| 1. |
- Avellan, Rickard, 1976, et al.
(author)
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Preparing for Proof-of-concept of a Novel Propeller for Open Rotor Engines
- 2015
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In: ISABE-2015-20097.
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Conference paper (peer-reviewed)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.
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| 2. |
- Capitao Patrao, Alexandre, 1988, et al.
(author)
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Aerodynamic and aeroacoustic comparison of optimized high-speed propeller blades
- 2018
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In: 2018 Joint Propulsion Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Conference paper (peer-reviewed)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.
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| 3. |
- Capitao Patrao, Alexandre, 1988, et al.
(author)
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An Optimization Platform for High Speed Propellers
- 2016
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Conference paper (other academic/artistic)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.
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| 4. |
- Capitao Patrao, Alexandre, 1988, et al.
(author)
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Wake Analysis of an Aerodynamically Optimized Boxprop High Speed Propeller
- 2019
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In: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 141:9
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Journal article (peer-reviewed)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.
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| 5. |
- Capitao Patrao, Alexandre, 1988, et al.
(author)
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Wake and Loss Analysis for a Double Bladed Swept Propeller
- 2016
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In: Proceedings of ASME Turbo Expo 2016: Turbine Technical Conference and Exposition, Seoul, South Korea, Jun 13-17, 2016. ; 1
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Conference paper (peer-reviewed)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.
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| 6. |
- Capitao Patrao, Alexandre, 1988, et al.
(author)
-
Wake Energy Analysis Method Applied to the Boxprop Propeller Concept
- 2018
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In: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 79, s. 689-700
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Journal article (peer-reviewed)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.
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| 7. |
- De Campos, Gustavo Bonolo, et al.
(author)
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Propulsive efficiency of boundary layer ingestion propellers
- 2018
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In: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018.
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Conference paper (peer-reviewed)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.
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| 8. |
- Grönstedt, Tomas, 1970, et al.
(author)
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DN Debatt. "Mellanlandning kan halvera utsläppen från Thailandsresa"
- 2018
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In: Dagens Nyheter. ; , s. 5-
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Journal article (pop. science, debate, etc.)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.
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| 9. |
- Grönstedt, Tomas, 1970, et al.
(author)
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Flygforskare: "Våra beräkningar bygger på detaljerade modeller"
- 2018
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In: Dagens Nyheter (DN). - 1101-2447.
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Journal article (pop. science, debate, etc.)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.
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| 10. |
- Grönstedt, Tomas, 1970, et al.
(author)
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Ultra low emission technology innovations for mid-century aircraft turbine engines
- 2016
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In: ASME Turbo EXPO 2016, Seoul, June 13-17, South Korea. - 9780791849743 ; 3:GT2016-56123
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Conference paper (peer-reviewed)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.
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| 11. |
- Lundbladh, Anders, 1964, et al.
(author)
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High Power Density Work Extraction from Turbofan Exhaust Heat
- 2015
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In: ISABE-2015-20101.
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Conference paper (peer-reviewed)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.
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| 12. |
- Lundbladh, Anders, 1964, et al.
(author)
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Installation effects for ultra-high bypass engines
- 2017
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In: International Society of Air-breathing Engines (ISABE).
-
Conference paper (peer-reviewed)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.
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| 13. |
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| 14. |
- Sandberg, Marcus, et al.
(author)
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A knowledge-based master model approach exemplified with jet engine structural design
- 2017
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In: Computers in Industry. - : Elsevier BV. - 0166-3615 .- 1872-6194. ; 85, s. 31-38
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Journal article (peer-reviewed)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.
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| 15. |
- Xisto, Carlos, 1984, et al.
(author)
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Analytical model for the performance estimation of pre-cooled pulse detonation turbofan engines
- 2017
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In: Proceedings of the ASME Turbo Expo. ; 1
-
Conference paper (peer-reviewed)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.
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| 16. |
- Xisto, Carlos, 1984, et al.
(author)
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Assessment of CO2 and NOx emissions in intercooled pulsed detonation turbofan engines
- 2018
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In: Proceedings of the ASME Turbo Expo. ; 1
-
Conference paper (peer-reviewed)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.
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| 17. |
- Xisto, Carlos, 1984, et al.
(author)
-
Assessment of CO2 and NOx emissions in intercooled pulsed detonation turbofan engines
- 2019
-
In: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 141:1
-
Journal article (peer-reviewed)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.
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| 18. |
- Xisto, Carlos, 1984, et al.
(author)
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The Efficiency of a Pulsed Detonation Combustor-Axial Turbine Integration
- 2018
-
In: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 82-83, s. 80-91
-
Journal article (peer-reviewed)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.
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| 19. |
- Zhao, Xin, 1986, et al.
(author)
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Conceptual Mean-line Design of a Low Pressure Turbine for a Geared Turbofan with Rear Structure Interaction
- 2019
-
Conference paper (other academic/artistic)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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