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The spatial distribution of drops in sprays is critical to the performance of many atomization systems, including diesel engine injectors, gas turbine injectors, spray coating systems, and furnace burners. This paper presents an investigation of the effects of nozzle fuel spray pattern on the measurement of cetane number as determined in the Ignition Quality Tester (IQT™). To determine the effects of spray pattern on cetane number, an optical spray pattern test rig was developed. The test rig was comprised of the IQT™ fuel injection system and data acquisition system, and the Optical Spray Pattern Analyzer from Nexum. Several nozzles from different manufacturers where chosen for this study. Cetane numbers for a diesel reference fuel were obtained for each of the test nozzles in the IQT™ and where compared qualitatively to spray pattern images for each of the test nozzles observed from the spray pattern test rig.

In this study, the injection spray of the IQT™ is characterized under atmospheric back pressure using phase doppler anemometry (PDA). Viscor calibration fluid, which has diesel-like fluid properties, is injected using the complete injection system of the IQT™. The high temporal resolution of the PDA method allowed precise time-resolved analysis of droplet size and velocity. The AMD and SMD of fuel droplets are found to be 9.3 and 29.3 μm, respectively. The velocity is analyzed as a function of radial position from the nozzle axis. The droplet velocity varies between 130 m/s and 10 m/s depending on spatial position and time after the start of injection. Average velocities on the axis were found to be approximately 78 m/s, decreasing to 15 m/s moving towards the outer spray periphery. The droplet count as a function of radial position suggests that most droplets form a cone angle of 12.6°, which is in agreement with a series of high speed images captured using front light photography.