| 1. |
- Andersson, H.M., et al.
(författare)
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Application of digital speckle photography to measure thickness variations in the vacuum infusion process
- 2003
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 24:3, s. 448-455
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Tidskriftsartikel (refereegranskat)abstract
- A new method to measure the movement of the flexible bag used in vacuum infusion is presented. The method is based on an in-house developed stereoscopic digital speckle photography system (DSP). The advantage with this optical method, which is based on cross-correlation, is that the deflection of a large area can be continuously measured with a great accuracy (down to 10 μm. The method is at this stage most suited for research but can in the long run also be adopted in production control and optimization. By use of the method it was confirmed that a ditch is formed at the resin flow front and that there can be a considerable and seemingly perpetual compaction after complete filling. The existence of the ditch demonstrates that the stiffness of the reinforcement can be considerably reduced when it is wetted. Hence, the maximum fiber volume fraction can be larger than predicted from dry measurements of preform elasticity. It is likely that the overall thickness reduction after complete filling emanates from lubrication of the fibers combined with an outflow of the resin. Besides, the cross-linking starts and the polymer shrinks. Hence, the alteration in height will continue until complete cross-linking is reached.
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| 2. |
- Andersson, Magnus, et al.
(författare)
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Development of guidelines for the vacuum infusion process
- 2000
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Ingår i: Proceedings of the 8th International Conference on Fibre Reinforced Composites, FRC 2000. - Cambridge : Woodhead Publishing Materials. - 1855735504 ; , s. 113-120
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Konferensbidrag (refereegranskat)abstract
- The current trend towards increased use of vacuum infusion moulding for large surface area parts has increased the interest for an advanced modelling of the process. This paper presents a detailed experimental investigation of laminate thickness and out-of-plane flow front shape during impregnation of high permeability reinforcement on top of a non-crimp fabric reinforcement lay-up. The goal with the experiments is to increase the understanding of the process and to provide accurate data that can later be used for validation of numerical models. The laminate thickness was measured during impregnation with a stereoscopic digital speckle photography system and the flow front shape was determined by tracking of colour marks in the stacking. The laminate lay-ups studied are different combinations of non-crimp fabrics and flow layers while the resin used was a polyester developed specifically for vacuum infusion moulding. Results are presented both for the instantaneous thickness and the flow front shape for several different material combinations. It was found that the skewness of the flow front became more pronounced with increasing number of flow layers when the number of non-crimp fabric layers was kept constant. As a first step towards a complete numerical model of the impregnation process a simplified model for the compressibility and a proven model for permeability was implemented in a commercial CFD package that can handle moving boundaries and moving flow fronts. Only a qualitative comparison with experiments was done but the conclusion was that the overall behaviour of the model was encouraging. A validation of the numerical model based on the measurements in this paper is under development.
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| 3. |
- Andersson, Magnus, et al.
(författare)
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Flow-enhancing layers in the vacuum infusion process
- 2002
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 23:5, s. 895-901
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Tidskriftsartikel (refereegranskat)abstract
- The current trend towards increased use of vacuum infusion molding for large surface-area parts has increased the interest in an advanced modeling of the process. Because the driving pressure is limited to 1 atmosphere, it is essential to evaluate possible ways to accelerate the impregnation. One way of doing this is to use layers of higher permeability within the reinforcing stack, i.e. flow-enhancing layers. We present an experimental investigation of the flow front shape when using such layers. The through-thickness flow front was observed by making a number of color marks on the glass-mats forming the reinforcing stack, which became visible when the resin reached their position. The in-plane flow front was derived from observations of the uppermost layer. It turned out that existing analytical models agree very well with the experiments if effective permeability data is used, that is, permeability obtained from vacuum infusions. However, the fill-time was nearly twice as long as predicted from permeability data obtained in a stiff tool. This rather large discrepancy may be due to certain features of a flexible mold half and is therefore a topic for further research. The lead-lag to final thickness ratio is dependent on the position of the flow front and ranges form 5 to 10 for the cases tested. Interestingly the lead-lag has a miximum close to the inlet.
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| 4. |
- Andersson, Magnus, et al.
(författare)
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Numerical model for vacuum infusion manufacturing of polymer composites
- 2003
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Ingår i: International journal of numerical methods for heat & fluid flow. - : Emerald. - 0961-5539 .- 1758-6585. ; 13:3, s. 383-394
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Tidskriftsartikel (refereegranskat)abstract
- The focus is set on the development and evaluation of a numerical mgodel describing the impregnation stage of a method to manufacture fibre reinforced polymer composites, namely the vacuum infusion process. Examples of items made with this process are hulls to sailing yachts and containers for the transportation industry. The impregnation is characterised by a full 3D flow in a porous medium having an anisotropic, spatial- and time-dependent permeability. The numerical model has been implemented in a general and commercial computational fluid dynamic software through custom written subroutines that: couple the flow equations to the equations describing the stiffness of the fibre reinforcement; modify the momentum equations to account for the porous medium flow; remesh the computational domain in each time step to account for the deformation by pressure change. The verification of the code showed excellent agreement with analytical solutions and very good agreement with experiments. The numerical model can easily be extended to more complex geometry and to other constitutive equations for the permeability and the compressibility of the reinforcement.
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| 5. |
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| 6. |
- Bergström, John, et al.
(författare)
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Estimation of numerical accuracy for the flow field in a draft tube
- 1999
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Ingår i: International journal of numerical methods for heat & fluid flow. - : Emerald. - 0961-5539 .- 1758-6585. ; 9:4, s. 472-486
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Tidskriftsartikel (refereegranskat)abstract
- The potential for overall efficiency improvements of modern hydro power turbines is a few percent. A significant part of the losses occurs in the draft tube. To improve the efficiency by analysing the flow in the draft tube, it is therefore necessary to do this accurately, i.e. one must know how large the iterative and the grid errors are. This was done by comparing three different methods to estimate errors. Four grids (122,976 to 4,592 cells) and two numerical schemes (hybrid differencing and CCCT) were used in the comparison. To assess the iterative error, the convergence history and the final value of the residuals were used. The grid error estimates were based on Richardson extrapolation and least square curve fitting. Using these methods we could, apart from estimate the error, also calculate the apparent order of the numerical schemes. The effects of using double or single precision and changing the under relaxation factors were also investigated. To check the grid error the pressure recovery factor was used. The iterative error based on the pressure recovery factor was very small for all grids (of the order 10-4 percent for the CCCT scheme and 10-10percent for the hybrid scheme). The grid error was about 10 percent for the finest grid and the apparent order of the numerical schemes were 1.6 for CCCT (formally second order) and 1.4 for hybrid differencing (formally first order). The conclusion is that there are several methods available that can be used in practical simulations to estimate numerical errors and that in this particular case, the errors were too large. The methods for estimating the errors also allowed us to compute the necessary grid size for a target value of the grid error. For a target value of 1 percent, the necessary grid size for this case was computed to 2 million cells.
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| 7. |
- Bergström, John, et al.
(författare)
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Time-phase averaging for the approximate solution of the flow in a hydraulic turbine
- 1999
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Ingår i: Proceedings of ASME/JSME FEDSM'99. - : American Society of Mechanical Engineers.
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Konferensbidrag (refereegranskat)abstract
- The refurbishment of old hydropower installations and the continuos development of new installations has increased the interest for better design tools to improve their efficiency. Computational fluid dynamics has been used with great success to improve the design of the runner. However, extensive model testing has been necessary to improve the design of the surrounding waterways. Even after testing, some uncertainty has remained concerning the difference between the model scale and the full scale turbine system. The current trend is therefore to include as much as possible of the water conduits with a simultaneous solution of the flow in the turbine runner in an effort to reduce the need for model testing. However, if high numerical accuracy is required the number of mesh points for a complete model of the turbine system has to be at least 10^7. The mesh size together with the need for a time dependent mesh in the runner makes it unlikely that a full simulation with a rotating runner and advanced turbulence modeling will be possible within the next several years, even if the most optimistic estimate of future computer capacity are taken into account. It is therefore of great interest to find new approximations that will make a more refined analysis of the waterways external to the runner possible.In this paper we present a model for the runner that preserves any flow non-uniformity existing at the inlet of the runner in a realistic way through the runner. This has enabled a complete analysis of the interaction of the flow through the penstock, spiral casing and guide vanes with the flow in the draft tube. The mesh requirement and the computational time is considerably reduced compared to a full simulation with a sliding mesh model for the runner. The main drawback with the new model is believed to be that the blade wakes are averaged out of the problem.The model we propose is based on a time-phase averaging technique. The essence of the model is similar to the time averaging technique used by Adamczyk (Adamczyk, 1985), but with different averaging time and different mathematical notation that makes it possible to use the model in a general case, i.e. both for axial and radial machines. A phase function is central to the technique and is introduced for weighting in the averaging procedure. The phase function makes it possible to time average the flow inside a runner. It is constructed with generalised functions and a geometrical description of the suction and pressure side of a runner blade at a reference position. Exact equations for the time-phase averaged variables are derived by a formal time-phase averaging of the governing equations. Some of the terms are accounted for in an approximate way in the present simulation but it is possible to calculate better approximations with a simulation of an isolated runner in a rotating coordinate system. However, even with the crude approximations that we have used the simulation produces realistic results for the particle paths through the runner.
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| 8. |
- Burman, Jörgen, et al.
(författare)
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Assessment of response surface-based optimization techniques unsteady flow around bluff bodies
- 2002
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Ingår i: A collection of technical papers. - Reston, Va. : American Institute of Aeronautics and Astronautics, AIAA. - 1563475502
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Konferensbidrag (refereegranskat)abstract
- The shape of a trapezoidal obstacle immersed in a 2D unsteady, viscous flow is optimized by response surface (RS) techniques based on combined criteria of minimum total drag and maximum mixing efficacy. Time-dependent Navier-Stokes computations are conducted to supply the database. In order to address the issues related to noise, an outlier analysis based on iteratively re-weighted least square (IRLS) method is applied. The results indicate that optimum designs having a low mean drag coefficient tend to be square-shaped, while designs having a large value of the mixing effectiveness are more trapezoidally-shaped. Both RS and IRLS models yield consistent designs, indicating that the present task is well handled by the techniques employed. In addition, the RS methodology is used to identify domains within the design space within which all designs are, for practical purpose, acceptable.
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| 9. |
- Burman, Jörgen, et al.
(författare)
-
Development of a blade geometry definition with implicit design variables
- 2000
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Ingår i: AIAA Paper 00-671. - : American Institute of Aeronautics and Astronautics, AIAA.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a method to create 3-dimensional blade geometries defined in terms of stacked profiles where each profile is described by four NURBS curves. The NURBS representations of the profiles are attractive since they can be exchanged with CAD/CAM systems and grid generators. The blade profiles are defined in terms of traditional design variables, e.g. maximum thickness and camber. A numerical optimisation loop is then used to adjust the basic parameters of the NURBS curves until the requested values of the traditional design variables are obtained. Normally the number of traditional design variables is less than the number of NURBS parametersI.t has therefore been necessaryt o define additional constraints that make the shape corresponding to a given set of traditional design variables unique.
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| 10. |
- Burman, Jörgen, et al.
(författare)
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Influence from numerical noise in the objective function for flow design optimisation
- 2001
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Ingår i: International journal of numerical methods for heat & fluid flow. - : Emerald. - 0961-5539 .- 1758-6585. ; 11:1, s. 6-19
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Tidskriftsartikel (refereegranskat)abstract
- The overall pressure drop in an axisymmetric contraction is minimised using two different grid sizes. The transition region was parameterised with only two design variables to make it possible to create surface plots of the objective function in the design space, which were based on 121 CFD calculations for each grid. The coarse grid showed to have significant numerical noise in the objective function while the finer grid had less numerical noise. The optimisation was performed with two methods, a Response Surface Model (RSM) and a gradient-based method (the Method of Feasible Directions) to study the influence from numerical noise. Both optimisation methods were able to find the global optimum with the two different grid sizes (the search path for the gradient-based method on the coarse grid was able to avoid the region in the design space containing local minima). However, the RSM needed fewer iterations in reaching the optimum. From a grid convergence study at two points in the design space the level of noise appeared to be sufficiently low, when the relative step size is 10-4 for the finite difference calculations, to not influence the convergence if the errors are below 5 per cent for this contraction geometry.
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| 11. |
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| 12. |
- Carlsson, Per, et al.
(författare)
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Comparison and validation of gas phase reaction schemes for black liquor gasification modeling
- 2008
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Ingår i: Conference Proceedings 2008 AiChE annual meeting.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Pressurized Entrained-flow High Temperature Black Liquor Gasification (PEHT-BLG) is a potential substitute or complement to the recovery boiler traditionally used for the recovery of chemicals and energy in black liquor in the Kraft pulping process. Black liquor consists of roughly 30 % moisture, 35 % inorganic pulping chemicals and 35 % combustible material (i.e. lignin). The PEHT-BLG technology can give an increase in total energy efficiency of the mill and provide new products with high added value, such as green motor fuels. The main parts of the recovery unit in the process are; a slagging refractory lined entrained-flow gasification reactor, with a gas assisted burner nozzle producing small black liquor droplets, used for direct gasification of the black liquor at about 1000 °C to produce a ‘raw' syngas and a liquid smelt containing mainly Na2CO3 and Na2S; a quench cooler beneath the reactor where the product gas and smelt are separated and the smelt is dissolved in water forming green liquor; a counter current condenser (CCC) that cools the syngas and condenses water vapor and any volatile and tar species that may be present. The heat recovered from the gas condensation is used to generate low/medium pressure steam that can be used in the pulp and paper process. Furthermore, the chemicals in the green liquor are recovered as cooking chemicals in the downstream processing. Due to lack of demonstration of long term operation of the technology, a development (pilot) plant for PEHT-BLG (named DP-1) with a capacity of 20 tones dry solids/24h is in operation by the technology vendor Chemrec AB at the Energy Technology Centre in Piteå, Sweden. An important tool for reduction of the technical risk associated with scale up of new technology is a comprehensive CFD model for the PEHT-BLG reactor. The current model includes drying, pyrolysis, char gasification and smelt formation of black liquor droplets as well as a simplified gas phase reaction mechanism. The current model has been validated against the outlet gas composition after the Counter Current Condenser (CCC). The model predicted a CO / CO2 ratio that was approximately 50% higher compared to the measurements. However, it is possible that the well known water-gas shift reaction is active in the quench and this could explain that the experimentally determined gas composition after the CCC differs from the computational results at the outlet from the hot zone. Recently, in-situ measurements have been performed in the DP-1 reactor and a further validation of the model has been made possible. The measurements have been performed by sampling gas with a water-cooled suction probe from the lower part of the hot zone, followed by offline gas analyses. The present paper investigates the difference between the current CFD-model and a modified version with an additional CO + O2 reaction added to the simplified gas phase reaction scheme. The simulation results are compared against measurements obtained by the gas sampling probe in the DP-1 reactor. The results suggest that by implementing the additional CO + O2 reaction local flame temperature was increased significantly. However, the effect on volume average and outlet gas temperature was minimal.The results also showed that the CO + O2 reaction had very little effect on outlet gas composition when the reaction was implemented in the PEHT-BLG-CFD model
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| 13. |
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| 14. |
- Carlsson, Per, et al.
(författare)
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Computational fluid dynamics simulations of raw gas composition from a black liquor gasifier : comparison with experiments
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 25:9, s. 4122-4128
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Tidskriftsartikel (refereegranskat)abstract
- Pressurized entrained flow high temperature black liquor gasification can be used as a complement or a substitute to the Tomlinson boiler used in the chemical recovery process at kraft pulp mills. The technology has been proven on the development scale, but there are still no full scale plants. This work is intended to aid in the development by providing computational tools that can be used in scale up of the existing technology. In this work, an existing computational fluid dynamics (CFD) model describing the gasification reactor is refined. First, one-dimensional (1D) plug flow reactor calculations with a comprehensive reaction mechanism are performed to judge the validity of the global homogeneous reaction mechanism used in the CFD simulations in the temperature range considered. On the basis of the results from the comparison, an extinction temperature modification of the steam-methane reforming reaction was introduced in the CFD model. An extinction temperature of 1400 K was determined to give the best overall agreement between the two models. Next, the results from simulations of the flow in a 3 MW pilot gasifier with the updated CFD model are compared to experimental results in which pressure, oxygen to black liquor equivalence ratio, and residence time have been varied. The results show that the updated CFD model can predict the main gas components (H2, CO, CO2) within an absolute error of 2.5 mol %. CH4 can be predicted within an absolute error of 1 mol %, and most of the trends when process conditions are varied are captured by the model.
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| 15. |
- Carlsson, Per, et al.
(författare)
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Experimental investigation of an industrial scale black liquor gasifier : 1. Influence of reactor operation parameters on product gas composition
- 2010
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 89:12, s. 4025-4034
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Tidskriftsartikel (refereegranskat)abstract
- A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient fuel synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO2, CO, H2, CH4, H2S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.
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| 16. |
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| 17. |
- Carlsson, Per, et al.
(författare)
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Experiments and mathematical models of black liquor gasification – influence of minor gas components on temperature, gas composition, and fixed carbon conversion
- 2010
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Ingår i: TAPPI Journal. - 0734-1415. ; 9:9, s. 15-24
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Forskningsöversikt (refereegranskat)abstract
- In this work, predictions from a reacting Computational Fluid Dynamics (CFD) model of a gasification reactor are compared to experimentally obtained data from an industrial pressurized black liquor gasification plant. The data consists of gas samples taken from the hot part of the gasification reactor using a water cooled sampling probe. During the considered experimental campaign, the oxygen-to-black liquor equivalence ratio (λ) was varied in three increments, which resulted in a change in reactor temperature and gas composition. The presented numerical study consists of CFD and thermodynamic equilibrium calculations in the considered λ-range using boundary conditions obtained from the experimental campaign. Specifically, the influence of methane concentration on the gas composition is evaluated using both CFD and thermodynamic equilibrium. The results show that the main gas components (H2, CO, CO2) can be predicted within a relative error of 5% using CFD if the modeled release of H2S and CH4 are specified a priori. In addition, the calculations also show that the methane concentration has large influence on the reactor outlet temperature and final carbon conversion.
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| 18. |
- Carlsson, Per, et al.
(författare)
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High-speed imaging of biomass particles heated with a laser
- 2013
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Ingår i: Journal of Analytical and Applied Pyrolysis. - : Elsevier BV. - 0165-2370 .- 1873-250X. ; 103, s. 278-286
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Tidskriftsartikel (refereegranskat)abstract
- In this work two types of lignocellulosic biomass particles, European spruce and American hardwood (particle sizes from 100 μm to 500 μm) were pyrolysed with a continuous wave 2 W Nd:YAG laser. Simultaneously a high-speed camera was used to capture the behavior of the biomass particle as it was heated for about 0.1 s. Cover glasses were used as a sample holder which allowed for light microscope studies after the heating. Since the cover glasses are not initially heated by the laser, vapors from the biomass particle are quenched on the glass within about 1 particle diameter from the initial particle. Image processing was used to track the contour of the biomass particle and the enclosed area of the contour was calculated for each frame.The main observations are: There is a significant difference between how much surface energy is needed to pyrolyses the spruce (about 75% more) compared to the hardwood. The oil-like substance which appeared on the glass during the experiment is solid at room temperature and shows different levels of transparency. A fraction of this substance is water soluble. A brownish coat is seen on the unreacted biomass. The biomass showed insignificant swelling as it was heated. The biomass particle appears to melt and boil at the front that is formed between the laser beam and the biomass particle. The part of the particle that is not subjected to the laser beam seems to be unaffected.
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| 19. |
- Carlsson, Per, et al.
(författare)
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Spatially resolved measurements of gas composition in a pressurised black liquor gasifier
- 2009
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Ingår i: Environmental Progress & Sustainable Energy. - : Wiley. - 1944-7442 .- 1944-7450. ; 28:3, s. 316-323
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Tidskriftsartikel (refereegranskat)abstract
- Black liquor gasification is a new process for recovery of energy and chemicals in black liquor from the Kraft pulping process. The process can be combined with catalytic conversion of syngas into motor fuels. The potential for motor fuel production from black liquor in Sweden is to replace about 25% of the current consumption ofgasoline and diesel. For Finland the figure is even higher while for Canada it is about 14% and for the USA about 2%. © 2009 American Institute of Chemical Engineers Environ Prog, 28: 316-323, 2009.
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| 20. |
- Chishty, Muhammad Aqib, et al.
(författare)
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Numerical simulation of a biomass cyclone gasifier : Effects of operating conditions on gasifier performance
- 2021
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- In Nordic countries, biomass gasification in a cyclone gasifier combined with a gas engine has been employed to generate small scale heat and power. Numerical simulations were carried out to analyze the effect of different operating conditions on the functioning of the gasifier. Reynolds-Averaged Navier-Stokes equations are solved together with the eddy-break up combustion model in conjunction with a modified k − ϵ model to predict the temperature and the flow field inside the gasifier. Results were compared with the experimental measurements in a 4.4 MW cyclone gasifier constructed by Meva Energy AB at Hortlax, Piteå, Sweden. The predicted results were in good agreement with the experimental data and the model provides detailed information about the gas compositions, cold gas efficiency and temperature field. Furthermore, the model allows different operating scenarios to be examined in an efficient manner such as the number of inlets, fuel to air velocity difference (slip-velocity) and moisture content in the fuel feedstock. The cold gas efficiency, composition of product gases and outlet temperature were monitored for each test case. These findings help to understand the importance of geometry modification, feedstock contents and make it possible to scale-up the gasifier for future applications.
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| 21. |
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| 22. |
- Dal Belo Takehara, Marcelo, et al.
(författare)
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Effect of acoustic perturbation on particle dispersion in a swirl-stabilized pulverized fuel burner: Cold-flow conditions
- 2022
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- Inter-particle distance and particle dispersion during gasification of biomass have been found to significantly affect soot emission. Consequently, enhanced particle dispersion decreases energy losses and the risk for blockages of downstream equipment, increasing the efficiency and reliability of entrained flow reactors (EFRs). In this work, we investigated the interactions between imposed acoustic oscillations and particle dispersion under non-reacting conditions in a co-axial burner for a lab-scale EFR. A flow of air, laden with pulverized stem wood particles (Norwegian Spruce) of three different sizes (63–112 μm, 200–250 μm, and 500–600 μm), was forced axially through the burner center tube at Reynolds numbers ranged from 800 to 1700, and loading ratio of 0.7–4.2. The influences on particle dispersion from variations of the Strouhal number (0.12–0.6), the pressure amplitude at synthetic jet cavity (0.5–4.0 kPap-p), the swirl number (0–2.3), and the center jet velocity (1.9–3.9 m s−1) were investigated. Post-processed shadowgraph images revealed the influence of acoustic perturbations, which generate large structures with high particle concentration for both swirling and non-swirling conditions. Time-averaged contour maps showed a significantly higher particle dispersion, quantified as dispersion angle, for higher values of forcing amplitude and swirl numbers, with a stronger influence from the forcing amplitude, especially at lower Stokes number.
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| 23. |
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| 24. |
- Dal Belo Takehara, Marcelo, 1987-, et al.
(författare)
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Investigation of oxygen-enriched biomass flames in a lab-scale entrained flow reactor
- 2024
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Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 366
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen-enriched air combustion of pulverized biomass fuel is an effective method to improve char combustion and improve flame stability. Moreover, understanding the impact of O2 addition is an important step toward oxyfuel combustion, one of the most promising technologies for bioenergy with carbon capture and storage (BECCS). Our previous studies focused on flow manipulation methods, e.g., swirling co-flow and acoustic forcing, to enhance particle dispersion during biomass combustion and gasification. This work aims to extend the understanding of the effect of different manipulation methods on oxygen-enriched combustion at different levels in a lab-scale entrained flow reactor. This methodology combines the analysis of visible flame characteristics, CO and NO gas emissions, and coarse particle emissions characterization with thermogravimetric analysis and particle size distribution by dynamic imaging. The results indicated that oxygen-enriched combustion leads to lower liftoff distance and higher flame brightness. Moreover, oxygen-enriched combustion presented coarse particle emissions with finer particle size distribution and lower carbon content. The acoustic forcing further decreased the flame liftoff and decreased CO emissions, increasing combustion efficiency under conditions with similar equivalence ratios and lower momentum flux at the secondary air.
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| 25. |
- Dal Belo Takehara, Marcelo, 1987-
(författare)
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Pulverized biomass combustion and gasification : Experimental study of the effects of acoustic forcing on flame and fuel conversion
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of by-products from forestry and agricultural sectors can increase the bioenergy share for heat/power production and industrial processes. Moreover, the integration with carbon capture technologies has a significant potential for CO2 reduction with BECCS (bioenergy with carbon capture and storage) technologies. Entrained flow reactors (EFRs) are commonly applied in the direct combustion and gasification of pulverized fuels. In both technologies, particle-laden flow characteristics can significantly influence the reactor operation, with an impact on performance and emissions. This thesis investigates a broad range of particle flow parameters in EFRs, with an experimental analysis combining high-speed imaging methods with sampling techniques. A comprehensive analysis was carried out using different biomass feedstocks (sawdust, pine bark, and rice husk), operating conditions (non-reacting, air and oxygen-enriched combustion, and gasification), and flow manipulation techniques (swirling flow and acoustic forcing).The latter technique, acoustic forcing, resulted in a high potential for soot reduction in previous experiments when applied to biomass injection in small lab-scale reactors under laminar conditions. Soot emissions represent important environmental concerns and a major technical problem due to the required downstream cleaning processes. For this reason, acoustic forcing was further studied in this work using a larger pulverized swirl burner. Post-processed shadowgraph images from cold-flow experiments provided insights into the near-field particle distribution and quantified particle dispersion in a broad range of operating conditions. Particle dispersion increased near-linearly with the pressure amplitude of the acoustic forcing, which presented the strongest effect followed by the swirl intensity of the secondary air. Both techniques applied simultaneously had a synergetic effect, especially for small particle size (e.g. dispersion angle increased from 0.9 to 9.1° for particles in the size range of 63-112 μm).High particle dispersion significantly reduced the flame liftoff distance (ignition characteristic) during combustion, which was identified by the high-speed imaging technique. The reduction in liftoff distance, caused by the acoustic forcing in combustion conditions, varied from 6 to 28%. Higher reduction was identified for high oxygen level enrichment and small particles. Acoustic forcing applied at conditions with low secondary air momentum flux resulted in lower CO emissions and higher combustion efficiency, with higher NO emissions. Under gasification, the ignition occurred at earlier stages than in combustion as demonstrated by the changes in liftoff distance, which was strongly affected by the producer gas recirculation (containing CO and H2). The acoustic forcing presented a sharper effect on liftoff in such conditions, decreasing by 42% at low equivalence ratios (λ of 0.4). Moreover, acoustic forcing increased cold-gas efficiency by 12%, by increasing the yields of CO and H2.Particle emissions were characterized by particulate matter (PM) isokinetic sampling and coarse particle collection with further thermogravimetric, elemental, and particle size distribution analysis. The coarse particles presented a small reduction of carbon content for combustion conditions under acoustic forcing. In gasification conditions, acoustically forced cases presented up to 25% lower PM emissions, while coarse particle emissions increased substantially. Ultimate and thermogravimetric analysis suggests that soot was an important component of the PM emissions. Coarse particles during gasification mainly consisted of fragmented char, which yield increased with acoustic forcing, apparently due to high velocities imposed on the particles around the flow centerline, which gave them a shorter residence time at high temperatures.Experiments in a larger scale reactor, with 100 kW thermal capacity, were used for studies focused on the particle emissions and deposition from high-temperature oxygenenriched combustion of rice husks. A completely different ash morphology was identified in such experiments, which mainly presented coarse ash fraction deposit build-ups with high Si content and minor ash-forming elements. These characteristics can be beneficial both for bioenergy applications and ash valorization processes. The current work brings new experimental results of EFRs under different particle-laden flow characteristics. The implications in particle dispersion, flame morphology, and emissions could be addressed in further investigations, from fundamental aspects to optimization of burners of EFRs.
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| 26. |
- Dal Belo Takehara, Marcelo, 1987-, et al.
(författare)
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Pulverized biomass flame under imposed acoustic oscillations : Flame morphology and emission characteristics
- 2022
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Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- Forced intermittent combustion with periodical variations of pressure, velocity, and air-fuel ratios is a promising method to increase efficiency and reduce emissions from combustion and gasification applications. In this work, flame characteristics and emissions from a pulverized biomass burner are investigated under oscillations induced by an acoustically-driven synthetic jet. Instantaneous images of incandescent light emitted from flame were captured using high-speed cameras. The images were analyzed to identify the liftoff distance, flame length, and shape. The flame liftoff distance decreased under excited conditions, notably at high forcing amplitude applied to small particle size distribution (63-112 μm). In such conditions, acoustic forcing increases particle dispersion as presented in the previous work, providing conditions for earlier ignition due to enhanced fuel-air mixing besides reducing CO emissions. Flue gas emissions were influenced mainly by the particle size distribution, from which the 63-112 μm particle size presented the lowest values of CO and highest levels of NO emissions. The results presented stable flame edge positions for the particle size of 63-112 μm, while wide range particle distributions (0–600, 0-400 μm) had strong fluctuations, indicating high flame instability. The experimental work adds new insights regarding acoustic excitation in swirl burners, which could be used to optimize pulverized fuel combustion.
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| 27. |
- Engström, T. Fredrik, et al.
(författare)
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Gyroscopic design of swirling flow diffusers
- 1999
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Ingår i: Proceedings of ASME/JSME FEDSM'99. - : American Society of Mechanical Engineers.
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Konferensbidrag (refereegranskat)abstract
- The flow in the draft tube of a hydro power plant is often swirling when the turbine is operating outside its best efficiency point. The swirl gives rise to gyroscopic effects when the flow is forced through the bend in the draft tube. The resulting complex flow field causes losses.The idea in this paper is to investigate the possibility of using a simple model to calculate a new geometry of the draft tube that avoids distortion of the vortex core. Simulations are carried out using the CFD code CFX. A Reynolds stress model, with wall functions, is used to model turbulence.A loss factor is calculated and it was found that the new design draft tube shows approximately the same loss as a non-modified draft tube. The explanation to the somewhat surprising result is that the flow through and after the bend is dominated by the centrifugal effects from streamline curvature. It is therefore concluded that the most important loss mechanism appears to be triggered by streamline curvature.
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| 28. |
- Furusjö, Erik, et al.
(författare)
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Co-gasification of pyrolysis oil and black liquor - a new track for production of chemicals and transportation fuels from biomass
- 2015
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Konferensbidrag (refereegranskat)abstract
- Pressurized oxygen-blown entrained flow black liquor (BL) gasification, the Chemrec technology, has been demonstrated in a 3 MWth pilot plant in Piteå, Sweden for more than 25,000 h. The plant is owned and operated by Luleå University of Technology since 2013. It is well known that catalytic activity of alkali metals is important for the high reactivity of black liquor, which leads to a highly efficient BL gasification process. The globally available volume of BL is however limited and strongly connected to pulp production. By co-gasifying pyrolysis oil (PO) with BL it is possible to utilize the catalytic activity also for PO conversion to syngas. Adding PO leads to larger feedstock flexibility with the possibility of building larger biofuels plants based on BL gasification technology. This presentation summarizes new results from research activities aimed at developing and assessing the PO/BL co-gasification process. Results from laboratory experiments with PO/BL mixtures show that pyrolysis behavior and char gasification reactivity are similar to pure BL. This means that the decrease in the alkali metal concentration due to the addition of PO in the mixture does not decrease the reactivity. Pure PO is much less reactive. Mixing tests show that the fraction of PO that can be mixed into BL is limited by lignin precipitation as a consequence of PO acidity. Pilot scale PO/BL co-gasification experiments have been executed following design and construction of a new feeding system to allow co-feeding of PO with BL. The results confirm the conclusions from the lab scale study and prove that the co-gasification concept is practically applicable. Process performance of the pilot scale co-gasification process is similar to gasification of BL only with high carbon conversion and clean syngas generation. This indicates that the established BL gasification technology can be used for co-gasification of PO and BL without major modifications.
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| 29. |
- Gebart, Rikard
(författare)
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Analysis of heat transfer and fluid flow in the resin transfer moulding process
- 1992
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis contains an analysis of fluid flow and heat transfer problems in the resin transfer moulding (RTM) process for manufacturing of polymer based fibre composites and it consists of five separate papers. The permeability of unidirectional fabrics, that are often used in advanced composites, is considered in Paper A and a theory for the permeability dependence on the micro geometry is developed. The theory is based on lubrication theory for narrow gaps which is motivated by the fact that most of the flow resistance comes from a small region where the fibres are closest to each other. Despite this limitation the results agree excellently with numerical results. 'Me best performance of the theory is expected at high fibre volume fractions (Vf) but the dependence on Vf is surprisingly good even at as low values as 0.3. Although the theory is formulated for an idealised geometry it can be used to predict the variation of the anisotropic permeability tensor with fibre volume fraction in real fabrics after fitting of three model parameters. Paper B is a study of the influence from different process parameters on the void content in the laminate. The void content is shown to be reduced strongly by an applied vacuum during mould filling. The main mechanism for void formation appears to be mechanical entrapment at the flow front. The voids are convected by the flow so that their concentration is highest close to the flow front. Microscopy investigation of the bubbles show that they are of two basic types, large spherical bubbles in the interstices between fibre bundles and smaller cylindrical bubbles inside the fibre bundles. The positive influence of vacuum compared to no vacuum can be explained as a combined effect of an increased mobility due to larger volume changes during mould filling and compression by the increased pressure during cure. In Paper C a comparison is made between the mould filling times for different injection strategies. The possible alternatives for a normal laminate are point injection, edge injection and peripheral injection. Theoretical results are derived that can be used to estimate the mould filling time with the different alternatives. In addition, fundamental theoretical results are derived from the governing equations showing the scaling of the mould filling time with the process parameters. This analysis also shows that the flow front motion during mould filling is only a function of the anisotropy of the reinforcement and the location of the gates. Paper D presents an analysis of the non-uniform flow at the flow front during impregnation of a stack of fabrics consisting of layers with different flow resistance. A detailed derivation of the theory and an analytical solution to the equations are presented in an addendum to Paper D. The theoretical model is compared with experimental results and is found to describe the experiment qualitatively well. The resulting permeability of a stack of different fabrics is derived from the basic equations and is found to be a weighted average of the permeability in the individual layers. This result is compared with experiments with different stacking sequences and it is found that the stacking sequence has no influence on the resulting permeability as expected from the theory. Experimental results in excellent agreement with Darcy's law are also presented for the case with radial flow and with unidirectional flow. Finally, Paper E is a theoretical study of the curing behaviour of thick laminates. A general solution independent of the cure kinetic model is derived. The solution is valid for low exothermal peak temperatures and it is characterised by two dimensionless numbers. The first parameter is the ratio between the time scales for the reaction and for heat conduction, the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The general solution is specialised to a second order autocatalytic cure model so that the results can be compared to numerical results. The agreement between the numerical and the analytical solution is excellent for small exothermal peak temperatures, as expected. The particular model used also serves as an example of the additional dimensionless parameters that are introduced by a specific kinetic model.
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| 30. |
- Gebart, Rikard
(författare)
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Critical parameters for heat transfer and chemical reactions in thermosetting materials
- 1994
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 51:1, s. 153-168
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Tidskriftsartikel (refereegranskat)abstract
- The equations of one-dimensional heat transfer with chemical reactions with isothermal initial conditions and constant wall temperature are solved approximately for all types of kinetic models. The general solution is valid for low exothermal peaks and it is characterized explicitly by two dimensionless parameters. The first parameter is the ratio between the time scale for heat conduction and that for the chemical reaction; the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The number of additional parameters depends on the particular choice of kinetic model. The maximum temperature in the solution always occur at the center line and its magnitude is proportional to the maximum rate of reaction. For a second-order autocatalytic kinetic model, closed form results can be obtained. The solution is in this case characterized by two additional dimensionless parameters. The analytical solution agrees excellently with numerical solutions for small exothermal temperature peaks (< 10% of the adiabatic temperature rise), but the qualitative agreement is very good also for cases with significant exothermal peaks. The general solution can be used also for the case when the kinetic model is unknown and only experimental DSC results are available.
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| 31. |
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| 32. |
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| 33. |
- Gebart, Rikard, et al.
(författare)
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Measurement of in-plane permeability of anisotropic fiber reinforcements
- 1996
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Ingår i: Polymer Composites. - : Wiley. - 0272-8397 .- 1548-0569. ; 17:1, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- Three of the most common methods (two with parallel flow and one with radial flow) for determination of the in-plane permeability tensor are studied both theoretically and experimentally. An error analysis shows that the difference between the methods is negligible if the error levels are equal. However, the radial flow method is found to be susceptible to large errors from mold deflection in an experimental comparison between the methods. Additional experiments with the radial flow method in a stiffer mold show that the method gives the same values for the permeability tensor as the other two methods. A new method with multiple cavities in parallel is proposed that combines the simplicity of the radial flow method with the stiff mold of the parallel flow method. Only mass and time need to be measured in one experiment and it eliminates the need to measure fluid viscosity, temperature, and injection pressure. The method depends on the availability of a reference material with known permeability.
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| 34. |
- Gebart, Rikard
(författare)
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Permeability of unidirectional reinforcements for RTM
- 1992
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Ingår i: Journal of composite materials. - : SAGE Publications. - 0021-9983 .- 1530-793X. ; 26:6, s. 1100-1133
-
Tidskriftsartikel (refereegranskat)abstract
- The permeability of an idealized unidirectional reinforcement consisting of regularly ordered, parallel fibres is derived starting from first principles (Navier-Stokes equations) both for flow along and for flow perpendicular to the fibres. First, an approximate analytical solution for transverse flow is derived which differs from the Kozeny-Carman equation for the permeability of a porous medium in that the transverse flow stops when the maximum fibre volume fraction is reached. The solution for flow along the fibres has the same form as the Kozeny-Carman equation. A comparison shows excellent agreement between a numerical solution of the full flow equations and the approximate one at medium to high fibre volume fractions (Vf > 0.35). The theoretical predictions of permeability were tested in a specially designed mould. The results from the experiments with an unsaturated polyester resin (Jotun PO-2454) and the unidirectional reinforcement did in all cases show excellent agreement with results predicted by Darcy's law (the square of the flow front position increases linearly with time if the injection pressure is kept constant). The theoretical model could be fitted to the experimental data both for flow along the fibres and for cross flow based on data for flow along the fibres only. The fitting is obtained by adjusting one parameter in the model, the effective fibre radius, to a value about four times larger than the real fibre radius (15 μm). Scanning electron microscopy shows that the fibres are arranged in bundles looking like cylinders with ellipsoidal cross section which may be the explanation for the effective fibre radius in the fitted model equation being larger than the real fibre radius.
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| 35. |
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| 36. |
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| 37. |
- Gebart, Rikard, et al.
(författare)
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Squeeze flow rheology in large tools
- 1999
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Ingår i: Fifth International Conference on Flow Processes in Composite Materials. - : University of Plymouth Press. - 1870918010 ; , s. 365-372
-
Konferensbidrag (refereegranskat)
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| 38. |
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| 39. |
- Gebart, Rikard
(författare)
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Thermal runaway criterion for thick polymer composites
- 2024
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- An analytical solution has been developed for the curing of thick polymer composite laminates that shows how the temperature profile responds to arbitrary changes to the material properties and process parameters and that curing with slow reactions and a low exotherm temperature is impossible if the Damköhler number is above a well-defined limit. The thermal runaway criterion can be recast as a criterion for the maximum allowable thickness of the laminate. The thermal runaway criterion was found to agree well with some results for thick laminates from the literature, but the peak temperature in the laminate was underpredicted for stable conditions. The model has a constant that can be adjusted to improve the peak temperature prediction, but more validation data is needed before the model can be optimized to simultaneously predict the peak temperature and thermal runaway with high accuracy.
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| 40. |
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| 41. |
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| 42. |
- Grip, Carl-Erik, et al.
(författare)
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Industrial ecology in northern areas : practical experience and development
- 2010
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Konferensbidrag (refereegranskat)abstract
- The possibilities to develop the industrial ecology in the northern regions of Europe are influenced by some common characteristics, e.g.: The regions are rich in natural re-sources and energy- and material intensive base industries. These industries cover sev-eral branches, e.g., Mining, Iron and Steel, Metal production, Pulp and Paper. Low popu-lation density and relatively long distances to the main customers are difficulties espe-cially for transport and use of rest products. District heating with waste heat from the in-dustries is an important part of the energy system that reduces the emission of green-house gases and improves the overall energy efficiency. The problems and possibilities connected to the industrial ecology are described for two examples, the energy system in Luleå and the Solander science park in Piteå
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| 43. |
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| 44. |
- Guo, Ning, et al.
(författare)
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Computational fluid dynamic simulations of thermochemical conversion of pulverized biomass in a dilute flow using spheroidal approximation
- 2020
-
Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 271
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Tidskriftsartikel (refereegranskat)abstract
- A drag force model for spheroids, referred as the spheroid model, was implemented in OpenFOAM, in order to better predict the thermochemical conversion of pulverized biomass. Our previous work has found that the spheroid model predicts more dispersed results in terms of particle velocities and local concentrations comparing to other conventional particle models under non-reactive conditions. This work takes the spheroid model one step further, by validating against experiments performed under reactive conditions with a newly implemented heat transfer model for spheroids as well as updated devolatilization kinetic parameters. In addition, simulations were conducted in a configuration similar to a pilot-scale entrained flow gasifier for more realistic scenarios. Particle mass and axial velocity development were compared accordingly using four different modelling approaches with increasing complexity. When compared with models of spheroidal shape assumptions, the sphere and simplified non-sphere model predict 61% and 43% longer residence times, respectively. The combination of the spheroid shape assumption with the heat transfer model for spheroids tends to promote drying and devolatilization. On the other hand, the traditional spherical approach leads to longer particle residence times. These opposing effects are believed to be a major contributing factor to the fact that no significant differences among modelling approaches were found in terms of syngas production at the outlet. Furthermore, particle orientation information was reported in both experiments and simulations under reactive conditions. Its dependency on gas velocity gradient under reactive conditions is similar to what was reported under non-reactive conditions.
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| 45. |
- Göktepe, Burak, et al.
(författare)
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Cold flow experiments in an entrained flow gasification reactor with a swirl-stabilized pulverized biofuel burner
- 2016
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Ingår i: International Journal of Multiphase Flow. - : Elsevier BV. - 0301-9322 .- 1879-3533. ; 85, s. 267-277
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Tidskriftsartikel (refereegranskat)abstract
- Short particle residence time in entrained flow gasifiers demands the use of pulverized fuel particles to promote mass and heat transfer, resulting high fuel conversion rate. The pulverized biomass particles have a wide range of aspect ratios which can exhibit different dispersion behavior than that of spherical particles in hot product gas flows. This results in spatial and temporal variations in temperature distribution, the composition and the concentration of syngas and soot yield. One way to control the particle dispersion is to impart a swirling motion to the carrier gas phase. This paper investigates the dispersion behavior of biomass fuel particles in swirling flows. A two-phase particle image velocimetry technique was applied to simultaneously measure particle and gas phase velocities in turbulent isothermal flows. Post-processed PIV images showed that a poly-dispersed behavior of biomass particles with a range of particle size of 112–160 µm imposed a significant impact on the air flow pattern, causing air flow decelerated in a region of high particle concentration. Moreover, the velocity field, obtained from individually tracked biomass particles showed that the swirling motion of the carrier air flow gives arise a rapid spreading of the particles.
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| 46. |
- Göktepe, Burak, et al.
(författare)
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Does distance among biomass particles affect soot formation in an entrained flow gasification process?
- 2016
-
Ingår i: Fuel processing technology. - : Elsevier. - 0378-3820 .- 1873-7188. ; 141, s. 99-105
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Tidskriftsartikel (refereegranskat)abstract
- Soot creates technical challenges in entrained flow biomass gasification processes, e.g. clogging of flow passages, fouling on system components and reduced efficiency of gasification. This paper demonstrates a novel soot reduction method in a laboratory-scale entrained flow reactor by forced dispersion of biomass particles. Gasification of small biomass particles was done in a flat flame burner where a steady stream of biomass was sent. The flat flame burner was operated with a premixed sub-stoichiometric methane-air flame to simulate the conditions in an entrained flow gasifier. The dispersion of biomass particles was enhanced by varying the flow velocity ratio between particle carrier gas and the premixed flame. Primary soot particles evolved with the distance from the burner exit and the soot volume fraction was found to have a peak at a certain location. Enhanced particle separation diminished the peaks in the soot volume fraction by 35-56% depending on the particle feeding rates. The soot volume fraction was found to decrease towards an asymptotic value with increasing inter-particle distance.
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| 47. |
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| 48. |
- Göktepe, Burak, et al.
(författare)
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Soot reduction in an entrained flow gasifier of biomass by active dispersion of fuel particles
- 2017
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; , s. 111-117
-
Tidskriftsartikel (refereegranskat)abstract
- Soot is an undesired by-product of entrained flow biomass gasification since it has a detrimental effect on operation of the gasifier, e.g. clogging of flow passages and system components and reduction of efficiency. This study investigated how active flow manipulation by adding synthetic jet (i.e. oscillating flow through orifice) in feeding line affects dispersion of fuel particles and soot formation. Pine sawdust was gasified at the conditions similar to pulverized burner flame, where a flat flame of methane-air sub-stoichiometric mixture supported ignition of fuel particles. A synthetic jet flow was supplied by an actuator assembly and was directed perpendicular to a vertical tube leading to the center of the flat flame burner through which pine sawdust with a size range of 63-112. μm were fed into a reactor. Quartz filter sampling and the laser extinction methods were employed to measure total soot yield and soot volume fraction, respectively. The synthetic jet actuator modulated the dispersion of the pine sawdust and broke up particle aggregates in both hot and cold gas flows through generation of large scale vortex structures in the flow. The soot yield significantly reduced from 1.52. wt.% to 0.3. wt.% when synthetic jet actuator was applied. The results indicated that the current method suppressed inception of young soot particles. The method has high potential because soot can be reduced without changing major operation parameters. © 2016.
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| 49. |
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| 50. |
- Hadi Jafari, Pantea, et al.
(författare)
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Effect of process parameters on the performance of an air-blown entrained flow cyclone gasifier
- 2020
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Ingår i: International Journal of Sustainable Energy. - : Taylor & Francis. - 1478-6451 .- 1478-646X. ; 39:1, s. 21-40
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Tidskriftsartikel (refereegranskat)abstract
- Entrained flow gasification of biomass in a cyclone reactor combined by a gas engine has been applied in Nordic countries as one of the preferred methods for generating combined heat and power in small scales. The purpose of the current study was to optimise the gasification plant efficiency and understanding the influence of operating conditions. The experiments were carried out in a 2.4 MW(th) commercial gasification power plant. The gasifier was operated in optimum at a rather low lambda around 0.27 and a temperature of 950°C. The lower heating value of the clean product gas at this lambda was 5.95 MJ/Nm3. The experimental results also were compared with the predicted values from thermodynamic equilibrium calculations by Factsage 7.0. The performance of five different types of biofuels including torrefied spruce, peat, rice husk, bark and stemwood were assessed and compared with each other using thermodynamic equilibrium and available experimental data.
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