Experimental and numerical studies were carried out to investigate the effects of operation parameters

such as diameter of resonance tube

resonance tube depth

jet nozzle hole to resonance tube spacing and nozzle pressure ratio(NPR)

on the flow and acoustic field characteristics of a ultrasonic atomizer based on the Hartmann resonance tube(HRT). The modifications of the geometry of HRT in spectral and flow field characteristics were studied in detail. Result shows that that

when NPR is higher than 2

the increase of NPR has little effect on the frequency

however

when NPR is lower than 2

the lower frequencies of the acoustic field are obtained. The simulation results of flow field suggest that when the length of the resonance tube is smaller than diameter of jet nozzle hole

the reciprocating phenomenon of flow in the cavity is dampened

leading to a decrease of acoustic field frequency compared with cases having longer resonance tube length

and the classical relation between acoustic field frequency and tube resonance length is not appropriate for these situations. Also

the oversized diameter of resonance tube (typically

the diameter of resonance tube more than 1.75 times the diameter of jet nozzle hole) results in a lower oscillation acoustic field frequency for the interaction of the reciprocating and the shock is weakened. Furthermore

resonance occurs when the cavity is put in the regions where pressure arises for free jet.