Multipoint Aerodynamic Design of Ultrashort Nacelles for Ultrahigh-Bypass-Ratio Engines

Abstract

This paper presents a newly developed methodology for multipoint aerodynamic design of ultra-short nacelles for ultra-high bypass ratio turbofan engines. An integrated aerodynamic framework, based on parametric geometry generation and flow field solution via three-dimensional Reynolds-Averaged Navier-Stokes equations, was built and used for designing several ultra-short nacelle shapes and to evaluate their aerodynamic performance. An approach for estimating the static pressure distribution at the fan face, based on the parallel compressor theory, is presented and validated. A design strategy is introduced and various test cases are evaluated under the following critical operating conditions: mid-cruise, low speed/ high angle of attack, and pure crosswind. The major design parameters are highlighted and their influence in the flow field is discussed in detail for all the chosen flight conditions. Performance was evaluated by assessing inlet flow distortion and by bookkeeping of thrust and drag. The framework has proven to be suitable for designing high performance nacelles capable of operating under critical flight conditions, without flow separation or high levels of distortion. Drooping the inlet by 4 degrees is shown to reduce the drag at cruise by 1.9%, which also has a large beneficial impact on internal lip separation at high incidence conditions. Furthermore, crosswind was identified as the most severe of the conditions, requiring a drastic reshaping of the nacelle to avoid internal lip separation. Two final nacelle designs were compared: the first allowing inlet separation under a 90-degree crosswind condition, whilst the second was reshaped to be separation-free under all operating conditions. Reshaping to avoid separation

Powered Low-Speed Experimental Aerodynamic Investigation of an Over-Wing-Mounted Nacelle Configuration

“…The integrated over-wing nacelle geometry used to create the test model was designed using the methodology presented in [7,8], where the aerodynamic investigation of an OWN configuration was carried out. The chosen airframe geometry was the wing-body NASA Common Research Model (CRM) [20,21], which was scaled to the size of an A320, based on its mean aerodynamic chord (MAC).…”

“…The chosen airframe geometry was the wing-body NASA Common Research Model (CRM) [20,21], which was scaled to the size of an A320, based on its mean aerodynamic chord (MAC). The model features an axisymmetric nacelle with an ultra-short inlet, designed as part of the work conducted in [22], which presented a multipoint design method for ultrashort-nacelles. The pylon shape was created by vertically overlapping symmetric NACA four-digit airfoils.…”

“…Nonetheless, with the development of the design, optimization, and computational fluid dynamics (CFD) methods, there is some evidence that OWN integration can be an aerodynamically feasible option. Several recent studies have investigated over-wing installation of UHBPR engines [7][8][9][10][11][12]. A work by Hooker et al [12] is of particular interest.…”

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

“…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.…”

Effect of Unsteady Fan-Intake Interaction on Short Intake Design

“…Recent steady [15,16] and unsteady [17] CFD studies of short and conventional intakes with fan-coupling under high-incidence conditions showed the impact of intake design style and compactness on the onset of large total pressure and swirl distortions at the fan face due to notable separation of the intake boundary layer. Silva et al [18] assessed with steady CFD analyses different short intake designs under both high-incidence and crosswind conditions, and evaluated the impact of a change in short intake design on the status of the intake boundary layer. The crosswind analyses were conducted at a single operating point and therefore the separation mechanisms were not fully determined.…”