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Soot Processes and Radiation in Aeronautical inNOvative combustors

Periodic Reporting for period 2 - SOPRANO (Soot Processes and Radiation in Aeronautical inNOvative combustors)

Reporting period: 2018-03-01 to 2019-08-31

SOPRANO aims at developing clean and efficient combustion technologies for aircraft engines to low-medium TRL, able to satisfy simultaneously the following challenges:
-Meet the ambitious ACARE NOx and CO2 objectives,
-Enhance the combustor’s liner durability,
-Control the emitted PM in terms of mass, number and morphology.
This can be broken down into the following scientific and industrial objectives.
The SOPRANO project’s 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 of SOPRANO 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 in the three SOPRANO technical work packages:

WP2: Validated tools for accurate soot PSD prediction
•Soot experiments:
-DLR has improved the fuel imaging technique implemented in its generic combustor at increased pressure by using acetone seeding into ethylene.
-DLR also conducted a detailed characterization of oxidation of soot particles of different sizes generated from ethylene flames by combining SMPS and MBMS.
-KIT has commissioned an RQL model combustor operating with kerosene in collaboration with MTU and performed 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 is working on a sectional model for soot PSD dynamics, using a transport 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 is introducing the DLR soot oxidation scheme into their used soot model already implemented in OpenFoam. This model framework has successfully been applied to the DLR benchmark 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 introduced aggregation into their soot model.
-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 is studding the impact of soot in the radiative power of an ethylene-air diffusion flame.
-RRD and RR-UK performed LES calculations using the RR in-house code PRECISE-UNS under a wide variation of the implemented chemistry and soot sub-models.

WP3: Reliable cooling design for durable combustors
•Aero-thermal measurements:
-ONERA is setting 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 is also performing 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.
-Another multiphysics tool, OPEN-PALM, is used in LES by EM2C to focus on the soot radiative effects within the DLR generic combustor.

WP4: Innovative Applications
•Semi-industrial combustor measurements:
-The setup of the high-pressure combustion chamber (MICADO) at ONERA is finished.
-At the same time, DLR launched two experimental campaigns with laser shadowgraphy.
•Semi-industrial combustor modelling:
-Loughborough University 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.
-SAFRAN has performed the reactive LES computation of the MICADO test rig.
-Rolls-Royce applied the baseline two-equation as well as new soot models from DLR in LES in their in-house Intermediate Pressure Rig.
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 total 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 could strongly impact program outcomes.
The strong interaction between experimentalists, academic and industrial soot and cooling modelling, practiced in the different benchmark comparisons, shall also provide input to even more international benchmark approaches during this and next year’s scientific events, and thereby (a) enhance the visibility of the SOPRANO project and (b) exploit the detailed understanding of soot formation (modelling and experimental data) by collaboration with the international research community. The concerted presence of SOPRANO-based contributions on recent conferences has already been acknowledged by the scientific community and will even enhance during the upcoming International Sooting Flame workshop (ISF5) and the International Combustion Symposium.