A Method for Evaluating Fully Developed Turbulent Flame Speed

Fan-stirred bombs, which are widely used worldwide, offer an unique opportunity to investigate basic features of S.I. engine combustion under well-defined experimental conditions. Extensive data bases on turbulent flame speeds have been generated by various groups utilizing such bombs. However, the use of these data bases is impeded by the fact that the measured flame speeds characterize an inherently transient process, i.e.. the speeds are time-dependent even if the pressure and the unburned gas temperature in the bomb are very close to the initial values; whereas the combustion theory and various models deal commonly with an asymptotically fully developed turbulent flame speed. The goal of this work is to test a method for evaluating the latter quantity by processing the published data on the flame radius growth, measured in expanding, statistically spherical, premixed flames. For these purposes, an experimentally well-supported parameterization of the mean turbulent flame brush thickness development is invoked. The obtained results seem to be encouraging and they support the method for evaluating asymptotically fully developed turbulent flame speeds.