Analisi comparativa di un circuito low pressure e high pressure EGR per un motore diesel sottostante a normativa americana US LEV III ULEV 125

Questa tesi di laurea nasce dall’esperienza maturata presso la VM Motori S.p.A., ufficio CRM (Centro Ricerca Motori) di ingegneria, divisione del reparto R&D (Research and Development) situato a Cento di Ferrara. Durante tale esperienza sono state affrontate le problematiche inerenti al settore automotive riguardo la ricerca e lo sviluppo dei motori endotermici diesel. Dopo un approccio introduttivo, che definisce l’ambito lavorativo in cui opera VM Motori S.p.A. e l’oggetto della tesi, si passa alla definizione ed alla calibrazione di un circuito low pressure EGR di un propulsore diesel da 200HP@3800rpm di potenza e 500Nm@1600rpm di coppia per uso automobilistico, mediante l’ausilio dei software AδαMO, INCA, Controldesk Next Generation, DoE, DIAdem ed INDICOM, software per lo studio della calibrazione al banco sviluppo. Si analizzano gli aspetti che contraddistinguono la VM Motori S.p.A. dalle altre aziende specializzate nel settore automotive, facendo riferimento ai campi produttivi in cui si applica l’ingegneria meccanica ed analizzandone gli aspetti tecnici, metodici e gestionali. Da notare il ruolo fondamentale delle automotive nell’economia mondiale in riferimento alla produzione dei principali propulsori diesel, primarie fonti produttive della VM.

Twenty years experience with an ileal orthotopic low pressure bladder substitute--lessons to be learned

PURPOSE: We present the long-term results of a large consecutive series of patients undergoing ileal orthotopic bladder substitution following radical cystectomy. MATERIALS AND METHODS: Between April 1985 and 2005 orthotopic bladder substitution with an ileal low pressure reservoir was performed in 482 patients (including 40 women) after radical and, if possible, nerve sparing cystectomy. In 447 cases the procedure was combined with an afferent ileal isoperistaltic tubular segment. The patients were followed prospectively. RESULTS: In the 482 patients 61 early (less than 30 days) diversion related complications requiring prolonged hospital stay or readmission were noted and 115 late complications required treatment. At 1 year continence was good in 92% of patients during the day and in 79% at night. At last followup 93% of patients could void spontaneously. Of 442 evaluable men 99 (22.4%) reported having erections without and 68 (15.4%) with medical assistance. Ureteroileal stenosis was observed in 12 of 447 (2.7%) patients. Urethral recurrence was detected in 25 of 482 (5%) patients. A total of 15 (5%) patients received vitamin B12 substitution. Renal parenchyma decreased only in patients with preoperative or postoperative ureteral obstruction. After 10 years patients with normal renal function had no long-term acidosis and in 20 patients the incidence of osteoporosis resembled that of the normal population. CONCLUSIONS: Ileal orthotopic bladder substitution combined with an afferent ileal tubular segment allows for good long-term functional results provided patients are restrictively selected, postoperative instructions are followed carefully, and typical complications such as outlet obstruction and hernias are treated early.

On the theory of high and low pressure areas: The significance of divergence in pressure areas

This is the edited and translated version of the article by Richard Scherhag “Zur Theorie der Hoch- und Tiefdruckgebiete. Die Bedeutung der Divergenz in Druckfeldern” (On the theory of high and low pressure areas: The significance of divergence in pressure areas), which was published in Meteorologische Zeitschrift 51, 129–138.

Low-pressure melting relations of a basalt from ODP Hole 127-797C

One-atmosphere melting experiments, controlled to approximately the fayalite-magnetite-quartz oxygen buffer, performed on a basalt from Hole 797C crystallized olivine and plagioclase nearly simultaneously from about 1235°C and augite from about 1175°C. The liquid compositions indicate systematic trends of increasing FeO and TiO2 and decreasing Al2O3 with decreasing MgO. Experimental olivine compositions vary from Fo90 to Fo78, plagioclase from An79 to An67, and augite from En49 to En46. The KD value for the Fe2+ and Mg distribution between olivine and liquid is 0.31. The KD value for the distribution of Fetotal and Mg between augite and liquid averages 0.24. These KD values suggest experimental equilibrium. The KD values for Na and Ca distribution between plagioclase and liquid range between 0.55 and 0.99 and are dependent on crystallization temperature. Projected on pseudoternary basaltic phase diagrams, the liquid line of descent moves toward increasing quartz normative compositions, revealing a typical tholeiitic crystallization trend with marked Fe and Ti enrichments. Such enrichments are a reflection of the dominance of plagioclase in the crystallizing assemblage. The experimental results can explain the marked Fe- and Ti-enrichment trends observed for the sills of the lower part of Hole 797C, but have no direct bearing on the origin of the relatively evolved high-Al basalts of Hole 794C.

Test time in low pressure shock tubes.

"SSD-TDR-62-204. Report no TDR-169 (3230-12)TN-5."

Water gravity waves generated by a moving low pressure area /

Mode of access: Internet.

Model study of water gravity waves generated by moving circular low pressure area /

Mode of access: Internet.

Rules and regulations relating to the handling of anhydrous ammonia and low pressure nitrogen solutions, equipment containers and storage facilities /

Cover title.

Physical Insights, Steady Aerodynamic Effects, and a Design Tool for Low-Pressure Turbine Flutter

The successful, efficient, and safe turbine design requires a thorough understanding of the underlying physical phenomena. This research investigates the physical understanding and parameters highly correlated to flutter, an aeroelastic instability prevalent among low pressure turbine (LPT) blades in both aircraft engines and power turbines. The modern way of determining whether a certain cascade of LPT blades is susceptible to flutter is through time-expensive computational fluid dynamics (CFD) codes. These codes converge to solution satisfying the Eulerian conservation equations subject to the boundary conditions of a nodal domain consisting fluid and solid wall particles. Most detailed CFD codes are accompanied by cryptic turbulence models, meticulous grid constructions, and elegant boundary condition enforcements all with one goal in mind: determine the sign (and therefore stability) of the aerodynamic damping. The main question being asked by the aeroelastician, ``is it positive or negative?'' This type of thought-process eventually gives rise to a black-box effect, leaving physical understanding behind. Therefore, the first part of this research aims to understand and reveal the physics behind LPT flutter in addition to several related topics including acoustic resonance effects. A percentage of this initial numerical investigation is completed using an influence coefficient approach to study the variation the work-per-cycle contributions of neighboring cascade blades to a reference airfoil. The second part of this research introduces new discoveries regarding the relationship between steady aerodynamic loading and negative aerodynamic damping. Using validated CFD codes as computational wind tunnels, a multitude of low-pressure turbine flutter parameters, such as reduced frequency, mode shape, and interblade phase angle, will be scrutinized across various airfoil geometries and steady operating conditions to reach new design guidelines regarding the influence of steady aerodynamic loading and LPT flutter. Many pressing topics influencing LPT flutter including shocks, their nonlinearity, and three-dimensionality are also addressed along the way. The work is concluded by introducing a useful preliminary design tool that can estimate within seconds the entire aerodynamic damping versus nodal diameter curve for a given three-dimensional cascade.

Computational modelling of non-equilibrium condensing steam flows in low-pressure steam turbines

The steam turbines play a significant role in global power generation. Especially, research on low pressure (LP) steam turbine stages is of special importance for steam turbine man- ufactures, vendors, power plant owners and the scientific community due to their lower efficiency than the high pressure steam turbine stages. Because of condensation, the last stages of LP turbine experience irreversible thermodynamic losses, aerodynamic losses and erosion in turbine blades. Additionally, an LP steam turbine requires maintenance due to moisture generation, and therefore, it is also affecting on the turbine reliability. Therefore, the design of energy efficient LP steam turbines requires a comprehensive analysis of condensation phenomena and corresponding losses occurring in the steam tur- bine either by experiments or with numerical simulations. The aim of the present work is to apply computational fluid dynamics (CFD) to enhance the existing knowledge and understanding of condensing steam flows and loss mechanisms that occur due to the irre- versible heat and mass transfer during the condensation process in an LP steam turbine. Throughout this work, two commercial CFD codes were used to model non-equilibrium condensing steam flows. The Eulerian-Eulerian approach was utilised in which the mix- ture of vapour and liquid phases was solved by Reynolds-averaged Navier-Stokes equa- tions. The nucleation process was modelled with the classical nucleation theory, and two different droplet growth models were used to predict the droplet growth rate. The flow turbulence was solved by employing the standard k-ε and the shear stress transport k-ω turbulence models. Further, both models were modified and implemented in the CFD codes. The thermodynamic properties of vapour and liquid phases were evaluated with real gas models. In this thesis, various topics, namely the influence of real gas properties, turbulence mod- elling, unsteadiness and the blade trailing edge shape on wet-steam flows, are studied with different convergent-divergent nozzles, turbine stator cascade and 3D turbine stator-rotor stage. The simulated results of this study were evaluated and discussed together with the available experimental data in the literature. The grid independence study revealed that an adequate grid size is required to capture correct trends of condensation phenomena in LP turbine flows. The study shows that accurate real gas properties are important for the precise modelling of non-equilibrium condensing steam flows. The turbulence modelling revealed that the flow expansion and subsequently the rate of formation of liquid droplet nuclei and its growth process were affected by the turbulence modelling. The losses were rather sensitive to turbulence modelling as well. Based on the presented results, it could be observed that the correct computational prediction of wet-steam flows in the LP turbine requires the turbulence to be modelled accurately. The trailing edge shape of the LP turbine blades influenced the liquid droplet formulation, distribution and sizes, and loss generation. The study shows that the semicircular trailing edge shape predicted the smallest droplet sizes. The square trailing edge shape estimated greater losses. The analysis of steady and unsteady calculations of wet-steam flow exhibited that in unsteady simulations, the interaction of wakes in the rotor blade row affected the flow field. The flow unsteadiness influenced the nucleation and droplet growth processes due to the fluctuation in the Wilson point.

Atmospheric pressure plasma chemical vapor deposition reactor for 100 mm wafers, optimized for minimum contamination at low gas flow rates

Gas discharge plasmas used for thinfilm deposition by plasma-enhanced chemical vapor deposition (PECVD) must be devoid of contaminants, like dust or active species which disturb the intended chemical reaction. In atmospheric pressure plasma systems employing an inert gas, the main source of such contamination is the residual air inside the system. To enable the construction of an atmospheric pressure plasma (APP) system with minimal contamination, we have carried out fluid dynamic simulation of the APP chamber into which an inert gas is injected at different mass flow rates. On the basis of the simulation results, we have designed and built a simple, scaled APP system, which is capable of holding a 100 mm substrate wafer, so that the presence of air (contamination) in the APP chamber is minimized with as low a flow rate of argon as possible. This is examined systematically by examining optical emission from the plasma as a function of inert gas flow rate. It is found that optical emission from the plasma shows the presence of atmospheric air, if the inlet argon flow rate is lowered below 300 sccm. That there is minimal contamination of the APP reactor built here, was verified by conducting an atmospheric pressure PECVD process under acetylene flow, combined with argon flow at 100 sccm and 500 sccm. The deposition of a polymer coating is confirmed by infrared spectroscopy. X-ray photoelectron spectroscopy shows that the polymer coating contains only 5% of oxygen, which is comparable to the oxygen content in polymer deposits obtained in low-pressure PECVD systems. (C) 2015 AIP Publishing LLC.