Evaluating the Burning Velocity of Gaseous Fuels for Engine Applications: the DHARMA Project 2011-24-0056

Characterization of combustion parameters of gaseous fuels is the main objective of a novel experimental laboratory, which recently became operational at Istituto Motori: the "Device for Hydrogen-Air Reaction Mode Analysis" (DHARMA in brief) project is meant to generate a systematic database on the burning properties of CH₄, H₂ and other species of interest, in conditions typical of i.c. engines. The experimental setup is based upon an optically accessible cylindrical bomb, where tests are carried out on spherical expanding flames. High-speed shadowgraph is used to record the flame growth and to infer laminar burning parameters. Thorough details are given of the experimental apparatus and the data analysis. Experimental data are presented for the combustion in air of CH₄ and of CH₄/H₂ mixtures: the percentage of hydrogen was 20% and 30% (vol.). The tests have been performed under the same conditions: equivalence ratio was 1.0, initial pressure and temperature were 6.0 bar and 293 K, respectively. Data analysis yielded the laminar burning velocity and Markstein length: the variation of these parameters has been evidenced as a function of the hydrogen content. The obtained results have been compared to those available in literature, showing a good agreement.