Ignition energy curves

Tbe partial results are shown in Figure 2-6.2.1. Tbe ranges of ignitable concentrations are superimposed on a spark ignition energy curve for bexane in air calculated from data in [56]. Both data sets are assumed to be characteristic ofn-hexane, unbiased by the presence of methylcyclopentane or hexane isomers (dimethylbutanes and methylpentanes). 

Figure 7a. Ignition energy curve. The peak temperature is shown as a function of time. The change is the magnitude of the gravitational acceleration, 0 g0. The excess energy required (above that predicted by the IPM) is shown as a percentage of E0 = 4.67 X 10. ...

Appendix H lists minimum ignition energies of many fuels for the stoichiometric condition at a pressure of 1 atm. The Blanc data in this appendix are taken from Fig. 7.6. It is remarkable that the minima of the energy curves for the various compounds occur at nearly identical values. 

The values of kinetic parameters (pre-exponential factors k0j and activation energies Ej of rate constants k and inhibition constant Kg) can for a particular catalyst be determined by weighted least squares method, Eq. (35), from the light-off or complete ignition-extinction curves measured in experiments with slowly varying one inlet gas variable—temperature or concentration of one component (cf., e.g., Ansell et al., 1996 Dubien et al., 1997 Dvorak et al., 1994 Kryl et al, 2005 Koci et al., 2004c, 2007b Pinkas et al., 1995). 

Figure 21. The relationship between light energy for ignition and temperature for lead azide [119]. The solid line gives the experimental curve the dotted line connects the value for the ignition energy at 20° C and the point on the temperature axis corresponding to the thermal ignition temperature.

Fig. 4.18 Minimum ignition energy for H2 + air mixtures for laser ignition (the solid curve) and at spark ignition (the dashed curve). Atmospheric pressure and room temperature...

U-shaped curve, we have mixtures that can be ignited for a sufficiently high spark energy. From Equation (4.25) and the dependence of the kinetics on both temperatures and reactant concentrations, it is possible to see why the experimental curve may have this shape. The lowest spark energy occurs near the stoichiometric mixture of XCUi =9.5%. In principle, it should be possible to use Equation (4.25) and data from Table 4.1 to compute these ignitability limits, but the complexities of temperature gradients and induced flows due to buoyancy tend to make such analysis only qualitative. From the theory described, it is possible to illustrate the process as a quasi-steady state (dT/dt = 0). From Equation (4.21) the energy release term represented as... 

Figure 168 is an idealization because it does not take into account the energy required to heat the source, ie the wire, to some critical temperature. This critical temperature should be close to that of the flat portion of the lower curve of Fig 168. If one assumes that the critical wire temperature remains constant in any given ignition system, and allows for heat losses by the wire ... 

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