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Assessment of Deterministic Shape Optimizations Within a Stochastic Framework for Supersonic Organic Rankine Cycle Nozzle Cascades

Alessandro Romei 1 Pietro Marco Congedo 2 Giacomo Persico 1
2 DeFI - Shape reconstruction and identification
Inria Saclay - Ile de France, CMAP - Centre de Mathématiques Appliquées - Ecole Polytechnique
Abstract : The design of converging–diverging blades for organic Rankine cycle (ORC) applications widely relies on automated shape-optimization processes. As a result, the optimization produces an adapted-nozzle cascade at the design conditions. However, only few works account for the uncertainties in those conditions and their consequences on cascade performance. The proposed solution, i.e., including uncertainties within the optimization routine, demands an overall huge computational cost to estimate the target output statistic at each iteration of the optimization algorithm. With the aim of understanding if this computational cost is avoidable, we study the impact of uncertainties in the design conditions on the robustness of deterministically optimized profiles. Several optimized blades, obtained with different objective functions, constraints, and design variables, are considered in the present numerical analysis, which features a turbulent compressible flow solver and a state-of-the-art uncertainty-quantification (UQ) method. By including measured field variations in the formulation of the UQ problem, we show that a deterministic shape optimization already improves the robustness of the profile with respect to the baseline configuration. Guidelines about objective functions and blade parametrizations for deterministic optimizations are also provided. Finally, a novel methodology to estimate the mass-flow-rate probability density function (PDF) for choked supersonic turbines is proposed, along with a robust reformulation of the constraint problem without increasing the computational cost.
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https://hal.inria.fr/hal-03071659
Contributor : Pietro Marco Congedo Connect in order to contact the contributor
Submitted on : Wednesday, December 16, 2020 - 10:04:36 AM
Last modification on : Wednesday, August 18, 2021 - 11:39:36 AM
Long-term archiving on: : Wednesday, March 17, 2021 - 6:34:14 PM

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Alessandro Romei, Pietro Marco Congedo, Giacomo Persico. Assessment of Deterministic Shape Optimizations Within a Stochastic Framework for Supersonic Organic Rankine Cycle Nozzle Cascades. Journal of Engineering for Gas Turbines and Power, American Society of Mechanical Engineers, 2019, 141 (7), ⟨10.1115/1.4042925⟩. ⟨hal-03071659⟩

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