Numerical study of the characteristics of CNG, LPG and Hydrogen turbulent premixed flames

Numerical simulations have proven itself as a significant and powerful tool for accurate prediction of turbulent premixed flames in practical engineering devices. The work presented in this thesis concerns the development of simulation techniques for premixed turbulent combustion of three different fuels, namely, CNG, LPG and Hydrogen air mixtures. The numerical results are validated against published experimental data from the newly built Sydney combustion chamber. In this work a newly developed Large Eddy Simulation (LES) CFD model is applied to the new Sydney combustion chamber of size 50 x 50 x 250 mm (0.625 litre volume). Turbulence is generated in the chamber by introducing series of baffle plates and a solid square obstacle at various axial locations. These baffles can be added or removed from the chamber to adapt various experimental configurations for studies. This is essential to understand the flame behaviour and the structure. The LES numerical simulations are conducted using the Smagorinsky eddy viscosity model with standard dynamic procedures for sub-grid scale turbulence. Combustion is modelled by using a newly developed dynamic flame surface density (DFSD) model based on the flamelet assumption. Various numerical tests are carried out to establish the confidence in the LES based combustion modelling technique. A detailed analysis has been carried out to determine the regimes of combustion at different stages of flame propagation inside the chamber. The predictions using the DFSD combustion model are evaluated and validated against experimental measurements for various flow configurations. In addition, the in-house code capability is extended by implementing the Lewis number effects. The LES predictions are identified to be in a very good agreement with the experimental measurements for cases with high turbulence levels. However, some disagreement were observed with the quasi-laminar case. In addition a data analysis for experimental data, regarding the overpressure, flame position and the flame speed is carried out for the high and low turbulence cases. Moreover, an image processing procedure is used to extract the flame rate of stretch from both the experimental and numerical flame images that are used as a further method to validate the numerical results. For the grids under investigation, it is concluded that the employed grid is independent of the filter width and grid resolution. The applicability of the DFSD model using grid-independent results for turbulent premixed propagating flames was examined by validating the generated pressure and other flame characteristics, such as flame position and speed against experimental data. This study concludes that the predictions using DFSD model provide reasonably good results. It is found that LES predictions were slightly improved in predicting overpressure, flame position and speed by incorporating the Lewis number effect in the model. Also, the investigation demonstrates the effects of placing multiple obstacles at various locations in the path of the turbulent propagating premixed flames. It is concluded that the pressure generated in any individual configuration is directly proportional to the number of baffles plates. The flame position and speed are clearly dependent on the number of obstacles used and their blockage ratio. The flame stretch extracted from both the experimental and numerical images shows that hydrogen has the highest stretch values over CNG and LPG. Finally, the regime of combustion identified for the three fuels in the present combustion chamber is found to lie within the thin reaction zone. This finding supports the use of the laminar flamelet modelling concept that has been in use for the modelling of turbulent premixed flames in practical applications

Treatment of Peyronie's Disease With Collagenase Clostridium histolyticum and Vacuum Therapy: A Randomized, Open-Label Pilot Study

BACKGROUND: Collagenase Clostridium histolyticum (CCH) is indicated for the treatment of penile curvature in adult men with Peyronie's disease (PD) with palpable plaque and curvature deformity of at least 30° at the start of therapy. AIM: To evaluate the efficacy and safety of CCH plus vacuum-pump therapy with and without penile modeling for the management of PD. METHODS: Adult men with PD and penile curvature of at least 30° were randomly assigned to receive CCH 0.58 mg plus vacuum therapy alone (n = 15) or with penile plaque modeling (n = 15). Patients received no more than four treatment cycles (cycle = ∼6-week duration), each consisting of two intralesional injections of CCH administered 24 to 72 hours apart. Vacuum therapy was applied twice daily from 14 days after the second injection of each cycle until the following cycle. Modeling was performed 24 to 72 hours after the second injection of each cycle. OUTCOMES: The primary end point was change in penile curvature from baseline to week 36; additional end points included changes in Peyronie's Disease Questionnaire (PDQ) domain scores, composite response (≥20% decrease in penile curvature and decrease in PDQ bother score ≥ 1 point), and global response (small but important, moderate, or much improvement in the Global Assessment of PD). RESULTS: At week 36, improvement in penile curvature from baseline was similar in the two groups (mean change from baseline = -23.7° [SD = 10.9] for CCH + vacuum + modeling and -23.3° [SD = 7.2] for CCH + vacuum; between-group difference = -0.3°, 95% CI = -7.3 to 6.6). Improvements in most PDQ domains, including bother, were observed from baseline to week 36 in the two groups. Most patients were composite (66.7% and 84.6% with CCH + vacuum + modeling and CCH + vacuum, respectively) and global (86.7% and 92.3%, respectively) responders. The most common adverse events were penile contusion, penile swelling, and penile pain. CLINICAL IMPLICATIONS: Vacuum-pump therapy administered alone or in combination with modeling after CCH treatment could improve PD symptoms. STRENGTHS AND LIMITATIONS: This was a pilot study with a small sample and limited follow-up duration. CONCLUSION: CCH and vacuum-pump therapy (alone or combined with modeling) could be an appropriate consideration for men with PD and warrants further investigation

NTI-ULCEROGENIC EFFECT OF GENISTEIN AGAINST INDOMETHACIN-INDUCED GASTRIC ULCER IN RATS

ABSTRACTObjectives: Free radicals generation, inflammation, and nitric oxide (NO) modulation are involved in indomethacin (IND)-induced gastric ulcers.Most of the drugs used for the treatment of gastric ulcer have various side effects. Genistein (GEN), the natural isoflavones isolated from soya beanhas an antioxidant, anti-inflammatory, and NO modulating activity. These properties could make GEN a promising and safe, natural candidate againstIND-induced peptic ulcers.Methods: Rats were divided into four groups. Control group; GEN group (10 mg/kg, p.o.); IND group (48 mg/kg, orally); and GEN+IND group (GENadministered 1 week before IND injection). 6 hrs after IND administration, all rats were sacrificed. Gastric juice acidity and gastric injury wereevaluated directly. The levels of tumor necrosis factor alpha (TNF-α), myeloperoxidase (MPO), and NO were determined in gastric tissues. Moreover,glutathione (GSH), malondialdehyde (MDA), and superoxide dismutase (SOD) activity were determined in mucosal tissues.Results: Several mechanisms are involved in IND-induced ulcers as evidenced from the increase in TNF-α, MPO, and reduction in NO levels. In addition,free radicals also participate in the pathogenesis as evidenced from the increase in MDA levels and reduction in GSH levels and SOD activity. On theother hand, pre-administration of GEN markedly attenuated IND-induced ulcers without affecting gastric acidity, through a reduction of the elevatedTNF-α and MPO levels. Moreover, GEN significantly restored the declined NO level and ameliorated the unbalanced oxidative stress parameters.Conclusion: GEN markedly protects against IND-induced ulcers as revealed from biochemical data and amelioration of IND-induced lesions.Therefore, GEN may be a promising candidate for protection against IND-induced gastropathy.Keywords: Genistein, Ulcers, Indomethacin, Nitric oxide, Myeloperoxidase, Tumor necrosis factor alpha

Hidroksiureja i srčane posljedice u djece s bolešću srpastih stanica

Cardiac complications in sickle cell disease patients are widely expected. They may be related to iron deposition, anaemia or vasculitis. Hydroxyurea is a known drug that decreases haemoglobin (Hb) S levels. The objective of the study was to assess the effect of hydroxyurea on cardiac sequelae in children with sickle cell disease. Sixty-five sickle cell disease children were enrolled in the study; 37 of them were on regular follow up and hydroxurea treatment, whereas 28 were not. All patients underwent echocardiography and N-terminal pro-brain natriuretic peptide (NT-proBNP) assay. Plasma levels of NTproBNP were significantly lower in sickle cell patients who were on hydroxyurea treatment than in those without this therapy (p=0.03). NTproBNP levels showed significant correlations with Hb (r=-0.72, p<0.05) and HbS levels (r=0.54, p<0.05). Significant positive correlations were detected between NTproBNP and echocardiography findings (r=0.64, p<0.01) including left ventricular mass index (r=0.78, p<0.01). In conclusion, hydroxyurea may reduce cardiac complications in children with sickle cell disease.Srčane komplikacije su vrlo vjerojatne u bolesnika s bolešću srpastih stanica, a mogu biti povezane s odlaganjem željeza, anemijom ili vaskulitisom. Hidroksiureja je lijek koji snižava razine hemoglobina (Hb) S. Cilj istraživanja bio je procijeniti učinak hidroksiureje na srčane posljedice u djece s bolešću srpastih stanica. U studiju je bilo uključeno 65 djece s bolešću srpastih stanica, od kojih je 37 bilo na terapiji hidroksiurejom uz redovito praćenje, a preostalih 28 nije primalo ovu terapiju. U svih bolesnika učinjena je ehokardiografija i test NT-proBNP. Razine NT-proBNP u plazmi bile su značajno niže u bolesnika s bolešću srpastih stanica koji su primali terapiju hidroksiurejom nego u onih bez ove terapije (p=0,03). Razine NT-proBNP pokazale su značajnu korelaciju s razinama Hb (r=-0,72, p<0,05) i HbS (r=0,54, p<0,05). Značajna pozitivna korelacija utvrđena je između NT-proBNP i ehokardiografskih nalaza (r=0,64, p<0,01) uključujući indeks mase lijeve klijetke (r=0,78, p<0,01). Zaključno, hidroksiureja može smanjiti srčane komplikacije kod djece s bolešću srpastih stanica

Lean partially premixed turbulent flame equivalence ratio measurements using laser-induced breakdown spectroscopy

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.The creation of a more stable flame along with the extension of flammability limits under lean mixture combustion was the main motivation to develop a new burner design, which has been investigated in this research. The current burner configuration was utilized to create a wide range of higher turbulent intensities and to produce different degrees of mixture inhomogeneity, which acted to promote minimum pollution, highest performance and higher flame stability. The burner stability assessment was investigated using two types of fuel: natural gas (NG) and liquefied petroleum gas (LPG). They were tested under different degrees of partial premixing, and two turbulence generator disks for lean mixture at an equivalence ratio of φ = 0.8 were used. Following this, the Laser Induced Breakdown Spectroscopy (LIBS) technique was utilized to characterize and quantify the impact of changing the disk slit diameter on the distributions profiles of equivalence ratio or mixture fraction for a NG/air partially premixed flame. A series of homogeneous NG/air mixtures with different equivalence ratios were used to obtain the correlations between the measured emission lines of LIBS spectra and the global flame equivalence ratio. Consequently, the emission spectral lines ratios of H/N, H/O and C/N + O were utilized to predict the equivalence ratio distributions. The results demonstrated that for all of the mixing lengths, NG/air mixture with larger disk generator diameter yielded the maximum burner stability, whilst the LPG/air mixture with a larger disk generator diameter resulted in the minimum burner stability. Furthermore, the flame associated with the larger disk slit diameter had a uniform local equivalence ratio distribution and lower RMS fluctuation profiles of equivalence ratio in comparison to the lower disk slit diameter

Towards conceptual understanding for the adoption of building environmental sustainability assessment methods in the UAE built environment

The UAE is witnessing increased interest for sustainable development which poses challenges on the development processes for the large amount of built environment projects taking place in this emerging economy. While, great attention has been given to the development of tools and methods to measure and assess the performance of buildings to meet specific environmental sustainability targets, however, less is known about the effect of these assessment methods on the built environment development process itself. This paper addresses this gap through the investigation of the adoption of building environmental sustainability assessment methods for development projects in the UAE. Currently, there are two assessment methods in the UAE; Pearl Building Rating (PBR) and Al Sa'fat systems. Background study revealed that both systems: are developed in parallel to the development of building codes, adopt performance-based approach for assessment methods, and their adoption for development projects is basically mandatory. This paper draws from diffusion of innovations theory and growing literature in the adoption of similar assessment methods in projects, with the objective of proposing a conceptual framework that conceptualizes PBR and Al Sa'fat methods as innovations and the development projects as the social system for adoption, while focusing on the adoption process dynamics rather than the decision to adopt or not. The proposed framework captures specific conceptual themes, providing the foundation for further empirical investigation. As such, this paper contributes to the growing literature on the adoption of global energy assessment tools and specifically addresses the UAE's sustainable development policy and regulation

Management of congenital esophageal stenosis associated with esophageal atresia and its impact on postoperative esophageal stricture

Aim The aim of this work was to study the incidence, management of congenital esophageal stenosis (CES) associated with esophageal atresia (EA) and tracheoesophageal fistula (TEF), and its impact on esophageal stricture (ES) after primary repair.Patients and methods From January 2006 to December 2014, 41 sequential cases of EA with distal TEF were retrospectively studied. Cases with significant ES after primary repair were included in the study. Associated CES was diagnosed in the neonatal period by taking histopathologic samples from the tips of the esophageal pouches, failure to pass a size-6 nasogastric tube distally during primary repair, and by initial esophagogram.Results Significant ES developed in 19 patients (46.3%); of them, six had CES (32%). Three patients had tracheobronchial remnants at the anastomotic site. Two of them had refractory strictures requiring resections and one had mainly major esophageal dysmotility. Patients 4 and 5 had CES distal to the anastomotic site on initial esophagogram. Patient 4 responded well to dilatations, whereas the other one had refractory stricture. Patient 6 had distal CES due to fibromuscular stenosis diagnosed by failure to pass a size-6 nasogastric tube distally. The patient responded well to dilatation, myectomy, and Thal’s fundoplication.Conclusion One-third of the patients with significant stricture had CES; half of them were refractory to dilatation. Failure to have histology specimens and a high index of suspicion will make the incidence of this association a rarity. Diagnosis and management of CES with EA/TEF in the neonatal period is possible. Esophageal dilatation is the initial management for all cases with a low threshold for gastric fundoplication and gastrostomy. Resection is reserved for refractory stenosis.Keywords: congenital esophageal stenosis, esophageal atresia, esophageal stricture, tracheoesophageal fistul

Soil-raft foundation-structure interaction effects on seismic performance of multi-story MRF buildings

Recent studies show that the effects of Soil Structure Interaction (SSI) may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. Despite this, the conventional design procedure usually involves assumption of fixity at the base of foundation neglecting the flexibility of the foundation, the compressibility of soil mass and consequently the effect of foundation settlement on further redistribution of bending moment and shear force demands. The effects of SSI are analyzed for typical multi-story building resting on raft foundation. Three methods of analysis are used for seismic demands evaluation of the target moment resistant frame buildings: equivalent static load (ESL); response spectrum (RS) methods and nonlinear time history (TH) analysis with suit of nine time history records. Three-dimensional Finite Element (FE) model is constructed to analyze the effects of different soil conditions and number of stories on the vibration characteristics and seismic response demands of building structures. Numerical results obtained using soil structure interaction model conditions are compared to those corresponding to fixed-base support conditions. The peak responses of story shear, story moment, story displacement, story drift, moments at beam ends, as well as force of inner columns are analyzed

Six Cases of Fungal Peritonitis Complicating Peritoneal Dialysis in a Single Center in Sudan

Introduction: A national program of continuous ambulatory peritoneal dialysis (CAPD) has only recently been established in Sudan. In the head center of this national program, six of the 67 peritonitis episodes that were diagnosed during its 30 months of function were fungal in origin (9% of all episodes, 0.12 episode per year at risk). Here we describe the clinical features, predisposing factors, and outcomes of these six cases. Case series: Clinical presentation of fungal peritonitis did not differ from other cases of peritonitis. Among the six cases that were diagnosed in our center, five cases were due to Candida species and only one was due to Aspergillus. All patients had received antibiotic therapy within one month of diagnosing fungal peritonitis; five of them had received intraperitoneal (IP) antibiotics for a previous episode of bacterial peritonitis and one patient had received a course of oral antibiotics for exit site infection. Two of the patients were diabetic. All patients were treated with oral fluconazole, 200 mg daily, for three weeks, and all had their dialysis catheter removed. One patient died, and the others were transferred permanently to hemodialysis (HD). Two patients developed encysted intra-abdominal fluid collections 15 and 48 days after catheter removal. Conclusion: Fugal peritonitis complicating CAPD is not uncommon in our center, which serves a major portion of the CAPD population in the Sudan. Most patients responded to oral fluconazole treatment and catheter removal, but two of them suffered from late complications. Keywords: fungal peritonitis, peritoneal dialysis, Suda