Towards the design and optimisation of future compact aero-engines: intake/fancowl trade-off investigation

Abstract

Purpose Relative to in-service aero-engines, the bypass ratio of future civil architectures may increase further. If traditional design rules are applied to these new configurations and the housing components are scaled, then it is expected that the overall weight, nacelle drag and the effects of aircraft integration will increase. For this reason, the next generation of civil turbofan engines may use compact nacelles to maximise the benefits from the new engine cycles. The purpose of this paper is to present a multi-level design and optimisation process for future civil aero-engines. Design/methodology/approach An initial set of multi-point, multi-objective optimisations for axisymmetric configurations are carried out to identify the trade-off between intake and fancowl bulk parameters of highlight radius and nacelle length on nacelle drag. Having identified the likely optimal part of the design space, a set of computationally expensive optimisations for three-dimensional non-axisymmetric configurations is performed. The process includes cruise- and windmilling-type operating conditions to ensure aerodynamic robustness of the downselected configurations. Findings Relative to a conventional aero-engine nacelle, the developed process yielded a compact aero-engine configuration with mid-cruise drag reduction of approximately 1.6% of the nominal standard net thrust. Originality/value The multi-point, multi-objective optimisation is carried out with a mixture of regression and classification functions to ensure aerodynamic robustness of the downselected configurations. The developed computational approach enables the optimisation of future civil aero-engine nacelles that target a reduction of the overall fuel consumption.

Deep-Learning for Flow-Field Prediction of 3D Non-Axisymmetric Aero-Engine Nacelles

“…This work investigates the design space for compact aero-engine nacelle with L nac /r hi = 3.1. This is a short configuration that is expected for future turbofan architectures [14]. Previous studies have highlighted the large aerodynamic non-linearity of this design space [33].…”

“…The CFD data used to build low order models for flow-field prediction of 3D non-axisymmetric aero-engine nacelles is generated with the approach developed by Tejero et al [14,24,25]. A thorough description of this computational method was provided in the past [14,24,25], and as such, a brief overview is presented below. The nacelle shape is defined with a parametric definition using intuitive Class-Shape Transformation (iCST) [26,27].…”

“…As such, the mesh with 1M was selected for this study. The described computational approach for 3D non-axisymmetric nacelles was previously validated with experimental data [14]. For a nominal Mach number of 0.85, the normalised nacelle drag obtained with CFD is overpredicted by 1.1% with respect to the measurements.…”

“…For this reason, research in recent years has focused on the design and optimisation of compact nacelles for future turbofans [14][15][16][17]. Previous studies investigated the impact of bulk parameters such as nacelle length or highlight radius on the nacelle drag characteristics [14], assessed the sensitivity of compact nacelle architectures to off-design conditions [15], coupled the nacelle design process with the thermodynamic engine cycle [16] or investigated the drag reduction benefits of transonic axisymmetric natural laminar flow nacelles [17]. All these investigations were based on computationally expensive numerical simulations that are not feasible within a preliminary design stage.…”

Coupled propulsive and aerodynamic analysis of an installed ultra-high bypass ratio powerplant at high-speed and high-lift conditions

“…However, this requires a detailed design of the fan cowl and exhaust aerodynamics to maximise the fuel savings. The design and optimisation approaches have been mostly focussed on the study of the nacelle and exhaust in isolation [5][6][7]. Nevertheless, the increase on the fan diameter will require a closer integration of the propulsion system within the airframe.…”