Performance analysis of a biogas-fueled micro gas turbine using a validated thermodynamic model

• The MGT performance and fuel flexibility were investigated in biogas application.
• A thermodynamic model of the MGT was developed and validated with experimental data.
• Changes in performance and operating conditions of components were studied.
• The results showed the viability of the MGT for use in biogas application.

This study focuses on an investigation of the fuel flexibility and performance analysis of micro gas turbines (MGTs) in biogas application. For this purpose, a steady state thermodynamic model of an MGT was developed and validated by experimental data obtained from a 100 kW MGT test rig. Quite good agreement was obtained between the measurements and the simulation results. A wide range of biogas compositions with varying methane content was simulated for this study. Necessary minor modifications to fuel valves and compressor were assumed to allow engine operation with the simulated biogas composition. The effects of biogas on the engine performance were fully analyzed at various operational conditions by changing the power demand and also the ambient temperature. Compared to the natural gas fueled case, the mass flow and pressure ratio in the MGT decreased, which resulted in a slight reduction of the surge margin. This effect became more severe, however, at low power loads and/or low ambient temperatures. For all operational conditions, the electrical efficiency decreased with decreasing methane content of the biogas. The results also indicated the negative effect of the biogas on the heat recovery in the recuperator, which lowered as the methane content of the fuel decreased.