Flamelet Model with Epsilon Tracking in a Turbine Stator

TL;DR

This paper introduces a novel flamelet model with epsilon tracking for simulating combustion in turbine stators, incorporating practical JP-5 fuel and detailed chemical mechanisms within a RANS framework.

Contribution

It develops an epsilon-based flamelet model linking turbulence and chemistry, enabling realistic simulation of JP-5 combustion in turbine passages.

Findings

The epsilon-based model predicts lower peak flame temperatures than one-step models.

Simulations show JP-5 combustion involves pyrolysis and oxidation, affecting temperature and reaction zones.

Model captures effects of strain rate and flame quenching on chemical energy release.

Abstract

Combustion within a two-dimensional turbine stator passage is numerically investigated in the context of the turbine-burner concept using a Reynolds-Averaged Navier-Stokes framework coupled with a novel flamelet model. The formulation links resolved-scale turbulence quantities with subgrid flamelet dynamics through the local turbulent kinetic energy dissipation rate, $\epsilon$, which determines the flamelet inflow strain rate. For the first time, combustion of JP-5 is considered in a turbine stator passage as a practical fuel. This is achieved by solving transport equations for 14 major species on the resolved scale, while chemical source terms are obtained from precomputed flamelet libraries based on the HyChem A3 mechanism comprising 119 species and 841 elementary reactions. Model performance is assessed against methane combustion using both a one-step kinetics model and an $\epsilon$-based flamelet formulation employing a 13-species skeletal mechanism. The $\epsilon$-based formulation predicts lower peak flame temperatures due to dissociation effects and approximately 50\% lower net chemical energy addition per unit mass compared with the one-step model, as a result of flame stand-off and downstream strain-rate-induced quenching. For JP-5, the simulations capture combined endothermic pyrolysis and exothermic oxidation processes, leading to vertically displaced reaction zones, increased near-wall temperatures, and larger resolved-scale reaction regions due to the higher flamelet flammability limit relative to methane.