An ultrasonic apparatus and a method for injecting a pressurized liquid fuel by applying ultrasonic energy to a portion of the pressurized liquid fuel. The apparatus includes a die housing which defines a chamber adapted to receive a pressurized liquid and a means for applying ultrasonic energy to a portion of the pressurized liquid. The die housing further includes an inlet adapted to supply the chamber with the pressurized liquid, and an exit orifice defined by the walls of a die tip. The exit orifice is adapted to receive the pressurized liquid from the chamber and pass the liquid out of the die housing. When the means for applying ultrasonic energy is excited, it applies ultrasonic energy to the pressurized liquid without applying ultrasonic energy to the die tip. The method involves supplying a pressurized liquid to the foregoing apparatus, applying ultrasonic energy to the pressurized liquid but not the die tip while the exit orifice receives pressurized liquid from the chamber, and passing the pressurized liquid out of the exit orifice in the die tip.