Turbomachinery

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Rotor vibration of the liquid rocket turbopump may cause not only the functional failures but also catastrophic failures of the rocket engine that leads to the mission failure. It is generally considered that the rotor vibration characteristics depend on the length of the overhang part of the rotor, bearing support stiffness, bearing span and system damping. This study aims at proposing the morphological design method of the turbopump for considering the rotor dynamic properties. In the first, a typical turbopump rotor linear dynamic simulation model was constructed by using finite element method. Its vibration characteristics were validated by the published data. In the second, component based modeling for the morphological design was proposed. Available different component arrangements were generated based on the selection rules. Each arrangement estimated from the view point of the rotor weight and its critical speed. Illustrative design simulation performed for a trial turbopump design example.

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In the present paper the attention is focused on the characteristics of Karman vortex shedding from the trailing edge of the rotor blade at the design operating attack angle for different Reynolds number. We measured the local relative velocity, velocity fluctuation, and spectrum in the near wake of rotor blade. The periodic velocity fluctuation in the near wake of the blade was observed at Reynolds number, based on the tip chord length, of 5.1×10⁴. This was caused by Karman vortex shedding from the trailing edge of the blade at constant frequency along spanwise direction. However, as Reynolds number increased, the spectrum of velocity fluctuation became broad band gradually. At the design operating point, the velocity fluctuation at predicted vortex shedding frequency was also observed in the near wake of the rotor blade momentarily although the intensity and the periodicity of velocity fluctuations became weak.

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