CERES :: Browsing by Author "Nalianda, Devaiah"

Browsing by Author "Nalianda, Devaiah"

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Open Access
Abating CO2 and non-CO2 emissions with hydrogen propulsion
(Cambridge University Press (CUP), 2024-04-02) Mourouzidis, Christos; Singh, G.; Sun, X.; Huete, Jon; Nalianda, Devaiah; Nikolaidis, Theoklis; Sethi, Vishal; Rolt, Andrew Martin; Goodger, E.; Pilidis, Pericles
This contribution focuses on the abatement with hydrogen of CO2 and non-CO2 emissions. It is agenda-setting in two respects. Firstly, it challenges the globally accepted hydrocarbon sustainable aviation fuel (SAF) pathway to sustainability and recommends that our industry accelerates along the hydrogen pathway to ‘green’ aviation. Secondly, it reports a philosophical and analytical investigation of appropriate accuracy on abatement strategies for nitrogen oxides and contrails of large hydrogen airliners. For the second contribution, a comparison is made of nitrogen oxide emissions and contrail avoidance options of two hydrogen airliners and a conventional airliner of similar passenger capacity. The hydrogen aircraft are representative of the first and second innovation waves where the main difference is the weight of the hydrogen tanks. Flights of 1000, 2000, 4000 and 8000 nautical miles are explored. Cranfield’s state of the art simulators for propulsion system integration and gas turbine performance (Orion and Turbomatch) were used for this. There are two primary contributions to knowledge. The first is a new set of questions to be asked of SAF and hydrogen decarbonising features. The second is the quantification of the benefits from hydrogen on non-CO2 emissions. For the second generation of long-range hydrogen-fuelled aircraft having gas turbine propulsion, lighter tanks (needing less thrust and lower gas temperatures) are anticipated to reduce NOx emissions by over 20%; in the case of contrails, the preliminary findings indicate that regardless of the fuel, contrails could largely be avoided with fuel-burn penalties of a few per cent. Mitigating action is only needed for a small fraction of flights. For conventional aircraft this penalty results in more CO2, while for hydrogen aircraft the additional emission is water vapour. The conclusion is that our research community should continue to consider hydrogen as the key ‘greening’ option for aviation, notwithstanding the very significant costs of transition.
Open Access
Aero engine compressor fouling effects for short- and long-haul missions
(Sage, 2015-10-06) Igie, Uyioghosa; Goiricelaya, Mike; Nalianda, Devaiah
The impact of compressor fouling on civil aero engines unlike the industrial stationary application has not been widely investigated or available in open literature. There are questions about the impact of fouling for short- and long-haul missions comparatively, given their unique operational requirements and market. The aim of this study is to quantify the effects of different levels of fouling degradation on the fan, for two different aircraft with different two-spool engine models for their respective typical missions. Firstly, the study shows the increase in turbine entry temperature for both aircraft engines, to maintain the same level of thrust as their clean condition. The highest penalty observed is during take-off and climb, when the thrust setting is the highest. Despite take-off and climb segment being a larger proportion in the short-haul mission compared to the long-haul mission, the percentage increase in fuel burn due to fouling are similar, except in the worst case fouling level were the former is higher by 0.8% points. In addition to this, for all the cases, the additional fuel burn due to fouling and its cost is shown to be small. Likewise, the increase in turbine entry temperature for both missions at take-off are similar, except in the worst case fouling level for the short-haul mission were the turbine entry temperature is 7 K higher than the corresponding long-haul mission for the same level of degradation. The study infers that the penalty due to rise in temperature is of more concern than the additional fuel burn. Hence the blade technology (cooling and material) and engine thrust rating are key factors in determining the extent to which blade fouling would affect aero engine performance in short- and long-haul missions.
Open Access
Application of compressor water injection for the reduction of civil aircraft NOᵪ emissions.
(2018-12) Block Novelo, David Alejandro; Igie, Uyioghosa; Nalianda, Devaiah
Gas turbine Nitrogen Oxide (NOx) emissions are directly proportional to combustion temperature. These contaminants are associated with respiratory diseases and damage to the local water quality and wildlife. Higher demand on civil aviation, coupled to high-pressure ratio (and thus, temperature-ratio) engines, have caused aviation-borne NOᵪ Gas turbine Nitrogen Oxide (NOx) emissions are directly proportional to combustion temperature. These contaminants are associated with respiratory diseases and damage to the local water quality and wildlife. Higher demand on civil aviation, coupled to high-pressure ratio (and thus, temperature-ratio) engines, have caused aviation-borne NOᵪ emissions to double since 1990. This is of concern around airports, at operations below 3,000 ft. where the concentration of air traffic is high and the population faces direct exposure to engine contaminants. This thesis explores the use of atomized water droplets into an engine compressor as a way of intercooling the cycle and in doing so reducing NOᵪ emissions. The use of water injection is proposed to be applied only during take-off and climb up to 3,000 ft. The analysis of water injection is firstly applied to common turbofan architectures (2 and 3-spool), under varied ambient conditions. The gas turbines are simulated by means of an in-house performance simulating tool, Turbomatch. The changes in cycle temperature when water injection is applied, are accounted for by means of a stand-alone analytical compressor model. The platform calculates the thermodynamic exchange between the gas path of the engine and the water droplets in the Lagrangian frame of reference. The engine models are then integrated into an in-house aircraft performance simulating tool, Hermes. Two types of aircraft, narrow and wide-body, are considered for operations with the water injection system. The performance benefits noted in the stand-alone engine section, are evaluated considering the extra system weight for different missions ranging from 500 to 11,000 km. The observed theoretical trends are then confirmed by means of an experiment performed on a stationary gas turbine. The test includes performance monitoring (pressures, temperatures, mass flows), water droplet measurements, and exhaust emissions analysis. The most optimistic case of water injection shows a reduction of NOx emissions greater than 50%, for the period when water is used. This technology, when applied after the fan compressor, is effective at ambient temperatures as low as 5°C and is more promising in 3-spool engines. For the shortest mission considered, equivalent to a journey from London to Paris, the aircraft benefits from a small fuel saving, despite of the extra weight. For longer missions, there is a negligible fuel penalty (0.05%) derived from the extra payload. In all the cases Landing and Take-Off (LTO) emissions are estimated to be reduced by 42-43%. A reduction of NOx emissions of 25% is achieved experimentally when injecting 2% water-to-air ratio. The study concludes that compressor water injection is a feasible solution that can significantly reduce the environmental footprint of aviation emissions to double since 1990. This is of concern around airports, at operations below 3,000 ft. where the concentration of air traffic is high and the population faces direct exposure to engine contaminants. This thesis explores the use of atomized water droplets into an engine compressor as a way of intercooling the cycle and in doing so reducing NOᵪ emissions. The use of water injection is proposed to be applied only during take-off and climb up to 3,000 ft. The analysis of water injection is firstly applied to common turbofan architectures (2 and 3-spool), under varied ambient conditions. The gas turbines are simulated by means of an in-house performance simulating tool, Turbomatch. The changes in cycle temperature when water injection is applied, are accounted for by means of a stand-alone analytical compressor model. The platform calculates the thermodynamic exchange between the gas path of the engine and the water droplets in the Lagrangian frame of reference. The engine models are then integrated into an in-house aircraft performance simulating tool, Hermes. Two types of aircraft, narrow and wide-body, are considered for operations with the water injection system. The performance benefits noted in the stand-alone engine section, are evaluated considering the extra system weight for different missions ranging from 500 to 11,000 km. The observed theoretical trends are then confirmed by means of an experiment performed on a stationary gas turbine. The test includes performance monitoring (pressures, temperatures, mass flows), water droplet measurements, and exhaust emissions analysis. The most optimistic case of water injection shows a reduction of NOᵪ emissions greater than 50%, for the period when water is used. This technology, when applied after the fan compressor, is effective at ambient temperatures as low as 5°C and is more promising in 3-spool engines. For the shortest mission considered, equivalent to a journey from London to Paris, the aircraft benefits from a small fuel saving, despite of the extra weight. For longer missions, there is a negligible fuel penalty (0.05%) derived from the extra payload. In all the cases Landing and Take-Off (LTO) emissions are estimated to be reduced by 42-43%. A reduction of NOx emissions of 25% is achieved experimentally when injecting 2% water-to-air ratio. The study concludes that compressor water injection is a feasible solution that can significantly reduce the environmental footprint of aviation.
Open Access
Assessment of an energy-efficient aircraft concept from a techno-economic perspective
(Elsevier, 2018-04-17) Goldberg, Chana; Nalianda, Devaiah; Sethi, Vishal; Pilidis, Pericles; Singh, Riti; Kyprianidis, Konstantinos
An increase in environmental awareness in both the aviation industry and the wider global setting has led to large bodies of research dedicated to developing more sustainable technology with a lower environmental impact and lower energy usage. The goal of reducing environmental impact has necessitated research into revolutionary new technologies that have the potential to be significantly more energy efficient than their predecessors. However, for innovative technologies in any industry, there is a risk that adoption will be prohibitively expensive for commercial application. It is therefore important to model the economic factors of the new technology or policy at an early stage of development. This research demonstrates the application of a Techno-economic Environmental Risk Assessment framework that may be used to identify the economic impact of an energy-efficient aircraft concept and the impact that environmental policy would have on the viability of the concept. The framework has been applied to a case study aircraft designed to achieve an energy saving of 60% in comparison to a baseline 2005 entry-into-service aircraft. The model compares the green aircraft concept to a baseline conventional aircraft using a sensitivity analysis of the aircraft direct operating cost to changes in acquisition and maintenance cost. The research illustrates an economically viable region for the technology. Cost margins are identified where the increase in operating cost due to expensive novel technology is counterbalanced by the reduction in cost resulting from low energy consumption. Viability was found to be closely linked to fuel price, with a low fuel price limiting the viability of energy-efficient aviation technology. In contrast, a change in environmental taxation policy was found to be beneficial, with the introduction of carbon taxation incentivising the use of an environmentally optimised aircraft.
Open Access
Assessment of the BWB aircraft for military transport
(Emerald, 2020-04-06) Kissoon, Sajal; Mastropierro, Francesco; Nalianda, Devaiah; Rolt, Andrew Martin; Sethi, Bobby
Purpose The growth in air mobility, rising fuel prices and ambitious targets in emission reduction are some of the driving factors behind research towards more efficient aircraft. The purpose of this paper is to assess the application of a blended wing body (BWB) aircraft configuration with turbo-electric distributed propulsion in the military sector and to highlight the potential benefits that could be achieved for long-range and heavy payload applications. Design/methodology/approach Mission performance has been simulated using a point-mass approach and an engine performance code (TURBOMATCH) for the propulsion system. Payload-range charts were created to compare the performance of a BWB aircraft with various different fuels against the existing Boeing 777-200LR as a baseline. Findings When using kerosene, an increase in payload of 42 per cent was achieved but the use of liquefied natural gas enabled a 50 per cent payload increase over a design range of 7,500 NM. When liquid hydrogen (LH2) is used, the range may be limited to about 3,000 NM by the volume available for this low-density fuel, but the payload at this range could be increased by 137 per cent to 127,000 kg. Originality/value The results presented to estimate the extent to which the efficiency of military operations could be improved by making fewer trips to transport high-density and irregular cargo items and indicate how well the proposed alternatives would compare with present military aircraft. There are no existing NATO aircraft with such extended payload and range capacities. This paper, therefore, explores the potential of BWB aircraft with turbo-electric distributed propulsion as effective military transports.
Open Access
Computational approach for investigating nanoscale interfacial ice adhesion trends
(Royal Society of Chemistry, 2023-12-12) Vincent, Abhay; Pervier, Marie; Pervier, Hugo; Nalianda, Devaiah
For developing high performance, low-energy ice protection systems, it is vital to understand the icing physics at the interface of the ice and substrate. Macroscopic experiments have known limitations when it comes to explaining the adhesion characteristics of ice. There is a need to look at the microscale behaviour of ice and how it interacts with the surface it adheres on. The article describes application of molecular dynamics to the ice-substrate problem by modelling two major modes of ice adhesion test – tensile and shear tests, which are used for ice adhesion strength determination. The coarse-grained model of water is nucleated to form ice at the temperature which is designated for ice adhesion test on a macroscopic level. Steered molecular dynamics (SMD) is then applied to the nucleated ice cube to then obtain tensile and shear adhesion strengths over various FCC surface morphologies that represent the crystal structure of metallic substrates. The results obtained from the adhesion simulations are then used to compare the nanoscale trends on ice adhesion to the macroscale ice adhesion trends. The simulation results show that while contact area and temperature variations have similar trends to the observed macroscopic trends, other variations like tensile and shear loading rate variation at the nanoscale are not directly understood from macroscopic interpretations of ice adhesion.
Open Access
Cryogenic fuel storage modelling and optimisation for aircraft applications
(American Society of Mechanical Engineers, 2021-09-16) Rompokos, Pavlos; Rolt, Andrew Martin; Nalianda, Devaiah; Sibilli, Thierry; Benson, Claire
Designing commercial aircraft to use liquid hydrogen (LH2) is one way to substantially reduce their life-cycle CO2 emissions. The merits of hydrogen as an aviation fuel have long been recognized, however, the handling of a cryogenic fuel adds complexity to aircraft and engine systems, operations, maintenance and storage. The fuel tanks could account for 8–10% of an aircraft’s operating empty weight, so designing them for the least added weight is of high significance. This paper describes the heat transfer model developed in the EU Horizon 2020 project that is used to predict heat ingress to a cylindrical tank with hemispherical end caps with external foam insulation. It accounts for heat transfer according to the state of the tank contents, the insulation material properties, the environment, and the dimensions of the tank. The model also estimates the rate of pressure change according to the state of the fuel and the rate at which fuel is withdrawn from the tank. In addition, a methodology is presented, that allows for tank sizing taking into consideration the requirements of a design flight mission, the maximum pressure developed, and the fuel evaporated. Finally, the study demonstrates how to select optimal insulation material and thickness to provide the lightest design for the cases where no gaseous hydrogen is extracted, and where some hydrogen gas is extracted during cruise, the latter giving gravimetric efficiencies as high as 74%.
Open Access
Design evaluation and performance assessment of rotorcraft technology by 2050
(Netherlands Aerospace Centre (NLR), 2019-09-17) Stevens, Jos; Rademaker, Edward; Scullion, Calum; Vouros, Stavros; van Oosten, Nico; Misté, Gianluigi; Venturelli, Giovanni; Nalianda, Devaiah; Pachidis, Vassilios; Benini, Ernesto
The extended Clean Sky Joint Technology Initiative (JTI) within the EU Horizon 2020 Framework Programme [Ref. 1] proposes to introduce a number of concept aircraft and rotorcraft to replace reference technology counterparts at different time scales (2020/2035/2050). This Clean Sky 2 (CS2) promotes the importance of those concept configurations and their application in the future. An increasing global demand within and outside the European Union (EU) for an efficient air mobility and transportation system (i.e. more flexible, resilient, effective and affordable), and future projected growth for its application, will lead to the requirement for development of highly optimised transportation solutions.
Open Access
Design feasability of the electrical network for turboelectric aircraft propulsion.
(2020-01) Ibrahim, Kingsley; Sampath, Suresh; Nalianda, Devaiah
The motivation for this research is the need for safer and more environmentally friendly air transport system. Electrical propulsion systems have been identified as a potential method for improving aircraft performance going forward. The implementation of electrical drive trains for future aircraft propulsion comes with many challenges, due to the novelty and scale of the intended deployments. Major technological advancements and research are ongoing at system and component level to meet this ambition. However, the feasibility aspects of these studies have focused more on the engine side than on the electrical aspects, especially with regards to system reliability and stability. These have been considered in the earlier proposed sizing methods, using assumed fault and transient current magnitudes. Such assumption implies that the control and protection systems, may not properly handle abnormal operational scenarios. The aim of this research is to establish a procedure for sizing components of an electric propulsion system considering reliability and stability. The major objective is to properly quantify the operating parameters in non-steady state operations, like transients and fault scenarios, and establish that components are operating within their thermal limits at all operational stages. The contribution of this work is the development of a method that incorporates stability and reliability in the sizing process of electrical propulsion networks. The practicality of the proposed methods has also been validated experimentally, using a test facility set up for this study. The impact of this work is the reduction of the design uncertainties, resulting from assumed fault and transient characteristics of an electrical propulsion system. The results show that the assumptions in earlier researches do not suffice for the investigated architectures. A considerable mass penalty is incurred, with the power electronic devices having to be sized for slightly higher than the maximum transient currents.
Open Access
Development and application of a preliminary design methodology for modern low emissions aero combustors
(SAGE, 2020-04-23) Liu, Yize; Sun, Xiaoxiao; Sethi, Vishal; Li, Yi-Guang; Nalianda, Devaiah; Abbott, David; Gauthier, Pierre Q.; Xiao, Bairong; Wang, Lu
In this article, a preliminary design framework containing a detailed design methodology is developed for modern low emissions aero combustors. The inter-related design elements involving flow distribution, combustor sizing, heat transfer and cooling, emission and performance are coupled in the design process. The physics-based and numerical methods are provided in detail, in addition to empirical or semi-empirical methods. Feasibility assessment on the developed work is presented via case studies. The proposed combustor sizing methodology produces feasible combustor dimensions against the public-domain low emissions combustors. The results produced by the physics-based method show a reasonable agreement with experimental data to represent NOx emissions at key engine power conditions. The developed emission prediction method shows the potential to assess current and future technologies. A two-dimensional global prediction on liner wall temperature distribution for different cooling systems is reasonably captured by the developed finite difference method. It can be of use in the rapid identification of design solutions and initiating the optimisation of the design variables. The altitude relight efficiency predicted shows that the method could be used to provide an indicative assessment of combustor altitude relight capability at the preliminary design phase. The methodology is applied and shows that it enables the automatic design process for the development of a conceptual lean staged low emissions combustor. The design evaluation is then performed. A sensitivity analysis is carried out to assess the design uncertainties. The optimisation of the air distribution and cooling geometrical parameters addresses the trade-off between the NOx emissions and liner wall cooling, which demonstrates that the developed work has potential to identify and solve the design challenges at the early stages of the design process.
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
Economic viability assessment of NASA's blended wing body N3-X aircraft
(AIAA, 2017-07-12) Goldberg, Chana; Nalianda, Devaiah; Pilidis, Pericles; Singh, Riti
Numerous novel aircraft concepts are under development that aim to achieve dramatic increases in efficiency and reductions in emissions in comparison to current aircraft. Research into these concepts typically focuses on performance aspects to establish whether the aircraft will be capable of meeting developmental goals. However, the final goal of such concepts is to progress to viable commercial products. Economic viability assessments are therefore an integral part of the development process to ensure a sustainable industry. The key question to address is whether a high efficiency aircraft concept can translate into an attractive product from an economic perspective. This research performed an economic viability assessment of NASA's N3-X aircraft, a blended wing body aircraft with a distributed boundary layer ingesting propulsion system. The sensitivity of the aircraft's direct operating cost to changes in acquisition price and maintenance cost was predicted to establish maximum cost margins for the aircraft. In a May 2017 fuel price scenario, the N3-X could be no more than 25% more expensive than the baseline aircraft to remain economically viable. Introducing a carbon tax or fuel price jump widens the margin for increased costs. Aircraft cost estimates for the aircraft predict an acquisition cost from 11{37% more expensive than the baseline. In combination with the direct operating cost sensitivity analysis, the N3-X is predicted to need to capture 30% of the aircraft market up to 2035.
Open Access
Enabling cryogenic hydrogen-based CO2-free air transport: meeting the demands of zero carbon aviation
(IEEE, 2022-06-02) Sethi, Vishal; Sun, Xiaoxiao; Nalianda, Devaiah; Rolt, Andrew Martin; Holborn, Paul; Wijesinghe, Charith; Xisto, Carlos; Jonsson, Isak; Grönstedt, Tomas; Ingram, James; Lundbladh, Anders; Isikveren, Askin; Williamson, Ian; Harrison, Tom; Yenokyan, Anna
Flightpath 2050 from the European Union (EU) sets ambitious targets for reducing the emissions from civil aviation that contribute to climate change. Relative to aircraft in service in year 2000, new aircraft in 2050 are to reduce CO2 emissions by 75% and nitrogen oxide (NOx) emissions by 90% per passenger kilometer flown. While significant improvements in asset management and aircraft and propulsion-system efficiency and are foreseen, it is recognized that the Flightpath 2050 targets will not be met with conventional jet fuel. Furthermore, demands are growing for civil aviation to target zero carbon emissions in line with other transportation sectors rather than relying on offsetting to achieve “net zero.” A more thorough and rapid greening of the industry is seen to be needed to avoid the potential economic and social damage that would follow from constraining air travel. This requires a paradigm shift in propulsion technologies. Two technologies with potential for radical decarbonization are hydrogen and electrification. Hydrogen in some form seems an inevitable solution for a fully sustainable aviation future. It may be used directly as a fuel or combined with carbon from direct air capture of CO2 or other renewable carbon sources, to synthesize drop-in replacement jet fuels for existing aircraft and engines. As a fuel, pure hydrogen can be provided as a compressed gas, but the weight of the storage bottles limits the practical aircraft ranges to just a few times that is achievable with battery power. For longer ranges, the fuel needs to be stored at lower pressures in much lighter tanks in the form of cryogenic liquid hydrogen (LH2).
Open Access
Enhancing aero engine performance through synergistic combinations of advanced technologies.
(2019-07) Rolt, Andrew Martin; Sethi, Vishal; Nalianda, Devaiah
By 2050 the evolutionary approach to aero engine research and development will no longer be able to maintain historic rates of performance improvement. Future geared fan and open rotor engines promise increased propulsive efficiency and reduced noise, but will need to incorporate new technologies to improve core thermal efficiency in order to meet the ambitious fuel-burn and emissions targets set by ACARE in Flightpath 2050. In the face of increasing air traffic, radical new approaches will be needed to minimize the impact of aviation on the environment. A long-term vision is required. This PhD project investigates the potential of innovative propulsion technologies for civil aviation. Candidate technologies include topping and bottoming cycles, secondary combustion, intercooling and recuperation. The reported research investigates potential synergies between these advanced core technologies that when integrated together should give a significant fuel burn reduction relative to a more-conventional year-2050 ‘reference’ Brayton-cycle turbofan. Spreadsheet models have been used to quantify performance and estimate the weight and fuel burn savings for each new engine cycle. Further models were created to investigate preferred topping and bottoming cycle arrangements. NOx emissions are estimated for engines with rich-quench-lean (RQL) or lean-direct-injection (LDI) combustors. The correlation for future LDI combustor NOx emissions was selected following a review of recent LDI combustor research and a detailed study of alternative options. Increasingly aerodynamically efficient and lighter weight aircraft with more efficient engines will have lower thrust requirements. Advanced engine cycles also generally increase core specific power and reduce core mass flow, so future engines will have smaller turbo-machines that will tend to have lower component efficiencies. Therefore a preliminary study investigated the effects of thrust-scaling on the efficiency of the reference turbofan and possible high-OPR intercooled engines, since these could have very small core components. Novel core-component designs and engine architectures can minimize these penalties. Positive-displacement topping-cycle machines and reverse-flow-core engine layouts should help to maintain component efficiency and improve SFC, but low weight and low drag are also essential to minimize fuel burn. Therefore weight assessments of the advanced engine designs were made, and fuel-burn exchange rates used to quantify expected mission-level CO₂ reductions. Following a qualitative assessment of synergies between potential advanced technologies, an engine that combines intercooling, a topping cycle, secondary combustion and an open-air-cycle bottoming cycle was selected for detailed study. While each of these technologies has been researched previously, the contribution and value that each advanced core technology could bring to the whole in a large geared turbofan has not so far been reported. The approach initiated was to model a series of engines omitting each technology in turn and this scheme has been partially realized. The modelled topping-cycle technology uses six nutating-disc modules as a replacement for conventional combustors, high pressure compressors and turbines. A nutating-disc core module concept design led to the creation of a display model that was shown on the ULTIMATE project stand at the 2018 Farnborough International Air Show. The selected cycle combining all four technologies should reduce SFC by about 15% relative to the reference year-2050 turbofan and is assessed to reduce fuel burn by up to 18.5% in a long-range aircraft. An engine with intercooling, intra-turbine combustion and a bottoming cycle reduces SFC by about 6%, and an engine that is simply intercooled reduces SFC by about 3%. The topping cycle gives the biggest potential thermal efficiency improvement, but nutating-disc technology presents very significant design challenges for large aero engines, particularly with regard to internal sealing and bearing loads. Therefore it is recommended that alternative topping-cycle technologies should be researched for long-term aero engine performance improvements. A further study shows the effect of the target 15% reduction in fuel burn on in-flight CO2 emissions by the civil aviation fleet under various traffic-growth scenarios.
Open Access
Experimental rig for ice accretion and adhesion strength measurement for air cycle machine system
(Elsevier, 2023-06-06) Vincent, Abhay; Pervier, Marie L. A.; Pervier, Hugo; Nalianda, Devaiah; West, Peter; Agustin-Saenz, C.; Brusciotti, F.
Air cycle machines (ACM) which are part of the air-conditioning pack in every aircraft, are one such turbomachinery device that can be affected by icing issues particularly at the turbine end. Current ice protection solutions for the air cycle machines use a heating system on the downstream pipe to heat the surface, using electric resistance heaters or hot air coming from the ACM compressor stage. Both solutions require high energy, hence the need to reduce energy consumption through the development of passive energy-saving solutions. Clean Sky 2 ERICE project aims at developing an eco-friendly and cost-effective hydrophobic / ice-phobic solution able to resist ice adhesion in the ACM turbine scroll and its downstream pipe. This paper discusses the implementation of an experimental rig to reproduce the ice formation and accretion conditions within the ACM and a new shear test method to measure the ice adhesion strength on existing and new solutions in the form of coatings. The flow through the ACM turbine exhaust has also been characterized for the first time in published literature. The results from the ice accretion and adhesion tests show that hydrophobic coatings developed for the purposes of ice protection perform better than the current industry baseline material for ACM turbine scroll pipe internal surface. While these coatings could not be used to prevent accretion, they do help in reducing adhesion of ice to the surface.
Open Access
Hydrogen propulsion for civil aviation: an introduction scenario
(ISABE, 2022-09-30) Pantelis, Isidoros; Huete, Jon; Nalianda, Devaiah; Jarzębowska, Elżbieta; Pilidis, Pericles
Civil aircraft that fly medium and long ranges consume a large fraction of civil aviation fuel, injecting an important amount of aviation carbon into the atmosphere. Decarbonising solutions must consider this sector in a holistic manner. Hydrogen is increasingly seen as a key solution. There is a number of major issues to resolve. One of them is the provision of appropriate airport infrastructure. A philosophical-analytical scenario feasibility is proposed here based on an airliner family, previously proposed by the authors to assist in the elimination of carbon dioxide emissions from civil aviation. The family comprises six airliner models derived (not retrofits) from existing state of the art airliners. The objective of the philosophical investigation presented here is to explore the gradual implementation of airport infrastructure considering geographical and traffic characteristics. The outcome is a plausible and effective scenario where a gradual introduction of Hydrogen fuel is proposed where for a few decades Hydrogen will coexist with conventional fuels and drop-in Sustainable Aviation Fuels. This scenario proposes a first generation of six very large hydrogen hubs to cover very large traffic centres to make in the first instance deep inroads into civil aviation carbon emissions. A second generation of 16 hydrogen hubs is also proposed that would enable a global span. These two generations of hydrogen hubs could enable a very wide introduction of hydrogen in the long term by catalysing cost reductions with volume and experience, in the long-term delivering 3rd, 4th and nth generations of hydrogen hubs where reliance on carbon fuels is gradually reduced until they have been fully displaced in the long term.
Open Access
Impact of tank gravimetric efficiency on propulsion system integration for a first-generation hydrogen civil airliner
(Cambridge University Press, 2022-06-10) Huete, Jon; Nalianda, Devaiah; Pilidis, Pericles
Civil aircraft that fly long ranges consume a large fraction of civil aviation fuel, injecting an important amount of aviation carbon into the atmosphere. Decarbonising solutions must consider this sector. A philosophical-analytical feasibility of an airliner family to assist in the elimination of carbon dioxide emissions from civil aviation is proposed. It comprises four models based on the integration of the body of a large two-deck airliner with the engines, wings and flight surfaces of a long-range twin widebody jet. The objective of the investigation presented here is to evaluate the impact of liquid hydrogen tank technology in terms of gravimetric efficiency. A range of hydrogen storage gravimetric efficiencies was evaluated; from a pessimistic value of 0.30 to a futuristic value of 0.85. This parameter has a profound influence on the overall fuel system weight and an impact on the integrated performance. The resulting impact is relatively small for the short-range aircraft; it increases with range and is important for the longer-range aircraft. For shorter-range aircraft variants, the tanks needed to store the hydrogen are relatively small, so the impact of tank weight is not significant. Longer range aircraft are weight constrained and the influence of tank weight is important. In the case of the longest range, the deliverable distance increases from slightly over 4,000 nautical miles, with a gravimetric efficiency of 0.3, to nearly 7,000 with a gravimetric efficiency of 0.85.
Open Access
Impact of tip-vortex modeling uncertainty on helicopter rotor blade-vortex interaction noise prediction
(Vertical Flight Society, 2020-09-04) Vouros, Stavros; Goulos, Ioannis; Scullion, Calum; Nalianda, Devaiah; Pachidis, Vassilios
Free-wake models are routinely used in aeroacoustic analysis of helicopter rotors; however, their semi-empiricism is accompanied with uncertainty related to the modeling of physical wake parameters. In some cases, analysts have to resort to empirical adaption of these parameters based on previous experimental evidence. This paper investigates the impact of inherent uncertainty in wake aerodynamic modeling on the robustness of helicopter rotor aeroacoustic analysis. A free-wake aeroelastic rotor model is employed to predict high-resolution unsteady airloads, including blade-vortex interactions. A rotor aeroacoustics model, based on integral solutions of the Ffowcs Williams-Hawkings equation, is utilized to calculate aerodynamic noise in the time-domain. The individual analytical models are incorporated into an uncertainty analysis numerical procedure, implemented through non-intrusive Polynomial Chaos expansion. The potential sources of uncertainty in wake tip-vortex core growth modeling are identified and their impact on noise predictions is systematically quantified. When experimental data to adjust the tip-vortex core model are not available the uncertainty in acoustic pressure and noise impact at observers dominated by blade-vortex interaction noise can reach up to 25% and 3.50 dB respectively. A set of generalized uncertainty maps is derived, for use as modeling guidelines for aeroacoustic analysis in the absence of the robust evidence necessary for calibration of semi-empirical vortex core models.
Open Access
Impact of wake modeling uncertainty on helicopter rotor aeroacoustic analysis
(European Rotorcraft Forum, 2019-09-20) Vouros, Stavros; Goulos, Ioannis; Scullion, Calum; Nalianda, Devaiah; Pachidis, Vassilios
Free-wake models are routinely used in aeroacoustic analysis of helicopter rotors; however, their semi-empiricism is essentially accompanied with uncertainty related to physical wake parameters. In some cases, analysts have to resort to empirical adaption of these parameters based on previous experimental evidence. This paper investigates the impact of inherent uncertainty in wake aerodynamic modeling on the robustness of helicopter rotor aeroacoustic analysis. A freewake aeroelastic rotor model is employed to predict high-resolution unsteady airloads, including blade-vortex interactions. A rotor aeroacoustics model, fundamentally based on Acoustic Analogy, is utilized to calculate aerodynamic noise in the time-domain. The individual analytical models are incorporated into a stochastic analysis numerical procedure, implemented through non-intrusive Polynomial Chaos expansion. The possible sources of uncertainty in wake tip-vortex core modeling are identified and their impact on noise predictions quantified. When experimental data to adjust the tip-vortex core model are not available the uncertainty in acoustic pressure and ground noise impact at observers dominated by blade-vortex interaction noise can reach up to 25% and 3.50 dB respectively. This work aims to devise generalized uncertainty maps to be used as modeling guidelines for aeroacoustic analysis in the absence of the robust evidence necessary for calibration of semi-empirical vortex core models.
Open Access
Installed performance assessment of an array of distributed propulsors ingesting boundary layer flow
(ASME, 2018-12-29) Goldberg, Chana; Nalianda, Devaiah; Laskaridis, Panagiotis; Pilidis, Pericles
Conventional propulsion systems are typically represented as uninstalled system to suit the simple separation between airframe and engine in a podded configuration. However, boundary layer ingesting systems are inherently integrated, and require a different perspective for performance analysis. Simulations of boundary layer ingesting propulsions systems must represent the change in inlet flow characteristics which result from different local flow conditions. In addition, a suitable accounting system is required to split the airframe forces from the propulsion system forces. The research assesses the performance of a conceptual vehicle which applies a boundary layer ingesting propulsion system - NASA's N3-X blended wing body aircraft - as a case study. The performance of the aircraft's distributed propulsor array is assessed using a performance method which accounts for installation terms resulting from the boundary layer ingesting nature of the system. A `thrust split' option is considered which splits the source of thrust between the aircraft's main turbojet engines and the distributed propulsor array. An optimum thrust split for a specific fuel consumption at design point is found to occur for a thrust split value of 94.1%. In comparison, the optimum thrust split with respect to fuel consumption for the design 7500 nmi mission is found to be 93.6%, leading to a 1.5% fuel saving for the configuration considered.