Browsing by Author "Valencia, Esteban"

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    Discretized Miller approach to assess effects on boundary layer ingestion induced distortion
    (Elsevier, 2016-12-21) Valencia, Esteban; Hidalgo, Víctor; Nalianda, Devaiah; Laskaridis, Panagiotis; Singh, R.
    The performance of propulsion configurations with boundary layer ingestion (BLI) is affected to a large extent by the level of distortion in the inlet flow field. Through flow methods and parallel compressor have been used in the past to calculate the effects of this aerodynamic integration issue on the fan performance; however high-fidelity through flow methods are computationally expensive, which limits their use at preliminary design stage. On the other hand, parallel compressor has been developed to assess only circumferential distortion. This paper introduces a discretized semi-empirical performance method, which uses empirical correlations for blade and performance calculations. This tool discretizes the inlet region in radial and circumferential directions enabling the assessment of deterioration in fan performance caused by the combined effect of both distortion patterns. This paper initially studies the accuracy and suitability of the semi-empirical discretized method by comparing its predictions with CFD and experimental data for a baseline case working under distorted and undistorted conditions. Then a test case is examined, which corresponds to the propulsor fan of a distributed propulsion system with BLI. The results obtained from the validation study show a good agreement with the experimental and CFD results under design point conditions.
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    Methodology for the assessment of distributed propulsion configurations with boundary layer ingestion using the discretized miller approach
    (Praise Worthy Prize, 2017-06-30) Valencia, Esteban; Liu, Chengyuan; Nalianda, Devaiah; Panagiotis, Laskaridis; Gray, Iain; Singh, Riti
    The growing global environmental awareness has motivated the search for more fuel-efficient aircraft propulsion systems. In this context, a configuration based on distributed propulsion with Boundary Layer Ingestion (BLI) has been found to present potential performance benefits. The concept has been documented and explored extensively during the last few years and various aerodynamic integration issues, such as: high levels of distortion and low intake pressure recovery; have been identified as factors that may be detrimental in realizing the technology full potential. Parametric and parallel compressor (PC) approaches have been used to assess the effect of these aerodynamic issues on propulsors fan performance. However, in the context of BLI, these tools are unable to assess the effects of combined radial and circumferential distortion that are present. In order to assess the combined distortion patterns and the effects of distortion at component and system levels, this study uses a novel method based on semi-empirical correlations denominated the Discretized Miller (DM) approach. This method was developed for BLI systems previously by the author, and it is now incorporated into the propulsor performance method to assess the effects of the combined radial and circumferential distortion patterns. The performance analysis, undertaken at a component and system level, aims to assess several propulsion architectures, using Thrust Specific Fuel Consumption (TSFC) as figure of merit. To define the suitability of the distributed propulsor array in this study, an airframe layout based on the N3-X aircraft concept and High Temperature Superconducting (HTS) electric motor capabilities were assumed. The key contribution of this study is to enable the introduction of the concept of thrust split between energy source and propulsion system in the system analysis, and thereby, allows the assessment of its effects on different propulsion system layouts, while considering the BLI induced distortion. The results obtained with this alternative performance method showed that BLI reduces the fan efficiency of a conventional fan by approximately 2%, whilst corroborating the TSFC trends observed in previous studies. The study also indicates that when sizing effects of propulsors and core-engines were neglected, a propulsion system configuration with 75% thrust split was found optimum.
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    Novel fan configuration for distributed propulsion systems with boundary layer ingestion on an hybrid wing body airframe
    (Elsevier, 2020-02-28) Valencia, Esteban; Alulema, Victor; Rodriguez, Dario; Laskaridis, Panagiotis; Roumeliotis, Ioannis
    The performance benefits of directly ingesting the boundary layer (BLI) on air vehicles with distributed propulsion (DP) systems has been documented and explored extensively. However, numerous investigations have demonstrated that the increase of the flow distortion in the inlets of conventional propulsors can dramatically reduce the expected benefits. Hence, this work presents an alternative fan configuration to re-energize the boundary layer, and at the same time, to perform properly in a distorted and non-uniform flow-field. This conceptual design utilizes a two-dimension idealized fan and replaces the rotational movement with linear displacement, avoiding the undesired effects of circumferential distortion on the propulsor operation. A quasi two-dimensional model based on the Discretized Miller approach has been used to compare the proposed configuration with a conventional axial fan. From the results obtained, it is observed that the thermal performance of the fan is less affected for the proposed configuration and furthermore, intake pressure losses are ameliorated by the use of a single mailbox shape inlet. The performance assessment of the proposed configuration coupled on the N3-X aircraft shows benefits of 4% in fuel savings compared with current BLI turbo-machinery configurations. The main contribution of this study lies on the definition of a preliminary design for an alternative propulsor configuration able to deal with circumferential distortion.