| 31. |
- Rao, Anirudh Narayan, 1985, et al.
(författare)
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Influence of the numerical schemes on the flow states of a simplified heavy vehicle
- 2018
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Ingår i: Proceedings of the International Symposium on Turbulence, Heat and Mass Transfer. - 2377-2816. ; , s. 731-734
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Konferensbidrag (refereegranskat)abstract
- Recent experiments [1, 2] in the wake of a simplified heavy vehicle (also know as a ground transportation system (GTS)) have shown that the flow topology remains invariant over a large range of Reynolds numbers [3.8 × 10 4 − 2.8 × 10 6 ]. This allows numerical techniques such as large eddy simulations (LES) to accurately predict the flow topology at low Reynolds numbers. While LES requires grids of higher spatial resolution; hybrid RANS/LES turbulence models are an alternate choice, where, accurate prediction of the flow is possible on coarser grids ([3, 4]). Numerical simulations are performed using LES and a hybrid turbulence model - partially-averaged Navier–Stokes (PANS) equations at Re H = 3.8 × 10 4 for a unified tractor-trailer geometry to compare the flow topologies in the near wake. The influence of the numerical schemes on the flow topology in the symmetry plane which is susceptible to bi-stable flow is investigated using PANS, and compared with the results from LES.
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| 32. |
- Sarmast, Sasan, et al.
(författare)
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Validation of the actuator line and disc techniques using the New Mexico measurements
- 2016
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Ingår i: Journal of Physics, Conference Series. - : Institute of Physics (IOP). - 1742-6588 .- 1742-6596. ; 753:3
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Tidskriftsartikel (refereegranskat)abstract
- Actuator line and disc techniques are employed to analyse the wake obtained in the New Mexico wind turbine experiment. The New Mexico measurement campaign done in 2014 is a follow-up to the MEXICO campaign, which was completed in 2006. Three flow configurations in axial flow condition are simulated and both computed loads and velocity fields around the rotor are compared with detailed PIV measurements. The comparisons show that the computed loadings are generally in agreement with the measurements under the rotor's design condition. Both actuator approaches under-predicted the loading in the inboard part of blade in stall condition as only 2D airfoil data were used in the simulations. The predicted wake velocities generally agree well with the PIV measurements. In the experiment, PIV measurements are also provided close to the hub and nacelle. To study the effect of hub and nacelle, numerical simulations are performed both in the presence and absence of the hub geometry. This study shows that the large hub used in the experiment has only small effects on overall wake behaviour.
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| 33. |
- 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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| 34. |
- Grönstedt, Tomas, 1970, et al.
(författare)
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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.
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| 35. |
- Gullberg, Peter, 1983, et al.
(författare)
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Axial fan performance predictions in CFD, comparison of MRF and sliding mesh with experiments
- 2011
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627. ; 2011
-
Tidskriftsartikel (refereegranskat)abstract
- Underhood Thermal Management has become an important topic for the majority of automotive OEM's. To keep combustion engines cool and manage waste heat efficiently is an important part in the design of vehicles with low fuel consumption. To be able to predict cooling performance and underhood airflow with good precision within a virtual design process, it is of utmost importance to model and simulate the cooling fan efficiently and accurately, and this has turned out to be challenging. Simulating the cooling fan in a vehicle installation involves capturing complex fluid dynamic interaction between rotating blades and stationary objects in the vicinity of the fan. This interaction is a function of fan rotation rate, fan blade profile, upstream and downstream installation components. The flow is usually highly turbulent and small geometry details, like the distance between the blade tip and the fan shroud, have strong impact on the fan performance characteristics. Fan installations therefore have a large influence on cooling performance which the fan data from the supplier cannot capture. Improved simulation capabilities in this area are critical for optimizing the design of energy efficient vehicles since the performance of these fans, which provide airflow to the heat exchangers used for engine cooling and HVAC system operation, have a big impact on the vehicles' overall energy efficiency. This paper presents a comparison of two methodologies for simulating fan air flows. Multiple Reference Frame (MRF) and Sliding Mesh (SM) techniques are applied for a typical heavy duty truck fan. Simulation results are compared to experimental data obtained in a fan test rig with representation of a typical truck fan installation, including fan shroud, ring, seal and an engine silhouette downstream. Results of MRF simulations are known to be sensitive to the MRF domain, which is highly constrained in tight fan installations. For typical truck installations, SM provides a more robust alternative, and better accuracy than MRF in the transitional and radial regime of the fan curve.
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| 36. |
- Kyprianidis, Konstantinos, et al.
(författare)
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Dynamic performance investigations of a turbojet engine using a cross-application visual oriented platform
- 2008
-
Ingår i: Aeronautical Journal. - 0001-9240. ; 112:1129, s. 161-169
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents the development of visual oriented tools for the dynamic performance simulation of a turbojet engine using a cross-application approach. In particular, the study focuses on the feasibility of developing simulation models using different programming environments and linking them together using a popular spreadsheet program. As a result of this effort, a low fidelity cycle program has been created, capable of being integrated with other performance models. The amount of laboratory sessions required for student training during an educational procedure, for example for a course in gas turbine performance simulation, is greatly reduced due to the familiarity of most students with the spreadsheet software. The model results have been validated using commercially available gas turbine simulation software and experimental data from open literature. The most important finding of this study is the capability of the program to link to aircraft performance models and predict the transient working line of the engine for various initial conditions in order to dynamically simulate flight phases including take-off and landing.
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| 37. |
- Kyprianidis, Konstantinos, et al.
(författare)
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Multi-disciplinary Analysis of a Geared Fan Intercooled Core Aero-Engine
- 2013
-
Ingår i: <em><em>Proc. ASME</em>.</em> 55133; Volume 2: Aircraft Engine; Coal, Biomass and Alternative Fuels; Cycle Innovations, V002T07A027. GT2013-95474. - 9780791855133
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Konferensbidrag (refereegranskat)abstract
- Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, as well as the reduction of engine nacelle drag and weight. One alternative design approach to improving specific fuel consumption is to consider a geared fan combined with an increased overall pressure ratio intercooled core performance cycle. Thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is very little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to analyse the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption.With minimum mission fuel in mind, the results indicate as optimal values a pressure ratio split exponent of 0.38 and an intercooler mass flow ratio just below 1.2 at hot-day top of climb conditions. At ISA mid-cruise conditions a specific thrust of 86m/s, a jet velocity ratio of 0.83, an intercooler effectiveness of 55% and an overall pressure ratio value of 76 are likely to be a good choice. A 70,000lbf intercooled turbofan engine is large enough to make efficient use of an all-axial compression system, particularly within a geared fan configuration, but intercooling is perhaps more likely to be applied to even larger engines.The proposed optimal jet velocity ratio is actually higher than the value one would expect by using standard analytical expressions primarily because this design variable affects core efficiency at mid-cruise due to a combination of several different subtle changes to the core cycle and core component efficiencies at this condition. Analytical expressions do not consider changes in core efficiency and the beneficial effect of intercooling on transfer efficiency, nor account for losses in the bypass duct and jet pipe, whilst a relatively detailed engine performance model such as the one utilised in this study does.Mission fuel results from a surrogate model are in good agreement with the results obtained from a rubberised-wing aircraft model for some of the design parameters. This indicates that it is possible to replace an aircraft model with specific fuel consumption and weight penalty exchange rates. Nevertheless, drag count exchange rates have to be utilised to properly assess changes in mission fuel for those design parameters that affect nacelle diameter.
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| 38. |
- Lundbladh, Anders, 1964, et al.
(författare)
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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.
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| 39. |
- Sjögren, Oliver, 1993, et al.
(författare)
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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.
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| 40. |
- Thulin, Oskar, 1987, et al.
(författare)
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A Mission Assessment of Aero Engine Losses
- 2015
-
Ingår i: ISABE-2015-20121.
-
Konferensbidrag (refereegranskat)abstract
- A detailed and systematic loss breakdown of a direct drive two-spool turbofan aero engine integrated to an aircraft corresponding to a technology level of year 2020is produced from engine mission point performance simulations. The analysis includes the fundamental mission points throughout a commercial aircraft mission. The breakdown also incorporates the inherent effects of the propulsion system such as engine weight and nacelle drag. A new term, installed rational efficiency, is proposed to fully assess the performance of the propulsion subsystem. Combining the detailed component loss analysis with the assessment of the installation effects provides a systematic as well as effective way of analyzing the full impact of an aircraft component, likethe engine subsystem, on the aircraft. This can be used to truly assess the performance of one propulsion unitcompared to another.
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