Squeeze film dampers are widely used to reduce the vibration of rotating systems. Using magnetorheological fluid in these dampers can lead to a variable-damping damper called Magnetorheological Squeeze Film Damper (MRSFD). Magnetorheological fluid viscosity alter under different values of magnetic field. The previous research have widely used long bearing approximation to derive the equations governing the hydrodynamic behavior of MRSFDs. In this paper, the behavior of MRSFDs has been studied using short bearing approximation. Next, the effects of MRSFDs on the dynamic behavior of a flexible rotor have been studied, using finite element method (FEM). Synchronous whirl motion has not been imposed on the system behavior, as an external assumption. Damper pressure distribution and forces, dynamic trajectories, eccentricity and the frequency response of the rotor are tools used to analyze the dynamic behavior of MRSFDs and rotor system. As the results show, it seems to be more precise to use short bearing approximation to analyze dampers with aspect ratios lower than a limit (especially L/D < 1). Furthermore, by controlling electrical current one can control the dynamic behavior of a rotor, to avoid failure and damage. Finally, the whirl motion of the rotor was observed to remain synchronous, even when fluid forces are present.

Along with exhaust emissions and fuel consumptions (FCs), noise emission from cars is one of the main concerns of automotive industry. Hybridization is a promising method not only to make automobiles more environmentally-friendly, but also to reduce their noise emissions. However, a proper control design for hybrid electric vehicles (HEVs) to make noise emissions lower is still required in addition to exhaust emissions and FC reductions. In this study, we modify Equivalent Consumption Minimization Strategy (ECMS) to keep the engine noise less than tire/road noise during driving. A test bench is established for calculating the engine noise and brake specific fuel consumption. Moreover, tire/road noise is experimentally defined as a function of the vehicle speed. It is shown that implementing the basic ECMS, the engine noise exceeds the tire/road noise in some moments of driving cycle, which is annoying to the passengers. Therefore, a modified ECMS is proposed to limit the candidate engine operating points such that the engine noise does not exceed the tire/road noise. It is shown that the engine noise level is kept below the tire/road noise level by using the modified ECMS at the expense of a very small increase (about 1%) in the vehicle's FC.