Przedziały adekwatności liniowych i nieliniowych metod określania właściwości dynamicznych maszyn wirnikowych [Adequacy ranges of linear and nonlinear methods for determining the dynamic properties of the rotating machinery]
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- Streszczenie:
- The PhD dissertation focuses on the experimental and computational determination of stiffness and damping coefficients for hydrodynamic bearings. Its principal aim is to develop the existing experimental method for identification of bearing dynamic coefficients and to specify the applicability ranges of various computational methods on the basis of measurements taken for a fluid-flow machine equipped with bearings characterized by the inherently nonlinear nature of their operation.
The experimental research was carried out, using the impact excitation technique
on the basis of which the dynamic parameters of the hydrodynamic bearings have been identified. The linear computational method used, in addition to allowing you to determine stiffness and damping coefficients, the method also allows you to identify mass coefficients, and all of this takes place in one computational step. Stiffness and damping coefficients cannot be determined directly, which is why indirect methods are applied. The rotor mass is a directly measurable parameter. The indirectly calculated mass coefficients can be compared with known rotor mass and in this way the correctness of the obtained results can be initially estimated.
Within the framework of this PhD dissertation the sensitivity analysis of the
above-mentioned experimental method was conducted using the model created in the Samcef Rotors software. It was analyzed whether the factors such as rotor unbalance, change of the position of measurement sensors, change of the excitation force parameters etc. have an impact on the obtained results. The experimental research was carried out to determine the dynamic coefficients of the hydrodynamic bearings across a wide range of rotational speeds, taking into account rotor resonant speeds and speeds above the resonant range. The obtained results were subsequently verified using the Abaqus software.
The calculations of stiffness and damping coefficients for hydrodynamic bearings
were also carried out using linear and nonlinear computational models, developed at the IFFM PAS. The verification of the obtained results was performed. The similarities and differences between the bearing coefficients obtained by the computational methods (linear and nonlinear) and by the experimental method have been discussed.
- Rok:
- 2016
- Typ publikacji:
- Rozprawa doktorska
- Uniwersytet:
- The Szewalski Institute of Fluid Flow Machinery PAN
- Typ publikacji:
- Doctoral thesis