Laminar burning properties of biogas and syngas for gas turbine retrofit

Biogas and syngas fuels have been evaluated as candidate replacement of methane in gas turbines. The combustion properties of binary gas mixtures mimicking biogas and syngas were compared to CH4, in the same operating conditions. Tests were performed in the high-pressure, constant-volume DHARMA reactor at Istituto Motori - CNR. The laminar burning parameters were obtained from the analysis of outwardly propagating spherical expanding flames. The flame growth was recorded by means of high-speed, high-resolution shadowgraph; image processing and stretch analysis were used to infer the laminar burning velocity and the Markstein length for each test case. Results are presented for the combustion in air of CH4-CO2 (representative of biogas) and H2-CO (representative of syngas). All the tests were performed at 0.4 MPa and 297 K. The equivalence ratio ranged between 1.0 and the lower flammable limit. The unstretched laminar burning velocity and the Markstein length are reported for each fuel as a function of the equivalence ratio.