Mitigation of Engine Inlet Distortion through Adjoint-Based Design

Abstract

The adjoint-based design capability in FUN3D is extended to allow efficient gradientbased optimization and design of concepts with highly integrated aero-propulsive systems. A circumferential distortion calculation, along with the derivatives needed to perform adjoint-based design, have been implemented in FUN3D. This newly implemented distortion calculation can be used not only for design but also to drive the existing mesh adaptation process and reduce the error associated with the fan distortion calculation. The design capability is demonstrated by the shape optimization of an in-house aircraft concept equipped with an aft fuselage propulsor. The optimization objective is the minimization of flow distortion at the aerodynamic interface plane of this aft fuselage propulsor.

Performance bookkeeping for aircraft configurations with fuselage wake-filling propulsion integration

“…The overall net force in axial direction was determined as the sum of the integrated pressure and viscous forces over all body surfaces and the pressure and momentum flux contributions on the fan face and fan exit [65][66][67][68]. In a similar manner, Ordaz et al carried out an adjoint-based numerical design and optimization of BLI concepts (NASA STARC-ABL and MTA450-business jet with aft fan) with the objective of minimized flow distortion at the propulsor [69,70].…”

Recent Advances in Boundary Layer Ingestion Technology of Evolving Powertrain Systems

“…An optimization to minimize the distortion on the fan was presented by Ordaz et al [153]. This was achieved by employing an adjoint-based design tool that can adapt its meshing process to effectively calculate the distortion.…”

“…The research efforts focusing on the propulsive fuselage concept are summarized in Tables 3 and 4 Other studies [31] propeller in body's wake uniform flow propeller propulsive efficiency analysis; Brèguet-Coffin equation higher potential range; lower available kinetic energy [146] full-electric turboprop aircraft analytical calculations 25% benefit in energy efficiency [147] aft-mounted BLI propulsor Boeing 737-800 2D axisymmetric CFD studies power savings of 81-85% can be achieved [149] propulsor in the body's wake no experimental and 3D CFD studies reduced required power for same net axial force [150] thin haul PFC aircraft no mathematical analysis using an actuator model importance of velocity deficit parameter and overall energy efficiency [151] propeller in body's wake twin-turbo propeller aircraft (EIS 2035) BL profile from 1/7th power law; investigated thrust split and BLI propeller loading BLI presented negligible benefits [152] hybrid-electric aircraft; aft-BLI propeller ATR 42-500 aircraft FLOPS-based method; different tools integrated importance of synergistic benefits [153] aft-mounted BLI fan baseline BLI geometry optimization to minimize the distortion on the fan vertical tail-plane increases distortion levels [154,155] all-electric podded configuration RANS CFD studies power savings ranged between 3.4 to 4.9%; 20 dB noise reduction [156] partial turbo-electric conventional aircraft with two engines three levels of BLI thrust; CFD simulations; main engine redesign 2.8% fuel burn increase; 1.7% fuel burn increase after optimization [164] aft-mounted BLI fan no power balance method; 2D CFD models low FPR favorable; importance of thrust split [36] partial turbo-electric clean inflow propeller blade element theory; potential and 1/7 power law BL use of system level PSC; 1.5 to 5% power saving A chronological order illustration showing the start and finish publication dates of the most intensively boundary layer ingestion concepts studied in the open literature is presented in Figure 11. An interesting aspect emerging from this timeline illustration is that initial research efforts focused on radically changed aircraft concepts, moving away from the traditional tube-and-wing aircraft geometry.…”

Adjoint-Based Mesh Adaptation and Shape Optimization for Simulations with Propulsion

“…6 In fixed-wing applications, specialized permeable boundary conditions 7 and actuator zones 8 are typically used to model the propulsion system. Moreover, specialized outputs, such as those involving mass flow rates and stagnation pressure, [9][10][11] are required to characterize the aerodynamic performance of powered configurations. These add various challenges to the simulation -most notably, appropriate meshing of the propulsive stream-tube and exhaust plumes to control the discretization error in the quantities of interest.…”

“…8,11,13 The adjoint equation solved in both settings is the same, but the computation of the objective function gradient is perhaps less sensitive to issues regarding adjoint consistency, especially when using the discrete adjoint approach, leading to more widespread use. The work of Ordaz et al 10 on engine inlet distortion focuses on adjoint-based optimization, but also demonstrates progress toward adjoint-based mesh adaptation for stagnation-pressure outputs.…”