Determination of loose spline coupling coefficients of rotor bearing systems in turbomachinery /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Analytical and experimental studies have been carried out to determine the stiffness and damping coefficients of loose spline couplings used in high speed rotating machinery from which a realistic assessment of rotor stability can be made at the turbomachinery design stage. This is believed to be the first attempt ever to determine these coefficients experimentally. Experimented modal parameters of the rotor bearing system with a spline coupling are found using modal testing for given spline geometry, misalignment, lubrication conditions, torque, and rotational speeds. A dual rotor computer algorithm which contains a spline coupling model is developed in order to calculate the analytical modal parameters. Support bearing coefficients are obtained using a pressure dam bearing computer code which employs lubrication theory. Spline coupling coefficients are determined by adjusting the model until the analytical m odal parameters match the experimental modal parameters. Both computer simulations and impact testing show that shaft speed and torque are the most important parameters which affect the system natural frequency and logarithmic decrement. However, the modal parameters are not very sensitive to the spline coupling coefficients. Only the second natural frequency shows any sensitivity to the spline angular stiffness. The lateral stiffness coefficient of the spline coupling decreases as rotational speed increases. Lateral and angular damping do not influence the modal parameters until unreasonably large values are considered. This is due to the large value of dam ping in the pressure dam bearings. Since the modal parameters are insensitive to the spline coefficients, a set of error bounds for the experimental values are chosen to determine the ranges of the loose spline coupling coefficients. The results show that the value of the spline lateral stiffness is between 2.0x10^7 and 8.0x10^8 N /m, and the spline angular stiffness is between 2.0x10^7 and 10^6 Nm/rad. However, it is impossible to identify the spline damping coefficients because the effect of support bearing dam ping is dominant. Large values of the support bearing dam ping coefficients suppress the nonsynchronous whirling motion due to the spline friction even at speeds above the first critical speed. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Mechanical Engineering." |
| Physical Description: | xv, 233 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |