Investigation of the Characteristics of a High Pressure Injector

This paper will focus on the spray characteristics of a high pressure (up to 155 MPa) accumulator type injector in a high pressure (chosen density) quiescent spray chamber. The injector uses a standard single orifice nozzle which produces a full cone spray. Using this apparatus, we are examining the fundamental aspects of high pressure spray formation under controlled conditions. Experimental data was collected using high speed photography (10,000 frames per second) which used a pulsed copper-vapor laser as a light source. Two photographic techniques are being utilized. Direct attenuation allows measurement of tip penetration, spray cone angle, and injection duration. Scattering from a sheet of laser light perpendicular to the camera field of view is being developed in an attempt to resolve inner spray cone structure. In addition to the quantitative data from the high speed photography, injector accumulator pressure, supply pressure and injection rate histories were recorded. From this data, instantaneous nozzle discharge coefficients were calculated. Results will be reported for changes in injector hole diameter (.300 and .406 mm), peak accumulator pressure (105, 123 and 140 MPa), and injection frequency (12.5 and 22 Hz). From our data, the BKM high pressure injector produces a very fast initial rate of injection which slowly decays throughout the injection duration and then ends with a sharp cut-off. Also, for a given injector and nozzle, tip penetration is independent of injection frequency as peak accumulator pressure determines all injection characteristics.