Browsing by Author "Piovesan, Tommaso"
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Item Open Access Aerodynamic optimization of the exhaust system of an aft-mounted boundary layer ingestion propulsor(Emerald, 2022-12-15) Matesanz García, Jesús; Piovesan, Tommaso; MacManus, David G.Purpose Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive system, higher levels of flow distortion at the fan face are expected. This distortion will propagate through the fan and penalize the system performance. This will also modify the exhaust design requirements. This paper aims to propose a methodology for the aerodynamic optimization of the exhaust for novel embedded propulsive systems. To model the distortion transfer, a low order throughflow fan model is included. Design/methodology/approach As the case study a 2D axisymmetric aft-mounted annular boundary layer ingestion (BLI) propulsor is used. An automated computational fluid dynamics approach is applied with a parametric definition of the design space. A throughflow body force model for the fan is implemented and validated for 2D axisymmetric and 3D flows. A multi-objective optimization based on evolutionary algorithms is used for the exhaust design. Findings By the application of the optimization methodology, a maximum benefit of approximately 0.32% of the total aircraft required thrust was observed by the application of compact exhaust designs. Furthermore, for the embedded system, it is observed that the design of the compact exhaust and the nacelle afterbody have a considerable impact on the aerodynamic performance. Originality/value This paper presents a novel approach for the exhaust design of embedded propulsive systems in novel aircraft configurations. To the best of the authors’ knowledge, this is the first detailed optimization of the exhaust system on an annular aft-mounted BLI propulsor.Item Open Access Aerodynamic optimization of the exhaust system of an aft-mounted boundary layer ingestion propulsor(2022-03-28) Matesanz García, Jesús; Piovesan, Tommaso; MacManus, David G.Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive system, higher levels of flow distortion at the fan face are expected. This distortion will propagate through the fan and penalize the system performance. This will also modify the exhaust design requirements. Hence, the aerodynamic design of the exhaust system becomes crucial to reduce the penalties of the distortion on the system performance. This work defines a methodology for the optimization of exhaust systems for novel embedded propulsive systems. As the case study a 2D axisymmetric aft mounted annular boundary layer ingestion (BLI) propulsor is used. An automated CFD approach is applied with a parametric definition of the design space. A throughflow body force model for the fan is implemented and validated for 2D axisymmetric and 3D flows. A multi-objetive optimization based on evolutionary algorithms is used for the exhaust design. A maximum benefit of approximately 0.32% on the total aircraft required thrust was observed by the application of compact exhaust designs. Furthermore, for the embedded system, is observed that the design of the compact exhaust and the nacelle afterbody have a considerable impact on the aerodynamic performance. To the author’s knowledge, this is the first detailed optimization of an exhaust system on an annular aft-mounted BLI propulsor.Item Open Access Dynamic swirl distortion characteristics in S-shaped diffusers using UCNS3D and time-resolved, stereo PIV methods(AIAA, 2024-01-04) Piovesan, Tommaso; Migliorini, Matteo; Zachos, Pavlos K.; Tsoutsanis, PanagiotisEmbedded propulsion systems are key enablers of future aircraft configurations with expected benefits in reduced environmental impact and enhanced performance. Such propulsion systems are typically integrated with convoluted, complex air induction systems whose dynamic distortion characteristics previously found detrimental to the engine’s stability. Therefore, predictive capability for these complex flows is critical for the design of closely coupled engine – intake architectures. A new High-Order Delayed Detached Eddy Simulation (HODDES) is applied in this work to predict dynamic flow distortion within an S-shaped subsonic diffuser. The aim is to assess the ability of a new solver to predict unsteady and extreme distortion events. The HODDES results have been validated with Time-Resolved Stereo PIV (TR-PIV) data. The analysis shows that the HODDES captures the key mean and unsteady flow characteristics, the spectral content and unsteady distortion descriptor behavior across the Aerodynamic Interface Plane (AIP). Although the predicted mean velocity levels, flow field unsteadiness and range of predicted velocities are notably higher than the ones observed at the experiment by at least 40%, it is suggested that this is an artifact of a discrepancy between the axial planes where the CFD and test data were analyzed. The findings of the work suggest that the HODDES is broadly capturing the dynamic flow fields and with some further effort towards the calibration of its RANS models can be further used to study the integration of closely coupled fan system downstream of air induction systems.Item Open Access High-resolution turbofan intake flow characterization by automated stereoscopic-PIV in an industrial wind tunnel environment(IOP Publishing, 2023-11-30) Kempaiah, Kushal U.; Piovesan, Tommaso; Zachos, Pavlos K.; Michaelis, Dirk; Gebbink, Roy; van Rooijen, Bart; Prieto, Daniel Gil; MacManus, David; Sciacchitano, Andrea; Sheaf, Christopher T.Unsteady inlet flow distortion can influence the stability and performance of any propulsion system, in particular for more novel, short and slim intakes of future aero-engine configurations. As such, the requirement for measurement methods able to provide high spatial resolution data is important to aid the understanding of these flow fields. This work presents flow field characterisations at a crossflow plane within a short aeroengine intake using stereoscopic particle image velocimetry (SPIV). A series of tests were conducted across a range of crosswind and high angle of attack conditions for a representative short and slim aspirated intake configuration at two operating points in terms of mass flow rate. The velocity maps were measured at a crossflow plane within the intake at an axial position L/D = 0.058 from where a fan is expected to be installed. The diameter of the measurement plane was 250 mm, and the final spatial resolution of the velocity fields had a vector pitch of 1.5 mm which is at least two orders of magnitude richer than conventional pressure-based distortion measurements. The work demonstrates the ability to perform robust non-intrusive flow measurements within modern intake systems in an industrial wind tunnel environment across a wide range of operating conditions; hence, it is suggested that SPIV can potentially become part of standard industrial testing. The results provide rich datasets that can notably improve our understanding of unsteady distortions and influence the design of novel, closely coupled engine-intake systems.Item Open Access Investigations of the unsteady aerodynamic characteristics for intakes at crosswind(American Society of Mechanical Engineers, 2022-10-28) Piovesan, Tommaso; Wenqiang, Zhang; Vahdati, Mehdi; Zachos, Pavlos K.The ground vortex generated in front of an intake operating near the ground and subjected to crosswind is investigated using CFD and compared to the experiments. The flow field of a scale-model intake is numerically simulated with both steady and unsteady approach, with the aim of predicting ground vortex effects and to characterize the vortex unsteady behaviour. The experimental results showed that for an intake near the ground under crosswind the ground vortex that forms under the intake and the in-duct separation, when present, exhibit unsteady behaviour that becomes stronger as the crosswind velocity is increased. The simulations indicate that a steady-state approach only partially reproduces the time-averaged ground vortex characteristics and in-duct distortion losses, while an unsteady approach shows a lower level of unsteadiness compared to the experimental observations. The consequences of the unsteady flow in the intake on the fan aerodynamic and aeroelastic stability are finally discussed to reinforce that these can result in significant non-synchronous vibration (NSV) and loss of stall margin which cannot be adequately assessed if no unsteady component of the inlet distortions is taken into account.Item Open Access Unsteady swirl distortion in a short intake under crosswind conditions(AIAA, 2024-01-04) Piovesan, Tommaso; Zachos, Pavlos K.; MacManus, David G.; Sheaf, Christopher T.In crosswind operating conditions, an aero-engine intake can be affected by notable unsteady flow distortions at the fan face. These distortions are typically associated with the ingestion of the ground vortex as well as with flow separation within the intake and can have a detrimental effect on the intake performance and therefore on the operability of the downstream compression system. Measurements of the unsteady velocity field within a model-scale intake under crosswind conditions were conducted using Stereo Particle Image Velocimetry (S-PIV) to characterize the velocity field and hence the intake flow distortion across the Aerodynamic Interface Plane (AIP) inside the duct. The intake distortion metrics were calculated for three operating conditions at a fixed crosswind velocity and increasing Mass Flow Capture Ratio (MFCR). The conditions at which the flow separates depend on crosswind velocity, ground clearance, the design of the intake and the MFCR. Flow characteristics of both low MFCR diffusion-driven, and high MFCR shock-induced separation were identified. The circumferential extent and intensity of the swirl distortion were found to be highly dependent on the crosswind velocity and MFCR. The swirl distortion caused by the diffusion-driven separation is greater than that due to shock-induced separation. The diffusion-driven separation was found to affect a bigger position of the intake AIP with higher time-average and peak values. An intermittent separation, that was observed for one value of MFCR in the range investigated, was found to cause peak levels of distortion twice the time-averaged values. Localized high swirl levels at a radial position near the intake surface correspondent to the tip region of a notional fan were observed. These can be expected to be detrimental to the operating stability of the downstream compression system.