Flashback analysis and avoidance in swirl burners

This study is aimed to investigate and demonstrate the feasibility and validity of various flame flashback resistance techniques for premixed fuel conditions. It presents a series of experiments to determine the impact of different configurations on flame flashback mechanisms. Experiments were performed using a 150 kW tangential swirl burner working on premixed mode with various swirl numbers; the flow field characteristics were measured by 1D LDA. The first part of the project targeted the effect of central fuel injector geometries on flame flashback mechanisms, especially combustion induced vortex breakdown (CIVB). It was found that changing the central fuel injector outside diameter can significantly alter the flame flashback mechanism. Large injector diameters result in boundary layer flashback (BLF), contrary, the use of small injectors diameter led to CIVB. Thus a dimensionless number (χ) which represent the ratio between the injector outside diameter and the nozzle inside diameter was introduced. Using this dimensionless number the critical value of transition from CIVB to BLF has been defined, the value being χ= 0.280 for Sg=1.12 and χ= 0.320 for Sg= 0.9. The second part was about the effect of using axial air injection instead of central fuel injectors. It was found that axial air jets have a considerable potential for flame stability requirements, they producing wider stability operation than that of central injectors. Moreover, the stability limits increase regarding both equivalence ratio and inlet tangential velocity. It appeared that using such air jets could reduce the combustor maintenance cost that arises due to a continuous harsh environment. However, it was found that axial air jets could enforce flame propagation during flashback via wall boundary layer. Thus, the third part of the study was about the validity of using micromeshes to improve BLF resistance in addition to axial air injection. It was found that using both techniques produced high flashback resistance for both mechanisms, i.e. CIVB and BLF

Endoscopic Management of Spontaneous Clival Cerebrospinal Fluid Leaks: Case Series and Literature Review

Abstract OBJECTIVE: Spontaneous cerebrospinal fluid leaks are most commonly located along the anterior skull base. Sphenoidal localization is less common, and clival localization is even rarer. We analyzed a group of patients with spontaneous leaks and selected patients with clival localization. This article discusses surgical management of these entities and provides a brief literature review regarding spontaneous clival leaks. METHODS: Of a cohort of 67 patients who presented to our departments with a spontaneous leak during the period 2005-2014, a retrospective data analysis was performed on 6 patients with clival localization of the defect. A skull base repair with a multilayered reconstruction was performed in 3 patients, and a single-layered reconstruction using a pedicled nasoseptal flap was performed in 3 patients. RESULTS: The patients included 6 women with a mean age of 60 years (range, 36-91 years). The mean length of the follow-up period was 69.5 months (range, 22-114 months). The overall success rate of the primary endoscopic repair was 83.3% (5 of 6 patients); this increased to 100% after revision surgery. CONCLUSIONS: This series, although numerically limited, suggests that a minimally invasive endoscopic repair of idiopathic clival leaks may be accomplished with an acceptable rate of morbidity and excellent outcomes. Moreover, the pedicled nasoseptal flap has been confirmed to be the "workhorse" for the reconstruction of clival defects

HPV impact on oropharyngeal cancer radiological staging: 7th vs 8th edition of AJCC TNM classification

Purpose: To evaluate the agreement between pathological and radiological staging in oropharyngeal cancer by comparing the 7th and the 8th edition of the AJCC TNM system. Methods: This retrospective cohort study included 57 cases of oropharyngeal cancer with lymph node metastases staged with the 7th and 8th editions of the AJCC TNM system. Comparison between clinical and radiological features and differences in agreement rates were calculated between radiological and pathological staging for the primary tumor (T) and lymph nodes (N) in HPVpos and HPVneg cases. Results: Comparison of HPVpos and HPVneg revealed a significantly different distribution between early and advanced stages in the 8 th edition, with a relevant number of HPVpos patients redefined from advanced stages whit the 7 th ed. to early stages with 8 th ed. (p < 0.01); no significant differences were found when comparing all diagnostic methods for T and N. Conclusions: The 8th edition of the AJCC TNM seems to lead to better pretreatment staging. For both HPVpos and HPVneg, the agreement between pretreatment radiological and pathological staging

"TuNa-saving" endoscopic medial maxillectomy: a surgical technique for maxillary inverted papilloma

The maxillary sinus is the most common site of sinonasal inverted papilloma. Endoscopic sinus surgery, in particular endoscopic medial maxillectomy, is currently the gold standard for treatment of maxillary sinus papilloma. Although a common technique, complications such as stenosis of the lacrimal pathway and consequent development of epiphora are still possible. To avoid these problems, we propose a modification of this surgical technique that preserves the head of the inferior turbinate and the nasolacrimal duct. A retrospective analysis was performed on patients treated for maxillary inverted papilloma in three tertiary medical centres between 2006 and 2014. Pedicle-oriented endoscopic surgery principles were applied and, in select cases where the tumour pedicle was located on the anterior wall, a modified endoscopic medial maxillectomy was carried out as described in this paper. From 2006 to 2014 a total of 84 patients were treated. A standard endoscopic medial maxillectomy was performed in 55 patients (65.4%), while the remaining 29 (34.6%) had a modified technique performed. Three recurrences (3/84; 3.6%) were observed after a minimum follow-up of 24 months. A new surgical approach for select cases of maxillary sinus inverted papilloma is proposed in this paper. In this technique, the endoscopic medial maxillectomy was performed while preserving the head of the inferior turbinate and the nasolacrimal duct ("TuNa-saving"). This technique allowed for good visualization of the maxillary sinus, good oncological control and a reduction in the rate of complications

Deep Neck Abscesses in Children

Retropharyngeal and parapharyngeal abscesses (RPAs, PPAs) usually affect young children. Surgical drainage and/or antibiotic therapy are treatment of choice, but no specific guidelines exist. In order to reduce the risk of severe complications, appropriate diagnosis and therapy are necessary. The aims of the study were to review diagnosis and management of children with RPAs/PPAs and to compare surgical versus medical approach

Deep Neck Abscesses in Children: An Italian Retrospective Study

Retropharyngeal and parapharyngeal abscesses (RPAs, PPAs) usually affect young children. Surgical drainage and/or antibiotic therapy are treatment of choice, but no specific guidelines exist. In order to reduce the risk of severe complications, appropriate diagnosis and therapy are necessary. The aims of the study were to review diagnosis and management of children with RPAs/PPAs and to compare surgical versus medical approach