| 1. |
- Avellan, Rickard, 1976, et al.
(författare)
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Boxprop, a forward-swept joined-blade propeller
- 2013
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Ingår i: ISABE-2013-1108.
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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.
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| 2. |
- Avellan, Rickard, 1976, et al.
(författare)
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Preparing for Proof-of-concept of a Novel Propeller for Open Rotor Engines
- 2015
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Ingår i: ISABE-2015-20097.
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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.
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| 3. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Aerodynamic and aeroacoustic comparison of optimized high-speed propeller blades
- 2018
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Ingår i: 2018 Joint Propulsion Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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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.
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| 4. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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An Optimization Platform for High Speed Propellers
- 2016
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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.
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| 5. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Compact heat exchangers for hydrogen-fueled aero engine intercooling and recuperation
- 2024
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Ingår i: Applied Thermal Engineering. - 1359-4311. ; 243
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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.
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| 6. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine
- 2024
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Ingår i: Applied Thermal Engineering. - 1359-4311. ; 236
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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.
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| 7. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Wake Analysis of an Aerodynamically Optimized Boxprop High Speed Propeller
- 2019
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Ingår i: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 141:9
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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.
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| 8. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Wake and Loss Analysis for a Double Bladed Swept Propeller
- 2016
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Ingår i: Proceedings of ASME Turbo Expo 2016: Turbine Technical Conference and Exposition, Seoul, South Korea, Jun 13-17, 2016. ; 1
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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.
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| 9. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Wake Energy Analysis Method Applied to the Boxprop Propeller Concept
- 2018
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 79, s. 689-700
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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.
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| 10. |
- De Campos, Gustavo Bonolo, et al.
(författare)
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Propulsive efficiency of boundary layer ingestion propellers
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018.
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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.
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