Flame Propagation and Combustion Phenomena in a Confined Space with the Perforated Plate at Different Positions
Flame acceleration and flame–shock interactions are important physical phenomena in combustion science. The primary contribution of this work is to observe different combustion phenomena in the flame acceleration process and during flame–shock interactions in a confined space with a perforated plate. The effect of the perforated plate is to generate a rapidly accelerating flame. The experiment is conducted with an improved experimental apparatus with larger optical windows to observe the complete flame development process and the results are obtained using high-speed Schlieren photography. The complete process is observed clearly, including jet flame formation, turbulent propagation, and shock formation and propagation. Meanwhile, the obvious propagation of the turbulent flame, shock waves and reflected shock waves in burnt and unburnt materials is observed clearly in our experiment in terms of flame–shock interactions. The present results indicate that the perforated plate positions can change the flame propagation as well as the in-cylinder pressure oscillation, and affect the combustion intensity in the confined space significantly. For the middle distance between spark plug and perforated plate (position A), the flame tip velocity after perforated plate increases with increasing hole size. In contrast, the significantly different flame propagation behaviors can be obviously observed for the small distance between the spark plug and perforated plate (position B). The flame tip velocity decreases with increasing hole size initially after the flame passes through the perforated plate. Subsequently, a large hole size results in a turbulent eddy with a larger eddy structure, and consequently the turbulent flame acceleration behavior becomes more obvious for the hole size of 5 mm. Furthermore, a reflected shock wave with a sequence of compression waves with oscillating propagation in the confined space is observed experimentally. The present work could provide valuable insights into super-knocking combustion in gasoline engine, fire-safe fields in mining operations and buildings.