| 1. |
- Ericsson, Per, et al.
(författare)
-
Characterization of particulate emissions and methodology for oxidation of particulates from non-diesel combustion systems
- 2008
-
Ingår i: SAE Technical Paper. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
-
Tidskriftsartikel (refereegranskat)abstract
- Tailpipe particulate emissions, i.e., particle number, size distribution and total mass, from a series of four-cylinder engines with 2L displacement and power output of approximately 150 hp have been measured. The engines were in their respective vehicle installation, all midsize vehicles from various manufacturers, and represented different combustion concepts, i.e., port- and direct-injected vehicles and E5 and E85 fuels. The results are compared to post-Euro V emission standards for gasoline and biofuels using diesel as reference. The results show that the type of combustion and fuel significantly affect the particulate formation. In general, direct-injected engines show high particle numbers and mass compared to port-injected engines. The particulate number and total mass can be reduced by using biofuels, e.g., ethanol mixes, instead of gasoline. Moreover, an experimental procedure and setup facilitating precise studies of oxidation of particulates in realistic filter structures by well-controlled gas flow (composition and temperature) and sample (particulate load and temperature) conditions has been developed. The results from this method have been verified by using commercial soot as reference.
|
|
| 2. |
- Mahmoudkhani, Maryam, 1971, et al.
(författare)
-
Low energy sodium hydroxide recovery for CO2 capture from atmospheric air – Thermodynamic analysis
- 2009
-
Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 3:4, s. 376-384
-
Tidskriftsartikel (refereegranskat)abstract
- To reduce the risks of climate change, atmospheric concentrations of greenhouse gases must be lowered.Direct capture of CO2 from ambient air, ‘‘air capture’’, might be one of the few methods capable of systematically managing dispersed emissions. The most commonly proposedmethod for air capture is a wet scrubbing technique which absorbs CO2 in an alkaline absorbent, i.e. sodium hydroxide producing an aqueous solution of sodium hydroxide and sodium carbonate. In most of the previous works it was assumed that the absorbent would be regenerated and CO2 liberated from the alkaline carbonatesolution using a lime and calcium carbonate causticization cycle. We describe a novel technique for recovering sodium hydroxide from an aqueous alkaline solution of sodium carbonate and present an end-to-end energy and exergy analysis. In the first step of the recovery process, anhydrous sodium carbonate is separated from the concentrated sodium hydroxide solution using a two-step precipitation and crystallization process. The anhydrous sodium carbonate is then causticized using sodium tri-titanate. The titanate direct causticization process has been of interest for the pulp and paper industry and has been tested at lab- and pilot-scale. In the causticization process, sodium hydroxide is regenerated and carbon dioxide is liberated as a pure stream, which is compressedfor use or disposal. The technique requires 50% less high-grade heat than conventional causticization and the maximum temperature required is reduced by at least 50 8C. This titanate cycle may allow a substantial reduction in the overall cost of direct air capture.
|
|
| 3. |
- Perdana, Indra, 1973, et al.
(författare)
-
Effect of external mass transport on permeation in a Wicke-Kallenbach cell
- 2009
-
Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 87:10, s. 1438-1447
-
Tidskriftsartikel (refereegranskat)abstract
- Wicke-Kallenbach (WK) cells are often used for studying separation and component transport in porous material. In order to obtain important transport parameters, mathematical models are frequently developed but they generally consider the fluid phase in the WK compartments to be free of concentration gradients and thus external mass transport resistance is neglected. The present work is a detailed study of how the external transport influences permeation through porous material in a WK cell. External mass transfer effects were demonstrated experimentally and they were further studied from three-dimensional (3-D) model simulations. Film theory was applied to develop an appropriate Sherwood number correlation for the external mass transport coefficient. It was shown that the flow in the compartment and geometrical factors of the WK cell had significant influences on the permeation. It was found that introducing the proposed external mass transport correlation into a simplified one-dimensional (1-D) model was adequate to reproduce results from both the experimental data and the 3-D model.
|
|
| 4. |
- Schwartz, W. R., et al.
(författare)
-
Combustion of methane over palladium based catalysts - A study of catalytic deactivation & the use of electrochemical oxygen pumping
- 2007
-
Ingår i: 5th US Combustion Meeting 2007. - : Combustion Institute. - 9781604238112 ; , s. 1787-1794
-
Konferensbidrag (refereegranskat)abstract
- Methane oxidation over palladium is of interest due to its clean catalytic combustion properties, forming only carbon dioxide and water. A successful palladium based catalyst will virtually eliminate polluting by products including unburned hydrocarbons, carbon monoxide, soot, and NOx. These potential benefits have have not been realized, in part due to catalyst deactivation over time. In this study we identify a relationship between catalyst deactivation and hydroxyl formation on Pd/Al2O3 and Pd/TiO2 catalyst surfaces, using time series FTIR spectroscopy. FTIR analysis suggests that catalyst deactivation is caused by growth of surface hydroxyls at temperatures below 450°C, and that that oxygen mobility on the catalyst surface may correlate with the degree of catalytic deactivation. We also examine the use of electrochemical oxygen pumping through a yttrium stabilized zirconia (YSZ) membrane as a possible method of delivering oxygen to the methane catalytic combustion reaction and improving catalytic conversion. We observe that applying a potential across a YSZ membrane can result in moderate increases in methane conversion, and that oxygen concentration in reactant gas mixture has a dramatic effect on catalytic activity. Our study will also address electrochemical oxygen transport to determine its rate limiting impact on the methane catalytic combustion reaction.
|
|
| 5. |
- Sjöblom, Jonas, 1968, et al.
(författare)
-
Latent variable projections of sensitivity data for experimental screening and kinetic modeling
- 2008
-
Ingår i: Computers and Chemical Engineering. - : Elsevier BV. - 0098-1354. ; 32:12, s. 3121-3129
-
Tidskriftsartikel (refereegranskat)abstract
- In microkinetic modeling the number of kinetic parameters is large and the precision of the “known” parameters is often very low. The standard approach is then to fit only the most uncertain parameters while regarding the fixed parameter as “true”. This assumption will have consequences also on the fitted parameters since the correlation structure often is quite significant. In this study we have taken the approach to fit many parameters and then try to use more efficient experimental designs to break the correlation structure and thus obtain more precise parameter estimation despite the large number of fitted parameters. After performing sensitivity analysis of many candidate experiments, a latent variable model (PCA) is made from the resulting sensitivity matrix and the score matrix is used as a candidate set prior to experiment selection. Due to the correlation structure in the sensitivity matrix, the number of components from the PCA model is fewer than the number of parameters. The columns in the score matrix are furthermore orthogonal whereas the columns in the original sensitivity matrix are not. Different designs were generated using the original sensitivity matrix, the score matrix as well as using a space-filling design and performing a sequential approach. Both steady state and transient experiments were evaluated. These different designs were used to fit kinetic parameters to a simulated dataset made using published parameter values. The results show no significant difference when using the original sensitivity matrix or the score matrix. However, since the score matrix has fewer columns than the full sensitivity matrix, the use of designs based on the score matrix enables more efficient designs when few experiments are required. The number of components in the PCA model also gives the rank of the parameter space induced by the candidate experiments. This is useful information when fitting many parameters in a microkinetic model and provides an assessment of the value of every candidate experiment before it is even performed.
|
|
| 6. |
- Ström, Henrik, 1981, et al.
(författare)
-
Choice of urea-spray models in CFD simulations of urea-SCR systems
- 2009
-
Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 150:1, s. 69-82
-
Tidskriftsartikel (refereegranskat)abstract
- The sensitivity of modeling choices to obtained results for Eulerian–Lagrangian CFD simulations of urea-SCR systems has been investigated for a system consisting of an AdBlue-spray located at the exhaust pipe wall, directed into the exhaust gas flow. The decomposition of urea is modeled as being heat transfer limited and taking place at a constant temperature (425 K). It is shown that modeling choices may affect the predicted extent of wall hit, which types of droplets that are predicted to hit the wall, and also where they will do so.The influence of the different forces due to drag, buoyancy, lift effects, thermophoresis and history effects was investigated, proving that only the forces due to drag and buoyancy are necessary to correctly describe droplet motion within this system. It is necessary to use a droplet drag coefficient that takes the current level of droplet distortion into account.A stochastic particle tracking model will describe the effects of turbulent dispersion, but also make the simulation results sensitive to the quality of the turbulence model's prediction of the turbulent fluctuating velocities. Using such a model will also resolve some of the enhancement of heat and mass transfer caused by the continuous acceleration/deceleration of droplets by turbulent eddies.
|
|
| 7. |
- Ström, Henrik, 1981, et al.
(författare)
-
Simulations of Trapping of Diesel and Gasoline Particulate Matter in Flow-through Devices
- 2009
-
Ingår i: Topics in Catalysis. - 1572-9028 .- 1022-5528. ; 52:13, s. 2047-2051
-
Tidskriftsartikel (refereegranskat)abstract
- Eulerian–Lagrangian CFD modeling has been used to track eight types of typical diesel and gasoline soot particles through a flow-through substrate with protrusions. It is shown that there exists a minimum trapping efficiency for medium-sized soot particles (dp ≈ 150 nm). Small and large particles are trapped by different mechanisms, and thus appear in different patterns on the substrate walls.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
