Ultrasonic Atomization Using a Micro Nozzle Array

Atomization characteristics of an ultrasonic fuel injector using a micro nozzle array were investigated experimentally. Micro nozzles whose exit diameter is d =3,6 and 9mum are mounted on a thin metal film. The number of the micro nozzle is 2.0 x 104. Using an ultrasonic oscillator, gasoline is periodically pushed out from the micro nozzles at the frequency of 63.6 kHz. A disk-type PZT is used as an ultrasonic oscillator, and the oscillation is amplified using a step-type horn. The input voltage is varied from 0 to 200 V. At the natural frequency, the oscillation amplitude of the horn is about 10 p.m. The droplet diameter and velocity are measured with a phase Doppler analyzer at 15 mm downstream from the micro nozzle array. For d=3 mum, the Sauter mean diameter (SMD) is about 10 p.m, and the fuel flow rate is 0.023 cc/s. The SMD is much smaller when compared to conventional port fuel injectors. For d=6 the SMD is about 10 to 18 p.m, and the fuel flow rate is 0.055 cc/s. For d =9 p.m, the SMD is about 16 to 28 1.1.m, and the fuel flow rate is 0.41 cc/s. It is shown that, using the micro nozzle array, a uniform-diameter steady spray can be obtained without high-pressure fuel pump and nozzle type injectors.