Thermodynamic simulation of a multi-step externally fired gas turbine powered by biomass

Abstract

[EN]A thermodynamic model for a realistic Brayton cycle, working as an ex- ternally red gas turbine fueled with biomass is presented. The use of an external combustion chamber, allows to burn dirty fuels to preheat pure air, which is the working uid for the turbine. It also avoids direct contact of ashes with the turbine blades, resulting in a higher life cycle for the turbine. The model incorporates a high temperature heat exchanger and an arbitrary number of turbines and compressors, with the corresponding number of in- tercoolers and reheaters. It considers irreversibilities such as non-isentropic compressions and expansions, and pressure losses in heat input and release. The composition and temperature of the combustion gases, as well as the variable ow rate of air and combustion gases, are calculated for speci c biomasses. The numerical model for a single stage con guration has been validated by comparing its predictions with the data sheets of two commer- cial turbines. Results are in good agreement. Curves on the dependence of thermal e ciency and power output with the overall pressure ratio will be shown for several plant con gurations with variable number of compres- sion/expansion stages. Also the in uence of di erent types of biomasses and their moisture will be analyzed on parameters such as fuel consumption and exhaust gases temperature.