Atomization characteristics of pressure-modulated automotive port injector sprays

Selected standard automotive port fuel injectors were retrofitted to a novel pressure-modulation piezoelectric driver to study the effect of fuel-line pressure perturbation on the spray atomization characteristics. Unlike many other piezoelectric atomizers, this unit does not drive the nozzle directly but generates a pressure perturbation inside the fuel line. It has a small size and can be installed easily between a regular gasoline port injector and the fuel line. The pressure modulator and the fuel injector are controlled separately, by different drivers; therefore, there is no extra control difficulty with this fuel system. The global spray structures were visualized using the planar laser Mie scattering (PLMS) techniques, and the spray atomization processes were quantified using phase Doppler analyzer (PDA). Four standard gasoline port injectors were tested in this study, including the central port injection (CPI), electrostatic-discharge machined (EDM) director-plate, compound silicon-micromachined (CSMM), and dual-stream (DS) injectors. The experimental results showed that the global structure of the gasoline spray is changed dramatically by this technique. In particular, this technique can greatly enhance the spray atomization process of some gasoline port injectors and is also effective in redistributing the liquid fuel spatially. The spray behavior showed a strong dependence on the driving frequency and power of the pressure modulator. The optimal operating condition for the pressure modulation device, however, depends on the injector design.