Experimental and Numerical Study on Effect of Sample Orientation on Auto-Ignition and Piloted Ignition of Poly(methyl methacrylate)
Abstract
:1. Introduction
2. Experimental Details
2.1. Apparatus Methods
2.2. Procedure and Observed Fire Behavior
3. Numerical Modeling
Orientation | 0° | 15° | 30° | 45° | 60° | 75° | 90° |
---|---|---|---|---|---|---|---|
g(x) | 0 | −2.539 | −4.905 | −6.937 | −8.496 | −9.476 | −9.81 |
g(z) | −9.81 | −9.476 | −8.496 | −6.937 | −4.905 | −2.539 | 0 |
4. Results and Discussion
4.1. Ignition Time
4.1.1. Piloted Ignition
4.1.2. Auto-Ignition
Orientation | a | b | R-Square | |
---|---|---|---|---|
0° | 0.00397 | −0.3728 | 0.97382 | 9.39 kW/m2 |
15° | 0.00367 | −0.04108 | 0.90971 | 11.19 kW/m2 |
30° | 0.00307 | −0.05143 | 0.94509 | 16.75 kW/m2 |
45° | 0.000684 | −0.0155 | --------- | 22.63 kW/m2 |
4.2. Mass Loss Rate
4.2.1. Piloted Ignition
4.2.2. Auto-Ignition
4.3. Heat Flux
4.3.1. Radiant Heat Flux
4.3.2. Convective Heat Flux
4.3.3. Net Heat Flux
4.4. Surface Temperature
4.5. Fuel Concentration
4.6. Discussion
5. Conclusions
- (1)
- In piloted ignition conditions, both the ignition time and critical mass loss rate at ignition have a U-shape relationship with the sample orientation angle α. The U-shape relationships indicate there is a specific α which makes the ignition time and critical mass loss rate is at a minimum. In auto-ignition conditions, both the ignition time and critical mass loss rate at ignition decrease with sample orientation angle α, but the critical heat flux increases from 9.39 to 22.63 kW/m2 as α increases from 0° to 45°.
- (2)
- Both the convictive heat flux loss and the inflow of radiant heat flux grows with sample orientation angle as α increases from 0° to 75°. As a result of the combination of the convective and radiant heat flux, the total incident heat flux at the solid surface decreases with α which makes the surface temperature of solid decrease. This makes the auto-ignition harder to occur with the increasing of the orientation angle. Because of the laminar air flow of vertical placed samples, the angle of α = 90° does not obey the same rule.
- (3)
- Influenced by the increasing incident heat flux at sample surface and different gas flow of volatiles, the fuel concentration at the pilot place has a U-shape and results to the U-shape profile of ignition time and critical mass loss rate of piloted ignition.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Peng, F.; Zhou, X.-D.; Zhao, K.; Wu, Z.-B.; Yang, L.-Z. Experimental and Numerical Study on Effect of Sample Orientation on Auto-Ignition and Piloted Ignition of Poly(methyl methacrylate). Materials 2015, 8, 4004-4021. https://doi.org/10.3390/ma8074004
Peng F, Zhou X-D, Zhao K, Wu Z-B, Yang L-Z. Experimental and Numerical Study on Effect of Sample Orientation on Auto-Ignition and Piloted Ignition of Poly(methyl methacrylate). Materials. 2015; 8(7):4004-4021. https://doi.org/10.3390/ma8074004
Chicago/Turabian StylePeng, Fei, Xiao-Dong Zhou, Kun Zhao, Zhi-Bo Wu, and Li-Zhong Yang. 2015. "Experimental and Numerical Study on Effect of Sample Orientation on Auto-Ignition and Piloted Ignition of Poly(methyl methacrylate)" Materials 8, no. 7: 4004-4021. https://doi.org/10.3390/ma8074004