CURRENT PROGRESS AND FUTURE-TRENDS IN TURBULENT COMBUSTION

This article discusses some recent progress and future trends in turbulent combustion. Issues in turbulent combustion modeling (TCM) and some perspectives in active control are specifically considered. Modeling methods are first briefly surveyed to identify future developments. It is anticipated that further progress will be made in physical modeling based on flame surface density concepts and that physical modeling of turbulent flames will rely more heavily on modern computational tools like direct numerical simulation (DNS), large eddy simulations (LES), detailed numerical modeling (DNM) of simple flames. Physical modeling as it is practiced today will continue to evolve into more reliable methods for industrial design applications. As the computational resources progress one may also foresee that LES methods will take over and that research will shift from the Reynolds average approach to the more advanced LES computation of turbulent reactive flows. Because turbulent combustion is so complex, physical modeling and LES calculations will continuously need detailed experiments. These will emphasize field measurements based on imaging methods. It is expected that current progress in optical diagnostics will continue. Imaging diagnostics will become more easily applicable to practical situations. Their spatial and temporal resolution will be enhanced. Images will continue to provide qualitative information on the basic processes of turbulent combustion but improved experimental methods will yield more quantitative data. Another area which holds promises is that of active control. From current progress in this field one may foresee that advanced control schemes will play an increasing role in experimental investigations of instabilities and in practical optimization of turbulent combustors. ''Intelligent combustor'' concepts combining control loops with a combustion system are now being explored and will probably become of importance in enhancing the stability of combustion, in augmenting the domain of operation and in reducing the pollutant emission levels.