This paper reports the results of high-pressure combustion rig testing carried out to assess the fuel flexibility of the standard Siemens Energy SGT-300-2S dry low emission (DLE) combustion system operated at engine conditions across a wide range of engine loads and ambient conditions. Variations of the fuel heating value, with Wobbe Index (WI) of 23 MJ/Sm3, 25 MJ/Sm3, 27.5 MJ/Sm3, 30 MJ/Sm3 and 45 MJ/Sm3 (UK natural gas) at standard conditions1, were achieved in a mixing plant by blending natural gas with CO2 as diluent. Emissions, fuel pressure, combustion dynamics, and flashback monitoring via measurement of burner and combustor can metal temperatures were the main parameters used to assess the effect of fuel flexibility on combustor performance. Test results show that NOx emissions decrease as the fuel heating value is reduced due to lower adiabatic flame temperatures for the MCV (Medium Calorific Value) fuels. CO emissions performance was found to be unaffected. However, decreasing fuel heating value leads to a requirement to increase the fuel supply pressure as a consequence of higher volumetric fuel flow rate to achieve the heat input requirements of the gas turbine. Combustion dynamics characteristics were found to be similar for the different fuel compositions. The impact of fuel heating value change on turbine nozzle guide vanes and blades was also investigated by measuring the combustion hot gas temperature profile at the exit of transition duct. The results show that there is no significant change in turbine entry temperature profile in terms of maximum temperature and pattern factors.

The successful development program has expanded the capability of the SGT-300-2S standard production DLE combustor to operate with a range of fuels covering a WI range of 25 MJ/Sm3 to 49 MJ/Sm3. The test results obtained on the SGT-300-2S combustion system provide significant experience for industrial gas turbine burner design for fuel flexibility.

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