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Modeling and Simulation of Lean Blowout in High-Pressure Swirl-Stabilized Combustors

Description:

TECHNOLOGY AREA(S): Air Platform

OBJECTIVE: Develop new physics-based turbulent combustion models for predicting the onset of lean blowout in propulsion systems operating at Air Force relevant conditions including high pressures, high-speed compressible flows, and high turbulence intensities.

DESCRIPTION: Many existing modeling and simulation approaches have been developed for and applied to turbulent combustion systems operating at steady-state under ideal laboratory conditions. The laboratory conditions typically include atmospheric pressures, low speed incompressible flows (i.e., low Mach numbers), low turbulence intensities (i.e., low Reynolds numbers), and gaseous fuels. Current and next-generation Air Force combustion systems operate with high pressures, high-speed compressible flows (i.e., high Mach numbers), high turbulence intensities (i.e., high Reynolds numbers), and multi-component liquid fuels. Large eddy simulations (LES) and turbulent combustion models [1-2] for these more relevant operating conditions require the development of new physics-based models or significant improvements to existing models such as the flamelet progress variable (FPV) [3], linear eddy model (LEM) [4], or transported probability density function (PDF) [5] approaches.

Significant attention should be focused on evaluating and quantifying the effects of model assumptions at both the resolved scales and unresolved subgrid scales (SGS). Specific model assumptions that should be evaluated include but are not limited to the following: low Mach numbers, constant pressures, presumed PDF closures, presumed scalar mixing closures, a prior tabulated chemical kinetics, preferential diffusion, and consistency with the direct numerical simulation (DNS) limit. The models must be applicable to pre-mixed, non-pre-mixed, and partially pre-mixed combustion regimes. The models must be capable of predicting the onset of lean blowout at operating conditions relevant to Air Force propulsion systems including pressures from 10-30 atm and temperatures from 2200 to 3500 degrees F. The LES results must be evaluated using relevant experimental data such as those being acquired at the Air Force Research Laboratory Aerospace Systems Directorate Turbine Engine Division.

The models must be made modular by specifying standardized application programming interfaces (APIs) which enable the models to be utilized as libraries in turbulent reacting flow codes relevant to Air Force and original engine manufacturer (OEM) applications of interest. The interfaces must be independent of code-specific data structures in order to maintain generality. The availability of conventional LES models and finite-rate chemical kinetics can be assumed to exist in the reacting flow codes, but all other aspects of the turbulent combustion models must be enabled through the new modules.

PHASE I: Evaluate the effects of turbulent combustion model assumptions on the simulation results for the intended operating conditions and combustion regimes. Demonstrate the potential of the turbulent combustion models for statistically stationary turbulent combustion systems. Develop prototype APIs with standardized interfaces that are well-documented.

PHASE II: Further develop and improve the turbulent combustion models with particular emphasis on predicting the onset of lean blowout. Perform detailed verification and validation by using experimental data sets such as those being acquired at the Air Force Research Laboratory Aerospace Systems Directorate Turbine Engine Division. Demonstrate the models as APIs in turbulent reacting flow codes relevant to the Air Force and OEMs.

PHASE III DUAL USE APPLICATIONS: Turbulent combustion processes are highly relevant to the performance of military propulsion systems such as gas turbine engines, augmentors, rockets, and scramjets and non-military power and propulsion systems such as aircraft engines, automotive engines, and land-based power generation devices.

REFERENCES:

    • Pope, S.B., "Turbulent Flows," Cambridge University Press (2000).

 

    • Poinsot, T. and Veynante, D., "Theoretical and Numerical Combustion," R.T. Edwards (2005).

 

    • Pitsch, H., Desjardins, O., Balarac, G. and Ihme, M., "Large-Eddy Simulation of Turbulent Reacting Flows," Progress in Aerospace Sciences, Vol. 44, pp. 466-478 (2008).

 

    • Kerstein, A., "A Linear Eddy Model of Turbulent Scalar Transport and Mixing," Combustion Science and Technology, Vol. 60, pp. 391-421 (1988).

 

  • Pope, S.B., "Small Scales, Many Species and the Manifold Challenges of Turbulent Combustion," Proceedings of the Combustion Institute, Vol. 34, pp. 1-31 (2013).

KEYWORDS: modeling and simulation, large eddy simulations, turbulent combustion, reacting flows, lean blowout

  • TPOC-1: Brent Rankin
  • Phone: 937-255-9722
  • Email: brent.rankin.1@us.af.mil
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