Optical Diagnostics of Late-Injection Low-Temperature Combustion in a Heavy-Duty Diesel Engine

A late injection, high exhaust-gas recirculation (EGR)-rate, low-temperature combustion strategy was investigated in a heavy-duty diesel engine using a suite of optical diagnostics: chemiluminescence for visualization of ignition and combustion, laser Mie scattering for liquid fuel imaging, planar laser-induced fluorescence (PLIF) for both OH and vapor-fuel imaging, and laser-induced incandescence (LII) for soot imaging. Fuel is injected at top dead center when the in-cylinder gases are hot and dense. Consequently, the maximum liquid fuel penetration is 27 mm, which is short enough to avoid wall impingement. The cool flame starts 4.5 crank angle degrees (CAD) after the start of injection (ASI), midway between the injector and bowl-rim, and likely helps fuel to vaporize. Within a few CAD, the cool-flame combustion reaches the bowl-rim. A large premixed combustion occurs near 9 CAD ASI, close to the bowl rim. Soot is visible shortly afterwards along the walls, typically between two adjacent jets at the head vortex location. OH PLIF indicates that premixed combustion first occurs within the jet and then spreads along the bowl rim in a thin layer, surrounding soot pockets at the start of the mixing-controlled combustion phase near 17 CAD ASI. During the mixing-controlled phase, soot is not fully oxidized and is still present near the bowl-rim late in the cycle. At the end of combustion near 27 CAD ASI, averaged PLIF images indicate two separate zones. OH PLIF appears near the bowl rim, while broadband PLIF persists late in the cycle near the injector. The most likely source of broadband PLIF is unburned fuel, which indicates that the near-injector region is a potential source of unburned hydrocarbons.

[1]  Long Zhang,et al.  A Study of Unburnt Hydrocarbon Emission in Small DI Diesel Engines , 1999 .

[2]  Christoph Espey,et al.  Soot and Fuel Distributions in a D.I. Diesel Engine via 2-D Imaging , 1992 .

[3]  Jerald A. Caton,et al.  Evaluation of the equivalence ratio-temperature region of diesel soot precursor formation using a two-stage Lagrangian model , 2006 .

[4]  Hua Zhao,et al.  Engine combustion instrumentation and diagnostics , 2001 .

[5]  Christoph Espey,et al.  The effect of TDC temperature and density on the liquid-phase fuel penetration in a D.I. Diesel engine , 1995 .

[6]  Christoph Espey,et al.  Diesel Engine Combustion Studies in a Newly Designed Optical-Access Engine Using High-Speed Visualization and 2-D Laser Imaging , 1993 .

[7]  Cherian A. Idicheria,et al.  Soot Formation in Diesel Combustion under High-EGR Conditions , 2005 .

[8]  M. Musculus,et al.  Multiple Simultaneous Optical Diagnostic Imaging of Early-Injection Low-Temperature Combustion in , 2006 .

[9]  H. Yanagihara.  A Study on Combustion Structure of Premixed Compression Ignition Diesel Engines , 2004 .

[10]  John E. Dec,et al.  The Effects of Injection Timing and Diluent Addition on Late-Combustion Soot Burnout in a Di Diese , 2000 .

[11]  John E. Dec,et al.  Soot Distribution in a D.I. Diesel Engine Using 2-D Imaging of Laser-induced Incandescence, Elastic Scattering, and Flame Luminosity , 1992 .

[12]  F. J. Salvador,et al.  Prediction of Spray Penetration by Means of Spray Momentum Flux , 2006 .

[13]  Shuji Kimura,et al.  New Combustion Concept for Ultra-Clean and High-Efficiency Small DI Diesel Engines , 1999 .

[14]  Paul C. Miles,et al.  A Parametric Study of Low-Temperature, Late-Injection Combustion in a HSDI Diesel Engine , 2005 .

[15]  R. J. Kee,et al.  Chemkin-II : A Fortran Chemical Kinetics Package for the Analysis of Gas Phase Chemical Kinetics , 1991 .

[16]  Robert J. Kee,et al.  CHEMKIN-III: A FORTRAN chemical kinetics package for the analysis of gas-phase chemical and plasma kinetics , 1996 .

[17]  John B. Heywood,et al.  Internal combustion engine fundamentals , 1988 .

[18]  Shuji Kimura,et al.  Ultra - Clean Combustion Technology Combining a Low - Temperature and Premixed Combustion Concept fo , 2001 .

[19]  J. Dec,et al.  The Influence of Fuel Volatility on the Liquid-Phase Fuel Penetration in a Heavy-Duty D.I. Diesel Engine , 1998 .

[20]  Bengt Johansson,et al.  A Study of the Homogeneous Charge Compression Ignition Combustion Process by Chemiluminescence Imaging , 1999 .

[21]  Rolf D. Reitz,et al.  2-Color Thermometry Experiments and High-Speed Imaging of Multi-Mode Diesel Engine Combustion , 2005 .

[22]  Dennis L. Siebers,et al.  Effects of Oxygenates on Soot Processes in DI Diesel Engines: Experiments and Numerical Simulations , 2003 .

[23]  Ryo Hasegawa,et al.  Numerical Analysis of Ignition Control in HCCI Engine , 2003 .

[24]  J. Dec.  A Conceptual Model of DI Diesel Combustion Based on Laser-Sheet Imaging* , 1997 .

[25]  John E. Dec,et al.  OH radical imaging in a DI diesel engine and the structure of the early diffusion flame , 1996 .

[26]  Hua Zhao,et al.  Effects of EGR on heat release in diesel combustion , 1998 .

[27]  Christoph Espey,et al.  Ignition and early soot formation in a DI diesel engine using multiple 2-D imaging diagnostics , 1995 .

[28]  Dennis L. Siebers,et al.  Scaling Liquid-Phase Fuel Penetration in Diesel Sprays Based on Mixing-Limited Vaporization , 1999 .

[29]  H Ogawa,et al.  An experimental analysis of low-temperature and premixed combustion for simultaneous reduction of NOx and particulate emissions in direct injection diesel engines , 2002 .

[30]  Yoshihiro Hotta,et al.  Combustion Improvement for Reducing Exhaust Emissions in IDI Diesel Engine , 1998 .

[31]  M. Musculus,et al.  In-cylinder unburned hydrocarbon visualization during low-temperature compression-ignition engine combustion using formaldehyde PLIF , 2007 .

[32]  Christoph Espey,et al.  Chemiluminescence Imaging of Autoignition in a DI Diesel Engine , 1998 .

[33]  Dennis L. Siebers,et al.  Relationship Between Ignition Processes and the Lift-Off Length of Diesel Fuel Jets , 2005 .

[34]  M. Musculus.  On the Correlation between NOx Emissions and the Diesel Premixed Burn , 2004 .

[35]  Dennis L. Siebers,et al.  Fuel Effects on Soot Processes of Fuel Jets at DI Diesel Conditions , 2003 .