Comparison of JP-8 Sprays from a Hydraulically Actuated Electronically Controlled Unit Injector and a Common Rail Injector

Report No. ARL-RP-0556
Authors: Matthew Kurma; Michael Tess; Luis Bravo; Chol-Bum Kweon; Craig Hershey
Date/Pages: October 2015; 22 pages
Abstract: JP-8 sprays from a hydraulically actuated electronically controlled unit injector (HEUI) and a common rail injector (CRIN) were investigated to compare the effects of the fuel delivery system on the spray behavior of the fuel. The fuel pressurization method between injectors is fundamentally different. The HEUI system utilizes engine oil to pressurize the fuel, whereas, the CRIN system pressurizes the fuel directly. To explore the different injection methods, rate of injection (ROI) experiments were initially conducted to measure shot-to-shot fuel quantity and rate of injection of both injector types. During the ROI experiments with the HEUI, the oil temperature and pressure was varied from 45°C to 90°C and 142-200 bar, respectively. In addition, the dwell time and rate shape of the HEUI was investigated to determine effects on injected fuel mass and rate of injection. Non-reacting spray experiments were performed in a high temperature (900 K), high pressure (60 bar) flow chamber to investigate the transient liquid penetration lengths of both injection systems. Ambient conditions of the flow chamber were chosen to represent typical conditions found in a compression-ignition engine and fuel injection pressures were 850, 1000, and 1200 bar. Results showed that an increase in oil temperature for the HEUI will increase the injected fuel mass. The CRIN injector system showed 4 times more precise control of injected fuel mass compared to the HEUI, and the CRIN showed less variations in the hydraulic delay. Comparing the plume to plume transient spray behavior of the two systems showed that more variations were present with the HEUI injector. However, the overall transient liquid penetration behavior was similar for both injection systems. Results of this study can be used to optimize the design of engines using JP-8 with hydraulic fuel injectors, thus improving fuel efficiency and power output.
Distribution: Approved for public release
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Last Update / Reviewed: October 1, 2015