Applied and Industrial Fluid-Dynamics Ref.

To request a copy of a publication send an email to antonio.ficarella02@gmail.com.

2015

"An improved parameter identification schema for the dynamic model of LD converters", Antonio Paolo Carlucci; Antonio Ficarella; Giovanni Indiveri; Paolo Presicce, JOURNAL OF PROCESS CONTROL, 31, 64-72, 2015.

The process of conversion in Linz–Donawitz converters is a crucial stage in the production of steel: oxygen is blown on the surface of the melted bath in order to reduce the carbon concentration. At the same time, suitable amounts of coolants are added in order to govern the increase of the bath temperature and reduce the impurities (favoring the slag formation). The aim is to direct the bath of melted steel to the desired final condition, in terms of temperature and carbon content. At around 92–93% of the complete process of conversion, the oxygen blowing is suspended and the In-Blow is performed, i.e. a steel sample is collected by means of a lance introduced in the melted bath and its carbon percentage and temperature measured. A dynamic model, through two characteristic equations, describes the evolution of the carbon percentage and temperature of the melted steel during the final phase of the conversion process, i.e. from the In-Blow until the end. Based on this model, the volume of oxygen to be blown during this phase and the amount of coolant to be added in order to reach the required final (End-Point) conditions of carbon percentage and temperature can be calculated. The model is nonlinear and depends on four parameters to be estimated. Based on a dimensional analysis and on a large set of experimental data, the nominal model has been modified introducing the hypothesis that the parameters are not constant, but depend on the temperature. Within this framework the novel model is identified exploiting Least Squares (LS) methods and its output is compared with the existing practice.

2010 and before

“TheEffects of Distributor and Striking Mass on the Performance of aHydraulic Impact Machine”, A. Ficarella, A. Giuffrida, D. Laforgia, SAE PAPER 2008-01-2679, Commercial Vehicle Engineering Congress & Exhibition, October 2008, Chicago, IL, USA.

This paper deals with numerical investigations concerning the working behavior of a hydraulic impact machine. Attention is focused on the moving elements inside the casing of the breaker, taking the main targets to be achieved by the designer into account. On one hand, there is the operating performance optimization, with particular care devoted to the impact energy of the breaker; on the other hand, the energy conversion efficiency, related to the power transmission, in order to minimize the power requirement to the feeding system. Use of a parameterized numerical model is made in order to better understand the effects of parameters characteristic of distributor and striking mass on breaker performance and to achieve possible improvements in both impact energy and efficiency. The key-variable, which leads to better performance, is found to be the working pressure.

“Investigationon the Impact Energy of a Hydraulic Breaker”, A. Ficarella, A. Giuffrida, D. Laforgia, (SAE paper 2007-01-4229), 2007 SAE Commercial Vehicle Engineering Conference, Rosemont, Illinois (USA), Oct. 30th – Nov. 1st, 2007.

Percussive breaking is basically a process in which short duration blows with high force intensity are applied in rapid succession, resulting in rock, concrete or pavement fragmentation. The machine for such a task is

the hydraulic breaker which turns the hydraulic energy supplied by a positive displacement pump into mechanical energy as percussions of a piston against a chisel.

This work presents the results of experimental tests carried out on a hydraulic breaker to determine its blow impact energy. Then, using these data, theoretical considerations are formulated in order to understand the

phenomenon of the tool loading especially at the instant of the impact of the piston against the chisel, leading to the energy release.

“Numerical Investigations on the Working Cycle of a Hydraulic Breaker:Off-Design Performance and Influence of Design Parameters”, A. Giuffrida, A. Ficarella, D. Laforgia, International Journal of Fluid Power, 7 (2006), No. 3, pp. 41-50.

This paper deals with theoretical considerations and numerical simulations concerning the working behaviour of a hydraulic breaker. At first, some formulations coming from sufficiently reasonable considerations on the working principle of the breaker, based on the hypothesis of the motion of the striking mass as uniformly accelerated, are proposed.

Later, a previously realized parameterised model is used in order to investigate the influence of the inlet flow rate and of the most important design parameters on the behaviour of the machine. This analysis allows the characterization of these parameters affecting breaker performance, suggesting possible design improvements which may lead to better performance in terms of both impact energy and efficiency.

“Numerical Study of the Extrusion Process in Cereals Production: Part I.Fluid-dynamic Analysis of the Extrusion Systems”, A. Ficarella, M. Milanese e D. Laforgia, Journal of Food Engineering, Vol. 73, pp. 103-111, 2006.

A numerical investigation on the extrusion cooking process for cereals in a co-rotating twin-screw extruder was carried out, using a fluid-dynamic, numerical simulation model. Simulation tests were carried out, varying temperature, screw rotation velocity, mass flow rate and extruder geometry. Fluid-dynamic parameters inside the extruder, as shear rate, residence time and mixing index were

evaluated.

Extruder geometry is an important parameter in the extrusion process, since it affects the values of shear rate and residence time and consequently the quality of the final product. Screw with regular geometry shows a more regular profile of the mean shear rate along the extruder, but characterized by lower values of this parameter, determining a reduced gelatinization of the compound.

Instead, extruders characterized by a more complex geometry allow to obtain higher values of shear rate, but with some difficulties in the control of the final quality of the products due to a more complex behavior of the shear rate profile along the screw axis.

“NumericalStudy of the Extrusion Process in Cereals Production: Part II.Analysis of Variance”, A.Ficarella, M. Milanese e D. Laforgia, Journal of Food Engineering, Vol. 72, pp. 179-188, 2006.

Extrusion cooking of cereals is a complex process, regarding a wide range of food products (snack-foods, baby-foods, cereals for breakfast and pasta). In this work, an analysis of variance (ANOVA) on the extrusion cookingprocess for cereals in a co-rotating twin-screw extruder was carried out, usinga finite-element fluid dynamic simulation model, to study shear rate, residence time and mixingindex inside the extruder, varyingtemperature, screw rotation velocity, flow rate and extruder geometry.

Besides, the significance analysis, carried out in this study, have shown several aspects of the process under investigation: (i) the interdependence between shear rate, screw rotation velocity and screw axis ratio seems very strong; (ii) the significance of the effects on shear rate of the variations of temperature and flow rate appears less meaningful; (iii) the influence on the residence time of the flow rate and screw axis ratio is more meaningful respect to the screw speed and temperature.

The numerical simulations have revealed numerous aspects that can be used to improve the extrusion process: the flow temperature can be varied without modifyingthe gelatinization of material that is mainly influenced by screw rotation velocity and screw axis ratio.

“NumericalAnalysis of a Cross-Flow Compact Heat Exchanger for VehicleApplications”, E. Carluccio, G. Starace, A. Ficarella, D. Laforgia, Applied Thermal Engineering, 25 (13), p.1995-2013, Sep 2005.

A numerical thermo-fluid–dynamic study of a compact crossed flows heat exchanger (HX), used to cool the high-pressure oil used in hydraulic circuits of earth-movement industrial vehicles, was performed.

The numerical analysis was carried out to verify the influence of the hydrodynamic regimes of the fluids involved in the heat transfer process, induced by fins in the channels, on the performances of the whole HX.

The analysis was developed through three steps of increasing complexity. After a simple model built to evaluate the consistent boundary conditions of temperature, a small scale analysis of the fluid–dynamic phenomena inside the HX was carried out, taking into account geometrical periodical units at oil (OS) and at air side (AS). With the results obtained in this way, the HX performances were evaluated on an overall

scale, extrapolating the data up to the real dimensions in terms of heat transfer and pressure loss.

With the ‘‘small scale’’ approach at the OS the local heat flux and the pressure losses were quantified, using a laminar scheme and a high detail in the geometry description of the turbulence generators. With

the ‘‘full scale’’ approach, then, simulations were performed considering a porous media with characteristics set up on the previous analysis. The global heat transfer coefficient and the pressure losses were so

accounted for.

At the AS, the schematization was limited to two periodic portions of the flow and results allowed to evaluate both local and overall heat transfer coefficients. Results were again extrapolated to the real dimensions of the channels.

“Application ofMultiphase CFD Modeling to Naval Design in Presence of Cavitation”, M.G. De Giorgi, A. Ficarella, D. Laforgia, TCN CAE 2005 International Conference on CAE and Computational Technologies for Industry, October 5-8, 2005, Lecce, Italy.

In the design process of a wide variety of fluid machinery, as the naval profiles under investigations, the occurrence of cavitation is one of the most important aspects that need to be considered. Cavitation of marine propellers can cause many problems, such as vibration, noise, and erosion on the blades. Marine propeller researchers and designers have made numerous efforts to reduce the effects of cavitation. However, with recent high-speed and shallow-draft ships, it is difficult to avoid cavitation without compromising the propeller efficiency. Different efforts have been given in literature to simulate cavitating flows with Computational Fluid Dynamics (CFD) methods. However, validation of computational results with experimental data is very fragmentary in many papers. The main cause is the lack of experimental data. This means that at present,

uncertainty exists on the adequacy of the physical models applied to describe the cavitation dynamics. Therefore, the aim of this work is the investigation of currently known cavitation models and the implementation of these models in a commercial CFD code. Final validation results are presented for flows over hydrofoils. For each case, experimental data are compared. In general, the results are very promising. Several aspects

of cavitation phenomena, of fundamental importance for the profiles design, can be accurately captured with the developed cavitation models.

“Monitoring the Drying Process of Lasagna Pasta thought A Novel SensingDevice-Based Method”, A. Sannino, S. Capone, P. Siciliano, A. Ficarella, L. Vasanelli, A. Maffezzoli, Journal of Food Engineering, Vol. 69, pp. 51-59, 2005.

The desiccation process of lasagna pasta is usually accompanied by bending and breaking of the dry pasta slices, due to self generated internal stress. The diffusive transfer of water through the slice bulk is responsible of these phenomena, leading to excessive product reject. The water sorption equilibrium and kinetics of drying were measured for different pasta mixtures. Measurements have been performed by means of a novel equipment based on a raw alumina substrate (3 · 3mm sized) equipped with gold interdigitated electrodes, and a strict analogy exists between current and water diffusion data. Moreover, in situ measurements have been performed in an Italian pasta factory with an on line system assembled on the desiccation apparatus.

Results of the sorption studies show a Case II diffusion mechanism, with the formation of a glassy shell around the pasta sample during desiccation at low water vapour activities, which prevents the further desiccation of the internal humid core. Thus, an accurate control of the humidity both in the sample and the external environment was performed to avoid stress generation in the material and cracks formation. The measuring device provided an accurate control of the sample humidity and a fast response to external environment modifications during desiccation.

“Application and Impacts of a Real Fire in a Residential Building for Analysis the Level of Risk for Life”, A. Ficarella, R. Lala, A. Perago, D. Laforgia, Proceedings of the Conference on Probabilistic Safety Assessment, Berlin (Germany), June 2004.

High temperature, smoke and fire gases, inherent in all unwanted fires, are dangerous products of combustion that have critical influences on life safety, property protection, response of structure and fire suppression practices in buildings. In some fires, the volume of smoke is so great that it may fill an entire building and obscure visibility at the street level to such an extent that it is difficult to identify the fire-involved building. An experimental campaign was performed to analyse the flows of smoke and the time variation of the temperature due to a fire in a building, monitoring of smoke flow evolution and temperature trends on the walls

during controlled fires with different ventilation conditions in office. The used instrumentation, positioned near place where has developed the fire, he has allowed of to pick up data on temperature on the walls, composition of the smokes; particularly, for the analysis of the smokes have been measured the concentrations of O2, CO, CO2, HC. The results of the experiments have allowed the detailed analysis of the characteristics of the propagation of smoke in relationship to the degree of opening of doors and windows of the building and the distribution of the temperature on the wall of building.

“Fluid-dynamicAnalysis and Optimization of the Quenching Process for Hardening ofChange-Speed Gears using DOE – ANOVA method”, P. M. Congedo, A. Ficarella, D. Laforgia, ASME Journal of Heat Transfer, vol. 126, pp. 365-375, June 2004.

This investigation deals with the fluid-dynamic behavior of the hardening process for change-speed gears, where a Nitrogen high pressure flow is used for quenching. At the end of the process, the gears showed a high planarity error due to a slow and nonhomogeneous cooling process. A detailed fluid-dynamic calculation was performed to identify some possible technical improvements, such as varying some design parameters

including the geometry configuration of the quenching chamber and the operating conditions.

Three performance indexes have been defined to synthesize the quality of the hardening process and their trends have been evaluated as a function of the design and operative configuration by a DOE–ANOVA statistical analysis to obtain the best configuration.

“Thermo-Fluid-DynamicInvestigation of a Dryer, Using Numerical and Experimental Approach”, A. Ficarella, A. Perago, G. Starace, D. Laforgia, 15th International Conference on Efficiency, Costs, Optimization, Simulation and Environmental Impact of Energy Systems, ECOS 2002, Berlin, Germany, 3-5 luglio 2002. Pubblicato nel Journal of Food Engineering, n. 59, pp. 413-420, Oct. 2003.

The thermo-fluid-dynamic behavior of a dryer, used for the production of a special kind of alimentary pasta (lasagna), was analyzed, performing both numerical simulations and experimental investigations, in order to improve the dryer thermal performance. In particular, the achievable improvements in terms of temperature distribution, obtained by modifying the control of air distribution and the geometry of air distribution channels, were analyzed. The numerical simulation suggested the design of some modifications of the actual dryer. Particularly, the air distribution was improved and the natural vertical stratification of the drying air was reduced, implementing a new geometrical configuration with some vertical and horizontal panels. An experimental campaign on the dryer was carried out, confirming the trends obtained using the computer code. The percentage of pasta defects was reduced from 30% down to 10% thanks to a more controlled air distribution.