Flame equilibrium

Mass spectrometric studies were made by Farber and Srivastava (6) on the reactions involved with vanadium and chromium additives in potassium-seeded H /Og flames. Equilibrium values at an average flame temperature of 2250 K for the reaction CrOg(g) + HgO(g) = H2CrO (g) were analyzed by Farber and Srivastava (6). They calculated AjH (298.15 K) = -64.6 7 kcal mol for CrOg(g). The experimental determination of AjH (298.15 K) for H2CrO (g) also required the A H (298.15 K) value for CrO(g). Adjusting the calculations of Farber and Srivastava (6) to be consistent with the JANAF AjH (298.15 K) value for CrO(g) (2), we recalculate A H (289.15 K) = -72.6 kcal mol for CrOg(g). 

D. E. Jensen, Production of electrons from alkaline earths in flames equilibrium and kinetic considerations. Combust. Flame 12, 261-268 (1968). 

An approximate equilibrium is set up in the plasma, with the electrons, ions, and atoms having velocity distributions similar to those of a gas that has been heated to temperatures of 7,000 to 10,000°C. Since the plasma is ignited toward the end of the concentric tubes from which argon gas is issuing, the plasma appears as a pale-blue-to-lilac flame coming out of the end of the tube, which is why the system is referred to as a torch, as in a welding torch. 

Useful formulas for BLEVE fireballs (CeSP, 1989) are given by equations 9.1-27 thru 9.1-30, where M = initial mass of flammable liquid (kg). The initial diameter describes the short duration initial ground level hemispherical flaming-volume before buoyancy lifts it to an equilibrium height. 

To predict die capability of a flame arrester to cool hot combnstion gases, the U.S. Bnrean of Mines has developed an equilibrium model and one- and diree-dimensional transient diermal models of a flame arrester, which are nsed to predict die heat losses from die arrester and the maximum temperatures developed (Edwards 1991). 

Several techniques are available in the literature for evaluation of the flame temperature, exit temperature, equilibrium composition of combustion products, and performance parameters of energetic composites [11-13]. The optimum combination of the composite ingredients is determined by thermodynamic means, so as to arrive at a composition having maximum performance... 

Though a system at equilibrium is constant in properties, constancy is not the only requirement. Consider a laboratory burner flame. There is a well-defined structure to the flame—an inner cone surrounded by a luminous region whose appearance does not change. A temperature measurement made at a particular place in the flame shows that the temperature at that spot is constant. At another place in the flame the temperature might be different but, again, it would be constant, not changing with time. A measurement of the gas flow rate shows a constant movement of gas into the flame. Yet a laboratory burner flame is not at equilibrium be-... 

If two or more systems are connected together (such as a pipe length with an orifice plate, two or more vessels connected with pipe or duct, or a compartmented vessel) and an explosion develops in No. 1 area, which generally may be at equilibrium pressure with compartments No. 2 and 3 in equilibrium with No. 2, it can cause a pressure rise in front of the flame front in the unburnt gases in the interconnecting spaces (pipe, compartment). The increased pressure in compartment or area No. 1 becomes the starting pressure for an explosion in com-... 

Table I. Typical Flame Temperatures and Equilibrium Compositions0...

Decay of Secondary Ion Concentrations. The fate of the secondary ions must now be considered. Miller (28) has observed that for C2H4/02 and C2H2/02 flames at 2 and 4 torr the rates of decay of all secondary ions, including C3H3+, are approximately the same (see, for example, Figure 1). The slow decay of the primary ion CHO+, paralleling that of H30 +, has been attributed (11) to establishment of equilibrium for Reaction 14. 

Sugden and Schofield (33) suggest that this reaction (with a rate constant 40-8 cm.3 molecule-1 sec.-1) can account for the boost in ionization of sodium observed when strontium salts are supplied to flames containing sodium. There is evidence (24, 33, 36) which strongly suggests that equilibrium ionization of strontium in flames is rapidly established via... 

The development of models for HCSI combustion has been governed by the similarity of flame growth in HCSI engines and premixed turbulent flames. Thin laser-sheets of only 300 pm thickness were used to measure high-resolution cross sections of the temperature and OH radical distribution in flames of a propane-fueled engine. Figure 8.2.3 illustrates the structure where temperature and OH concentration are closely coupled with super equilibrium values for the OH radical close to the flame front [11]. 

GC, utilizing flame ionization detection (FID), has been used to measure diisopropyl methylphosphonate in meat, grain, or milk (Caton et al. 1994). Sample preparation steps include homogenization, filtration, dialysis, and extraction on a solid sorbent. Two common solid phase extractants, Tenax GC and octadecylsilane bonded silica gel (C18 Silica), were compared by Caton et al. (1994). They reported 70% recovery when using Tenax GC and 85% recovery when using C18 Silica. Sensitivity was not reported. Equilibrium experiments indicate that 8-10 mg of Tenax GC are required to achieve maximum recovery of each g of diisopropyl methylphosphonate (Caton et al. 1994). By extrapolating these... 

A second type of interference is ionization interference. Certain elements, particularly the alkali metals in high temperature flames, become partially ionized in the flame. This event causes a decrease in the number of neutral atoms and hence, a decrease in the sensitivity. For example, an appreciable fraction of sodium atoms will be ionized. Now if another easily ionized element such as potassium is added to the sodium solution, it will contribute free electrons to the flame and cause the equilibrium for the sodium ionization to shift toward the formation of a larger fraction of neutral atoms. This is, therefore, a positive interference. It can be overcome by adding the same amount of interfering element to the standard solution. Or, more simply, a large amount of an ionizable element such as potassium (200 to 1000 ppm) can be added to both sample and standard solutions this will effectively suppress ionization to a small and constant value and at the same time increase the sensitivity. 

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