Prediction of flammable range of benzene/N2/O2/H2O mixtures using detailed kinetics.

• New measurements of Benzene flame speed in air. • Prediction of UFL and LFL at different pressures, temperatures and dilutions. • Quantification of the relevance of soot for flammability limits. • First comprehensive interpretation of all existing benzene flammability data. • Approach applicable to other high-sooting fuels. This research introduces an innovative approach to predict benzene Lower and Upper Flammability Limits (LFL and UFL). The focus of this study is on predicting the flammable range of benzene/air/steam mixtures utilizing a freely-propagating flame method, incorporating an optically-thin approximation to model soot radiation. The investigation delves into the consequences of dilution by inert gases (N 2 and steam), along with the impacts of pressure and initial temperature. Soot is recognized as essential not only for its role in flame chemistry under rich conditions but also for its influence on radiation, thereby affecting the flammable region of hydrocarbons especially at higher temperatures and pressures. To address the significant formation of soot during benzene combustion near the UFL, the study integrates the kinetic model for benzene combustion with a recently developed soot mechanism based on the discrete sectional method, which has been validated extensively against a large database of sooting flames, encompassing various hydrocarbons, including benzene. To limit the computational effort associated with predicting flammability limits, a skeletal version (with 136 species and 4788 reactions) of the overall kinetic model covering benzene combustion and soot formation is developed and validated in this work. The kinetic model was first validated against new and existing benzene flame speed data at different pressures and initial temperatures. Then it was used to investigate the flammable range. The model predictions align remarkably well with the available experimental data in the literature for the LFL, for the effect of dilution with inert gases, and with some experimental measurements for the UFL. An extensive review of these experimental data revealed significant uncertainty in characterizing benzene's UFL experimentally, both in terms of absolute value and effect of initial temperature. The comprehensive model predictions provide valuable insights, enabling differentiation among various UFL datasets for benzene. [ABSTRACT FROM AUTHOR]