CORRELATIONS FOR TURBULENT FLAME SPEED OF DIFFERENT SYNGAS MIXTURES AT HIGH PRESSURE AND TEMPERATURE

There is an obvious lack of data and understanding of the behavior of turbulent flames at high temperature and high pressure, especially concerning hydrogen containing fuels. Among the many relevant parameters, the turbulent flame speed S-T is one of the most interesting for scientists and engineers. This paper reports an experimental investigation of premixed syngas combustion at gas-turbine like conditions, with emphasis on the determination of S-T/S-L derived as global fuel consumption per unit time. Experiments at pressures up to 2.00 MPa, inlet temperatures and velocities up to 773K and 150 m/s respectively, u'/SL greater than 100 are presented. Comparison between different syngas mixtures and methane clearly show. much higher S-T/S-L, for the former fuel. It is shown that ST/SL is strongly dependent on preferential diffusive-thermal (PDT) effects, co- acting with hydrodynamic effects, even for very high u'/S-L. S-T/S-L increases with rising hydrogen content in the fuel mixture and with pressure. A correlation for ST/SL valid for all investigated fuel mixtures, including methane, is proposed in terms of turbulence properties (turbulence intensity and integral length scale), combustion properties (laminar flame speed and laminar flame thickness) and operating conditions (pressure and inlet temperature). The correlation captures effects of preferential diffusive-thermal and hydrodynamic instabilities.