Turbulent Flames in Enclosed Combustion Chambers: Characteristics and Visualization - a Review

Remarkable progress has been achieved in measuring the flame propagation rate accurately under laminar conditions, which can be used to predict turbulent flame propagation rates using some correlations fitted to experimental data. However, such propagation rates, unlike the laminar case, cannot be unambiguously determined. Nevertheless, the advancement of laser imaging techniques has led to several definitions of turbulent burning rates (Roshan et al., 2010, "Simulation of Global Warming Effect on Outdoor Thermal Comfort Conditions," Int. J. Environ. Sci. Technol., 7(3), pp. 571-580). Recently, a unified scaling factor has been successfully demonstrated using data gathered from several fan-stirred bombs. Such results are promising in compiling a comprehensive database of turbulent propagation rates for potential and common fuels of interest to internal combustion engines (ICEs) and gas turbines alike. The strict worldwide legislation to reduce emissions has forced many industries to look into alternative fuels with less emissions. One such alternative fuel that has gained much interest recently is the gas-to-liquid (GTL) fuel, which is being used in blended forms in several combustion applications. However, detailed combustion characteristic investigations are required before using this new alternative fuel widely in engines (Business, 2018, "Qatar's Exporters Directory 2018"). In this study, the significant issues associated with the use of fan-stirred bombs are investigated. First, the effect of varying fan speed and geometry is reviewed, and then, the measurement techniques that are commonly used to track flame propagation are discussed. This is followed by the study of the effect of using different types of fuels on combustion characteristics. Furthermore, the use of diesel and gasoline optical engine setups as advanced flame visualization tools have been reviewed extensively.