Operability of Fuel/Oxidizer-Flexible Gas Turbine Combustors

Abstract

In this chapter, the operability of gas turbine combustors under fuel-flexible and oxidizer-flexible combustion conditions is evaluated based on experimental and numerical investigations, and the results are compared with those of non-flexible gas turbine combustors. Stability and combustion characteristics of the different flames in premixed combustors considering different fuels with/without hydrogen enrichment and under air or oxygen combustion conditions are discussed. Several combustion techniques have been proposed, reviewed, and evaluated aiming at decreasing the greenhouse gas emissions, primarily CO2. Among these techniques, oxy-fuel combustion stands out as a promising carbon capture and storage (CCS) technology that can be implemented in new power plants and with little hardware retrofitting in the existing systems. However, fuel combustion in pure oxygen environment results in high combustion temperature, which may not be suitable for safe operation of gas turbine blades. Premixing the reactants in an environment of recirculated CO2 under premixed oxy-combustion condition can control the combustion temperature for safe operation of the turbine blades while controlling the emissions. The main target of gas turbine manufacturers is to design versatile environmental-friendly gas turbine combustors that can handle different fuel and oxidizer compositions. This chapter evaluates the operability of gas turbine combustors of novel burner designs capable of handling different fuels and oxidizer compositions for the sake of better performance at the minimum emissions levels. This chapter investigates the stability and combustion features of C3H8/O2/CO2 flames in a model dry low emissions (DLE) gas turbine burner adopting lean premixed (LPM) oxy-fuel combustion technology. Relationship between the flame speed (FS) and the adiabatic flame temperature (Tad) is premeditated for better analyzing and predicting the flame behavior. The stability of the flame is characterized by its blowout and flashback limits over ranges of equivalence (ϕ) ratio and oxygen fraction (OF: volumetric concentration of O2 in the O2/CO2 oxidizer mixture). Flame shapes at different sets of conditions are investigated. The effects of fuel type and hydrogen-enrichment are investigated based on experimental and numerical investigations considering C3H8/O2/CO2 and CH4/H2/O2/CO2 flames operated on the same gas turbine model combustor. In addition, results out of three-dimensional (3-D) transient large eddy simulations (LES) are presented considering premixed C3H8/O2/CO2 and CH4/H2/O2/CO2 flames under various combinations of ϕ and OF to have more insight on flow, combustion, and emission characteristics. The temperature and species concentration distributions, flow field, and flame structure are also presented and discussed.