A high-pressure fuel injector has been designed to produce a spray having a lower SMD than that obtained typically with a common-rail fuel injection system for the same injection pressure. In the present design, a mixture of fuel and dissolved gas (CO2 or N2) is introduced continuously to an injector unit. The downstream part of the injector consists of an inlet orifice, an expansion chamber, a swirl duct, and a discharge orifice. When the mixture enters the expansion chamber, a part of the dissolved gas is transformed into tiny bubbles that grow inside the expansion chamber. When the mixture is discharged through the discharge orifice, these bubbles undergo a rapid flashing process while the liquid bulk disintegrates into small droplets. In the present work, we investigate experimentally the effect of the design parameters (geometrical proportions and injection pressure) on the SMD and cone angle of a continuous spray. The SMD was measured with a laser particle size analyzer (Malvern X-Mastersizer). A high-speed digital camera was employed to trace the liquid disintegration process. An overall analysis has been performed to evaluate the advantage of the proposed method over its counterparts, in terms of the total energy required to produce the desired spray.