A Modal Test Technology of Impeller and Blade for Torpedo Turbine

Torpedo turbine impeller has small size, light weight and short blades, so the additional mass of a common contact acceleration sensor directly affects the measurement accuracy of impeller modal, and the sensor cannot be installed on the short blade. To completely eliminate the influence of the sensor′s additional mass and increase the measurement points and accuracy, the non-contact laser measurement technology of vibration and the PVDF piezoelectric film are introduced into the impeller modal test for improving the measurement accuracy and obtaining the first five orders of impeller natural frequency and vibration modes. Comparison between the contact and non-contact vibration measurement methods shows that: both methods achieve high measurement accuracy of impeller natural frequency, while the non-contact laser measurement technology of vibration allows more measurement points for impeller vibration modal and wider measurement range, and achieves clearer modal shape; PVDF piezoelectric film has higher measurement accuracy and anti-interference ability in higher frequency range, but it is not suitable in lower frequency range and the obtained modal shapes of the impeller are difficult to be identified.