| A parametric study of the thermal effects in half-circumferential grooved journal bearings under aligned and misaligned conditions has been carried out by solving numerically the coupled Reynolds and energy equations. Five different sets of boundary conditions for the energy equation have been used which include mixing between recirculating oil and inlet oil and a contraction ratio for the cavitation region. The effects of the wall temperature, of inlet pressure and of the L/D ratio have also been examined. For the ranges of parameters found in internal combustion engines, the mixing effectiveness at the groove and the resulting final mixture temperature as well as the wall temperature and heat transfer rates have been found to be of importance in bearing operations. Realistic inlet pressure increases on the other hand, have been found incapable of affecting significantly the bearing performance. When the journal is misaligned, the variability of the temperature has been shown to smooth out the peaks of both pressure increase and friction caused by misalignment and thus reduce its performance deterioration.; Further, turbulence on the journal bearing operation is examined and the thermal variability is studied for isothermal, convective and adiabatic conditions on the walls. Heat convection is found to play but a small role in determining friction and load. The friction distribution patterns though inside a journal bearing now appear different with high values at the front part of the bearing due to the high speed and low temperature, and a sudden decrease past the pressure maximum.; To examine the unsteady effects of load and shaft speed, a full-circumferential grooved journal bearing under variable load has been analyzed. For this bearing, a series of measurements of shaft speed has just been completed; these data provided the basis for comparison of the numerical results. Thermal effects were not considered because of the short testing time. For this computation, the unsteady Reynolds equation is solved numerically in conjunction with the mobility method and Goenka's map components. The numerical results agree well with the data. |
