Research Information System
Thesis Type: Doctorate
Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey
Approval Date: 2014
Student: HAMİT SOLMAZ
Supervisor: HALİT KARABULUT
Abstract:Vibrations are one of the factors that affect vehicle driving safety and comfort negatively. Principal sources of vehicle vibrations are ground roughness and engine vibrations. The vibrations occurring in the internal combustion engines are not completely eliminated because of the working principle of the engine. Despite that, vibrations can be reduced by optimizing the mass of the moving parts. In addition this, the transmission of the engine vibrations to the chassis frame can be minimized by using appropriate engine mountings. In this study, a dynamic model of a four-cylinder four-stroke diesel engine was developed and engine vibrations were investigated. The model developed has seven degrees of freedom involving three translational and three rotational movements of the engine block and the crankshaft speed fluctuations. In the model, the cylinder gas pressure forces, inertia forces of the moving parts, hydrodynamic and dry friction forces, external load torque and starter torque were taken into consideration. It was assumed that the engine block was fixed to a rigid ground with two fronts and one rear mount. To improve the reliability of the analysis, the cylinder pressure was taken from a single cylinder four stroke diesel engine experimentally. For the solution of dynamic model a method based on Taylor series was used and a simulation program was developed in FORTRAN. By using the prepared simulation program the influences of; different engine loads, the cyclic variation of the in-cylinder pressure, the connecting rods inertia forces, the combined flywheel and crankshaft inertia moment, inertia forces of pistons, inertia forces counterweights; were examined. In order to determine appropriate mount parameters, primarily optimal equivalent mount parameters were determined on each axes, then decoupling of equivalent parameters into three engine mounts was carried out by considering torque roll axis decoupling. As the result, it is proved that, the model developed can be used for determination of vibrations generated by the engine, reducing these vibrations and determining appropriate engine mounting parameters.