A passive scalar-based method for numerical combustion

• A passive scalar-based method is proposed for analyzing unsteady combustion.
• Passive scalars are utilized to trace mass transport in numerical combustion.
• Large eddy simulation is executed for cavity-stabilized supersonic combustion.
• Cavity residence time is obtained for the first time under reacting conditions.

A passive scalar-based method for analyzing unsteady combustion processes has been proposed. Transport equations for passive scalars have been derived based on mixture fraction concept widely used for the description of nonpremixed combustion. These equations can be solved together with the conventional computational fluid dynamics (CFD) governing equations so that these passive scalars are readily utilized to trace the mass transport in simulations of complicated reacting flows, regardless of turbulence and chemistry models. The approach is used together with large eddy simulation to study the cavity-stabilized H2 jet combustion in a supersonic combustor, where characteristics of the mass transfer into and out of the cavity are captured and cavity residence time is obtained for the first time under reacting flow conditions.