Acoustic and imaging correlations of a GDI single-hole spray

Acoustic emission is a powerful tool for monitoring different problems related to resonance phenomena. In this paper, a preliminary investigation of an alternative technology, having the potential to yield additional data about the atomization phenomenon of a spray for i.c. engines, is presented being low cost, less intrusive and much more robust respect to optical ones, both in terms of care requirements in setting the equipment and its own resilience to damages. A single-hole, axially-disposed, 0.200 mm diameter GDI injector was used to spray com-mercial gasoline in a test chamber at room temperature and atmospheric backpressure. The explored injection pressure was 5.0 MPa. Cycle-resolved acquisitions of the spray evolution were acquired by a high-speed camera. Simultaneously to the imaging measurements, an acoustic investigation was performed by using microphones and proper loudspeaker devices to assess the acoustic emission under investigated conditions. The above technique provided useful information on the fuel injection characteristic using Acoustic Emission (AE) to highlight the resonance frequencies established and their relationship with the microphone probe locations in the spray and the atomization degree. A series of experiments was designed to measure the sound pressure signal produced during the injection process. The main parameter carried out were: the noise generation mechanism, peak sound pressure amplitudes and bubble size determination by frequency