Design & development of a landfill gas combustion system for the typhoon gas turbine

Abstract

This paper presents design, initial combustion development testing and engine validation results of a combustion system which is capable of burning a medium CV landfill gas or conventional diesel oil in a 5MW gas turbine. Initial rig testing of the original combustion system burning a simulated medium CV gas revealed stability problems and inherently poor combustion efficiencies. A study of primary zone flow patterns and fuel placement led to the conclusion that the problems were due to axial injection of the gas. Subsequently a modified dual fuel injector was designed which relied on swirled instead of axial injection. The modified injector design also embodies a passive Purge feature, which uses combustor wall pressure drop to feed air directly into the gas swirlier passages. This prevents ingestion of harmful combustion products when running on diesel oil. Extensive rig testing demonstrated encouraging combustion efficiencies and emissions using 40% and 54% methane landfill gas compositions across a simulated engine load profile. Operation of the modified injector on diesel oil however, demonstrated a need for the incorporation of an anti-carbon feature The effectiveness of this anti-carbon modification was verified as part of a 'validation engine cycle' simulating the actual engine operating procedure from light up to shutdown. Post test inspection revealed carbon deposition to be significantly reduced. Combustion efficiencies, emissions, traverse quality, metal temperatures, stability and noise were all found to be satisfactory.