Metodologie di progettazione -Knowledge based- applicate a pompe centrifughe

La presente tesi di Laurea riguarda l’analisi delle metodologie di progettazione meccanica “knowledge based” applicate a pompe centrifughe. In particolare l’attività svolta ha permesso di determinare delle regole di progettazione per incrementare l’NPSH di una pompa centrifuga. Le regole sono state ottenute mediante simulazioni fluidodinamiche con il codice “Fluent”. La pompa centrifuga presa a riferimento è la “JETINOX 50/60M“ prodotta dalla ditta Nocchi s.p.a. L’incremento di NPSH è ottenuto mediante l’inserimento di un eiettore (“jet pump”) , a monte della girante, che utilizza come fluido motore una parte della portata di mandata della pompa. La geometria dell’eiettore è stata riprodotta mediante un processo di “Reverse Engineering”. Il modello numerico è stato implementato nel codice CFD e le simulazioni hanno permesso di calcolare la pressione , la velocità del fluido e la potenza spesa all’interno dei condotti. Dall’elaborazione dei risultati è stato determinato l’incremento di NPSH della pompa alle condizioni di funzionamento nominali. Analisi parametriche relative alle caratteristiche geometriche dell’eiettore hanno permesso un dimensionamento ottimale della pompa ai fini dell’incremento di NPSH. Abstract This thesis deals with the analysis of the Knowledge based method applied to mechanical design of centrifugal pumps. In detail , this work has allowed to establish design rules,( by means of fluidodinamic simulations with the code Fluent) in order to achieve an increment of NPSH of the centrifugal pump. The centrifugal pump taken in exam is an "JETINOX 50/60M" produced by Nocchi s.p.a. An increment on the NPSH is obtained by means of the insertion of an ejector (jet pump), located before the impeller. The jet pump uses as driven fluid a part of outlet flow rate. The geometry of the ejector has been reproduced by means of “Reverse Engineering” method. The numerical model has been implemented in the CFD code , the simulations have allowed to calculate the pressure , the velocity of the fluid and the power absorbed by the jet pump. An elaboration of the results has allowed to determine the increment of NPSH of the centrifugal pump at design operation conditions. Parametric analyses of the geometric characteristics of the ejector have allowed to find the optimal pump design in order to increment the NPSH

Medium-Long-Term Radiographic and Clinical Outcomes after Surgical Treatment of Intra-Articular Tibial Pilon Fractures by Three Different Techniques

The goal of this retrospective, observational, case series study was to evaluate the medium-long-term clinical and radiographic results of the three most common surgical osteosynthesis techniques used for the treatment of articular tibial pilon fractures: ORIF, MIPO, and EF. Materials and Methods. A consecutive series of patients with articular pilon fractures who underwent surgery at our institution were enrolled in this study. Fractures were classified according to the M\ufcller AO classification system. Overall outcomes took the following into account: radiographic quality of reduction, evaluated using Ovadia and Beals\u2019 criteria; clinical assessment, evaluated using the AOFAS questionnaire; and general health, evaluated with the SF36-v2 Health Survey. Results. A total of 94 articular pilon fractures (34 type 43-B and 60 43-C) were evaluated with a mean follow-up of 56.34 months (range 33\u2013101). The techniques used were ORIF, MIPO, and EF in 63 (67%), 17 (18.9%), and 14 cases (14.1%), respectively. According to Ovadia and Beals\u2019 criteria, good, fair, and poor results were reported in 61 (64.89%), 26 (27.66%), and 7 (7.45%) cases, respectively. The mean AOFAS score was 82.41 for MIPO, 79.83 for ORIF, and 50.57 for EF, respectively. Thirty-nine patients (41.49%) presented early and/or late complications. Conclusion. Satisfactory outcomes using the three different techniques were reported. In particular, the radiographic outcomes were inversely proportional to the fracture comminutions and statistically different between internal and external osteosynthesis, but comparable between ORIF and MIPO techniques. On the other hand, the clinical outcomes were closely related to the soft tissue conditions and the anatomical reconstruction of the joint