Thermoacoustic analysis of the dynamic pressure inside a model combustor during limit cycle oscillations

In this work comprehensive experimental and numerical studies incorporating the most relevant physical mechanisms causing limit cycle pressure and combustion rate oscillations (LCO) in a laboratory scale combustor will be discussed. The strong interaction between the aerodynamics-combustion-acoustic oscillations (ACA), and under specific conditions the aerodynamics-combustion-structural vibrations (ACS), is studied by a careful selection of experiments and numerical simulations performed using commercially available computational models. It is shown predominantly that the convective time scales due to the aerodynamics at the flame stabilizer and the time period related to acoustic propagation have to be of the same order in magnitude to be able to drive the system into LCO. The measurements indicated that the frequency spectrum of the oscillations of the LCO has a distinct peak close to the natural mode of the combustor along with higher order “harmonics” due to non-linear effects. Some non-harmonic higher order peaks are observed that are associated with the structural (liner) natural frequencies of vibration. A numerical simulation has been performed using the commercial code (ANSYS V13.0) that includes the effects of fluid-structure interaction by means of pressure load transfer on to the structure and vice-versa. The fluid domain is modeled using CFX and the structural domain is represented by ANSYS. The information is exchanged between the two domains dynamically at every time step computed. In order to reduce the computational effort and quickly gain insight into the problem only a 2 mm slice of the whole geometry has been considered making it essentially a 2D analysis. The good agreement between the model and measured instability frequencies shows a very promising approach in predicting the limit cycle oscillations in this kind of configurations

Sensitivity of the Numerical Prediction of Turbulent Combustion Dynamics in the LIMOUSINE Combustor

The objective of this study is to investigate the sensitivity and accuracy of the reaction flow-field prediction for the LIMOUSINE combustor with regard to choices in computational mesh and turbulent combustion model. The LIMOUSINE combustor is a partially premixed, bluff body-stabilized natural gas combustor designed to operate at 40–80 kW and atmospheric pressure and used to study combustion instabilities. The transient simulation of a turbulent combusting flow with the purpose to study thermoacoustic instabilities is a very time-consuming process. For that reason, the meshing approach leading to accurate numerical prediction, known sensitivity, and minimized amount of mesh elements is important. Since the numerical dissipation (and dispersion) is highly dependent on, and affected by, the geometrical mesh quality, it is of high importance to control the mesh distribution and element size across the computational domain. Typically, the structural mesh topology allows using much fewer grid elements compared to the unstructured grid; however, an unstructured mesh is favorable for flows in complex geometries. To explore computational stability and accuracy, the numerical dissipation of the cold flow with mixing of fuel and air is studied first in the absence of the combustion process. Thereafter, the studies are extended to combustible flows using standard available ansys-cfx combustion models. To validate the predicted variable fields of the combustor's transient reactive flows, the numerical results for dynamic pressure and temperature variations, resolved under structured and unstructured mesh conditions, are compared with experimental data. The obtained results show minor dependence on the used mesh in the velocity and pressure profiles of the investigated grids under nonreacting conditions. More significant differences are observed in the mixing behavior of air and fuel flows. Here, the numerical dissipation of the (unstructured) tetrahedral mesh topology is higher than in the case of the (structured) hexahedral mesh. For that reason, the combusting flow, resolved with the use of the hexahedral mesh, presents better agreement with experimental data and demands less computational effort. Finally, in the paper, the performance of the combustion model for reacting flow is presented and the main issues of the applied combustion modeling are reviewe

Thermoacoustic analysis of the dynamic pressure inside a model combustor during limit cycle oscillations

In this work comprehensive experimental and numerical studies incorporating the most relevant physical mechanisms causing limit cycle pressure and combustion rate oscillations (LCO) in a laboratory scale combustor will be discussed. The strong interaction between the aerodynamics-combustion-acoustic oscillations (ACA), and under specific conditions the aerodynamics-combustion-structural vibrations (ACS), is studied by a careful selection of experiments and numerical simulations performed using commercially available computational models. It is shown predominantly that the convective time scales due to the aerodynamics at the flame stabilizer and the time period related to acoustic propagation have to be of the same order in magnitude to be able to drive the system into LCO. The measurements indicated that the frequency spectrum of the oscillations of the LCO has a distinct peak close to the natural mode of the combustor along with higher order “harmonics” due to non-linear effects. Some non-harmonic higher order peaks are observed that are associated with the structural (liner) natural frequencies of vibration. A numerical simulation has been performed using the commercial code (ANSYS V13.0) that includes the effects of fluid-structure interaction by means of pressure load transfer on to the structure and vice-versa. The fluid domain is modeled using CFX and the structural domain is represented by ANSYS. The information is exchanged between the two domains dynamically at every time step computed. In order to reduce the computational effort and quickly gain insight into the problem only a 2 mm slice of the whole geometry has been considered making it essentially a 2D analysis. The good agreement between the model and measured instability frequencies shows a very promising approach in predicting the limit cycle oscillations in this kind of configurations

Conversion of glucose to lactic acid derivatives with mesoporous Sn-MCM-41 and microporous titanosilicates

BACKGROUND: The production of value-added products from biomass has acquired increasing importance due to the high worldwide demand for chemicals and energy, uncertain petroleum availability and the necessity of finding environmentally friendly processes. This paper reports work on the synthesis of several catalysts for the conversion of glucose to methyl lactate. RESULTS: A MCM-41 type mesoporous material containing tin (Si/Sn = 55) was developed with a uniform ordered mesoporous structure, high specific surface area and high pore volume. Sn-MCM-41 was tested in three consecutive catalytic cycles to evaluate its reusability giving methyl lactate yields of 43%, 41% and 39%, in each cycle. The slightly reduction in activity could be explained by the reduction in the accessibility of active centers due to the adsorption of reaction products and structural changes. Microporous titanosilicates and MFI-type zeolite ZSM-5 showed a lower catalytic performance, but exfoliated materials gave higher yields of methyl lactate and pyruvaldehyde dimethyl acetal than their respective layered precursors. CONCLUSIONS: Sn-MCM-41 material showed good results in the conversion of glucose to methyl lactate over three catalytic cycles and exfoliated materials facilitated the access of glucose to the catalytic sites and fast desorption of products.The authors gratefully thank the Spanish Ministry of Economy and Competitiveness (MINECO) for financial support through project MAT2010-15870, as well as the Regional Government of Aragón (DGA), the Obra Social La Caixa (GA-LC-019/2011) and the European Social Fund (ESF). C. Casado also thanks MINECO for the ‘Ramón y Cajal’ program (RYC-2011-08550)

Generating new fanca-deficient hnscc cell lines by genomic editing recapitulates the cellular phenotypes of fanconi anemia

Fanconi anemia (FA) patients have an exacerbated risk of head and neck squamous cell carcinoma (HNSCC). Treatment is challenging as FA patients display enhanced toxicity to standard treatments, including radio/chemotherapy. Therefore, better therapies as well as new disease models are urgently needed. We have used CRISPR/Cas9 editing tools in order to interrupt the human FANCA gene by the generation of insertions/deletions (indels) in exon 4 in two cancer cell lines from sporadic HNSCC having no mutation in FA-genes: CAL27 and CAL33 cells. Our approach allowed efficient editing, subsequent purification of single-cell clones, and Sanger sequencing validation at the edited locus. Clones having frameshift indels in homozygosis did not express FANCA protein and were selected for further analysis. When compared with parental CAL27 and CAL33, FANCA-mutant cell clones displayed a FA-phenotype as they (i) are highly sensitive to DNA interstrand crosslink (ICL) agents such as mitomycin C (MMC) or cisplatin(ii) do not monoubiquitinate FANCD2 upon MMC treatment and therefore (iii) do not form FANCD2 nuclear foci, and (iv) they display increased chromosome fragility and G2 arrest after diepoxybutane (DEB) treatment. These FANCA-mutant clones display similar growth rates as their parental cells. Interestingly, mutant cells acquire phenotypes associated with more aggressive disease, such as increased migration in wound healing assays. Therefore, CAL27 and CAL33 cells with FANCA mutations are phenocopies of FA-HNSCC cells

El Pla d'estavi energètic de la UPC (2011-2014)

Projecte presentat al 5è Premi a la Qualitat de la Gestió Universitària, convocat pel Consell Social de la UPCAward-winningPostprint (author's final draft

Comprehensive analysis and insights gained from long-term experience of the Spanish DILI Registry

Background & aims: Prospective drug-induced liver injury (DILI) registries are important sources of information on idiosyncratic DILI. We aimed to present a comprehensive analysis of 843 patients with DILI enrolled into the Spanish DILI Registry over a 20-year time period. Methods: Cases were identified, diagnosed and followed prospectively. Clinical features, drug information and outcome data were collected. Results: A total of 843 patients, with a mean age of 54 years (48% females), were enrolled up to 2018. Hepatocellular injury was associated with younger age (adjusted odds ratio [aOR] per year 0.983; 95% CI 0.974-0.991) and lower platelet count (aOR per unit 0.996; 95% CI 0.994-0.998). Anti-infectives were the most common causative drug class (40%). Liver-related mortality was more frequent in patients with hepatocellular damage aged ≥65 years (p = 0.0083) and in patients with underlying liver disease (p = 0.0221). Independent predictors of liver-related death/transplantation included nR-based hepatocellular injury, female sex, higher onset aspartate aminotransferase (AST) and bilirubin values. nR-based hepatocellular injury was not associated with 6-month overall mortality, for which comorbidity burden played a more important role. The prognostic capacity of Hy's law varied between causative agents. Empirical therapy (corticosteroids, ursodeoxycholic acid and MARS) was prescribed to 20% of patients. Drug-induced autoimmune hepatitis patients (26 cases) were mainly females (62%) with hepatocellular damage (92%), who more frequently received immunosuppressive therapy (58%).The present study has been supported by grants of Instituto de Salud Carlos III cofounded by Fondo Europeo de Desarrollo Regional – FEDER (contract numbers: PI19/00883, PI16/01748, PI18/00901, PI18/01804, PI-0285-2016, PI-0274-2016, PI-0310- 2018, PT17/0017/0020) and Agencia Española del Medicamento. CIBERehd and Plataforma ISCIII Ensayos Clinicos are funded by Instituto de Salud Carlos III. MRD holds a Joan Rodes (JR16/ 00015)/Acción B clinicos investigadores (B-0002-2019) and JSC a Rio Hortega (CM17/00243) research contract from ISCIII and Consejería de Salud de Andalucía. The funding sources had no involvement in the study design; in the collection, analysis, and interpretation of data; in the writing of the report or in the de- cision to submit the manuscript for publication