High performance turbo machinery demands high shaft speeds, increased rotor flexibility, tighter clearances in flow passages, advanced materials, and increased tolerance to imbalances. Operation at high speeds induces severe dynamic loading with large amplitude journal motions at the bearing supports. Squeeze film dampers are essential components of high-speed turbo machinery since they offer the unique advantages of dissipation of vibration energy and isolation of structural components, as well as the capability to improve the dynamic stability characteristics of inherently unstable rotor-bearing systems. A bearing test rig is developed using 350 KW motor with variable frequency drive and has the potential of maximum operating speed up to 20,000 rpm. A squeeze film damper is used between the bearings and housing to reduce the unbalance forces transmitted to the pedestal by introducing an additional damping and thereby reduces the amplitude of vibration to acceptable level. The test rig instrumentation is capable of detecting bearing critical speed of the test rotor, and has been used for parametric studies and to monitor the temperature profile, vibration levels and pressure distribution of SFD oil film. The first critical speed of the test rotor is measured. The vibration level of the rotor system is increased with the rise of axial load together with speed. It is estimated that under all the conditions presence of oil in SFD zone reduces the vibration levels.

In the present paper, we have derived an expression for change in entropy of non-spinning black holes on the basis of formula ( BH

This article elucidates the calibration of newly procured spinning rotor gauge (SRG 3) from MKS Instruments, USA using primary vacuum standards: Orifice flow system (OFS) and Static expansion system (SES) established at National Physical Laboratory, India (NPLI) in the range of 10^-4 Pa to 1 Pa and further compared with manufacturer reported value which was calibrated by transfer standard of National Institute of Standards & Technology (NIST). The key parameters to calculate the pressure measured by SRG is the accommodation coefficients. The accommodation coefficients for N₂ gas obtained using OFS, SES, and calibration report form NIST USA (SRG2) are 0.957, 0.961, and 0.954 respectively.

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