This content is not included in your SAE MOBILUS subscription, or you are not logged in.
High-Speed Microscopic Imaging of the Initial Stage of Diesel Spray Formation and Primary Breakup
ISSN: 0148-7191, e-ISSN: 2688-3627
Published October 25, 2010 by SAE International in United States
Annotation ability available
The formation and breakup of diesel sprays was investigated experimentally on a common rail diesel injector using a long range microscope. The objectives were to further the fundamental understanding of the processes involved in the initial stage of diesel spray formation.
Tests were conducted at atmospheric conditions and on a rapid compression machine with motored in-cylinder peak pressures up to 8 MPa, and injection pressures up to 160 MPa. The light source and long range imaging optics were optimized to produce blur-free shadowgraphic images of sprays with a resolution of 0.6 μm per pixel, and a viewing region of 768x614 μm. Such fine spatial and temporal resolutions allowed the observation of previously unreported shearing instabilities and stagnation point on the tip of diesel jets. The tip of the fuel jet was seen to take the shape of an oblate spheroidal cap immediately after leaving the nozzle, due to the combination of transverse expansion of the jet and the physical properties of the fuel. The spheroidal cap was found to consist of residual fuel trapped in the injector hole after the end of the injection process. The formation of fuel ligaments close to the orifice was also observed, ligaments which were subsequently seen to breakup into droplets through hydrodynamic and capillary instabilities.
An ultra-high-speed camera was then used to capture the dynamics of the early spray formation and primary breakup with fine temporal and spatial resolutions. The frame rate was up to 5 million images per second and exposure time down to 20 ns, with a fixed resolution of 1280x960 pixels covering a viewing region of 995x746 μm. A vortex ring motion within the vaporized spheroidal cap was identified, and resulted in a slipstream effect which led to a central ligament being propelled ahead of the liquid jet.
CitationCrua, C., Shoba, T., Heikal, M., Gold, M. et al., "High-Speed Microscopic Imaging of the Initial Stage of Diesel Spray Formation and Primary Breakup," SAE Technical Paper 2010-01-2247, 2010, https://doi.org/10.4271/2010-01-2247.
- Som, S. and Aggarwal, S.K., “Effects of Primary Breakup Modeling on Spray and Combustion Characteristics of Compression Ignition Engines,” Combustion and Flame 157(6):1179-1193, 2010, doi:10.1016/j.combustflame.2010.02.018.
- Dumouchel, C., “On the Experimental Investigation on Primary Atomization of Liquid Streams,” Experiments in Fluids 45(3):371-422, 2008, doi:10.1007/s00348-008-0526-0.
- Eggers, J. and Villermaux, E., “Physics of Liquid Jets,” Reports on progress in physics 71(3):036601, 2008, doi:10.1088/0034-4885/71/3/036601.
- Faeth, G., Hsiang, L. and Wu, P., “Structure and Breakup Properties of Sprays,” International Journal of Multiphase Flow 21(supp 1):99-127, 1995, doi:10.1016/0301-9322(95)00059-7.
- Gorokhovski, M. and Herrmann, M., “Modeling Primary Atomization,” Annual Review of Fluid Mechanics 40(1):343-366, 2008, doi:10.1146/annurev.fluid.40.111406.102200.
- Heimgärtner, C. and Leipertz, A., “Investigation of Primary Diesel Spray Breakup Close to the Nozzle of a Common Rail High Pressure Injection System,” presented at 8th ICLASS, Pasadena, USA, July 2000.
- Hossainpour, S. and Binesh, A., “Investigation of Fuel Spray Atomization in a Di Heavy-Duty Diesel Engine and Comparison of Various Spray Breakup Models,” Fuel 88(5):799-805, 2009, doi:10.1016/j.fuel.2008.10.036.
- Lefebvre, A.H., Atomization and sprays, Hemisphere Publishing, New York, 1989.
- Liu, Z., Im, K., Xie, X., Wang, Y., Zhang, X., Moon, S., Gao, J., Fezzaa, K., Lai, M. and Harkay, K., “Ultra-Fast Phase-Contrast X-Ray Imaging of near-Nozzle Velocity Field of High-Speed Diesel Fuel Sprays,” presented at ILASS-Americas, Cincinnati, Ohio, USA, May 2010.
- Reitz, R. and Diwakar, R., “Structure of High-Pressure Fuel Sprays,” SAE Technical Paper 870598, 1987, doi:10.4271/870598.
- Crua, C., “Combustion Processes in a Diesel Engine,” Ph.D. thesis, University of Brighton, UK, 2002.
- Karimi, K., “Characterisation of Multiple-Injection Diesel Sprays at Elevated Pressures and Temperatures,” Ph.D. thesis, University of Brighton, UK, 2007.
- Bae, C., Yu, J., Kang, J., Kong, J. and Lee, K., “Effect of Nozzle Geometry on the Common-Rail Diesel Spray,” SAE Technical Paper 2002-01-1625, 2002, doi:10.4271/2002-01-1625.
- Lai, M., Wang, T., Xie, X., Han, J., Henein, N., Schwarz, E. and Bryzik, W., “Microscopic Characterization of Diesel Sprays at VCO Nozzle Exit,” SAE Technical Paper 982542, 1998, doi:10.4281/982542.
- Sjöberg, H., Manneberg, G. and Cronhjort, A., “Long-Working-Distance Microscope Used for Diesel Injection Spray Imaging,” Optical Engineering 35(12):3591-3596, 1996, doi:10.1117/1.601113.
- Badock, C., Wirth, R., Fath, A. and Leipertz, A., “Investigation of Cavitation in Real Size Diesel Injection Nozzles,” International Journal of Heat and Fluid Flow 20(5):538-544, 1999, doi:10.1016/S0142-727X(99)00043-0.
- Roisman, I. V., Araneo, L. and Tropea, C., “Effect of Ambient Pressure on Penetration of a Diesel Spray,” International Journal of Multiphase Flow 33(8):904-920, 2007, doi:10.1016/j.ijmultiphaseflow.2007.01.004.
- Hiroyasu, H. and Arai, M., “Structure of Fuel Sprays in Diesel Engines,” SAE Technical Paper 900475, 1990, doi:10.4271/900475.
- Naber, J. D. and Siebers, D. L., “Effects of Gas Density and Vaporization on Penetration and Dispersion of Diesel Sprays,” SAE Technical Paper 960034, 1996, doi:10.4271/960034.
- Lepperhoff, G. and Houben, M., “Mechanisms of Deposit Formation in Internal Combustion Engines and Heat Exchangers,” SAE Technical Paper 931032, 1993, doi:10.4271/931032.
- Birgel, A., Ladommatos, N., Aleiferis, P., Zuelch, S., Milovanovic, N., Lafon, V., Orlovic, A., Lacey, P. and Richards, P., “Deposit Formation in the Holes of Diesel Injector Nozzles: A Critical Review,” SAE Technical Paper 2008-01-2383, 2008, doi:10.4271/2008-01-2383.