Combustor Design for Low Emissions and Long Lifetime Requirements

Abstract

Advanced combustor design for gas turbines in power generation is driven by reliability, lifetime and emission requirements, by needs for fuel flexible operation, and minimization of cost of electricity. The present paper explains in detail the basic design principles of the annular combustors, as implemented in the most recent upgrades of the GT13E2 and GT24/GT26 engine families. One fundamental principle is the choice of a premix burner system with low pressure drop, allowing serial combination of a convective cooling scheme by fuel-air premixing with almost all available air. This allows operating at the lowest possible flame temperature, for a given hot gas temperature, thus assuring the minimum NOx emissions. Introduction of advanced seals reduce the leakage of air, helping further to reduce the flame temperature and improve burnout and stability. A second distinct feature of annular combustors is the possibility of single- and multiple-row burner arrangements for optimized operational flexibility. Burner arrangements are further optimized to yield the best stability with low heat loads to combustor walls and more uniform exit temperature distribution over the entire engine load range. Another feature of the modular combustion chambers is the separation of cold load-carrying structures and hot heat-shielding elements, which allows for easy maintenance and minimization of air leakages. Examples for the most recent component upgrades will be given in the full paper, with a focus on the reheat (SEV) combustor improvements for increased robustness and life-time, whilst maintaining combustion performance and minimizing cost. Field-feedback has proven to be an important element to understand and exploit the full lifetime potential of this design concept. A comprehensive account of field data from both EV and SEV combustors are presented, accounting more than one and a half decade long operation experience with annular combustors.