Experimental Study of Three Journal Bearings with a Flexible Rotor

The unbalance response and stability of a simple flexible rotor was tested over a speed range with three different types of journal bearings: axial groove, pressure dam and tilting pad. Measurements were made of total rotor response, synchronous response and frequency spectrums at various running speeds and at selected locations along the shaft. Axial groove bearings were better for low-speed use and near the critical speed but oil whip occurred at approximately twice the first rotor critical speed. Two sets of pressure dam bearings with different geometries were tested and both controlled vibrations at the critical speed. Whip occurred at twice and thrice the critical speed for the two pressure dam bearings. Tilting-pad beatings exhibited large vibration amplitudes near the critical speed, but did not go into oil whip at speeds up to three times the first rotor critical speed.