1 / 8

Heat release modeling

Heat release modeling. FPVA-based model V. Terrapon and H. Pitsch. Why is turbulent combustion challenging?. QUALITATIVE. A large range of scales is involved!. Typical engineering application. 10 -9. 10 -6. 10 -3. 10 0. 10 3. [ m ] [ s ]. Reaction time scale. Chemistry.

elke
Download Presentation

Heat release modeling

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Heat release modeling FPVA-based model V. Terraponand H. Pitsch Stanford PSAAP Center - Working draft

  2. Why is turbulent combustion challenging? QUALITATIVE A large range of scales is involved! Typical engineering application 10-9 10-6 10-3 100 103 [m] [s] Reaction time scale Chemistry Reaction zone thickness Turbulent flow Integral length scale Kolmogorov length scale • Equations are very stiff • DNS is usually not possible (LES/RANS) Stanford PSAAP Center - Working draft

  3. Closure is required Source term is highly non-linear Decaying isotropic turbulence Average species transport equation: Average species transport equation simplifies: The source term: Species mass fraction Flamelets DNS with From mean quantities Diffusive and convective terms can usually be treated like for the NS equations From M. Ihme Stanford PSAAP Center - Working draft

  4. Tabulated chemistry as a potential solution Transformation and asymptotic approximation leads to equations for the flame micro-structure similar to the flamelet equations Steady diffusion flame solution for H2/air flame at χst =1 Diffusion flame regime Auto-ignition regime Mixture fraction Flame strain is measured by the scalar dissipation rate Zst Scale separation allows us to pre-compute and tabulate chemistry as function of Z and χ Stanford PSAAP Center - Working draft

  5. Combustion model for high-speed flows based on tabulated chemistry + - Assumptions Current combustion model • Species mass fractions independent of compressibility effects • Flame micro-structure • Based on FlameletProgress Variable Approach (FPVA)* • Tabulated chemistry • Temperature computed from species mass fractions and energy (not from chemistry table) • 3 additional transport equations for the mean and variance of the mixture fraction and for the progress variable Pros Cons • Complex chemistry mechanism • Only few additional scalars to solve • Turbulence – chemistry interaction • Compressibility effects on chemistry not accounted for • Accuracy of ignition dynamics * Pierce & Moin, 2004; Ihme et al., 2005 Stanford PSAAP Center - Working draft

  6. Model algorithm All other quantities Transported variables • EOS • Mixing rules NSE Temperature • Newton iteration • Not looked up from table Turbulence Tabulated chemistry Combustion • Table lookup • Pre-computed chemistry Chemistry does not account for compressibility effects and viscous heating Stanford PSAAP Center - Working draft

  7. Source term of progress variable C has a strong pressure dependence • Dynamics of flame strongly dependent on pressure • Quadratic dependence (mostly 2 body interactions) • Rescaling of source term for progress variable • Sc(P) = Sc(Pref) P2/P2ref Stanford PSAAP Center - Working draft

  8. Rescaled source term as function of the progress variable Z = Zst = 0.028 • Dynamics of flame strongly dependent on pressure • Quadratic dependence (mostly 2 body interactions) • Rescaling of source term for progress variable • Sc(P) = Sc(Pref) P2/P2ref P Stanford PSAAP Center - Working draft

More Related