Ignition time

Emission factors must be also critically examined to determine the tests from which they were obtained. For example, carbon monoxide from an automobile will vary with the load, engine speed, displacement, ambient temperature, coolant temperature, ignition timing, carburetor adjustment, engine condition, etc. However, in order to evaluate the overall emission of carbon monoxide to an area, we must settle on an average value that we can multiply by the number of cars, or kilometers driven per year, to determine the total carbon monoxide released to the area. 

Minimization of pollutants from the combustion chamber. This approach consists of designing the engine with improved fuel-air distribution systems, ignition timing, fuel-air ratios, coolant and mixture temperatures, and engine speeds for minimum emissions. The majority of automobiles sold in the United States now use an electronic sensor/control system to adjust these variables for maximum engine performance with minimum pollutant emissions. 

Ignition time function (30 seconds allowed for establishing flame on both detectors or the unit will be shut down after several tries). 

Ignition time function (to de-energize ignition at the proper time). 

Some of the parameters that affect VCE behavior25 are quantity of material released, fraction of material vaporized, probability of ignition of the cloud, distance traveled by the cloud before ignition, time delay before ignition of cloud, probability of explosion rather than fire, existence of a threshold quantity of material, efficiency of explosion, and location of ignition source with respect to release. 

In dimensional terms, this adiabatic ignition time is... 

Applying Equations (5.21) to the adiabatic time corresponding to the critical Damkohler number, and realizing for a three-dimensional pile of effective radius, r,. A 3 (e.g. Sc = 3.32 for a sphere for Bi —> oo), then we estimate a typical ignition time at 6 = Sc 3 of... 

Let us return to our discussion of the prediction of ignition time by thermal conduction models. The problem reduces to the prediction of a heat conduction problem for which many have been analytically solved (e.g. see Reference [13]). Therefore, we will not dwell on these multitudinous solutions, especially since more can be generated by finite difference analysis using digital computers and available software. Instead, we will illustrate the basic theory to relatively simple problems to show the exact nature of their solution and its applicability to data. 

Figure 7.11 Ignition times as a function of incident heat flux [15]...

Scatter in these data indicate accuracy, but they suggest that the earliest ignition time would be piloted, followed by glowing and then autoignition. This still may not preclude the effect of smoldering on piloted ignition at very low heat fluxes, as occurs with autoignition at 40 kW/m2. 

This is identical with our result for the ignition time at a high heat flux in the thermally thin ignition of a solid. It can be generalized to say that flame speed - thermally driven -can be represented as the ratio of the flame extension length to the time needed to ignite this heated material, originally at 7). 

Table 5 Ignition-time measured in the ASTM E 1354 cone calorimeter and thermal response parameter values derived from the data... 

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