Experimental Study on Combustion Characteristics of Conventional and Alternative Liquid Fuels

Gas turbine combustor design relies strongly on the turbulent flame velocity over the whole turbine operation range. Due to the fact that turbulent flame velocity depends strongly on the laminar one, its characterization at different thermodynamic conditions is necessary for further optimization of gas turbines. The Markstein number, which quantifies the response of the flame to the stretch, also has to be considered. Additionally, the Markstein number can be utilized as an indicator for laminar and turbulent flame front stability. Current attempts to replace conventional fuels, such as kerosene, with alternative ones, obtrude their comparison in order to find the most appropriate substitute. Additionally, significant differences in the flame behavior, which could be recognized through different combustion characteristics, can lead to modification of currently used gas turbine design. Even so, the experimental data of alternative fuels are scarce, especially at elevated pressure conditions. So, the combustion characteristics, laminar burning velocity, and Markstein number of kerosene Jet A-1 and several alternative fuels (gas to liquid (GTL) and GTL blends) are investigated experimentally in an explosion vessel. For this purpose an optical laser method is employed based on the Mie-scattering of the laser light by smoke particles. Within this experimental study the influence of three crucial parameters, initial temperature, initial pressure, and mixture composition on the burning velocity and Markstein number, are investigated. The experiments are performed at three different pressures 1, 2, and 4 bar; three different temperatures 100 °C, 150 °C, and 200 °C; and for a range of equivalence ratio 0.67–1.67. The observed results are compared and discussed in detail.