CERES :: Browsing by Author "Laskaridis, Panagiotis"

Browsing by Author "Laskaridis, Panagiotis"

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Open Access
Advancements and prospects of boundary layer ingestion propulsion concepts
(Elsevier, 2023-03-23) Moirou, Nicolas; Sanders, Drewan S.; Laskaridis, Panagiotis
The 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.
Open Access
Application of probabilistic principles to set-based design for the optimisation of a hybrid-electric propulsion system
(IOP, 2022-02-15) Spinelli, Andrea; Anderson, Luchien; Balaghi Enalou, Hossein; Zaghari, Bahareh; Kipouros, Timoleon; Laskaridis, Panagiotis
Current research in hybrid-electric aircraft propulsion has outlined the increased complexity in design when compared with traditional propulsion. However, current design methodologies rely on aircraft-level analysis and do not include the consideration of the impact of new technologies and their uncertainty. This can be a key factor for the development of future hybrid-electric propulsion systems. In this paper, we present a methodology for exploring the design space using the principles of Set-Based Design, which incorporates probabilistic assessment of requirements and multidisciplinary optimisation with uncertainty. The framework can explore every design parameter combination using a provided performance model of the system under design and evaluate the probability of satisfying a minimum required figure of merit. This process allows to quickly discard configurations incapable of meeting the goals of the optimiser. A multidisciplinary optimiser then is used to obtain the best points in each surviving configuration, together with their uncertainty. This information is used to discard undesirable configurations and build a set of Pareto optimal solutions. We demonstrate an early implementation of the framework for the design of a parallel hybrid-electric propulsion system for a regional aircraft of 50 seats. We achieve a considerable reduction to the required function evaluations and optimisation run time by avoiding the ineffective areas of the design space but at the same time maintaining the optimality potential of the selected sets of design solutions.
Open Access
Application of probabilistic set-based design exploration on the energy management of a hybrid-electric aircraft
(MDPI, 2022-03-08) Spinelli, Andrea; Balaghi Enalou, Hossein; Zaghari, Bahareh; Kipouros, Timoleon; Laskaridis, Panagiotis
The energy management strategy of a hybrid-electric aircraft is coupled with the design of the propulsion system itself. A new design space exploration methodology based on Set-Based Design is introduced to analyse the effects of different strategies on the fuel consumption, NOx and take-off mass. Probabilities are used to evaluate and discard areas of the design space not capable of satisfying the constraints and requirements, saving computational time corresponding to an average of 75%. The study is carried on a 50-seater regional turboprop with a parallel hybrid-electric architecture. The strategies are modelled as piecewise linear functions of the degree of hybridisation and are applied to different mission phases to explore how the strategy complexity and the number of hybridised segments can influence the behaviour of the system. The results indicate that the complexity of the parametrisation does not affect the trade-off between fuel consumption and NOx emissions. On the contrary, a significant trade-off is identified on which phases are hybridised. That is, the least fuel consumption is obtained only by hybridising the longest mission phase, while less NOx emissions are generated if more phases are hybridised. Finally, the maximum take-off mass was investigated as a parameter, and the impact to the trade-off between the objectives was analysed. Three energy management strategies were suggested from these findings, which achieved a reduction to the fuel consumption of up to 10% and a reduction to NOx emissions of up to 15%.
Open Access
Assessment of numerical radiation models on the heat transfer of an aero-engine combustion chamber
(Elsevier, 2020-11-02) Gamil, Abdelaziz A. A.; Nikolaidis, Theoklis; Lelaj, Indrit; Laskaridis, Panagiotis
Thermal radiation is the most dominant type of heat transfer inside the combustion chamber, which can directly affect the temperature distributions at the combustor walls. This paper provides a comprehensive analysis of the effects of two radiation models on the flame and liner-walls temperatures. A combustion chamber used in the Rolls-Royce-RB-183 turbofan engine was examined in this study by integrating a solid combustor model with the numerical fluid domain. The results indicated that the implementation of radiation models shrinks the flame peak-temperature and altered temperature distribution across the liner. The Discrete Ordinates Method (DOM) estimated a 10% higher temperature at the front part of the liner compared to the non-radiation model and 15% less than the P-1 radiation method. After the dilution zone, the DOM and P-1 models estimated respectively 15% and 25% reduction in the liner temperature compared to the non-radiation combustor. The radiation models have also down predicted the flame temperature by 200 K and more than 200 K for DOM and P-1 case respectively. The results also showed that the emissivity value had minimal effects on the combustor temperature distribution. The DOM considered being more accurate to estimate the combustor wall and flow temperatures compared to the P-1 radiation method
Open Access
Boundary layer ingestion performance assessments with application to business jets.
(2018-07) Sanders, Drewan S.; Laskaridis, Panagiotis
Advancements 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.
Open Access
Civil aero-propulsion application: effect of thrust rating change on engine time on-wing
(Cranfield University, 2015-11) Shafi, Syed Atif; Singh, R.; Laskaridis, Panagiotis
Engine fleet management has always been one of the most challenging tasks in any airline as it requires assuring reliability and cost effectiveness of engine operation at all times. The engine maintenance expenses are quite significant and accounts for about one third of the total aircraft maintenance costs. For all airlines with “Labour & Material” type of contractual arrangement with respective OEM / MRO provider, maximizing engine’s Time On-Wing (TOW) is extremely crucial to face lower maintenance costs, while at the same time abiding by governing airworthiness standards. Engine’s TOW is generally limited due to at least one of the following reasons: performance degradation reflected by lower Exhaust Gas Temperature (EGT) margin, hot section hardware life monitored by regular borescope inspections and Life Limited parts (LLP) expiry enforced by OEM or regulatory authority. After introducing relevant aero engine maintenance concepts and terminology, this thesis will serve to provide both qualitative and quantitative assessment of how certain operational factors of flight profile influence engine performance deterioration and maintenance costs. One such factor is the thrust rating of the engine. Higher thrust gives rise to higher internal temperatures, exposing engine hardware to greater mechanical and thermal stresses and therefore leading to faster rate of degradation and earlier engine removal. This thesis will be of interest to airlines having at least two different types of aircraft models in their fleet with different average flight profiles but powered by the same engine model with the required thrust variant. A particular engine may spend some time first on the aircraft that requires higher thrust rating before being switched to the aircraft that requires lower thrust rating or vice versa. This thesis will look into the feasibility of such an operational strategy through different aspects and discuss its effectiveness in retaining the engine performance for a longer time, thereby affecting the operating fuel costs and restoration costs per flying hour expected at the time of shop visit.
Open Access
Comparison of sodium sulphate deposition rate models based on operational factors influencing hot corrosion damage in aero-engines
(American Society of Mechanical Engineers, 2021-01-11) Pontika, Evangelia; Laskaridis, Panagiotis; Nikolaidis, Theoklis; Koster, Max
Hot corrosion is defined as the accelerated oxidation/sulphidation in the presence of alkali metal molten salts. It is a form of chemical attack that causes good metal loss. Current lifing models in aircraft engines focus on creep, fatigue and oxidation while hot corrosion damage has been overlooked as being of secondary importance. However, the absence of hot corrosion lifing models for aircraft engines often leads to unexpected and unexplained hot corrosion findings by aircraft engine operators and Maintenance, Repair and Overhaul (MRO) providers during inspections. Although hot corrosion does not cause failure on its own, the interaction with other damage mechanisms can reduce component life significantly, consequently, there is a requirement for including hot corrosion in the damage prediction process of aircraft engines. In both theoretical and experimental studies in literature, deposition of molten salts is identified as one of the primary conditions for hot corrosion to occur and an increased amount of deposited liquid salts accelerates the attack. Currently, most hot corrosion studies are limited to experimental testing of superalloys which are pre-coated with a controlled layer of salts. Such experimental studies are disconnected from gas turbine operating conditions during service. The present paper analyses two deposition rate models applicable to gas turbine operating conditions using Design of Experiments. Design space exploration is presented by taking into account gas turbine operating parameters which vary during a flight as well as temperature ranges where hot corrosion can occur. Analysis of variance is presented for 6 input parameters using Box-Behnken 3-level factorial design. Results from the Analysis of Variance indicate that the deposition rate models are sensitive to pressure and salt concentration in the gas flow. Finally, the saturation point of sodium sulphate has been investigated within the operating range of gas turbine and it was found that it can vary significantly under different conditions.
Open Access
Conceptual design and assessment of turboelectric and hybrid electric propulsion system architectures for civil transport aircraft.
(2018-03) Tashie-Lewis, Bernard Chukwudi; Laskaridis, Panagiotis; Miller, Paul; Husband, Paul
To achieve ambitious future environmental targets for aircraft set out by organisations such as NASA and the European Union, turboelectric distributed propulsion (TeDP) has been proposed as a novel concept that has the potential to achieve these targets by significantly improving integrated propulsion-airframe performance. Realising TeDP as a technology option brings into play a number of design and development challenges due to the highly integrated natured of TeDP-airframe configurations, low technology-readiness-levels of key enabling technologies and new modes of operation opened up by shift to a more electric architecture. In tackling these challenges a multidisciplinary and integrated method to assess the benefits and challenges of turboelectric and hybrid-electric propulsion system configurations by considering the effect of aircraft size, mission specifications, airframe, electrical system, energy storage, propulsor architecture and gas turbine architecture was created. The method created was used in the assessment of turboelectric and hybrid electric performance for a regional transport aircraft and a medium haul transport aircraft. For the regional role the employment of a DC hybrid superconducting turboelectric architecture managed to achieve 16.7% block fuel saving and 3.23% total energy consumption saving over a baseline turboprop aircraft at 600 n.mi range. Driving performance benefits was increased duration of mission time batteries spend discharging at relatively high battery power rating which overcomes weight penalties from installation of electric machinery. For medium haul role the employment of a geared hybrid electric architecture managed to achieve a 3.07% block fuel saving over a baseline turbofan aircraft at 900 n.mi range. Driving performance benefit for the mission was increased battery-operative-cruise time at relatively high battery power rating overcoming aircraft weight penalty and electric machinery installation weight penalty. Despite fuel burn reduction, hybrid electric aircraft consumes more energy than a baseline configuration primarily due to utilisation of additional energy from battery pack.
Open Access
Design space exploration and performance modelling of advanced turbofan and open-rotor engines
(Cranfield University, 2013) Giannakakis, Panagiotis; Laskaridis, Panagiotis; Singh, R.
This work focuses on the current civil engine design practice of increasing overall pressure ratio, turbine entry temperature and bypass ratio, and on the technologies required in order to sustain it. In this context, this thesis contributes towards clarifying the following gray aspects of future civil engine development: the connection between an aircraft application, the engine thermodynamic cycle and the advanced technologies of variable area fan nozzle and fan drive gearbox. the connection between the engine thermodynamic cycle and the fuel consumption penalties of extracting bleed or power in order to satisfy the aircraft needs. the scaling of propeller maps in order to enable extensive open-rotor studies similar to the ones carried out for turbofan engines. The rst two objectives are tackled by implementing a preliminary design framework, which comprises models that calculate the engine uninstalled performance, dimensions, weight, drag and installed performance. The framework produces designs that are in good agreement with current and near future civil engines. The need for a variable area fan nozzle is related to the fan surge margin at take-o , while the transition to a geared architecture is identi ed by tracking the variation of the low pressure turbine number of stages. The results show that the above enabling technologies will be prioritised for long range engines, due to their higher overall pressure ratio, higher bypass ratio and lower speci c thrust. The analysis also shows that future lower speci c thrust engines will su er from higher secondary power extraction penalties. A propeller modelling and optimisation method is created in order to accomplish the open-rotor aspect of this work. The propeller model follows the lifting-line approach and is found to perform well against experimental data available for the SR3 prop-fan. The model is used in order to predict the performance of propellers with the same distribution of airfoils and sweep, but with di erent design point power coe cient and advance ratio. The results demonstrate that all the investigated propellers can be modelled by a common map, which separately determines the ideal and viscous losses.
Open Access
Design space exploration of distributed propulsion HALE UAVs burning liquid hydrogen.
(Cranfield University, 2015-11) Gallo, Luca; Laskaridis, Panagiotis; Singh, R.
High altitude long endurance (HALE) unmanned aerial vehicles (UAV) could serve as a platform to promote disruptive aircraft technologies in addition to set the stage to sustain week-long flights with electronic equipment. Hydrogen fuel is essential to meet the long-endurance requirement of low-speed HALE UAVs due to its high energy content per unit mass—2.8 times greater than that of kerosene. Hydrogen fuel could also be used to cryogenically cool the electric transmission system in a turbo-electric and/or hybrid-electric distributed propulsion system. This advanced propulsion system has the potential to affect all the aspects of a HALE UAV, from how much power is required to sustain flight to how power is produced, managed and distributed. However, in the literature there are no indications or design rules about how an integrated airframe/distributed propulsion system should be designed to maximise the integration synergies. The aim of this research was to identify a multi-disciplinary and multi-fidelity methodology for design space exploration studies of distributed propulsion low-speed HALE UAVs burning liquid hydrogen. The purpose of this methodology was to assess how the aircraft power requirement, production, management, and distribution are affected by the airframe selection, the distributed propulsion system and the energy management system. The results indicate that the slipstream-wing interaction of distributed propellers could increase the maximum endurance by nearly 60% on a tube-and-wing airframe for a given engine cycle. Superconductivity was assumed for the hydrogen-cooled electric transmission system that links the core engine to the distributed propulsors. These endurance benefits were three to four times greater than that of the series hybrid energy management strategy and of the wave rotor hybrid cycles. As such, the distributed propellers technology should be furthered investigated for both low-speed HALE UAVs and other low-Mach applications.
Open Access
Discretized Miller approach to assess effects on boundary layer ingestion induced distortion
(Elsevier, 2016-12-21) Valencia, Esteban; Hidalgo, Víctor; Nalianda, Devaiah; Laskaridis, Panagiotis; Singh, R.
The performance of propulsion configurations with boundary layer ingestion (BLI) is affected to a large extent by the level of distortion in the inlet flow field. Through flow methods and parallel compressor have been used in the past to calculate the effects of this aerodynamic integration issue on the fan performance; however high-fidelity through flow methods are computationally expensive, which limits their use at preliminary design stage. On the other hand, parallel compressor has been developed to assess only circumferential distortion. This paper introduces a discretized semi-empirical performance method, which uses empirical correlations for blade and performance calculations. This tool discretizes the inlet region in radial and circumferential directions enabling the assessment of deterioration in fan performance caused by the combined effect of both distortion patterns. This paper initially studies the accuracy and suitability of the semi-empirical discretized method by comparing its predictions with CFD and experimental data for a baseline case working under distorted and undistorted conditions. Then a test case is examined, which corresponds to the propulsor fan of a distributed propulsion system with BLI. The results obtained from the validation study show a good agreement with the experimental and CFD results under design point conditions.
Open Access
Effect of change in role of an aircraft on engine life
(2017-05-03) Gad-Briggs, Arnold; Halsam, Anthony; Laskaridis, Panagiotis
New aircraft require years of development from concept to realisation and can be prone to delays. Consequently, military operators take existing fleets and operate them in a different role. The objective of this study is to examine the effect of operating a typical low bypass military fast jet engine, originally designed for a European theatre, in a hot and harsh climate. The specific purpose is to determine the effect on the high-pressure turbine blade life and the life- cycle cost of the engine. A mission profile and respective performance conditions were analysed and modelled using an in-house performance tool. The flow conditions were simulated using ANSYS® FLUENT. A conjugated heat transfer solution was adopted to determine the blade metal temperature. The blade was modelled physically in 3D using SIMULIA® ABAQUS FEA software. The stresses were derived and used to calculate the temperature coupled low cycle fatigue and creep life. A deterioration case was also studied to evaluate the effect of sand and dust ingestion. There was a significant life reduction of approximately 50% due to creep. The reduction in life was inversely proportional to the life cycle cost of the engine depending on the operating conditions. The results were compared with similar engines and summarised in the context of airworthiness regulations and component integrity.
Open Access
Effect of mixing Mach number and mixing efficiency on the preliminary cycle design of mixed high-BPR turbofans
(Elsevier, 2019-03-02) Cleton, Bjorn; Anselmi, Eduardo; Pellegrini, Alvise; Pachidis, Vassilios; Laskaridis, Panagiotis
This article presents the implementation of an updated analytical flow mixing model in a state-of-the-art, non-dimensional gas turbine cycle performance simulation and optimisation tool. The model considers three separate streams in the mixer, each expanding through its own ‘virtual’ nozzle. The use of three streams, compared to one single stream, allows for a more realistic simulation of a mixed exhaust gas turbine. This approach is used in a parametric study to assess the effect of the choice of mixing efficiency and mixer inlet Mach number on the preliminary design of mixed-exhaust, high-bypass ratio turbofan engines. It was found that in terms of best thermal performance, a trade-off exists between mixer inlet Mach number and mixer effectiveness. The findings of this research establish some useful guidelines for the accurate selection of these two parameters to achieve robust cycle designs.
Open Access
Energy-based aerodynamic loss and recovery characteristics of adiabatic and heated fuselages
(AIAA, 2023-06-07) Lamprakis, Ioannis; Sanders, Drewan S.; Laskaridis, Panagiotis
An 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.
Open Access
An evaluation of operation and creep life of stationary gas turbine engine
(Cranfield University, 2012-03) Eshati, Samir; Laskaridis, Panagiotis; Pilidis, Pericles
During operation, gas turbine components undergo various types of timedependent degradation due to high temperatures and mechanical loading. In the case of stationary GT engines for mechanical power, creep failure mechanism problems are a very common cause of mechanical failure that significantly reduces component life. The magnitude of the adverse effect is highly dependent on the operating conditions and design parameter of the components. Against this background, the research programme was aimed at achieving a better scientific understanding of the major reasons for creep failure. This would allow mechanical equipment to keep running free creep problem for longer. Therefore, the aim of this research was to develop an analytical life model capable of assessing the influence of humidity on the turbine blade heat transfer and cooling processes considering the engine design parameters, operating conditions and working environment which, in turn, affect blade creep life. The whole cooled blade row is regarded as heat exchanger with convective/film cooling and a thermal barrier coating. The approach is based on an engine performance model, heat transfer models and the change of properties of moist air as a function of water to air ratio (WAR). The changes of fluid properties due to the presence of water vapour were not only considered through a variation of the specific heat, the ratio of major specific heats and gas constant, but also with the variation of density, Reynolds number, Nusselt number and other related parameters. Cont/d.
Open Access
An experimental and numerical investigation of the effect of aero gas turbine test facility aspect ratio on thrust measurement.
(Cranfield University, 2011-08) Al-Alshaikh, Abdullatif; Pilidis, Pericles; Laskaridis, Panagiotis
This work describes the outcome of research program investigating thrust measurements in enclosed test facility for modern aero gas turbine engines. Literature work, experimental work and a description of Computational fluid dynamics simulation system have been developed to improve the accuracy of test bed thrust measurement. The key parameters covered in the research include test house size in relation to engine size. The effect of the distance of engine to detuner on the thrust correction factor was also investigated. The rule of loss mechanism within the test facility to include intake momentum drag, cradle drag, base drag, recirculation on loss and intake exhaust losses loss. The thrust correction factor prediction technique available in the open literature are compared with the result given by this research and conclusion are drawn. CFD predictions show that the biggest difference with experimental data is only 1 % in TCF for the largest test cell size. For the smallest test cell this difference increases to only 2%. These results in terms of accuracy are lower than what would normally be expected for general CFD work. The major contributions to thrust measurement technology include the following: 1. The research was able to ascertain that as engine size increases it will become more risky to rely on test bed results as giving an accurate prediction of static thrust. 2. The work has enabled confident prediction that test bed results can give test bed static thrust compared to free air testing with an accuracy of one half of 1%. 3. Using Fluent it has been possible to reproduce a comparable comparison with test bed results. This will give the user of the research a higher level of confidence in predicting thrust measurements for test beds whose size is small in comparison with engine size. 4. It is of course an ambition for all those working in the field to eliminate engine testing. However this is unachievable ambition. This research has shown the way to improve CFD prediction towards achieving this ambition. Finally detailed recommendations are given for continuation for this research program.
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, Panagiotis
This 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 work
Open Access
Hot corrosion damage modeling in aeroengines based on performance and flight mission
(AIAA, 2024-05-28) Pontika, Evangelia; Laskaridis, Panagiotis; Nikolaidis, Theoklis; Koster, Max
Hot corrosion is a form of chemical damage that causes surface degradation, sound material loss, and reduced component life. A lifing analysis in aeroengines without considering hot corrosion can lead to unexpected damage findings and increased scrap rates due to blade thickness loss beyond repair. This paper presents a novel methodology to predict hot corrosion damage based on aeroengine performance and flight mission analysis while taking into account environmental exposure, fuel quality, and material factors. The participating mechanisms, from salt and sulfur ingestion to deposition and hot corrosion attack, are discussed to explain the phenomenon in aeroengine components. In the investigated engine type, the first stage of the low-pressure turbine is the most affected. The application of the new methodology provides insights into the damage progression during the flight, the most affected components and the importance of capturing variations in the fuel quality, environmental exposure at the flight region, and the thrust derate policy. For a representative 1500 n mile mission, the variations in environmental exposure, fuel quality, and derate policy within typical limits can result in up to +350% damage. The outputs of the new framework can inform the decision making for maintenance, repair, and overhaul contract costing and scheduling.
Open Access
Hot corrosion damage modelling in aero engines based on performance and flight mission analysis
(AIAA, 2023-01-19) Pontika, Evangelia; Laskaridis, Panagiotis; Nikolaidis, Theoklis; Koster, Max
Lifing models for aircraft engines are mainly focused on creep, fatigue and oxidation, while hot corrosion remains one of the least explored areas. Hot corrosion is a form of chemical damage that causes surface degradation, sound material loss and reduced component life. A lifing analysis for aircraft engines without considering hot corrosion can lead to unexpected and unexplained hot corrosion findings by aircraft engine operators and Maintenance, Repair and Overhaul (MRO) providers during inspections. Although hot corrosion does not cause failure on its own, the interaction with other damage mechanisms can reduce component life significantly. Consequently, there is a necessity for including hot corrosion in the damage prediction process of aircraft engines. This paper presents a new methodology to estimate hot corrosion damage based on aero-engine performance and flight mission analysis while taking into account environmental exposure, fuel quality and material factors. The analysis in the present paper focuses on the hot corrosion progress over the course of the flight mission, while varying the major contamination factors and thrust derate, and the hot corrosion rate over flight time is then used to calculate the damage at the end of the mission. The participating mechanisms, from salt and sulfur impurity ingestion to deposition rate and hot corrosion attack, are analytically presented to explain the progress of the phenomenon in aero-engine components. In the investigated type of engine, the first stage of the low-pressure turbine is found to be the most affected. It is concluded that hot corrosion is favored by a combination of high pressure, high sulfur oxide concentration, and high salt deposition rate within an intermediate temperature range while the gas conditions near the component surface remain below the sodium sulfate saturation point, and these conditions are linked with aero-engine operation. The presented hot corrosion framework captures the effect of mission requirements, component operating conditions, environmental exposure, fuel quality and material on the hot corrosion damage of hot section components. It can be used to inform aero-engine maintenance planning, lifecycle analysis and MRO contract-costing, and can benefit digital twins for predictive maintenance.
Open Access
The impact of electric machine and propeller coupling design on electrified aircraft noise and performance
(AIAA, 2023-01-19) Zaghari, Bahareh; Kiran, Abhishek; Sinnige, Tomas; Pontika, Evangelia; Enalou, Hossein B.; Kipouros, Timoleon; Laskaridis, Panagiotis
Novel propulsion systems have been studied in literature to reduce aircraft emissions with hydrogen or other electrical energy sources. Hybrid Electric Propulsion (HEP) system consists of electric machines as an alternative way to provide power for propulsion resulting in the reduction of aircraft fuel consumption. While reduction of emission is the main driver of new HEP designs, aircraft noise reduction and performance improvement will also need to be investigated. Much quieter electrified aircraft than conventional aircraft is explored with considering the benefits of coupled design between the propeller and electric machines. In this study, several electric machine designs have been explored and coupled with the propeller design to study the trade-off between the aerodynamic and acoustic performance of the propeller. Aerodynamic optimization is used as a baseline to minimize the energy consumption to find the aerodynamics optimum subject to constraints on the thrust levels during the mission. The propeller aerodynamic optimizer considers the electric machine efficiency map, which is a function of propeller torque and rotational speed, to find the optimum combination of propeller and electric machine designs. The objective function of the acoustic optimizations is to reduce the cumulative noise level over the entire mission. It is shown that a wider envelope of peak motor efficiency in the efficiency map provides acoustics and aerodynamic performance benefits. The trade-offs between reducing noise or increasing aerodynamic efficiency to reduce energy consumption are demonstrated.