| 1. |
- Andersson, Anton, et al.
(författare)
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Design of a Foiling Optimist
- 2018
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Ingår i: Journal of Sailboat Technology. ; 2018, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- Because of the successful application of hydrofoils on the America's Cup catamarans in the past two campaigns the interest in foiling sailing craft has boosted. Foils have been fitted to a large number of yachts with great success, ranging from dinghies to ocean racers. An interesting question is whether one of the slowest racing boats in the world, the Optimist dinghy, can foil, and if so, at what minimum wind speed. The present paper presents a comprehensive design campaign to answer the two questions. The campaign includes a newly developed Velocity Prediction Program (VPP) for foiling/non-foiling conditions, a wind tunnel test of sail aerodynamics, a towing tank test of hull hydrodynamics and a large number of numerical predictions of foil characteristics. An optimum foil configuration is developed and towing tank tested with satisfactory results. The final proof of the concept is a successful on the water test with stable foiling at a speed of 12 knots.
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| 2. |
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| 3. |
- Zamora, Juan Carlos, et al.
(författare)
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Considerations and consequences of allowing DNA sequence data as types of fungal taxa
- 2018
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Ingår i: IMA Fungus. - : INT MYCOLOGICAL ASSOC. - 2210-6340 .- 2210-6359. ; 9:1, s. 167-185
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Tidskriftsartikel (refereegranskat)abstract
- Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.
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| 4. |
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| 5. |
- Ahlström, Johan, 1990, et al.
(författare)
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Bark as feedstock for dual fluidized bed gasifiers. Operability, efficiency, and economics
- 2019
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 43:3, s. 1171-1190
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Tidskriftsartikel (refereegranskat)abstract
- The demand for biofuels and biochemicals is expected to increase in the future, which will in turn increase the demand for biomass feedstock. Large gasification plants fueled with biomass feedstock are likely to be a key enabling technology in a resource-efficient, bio-based economy. Furthermore, the costs for producing biofuels and biochemicals in such plants could potentially be decreased by utilizing inexpensive low-grade residual biomass as feedstock. This study investigates the usage of shredded tree bark as a feedstock for the production of biomethane in the GoBiGas demonstration plant in Gothenburg, Sweden, based on a 32 MWth industrial dual fluidized bed gasification unit. The plant was operated with bark feedstock for 12 000 hours during the period 2014 to 2018. Data from the measurement campaign were processed using a stochastic approach to establish the plant's mass and energy balances, which were then compared with operation of the plant with wood pellets. For this comparison, an extrapolation algorithm was developed to predict plant performance using bark dried to the same moisture content as wood pellets, ie, 8%w.b. Plant operation with bark feedstock was evaluated for operability, efficiency, and feedstock-related cost. The gas quality achieved during the test period was similar to that obtained for operation with wood pellets. Furthermore, no significant ash sintering or agglomeration problems were observed more than 750 hours of operation. The calculated biomass-to-biomethane efficiency is 43% to 47% (lower heating value basis) for operation with wet bark. However, the predicted biomass-to-biomethane efficiency can be increased to 55%–65% for operation with bark feedstock dried to 8% moisture content, with corresponding feedstock costs in the range of 24.2 to 32.7 EUR/MWh; ie, a cost reduction of about 40% compared with wood pellets.
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| 6. |
- Alamia, Alberto, 1984, et al.
(författare)
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Efficiency Comparison of Large-Scale Standalone, Centralized, and Distributed Thermochemical Biorefineries
- 2017
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Ingår i: Energy Technology. - : Wiley. - 2194-4296 .- 2194-4288. ; 5:8, s. 1435-1448
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.We present a comparison of three strategies for the introduction of new biorefineries: standalone and centralized drop-in, which are placed within a cluster of chemical industries, and distributed drop-in, which is connected to other plants by a pipeline. The aim was to quantify the efficiencies and the production ranges to support local transition to a circular economy based on biomass usage. The products considered are biomethane (standalone) and hydrogen/biomethane and sustainable town gas (centralized drop-in and distributed drop-in). The analysis is based on a flow-sheet simulation of different process designs at the 100MWbiomass scale and includes the following aspects: advanced drying systems, the coproduction of ethanol, and power-to-gas conversion by direct heating or water electrolysis. For the standalone plant, the chemical efficiency was in the range of 78-82.8% LHVa.r.50% (lower heating value of the as-received biomass with 50% wet basis moisture), with a maximum production of 72MWCH4 , and for the centralized drop-in and distributed drop-in plants, the chemical efficiency was in the range of 82.8-98.5% LHVa.r.50% with maximum production levels of 85.6MWSTG and 22.5MWH2 /51MWCH4 , respectively. It is concluded that standalone plants offer no substantial advantages over distributed drop-in or centralized drop-in plants unless methane is the desired product.
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| 7. |
- Alamia, Alberto, 1984, et al.
(författare)
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Performance of large-scale biomass gasifiers in a biorefinery, a state-of-the-art reference
- 2017
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Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 1099-114X .- 0363-907X. ; 41:14, s. 2001-2019
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Tidskriftsartikel (refereegranskat)abstract
- The Gothenburg Biomass Gasification plant (2015) is currently the largest plant in the world producing biomethane (20 MWbiomethane) from woody biomass. We present the experimental data from the first measurement campaign and evaluate the mass and energy balances of the gasification sections at the plant. Measures improving the efficiency including the use of additives (potassium and sulfur), high-temperature pre-heating of the inlet streams, improved insulation of the reactors, drying of the biomass and introduction of electricity as a heat source (power-to-gas) are investigated with simulations. The cold gas efficiency was calculated in 71.7%LHVdaf using dried biomass (8% moist). The gasifier reaches high fuel conversion, with char gasification of 54%, and the fraction of the volatiles is converted to methane of 34%mass. Because of the design, the heat losses are significant (5.2%LHVdaf), which affect the efficiency. The combination of potential improvements can increase the cold gas efficiency to 83.5%LHVdaf, which is technically feasible in a commercial plant. The experience gained from the Gothenburg Biomass Gasification plant reveals the strong potential biomass gasification at large scale.
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| 8. |
- Andersson, L. Robin, et al.
(författare)
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Localized roughness effects in non-uniform hydraulic waterways
- 2021
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Ingår i: Journal of Hydraulic Research. - : Taylor & Francis. - 0022-1686 .- 1814-2079. ; 59:1, s. 100-108
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Tidskriftsartikel (refereegranskat)abstract
- Hydropower tunnels are generally subject to a degree of rock falls. Studies explaining this are scarce and the current industrial standards offer little insight. To simulate tunnel conditions, high Reynolds number flow inside a channel with a rectangular cross-section is investigated using Particle Image Velocimetry and pressure measurements. For validation, the flow is modelled using LES and a RANS approach with k - ε turbulence model. One wall of the channel has been replaced with a rough surface captured using laser scanning. The results indicate flow-roughness effects deviating from the standard non-asymmetric channel flow and hence, can not be properly predicted using spatially averaged relations. These effects manifest as localized bursts of velocity connected to individual roughness elements. The bursts are large enough to affect both temporally and spatially averaged quantities. Both turbulence models show satisfactory agreement for the overall flow behaviour, where LES also provided information for in-depth analysis.
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| 9. |
- Anton, Nicholas, et al.
(författare)
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AXIAL TURBINE DESIGN FOR A TWIN-TURBINE HEAVY-DUTY TURBOCHARGER CONCEPT
- 2018
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Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : ASME Press. - 9780791851005
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Konferensbidrag (refereegranskat)abstract
- In the process of evaluating a parallel twin-turbine pulse-turbocharged concept, the results considering the turbine operation clearly pointed towards an axial type of turbine. The radial turbine design first analyzed was seen to suffer from sub-optimum values of flow coefficient, stage loading and blade speed-ratio. Modifying the radial turbine by both assessing the influence of "trim" and inlet tip diameter all concluded that this type of turbine is limited for the concept. Mainly, the turbine stage was experiencing high values of flow coefficient, requiring a more high flowing type of turbine. Therefore, an axial turbine stage could be feasible as this type of turbine can handle significantly higher flow rates very efficiently. Also, the design spectrum is broader as the shape of the turbine blades is not restricted by a radially fibred geometry as in the radial turbine case. In this paper, a single stage axial turbine design is presented. As most turbocharger concepts for automotive and heavy-duty applications are dominated by radial turbines, the axial turbine is an interesting option to be evaluated for pulse charged concepts. Values of crank-angle-resolved turbine and flow parameters from engine simulations are used as input to the design and subsequent analysis. The data provides a valuable insight into the fluctuating turbine operating conditions and is a necessity for matching a pulse-turbocharged system. Starting on a 1D-basis, the design process is followed through, resulting in a fully defined 3D-geometry. The 3D-design is evaluated both with respect to FEA and CFD as to confirm high performance and durability. Turbine maps were used as input to the engine simulation in order to assess this design with respect to "on-engine" conditions and to engine performance. The axial design shows clear advantages with regards to turbine parameters, efficiency and tip speed levels compared to a reference radial design. Improvement in turbine efficiency enhanced the engine performance significantly. The study concludes that the proposed single stage axial turbine stage design is viable for a pulse-turbocharged six cylinder heavy-duty engine. Taking into account both turbine performance and durability aspects, validation in engine simulations, a highly efficient engine with a practical and realizable turbocharger concept resulted.
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| 10. |
- Anton, Nicholas, et al.
(författare)
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Exhaust volume dependency of turbocharger turbine design for a heavy duty otto cycle engine
- 2017
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Ingår i: Proceedings of the ASME Turbo Expo. - : ASME Press. - 9780791850800
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Konferensbidrag (refereegranskat)abstract
- This study is considering turbocharger turbine performance at "on-engine" conditions with respect to turbine design variables and exhaust manifold volume. The highly unsteady nature of the internal combustion engine will result in a very wide range of turbine operation, far from steady flow conditions. As most turbomachinery design work is conducted at steady state, the influence of the chosen turbine design variables on the crank-angle-resolved turbine performance will be of prime interest. In order to achieve high turbocharger efficiency with the greatest benefits for the engine, the turbine will need high efficiency at the energetic exhaust pressure pulse peak. The starting point for this paper is a target full load power curve for a heavy duty Otto-cycle engine, which will dictate an initial compressor and turbine match. Three radial turbine designs are investigated, differing with respect to efficiency characteristics, using a common compressor stage. The influence of the chosen turbine design variables considering a main contributor to unsteadiness, exhaust manifold volume, is evaluated using 1D engine simulation software. A discussion is held in conjunction with this regarding the efficiency potential of each turbine design and limitations of turbine types.
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