Bearing characteristic number is formulated as p = projected bearing pressure, z = absolute lubricant viscosity, and N = journal speed, giving________________?
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Answer: A. ZN/p
Explanation
The bearing characteristic number is a dimensionless lubrication parameter formulated as ZN over p. In this expression, Z represents absolute lubricant viscosity, N represents journal speed, and p is pressure. Combining these three variables predicts hydrodynamic lubrication film thickness in journal bearings. Journal bearings support rotating shafts using a thin fluid film of lubricating oil. Viscosity, speed, and bearing pressure dictate whether full film lubrication can be maintained. Stribeck curves use this dimensionless parameter to illustrate friction regimes in journal bearings.
Mechanical engineers use the bearing characteristic number when designing automotive crankshaft bearings. Industrial turbine bearings require careful monitoring of speed and pressure to prevent metal contact. Proper lubrication design minimizes wear and maximizes the operational lifespan of rotating machinery. Inverting the variables to p over ZN creates an incorrect ratio for predicting bearing performance. Placing viscosity in the numerator with divided pressure and speed yields incorrect dimensionless groups. Other combinations of variables fail to represent the correct physical mechanics of journal lubrication.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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