Simulation ignition

To simulate the effect of small flames that may result from faulty conditions within electronic equipment, the lEC 695-2-2 Needle Elame Test may be used. In this case a small test flame is applied to the sample for a specified period and observations made concerning ability to ignite, extent of burning along the sample, flame spread onto adjacent material and time of burning. 

Accidental vapor cloud explosions do not occur under controlled conditions. Various experimental programs have been carried out simulating real accidents. Quantities of fuel were spilled, dispersed by natural mechanisms, and ignited. Full-scale experiments on flame propagation in fuel-air clouds are extremely laborious and expensive, so only a few such experiments have been conducted. 

Hoff (1983) studied the effect of igniting natural gas after a simulated pipeline rupture by firing a bullet into the gas mixture. The tests were on a 10-cm diameter pipeline operating at an initial pressure of 60 bar and a gas throughput of 400,000 mVday. The openings created in the pipeline simulated full-bore ruptures. Maximum flame speeds of approximately 15 m/s, and maximum overpressures of 1.5 mbar were measured at a distance of 50 m. 

Hoff (1983) Ignition of spill after simulated pipeline rupture LNG 15 ... 

Hoff, A. B. M. 1983. An experimental study of the ignition of natural gas in a simulated pipeline rupture. Comb, and Flame. 49 51-58. 

The second category includes BLEVE simulation, in which a pressurized, heated flask containing liquid or liquefied fuel is broken after the desired vapor pressure has been reached, and the released vapor is then ignited. Measurement of fireball diameter, liftoff time, combustion duration, and final height is captured by filming with high-speed cameras. Radiometers are used to measure radiation and temperature is measured by thermocouples or by determination of fireball color temperature (Lihou and Maund 1982). 

Mullis (M10), Bastress (B4), and Carlson and Seader (Cl) have conducted experimental studies to determine the heat-transfer characteristics of typical rocket-exhaust igniters. In these studies, the total rate of heat transfer to the propellant or simulated propellant surface was measured as a function of mass flow rate, geometry, and impingement angle between the igniter exhaust... 

Figure 3.2.1 shows flame kernels of the schlieren photograph taken by a high-speed camera. These photographs can be compared with the calculated temperature distribution in Figure 3.2.4. As can be seen, both of them bear a close resemblance. From this result, the authors firmly believe that the numerical simulation is a significant tool for grasping the mechanism of spark ignition. Of course, the experimental work should also be of importance to verify the results obtained by numerical simulations. In this work, the authors mainly introduce the results of numerical simulations that have been obtained xmtil then in their laboratory.

Richard, S., Colin, O., Vermorel, O., Benkenida, A., Angelberger, C., and Veynante, D., Towards large eddy simulation of combustion in spark ignition engines. Proc. Comb. Inst., 2007. 31,3059-3066. 

In Chapter 3.2, M. Kono and M. Tsue examine the mechanism of flame development from a flame kernel produced by an electric spark. They discuss results of numerical simulations performed in their laboratory in confrontation with experimental observations and confirm numerical simulation as a significant tool for elucidating the mechanism of spark ignition. 

Chattopadhyay, S., Veser, G., Detailed simulations of catalytic ond non-catalytic ignition during H2-oxidation in a micro-channel reactor isothermal case, in Proceedings of the ChemConn-2001, pp. 1-6 (December 2001), Chennai,... 

The particular hazard of firedamp ignition relates to the circumstance when a hole fired early in the round breaks the coal at another hole and exposes the explosive before it detonates. This is simulated by firing gallery tests similar to those described above, but with inverse initiation of a... 

Model experiments on the mixture (simulating paint tailings) exposed to air showed that storage at low temperature (7°C) led to a larger build-up of peroxide than occurred at 35°C. This would account for spontaneous ignition of paint tailings (residues) stored at low temperature and subsequently heated to 60°C. 

The experimentation in the field of gas cloud fires appears to be limited. The unique set of large-scale experiments that involve the release, dispersion, ignition, and combustion of flammable natural gas clouds in the open air is that with the code name Coyote. Coyote series trials conducted by LLNL in 1983 at California s Nevada Test Site, Nevada provided an integrated dataset for use in validation studies [64,65]. The objective of the experiments was to determine the transport and dispersion of vapors from LNG spills, and in addition to investigate the damage potential of vapor cloud fires. Transient simulations... 

Rigas, F. and Sklavounos, S., Simulation of Coyote series trials—Part II a computational approach to ignition and combustion of flammable vapor clouds, Chem. Eng. Sci., 61, 1444, 2006. 

The MCI is created by detonating or igniting a test round(s), or item(s) with all items in the operational configuration in the shield, including the equipment or reasonable simulation thereof, that performs the intended function on the munitions. If the shield is intended to be used for a variety of rounds, the one(s) having the most severe effects for overpressure, fragmentation, thermal emissions and shape charge effects is to be tested. 

Both self-heating and self-ignition characteristics are commonly determined by adiabatic tests (self-heating) and hot-plate tests (self-ignition). These tests are limited in their applicability because they do not fully simulate the plant conditions. 

Previous studies of Vapor Cloud Explosions (VCE) have used a correlation between the mass of a gas in the cloud and equivalent mass of TNT to predict explosion overpressures. This was always thought to give conservative results, but recent research evidence indicates that this approach is not accurate to natural gas and air mixtures. The TNT models do not correlate well in the areas near to the point of ignition, and generally over estimate the level of overpressures in the near field. Experiments on methane explosions in "unconfined" areas have indicated a maximum overpressure of 0.2 bar (2.9 psio). This overpressure then decays with distance Therefore newer computer models have been generated to better simulate the effects... 

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