Experimental Determination of Hydrogen-Air Laminar Burning Velocities, and the Effect of Water Mist

This research project characterises an experimental set-up with the aim of finding laminar burning velocities of premixed hydrogen-air (dry) mixtures, at initial pressure and pressure of 294 K and 1 bar, using a 20 litre cubic explosion chamber. Two different methods were employed; a constant-pressure method (CPM) applied with a schlieren imaging technique, and a constant-volume method (CVM) adopting the pressure-time history. Regarding the former method, linear and non-linear relation between the propagation of flame and stretch rate was employed to obtain the unstretched flame and burning velocity. Using the pressure measurements during the transient dispersion process, CPM using a pressure transducer was employed to calculate the burning velocity, relating the pressure rise to the radius of the flame. Both measuring techniques gave laminar burning velocities in agreement, with a maximum relative difference of 10 %. Observed wrinkling in the flame propagation due to hydrodynamic instabilities, in addition to limitations associated with experiments performed in a cubical vessel, made it difficult to produce quantitative results unison with those found in other literature. Using a nozzle, hydrogen-air mixtures were introduced to water mist with concentrations between 0.08-0.3 m^3/kg. This was done to investigate its influence on the laminar burning velocity. The inclusion of water mist gave burning velocities increased with as high as 100 %, compared to the dry results. This was mainly due to the generation of turbulence during the injection of water mist