Supercritical and Transcritical Real-Fluid Mixing in Diesel Engine Applications

Report No. ARL-RP-0551
Authors: PC Ma; L Bravo; M Ihme
Date/Pages: September 2015; 16 pages
Abstract: A numerical framework for simulating the mixing of supercritical and transcritical fuids with large density ratios is presented. The accurate and robust modeling of real-fluid effects on the fuel/air mixing process is critical in characterizing engine combustion. To describe this mixing process, the double-flux model is extended to systems with real-fluid state equations. For this, an effective specific heat ratio is introduced to eliminate the spurious pressure oscillations that are caused by the nonlinearity of the real-fluid equation of state. High-order WENO spatial discretization scheme is used for the real-fluid flow calculations to account for the large density gradients associated with these flows. One-dimensional single and multicomponent advection test cases and two-dimensional supercritical nitrogen jet mixing and transcritical n-dodecane injection test cases are conducted to show the capability of the present study in application to real-fluid supercritical and transcritical flows. Energy conservation errors, generated due to the double-flux formulation, are acceptable.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2015