Unsteady RANS Simulations with Uncertainty Quantification of Spray Combustor Under Liquid Rocket Engine Relevant Conditions

Cavalieri, Davide; Liberatori, Jacopo; Galassi, Riccardo Malpica; Remiddi, Arianna; Valorani, Mauro; Ciottoli, Pietro Paolo

doi:10.2514/6.2023-2148

Cited by 7 publications

(4 citation statements)

References 27 publications

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“…In other words, we consider the droplet to be a lumped sphere that reaches a uniform constant temperature profile throughout its volume infinitely fast, still varying with time. Although the reported set of assumptions may appear simplistic, such models are used even in recent years in most real-world applications, including CFD codes, both in unsteady Reynolds-averaged Navier-Stokes (uRANS) Fossi et al (2015); Cavalieri et al (2023); Lucchese et al (2024) and large eddy simulations (LES) Esclapez et al (2017); Noh et al (2018); Domingo-Alvarez et al (2020); Benajes et al (2022) approaches, and even in direct numerical simulations (DNS) studies Ciottoli et al (2020); Wang et al (2021); Concetti et al (2023); Liberatori et al (2024).…”

Section: Droplet Evaporation Modelmentioning

confidence: 99%

“…Here, α is the weighting parameter between the droplet surface and the surrounding conditions. As suggested by Hubbard et alHubbard et al (1975) and Yuen and Chen Yuen and Chen (1976), we use the so-called "1/3 law" (α = 1/3), which is widely used in a large number of works dealing with droplet vaporization phenomena Abramzon and Sirignano (1989); Miller et al (1998); Daïf et al (1998); Aggarwal and Mongia (2002); Ebrahimian and Habchi (2011); Both et al (2022), and spray combustion simulations Jenny et al (2012); Cavalieri et al (2023); Lucchese et al (2024). The following sections provide details on the thermodynamic and transport models used.…”

Section: Droplet Evaporation Modelmentioning

confidence: 99%

See 1 more Smart Citation

Evaluation of non-ideal fluid modeling for droplet evaporation in jet-engine-like conditions

Cavalieri,

Liberatori,

Blandino

et al. 2024

Preprint

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Mid-century climate neutrality targets for the aviation industry foster the development of ultra-high overall pressure ratio jet engines. Consequently, comprehensive numerical models driving the design process must tackle the severe thermodynamic conditions expected to occur during the various flight operational phases. In the current study, we present a cost-effective framework for addressing droplet vaporization phenomena in jet-engine-relevant conditions, leveraging real-fluid thermophysical modeling and high-pressure vapor-liquid equilibrium interfacial thermodynamics. We evaluate the impact of a non-ideal fluid approach on predicting the evaporation process of a single n-dodecane droplet in air, mimicking operating conditions relevant to aero-engines. For the conditions examined, the numerical results indicate that adopting a real-fluid thermodynamic treatment results in a deviation of the droplet vaporization rate from an ideal-fluid approach, for which we have outlined the thermodynamic states that lead to mixture non-ideality. Notably, we envisage the most impactful model discrepancies in transport property estimation, thus affecting the heat and mass transfer rates. Lastly, we analyze and quantify the role of the detailed phase equilibrium model in the droplet evaporation process, assessing its actual impact for the conditions of interest, and discussing the cost-effectiveness in commonly computational fluid dynamics tools.

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Section: Droplet Evaporation Modelmentioning

confidence: 99%

Section: Droplet Evaporation Modelmentioning

confidence: 99%

Evaluation of non-ideal fluid modeling for droplet evaporation in jet-engine-like conditions

Cavalieri,

Liberatori,

Blandino

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

“…[20][21][22][23] Once the PDFs are known, the submodel uncertainty may be propagated to the QoIs through low-fidelity RANS simulations, employing a polynomial chaos expansion (PCE) representation of the random variables (RVs) being involved to reduce the number of required simulations. [24][25][26][27][28] This way, CFD results become supported by reliability measures, such as error bars or confidence intervals, similar to the usually adopted representations of experimental results. Moreover, the derivation of a surrogate model in terms of a PCE naturally offers the opportunity to assess the sensitivity of the output variance to each uncertain parameter, e.g., in terms of the so-called Sobol indices.…”

Section: Introductionmentioning

confidence: 98%

Uncertainty quantification analysis of Reynolds-averaged Navier–Stokes simulation of spray swirling jets undergoing vortex breakdown

Liberatori

Galassi

Valorani

et al. 2023

International Journal of Spray and Combustion Dynamics

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The computational fluid dynamics-based design of next-generation aeronautical combustion chambers is challenging due to many geometrical and operational parameters to be optimized and several sources of uncertainty that arise from numerical modeling. The present work highlights the potential benefits of exploiting Bayesian uncertainty quantification at the preliminary design stage. A prototypical configuration of an acetone/air spray swirling jet is investigated through an Eulerian–Lagrangian method under non-reactive conditions. Two direct numerical simulations (DNSs) provide reference data, coping with different vortex breakdown states. Consequently, a set of Reynolds-averaged Navier–Stokes simulations is conducted. Polynomial chaos expansion (PCE) is adopted to propagate the uncertainty associated with the spray dispersion model and the turbulent Schmidt number, delivering confidence intervals and the sensitivity of the output variance to each uncertain input. Consequently, the most significant sources of modeling uncertainty may be identified and eventually removed via a calibration procedure, thus making it possible to carry out a combustion chamber optimization process that is no longer affected by numerical biases. The uncertainty quantification analysis in the current study demonstrates that the spray dispersion model slightly affects the fuel vapor spatial distribution under vortex breakdown flow conditions, compared with the output variance induced by the selection of the turbulent Schmidt number. As a result, additional high-fidelity experimental and numerical campaigns should exclusively address the development of an ad hoc model characterizing the spatial distribution of the latter in the presence of vortex breakdown phenomenology, discarding any effort to improve the spray dispersion formulation.

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“…With respect to the latter, Bayesian calibration techniques MacKay (2005) can be employed to statistically characterize the uncertainty sources which affect the sub-models embedded into the lower-fidelity approaches, i.e., LES and RANS, addressing liquid phase behavior in multiphase reacting flows, e.g., droplet dispersion. In this regard, the impact of spray sub-models' uncertain parameters on the major observables can be assessed through nonintrusive spectral projection techniques Ciottoli et al (2020b); Liberatori et al (2021); Cavalieri et al (2023); Liberatori et al (2023), thus returning an overview of those model uncertainties that require further investigation through high-fidelity campaigns.…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of Vortex Breakdown in Evaporating Dilute Sprays

Liberatori

Battista

Barba

et al. 2023

Preprint

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The effects of different vortex breakdown states on the evaporation process characterizing air-acetone vapor swirling jets laden with liquid acetone droplets in the dilute regime are discussed based on results provided by direct numerical simulations. Adopting the point-droplet approximation, the carrier phase is solved using an Eulerian framework, whereas a Lagrangian tracking of the dispersed phase is used. Three test cases are investigated: one with fully-turbulent pipe inflow conditions and two with a laminar Maxworthy velocity profile at different swirl rates. Consequently, turbulent, bubble-type and regular conical vortex breakdown states are established. Following phenomenological and statistical analyses of both phases, a significant enhancement of the overall droplet evaporation process due to the onset of the conical vortex breakdown is observed due to the strongest centrifugal forces driving the entire liquid drops towards the low-saturation mixing layer of the jet. The effects of droplet inertia on evaporation are isolated through an additional set of simulations where liquid droplets are treated as Lagrangian tracers. While it is found that inertial effects contribute to enhanced vaporization near the mixing layer under bubble vortex breakdown conditions, droplet inertia plays a secondary role under both turbulent and conical vortex breakdown due to intense turbulent mixing and high centrifugal forces, respectively.

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Unsteady RANS Simulations with Uncertainty Quantification of Spray Combustor Under Liquid Rocket Engine Relevant Conditions

Cited by 7 publications

References 27 publications

Evaluation of non-ideal fluid modeling for droplet evaporation in jet-engine-like conditions

Evaluation of non-ideal fluid modeling for droplet evaporation in jet-engine-like conditions

Uncertainty quantification analysis of Reynolds-averaged Navier–Stokes simulation of spray swirling jets undergoing vortex breakdown

Direct numerical simulation of Vortex Breakdown in Evaporating Dilute Sprays

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