Species temperatures

Transfer species Temperature, °C Chain-transter constant x Reference... 

Because many practical flames are turbulent (spark ignited engine flames, nil field flares), an understanding of the interaction between the complex fluid dynamics of turbulence and the combustion processes is necessary to develop predictive computer models. Once these predictive models are developed, they arc repeatedly compared with measurements of species, temperatures, and flow in actual flames for iterative refinement. If the model is deficient, it is changed and again compared with experiment. The process is repeated until a satisfactory predictive model is obtained. 

In turbulent reactive flows, the chemical species and temperature fluctuate in time and space. As a result, any variable can be decomposed in its mean and fluctuation. In Reynolds-averaged Navier-Stokes (RANS) simulations, only the means of the variables are computed. Therefore, a method to obtain a turbulent database (containing the means of species, temperature, etc.) from the laminar data is needed. In this work, the mean variables are calculated by PDF-averaging their laminar values with an assumed shape PDF function. For details the reader is referred to Refs. [16, 17]. In the combustion model, transport equations for the mean and variances of the mixture fraction and the progress variable and the mean mass fraction of NO are solved. More details about this turbulent implementation of the flamelet combustion model can also be found in Ref. [20],... 

Figures 4.6—4.8 are the results for the stoichiometric propane-air flame. Figure 4.6 reports the variance of the major species, temperature, and heat release Figure 4.7 reports the major stable propane fragment distribution due to the proceeding reactions and Figure 4.8 shows the radical and formaldehyde distributions—all as a function of a spatial distance through the flame wave. As stated, the total wave thickness is chosen from the point at which one of the reactant mole fractions begins to decay to the point at which the heat release rate begins to taper off sharply. Since the point of initial reactant decay corresponds closely to the initial perceptive rise in temperature, the initial thermoneutral period is quite short. The heat release rate curve would ordinarily drop to zero sharply except that the recombination of the radicals in the burned gas zone contribute some energy. The choice of the position that separates the preheat zone and the reaction zone has been made to account for the slight exothermicity of the fuel attack reactions by radicals which have diffused into...

Tunable diode-laser sensors offer considerable promise for combustion research and development and also for process sensing and control applications. These devices are rugged and relatively easy to operate and they have been demonstrated to yield simple and quantitative measurements of species, temperature, and velocity, where line-of-sight measurements are useful or preferred. These techniques will grow in use as costs of laser sources and fiber-optic components decrease and access to more wavelength regions improves. 

The discharge of warm wastewaters into a surface receiver may have many adverse effects on aquatic life. The increase in temperature results in a decrease in the oxygen concentration in water and the elimination of the most sensitive species. Temperature changes may also cause changes in the reproductive periods of fishes, growth of parasites and diseases, or even thermal shock to the animals found in the thermal plume. 

Species, Temperature, and Current Distribution Mapping in Polymer Electrolyte Membrane Fuel Cells... 

Chapters 4-6 address specific diagnostic methods in PEFCs. Martin et al. provide a detailed review of methods for distributed diagnostics of species, temperature, and current in PEFCs in Chapter 4. In Chapter 5, Hussey and Jacobson describe the operational principles of neutron radiography for in-situ visualization of liquid water distribution, and also outline issues related to temporal and spatial resolution. Tsushima and Hirai describe both magnetic resonance imaging (MRI) technique for visualization of water in PEFCs and tunable diode laser absorption spectroscopy (TDLAS) for measurement of water vapor concentration in Chapter 6. 

For the 1-D gas channel model, the specie, temperature, and velocity distributions inside the gas channels are assumed to be varying only in the direction of gas flow. The control volume employed, shown in Figure 5.5, encompasses the whole... 

Figure 4.24 Successive photoemission electron micrographs of the propagation of moving spiral chemical waves during reaction CO + 1/2 O2 —> CO2 on the surface of monocrystal Pt(llO). The dark and light zones correspond to different coverage of the Pt surface with the adsorbed species. Temperature is 398 K, oxygen pressure is 4-10 Pa, and CO pressure is 1.8 10 Pa [9].

FORTRAN computer program that predicts the species, temperature, and velocity profiles in two-dimensional (planar or axisymmetric) channels. The model uses the boundary layer approximations for the fluid flow equations, coupled to gas-phase and surface species continuity equations. The program runs in conjunction with CHEMKIN preprocessors (CHEMKIN, SURFACE CHEMKIN, and TRAN-FIT) for the gas-phase and surface chemical reaction mechanisms and transport properties. The finite difference representation of the defining equations forms a set of differential algebraic equations which are solved using the computer program DASSL (dassal.f, L. R. Petzold, Sandia National Laboratories Report, SAND 82-8637, 1982). 

The polymer deposition (polymerization) is significantly accelerated by the addition of cool inert gas into the deposition chamber. This phenomenon indicates the significance of the reactive species temperature, (in the context similar to that of the electron temperature, Tg). Unless can be cooled down (below Tc), which usually occurs as a consequence of collisions with walls, the polymerization cannot proceed. In other words, the dissipation of the excess energy in some forms is necessary for the deposition growth polymerization to occur. 

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