On the effects of uncertain amounts of residual impurities in shock-tube measurements of hydrogen ignition times

This study addresses the influences of uncertain amounts of residual impurities in the computation and experimental determination of ignition-delay times in hydrogen-air mixtures in shock tubes. Experimental methods for quantifying impurities in shock tubes are described and utilized. These methods are utilized to infer an equivalent amount of impurities as a function of the initial temperature of the mixture in the shock tube. A statistical model of the concentration of impurities is constructed and used for calculations of ignition delays based on short and detailed chemical descriptions.