Computational fluid dynamics modeling of hydrogen ignition in a rapid compression machine

In modeling a rapid compression machine (RCM) experiment, a zero-dimensional code is commonly used along with an associated heat loss model. However, the applicability of such a zero-dimensional modeling needs to be assessed over a range of accessible experimental conditions. It is expected that when there exists significant influence of the multidimensional effects, including boundary layer, vortex roll-up, and nonuniform heat release, the zero-dimensional modeling may not be adequate. In this work, we simulate ignition of hydrogen in an RCM by employing computational fluid dynamics (CFD) studies with detailed chemistry. Through the comparison of CFD simulations with zero-dimensional results, the validity of a zero-dimensional modeling for simulating RCM experiments is assessed. Results show that the zero-dimensional modeling based on the approach of “adiabatic volume expansion” generally performs very well in adequately predicting the ignition delay of hydrogen, especially when a well-defined homogeneous core is retained within an RCM. As expected, the performance of this zero-dimensional modeling deteriorates with increasing temperature nonuniformity within the reaction chamber. Implications for the species sampling experiments in an RCM are further discussed. Proper interpretation of the measured species concentrations is emphasized and the validity of simulating RCM species sampling results with a zero-dimensional model is assessed.