Sulla ricerca del minimo dei consumi per vetture sportive

La ricerca oggetto di questa tesi, come si evince dal titolo stesso, �� volta alla riduzione dei consumi per vetture a forte carattere sportivo ed elevate prestazioni specifiche. In particolare, tutte le attivit�� descritte fanno riferimento ad un ben definito modello di vettura, ovvero la Maserati Quattroporte. Lo scenario all���interno del quale questo lavoro si inquadra, �� quello di una forte spinta alla riduzione dei cosiddetti gas serra, ossia dell���anidride carbonica, in linea con quelle che sono le disposizioni dettate dal protocollo di Kyoto. La necessit�� di ridurre l���immissione in atmosfera di CO2 sta condizionando tutti i settori della societ��: dal riscaldamento degli edifici privati a quello degli stabilimenti industriali, dalla generazione di energia ai processi produttivi in senso lato. Nell���ambito di questo panorama, chiaramente, sono chiamati ad uno sforzo considerevole i costruttori di automobili, alle quali �� imputata una percentuale considerevole dell���anidride carbonica prodotta ogni giorno e riversata nell���atmosfera. Al delicato problema inquinamento ne va aggiunto uno forse ancor pi�� contingente e diretto, legato a ragioni di carattere economico. I combustibili fossili, come tutti sanno, sono una fonte di energia non rinnovabile, la cui disponibilit�� �� legata a giacimenti situati in opportune zone del pianeta e non inesauribili. Per di pi��, la situazione socio politica che il medio oriente sta affrontando, unita alla crescente domanda da parte di quei paesi in cui il processo di industrializzazione �� partito da poco a ritmi vertiginosi, hanno letteralmente fatto lievitare il prezzo del petrolio. A causa di ci��, avere una vettura efficiente in senso lato e, quindi, a ridotti consumi, �� a tutti gli effetti un contenuto di prodotto apprezzato dal punto di vista del marketing, anche per i segmenti vettura pi�� alti. Nell���ambito di questa ricerca il problema dei consumi �� stato affrontato come una conseguenza del comportamento globale della vettura in termini di efficienza, valutando il miglior compromesso fra le diverse aree funzionali costituenti il veicolo. Una parte consistente del lavoro �� stata dedicata alla messa a punto di un modello di calcolo, attraverso il quale eseguire una serie di analisi di sensibilit�� sull���influenza dei diversi parametri vettura sul consumo complessivo di carburante. Sulla base di tali indicazioni, �� stata proposta una modifica dei rapporti del cambio elettro-attuato con lo scopo di ottimizzare il compromesso tra consumi e prestazioni, senza inficiare considerevolmente queste ultime. La soluzione proposta �� stata effettivamente realizzata e provata su vettura, dando la possibilit�� di verificare i risultati ed operare un���approfondita attivit�� di correlazione del modello di calcolo per i consumi. Il beneficio ottenuto in termini di autonomia �� stato decisamente significativo con riferimento sia ai cicli di omologazione europei, che a quelli statunitensi. Sono state inoltre analizzate le ripercussioni dal punto di vista delle prestazioni ed anche in questo caso i numerosi dati rilevati hanno permesso di migliorare il livello di correlazione del modello di simulazione per le prestazioni. La vettura con la nuova rapportatura proposta �� stata poi confrontata con un prototipo di Maserati Quattroporte avente cambio automatico e convertitore di coppia. Questa ulteriore attivit�� ha permesso di valutare il differente comportamento tra le due soluzioni, sia in termini di consumo istantaneo, che di consumo complessivo rilevato durante le principali missioni su banco a rulli previste dalle normative. L���ultima sezione del lavoro �� stata dedicata alla valutazione dell���efficienza energetica del sistema vettura, intesa come resistenza all���avanzamento incontrata durante il moto ad una determinata velocit��. Sono state indagate sperimentalmente le curve di ���coast down��� della Quattroporte e di alcune concorrenti e sono stati proposti degli interventi volti alla riduzione del coefficiente di penetrazione aerodinamica, pur con il vincolo di non alterare lo stile vettura.

A study on the fluid dynamics of domestic Gas burners

Domestic gas burners are investigated experimentally and numerically in order to further understand the fluid dynamics processes that drive the cooking appliance performances. In particular, a numerical simulation tool has been developed in order to predict the onset of two flame instabilities which may deteriorate the performances of the burner: the flame back and flame lift. The numerical model has been firstly validated by comparing the simulated flow field with a data set of experimental measurements. A prediction criterion for the flame back instability has been formulated based on isothermal simulations without involving the combustion modelization. This analysis has been verified by a Design Of Experiments investigation performed on different burner prototype geometries. On the contrary, the formulation of a prediction criterion regarding the flame lift instability has required the use of a combustion model in the numerical code. In this analysis, the structure and aerodynamics of the flame generated by a cooking appliance has thus been characterized by experimental and numerical investigations, in which, by varying the flow inlet conditions, the flame behaviour was studied from a stable reference case toward a complete blow-out.

Clinicopathologic findings in thoroughbred horses during a high speed ��� short term competition

The aim of this study was to examine whether a real high speed-short term competition influences clinicopathological data focusing on muscle enzymes, iron profile and Acute Phase Proteins. 30 Thoroughbred racing horses (15 geldings and 15 females) aged between 4-12 years (mean 7 years), were used for the study. All the animals performed a high speed-short term competition for a total distance of 154 m in about 12 seconds, repeated 8 times, within approximately one hour (Niballo Horse Race). Blood samples were obtained 24 hours before and within 30 minutes after the end of the races. On all samples were performed a complete blood count (CBC), biochemical and haemostatic profiles. The post-race concentrations for the single parameter were corrected using an estimation of the plasma volume contraction according to the individual Alb concentration. Data were analysed with descriptive statistics and the percentage of variation from the baseline values were recorded. Pre- and post-race results were compared with non-parametric statistics (Mann Whitney U test). A difference was considered significant at p<0.05. A significant plasma volume contraction after the race was detected (Hct, Alb; p<0.01). Other relevant findings were increased concentrations of muscular enzymes (CK, LDH; p<0.01), Crt (p<0.01), significant increased uric acid (p<0.01), a significant decrease of haptoglobin (p<0.01) associated to an increase of ferritin concentrations (p<0.01), significant decrease of fibrinogen (p<0.05) accompanied by a non-significant increase of D-Dimers concentrations (p=0.08). This competition produced relevant abnormalities on clinical pathology in galloping horses. This study confirms a significant muscular damage, oxidative stress, intravascular haemolysis and subclinical hemostatic alterations. Further studies are needed to better understand the pathogenesis, the medical relevance and the impact on performance of these alterations in equine sport medicine.

Dynamic analysis of the motorcycle chattering behaviour by means of symbolic multibody modelling

Aim of this research is the development and validation of a comprehensive multibody motorcycle model featuring rigid-ring tires, taking into account both slope and roughness of road surfaces. A novel parametrization for the general kinematics of the motorcycle is proposed, using a mixed reference-point and relative-coordinates approach. The resulting description, developed in terms of dependent coordinates, makes it possible to efficiently include rigid-ring kinematics as well as road elevation and slope. The equations of motion for the multibody system are derived symbolically and the constraint equations arising from the dependent-coordinate formulation are handled using a projection technique. Therefore the resulting system of equations can be integrated in time domain using a standard ODE algorithm. The model is validated with respect to maneuvers experimentally measured on the race track, showing consistent results and excellent computational efficiency. More in detail, it is also capable of reproducing the chatter vibration of racing motorcycles. The chatter phenomenon, appearing during high speed cornering maneuvers, consists of a self-excited vertical oscillation of both the front and rear unsprung masses in the range of frequency between 17 and 22 Hz. A critical maneuver is numerically simulated, and a self-excited vibration appears, consistent with the experimentally measured chatter vibration. Finally, the driving mechanism for the self-excitation is highlighted and a physical interpretation is proposed.

Dynamics and control issues of multi-rotor platforms

This thesis deals with the analytic study of dynamics of Multi--Rotor Unmanned Aerial Vehicles. It is conceived to give a set of mathematical instruments apt to the theoretical study and design of these flying machines. The entire work is organized in analogy with classical academic texts about airplane flight dynamics. First, the non--linear equations of motion are defined and all the external actions are modeled, with particular attention to rotors aerodynamics. All the equations are provided in a form, and with personal expedients, to be directly exploitable in a simulation environment. This has requited an answer to questions like the trim of such mathematical systems. All the treatment is developed aiming at the description of different multi--rotor configurations. Then, the linearized equations of motion are derived. The computation of the stability and control derivatives of the linear model is carried out. The study of static and dynamic stability characteristics is, thus, addressed, showing the influence of the various geometric and aerodynamic parameters of the machine and in particular of the rotors. All the theoretic results are finally utilized in two interesting cases. One concerns the design of control systems for attitude stabilization. The linear model permits the tuning of linear controllers gains and the non--linear model allows the numerical testing. The other case is the study of the performances of an innovative configuration of quad--rotor aircraft. With the non--linear model the feasibility of maneuvers impossible for a traditional quad--rotor is assessed. The linear model is applied to the controllability analysis of such an aircraft in case of actuator block.