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Soot Processes and Radiation in Aeronautical inNOvative combustors

Periodic Reporting for period 3 - SOPRANO (Soot Processes and Radiation in Aeronautical inNOvative combustors)

Reporting period: 2019-09-01 to 2021-02-28

The SOPRANO initiative will contribute to the development of advanced methods and models dedicated to the detailed comprehension of soot particles formation and oxidation and their impact on heat transfer through radiation effects.
This can be broken down into the following scientific and industrial objectives:
-The main scientific objective is to make a breakthrough in the overall investigation efforts in the field of soot particles chemistry, particles size distribution (PSD), and their radiative effect on combustors typical of aero-engines. SOPRANO aims at a qualitative shift in the knowledge related to the characterization and -prediction of soot emission.
-The main industrial objective is to carry out an in-depth characterization of soot particles emitted by a modern combustor at engine-relevant operating conditions and at increased pressures to pave the way for the future design of high-performance combustors: a more accurate evaluation of the radiation effect and, therefore, a more reliable liner temperature prediction, will drive a review of the design criteria in terms of combustor air distribution and will improve durability of some key modules.
The following main achievements were made during the project:

WP2: Validated tools for accurate soot PSD prediction
•Soot experiments:
-DLR has determined wall temperatures (boundary conditions), first employed acetone PLIF for monitoring fuel distribution at pressure and first demonstrated coupled CARS and LII for in-flame particle sizing, and conducted detailed characterizations of soot particle oxidation for different particle sizes generated from ethylene flames by combined SMPS/MBMS.
-KIT has commissioned a kerosene RQL model combustor in collaboration with MTU and performed detailed measurements.
-INSA has commissioned and set up a burner for characterization of stratified flames at increased pressure. In parallel, diagnostics for detailed characterization of soot particles has been developed. For derivation of temperatures, a novel CARS system employing femtosecond laser pulses was set up.
•Soot modelling:
-ICL has detailed a sectional model for soot PSD dynamics, using a transported PDF approach. Based on this soot model, RRUK performed LES computations of the DLR’s generic combustor, and tested two combustion models: FGM and CMC.
-ICL have successfully reduced the size of the used gas phase model without significantly impeding accuracy; similar has been achieved by INSA using their automated combustion chemistry reduction scheme ORCh.
-MTU has introduced the DLR soot oxidation scheme into their soot model already implemented in OpenFoam. This model framework has successfully been applied to the DLR benchmark and the KIT case.
-DLR has confirmed the advantages of including polyynes for soot growth into their soot model for a representation combining sectional PAH model with a global 2-equations soot mechanism. RRD applied this soot model to the DLR’s generic combustor. Moreover, DLR incorporated reversible PAH chemistry using PAH radicals into their sectional PAH sub-model, and extended the model for soot aggregation.
-DLR also performed LES computations of the DLR generic combustor with a lumped sectional model for both soot and PAH.
-Based on a 1D laminar premixed flame computation, INSA has developed a hybrid sectionoal/stochastic soot model.
-CERFACS has developed and validated a Lagrangian soot particle solver coupled to a reduced chemistry for gaseous soot precursors.
-The optimized in-house EM2C sectional model, extended to diffusion flames (HACA-RC*), has also been applied to the DLR generic configuration.
-EM2C has studied the impact of soot on radiative power of an ethylene-air diffusion flame.
-RR performed LES calculations using the RR in-house code PRECISE-UNS under a wide variation of implemented chemistry and soot sub-models.

WP3: Reliable cooling design for durable combustors
•Aero-thermal measurements:
-ONERA has set up an experimental database of a perforated plate with a side injection.
-UNIFI performed adiabatic effectiveness measurements by IR technique and adiabatic film effectiveness by PSP to the Five-Sector Warm Rig for a detailed test matrix.
-KIT focusses on the effects of effusion cooling on relight performances within the dedicated Altitude Rig.
•Aero-thermal modelling:
-CERFACS has improved the film model dedicated to predict primary spray atomization using PAMELA model in AVBP.
-LMAP has performed RANS simulations of the multiperforated plate facility at ONERA.
-GE AVIO and UNIFI settled up aero flow for using KIAI test rig spray flame as initial step for their ignition probability model validation using FLUENT.
-UNIFI is working on the U-THERM3D unsteady multiphysics tool, which involves in LES heat transfer fluxes as well as combustion chemistry.

WP4: Innovative Applications
•Semi-industrial combustor measurements:
-The setup of the high-pressure combustion chamber (MICADO) at ONERA was finished, detailed measurements with laser-based and conventional diagnostics were performed.
-DLR has performed two experimental campaigns characterizing superheated/supercritical fuel injection.
•Semi-industrial combustor modelling:
-LU performed RANS and LES computations, with the baseline two-equation soot model, on the simplified combustor geometry previously defined.
-GEDE successfully performed initial steady-state calculations (based on GEA design tools) of the MICADO facility.
-RR applied the baseline two-equation as well as new soot models from DLR in LES in their in-house Intermediate Pressure Rig.
-ONERA: Optical campaigns carried out on the MICADO experiment and transmission of the MICADO database for first experimental-numerical comparisons.
-SAFRAN: LES simulation of the MICADO test-case using the new LST soot modelling developed by CERFACS in the WP2.
-LU: Experimental evaluation of combustor operability and soot emissions and numerical predictions of Primary Zone air-fuel mixing .
-DLR & GEDE: Measurement campaigns focused on the quantitative spray characterization under extreme injection conditions.
-RRD & RRUK: Application of combustion, combustion chemistry-interaction and soot models to the engine environment.
-SNECMA: Applcation of the Lagrangian soot model developed in WP2 inside rich and lean industrial combustors under representative operating conditions.
The major impact of the work performed within SOPRANO so far is anticipated to provide benefits for climate-related effects of particulate formation and their emission. A first step into improvement of industrial codes including predictive soot modelling was already visible during the periodic project meetings; the effect of a variation of sub-models on industrial soot prediction based on academic research was presented. For the first time, industrial design tools are getting increasingly capable to predict particle size distributions, while previously only mass-integrated emissions were relevant. This enhances their capability to comply with future legislation incorporating emitted particle numbers. Similarly, the first results presented on both aerothermal and soot radiative effects are very promising and can strongly impact program outcomes. Conjugate heat transfer has been proven to be important for strongly sooting flames and affects pollutant formation and wall heat load, thus should be considered (where possible) for design of wall cooling.
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