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1.	Avellan, Rickard, 1976, et al. (författare) Boxprop, a forward-swept joined-blade propeller 2013 Ingår i: ISABE-2013-1108. Konferensbidrag (refereegranskat)abstract This article describes the Boxprop, a new high-speed propeller concept with forward swept joined-blade for future transport aircraft applications. Both numerical and experimental investigations of the joined-blade propeller were carried out at GKN Aerospace and Chalmers University in order to answer some of the fundamental questions relating to aerodynamic performance and mechanical integrity. The results show that the Boxprop concept works as intended and in particular that rapid prototyping methods using polymeric materials are suitable for early product development, even for functional testing of high speed propellers. Furthermore, based on the positive outcome of the experimental work described in this article, the next development step can be started by initiating the design of the counter-rotating Boxprop and wind tunnel test stand to proof the concept at TRL 3.
2.	Avellan, Rickard, 1976, et al. (författare) Preparing for Proof-of-concept of a Novel Propeller for Open Rotor Engines 2015 Ingår i: ISABE-2015-20097. Konferensbidrag (refereegranskat)abstract This article describes the development of a novel high-speed propeller concept. Large-scale propeller tests are extremely expensive and thus not appropriate at early R&D development phases. A convenient approach is to use computational methods validated by small-scale tests with propellers manufactured from low-cost materials and rapid manufacturing methods. The present paper is describing this cross validation work explaining differences between numerics and experiments. Preferred materials and manufacturing methods for high-speed future wind tunnel tests are discussed. We also discuss the progress of development of the aerodynamic design of the concept propeller.
3.	Capitao Patrao, Alexandre, 1988, et al. (författare) Aerodynamic and aeroacoustic comparison of optimized high-speed propeller blades 2018 Ingår i: 2018 Joint Propulsion Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics. Konferensbidrag (refereegranskat)abstract The Boxprop is a high-speed propeller concept intended for aircraft engines, which features blade pairs connected at the tip in order to decrease tip vortex strength, possibly reducing noise and improving aerodynamic performance relative to conventional high-speed propellers. This paper investigates the aerodynamic and aeroacoustic performance of three aerodynamically optimized high speed propellers; a 6-bladed conventional propeller, a 12-bladed conventional propeller, and a 6-bladed Boxprop. Performance results will be be compared for the three designs, with a focus on sectional performance and wake flow characteristics, and will show that the 6-bladed Boxprop performance lies somewhat in-between its 6 and 12-bladed conventional counterparts. The noise level at various observer positions is presented, and shows that the noise roughly follows the values of efficiency for the three propellers, with the Boxprop noise level being higher than the 12-bladed conventional propeller, but lower than the 6-bladed one. The lower blade loading and higher efficiency of the Boxprop relative to the 6-bladed conventional propeller results in slightly lower levels of noise at cruise.
4.	Capitao Patrao, Alexandre, 1988, et al. (författare) An Optimization Platform for High Speed Propellers 2016 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract To improve the efficiency by which current power plants translate jet energy into useful thrust the use of turboprop and in particular open rotor aircraft are being revisited. One challenge in association with developing new powerplants for such aircraft is high speed propeller design in general and noise prediction in particular.The Boxprop was invented in 2009 by GKN Aerospace in order to mitigate the effects of the tip vortex on noise and to improve upon the aerodynamics of a conventional propeller blade. The Boxprop is composed of a double-bladed propeller joined at the tips, and the design has the potential to eliminate the tip vortex, and thereby decrease that particular noise source. The complex and highly three-dimensional shape of an advanced propeller blade is challenging to model with classical propeller design methods, requiring instead more sophisticated optimization methods.This paper presents an optimization platform developed for high speed propellers, and illustrates its use by performing a reduced aerodynamic optimization of the Boxprop. The optimization process starts by performing a Latin Hypercube Sampling of the design space, and analyzes the resulting geometries using CFD. A meta-model employing radial basis functions is then used to interpolate on the obtained CFD results, which the GA uses to find optimal candidates along the obtained Pareto front. These designs are then evaluated using CFD, and their data added to the meta-model. The process iterates until the meta-model converges.The results of this paper demonstrate the capability of the presented optimization platform, and applying it on the Boxprop has resulted in valuable design improvements and insights. The obtained designs show less blade interference, more efficiently loaded blades, and less produced swirl. The methodology for geometry generation, meshing and optimizing is fast, robust, and readily extendable to other types of optimization problems, and paves the way for future collaborative research in the area of turbomachinery.
5.	Capitao Patrao, Alexandre, 1988, et al. (författare) Compact heat exchangers for hydrogen-fueled aero engine intercooling and recuperation 2024 Ingår i: Applied Thermal Engineering. - 1359-4311. ; 243 Tidskriftsartikel (refereegranskat)abstract This study investigates the application of compact heat exchangers for the purpose of intercooling and recuperation systems for short-to-medium range aircraft equipped with hydrogen-fueled turbofan engines. The primary objective is to assess the potential effects of engine-integrated compact heat exchangers on fuel consumption and emissions. The paper encompasses the conceptual design of integrated heat exchangers and associated ducts, followed by aerodynamic optimization studies to identify suitable designs that minimize air-side pressure losses and ensure flow uniformity at the inlet of the high-pressure compressor. Pressure drop correlations are then established for selected duct designs and incorporated into a system-level performance model, allowing for a comparison of their impact on specific fuel consumption, NOx emissions, and fuel burn against an uncooled baseline engine. The intercooled-recuperated engine resulted in the most significant improvement in take-off specific fuel consumption, with a reduction of up to 7.7% compared to the baseline uncooled engine, whereas the best intercooled engine resulted in an improvement of about 4%. Furthermore, the best configuration demonstrated a decrease in NOx emissions by up to 37% at take-off and a reduction in mission fuel burn by 5.5%. These enhancements were attributed to reduced compression work, pre-heating of the hydrogen fuel, and lower high-pressure compressor outlet temperatures.
6.	Capitao Patrao, Alexandre, 1988, et al. (författare) The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine 2024 Ingår i: Applied Thermal Engineering. - 1359-4311. ; 236 Tidskriftsartikel (refereegranskat)abstract Hydrogen is a promising fuel for future aviation due to its CO2-free combustion. In addition, its excellent cooling properties as it is heated from cryogenic conditions to the appropriate combustion temperatures provides a multitude of opportunities. This paper investigates the heat transfer potential of stator surfaces in a modern high-speed low-pressure compressor by incorporating cooling channels within the stator vane surfaces, where hydrogen is allowed to flow and cool the engine core air. Computational Fluid Dynamics simulations were carried out to assess the aerothermal performance of this cooled compressor and were compared to heat transfer correlations. A core air temperature drop of 9.5 K was observed for this cooling channel design while being relatively insensitive to the thermal conductivity of the vane and cooling channel wall thickness. The thermal resistance was dominated by the air-side convective heat transfer, and more surface area on the air-side would therefore be required in order to increase overall heat flow. While good agreement with established heat transfer correlations was found for both turbulent and transitional flow, the correlation for the transitional case yielded decent accuracy only as long as the flow remains attached, and while transition was dominated by the bypass mode. A system level analysis, indicated a limited but favorable impact at engine performance level, amounting to a specific fuel consumption improvement of up to 0.8 % in cruise and an estimated reduction of 3.6 % in cruise NOx. The results clearly show that, although it is possible to achieve high heat transfer rate per unit area in compressor vanes, the impact on cycle performance is constrained by the limited available wetted area in the low-pressure compressor.
7.	Capitao Patrao, Alexandre, 1988, et al. (författare) Wake Analysis of an Aerodynamically Optimized Boxprop High Speed Propeller 2019 Ingår i: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 141:9 Tidskriftsartikel (refereegranskat)abstract The Boxprop is a novel, double-bladed, tip-joined propeller for high-speed flight. The concept draws inspiration from the box wing concept and could potentially decrease tip vortex strength compared with conventional propeller blades. Early Boxprop designs experienced significant amounts of blade interference. By performing a wake analysis and quantifying the various losses of the flow, it could be seen that these Boxprop designs produced 45% more swirl than a conventional reference blade. The reason for this was the proximity of the Boxprop blade halves to each other, which prevented the Boxprop from achieving the required aerodynamic loading on the outer parts of the blade. This paper presents an aerodynamic optimization of a 6-bladed Boxprop aiming at maximizing efficiency and thrust at cruise. A geometric parametrization has been adopted which decreases interference by allowing the blade halves to be swept in opposite directions. Compared with an earlier equal-thrust Boxprop design, the optimized design features a 7% percentage point increase in propeller efficiency and a lower amount of swirl and entropy generation. A vortex-like structure has also appeared downstream of the optimized Boxprop, but with two key differences relative to conventional propellers. (1) Its formation differs from a traditional tip vortex and (2) it is 46% weaker than the tip vortex of an optimized 12-bladed conventional propeller.
8.	Capitao Patrao, Alexandre, 1988, et al. (författare) Wake and Loss Analysis for a Double Bladed Swept Propeller 2016 Ingår i: Proceedings of ASME Turbo Expo 2016: Turbine Technical Conference and Exposition, Seoul, South Korea, Jun 13-17, 2016. ; 1 Konferensbidrag (refereegranskat)abstract Inspired by Prandtl’s theory on aircraft wings with minimum induced drag, the authors introduced a double-bladed propeller, the Boxprop, intended for high-speed flight. The basic idea is to join the propeller blades pair-wise at the tip to improve aerodynamics and mechanical properties compared to the conventional propeller. The rather complex geometry of the double blades gives rise to new questions, particularlyregarding the aerodynamics.This paper presents a propeller wake energy analysis method which gives a better understanding of the potential performance benefits of the Boxprop and a means to improve its design.CFD analysis of a five bladed Boxprop demonstrated its ability to generate typical levels of cruise thrust at a flight speed of Mach 0.75. The present work shows that the near tip velocity variations in the wake are weaker for this propeller than a conventional one, which is an indication that a counter rotatingpropeller designed with a Boxprop employed at the front may exhibit lower interaction noise.
9.	Capitao Patrao, Alexandre, 1988, et al. (författare) Wake Energy Analysis Method Applied to the Boxprop Propeller Concept 2018 Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 79, s. 689-700 Tidskriftsartikel (refereegranskat)abstract Inspired by Prandtl's theory on aircraft wings with minimum induced drag, the authors have introduced a double-bladed propeller, the Boxprop, intended for high-speed flight. The basic idea is to join the propeller blades pairwise at the tip to decrease tip vortex strength and improve mechanical properties compared to a conventional propeller. The present work develops a wake analysis method allowing an energy breakdown of the flow as well as making the irreversibility of the flow explicit by using the entropy lost work concept. The method quantifies the strength of flow features such as tip vortices and wakes in terms of engine power. In contrast to existing work, this method removes assumptions of uniform flow, no radial flow, and constant static pressure in the propeller jet. The results of the wake analysis method can be summarized into three key findings 1) the energy in the tip-vortex of the Boxprop design is comparatively speaking non-existent, 2) the swirl energy level of the Boxprop is higher and this turbomachine is thus more in need of a downstream counter-rotating blade to recover the energy, 3) the Boxprop develops a much larger part of its thrust closer to the hub. Analysis of this aspect of the flow reveals that blade interference approaching the tip, where the blades in a pair are more closely spaced, is quite pronounced. In turn, this indicates that maximum efficiency Boxprop designs are more likely to be obtained by having larger axial separation of the two blades.
10.	De Campos, Gustavo Bonolo, et al. (författare) Propulsive efficiency of boundary layer ingestion propellers 2018 Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018. Konferensbidrag (refereegranskat)abstract The pursuit of lower fuel consumption for aircraft is promoting a departure from contemporary arrangements. One example is the development of more synergetic airframe and propulsion system designs, which are expected to increase significantly aircraft efficiency mainly by means of boundary layer ingestion. By integrating propulsion and airframe, both systems will significantly impact each other. This mutual interference requires the development of novel performance evaluation methods that consider such effects. This manuscript introduces a propulsive efficiency equation for boundary layer ingestion propellers based on the power balance method. Two formulations are presented for numerical and analytical evaluations. The equation is bounded between 0 and 1 and allows a meaningful evaluation of shaft to propulsive powers conversion, which results in an accurate determination of thrust and drag. This manuscript is the first advance of a project that will develop an optimizing tool for boundary layer ingestion propellers based on computational fluid dynamic simulations. The results will be presented in subsequent manuscripts.
11.	Giuliani, Fabrice, et al. (författare) PULSE DETONATION AS AN OPTION FOR FUTURE INNOVATIVE GAS TURBINE COMBUSTION TECHNOLOGIES: A CONCEPT ASSESSMENT 2010 Ingår i: 27TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES Proceedings. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract A study on innovative combustion system for future aeroengine core concepts is done in the frame of the NEWAC project (EU FP6, AIP5-CT-2006-030876). A part of the high pressure core is replaced by a pulse detonation combustor. The ambition is to achieve a technical leap in TSFC reduction, or alternatively a lighter engine. In order to provide technical assessments on both the feasibility and performance of such a concept, specific tools were developed at TU Graz, Austria and Chalmers University, Sweden. The study emphasises the impact of flow intermittency on the direct environment of the pulse detonation combustor, and on the performance of a hybrid turbofan. A literature survey establishes the state of the art on pulse detonation technologies. Numerical tools for CFD calculation and performance analysis are presented. A concept assessment with a TSFC reduction by 5% in comparison to a conventional cycle is derived.1 General IntroductionThe need for more efficient and environment friendly engines is tending towards new methods of combustion. Although new injections systems currently in development, like LPP (Lean Premixed Prevaporised), RQL (Rich burn Quick quench Lean burn) and LDI (Lean Direct Injection), are promising a reduction in pollutant emission there is also the trend to look for innovative combustion methods to lower in addition fuel consumption. One premising way to reduce thrust specific fuel consumption (TSFC) is to use pulse detonation [6].A study on innovative combustion system for future aeroengine core concepts is done in the frame of the NEWAC project. A part of the high pressure core of a conventional aeroengine is replaced by a pulse detonation combustor. A medium-range two-spool turbofan is taken as a baseline for a back-to-back comparison.Pulse detonation (PD) is attractive because of its potential for higher thermal efficiency.
12.	Grönstedt, Tomas, 1970, et al. (författare) DN Debatt. "Mellanlandning kan halvera utsläppen från Thailandsresa" 2018 Ingår i: Dagens Nyheter. ; , s. 5- Tidskriftsartikel (populärvet., debatt m.m.)abstract I debatten om flyget har det globala perspektivet glömts bort. Risken är att Sveriges bästa möjligheter att minska flygets klimatpåverkan hamnar i skuggan. Det finns nämligen mycket att göra som kan ge effekt redan på kort sikt: vi kan flyga på lägre höjd vid ogynnsamt väder och vi kan välja mindre flygplan och i stället mellanlanda, skriver fem flygforskare.
13.	Grönstedt, Tomas, 1970, et al. (författare) First and Second Law Analysis of Future Aircraft Engines 2013 Ingår i: ASME Turbo Expo, 2013. - 9780791855133 ; 2:GT2013-95516 Konferensbidrag (refereegranskat)abstract An optimal baseline turbofan cycle designed for a performance level expected to be available around year 2050 is established. Detailed performance data are given in take-off, top of climb and cruise to support the analysis. Losses are analyzed based on a combined use of the first and second law of thermodynamics, to establish a basis for discussion on future radical engine concepts and to quantify loss levels of very high performance engines. In the light of the performance of the future baseline engine, three radical cycles designed to reduce the observed major loss sources are introduced. The combined use of a first and second law analysis of an open rotor engine, an intercooled recuperated engine and an engine working with a pulse detonation combustion core is presented. In the past, virtually no attention has been paid to the systematic quantification of the irreversibility rates of such radical concepts. Previous research on this topichas concentrated on the analysis of the turbojet and the turbofan engine. In the framework developed, the irreversibility rates are quantified through the calculation of the exergy destruction per unit time. A striking strength of the analysis is that it establishes a common currency for comparing losses originating from very different physical sources of irreversibility. This substantially reduces the complexity of analyzing and comparing losses in aero engines. In particular, the analysis sheds new light on how the intercooled recuperated engine establishes its performance benefits.
14.	Grönstedt, Tomas, 1970, et al. (författare) First and Second Law Analysis of Future Aircraft Engines 2014 Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 136:3 Tidskriftsartikel (refereegranskat)abstract An optimal baseline turbofan cycle designed for a performance level expected to be available around year 2050 is established. Detailed performance data are given in take-off, top of climb, and cruise to support the analysis. The losses are analyzed, based on a combined use of the first and second law of thermodynamics, in order to establish a basis for a discussion on future radical engine concepts and to quantify loss levels of very high performance engines. In light of the performance of the future baseline engine, three radical cycles designed to reduce the observed major loss sources are introduced. The combined use of a first and second law analysis of an open rotor engine, an intercooled recuperated engine, and an engine working with a pulse detonation combustion core is presented. In the past, virtually no attention has been paid to the systematic quantification of the irreversibility rates of such radical concepts. Previous research on this topic has concentrated on the analysis of the turbojet and the turbofan engine. In the developed framework, the irreversibility rates are quantified through the calculation of the exergy destruction per unit time. A striking strength of the analysis is that it establishes a common currency for comparing losses originating from very different physical sources of irreversibility. This substantially reduces the complexity of analyzing and comparing losses in aero engines. In particular, the analysis sheds new light on how the intercooled recuperated engine establishes its performance benefits.
15.	Grönstedt, Tomas, 1970, et al. (författare) Flygforskare: "Våra beräkningar bygger på detaljerade modeller" 2018 Ingår i: Dagens Nyheter (DN). - 1101-2447. Tidskriftsartikel (populärvet., debatt m.m.)abstract SLUTREPLIK DN DEBATT 4/6. Kenneth Nilsson hävdar i sin replik att vi räknat fel på var gränsen går för att minska koldioxidutsläppen genom mellanlandning. Våra resultat stöds av mer generella studier som kommer nära våra resultat, skriver fem flygforskare.
16.	Grönstedt, Tomas, 1970, et al. (författare) Ultra low emission technology innovations for mid-century aircraft turbine engines 2016 Ingår i: ASME Turbo EXPO 2016, Seoul, June 13-17, South Korea. - 9780791849743 ; 3:GT2016-56123 Konferensbidrag (refereegranskat)abstract Commercial transport fuel efficiency has improved dramatically since the early 1950s. In the coming decades the ubiquitous turbofan powered tube and wing aircraft configuration will be challenged by diminishing returns on investment with regards to fuel efficiency. From the engine perspective two routes to radically improved fuel efficiency are being explored; ultra-efficient low pressure systems and ultra-efficient core concepts. The first route is characterized by the development of geared and open rotor engine architectures but also configurations where potential synergies between engine and aircraft installations are exploited. For the second route, disruptive technologies such as intercooling, intercooling and recuperation, constant volume combustion as well as novel high temperature materials for ultra-high pressure ratio engines are being considered. This paper describes a recently launched European research effort to explore and develop synergistic combinations of radical technologies to TRL 2. The combinations are integrated into optimized engine concepts promising to deliver ultra-low emission engines. The paper discusses a structured technique to combine disruptive technologies and proposes a simple means to quantitatively screen engine concepts at an early stage of analysis. An evaluation platform for multidisciplinary optimization and scenario evaluation of radical engine concepts is outlined.
17.	Huang, Zhongjie, 1985, et al. (författare) Aeroacoustic analysis of aerodynamically optimized joined-blade propeller for future electric aircraft at cruise and take-off 2020 Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 107 Tidskriftsartikel (refereegranskat)abstract A novel propeller with the blade tips joined in pairs, named Boxprop, is designed and optimized for a conceptual electric aircraft using an efficient optimization platform. According to the thrust requirement of the electric aircraft at cruise, the Boxprop with optimal efficiency is down-selected from the Pareto front of thrust coefficient and propeller efficiency. Furthermore, the blade pitch angle is adjusted to meet the thrust requirement at take-off. It is found that the Boxprop is capable of suppressing tip vortices and inducing a wider wake behind blade tip in comparison to a conventional propeller usually shedding a concentrated tip vortex, which could potentially improve the propulsive efficiency. Afterwards, the aeroacoustic analysis performed by the hybrid integral method of Reynolds-Averaged Navier Stokes equations (RANS) and convected Ffowcs Williams and Hawkings (FW-H) equation shows that the tonal noise from the Boxprop with three joined blades operating at cruise is similar to a conventional three-bladed propeller, though being stronger than a conventional six-bladed propeller. Although the tip vortices have been suppressed by the joined-blade tips of the Boxprop, the corresponding tonal noise reduction is not prominent. Next, the Boxprop noise at take-off is studied. Unsteady RANS is used to resolve varying flow structures that become dominant under the take-off condition. Angle of attack (AOA) is found as an important factor influencing the noise generation. The radiated noise upstream and downstream of the propeller significantly intensifies due to increasing AOA. The AOA effects of the Boxprop follow a similar trend to a conventional propeller. The findings for the Boxprop aeroacoustics have enhanced the understanding of tip-vortex suppression techniques in connection with the tonal noise generation, which will be greatly helpful to the aeroacoustic design of Boxprop applied to electric aircraft in the future.
18.	Huang, Zhongjie, 1985, et al. (författare) Low-Noise Propeller Design for Quiet Electric Aircraft 2020 Ingår i: AIAA AVIATION 2020 FORUM. - Reston, Virginia : American Institute of Aeronautics and Astronautics. Konferensbidrag (refereegranskat)abstract Inspired by the tremendous success of electric cars, the electrification technology has recently attracted a great deal of attention in aviation industry. This leads to the advent of massive efforts on the development of electric aircraft. Electrification enables zero CO2 and NOx emissions for aircraft in the near future. However, the annoying noise radiated from electrified propulsion systems is still a great challenge. The major noise sources are propellers. In particular, short-haul electric aircraft are usually flying from small airports near communities, which would exaggerate the noise impacts on residents. This paper presents a study on the propeller noise for a hypothetical electric aircraft. First of all, the acoustic study focuses on the effects of blade number, blade diameter, and rotation speed for an isolated propeller. Then, an unique configuration of dual-rotating propeller is briefly investigated to explore its potential of low-noise generation. Lastly, multiple propellers installed on an aircraft with various distributive propulsion strategies are investigated. The overall noise emission of these distributive propulsion strategies are promising to reduce the total noise from electric aircraft. Nonetheless, the noise level is very sensitive to the installation location of every propeller. An interesting finding is that the acoustic-wave interaction among the propellers are limited to the near field, and is insignificant in the far field. The present results are expected to enhance the understanding of propeller noise generation mechanisms, which are beneficial to propose guidelines on the development of low-noise distributive propulsion systems for electric aircraft.
19.	Jouannet, Christopher, et al. (författare) SUSTAINABLE AVIATION FOR SWEDEN - TECHNOLOGY & CAPABILITY ASSESSMENT TARGETING 2045 2022 Ingår i: 33rd CONGRESS OF THE INTERNATIONAL COUNCIL OF THE AERONAUTICAL SCIENCES. - 2958-4647. Konferensbidrag (refereegranskat)abstract The goal of this project is to analyse the possibilities offered by different technological solutions to achieve zero emission aviation, firstly in the Swedish/Nordic network context and secondly extend this to the European context. This project will investigate the potential and feasibility of new or upgraded aircraft types based on the different technologies mapped from both, various published roadmaps and national expertise from Swedish aerospace universities and companies. This involves developing aircraft conceptual designs studies and trade analysis with regards to different fuel types, propulsion technologies, structure, operations, network and fleet management, and all relevant technologies. The project will, on a common technology basis, analyse a range of zero carbon fuels and associated technologies through operational studies and optimization to accelerate the introduction of fossil free aircraft technology and choosing optimal paths for making aviation sustainable.
20.	Larsson, Linda, 1981, et al. (författare) A Conceptual Design Study of an Open Rotor Powered Regional Aircraft 2014 Ingår i: ASME Turbo Expo: Turbine Technical Conference and Exposition, Dusseldorf, GERMANY. JUN 16-20, 2014. - 9780791845578 ; , s. V01AT01A023- Konferensbidrag (refereegranskat)abstract Today many of the routes between small to medium sized airports and large hubs are operated by regional aircraft, powered by turboprop or turbofan engines. In the future the open rotor engine might provide an alternative option. The open rotor would combine the possibility of high cruise speed with high propulsive efficiency. Also, since the open rotor essentially is a turboprop with the possibility to fly fast, there is a benefit of high specific range at low cruising speeds, thus giving it a wide range cruise operation.In this paper a regional aircraft for 70 passengers and 3000 km range is studied. The aircraft is evaluated with both a counter rotating open rotor and a turbofan engine. Aircraft design parameters such as wing area and sweep are varied together with engine parameters such as engine power and propeller disc loading.Results show that the open rotor aircraft has a 17.0 % higher specific range at the optimal cruise Mach number compared to the turbofan aircraft. For higher speeds, at Mach 0.78, the difference is reduced to 15.0 %. The long range cruise Mach number is around Mach 0.7 for the open rotor aircraft while for the turbofan aircraft it is slightly higher, around Mach 0.72.
21.	Larsson, Linda, 1981, et al. (författare) EFFECTS OF DIFFERENT PROPELLER MODELS ON OPEN ROTOR FUEL CONSUMPTION 2013 Ingår i: International Society for Airbreathing Engines, ISABE, Busan, South Korea, 2013. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract In this study three different ways to represent a counter rotating propeller are evaluated. One where a map for a single rotating propeller is used, one where most of the swirl losses are excluded from the original map, and one where swirl losses are excluded and the position of the maximum efficiency is determined by the design disc loading.The two methods using the reduced swirl maps generate similar trends with similar size propellers for the optimal design and similar fuel burn figures. If the original single rotating map is used to represent counter rotating propellers the trends are significantly changed and are viewedto be unphysical. The optimal size propeller is then closer to 4.5 m rather than 3.5 meters. With the maps where a reduction in swirl losses are accounted for, the trends show a slightly decreasing fuel consumption with decreasing tip speed. If the single rotating propeller map is used there is an opposite trend and it is of higher magnitude.
22.	Lundbladh, Anders, 1964, et al. (författare) DISTRIBUTED PROPULSION AND TURBOFAN SCALE EFFECTS 2005 Ingår i: ISABE 2005, 17th Symposium on Airbreathing Engine. Konferensbidrag (refereegranskat)abstract A coupled aircraft and engine model is used to evaluate the fuel consumption and mission weight of distributed propulsion aircraft. The engine cycle is optimized for the installation to show the ultimate performance of each propulsion alternative. The effect of higher specific fuel consumption for smaller engines is weighed against the potentially lower installation weight and higher integration efficiency of distributed propulsion.
23.	Lundbladh, Anders, 1964, et al. (författare) Future Innovative Cores for Commercial Engines 2009 Ingår i: XIX International Symposium on Air Breathing Engines (ISABE). Konferensbidrag (refereegranskat)abstract Within the European technology validation project NEWAC (new aero engine core concepts) innovative cores aimed at implementation in post 2020 transport engines havebeen studied. Four routes were investigated, a variable core, a pulse detonation combustor, a counter rotating core, and unconventional heat management. Thestudy searches for technically feasible configurations andattempts to evaluate the benefit to the aircraft.
24.	Lundbladh, Anders, 1964, et al. (författare) High Power Density Work Extraction from Turbofan Exhaust Heat 2015 Ingår i: ISABE-2015-20101. Konferensbidrag (refereegranskat)abstract Integration of steam and air bottoming cycles with a conventional transport category turbofan is discussed. A conceptual design of a turbofan with a steam bottoming cycle yielded a 5% efficiency improvement for realistic component performance, but the weight eliminated in principal all gain on an aircraft level. For an air bottoming cycle simplified core cycle simulations showed the potential for up to 8% efficiency improvement. A novel Exhaust Heated Bleed engine where the bottoming cycle is integrated with a conventional turbofan turbo machinery is proposed. Simulation of this engine for take-off, climb and cruise conditions shows a 3-7% efficiency benefit. A concept for an exhaust heat exchanger and a conceptual turbine design for the Bleed Turbine to convert the exhaust heat to shaft power are illustrated.
25.	Lundbladh, Anders, 1964, et al. (författare) Installation effects for ultra-high bypass engines 2017 Ingår i: International Society of Air-breathing Engines (ISABE). Konferensbidrag (refereegranskat)abstract In the pursuit of ever more fuel-efficient engines, the fan diameter and bypass ratio are increasing rapidly. Although it allows the engine to perform more efficiently, it penalizes the aircraft performance with bigger nacelles, meaning more weight and bigger wetted drag-generating area. The nacelle design of such high bypass ratio engine is a problem, as the efficiency gain from the engine is counterbalanced, and sometimes eliminated by the nacelle weight and drag penalty.The paper presents a method that allows for a parametric design of two-dimensional axisymmetric nacelle geometry based on the shape function approach. An automated process is created that generates nacelle designs based on only a few parameters, meshes, and numerically computes the flow around the designed nacelles. A drag bookkeeping system is defined, and the nacelle drag is extracted from the simulation and analysed.The computed drag of nacelles, ranging from conventional length and thickness nacelles, through short/thin nacelles and ultrashort fan shrouds is analysed. Contrary to the first belief, ultrashort nacelles generate more drag than conventional length when the after-body drag-generating surfaces are considered. Furthermore, the study shows that shorter nacelle will greatly increase the flow velocity around the nacelle cowl and create a shock that induces wave drag.A boundary layer ingesting propulsor provides an alternative way to increase propulsive efficiency. The same automated design method was used to generate two differently sized propulsors mounted behind a fuselage, and the flow was numerically computed. In this case the flow around the nacelle cowl was found to be subsonic without shocks. The value of boundary pressure loss and ingested drag was shown to be predictable from the total pressure in the boundary layer on a similar fuselage without propulsor.
26.	Lundbladh, Anders, 1964 (författare) Miljö och framtid för flygmotorer 2018 Annan publikation (övrigt vetenskapligt/konstnärligt)
27.	Lundbladh, Anders, 1964, et al. (författare) Transforming Propulsion Installation for Commercial Aircraft 2013 Ingår i: ISABE-2013-1434. Konferensbidrag (refereegranskat)abstract The architecture of modern subsonic transport aircraft has converged to almost exclusively use engines in under wing nacelles. Although highly functional and successful in use, further reduction of fuel consumption with this configuration is progressively harder. The fuel consumption associated with nacelle weight and drag may in future aircraft using large low pressure ratio fans amount to 15% of the total. To achieve higher propulsive efficiency high speed propellers, distributed fans and boundary layeringestion have been proposed. The nacelle shape of currentinstallations is a compromise between the different requirements set from the varying flight speedover a flight mission. In the present paper, threeideas of shape changing, transforming elements in thepropulsion integration will be presented: adaption of a low drag nacelle to low speed conditions, mission variable noise shielding, and deployable propulsors.
28.	Sandberg, Marcus, et al. (författare) A knowledge-based master model approach exemplified with jet engine structural design 2017 Ingår i: Computers in Industry. - : Elsevier BV. - 0166-3615 .- 1872-6194. ; 85, s. 31-38 Tidskriftsartikel (refereegranskat)abstract Successful product development requires the consideration of multiple engineering disciplines and the quantification of tradeoffs among conflicting objectives from the very early design phases. The single-largest challenge to do so is the lack of detailed design information. A possible remedy of this issue is knowledge-based engineering. This paper presents a knowledge-based master model approach that enables the management of concurrent design and analysis models within different engineering disciplines in relation to the same governing product definition. The approach is exemplified on an early phase structural design of a turbo-fan jet engine. The model allows geometric-, structural mechanics- and rotor-dynamic- models to be concurrently integrated into a multi-disciplinary design and optimization loop. © 2016 Elsevier B.V.
29.	Sethi, V., et al. (författare) Enabling Cryogenic Hydrogen-Based CO 2 -Free Air Transport: Meeting the demands of zero carbon aviation 2022 Ingår i: IEEE Electrification Magazine. - 2325-5889 .- 2325-5897. ; 10:2, s. 69-81 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract 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).
30.	Sjögren, Oliver, 1993, et al. (författare) FAN STAGE DESIGN AND PERFORMANCE OPTIMIZATION FOR LOW SPECIFIC THRUST TURBOFANS 2023 Ingår i: International Journal of Turbomachinery, Propulsion and Power. - 2504-186X. ; 8:4 Tidskriftsartikel (refereegranskat)abstract In modern turbofan engines the bypass section of the fan stage alone provides the majority of the total thrust in cruise and the size of the fan has a considerable effect on overall engine weight and nacelle drag. Thrust requirements in different parts of the flight envelope must also be satisfied together with sufficient margins towards stall. An accurate description of the interdependencies of relevant performance and design attributes of the fan stage alone - such as efficiency, surge margin, fan-face Mach number, stage loading, flow coefficient and aspect ratio - are therefore necessary to estimate system level objectives such as mission fuel burn and direct operating cost with enough confidence during the conceptual design phase. The contribution of this study is to apply a parametric optimization approach to conceptual design of fan stages for low specific thrust turbofans based on the streamline curvature method. Trade-offs between fan stage attributes for Pareto-optimal solutions are modelled by training a Kriging surrogate model on the results from the parametric optimization. The trends predicted by the resulting surrogate model are analyzed both quantitatively and qualitatively. Most of the trends could be justified with some degree of physical reasoning or comparison with common guidelines from the literature. Trends of stage efficiency with Mach number and stage loading may indicate that shock losses have a larger impact on stage efficiency for designs with low stage loading compared to designs with high stage loading. Means to reduce the strength of the passage shock wave, such as blade sweep, may therefore be of more importance as stage loading is reduced.
31.	Tavares Silva, Vinícius, 1991, et al. (författare) Aerodynamic Installation Effects of Over the wing Mounted Ultra high bypass Engines 2022 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract In order to increase propulsive efficiency and decrease specific thrust, future aeroengines for commercial airliners will have to operate with higher bypass ratios and lower fan pressure ratios. This results in a substantial increase of the fan diameter. One major issue with the conventional under-wing installation of ultrahigh-bypass engines is the limited space underneath the wings. Integrating larger engines under-the-wings could require prohibitive increase in landing gear height and weight to attain an adequate ground clearance. One potential solution is to mount the engines over-the-wings, which would eliminate the ground clearance problem and, in addition, reduce ground noise. Over-wing nacelle installation acquired a bad reputation in the past since the benefits of such configuration would be often outweighed by poor aerodynamic performance. Nonetheless, some recent studies indicate that over-wing mounted nacelles could be a feasible integration option. This paper provides an aerodynamic evaluation of an over-the-wing mounted nacelle configuration compared with an under-the-wing configuration for a mid-cruise condition. The nacelles and pylons are designed by using an in-house tool for engine aircraft aerodynamic integration. The flow field is computed by means of Reynolds-averaged Navier-Stokes equations. The effects of wing/nacelle/pylon interference are investigated, and the aerodynamic performance of each configuration is evaluated by means of thrust and drag bookkeeping. Results show that the over-the-wing nacelle installation has increased the overall drag by 19.7 drag counts, when compared to a conventional under-wing mount, which was caused mainly due to a higher wing wave drag and pylon/nacelle interference drag.
32.	Tavares Silva, Vinícius, 1991, et al. (författare) MULTIPOINT AERODYNAMIC DESIGN OF A NACELLE FOR AN ELECTRIC FAN 2022 Ingår i: ICAS Proceedings. - 2958-4647. Konferensbidrag (refereegranskat)abstract Attention to aircraft electrification has been growing quickly since such technology carries the potential of drastically reducing the environmental impact of aviation. This paper describes the re-design of a nacelle for an electric fan, which is developed as part of the EleFanT (Electric Fan Thruster) project. A multipoint nacelle design approach was carried out. Initially the nacelle shapes were optimized for a cruise condition by employing an evolutionary genetic algorithm (GA). The flow field around the nacelles was calculated by conducting 2D axisymmetric computational fluid dynamics (CFD) simulations, and the objective functions were computed by means of thrust and drag bookkeeping. It was found that the optimizer favored two types of nacelle shapes that differed substantially in geometry. The designs were referred to as low spillage and high spillage types. The optimum low spillage and high spillage cases were selected and investigated further by the means of 3D CFD simulations at cruise and at an end of runway takeoff condition, where the nacelle is subjected to high angle of attack. Whilst the low spillage case provided a slightly better performance at cruise, it presented high levels of distortion and boundary layer separation at takeoff, requiring a substantial shape modification. The high spillage case performed well at takeoff; however, supersonic velocities could be observed at the cowling when it was subjected to incoming flow at an angle of attack. Nonetheless, such problem was easily corrected by drooping the inlet. Due to its superior performance at takeoff, the drooped high spillage design type was recommended.
33.	Tavares Silva, Vinícius, 1991, et al. (författare) Multipoint aerodynamic design of ultrashort nacelles for ultrahigh-bypass-ratio engines 2022 Ingår i: Journal of Propulsion and Power. - 1533-3876 .- 0748-4658. ; 38:4, s. 541-558 Tidskriftsartikel (refereegranskat)abstract This paper presents a newly developed methodology for multipoint aerodynamic design of ultrashort nacelles for ultrahigh-bypass-ratio turbofan engines. An integrated aerodynamic framework, based on parametric geometry generation and flowfield solution via three-dimensional Reynolds-averaged Navier-Stokes equations, was built and used for designing several ultrashort nacelle shapes and to evaluate their aerodynamic performance. An approach for modeling the inlet-fan coupling is presented and validated. A design strategy is introduced, and various test cases are evaluated under the following critical operating conditions: midcruise, low speed/high angle of attack, and pure crosswind. The major design parameters are highlighted and their influence in the flowfield is discussed in detail for all the chosen flight conditions. Performance was evaluated by assessing inlet flow distortion and by bookkeeping of thrust and drag. The framework has proven to be suitable for designing high-performance nacelles capable of operating under critical flight conditions, without flow separation or high levels of distortion. Drooping the inlet by 4 deg is shown to reduce the drag at cruise by 1.9%, which also has a large beneficial impact on internal lip separation at high-incidence conditions. Furthermore, crosswind was identified as the most severe of the conditions, requiring a drastic reshaping of the nacelle to avoid internal lip separation. Two final nacelle designs were compared: the first allowed inlet separation under a 90 deg crosswind condition, whereas the second was reshaped to be separation-free under all operating conditions. Reshaping to avoid separation has increased drag by 5.1% at cruise.
34.	Tavares Silva, Vinícius, 1991, et al. (författare) Over-wing integration of ultra-high bypass ratio engines: A coupled wing redesign and engine position study 2023 Ingår i: Aerospace Science and Technology. - 1270-9638. ; 138 Tidskriftsartikel (refereegranskat)abstract The integration of next-generation high-bypass turbofan engines poses a major challenge to the aeronautical industry due to the larger fans necessary to achieve more fuel-efficient engines. The limited space underneath the wings and the strict ground clearance constraints bring the necessity to investigate solutions other than the conventional under-wing mounted engines. Over-wing installed nacelles have the potential to solve the ground clearance issue and, in addition, might reduce ground noise due to acoustic shielding from the wing. Nevertheless, a strong and complex coupling between aerodynamics and propulsion is the result of such integration choice, and traditional design practices may result in configurations with prohibitively high drag penalties. This paper presents a novel wing redesign method, specifically developed for over-wing mounted engines. The wing is reshaped to recover the spanwise lift distribution of the clean airframe (wing-body) configuration, for a single aisle airliner at a cruise condition. The wing redesign is conducted along with an engine position sensitivity study, in which the wing is reshaped for different engine axial and vertical positions. The coupling between propulsion and aerodynamics is thoroughly investigated, as well as the interaction and interference effects between the wing, pylon, and nacelle. Moreover, the best over-wing solution is compared to a baseline under-wing mounted nacelle. Results show that, by applying the developed method, an overall drag reduction of 17.65 counts, or 6.4%, was obtained, compared to the initial over-wing configuration, comprising the original wing and baseline engine position. Nonetheless, the best over-wing nacelle design is still 5.58 counts, or 2%, higher in overall drag compared to the baseline under-wing mounted nacelle case.
35.	Xisto, Carlos, 1984, et al. (författare) Analytical model for the performance estimation of pre-cooled pulse detonation turbofan engines 2017 Ingår i: Proceedings of the ASME Turbo Expo. ; 1 Konferensbidrag (refereegranskat)abstract This paper proposes a pulse detonation combustion (PDC) model integrated within Chalmers University' s gas turbine simulation tool GESTPA N (GEneral Stationary and Transient Propulsion ANalsysis). The model will support the development of novel aircraft engine architectures exploiting the synergies between intercooling, aftercooling and PDC. The proposed engine architectures are based on a reference high bypass ratio geared-turbofan engine model with performance levels estimated to be available by year 2050. Parametric studies have been carried out for each proposed advanced architecture, providing engine cycle mid-cruise design point parameters. Design sensitivity studies related to intercooling technology in combination with a PDC are further explored for a number of heat-exchanger design effectiveness values and associated pressure loss levels. The acquired results suggest that the incorporation of PDC technology within a conventional core has the potential to significantly improve engine thermal efficiency. Incorporating intercooling improves the cycle performance for any pre-combustion OPR above 10 and contributes to an increase in specific power over the entire range of OPR. Finally, the results demonstrate that aftercooling the high pressure compressor delivery air further improves core specific power, but cancels out any SFC and thermal efficiency benefits arising from pulse detonation.
36.	Xisto, Carlos, 1984, et al. (författare) Assessment of CO2 and NOx emissions in intercooled pulsed detonation turbofan engines 2018 Ingår i: Proceedings of the ASME Turbo Expo. ; 1 Konferensbidrag (refereegranskat)abstract In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOxand CO2emissions. CO2is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption and reducing engine weight and nacelle drag. A model predicting NOxgeneration per unit of fuel for pulsed detonation combustors, operating with jet-A fuel, is developed and integrated within Chalmers University's gas turbine simulation tool GESTPAN. The model is constructed using CFD data obtained for different combustor inlet pressure, temperature and equivalence ratio levels. The NOxmodel supports the quantification of the trade-off between CO2and NOxemissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.
37.	Xisto, Carlos, 1984, et al. (författare) Assessment of CO2 and NOx emissions in intercooled pulsed detonation turbofan engines 2019 Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 141:1 Tidskriftsartikel (refereegranskat)abstract In the present paper, the synergistic combination of intercooling with pulsed detonation combustion is analyzed concerning its contribution to NOx and CO2 emissions. CO2 is directly proportional to fuel burn and can, therefore, be reduced by improving specific fuel consumption and reducing engine weight and nacelle drag. A model predicting NOx generation per unit of fuel for pulsed detonation combustors, operating with jet-A fuel, is developed and integrated within Chalmers University's gas turbine simulation tool GESTPAN. The model is constructed using CFD data obtained for different combustor inlet pressure, temperature and equivalence ratio levels. The NOx model supports the quantification of the trade-off between CO2 and NOx emissions in a 2050 geared turbofan architecture incorporating intercooling and pulsed detonation combustion and operating at pressures and temperatures of interest in gas turbine technology for aero-engine civil applications.
38.	Xisto, Carlos, 1984, et al. (författare) Design and performance of liquid hydrogen fueled aircraft for year 2050 EIS 2022 Ingår i: 33rd Congress of the international council of the aeronautical sciences. ; 2, s. 1119-1131 Konferensbidrag (refereegranskat)abstract The present paper reports on the investigation of long-range LH2 aircraft concepts for year 2050 entry into service. The paper attempts to identify the limitations set by the LH2 storage technology when targeting typical design payload-range missions. In particular, the paper aims at providing a reasonable estimate of the upper efficiency levels set by low-weight rigid cell foam insulated tank technology, when integrated in a conventionally shaped airframe. Additionally, a sensitivity study on the gravimetric efficiency of the tanks will be carried out, to identify the required roadmap for LH2 storage technology that is compliant with the typical long range mission requirements. Results for the different LH2 aircraft are compared with a year 2020 and year 2050 reference aircraft fueled with conventional jet-A.
39.	Xisto, Carlos, 1984, et al. (författare) The Efficiency of a Pulsed Detonation Combustor-Axial Turbine Integration 2018 Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 82-83, s. 80-91 Tidskriftsartikel (refereegranskat)abstract The paper presents a detailed numerical investigation of a pulsed detonation combustor (PDC) coupled with a transonic axial turbine stage. The time-resolved numerical analysis includes detailed chemistry to replicate detonation combustion in a stoichiometric hydrogen–air mixture, and it is fully coupled with the turbine stage flow simulation. The PDC–turbine performance and flow variations are analyzed for different power input conditions, by varying the system purge fraction. Such analysis allows for the establishment of cycle averaged performance data and also to identify key unsteady gas dynamic interactions occurring in the system. The results obtained allow for a better insight on the source and effect of different loss mechanisms occurring in the coupled PDC–turbine system. One key aspect arises from the interaction between the non-stationary PDC outflow and the constant rotor blade speed. Such interaction results in pronounced variations of rotor incidence angle, penalizing the turbine efficiency and capability of generating a quasi-steady shaft torque.
40.	Zhao, Xin, 1986, et al. (författare) Conceptual Mean-line Design of a Low Pressure Turbine for a Geared Turbofan with Rear Structure Interaction 2019 Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract One of the most important features of a geared turbofan (GTF) is a reduced number of low pressure turbine (LPT) stages resulting from a faster spinning spool. Compared to a direct drive turbofan (DDTF), in which the LPT normally constitutes a considerable part of the engine total weight, from 10% to more than 25%, dependent on the engine bypass ratio (BPR), fewer stages can cut the weight into half or even less for the LPT. With this benefit, the weight of the LPT alone is no longer a dominating factor for the selection of its configuration. To obtain an optimal LPT configuration for a GTF requires a new balance between weight and performance involving both the LPT and the downstream component, the turbine rear structure (TRS). A conceptual design of the LPT for a mid- to long-range GTF is presented here to clarify this new balance. By comparing a range of designs based on different number of stages and turbine hade angles, the selection of the LPT design for the GTF is described. More importantly, interactions between the LPT design and the TRS design are considered. Results indicate that a joint design is necessary as the TRS plays an important role in designing the LPT of a GTF. It is shown that if the LPT design is done in isolation from the TRS design, a 3-stage LPT performs better than a 4-stage design from a fuel burn perspective. However, when the TRS design is considered, the advantage of the 3-stage LPT design is offset by the associated TRS weight and loss increase, compared to the 4-stage LPT design.

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