Browsing by Subject "windage losses"
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Design and testing of a high-speed spin test for evaluating pulse alternator windage loss effects(IEEE, 2003-01) Werst, M.D.; Hahne, J.J.; Liu, H-P.; Penney, C.E.Advanced pulse alternator designs require rotor surface speeds in excess of 1000 m/s. High tip speeds and an operating environment consisting of partial vacuum result in frictional windage losses and subsequent heating of the rotor and stator surfaces. Analytical models for cylindrical rotor windage loss exist. However, solving the combined fluid dynamics and thermal conduction problem for this specific operating regime requires significant code development. A series of spin tests with incremental levels of complexity have been designed and tested and are presented in this paper. The tests are intended to validate windage loss and heating codes used in the pulse alternator rotor design.Item Measurement of Windage Losses and Temperature Distribution for a High Speed Composite Rotor in a Stator Assembly at Low Air Pressures(American Society of Mechanical Engineers, 2003-07) Hahne, J.J.; Werst, M.D.; Penney, C.E.; Liu, H-P.; O’Rarden, J.; Bogard, D.With the advancements in composite technology several innovative applications present themselves that involve high-speed composite rotors spinning in a stator assembly. As rotational speeds and rotor tip speeds increase, these rotors must operate in low air pressure environments to minimize windage losses and thermal effects of being at high speed for long durations. Accurately predicting this windage loss for a specific geometry and operating conditions is very important for a proper design. It is also very important to know the relative heat distribution that is seen by the rotor and stator from this windage loss. Analysis tools to date do not have a coupled link that calculates windage loss and a resultant thermal distribution to the rotor and stator surfaces. This paper presents the design and fabrication of a test setup to measure the total windage loss and temperature distribution from a high-speed composite rotor in a stator structure. Rotor speeds up to 40,000 rpm and rotor tip speeds up to 900 m/s with pressure ranges from 0.1 torr to 10 torr were operating parameters during the testing. The paper will also present experimental data obtained during the testing. Experimental data obtained during the testing will be used to evaluate new analysis methods for predicting the windage loss and thermal distribution in new high-speed rotor applications.Item Prediction of Windage losses of an Enclosed High Speed Composite Rotor in Low Air Pressure Environments(American Society of Mechanical Engineers, 2003-07) Liu, H-P.; Werst, M.D.; Hahne, J.J.; Bogard, D.The frictional windage losses associated with non-ventilated airflows in the air gaps between the rotor and stator of a high speed rotating machine can greatly influence the rotor outer and stator inner surface temperatures. The characteristics of the radial and axial air-gap flows have been of general interest in many engineering applications. A rotating air gap flow is very complex, and in general, can be categorized as a continuum flow, slip flow, and free molecule flow, depending on the ratio of its mean free path to the air gap dimension. For a continuum flow between concentric rotating cylinders, secondary flow of rows of circumferential Taylor vortices in the air gap due to centrifugal flow instability of a curved flow at relatively high rotating speeds will typically be formed. As the air pressure in the air gap drops significantly, rarefied gas flow, departure from continuum flow, occurs when the mean free path becomes relatively large compared to the air gap dimension. This paper has developed and summarized an analytical approach to predict high speed windage losses (rotor tip velocities up to 900 m/s) at low rotor cavity air pressures (0.1 torr to 10 torr). The predicted transient windage losses at various air pressures and high rotor speeds are compared with measured windage losses generated in continuum and slip flow regimes. The agreements between the predicted and measured windage losses are relatively well.