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Guardone, Alberto (author), Colonna, Piero (author), Pini, M. (author), Spinelli, Andrea (author)The gas dynamics of single-phase nonreacting fluids whose thermodynamic states are close to vapor-liquid saturation, close to the vapor-liquid critical point, or in supercritical conditions differs quantitatively and qualitatively from the textbook gas dynamics of dilute, ideal gases. Due to nonideal fluid thermodynamic properties,...journal article 2024
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Tosto, F. (author), Wheeler, Andrew (author), Pini, M. (author)In this work, we present an investigation about the sources of dissipation in adiabatic boundary layers of non-ideal compressible fluid flows. Direct numerical simulations (DNS) of transitional, zero-pressure gradient boundary layer flows are performed for two fluids characterized by different complexity of the fluid molecules, namely, “air”...journal article 2024
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Giuffré, A. (author), Pini, M. (author)Non-ideal compressible flows exhibit physical behaviors that are quantitatively and qualitatively different than those of a perfect or ideal gas. As such, the classical gas dynamic relationships that can be found on fluid-mechanics textbooks cannot be directly applied to characterize this type of flows. NiceProp is a tool for interactively...journal article 2022
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Giuffré, A. (author), Colonna, Piero (author), Pini, M. (author)The impact of size and working fluid on the efficiency, operating range, and axial thrust on bearings is examined for high-speed, oil-free centrifugal compressors. First, the development and validation of a reduced-order model based on scaling principles is documented. Then, the validated compressor model is used to generate design maps for...journal article 2022
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Agromayor, Roberto (author), Anand, N. (author), Pini, M. (author), O. Nord, Lars (author)Currently, most of the adjoint-based design systems documented in the open literature assume that the fluid behaves as an ideal gas, are restricted to the optimization of a single row of blades, or are not suited to impose geometric constraints. In response to these limitations, this paper presents a gradient-based shape optimization framework...journal article 2022
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Scaccabarozzi, R. (author), Martelli, Emanuele (author), Pini, M. (author), de Servi, C.M. (author), Chiesa, Paolo (author), Gatti, Manuele (author)This paper documents a thermo-fluid-dynamic mean-line model for the preliminary design of multistage axial turbines with blade cooling applicable to supercritical CO<sub>2</sub> turbines. Given the working fluid and coolant inlet thermodynamic conditions, blade geometry, number of stages and load criterion, the model computes the stage-by...journal article 2022
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Tosto, F. (author), Giuffré, A. (author), Colonna, Piero (author), Pini, M. (author)In this work we examine the flow deviation and its relationship to critical choking, i.e., choking of the meridional component of velocity, in transonic turbine cascades operating with non-ideal compressible flows. To this purpose, a generalized expression of the corrected flow per unit area as a function of both the thermodynamic state and...journal article 2022
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Leverone, F.K. (author), Cervone, A. (author), Pini, M. (author), Gill, E.K.A. (author)Small satellites with increased capabilities in terms of power and propulsion are being demanded for future missions. This paper addresses an alternative bi-modal solution which consists of a solar thermal propulsion system coupled with a micro-Organic Rankine Cycle system, to co-generate thrust and electrical power. Current literature on bi...journal article 2021
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Giuffré, A. (author), Pini, M. (author)The impact of non-ideal compressible flows on the fluid-dynamic design of axial turbine stages is examined. First, the classical similarity equation (CSE) is revised and extended to account for the effect of flow non-ideality. Then, the influence of the most relevant design parameters is investigated through the application of a dimensionless...journal article 2021
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Tosto, F. (author), Lettieri, C. (author), Pini, M. (author), Colonna, Piero (author)Paradigmatic compressible one-dimensional flows provide insights regarding the loss mechanisms of fluid machinery components typical of power and propulsion systems, like turbomachines and heat exchangers. Their performance also depends on the working fluid, thus, on both molecular complexity and thermodynamic state. Four typical flow...journal article 2021
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Rubino, A. (author), Colonna, Piero (author), Pini, M. (author)The lack of established optimal design guidelines for turbomachinery operating in the nonideal flow regime (e.g., organic Rankine cycle turbines, CO<sub>2</sub> compressors, compressors for refrigeration systems) demands for effective and efficient automated design methods. Past research work focused on gradient-free methods applied to...journal article 2021
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Agromayor, Roberto (author), Anand, N. (author), Müller, Jens Dominik (author), Pini, M. (author), Nord, Lars O. (author)Turbomachinery design is increasingly carried out by means of automated workflows based on high-fidelity physical models and optimization algorithms. The parametrization of the blade geometry is an essential aspect of such workflows because it defines the design space in which an optimal solution can be found. Currently, parametrization...journal article 2021
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Rubino, A. (author), Vitale, S. (author), Colonna, Piero (author), Pini, M. (author)The possibility of taking into account unsteady flow effects if performing turbomachinery shape optimization is attractive to accurately address inherently time dependent design problems. The harmonic balance method is an efficient solution for computational fluid dynamics problems of turbomachinery characterized by quasi-periodic flows. If...journal article 2020
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Leverone, F.K. (author), Pini, M. (author), Cervone, A. (author), Gill, E.K.A. (author)Small satellites are receiving increased recognition in the space domain due to their reduced associated launch costs and shorter lead time when compared to larger satellites. However, this advantage is often at the expense of mission capabilities, such as available electrical power and propulsion. A possible solution is to shift from the...journal article 2020
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Pini, M. (author), Azzini, L. (author), Vitale, S. (author), Colonna, Piero (author)This paper presents a fully turbulent two-phase discrete adjoint method for metastable condensing flows targeted to turbomachinery applications. The method is based on a duality preserving algorithm and implemented in the open-source CFD tool SU2. The optimization framework is applied to the shape optimization of two canonical steam turbine...journal article 2020
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Anand, N. (author), Colonna, Piero (author), Pini, M. (author)Supersonic stator vanes account for two-thirds of the fluid-dynamic losses in high temperature mini-Organic Rankine Cycle (ORC) turbines. As a result, the overall performance of the turbo-expander mainly depends on the design of the stator. Currently, there is no established correlation for the optimal design of such cascades. This work...journal article 2020
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Vitale, S. (author), Pini, M. (author), Colonna, Piero (author)This paper documents a fully turbulent discrete ad joint method for three-dimensional multistage turbomachinery design. The method is based on a duality preserving algorithm and is implemented in the open-source computational fluid dynamics tool SU2. The SU2 Reynolds-averaged Navier–Stokes solver is first extended to treat three dimensional...journal article 2020
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de Servi, C.M. (author), Burigana, M. (author), Pini, M. (author), Colonna, Piero (author)The realization of commercial mini organic Rankine cycle (ORC) power systems (tens of kW of power output) is currently pursued by means of various research and development activities. The application driving most of the efforts is the waste heat recovery from long-haul truck engines. Obtaining an efficient mini radial inflow turbine, arguably...journal article 2019
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Bahamonde, Juan S. (author), Pini, M. (author), de Servi, C.M. (author), Schiffmann, Jürg (author), Colonna, Piero (author)By means of this corrigendum, the authors would like to include relevant information regarding the validation of the meanline turbine model employed in the original article. The improvement regarding the validation of the model was made possible thanks to the contribution of Prof. Jürg Schiffmann. The additional results documented here...journal article 2019
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Rubino, A. (author), Pini, M. (author), Kosec, M. (author), Vitale, S. (author), Colonna, Piero (author)Fast and accurate computation of thermo-physical properties is essential in computationally expensive simulations involving fluid flows that significantly depart from the ideal gas or ideal liquid behavior. A look-up table algorithm based on unstructured grids is proposed and applied to non-ideal compressible fluid dynamics simulations. The...journal article 2018
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