Spark electrodes

Eigure 3-5.4.1 was constructed from data in Table A-4-1.3. It shows that hydrogen s LMIE is found for small diameter spark electrodes using a circuit having a small capacitance and hence a small RC time constant. The same general trend is also found for methane and is primarily due to reduced... 

The answer is "NO." In the combustible mixture, an electric spark produces a flame kernel. Initially, its shape is elliptical (like an American football), and then becomes a torus (like an American doughnut). Afterwards, it changes into almost spherical shape, and propagates spherically in the unbumed mixture. This process is formed by the existence of spark electrodes, which is necessary for spark discharge. Spark electrodes lead not only to heat loss from the flame kernel but also a change in the kernel shape. Both affect the minimum ignition energy. 

Schlieren photograph of flame kernels by a high-speed camera. Time is given from the onset of spark discharge in microseconds. Spark electrode diameter 0.2 mm spark gap width 1mm. 

The boundary conditions are as follows In Figure 3.2.2, z-axis component and r-axis component velocities are zero for (1) and (2), respectively. The gradients of other variables are zero for both the boundaries. The gradients of all variables are zero for (3) and (4). No slip condition and heat transfer from the flame kernel to the spark electrode are assumed for (5) and (6), at the surface of spark electrode. 

For simplicity of the model, it is assumed that the natural convection, radiation, and ionic wind effect are ignored. The ignorance of the radiation loss from the spark channel during the discharge may be reasonable, because the radiation heat loss is found to be negligibly small in the previous studies [5,6]. The amount of heat transfer from the flame kernel to the spark electrodes, whose temperature is 300 K, is estimated by Fourier s law between the electrode surface and an adjacent cell. 

Calculated time series of temperature distribution. Spark energy O.ZOmJ spark gap width 1.0mm spark electrode diameter 0.50mm ratio of capacity spark energy 100%. Left time = 1 ps, central time = 10 ps, right time = 100 ps. 

Relationship between the ratio of capacity spark energy and the minimum ignition energy obtained from experiments. Equivalence ratio of mixture 0.62. Spark gap width 0.5mm spark electrode diameter 1.0mm. 

Colloidal Niobium.—Sols of niobium have been prepared by sparking electrodes of the metal immersed in wobutyl alcohol by means of an induction coil,3 or by reducing solutions of niobium salts with hydrazine, formic acid or formaldehyde in the presence of gelatose.4... 

Fig. 3 Flame housing of IL 943 flame photometer a) sodium filter, 589 nm b) potassium filter, 776 run c) lithium filter, 670 nm d) cesium filter, 852 nm e) ignition detector f) burner assembly g) rubber gasket h) spark electrode i) ignition coil wire j) chimney. (Courtesy of Instrumentation Laboratory, Inc.)...

The experiments reported here show the chemical effect of heat loss to the spark electrodes in the ignition process. For rapid sparks of the type used here, flame development begins about 0.2 cm away from the electrodes rather than at the electrodes or at the edge of the spark kernel. This new chemical information provides a description of the spark ignition process which has... 

The cubic form of WC has a parameter which is remarkably close to the value obtained when the lattice parameter of the TiC WC solid solution is extrapolated to pure WC (Metcalf, 1946). Sara (1965c) quenched a parameter of a = 4.215 A, while Rudy et al. (1966) obtained a constant value of a = 4.220 A, regardless of the composition or the quenching temperature. On the other hand, Willens and Buehler (1965) gave a = 4.266 A when the a and forms were found together, a = 4.252 A for pure ) -WC and a = 4.240 A for a mixture of j8-WC and WjC. The superconductivity transition temperature showed the same trend. When the phase was prepared by sparking electrodes of a-WC under oil, a parameter of 4.250 A was observed (Lautz and Schneider, 1961). 

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