CURRENT PROGRESS AND FUTURE-TRENDS IN TURBULENT COMBUSTION

This article discusses some recent progress and future trends in turbu lent combustion. Issues in turbulent combustion modeling (TCM) and som e perspectives in active control are specifically considered. Modeling methods are first briefly surveyed to identify future developments. I t is anticipated that further progress will be made in physical modeli ng based on flame surface density concepts and that physical modeling of turbulent flames will rely more heavily on modern computational too ls like direct numerical simulation (DNS), large eddy simulations (LES ), detailed numerical modeling (DNM) of simple flames. Physical modeli ng as it is practiced today will continue to evolve into more reliable methods for industrial design applications. As the computational reso urces progress one may also foresee that LES methods will take over an d that research will shift from the Reynolds average approach to the m ore advanced LES computation of turbulent reactive flows. Because turb ulent combustion is so complex, physical modeling and LES calculations will continuously need detailed experiments. These will emphasize fie ld measurements based on imaging methods. It is expected that current progress in optical diagnostics will continue. Imaging diagnostics wil l become more easily applicable to practical situations. Their spatial and temporal resolution will be enhanced. Images will continue to pro vide qualitative information on the basic processes of turbulent combu stion but improved experimental methods will yield more quantitative d ata. 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 comb ustion system are now being explored and will probably become of impor tance in enhancing the stability of combustion, in augmenting the doma in of operation and in reducing the pollutant emission levels.