Characterisation in water experiments of a “detached flow” free surface spallation target

In the development of accelerator driven systems, ADS, free surface lead–bismuth spallation targets are considered as promising solutions due to their possibility for compactness, their lifetime, and their ability to transport the heat deposited by the proton beam away from the spallation zone. Experiments to characterise the hydraulics of the targets are needed to allow the validation of numerical models and to improve the design. Such experiments have been performed in water on a new concept labelled “detached flow” geometry. This name was chosen because the liquid undergoes a free fall between the nozzle exit where the main free surface (that separating the void of the beam line from the liquid) is created and a second free surface downstream. The void surrounding the liquid jet plays the role of a buffer. The experiments show that a very stable main free surface with a small recirculation is obtained using this geometry thanks to the presence of the second free surface and the nozzle geometry. The experiments confirm that the level of the second free surface has no influence on the characteristics of the main free surface, improving the main free surface control. The influences of the mass flow rate and of the inlet velocity are evaluated. The free surface level rises linearly with an increase in mass flow rate. The recirculation zone is also stronger in this case. The opposite is found when the mass flow rate is decreased. For all mass flow rates studied, a stable free surface is obtained. Moreover, the outer shape of the liquid jet is similar at all mass flow rates. It is only dictated by the nozzle exit angle. Increasing slightly the inlet velocity for a given mass flow rate has a positive effect on the recirculation stability. The “detached flow” target is a promising design for ADS

Simulation of Wood Logs Combustion in a Stove at Peak Pyrolysis Conditions

Transient wood combustion may lead to excessive carbon monoxide and particle emissions, that could hinder the use of wood in small scale applications. The development of innovative and advanced designs meeting the future standards requires a more detailed knowledge of the flow, temperature, and species fields. Steady fluid dynamics numerical simulations of wood log combustion in a stove have been carried out at peak pyrolysis conditions. The ANSYS Fluent software has been used with a simplified kinetic model for the combustion of the pyrolysis gases. While the numerical model is rather simplified in terms of heat transfer, the essential features of the flow and combustion are well caught thanks to the detailed input for the pyrolysis gases. However, the carbon monoxide concentration at the chimney is higher compared to experimental data

Tricuspidation of quadricuspid aortic valve: case reports.

Quadricuspid aortic valve in adulthood is a rare pathology which often leads to aortic valve regurgitation that requires surgical treatment. Herein are described two patients with severe regurgitation on a quadricuspid aortic valve and with dilated left ventricle, who where successfully repaired using a technique of tricuspidation of the valve at the level of the abnormal commissure. In each patient, the repair was stabilized and leaflet coaptation increased by subcommissural annuloplasty stitches at the level of the three commissures. After one year and six months' follow up, respectively, both patients presented with trivial aortic regurgitation and good mobility of the three leaflets

Development of new clean and high-efficiency combustion systems operating with non conventional fuels

0info:eu-repo/semantics/nonPublishe

Aortic valve repair: the functional approach to leaflet prolapse and valve-sparing surgery.

BACKGROUND: Combined aortic valve repair and aortic valve-sparing surgery requires an approach determined by the leaflets and aortic root anatomy. METHODS: Among patients referred for aortic root aneurysm, 114 patients underwent an aortic valve-sparing procedure in which a reimplantation or remodelling technique was used. The Gelweave Valsalva prosthesis (Sulzer Vascutek, Renfrewshire, UK) was used in 45 patients. Better molding of the prosthesis on the aortic annulus was achieved by a low proximal dissection and incisions on the prosthesis to respect the anatomy of the aortoventricular junction. The reimplantation technique was used in 58%, and 62% of all patients underwent an associated leaflet procedure. RESULTS: The operative mortality rate was 1%, with a 2% immediate reoperation rate. During the mean follow-up 50 +/- 35 months, 3 patients (2.6%) needed reoperation for recurrent aortic regurgitation (n = 2) or aortic stenosis (n = 1). At the end of follow-up, aortic regurgitation grade exceeding 2 had occurred in 2.6% of patients (n = 3), and 98.2% were in New York Heart Association functional class 1 or 2. Neither the early nor mid-term results showed any differences among the different surgical techniques used (reimplantation, remodeling, Valsalva prosthesis, additional leaflet repair). CONCLUSIONS: A complete approach to the different components of the aortic root allows good clinical results at mid-term