Gas turbine combustion: Prospects and challenges

Abstract

Gas turbines, first postulated and conceptually analyzed during the first decade of the twentieth century, became engineering reality in the late 1930s. During the last 50 years, aircraft gas turbine technology has developed gradually and continuously. The two families of gas turbines, aircraft and stationary, share a certain similarity, although their design requirements are significantly different. Both cases, however, incorporate interdependent phenomena of three-dimensional multi-component flowfields with complex multiphase chemical kinetics, evaporation and heat transfer processes, all occurring simultaneously. Despite the many advances in combustor design, the challenge to ingenuity in design is now greater than ever before. New concepts and technology are still needed to satisfy the current and projected pollutants emission regulations and to provide energy conservation. Environmental challenges with gas turbines include low levels of NO x , CO and soot amongst other pollutants. Specifically, ultra-low NO x combustor technology is required to meet the ozone depletion challenge. Researchers are facing concerns about the development of dry low-NO x stationary and aero engines. Advanced concepts for environmental pollution control require detailed understanding of the physical and chemical processes that occur during combustion. Fundamental combustion research needs to be done in the areas of interactions between droplet, turbulence and chemistry, computer model development, gas and solid phase kinetics, droplet/droplet interaction, soot formation and chemistry, and flame structure. Data from laboratory-scale, bench-scale and prototype are urgently required, that provide isolated effect of chemistry, fuel droplet/air mixing, injector and combustor geometry, combustion air swirl and flow distribution. It is expected that the future combustors will be even shorter (and of less weight) than they are today, operate at higher temperatures and pressures and utilize a much broader range of fuels. Applied combustion research needs include, clean and energy efficient combustion of a broad range of fuels and the associated reduction of pollution through combustion control. Improvements in optical diagnostics, computer power and software, and numerical algorithms will grow in the future to give combustor developers and researchers new and greater insights within gas turbine combustors. Both experimental and theoretical combustion engineers need greater understanding of the combustion processes. Gas turbine engines will find even greater use in power plants in the future due to their low environmental impact and conservation of natural resources.