Simulation of real gas effects in supersonic methane jets using a tabulated equation of state with a discontinuous Galerkin spectral element method

• Published in: Computers & fluids 2017-03, Vol.145, p.167-179
• Main Authors: Hempert, F., Boblest, S., Ertl, T., Sadlo, F., Offenhäuser, P., Glass, C.W., Hoffmann, M., Beck, A., Munz, C.-D., Iben, U.
• Format: Article
• Language: English
• Subjects: Computational fluid dynamics; Computer simulation; Discontinuous Galerkin; Galerkin method; General equation of state; Ideal gas; Injectors; Internal combustion engines; Jets; Mass flow; Methane; Natural gas; Navier–Stokes equations; Phase transitions; Self-similarity; Shocks; Spectral element method; Supersonic jet
• ISSN: 0045-7930; 1879-0747
• DOI: 10.1016/j.compfluid.2016.12.024

•Coupling of a high order discontinuous Galerkin method with a tabulated multiparameter equation of state.•Large-Eddy simulation of high pressure supersonic real gas jets with a dense gas approach.•Demonstration of strong influence of real gas effects for high pressure supersonic jets. Modern direct gas injectors for natural-gas-powered internal combustion engines operate at ever-increasing pressures to maximize efficiency. At the operating point of current devices, real gas effects already become relevant, for example in the determination of mass flow rates. These effects have to be considered in the design process of such components. Motivated by this fact, we investigate the real gas effects of high-pressure supersonic methane jets. A discontinuous Galerkin spectral element method for computational fluid dynamics is used in combination with a tabulated equation of state for methane. We first evaluate self-similar profiles for subsonic jets to validate our simulation approach. Then we discuss our simulations of a supersonic jet, where we observe well-resolved shocks and transient structures. Additionally, real and ideal gas modeling are compared and we discuss the significant differences in general flow structure as well as density, pressure and mass flow that occur and make an ideal-gas description inappropriate for our simulation. The influence of pressure level and temperature on the behavior of the jet is discussed. We analyze the influence of the thermodynamic and viscous properties of the gas for the shock location and mass flow. The use of a tabulated equation of state makes jet simulations with occurring phase changes possible.