Burned gases

The main combustion pollutants are nitrogen oxides, sulfur oxides, carbon monoxide, unbumed hydrocarbons, and soot. Combustion pollutants can be reduced by three main methods depending on the location of thek appHcation before, after, or during the combustion. Techniques employed before and after combustion deal with the fuel or the burned gases. A thkd alternative is to modify the combustion process in order to minimise the emissions. 

Reactions and Combustion Dynamics of Fast-Burning Gases... 

A deflagration is a slow burning exothermic reaction similar to the combustion explosion, but which propagates from the burning gases into the unreacted material at a velocity that is less than the speed of sound in the unreacted material. Most (not all) explosions are deflagrations. 

The results show that at 2 torr, ku = 2.5 X 10 8 and at 760 torr ku = 1.0 X 10 8 cm.3 molecule-1 sec.-1 This is reasonably good agreement in view of the possible errors. Furthermore, the values of ku obtained are consistent with earlier estimates based on comparisons with similar reactions (10, 19). Our purpose in presenting it here is to illustrate the potential use of flames in estimating more accurate rate constants for reactions like Reaction 14. Of course, the influence of diffusion must always be accounted for in such estimations diffusion is particularly important at low pressures and for small ion concentrations. (It is often advantageous to work at low pressures because the spatial resolution is much better than at 1 atm. At low pressures most measurements are made in or close to the reaction zone itself. At high pressures, where the reaction zone is thinner, measurements are made both in the reaction zone and in the burned gases.)... 

More recently, experimental studies have been carried out using a similar device but with an annular external hot coflow of burned gases that allowed one to operate within a much larger velocity range. Chen et al. [26] and more recently Chen and Bilger [27,28] have studied the perturbations that the smallest scales of turbulence can impose to the local flamelet structures. Those studies are of paramount importance, first because they have allowed to get deeper insights into the local structure... 

Turbulent flame-front regime. Eddy-like contortions of fhe flame preheaf and burned gases zones give rise to "ouf of fronf" islands and peninsula sfructures of intermediate progress variable values. Scalar transport becomes gradient-like. 

The by-product process involves essentially by-product coke ovens which can be the waste heat ovens or regeneration ovens. They are designed to produce coke as well as to recover the products of carbonisation. The ovens are narrow rectangular refractory chamber. The ovens are heated from both sides through vertical flues. The necessary heat is produced by burning gases inside the narrow flue chambers. The ovens are the coking chambers and... 

Equation (4.4), which connects the known variables, unbumed gas pressure, temperature, and density, is not an independent equation. In the coordinate system chosen, //, is (lie velocity fed into the wave and u2 is the velocity coming out of the wave. In the laboratory coordinate system, the velocity ahead of the wave is zero, the wave velocity is uh and (u — u2) is the velocity of the burned gases with respect to the tube. The unknowns in the system are U, u2, P2, T2, and p2. The chemical energy release is q, and the stagnation adiabatic combustion temperature is T, for n-> = 0. The symbols follow the normal convention. 

Burned gases Luminous zone Dark zone... 

Hint Assume that the pressure in the burned gases is essentially 1 atm. In calculating the pressure in the cold gases make sure the value is correct to many decimal places. 

There is also interest in the velocity of the burned gases with respect to the tube, since as the wave proceeds into the medium at rest, it is not known whether the burned gases proceed in the direction of the wave (i.e., follow the wave) or proceed away from the wave. From Fig. 5.1 it is apparent that this velocity, which is also called the particle velocity (An), is... 

Before proceeding further, it must be established which values of the velocity of the burned gases are valid. Thus, it is now best to make a plot of the Hugoniot equation for an arbitrary q. The Hugoniot equation is essentially a plot of all the possible values of (l/p2, P2) for a given value of (Hp, Pi) and a given q. This point (IIPi, P ), called A, is also plotted on the graph. 

Thus, the important result is obtained that at J the velocity of the burned gases (u2) is equal to the speed of sound in the burned gases. Furthermore, an identical analysis would show, as well, that... 

Determination of the Speed of Sound in the Burned Gases for Conditions above the C-J Point... 

Since one can usually make an excellent guess of 72, one obtains // immediately and, thus, P2. Furthermore, /t does not vary significantly for most detonation mixtures, particularly when the oxidizer is air. It is a number close to 1.8, which means, as Eq. (5.21a) specifies, that the detonation velocity is 1.8 times the sound speed in the burned gases. 

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