Theoretical analysis of environmental and energetic performance of very high temperature turbo-jet engines

Abstract

Current progress in gas turbine performance is achieved mainly by increasing the turbine inlet temperature. State of-the-art military aircraft gas turbines operate with turbine inlet temperatures exceeding 2 000 K, and future development plans call for even higher temperature levels. At such high temperatures, the hot combustion gases can no longer be considered as chemically inert, and it becomes important to account for the chemically reactive nature of the expanding flow. In this paper, the authors present a one-dimensional model of the chemically reactive flow through the first turbine stage of an aircraft turbo-jet engine. The model is used to study the impact of chemical reactivity on pollutant emission characteristics and engines performance (i.e. overall efficiency and specific thrust). Three different casess are considered: sea-level static operation (take-off), commercial aircraft in subsonic cruising at 10 000 m altitude, and military aircraft in supersonic flight at 20 000 m altitude. The results of this study show, for instance, that the production of environmental pollutants in the turbine as a result of chemical reactivity is particularly significant for turbo-jets operating at subsonic cruise velocities. Moreover, in both flight conditions considered, the increase of operating temperature decreases the overall efficiency.