|Tipo di tesi||Tesi di laurea magistrale|
|Titolo||Trasmissione Idrostatica per veicoli off-road:sperimentazione e modellizzazione.|
|Titolo in inglese||Hydrostatic Transmission for off-road vehicles:investigation and modeling.|
|Struttura||Dipartimento di Ingegneria "Enzo Ferrari"|
|Corso di studi||Ingegneria Meccanica (D.M.270/04)|
|Data inizio appello||2017-04-12|
|Disponibilità||Accesso limitato: si può decidere quali file della tesi rendere accessibili. Disponibilità mixed (scegli questa opzione se vuoi rendere inaccessibili tutti i file della tesi o parte di essi)|
|Data di rilascio||2057-04-12|
La legislazione sempre più restrittiva sulle emissioni dei motori a combustione interna e l'aumento del costo del petrolio, induce i progettisti ad aumentare quanto più possibile l'efficienza globale dei veicoli che non operano su strada. In questo elaborato viene eseguita l’analisi di una trasmissione idrostatica a circuito chiuso, come trasmissione di potenza tra il motore primo (motore diesel) e l’utilizzatore (carico) entrambi sottosistemi dell’applicazione, ossia un veicolo di movimentazione terra. Questa analisi è stata effettuata presso il centro di ricerca dell’ Université de Technologie de Compiègne come attività progettuale. La disponibilità di un banco prova ha consentito di eseguire simulazioni fisiche in tempo reale sulla trasmissione stessa.
Emissions laws, which are becoming more restrictive, and oil price trend are pushing internal combustion engines designers, to increase as much as possible the efficiency of off-road vehicles. In this paper an analysis based on a master project led at Centre de Research of Université de Technologie de Compiègne, of a closed loop hydrostatic transmission was carried out. A test bench was available to perform experimental tests of that type of power transmission between prime mover (diesel engine) and vehicle (load) employed as construction machinery. Particularly, the work consists of three steps related to the hydrostatic transmission: full investigation, software modeling for simulation and empirical losses prediction. This dissertation first aims at find out the optimal operating range of thermal engine according to efficiency of the hydrostatic transmission which is a variable depending on working parameters as speed and displacement. The research refers before at the background of the hydrostatic transmission so test rig with its input and output, diesel engine and load. Then the analysis focuses on individual components that make up the hydrostatic transmission. In order to bring out conclusions on the global system mode operating each machine test was necessary. Efficiency tests executed for machines involve hydraulic pump and motor, specifying set up, modus operandi and finally results. Optimal operating mode of hydrostatic transmission and its parameters were suggested by results. To save diesel engine consumption and emission, it is a good deal working between 800 and 1500 revolution per minute of shaft speed. In case of high speed ratio of hydrostatic transmission be demanded to achieve target on vehicle velocity it is necessary get a greater pump size. Best trade-off is achieved between cost of new pump with required displacement, and reduction of diesel engine consumption and emission. As second step deals with a model development via AmeSim of engine, hydrostatic transmission and vehicle. The model built, accurately reproduces the reality and allows modifying parameters of subsystems in rapid and effective way. Efficiency curves discovered by the first step, are used into the model for having a valid tool and closer to the real time simulation. Before to perform tests on test bench, it is more appropriate using the model to predict the system response affected by operating parameters. A further step in this research could be an investigation to find out what happens when pump works as motor and vice versa. It could include other cases concerning different work configurations for vehicle. The thesis ends with a statistical analysis to identify flow and torque losses models. An empirical formulation has been found and calibrated to explain pump flow losses involved in the hydrostatic transmission. To compare measured and empirical data in terms of volumetric efficiency, a linear regression is used. According to statistic results it is shown that empirical model describes the reality with a good accuracy.