Title: SIMCENTER implementation of FEM/BEM methodologies as integrated simplified approaches to external gear pumps vibroacoustic analysis
A numerical-experimental integrated approach is described aimed at obtaining sufficiently accurate predictions of the noise field emitted by an external gear pump by means of some vibration measurements on its external casing. FFT acceleration spectra were experimentally acquired (PULSE code) only in some positions of a 8.5 cc/rev external gear pump casing for some working conditions and structural harmonic analyses were performed (ANSYS code) in order to estimate the dynamic response of the whole FE model. The pump noise field computation was carried out (Siemens VIRTUAL.LAB code) by considering this dynamic response as external excitation boundary condition to an FE/BE quite simplified vibroacoustic model. Sound power tests, based on sound intensity measurements, as well as sound pressure measurements in some positions around the pump casing were performed for validation purposes. The comparisons between numerical and experimental results confirmed the potentiality of this approach in offering a good compromise between noise prediction accuracy and reduction of experimental and modelling requirements.
Starting from the same pump FE and BE models and FFT acceleration spectra and taking into account updating and implementation of SIMCENTER, some further developments have been carried out:
1. Pump operational deflection shapes (ODS) were experimentally measured for the same pump working conditions (SIMCENTER TEST.LAB and SIMCENTER SCADAS) and the Modal Participation Factors (MPS) estimated by means of the Modal Expansion method (Siemens/LMS VIRTUAL.LAB code, this tool not implemented in SIMCENTER at present), this way ‘expanding’ vibration response onto the full FE model;
2. Pump noise field computation was carried out by means of acoustic transfer vectors (ATV) and/or BEM, starting from pump mode shapes acquired/computed and pump structural harmonic analyses carried out by NX NASTRAN (SIMCENTER).
Advantages of these new approaches have been evaluated and compared, as computation time reduction and SIMCENTER efficiency/performance evaluation.