plotted as Ut/Ul Similarly, Delbourg (12) found for town gas-air flames... 

Values of n are available for numerous gases and gas mixtures. Burning velocities have been measured on burner flames, and flame temperatures, Tb, can be computed thermodynamically. It is thus possible to put Equation 5 to a test by comparing experimental values of minimum spark-ignition energies with values calculated from data on quenching distances, burning velocities, heat conductivities, and flame temperatures. 

Effective Over-all Chemical Reaction Orders. Values of the effective over-all reaction order a have been obtained by many investigators. The published data are not comprehensive enough to permit any definite correlations to be made between reaction orders, pressure, temperature, and mixture ratios (26). One or more of the three basic types of flame measurements are used in determining reaction orders, these being flame thickness, burning velocity, and quenching distance. Reaction order data are available in the more recent literature for the following mixtures, obtained by the indicated method for various pressures, temperatures, and mixture ratios. 

The soot temperature was found to exceed the gas temperature as measured by thermocouples in the absence of droplet injection but decayed at a similar rate. This is attributed to bulk heating effects associated with the localized burning of vaporized material. A detailed diffusion flame calculation for a cylindrical source of reactants and relative velocity on the same order as these experimental data, indicate that this bulk heating effect is reasonable. 

An additional attempt for a further improvement of the emission behaviour is a detailed analysis of the combustion process by in-furnace measurements which is also carried out by [6]. In order to get experimental data of gas concentrations, temperatures and velocity fields within the reaction zones of different types of heating appliances the project Development of Newly Designed Wood Burning Systems with Low Emissions and High Efficiency f7I was carried out under the JOULE III program of the European Commission. 

In order Co get reliable data, results of several bum cycles are used to calculate mean values of velocities and turbulence intensities. In addition to the mentioned investigations by LDV, gas concentration measurements of CO2, CO, O3 and hydrocarbons (CHj) are done at the inlet of the burnout zone. Temperature measurements are carried out for the entering combustible gases, the added burnout air and at two wall sections in order to get complete data sets characterising the combustion conditions in the investigated test stove during the different burn phases of wood log combustion. 

The decomposition of ozone has been of great interest to those concerned with combustion, because of the apparent simplicity of the reaction and the fact that there is only one product gas, oxygen. Lewis and von Elbe (13) developed a theory of flame propagation in ozone-oxygen mixtures on the basis of their burning velocity studies. They (13) derived high-temperature specific heat values for oxygen from their explosion data. 

As noted earlier (Section 4.2), burning velocities in oxygen are considerably greater than those in air. Similarly, since the flame temperature increases as the oxygen content of the atmosphere increases, the amount of heat fed back to a liquid pool [Equation (4.51)] also increases. Accordingly, the liquid burning rate increases, but reliable quantitative data are available at present only for fires in air. 

The complete description of a flame requires the specification of the pressure, the mass flow rate or burning velocity, the initial gas composition, and the appropriate transport coefficients and thermodynamic data. The remaining information is contained in a set of one-dimensional profiles of composition, temperature, and gas velocity as a function of distance (Fig. 2). Other independent variables than distance could have been used, e.g., temperature or time, but distance is common in experimental studies. Not all of these profiles are independent since there are a number of relations between the variables such as the equation of state, conservation of mass, etc. As an example, gas velocity can be obtained both by direct measurement and from temperature measurements using geometrical and continuity considerations. In the example given the indirect determinations of velocity are the more reliable and were used in the analysis. It is general practice to measure as many variables as convenient because the redundant profiles provide a check on the reliability of the measurements. 

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