Browsing by Author "Sanders, Drewan S."
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Item Open Access Advancements and prospects of boundary layer ingestion propulsion concepts(Elsevier, 2023-03-23) Moirou, Nicolas; Sanders, Drewan S.; Laskaridis, PanagiotisThe aviation sector is experiencing an increasing pressure to reduce emissions via long-term strategies for a ceaselessly growing number of flight passengers. Aircraft currently in operation have typically been designed by considering the airframe somewhat separately from the propulsion system. In doing so, conventional aero-engine architectures are approaching their limits in terms of propulsive efficiency, with technological advancements yielding diminishing returns. A promising alternative architecture for improving the overall performance of the next generation of commercial aircraft relies upon boundary layer ingestion (BLI). This technology aerodynamically couples the airframe with a strategically positioned propulsion system to purposely ingest the airframe’s boundary layer flow. Nonetheless, there is a lack in consensus surrounding the interpretation and quantification of BLI benefits. This is primarily because conventional performance accounting methods breakdown in scenarios of strong aerodynamic coupling. Subsequently, there is a major challenge in defining appropriate performance metrics to provide a consistent measurement and comparison of the potential benefits. This review examines the various accounting methods and metrics that have been applied in evaluating BLI performance. These are discussed and critiqued in the context of both numerical and experimental models. Numerically, the geometric, aerodynamic and propulsive models are sorted by their orders of fidelity along with the plenitude of methods used for flow feature identification enabling a phenomenological understanding of BLI. Particular attention is then given to experimental BLI models with their different set-ups, methods and associated limitations and uncertainties. Finally, the numerous unconventional BLI aircraft concepts are categorised, compared and critiqued with reference to their associated design exploration and optimisation studies.Item Open Access Aero-propulsive performance assessment approach to boundary layer ingestion aircraft(Cranfield University, 2023-04) Moirou, Nicolas G. M.; Laskaridis, Panagiotis; Sanders, Drewan S.A promising solution towards more sustainable and efficient aircraft propulsion relies upon the ingestion of the boundary layer flow that develops around the airframe. Amongst the plethora of concepts, the propulsive fuselage concept appears to be the most pragmatic configuration, as a direct adoption of conventional tube-and-wing aircraft, which has an additional propulsor integrated around its tail. Nonetheless, there is a lack of consensus in the quantification and interpretation of the performance of such vehicles. Long-established momentum-based bookkeeping schemes break down as their underlying assumptions do not hold true in highly-integrated airframe-propulsion systems. Alternative approaches have been brought forth by considering holistically the aircraft to evaluate its performance and decompose its aerodynamic forces. Notably, energy- and exergy-based approaches improve one’s understanding on the cause and effect of boundary layer ingestion mechanisms but require high computational demands with dense grids. In sought of a universal approach, energy- and momentum-based methods are used together in this work to quantify the coupled aerodynamic performance of boundary layer ingestion aircraft. The strengths of near-field momentum integrations are coupled with more informative energy-based flow assessments. The design space of a propulsive fuselage aircraft is explored via CFD after a reduction of its modelling to an axi-symmetric partial assembly of the fuselage and propulsor. With variations in the thruster position along the tail, its flow passage through the fan and pressure rise, and exhaust design, best performance is achieved with a concept where the propulsor lies at 90% of the fuselage chord, for a fan hub radius of 30% of the fuselage radius, that ingests around 43% of the boundary layer mass-flow, and applies a pressure rise of 1.29, to generate around a third of the total propulsive force requirement whilst savings 11% of fuel relative to a short-to-medium range aircraft propelled by state-of-the-art turbofans. The reasons for such savings are detailed with a first-of-its-kind fully energetic flow decomposition which aims at attributing boundary layer ingestion benefits to changes in propulsor design.Item Open Access Boundary layer ingestion performance assessments with application to business jets.(2018-07) Sanders, Drewan S.; Laskaridis, PanagiotisAdvancements in propulsion system performance are reliant on improvements in propulsive efficiency, through increases in turbofan bypass ratio. This requires larger nacelle diameters, which incur external aerodynamic penalties. Business jets cruise at high subsonic Mach numbers, and are therefore normally propelled by high specific thrust turbofans. The business jet may benefit from a BLI propulsion system, whereby the specific thrust may be reduced without incurring such heavy penalties in external drag rise. The aim of the research is to perform a design exploration study on BLI applied to a business jet, with emphasis on external aerodynamics. Methods are developed to thoroughly analyse aerodynamic coupling between propulsor and airframe. A multi-physics, control-volume based approach led to the development of near-field momentum-based, far-field momentum-based and energy-based net-vehicle-force formulations. The former two, allowed for a set of thrust-force accounting systems to be defined. Energy-based methods, allowed for flow-field decompositions into different physical mechanisms. These include flow phenomena internal and external to the jet plume. The practical implications associated with applying these methods to RANS CFD solutions, is examined. This hinges around viscous stress tensor field continuity in the flow domain. It was found that the k — w SST turbulence model, along with a Green-Gauss Cell-Based gradient scheme, produced a continuous viscous stress tensor field. Having resolved this, the assessment methods were applied to solutions of non-propelled and propelled bodies. These methods were applied to control volumes having varying extents, which showed the far-field momentum-based method to be sensitive to spurious affects. The energy-based formulation, on the other hand, was observed to be relatively insensitive spurious affects. Good agreement (within 4%) was found between the forces predicted by all three methods over a non-propelled body. A very close agreement was observed between far-field momentum-based and energy-based results (within 1%) over the propelled body. However, much larger discrepancies were observed when compared against the near-field results. This was attributed to the increase in flow-field complexity, which now contained BL, shock and jet interaction regions. A design exploration study was performed by retrofitting a business jet with a fuselage concentric propulsor, powered by the baseline podded engines. A preliminary parametric study was first performed to gauge conditions favourable to BLI benefit. A ram drag approach to modelling BLI benefit was based on a flat plate analogy to obtain boundary layer profiles. Thrust-split, BLR, fan efficiency and intake pressure recoveries, were varied parametrically to asses potential benefits. An optimum SFC benefit between 5-7.5% was achieved at thrustsplits between 30-35%, when ingesting 65-90% of the BL thickness. This guided the the parametric CFD studies, where two tail-cone positions were examined. The first was placed at the top of the tail-cone, and the second positioned midway along the tail-cone. Benefits were only realised for the latter, where a 3-4% improvement in SFC was realised for a thrust-split around 20%, by ingesting 40% of the BL thickness. Energy breakdowns and decompositions were performed on all of the cases. One of the significant outcomes of this research was revealing that a significant proportion of the thrust force may be attributed to the isentropic expansion region within the jet plume's core.Item Open Access Computational investigation of the aerodynamic performance of an optimised alternative fuselage shape(Emerald, 2024-06-05) Odendaal, Diwan U.; Smith, Lelanie; Craig, Kenneth J.; Sanders, Drewan S.Purpose – The purpose of this study is to re-evaluation fuselage design when the main wing’s has the ability to fulfill stability requirements without the need for a tailplane. The aerodynamic requirements of the fuselage usually involve a trade-off between reducing drag and providing enough length for positioning the empennage to ensure stability. However, if the main wing can fulfill the stability requirements without the need for a tailplane, then the fuselage design requirements can be re-evaluated. The optimisation of the fuselage can then include reducing drag and also providing a component of lift amongst other potential new requirements. Design/methodology/approach – A careful investigation of parameterisation and trade-off optimisation methods to create such fuselage shapes was performed. The A320 Neo aircraft is optimised using a parameterised 3D fuselage model constructed with a modified PARSEC method and the SHERPA optimisation strategy, which was validated through three case studies. The geometry adjustments in relation to the specific flow phenomena are considered for the three optimal designs to investigate the influencing factors that should be considered for further optimisation. Findings – The top three aerodynamic designs show a distinctive characteristic in the low aspect ratio thick wing-like aftbody that has pressure drag penalties, and the aftbody camber increased surface area notably improved the fuselage’s lift characteristics. Originality/value – This work contributes to the development of a novel set of design requirements for a fuselage, free from the constraints imposed by stability requirements. By gaining insights into the flow phenomena that influence geometric designs when a lift requirement is introduced to the fuselage, we can understand how the fuselage configuration was optimised. This research lays the groundwork for identifying innovative design criteria that could extend into the integration of propulsion of the aftbody.Item Open Access Energy-based aerodynamic loss and recovery characteristics of adiabatic and heated fuselages(AIAA, 2023-06-07) Lamprakis, Ioannis; Sanders, Drewan S.; Laskaridis, PanagiotisAn energy-based aerodynamic analysis of the mechanical loss generation and potential energy/exergy recovery mechanisms is carried out for adiabatic and heated 2D axisymmetric flows over fuselage-shaped axisymmetric bodies. A generality of these mechanisms is obtained from dimensional analysis by appropriately scaling the freestream Reynolds and Mach numbers, while varying a reference fuselage’s fineness ratio. Thermo-aerodynamic implications and synergies of boundary-layer heating on the loss distribution, energy, and heat exergy recovery potentials are further considered for varying wall temperature ratios. The result is a clear identification of partial dynamic similarity and heat transfer effects on flow mechanisms such as shear layers, separation bubbles, and shockwaves of axisymmetric flows, and subsequent implications on loss distribution and energy recovery characteristics relating to boundary-layer ingestion. The analysis indicates that dissipating heat from aircraft surfaces aids, circumstantially, to drag reduction of unpowered fuselage bodies and increases, relative to the adiabatic, the recoverable energy fraction available for the boundary-layer ingestion propulsor, by strategically manipulating the loss distribution, while removing excess heat from the aircraft’s subsystem (batteries, fuel cells). Finally, an approach to assess the feasibility of exergetic heat recuperation as a possible means of useful work extraction and improved aerodynamic performance is explicitly introduced and discussed in the paper.Item Open Access Full-aircraft energy-based force decomposition applied to boundary layer ingestion(American Institute of Aeronautics and Astronautics, 2020-09-11) Sanders, Drewan S.; Laskaridis, PanagiotisThis paper introduces a generic force decomposition method derived from mechanical energy conservation. A transformation from relative to absolute reference frame captures the power transfer from pressure and skin-friction forces on aircraft surfaces to mechanisms in the flow-field . A unique flow-feature extraction procedure isolates these mechanisms into different regions including the jet-plume substructures, as well as shocks and shear-layers located externally to the jet. Featured is a novel shear-layer identification metric that captures both laminar and turbulent regions. The resulting energy balance is rearranged into a force decomposition formulation with contributions attributed to shocks, jets, lift induced vortices and the remaining wake. Boundary layer ingestion is used to demonstrate the method where a Potential for Energy Recovery factor is introduced and defines the amount of energy available at the trailing edge of an unpowered body. CFD results of a fuselage suggest 10% of its drag power is available for re-utilisation. CFD studies of a boundary layer ingesting propulsor show local minima in power consumption at a given thrust-split for particular combinations of fan pressure ratio and amount of boundary layer ingested. A noteworthy finding reveals significant contributions of volumetric pressure work, a term often neglected in previous workItem Open Access Fundamental considerations in the design and performance assessment of propulsive fuselage aircraft concepts(Cambridge University Press (CUP), 2024) Moirou, Nicolas G. M.; Mutangara, Ngonidzashe E.; Sanders, Drewan S.Propulsive fuselage aircraft complement the two under-wing turbofans of current aircraft with an embedded propulsion system within the airframe to ingest the energy-rich fuselage boundary layer. The key design features of this embedding are examined and related to an aero-propulsive performance assessment undertaken in the absolute reference frame which is believed to best evaluate these effects with intuitive physics-based interpretations. First, this study completes previous investigations on the potential for energy recovery for different fuselage slenderness ratios to characterise the aerodynamics sensitivity to morphed fuselage-tail design changes and potential performance before integrating fully circumferential propulsors. Its installation design space is then explored with macro design parameters (position, size and operating conditions) where an optimum suggests up to 11% fuel savings during cruise and up to 16% when introducing compact nacelles and re-scaling of the under-wing turbofans. Overall, this work provides valuable insights for designers and aerodynamicists on the potential performance of their concepts to meet the environmental targets of future aircraft.Item Open Access Potential for energy recovery from boundary-layer ingesting actuator disk propulsion(AIAA, 2024-01-26) Mutangara, Ngonidzashe E.; Smith, Lelanie; Craig, Kenneth J.; Sanders, Drewan S.The theoretical benefits of highly integrated propulsion systems are highlighted herein by assessing the potential for energy recovery utilization using actuator disk propulsion. Decomposing aerodynamic forces into thrust and drag for closely integrated bodies, particularly those employing boundary-layer ingestion, becomes challenging. In this work, a mechanical energy-based approach was taken using the power balance method. This allowed the performance to be analyzed through the mechanical flow power in the fluid domain, disregarding the need for any explicit definition of thrust and drag. Through this, the benefit of boundary-layer ingestion was observed from a wake energy perspective as a decrease in the downstream mechanical energy deposition and associated viscous dissipation. From a propulsion perspective, the reduction in power demand necessary to produce propulsive force indicated the possibility of power savings by utilizing the energy contained within the ingested boundary-layer flow.Item Open Access Potential for energy recovery of unpowered configurations using power balance method computations(AIAA, 2021-07-30) Mutangara, Ngonidzashe E.; Smith, Lelanie; Craig, Kenneth J.; Sanders, Drewan S.New aircraft developments are made to improve aircraft performance and efficiency. One such method is integrating propulsion into the airframe. This allows for boundary-layer ingestion, which shows promise of significant power benefits. However, these benefits are difficult to quantify as the propulsion system and aircraft body become meticulously integrated. The thrust and drag are coupled and cannot be defined separately, making conventional performance analysis methods inapplicable. The power balance method (PBM) addresses this by quantifying aircraft performance in terms of mechanical flow power and change in kinetic-energy rate. The primary focus of this work was to perform computational studies implementing the PBM on unpowered aerodynamic bodies to evaluate their respective drag contributions. A secondary study was also conducted to quantify the energy recovery potential of various bodies using a potential for energy recovery factor. The computational fluid dynamics case studies showed that drag obtained using the PBM agreed to within 2% of conventional momentum-based approaches. Maximal energy recovery potential was consistently observed at the trailing ends of the geometries, with values ranging between 9 and 12%.Item Open Access A scalable hydrogen propulsion system for civil transport aircraft(ICAS, 2022-11-28) van Heerden, Albert S. J.; Sasi, Sarath; Ghelani, Raj; Sanders, Drewan S.; Roumeliotis, IoannisThe aim of this research was to explore the application of engineering systems evolvability analysis techniques in devising potential scalable hydrogen propulsion systems for future civil transport aircraft. Baseline and derivative aircraft concepts were generated for a medium-sized long-range aircraft, with the derivative options having different levels of hydrogen incorporated in a dual-fuel arrangement (with separate hydrogen and kerosene turbofans), as well as potential turboelectric propulsion with boundary layer ingestion. Commonality between each baseline-derivative pair was then estimated, which could be used to predict the derivative development cost savings that could potentially be obtained when working from a specific baseline. The performance and cost results enabled different future scenarios to be explored. It was shown that developing the future concepts based on an existing state-of-the aircraft as baseline can offer considerable cost savings, as opposed to designing a clean sheet version. The importance of the baseline configuration selection in reducing the development cost for the different hydrogen configurations was also highlighted.Item Open Access Thrust/drag decomposition using partial pressure fields(Association Aeronautique et Astronautique de France (3AF), 2023-03-31) Hart, Pierce L.; Mutangara, Ngonidzashe E.; Sanders, Drewan S.; Schmitz, SvenThe accurate prediction of aircraft performance requires a robust definition of thrust/drag accounting. Traditional nacelle-pylon configurations have been treated as separate entities which are combined linearly; however, this is not feasible for embedded propulsion systems which have a higher degree of interaction than traditional designs. With the apparent shift to embedded propulsion systems in the N+3 generation of aircraft, of which boundary layer ingestion technology is a driving factor, improving our understanding of propulsion system interactions with an air-frame has never been more important. Since many of these interactions occur close to the body, a near-field decomposition method, partial pressure fields, is employed in CFD to provide insight as to the interactive aerodynamics of an embedded propulsion system.Item Open Access A unified partial pressure field and velocity decomposition approach toward improved energetic aerodynamic force decompositions(Association Aeronautique et Astronautique de France (3AF), 2023-03-31) Mutangara, Ngonidzashe E.; Sanders, Drewan S.; Laskaridis, Panagiotis; Hart, Pierce L.; Schmitz, SvenDrag decomposition through energy and exergy-based methods has been shown to have a variety of advantages. One of these is identifying and quantifying the recoverable energy within a flow field. This describes the available energy that can be used to produce thrust through systems such as boundary layer ingestion. Another advantage highlighted from prior work is that the velocity decomposition approach can split the flow field into its isentropic and non-isentropic contributions. This provides region-specific formulations for drag assessment, wherein the isentropic field is associated with contributions originating from the bulk flow and the non-isentropic field with the shear layer. This paper aims to assess the performance of a modified form of the velocity decomposition approach for transonic flows. This modification involves unification with partial pressure field analysis, which provides better flow field separability due to the added decomposition of the pressure field.Item Open Access Validation case studies of a numerical approach towards optimization of novel fuselage geometries(AIAA, 2023-01-19) Odendaal, Diwan U.; Smith, Lelanie; Craig, Ken; Mutangara, Ngonidzashe; Sanders, Drewan S.Optimization studies for improved fuselage designs primarily focus on drag reduction. However, when considering an alternative configuration where the stability requirements are assumed to be fulfilled by the main wing, eliminating the need for a tailplane, the fuselage design requirements are reconsidered. This work considers not only the reduction of drag but ensuring a component of lift as well as considering energy recovery potential for propulsion integration. The numerical modelling approach (turbulence model selection, optimization strategy and application of the Power Balance Method) is evaluated through a series of validation cases to determine a level of robustness and certainty. Three cases studies are completed: a 2D, compressible transonic RAE2282 airfoil, a 3D, incompressible low-drag body F-57 and a 3D, compressible body MBB3. The final approach includes a polyhedral mesh and SST k-ω turbulence model combined with multi-objective tradeoff optimization. Application of the Power Balance Method was validated within 1% for incompressible cases, however for the compressible cases the drag coefficient showed increasing deviation (1.3%) due to residual dissipative quantities.