• Tribology and Lubricants
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• 제12권3호
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• pp.92-99
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• 1996

Energy-efficient contrarotating propeller systems have been recently reviewed as one of alternative means in marine car-carrier applications. Contrarotating rotors preclude the usage of conventional plain journal bearings due to the lack of load carrying capacity. A new multi-recess hydrostatic contrarotating journal beating test facility has been designed and installed to test the static load carrying capacity. Measurements of flow rates and orbits have been investigated by testings on a overhung-type contrarotating rotor system which is supported by a hydrostatic journal bearing. Numerical results of static equilibria were compared with test results. Various contrarotating speed combinations, and supply pressure conditions were selected. The numerical predictions of orbit centers and flow rates are generally accurate.

• Journal of Hydrospace Technology
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• 제1권1호
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• pp.29-40
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• 1995

This paper describes the procedure to predict steady and unsteady performances of a contrarotating propeller(CRP) by a mixed formulation of the boundary value problem(BVP) far the flow around a CRP. The blade BVP is treated by a classical vortex lattice method, whereas the hub BVP is solved by a potential-based panel method. Blades and trailing wakes are represented by a vortex and/or source lattice system, and hubs are represented by normal dipole and source distributions. Both forward and aft propellers are solved simultaneously, thus treating the interaction effect without iteration. The unsteady performance is computed directly in time domain. The new numerical procedure requires a large amount of storage and computing time, which is however no longer a limit in a modern computer system. Sample computations show that the steady performance compares very well with the experiments. The predicted unsteady behavior shows that the dominant harmonics of the total forces are multiples of not only the number of blades of the forward and aft propellers but also the product of both blade numbers. The magnitude of the latter harmonics, present also in uniform oncoming flow, may reach abort 50% of the mean torque for the aft propeller, which in turn may cause a serious vibration problem in the complicated contrarotating shafting system.