No abstract

The. zinbalrince response and stability of a si'rnple flexible rotor ruas tested over n speed range with three dzfferent types of journal bearings: rixial groove, press~i.re dam and tilting pad. measurements ruere rnade of total rotor rest~onse, synchronous response and f r e q~i e r~c~ S~C C I I~L~I W . r~t various runni.r~g spee(ls and at selected locatiorrs rtlorrg the shaft. Axinl groove bearings ruere better for lorusficed u.se and rlear the critical speed but oil whip occz~rred at npprosirrrcitely twice the first rotor critical speed. Truo sets of pressure riarrr bearirrgs with different geometries were tested and both controlleti vibrritio~rs at the critical speed. Whip occurred at twice and thrice the oitical speed for the truo presszirc darn bearings. Kltingprtrl beatings exhibiteri lrirgc vibrntio?~ c~,rnplitudes near the criticnl sfleecl, but dirl ,101 go into oil ruhip (it speerls u p to three times the first rotor critict~l speed.

Theoretically predicted instability onset speeds are compared to the experimental instability threshold speeds for a simple three mass flexible rotor supported by five geometrically different sets of step journal bearings and a set of two axial groove bearings. The near optimum step bearing designs increase the instability onset speed by around 109 percent in one case and 41 percent in another compared to two axial groove bearings. The off optimum designs increase the instability speed by 18, 30 and 35 percent. The theoretical stability analysis predicts the general trends in the experimental data.

No abstract

The response of a flexible rotor mounted in six bearing sets has been experimentally determined. One set of axial groove bearings and five sets of pressure dam bearings were tested. Conventional synchronous tracking was used in the analysis and other techniques utilizing an FFT analyzer were developed. The stability of the system was seen to strongly depend on the design of the step bearings. The dam bearings were also noted to lock into subsynchronous whip during deceleration after the system went unstable. The response of the system with varying degrees of unbalance is also analyzed and several structural resonances of the rotor system are discussed.