Browsing by Author "Hueso Rebassa, Josep"

Now showing 1 - 12 of 12
  • Thumbnail Image
    ItemOpen Access
    Aerodynamic optimisation of civil aero-engine nacelles by dimensionality reduction and multi-fidelity techniques
    (Emerald, 2022-09-30) Tejero, Fernando; MacManus, David G.; Hueso Rebassa, Josep; Sanchez Moreno, Francisco; Goulos, Ioannis; Sheaf, Christopher
    Purpose - Aerodynamic shape optimisation is complex due to the high dimensionality of the problem, the associated non-linearity and its large computational cost. These three aspects have an impact on the overall time of the design process. To overcome these challenges, this paper develops a method for transonic aerodynamic design with dimensionality reduction and multi-fidelity techniques. Design/methodology/approach - The developed methodology is used for the optimisation of an installed civil ultra-high bypass ratio aero-engine nacelle. As such, the effects of airframe-engine integration are considered during the optimisation routine. The active subspace method is applied to reduce the dimensionality of the problem from 32 to 2 design variables with a database compiled with Euler CFD calculations. In the reduced dimensional space, a co-Kriging model is built to combine Euler lower-fidelity and RANS higher-fidelity CFD evaluations. Findings - Relative to a baseline aero-engine nacelle derived from an isolated optimisation process, the proposed method yielded a non-axisymmetric nacelle configuration with an increment in net vehicle force of 0.65% of the nominal standard net thrust. Originality - This work investigates the viability of CFD optimisation through a combination of dimensionality reduction and multi-fidelity method, and demonstrates that the developed methodology enables the optimisation of complex aerodynamic problems.
  • Thumbnail Image
    ItemOpen Access
    Aerodynamic optimisation of civil aero-engine nacelles by dimensionality reduction and multi-fidelity techniques
    (Unknown, 2022-03-30) Tejero, Fernando; MacManus, David G.; Hueso Rebassa, Josep; Sanchez Moreno, Francisco; Goulos, Ioannis; Sheaf, Christopher
    Aerodynamic shape optimisation is complex due to the high dimensionality of the problem, the associated nonlinearity and its large computational cost. These three aspects have an impact on the overall time of the design process. To overcome these challenges, this paper develops a method for transonic aerodynamic design with dimensionality reduction and multi-fidelity techniques. It is used for the optimisation of an installed civil ultra-high bypass ratio aero-engine nacelle. As such, the effects of airframe-engine integration are considered during the optimisation routine. The active subspace method is applied to reduce the dimensionality of the problem from 32 to 2 design variables with a database compiled with Euler CFD calculations. In the reduced dimensional space, a co-Kriging model is built to combine Euler lower-fidelity and RANS higher-fidelity CFD evaluations. Relative to a baseline aero-engine nacelle derived from an isolated optimisation process, the proposed method yielded a non-axisymmetric nacelle configuration with an increment in net vehicle force of 0.65% of the nominal standard net thrust. This work demonstrates that the developed methodology enables the optimisation of complex aerodynamic problems.
  • Thumbnail Image
    ItemOpen Access
    Civil turbofan propulsion aerodynamics: thrust-Drag accounting and impact of engine installation position
    (Elsevier, 2021-01-28) Goulos, Ioannis; John Otter, John J.; Tejero, Fernando; Hueso Rebassa, Josep; MacManus, David G.
    It is envisaged that the next generation of civil aero-engines will employ high bypass ratios to lower specific thrust and improve propulsive efficiency. This trend is likely to be accompanied with the integration of compact nacelle and exhausts in podded under-wing installation positions that are close coupled to the airframe. This leads to the requirement for a comprehensive methodology able to predict aerodynamic performance for combined airframe-engine architectures. This paper presents a novel thrust and drag accounting approach for the aerodynamic analysis of integrated airframe-engine systems. An integral metric is synthesised based on the concept of net vehicle force. This is accomplished through the consolidation of aerodynamic coefficients, combined with the engine cycle characteristics obtained from a thermodynamic matching model. The developed approach is coupled with an in-house tool for the aerodynamic design and analysis of installed aero-engines. This framework is deployed to quantify the impact of engine installation position on the aerodynamic performance of a future large turbofan installed on a commercial wide-body airframe. The governing flow mechanisms are identified and their influence is decomposed in terms of the impact on airframe, nacelle, and exhaust performance. It is shown that it is essential to include the impact of installation on the exhaust for the correct determination of overall airframe-engine performance. The difference in net vehicle force for a close coupled position can reach up to -0.70% of nominal standard net thrust relative to a representative baseline engine location.
  • Thumbnail Image
    ItemOpen Access
    Computational assessment of non-axisymmetric separate-jet exhausts on test rig configurations
    (AIAA, 2023-06-08) Hueso Rebassa, Josep; MacManus, David G.; Goulos, Ioannis
    The next generation of civil turbofan engines are likely to have increased bypass ratios and lower fan pressure ratios to improve propulsive efficiency and to reduce specific fuel consumption. However, the larger size of these engines may result in increased overall aircraft drag partially that could offset the fuel consumption benefits. Non-axisymmetric exhaust configurations can contribute to the mitigation of these effects through an improved alignment of the thrust vector relative to the drag axis. However, there is a lack of knowledge on how to experimentally test non-axisymmetric exhaust designs. To address this, the study develops a non-axisymmetric configuration of the Dual Stream-Flow Reference Nozzle (DSFRN) and assesses it with computational fluid dynamics in various configurations and conditions. The objective is to establish a baseline approach for testing non-axisymmetric exhausts. Overall, it is recommended to test non-axisymmetric exhausts with the ambient wind-on effects included and to evaluate the three-dimensional exhaust characteristics using thrust vector angles, in addition to overall velocity and discharge coefficients. Moreover, the interaction between a swept wing and the non-axisymmetric exhaust was found not to have a notable impact on the exhaust characteristics.
  • Thumbnail Image
    ItemOpen Access
    Coupled propulsive and aerodynamic analysis of an installed ultra-high bypass ratio powerplant at high-speed and high-lift conditions
    (AIAA, 2023-06-08) Matesanz García, Jesús Matesanz; MacManus, David G.; Tejero, Fernando; Goulos, Ioannis; Hueso Rebassa, Josep; Swarthout, Avery E.; Christie, Robert
    To achieve the targets proposed in the Flightpath 2050 for the aviation industry, more efficient propulsive systems are required. One possible solution is to increase the bypass ratio of the engines to increase the propulsive efficiency and reduce the specific fuel consumption. However, larger fan diameters are expected for these configurations, which results in an increase in the aerodynamic coupling between the powerplant and the airframe. The aim of this work is to develop and demonstrate a thrust and lift matching methodology for installed powerplants using a coupled aero-propulsive model. As a proof of concept, the aerodynamic performance of an ultra-high bypass ratio powerplant integrated with the airframe was evaluated across different flight conditions. This includes high-lift operating conditions such as end of runway; and high-speed conditions such as mid cruise. To evaluate the aerodynamic performance of the propulsion integration a combined assessment of the airframe and powerplant aerodynamics is required using computational fluid dynamics (CFD). The integration of the powerplant with the airframe has the potential to change the engine requirements across the aircraft operational envelope. To account for this the aerodynamic analysis is coupled with a turbomachinery model to adjust the engine thermodynamic conditions at a given operating point.
  • Thumbnail Image
    ItemOpen Access
    Deep-learning for flow-field prediction of 3D non-axisymmetric aero-engine nacelles
    (AIAA, 2023-06-08) Tejero, Fernando; MacManus, David; Matesanz García, Jesús; Boscagli, Luca; Hueso Rebassa, Josep; Sheaf, Christopher
    Computational fluid dynamics (CFD) methods have been widely used for the design and optimisation of complex non-linear systems. Within this context, the overall process can typically have a large computational overhead. For preliminary design studies, it is important to establish design capabilities that meet the usually conflicting requirements of rapid evaluations and accuracy. Of particular interest is the aerodynamic design of components or subsystems within the transonic range. This can pose notable challenges due to the non-linearity of this flow regime. There is a need to develop low order models for future civil aero-engine nacelle applications. The aerodynamics of compact nacelles can be sensitive to changes in geometry and operating conditions. For example, within the cruise segment different flow-field characteristics may be encountered such as shock-wave boundary layer interaction or shock induced separation. As such, an important step in the successful design of these new architectures is to develop methods for fast and accurate flow-field prediction. This work studies two different metamodelling approaches for flow-field prediction of 3D non-axisymmetric nacelles. Firstly, a reduced order model based on an artificial neural network (ANN) is considered. Secondly, a low order model that combines singular value decomposition and an artificial neural network (SVD+ANN) is investigated. Across a wide geometric design space, the ANN and SVD+ANN methods have an overall uncertainty in the isentropic Mach number prediction of about 0.02. However, the ANN approach has better capabilities to predict pre-shock Mach numbers and shock-wave locations.
  • Thumbnail Image
    ItemOpen Access
    Design considerations of non-axisymmetric exhausts for large civil aero-engines
    (AIAA, 2023-06-08) Hueso Rebassa, Josep; MacManus, David G.; Goulos, Ioannis; Tejero, Fernando
    In order to reduce fuel consumption, the next generation of aero-engines are expected to operate with higher bypass ratios and lower fan pressure ratios. This will improve the propulsive efficiency of the power plant and reduce specific fuel consumption. Higher bypass ratios will be mostly accommodated with larger fan diameters. However, this will increase the size and mass of the powerplant, which could penalise the overall aircraft drag and erode some of the aero-engine cycle benefits. In addition, future configurations may require more close-coupled installations with the airframe due to structural and ground clearance requirements. This tendency may further exacerbate the adverse aerodynamic installation effects. A better integration of UHBR aero-engines with the airframe could be achieved with non-axisymmetric separate-jet exhausts. Non-axisymmetric configurations of the bypass nozzle can improve the performance of the aircraft by mitigating some of the penalising aerodynamic effects induced by the installation of the power plant. In this context, three-dimensional configurations of exhaust systems are parametrised and integrated with the propulsion system through a refined control of the geometry. The power plant is installed on the NASA Common Research Model and assessed with CFD. The design of non-axisymmetric exhausts is embedded in a relatively low-cost optimisation process. The method is based on response surface models and targets the optimisation of the aircraft net vehicle force for different design concepts of non-axisymmetric exhaust systems and several installation configuration. It is concluded that the optimisation of installed non-axisymmetric exhausts can benefit the overall aircraft net vehicle force between 0.5-0.9% of the engine nominal thrust, depending on the installation position.
  • Thumbnail Image
    ItemOpen Access
    Design optimisation of non-axisymmetric exhausts for installed civil aero-engines
    (Elsevier, 2023-10-31) Hueso Rebassa, Josep; MacManus, David; Tejero, Fernando; Goulos, Ioannis; Sánchez-Moreno, F.; Sheaf, Christopher
    Future civil aero-engines are likely to operate with higher bypass-ratios (BPR) than current power-plants to improve propulsive efficiency and reduce specific thrust. This will probably be accompanied by an increase of fan diameter and size of the power plant. Consequently, future configurations are likely to require more close-coupled installations with the airframe due to structural and ground clearance requirements. This tendency may lead to an increase in the adverse installation effects which could be mitigated with non-axisymmetric exhausts. However, due to the prohibitive computational cost, limited regions of the design space have been studied. For this reason, a relatively low-cost design approach for the integrated system is required. The aim of this work is to establish a method to map the non-axisymmetric exhaust design space where the effects of the propulsion system installation are taken into account. The methodology relies on the generation of a design database using inviscid computational fluid dynamics (CFD) methods. This is used to characterise the design space, identify the dominant design parameters and build response surface models for optimisation. The candidate designs that arise from the optimisation are assessed with viscous CFD simulations to assess the aerodynamic mechanisms and performance characteristics. The result is a set of design recommendations for installed configurations with non-axisymmetric exhausts. The method is an enabler for the optimisation of installed propulsion systems and has provided an exhaust design with a 0.7% improvement on net vehicle force relative to an axisymmetric exhaust, for a close coupled configuration where the fan cowl is overlapped with the wing. A reduction in net vehicle force is expected to lead to a similar reduction in cruise fuel burn.
  • Thumbnail Image
    ItemOpen Access
    Impact of installation on the performance of a civil turbofan exhaust at wind-milling: a combined experimental and numerical approach
    (Elsevier, 2025-03) Goulos, Ioannis; MacManus, David; Hueso Rebassa, Josep; Alderman, James; Sheaf, Christopher
    This work presents a combined experimental and numerical investigation of the effect of wing integration on the aerodynamic behaviour of a typical large civil aero-engine exhaust at wind-milling conditions. Engine performance simulations established estimates of Fan and Core Nozzle Pressure Ratios (FNPR and CNPR, respectively) for representative “engine-out” wind-milling scenarios. The experimental data and Reynolds Averaged Navier Stokes (RANS) Computational Fluid Dynamic (CFD) simulations encompassed End of Runway (EoR) take-off, diversion, and cruise wind-milling conditions for both isolated and installed configurations. The impact of FNPR, CNPR, free-stream Mach number (M∞), and high-lift surfaces on the installed suppression effect were evaluated. The measured and CFD predicted fan and core nozzle maps were implemented into the engine performance model to estimate the engine re-matching characteristics due to the impact of the installation, and the effect on engine mass flow. The effect of installation can reduce the fan and core nozzle discharge coefficients by up to 13% and 26%, respectively, relative to the isolated configuration for representative EOR wind-milling conditions. RANS CFD captures the effect of suppression on both the fan and core with an accuracy between 0.1% and 1.2%, depending on Mach number, which is sufficient for industrial design and analysis purposes. The engine performance analyses showed that the installed suppression effect can result in a 10% reduction of engine mass flow at EOR wind-milling. Within the context of nacelle design under wind-milling, this effect of exhaust suppression must be considered in determining the intake Mass Flow Capture Ratio (MFCR).
  • Thumbnail Image
    ItemOpen Access
    Impact of installation on the performance of an aero-engine exhaust at wind-milling flow conditions
    (American Society of Mechanical Engineers, 2024-02-01) Goulos, Ioannis; MacManus, David; Hueso Rebassa, Josep; Tejero, Fernando; Au, Andy; Sheaf, Christopher
    This paper presents a numerical investigation of the effect of wing integration on the aerodynamic behavior of a typical large civil aero-engine exhaust system at wind-milling flow conditions. The work is based on the dual stream jet propulsion (DSJP) test rig, as will be tested within the transonic wind tunnel (TWT) located at the aircraft research association (ARA) in the UK. The DSJP rig was designed to measure the impact of the installed pressure field due to the effect of the wing on the aerodynamic performance of separate-jet exhausts. The rig is equipped with the dual separate flow reference nozzle (DSFRN), installed under a swept wing. Computational fluid dynamic simulations were carried out for representative ranges of fan and core nozzle pressure ratios (CNPR) for “engine-out” wind-milling scenarios at end of runway (EOR) takeoff, diversion, and cruise conditions. Analyses were done for both isolated and installed configurations to quantify the impact of the installed pressure field on the fan and core nozzle discharge coefficients. The impact of fan and core nozzle pressure ratios, as well as freestream Mach number and high-lift surfaces on the installed suppression effect, was also evaluated. It is shown that the installed pressure field can reduce the fan nozzle discharge coefficient by up to 16%, relative to the isolated configuration for EOR wind-milling conditions. The results were used to inform the design and setup of the experimental activity which is planned for 2023.
  • Thumbnail Image
    ItemOpen Access
    Multi-fidelity assessment of exhaust systems for complete engine-airframe integrations
    (Unknown, 2020-02-28) Hueso Rebassa, Josep; Tejero, Fernando; Otter, John J.; Goulos, Ioannis; MacManus, David G.
    For podded underwing configurations, the goal of specific fuel consumption reduction has led to engine designs with larger fan diameters and higher bypass ratios to increase propulsive efficiency. As a consequence of this trend, the aerodynamic interference with the airframe is increased. Non-axisymmetric exhaust geometries could minimise such interference for coupled configurations. Class Shape Transformation functions are used to define 3D podded engine geometries that are installed on a transonic aircraft configuration. The complete system is assessed at mid-cruise conditions of a representative long-range cruise operation. The assessment is conducted by multi-fidelity computational fluid dynamics computations that are Euler inviscid and Reynolds Averaged Navier Stokes turbulent methods. The correlation between the different fidelities is analysed and a multi-fidelity co-kriging model is developed. The model is applied to predict the behaviour of installed non-axisymmetric exhaust systems and results into a 33% computational benefit compared to single-fidelity surrogates.
  • Thumbnail Image
    ItemOpen Access
    Optimization of installed compact and robust nacelles using surrogate models
    (ICAS, 2022) Sanchez Moreno, Francisco; MacManus, David; Hueso Rebassa, Josep; Tejero, Fernando; Sheaf, Christopher
    The design and optimization of aero-engine nacelles in a configuration installed on the airframe may be an important consideration to realize the cycle benefits of new ultra-high bypass ratio aero-engines. However, this is typically a high-dimensional design problem and there is a need to reduce the associated computational costs. This work presents a method for aerodynamic nacelle optimization for an installed configuration and provides further knowledge about the characteristics of this design space. The methodology includes single fidelity surrogate models built with inviscid flow solutions. Gaussian process regression and artificial neural networks are tested as modelling techniques. Viscous computations are used to assess the optimized designs at cruise and off-design windmilling diversion condition. This approach yielded an optimal design with a reduction in fuel burn of about 0.56% relative to a design optimized in isolated configuration without considering the powerplant integration effects. The optimal design also met the robustness criteria in terms of limited flow separation at the windmilling diversion conditions.