Prediction of mean radical concentrations in lean hydrogen-air turbulent flames at different Karlovitz numbers adopting a newly extended flamelet-based presumed PDF
Artikel i vetenskaplig tidskrift, 2021

A recent analysis (Lipatnikov et al., 2020) of complex-chemistry direct numerical simulation (DNS) data obtained from lean hydrogen-air flames associated with corrugated-flame (case A), thin-reaction-zone (case B), and broken-reaction-zone (case C) regimes of turbulent burning has shown that the flamelet concept (i) can predict mean concentrations of various species in those flames if the probability density function (PDF) for the fuel-based combustion progress variable c is extracted from the DNS data, but (ii) poorly performs for the mean rate W¯c of product creation. These results suggest applying the concept to evaluation of mean species concentration (but not the mean rate) in combination with another closure relation for W¯c whose predictive capabilities are better. This proposal is developed in the present paper whose focus is placed on studying a new flamelet-based presumed PDF P(c) for predictions of mean concentration of radicals in engineering computational fluid dynamics (CFD) applications. Analysis of the DNS data shows that (i) the flamelet PDF performs well at intermediate values of c in cases A and B, but should be truncated at small and large c, (ii) modeling P(c) in the radical recombination zone (i.e., at large c) is of importance for predicting mean concentrations of H,O, and OH. Accordingly, the flamelet PDF is truncated and combined with a uniform P(c) at large c. Moreover, the mean rate W¯c extracted from the DNS data is used to calibrate the PDF (the rate is considered to be given by another model). Assessment of the approach against the DNS data shows that it well predicts mean density, temperature, and concentrations of reactants, product, and the aforementioned radicals in cases A and B. In case C, the approach performs worse for OandOH at large c¯ and moderately underestimates the mean concentration of H in the entire flame brush.

Premixed turbulent combustion

presumed pdf

modeling

radical concentrations

DNS

complex chemistry

Författare

Andrei Lipatnikov

Chalmers, Mekanik och maritima vetenskaper, Förbränning och framdrivningssystem, Förbränning och sprejer

Vladimir Sabelnikov

Central Aerohydrodynamic Institute (TsAGI)

Office national d'etudes et de recherches aerospatiales (ONERA)

Francesco Hernandez-Perez

King Abdullah University of Science and Technology (KAUST)

Wonsik Song

King Abdullah University of Science and Technology (KAUST)

Hong G. Im

King Abdullah University of Science and Technology (KAUST)

Combustion and Flame

0010-2180 (ISSN)

Vol. 226 248-259

Drivkrafter

Hållbar utveckling

Ämneskategorier

Energiteknik

Strömningsmekanik och akustik

Fundament

Grundläggande vetenskaper

DOI

10.1016/j.combustflame.2020.12.009

Mer information

Senast uppdaterat

2021-03-12