Effective Use of Storage/Retrieval-Based Chemistry Acceleration in CFD

Database for On–Line Function Approximation (DOLFA) is a storage/retrieval chemistry–acceleration scheme that is based on Pope’s ISAT method [S.B. Pope Combust. Theory Modell. 1:41-63, 1997]. Recent developments in DOLFA are reviewed and the effective usage of DOLFA in multidimensional in-cylinder CFD is discussed. Highly nonhomogeneous systems with direct in-cylinder liquid fuel injection are considered, and results with and without a Lagrangian particle probability density function (PDF) method are presented. Numerical experiments show that all three approximations (linear, constant, and hybrid) yield global in–cylinder pressure, temperature, and species profiles that are in good agreement with those obtained using direct integration for an absolute error tolerance of 10−3. A smaller tolerance is required if one requires, for example, that the maximum cell-level mean temperature be within 50 K (say) of that obtained using direct integration. In addition to the error tolerance, scale factors also affect computational efficiency and accuracy. The benefits of DOLFA are greater in cases where the particle PDF method is used.