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 characterist ics. Unlike many other piezoelectric atomizers, this unit does not dri ve the nozzle directly but generates a pressure perturbation inside th e fuel line. It has a small size and can be installed easily between a regular gasoline port injector and the fuel line. The pressure modula tor and the fuel injector are controlled separately, by different driv ers; therefore, there is no extra control difficulty with this fuel sy stem. The global spray structures were visualized using the planar las er Mie scattering (PLMS) techniques, and the spray atomization process es were quantified using phase Doppler analyzer (PDA). Four standard g asoline port injectors were tested in this study, including the centra l port injection (CPI), electrostatic-discharge machined (EDM) directo r-plate, compound silicon-micromachined (CSMM), and dual-stream (DS) i njectors. The experimental results showed that the global structure of the gasoline spray is changed dramatically by this technique. In part icular, this technique can greatly enhance the spray atomization proce ss of some gasoline port injectors and is also effective in redistribu ting the liquid fuel spatially. The spray behavior showed a strong dep endence on the driving frequency and power of the pressure modulator. The optimal operating condition for the pressure modulation device, ho wever, depends on the injector design.