DESIGN AND NUMERICAL SIMULATING OF THE PERFORMANCE OF ACOUSTIC PLENUM CHAMBER OF THE MARINE GAS TURBINE AIR SUPPLY SYSTEM

In the present work, cross section size investigation of the plenum chamber of a marine gas turbine air supply system was done. Flow in ducts make noise and in the case of turbine inlet due to amount of ow this noise is very high and should be considered. Using numerical simulations, a method to nd a suitable design considering both the acoustic and aerodynamic performance presented. In this method, at First air supply channel system of marine gas turbine according to the requirements of the aerodynamic and acoustic were categorized into three sections; input, plenum chamber and output channels with circular cross sections. The geometric dimensions of input and output channels determined using the theory of plane waves within the channel, without considering the eects of ow also considering the limits of space inside the oat at dominant frequency. Then suitable size of the intermediate cross section of the channel in terms of both aerodynamic and acoustic requirements with regard to the eects of ow using numerical methods were studied and determined. Various 3 Dimensional turbulent ows inside chamber are considered for this work where large eddy simulation turbulence model is used. Ffowcs, Williams and Hawkings model is used for the sound propagation process based on Lighthill integral equation. Validity of the simulation is checked by comparing results (sound pressure level) against experimental data in a chamber and error is acceptable over range of studied frequencies. The results showed that channel system aerodynamic performance decreasesanditsacousticperformanceinitiallyincreases and then decreases with the increase in cross section of the plenum chamber than the cross section of the inlet / outlet channel. In addition, deviation from plane waves in considering the eects of ow is observed in channel. That is due to the eects of the current owing through Channel system and the eect of quadrupole sources in the production of sound in the channel system, which causes higher modes.