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Fuel Stratification for Low-Load HCCI Combustion: Performance & Fuel-PLIF Measurements
Technical Paper
2007-01-4130
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Fuel stratification has been investigated as a means of improving the low-load combustion efficiency in an HCCI engine. Several stratification techniques were examined: different GDI injectors, increased swirl, and changes in injection pressure, to determine which parameters are effective for improving the combustion efficiency while maintaining NOx emissions below U.S. 2010 limits. Performance and emission measurements were obtained in an all-metal engine. Corresponding fuel distribution measurements were made with fuel PLIF imaging in a matching optically accessible engine. The fuel used was iso-octane, which is a good surrogate for gasoline.
For an idle fueling rate (ϕ = 0.12), combustion efficiency was improved substantially, from 64% to 89% at the NOx limit, using delayed fuel injection with a hollow-cone injector at an injection pressure of 120 bar. Relative to this base case, changing to an 8-hole injector provided the single largest improvement, increasing combustion efficiency to 92%. The effects of swirl varied with injector type, but increased injection pressure was beneficial for both injectors. The highest combustion efficiency of 92.5% at the NOx limit was achieved with the 8-hole injector and an injection pressure of 170 bar, with low swirl.
Quantitative fuel-distribution maps derived from the PLIF images showed good agreement with the combustion-efficiency and NOx-emission measurements in the metal engine. The images showed that at the NOx limit, fuel distributions and maximum equivalence ratios (ϕ) are similar for the two injectors, with delayed injection producing a single large fuel pocket. Fuel-mass histograms suggest that the 8-hole injector improved the combustion-efficiency at the NOx limit by reducing the fraction of low-ϕ regions, but a wider field of view is required to fully confirm this. The images also show that increased swirl inhibited the mixing of fuel into the center of the combustion chamber, explaining the slower mixing rates observed in the metal engine. A general finding is that the combustion-efficiency/NOx tradeoff improves when fuel can be injected as late as possible with acceptable levels of NOx. Therefore, techniques that provide even faster mixing have the potential for further improvements.
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Hwang, W., Dec, J., and Sjöberg, M., "Fuel Stratification for Low-Load HCCI Combustion: Performance & Fuel-PLIF Measurements," SAE Technical Paper 2007-01-4130, 2007, https://doi.org/10.4271/2007-01-4130.Also In
References
- Dec, J. E. Sjöberg, M. “Isolating the Effects of Fuel Chemistry on Combustion Phasing in an HCCI Engine and the Potential of Fuel Stratification for Ignition Control,” SAE paper 2004-01-0557 2004
- Dec, J.E. “A Computational Study of the Effects of Low Fuel Loading and EGR on Heat Release Rates and Combustion Limits in HCCI Engines,” SAE paper 2002-01-1309 2002
- Dec, J. E. Sjöberg, M. “A Parametric Study of HCCI Combustion - the Sources of Emissions at Low Loads and the Effects of GDI Fuel Injection,” SAE paper 2003-01-0752 2003
- Sjöberg, M. Dec, J. E. “Combined Effects of Fuel-Type and Engine Speed on Intake Temperature Requirements and Completeness of Bulk-Gas Reactions in an HCCI Engine,” SAE paper 2003-01-3173 2003
- Sjöberg, M. Dec, J. E. “An investigation into lowest acceptable combustion temperatures for hydrocarbon fuels in HCCI engines,” Proc. Combust. Inst. 30 2719 2726 2005
- Jun, D. Iida, N. “A Study of High Combustion Efficiency and Low CO Emission in a Natural Gas HCCI Engine,” SAE Paper 2004-01-1974 2004
- Aroonsrisopon, P. W. Werner, P. Waldman, J. O. Sohm, V. Foster, D. E. Morikawa, T. Minoru, I. “Expanding the HCCI Operation with the Charge Stratification,” SAE paper 2004-01-1756 2004
- Sjöberg, M. Edling, L.-O. Eliassen, T. Magnusson, L. Ångström, H.-E. “GDI HCCI: Effects of Injection Timing and Air Swirl on Fuel Stratification, Combustion and Emissions Formation,” SAE paper 2002-01-0106 2002
- Hultqvist A. Christensen, M. Johansson, B. Richter, M. Nygren, J. Hult, H. Aldén, M. “The HCCI Combustion Process in a Single Cycle - High-Speed Fuel Tracer LIF and Chemiluminescence Imaging,” SAE paper 2002-01-0424 2002
- Thirouard, B. Cherel, J. Knop, V. “Investigation of Mixture Quality Effect on CAI Combustion,” SAE paper 2005-01-0141 2005
- Reuss, D. L. Sick, V. “Inhomogeneities in HCCI Combustion: An Imaging Study,” SAE paper 2005-01-2122 2005
- Hultqvist, A. Christensen, M. Johansson, B. Franke, A. Richter, M. Aldén, M. “A Study of the Homogeneous Charge Compression Ignition Combustion Process by Chemiluminescence Imaging,” SAE paper 1999-01-3680 1999
- Kumano, K. Iida, N. “Analysis of the Effect of Charge Inhomogeneity on HCCI Combustion by Chemiluminescence Measurement,” SAE paper 2004-01-1902 2004
- Dec, J. E. Hwang, W. Sjöberg, M. “An Investigation of Thermal Stratification in HCCI Engines using Chemiluminescence Imaging,” SAE paper 2006-01-1518 2006
- Richter, M. Engström, J. Franke, A. Aldén, M. Hultqvist, A. Johansson, B. “The Influence of Charge Inhomogeneity on the HCCI Combustion Process,” SAE paper no. 2000-01-2868 2000
- Steeper, R. De Zilwa, S. Fayoux, A. “Co-evaporative Tracer-PRF Mixtures for LIF Measurements in Optical HCCI Engines,” SAE paper 2005-01-0111 2005
- Han, D. Steeper, R. R. “Examination of Iso-octane/Ketone Mixtures for Quantitative LIF Measurements in a DISI Engine,” SAE paper 2002-01-0837 2002
- Schulz, C. Sick, V. “Tracer-LIF diagnostics: quantitative measurement of fuel concentration, temperature and fuel/air ratio in practical combustion systems,” Prog. Energy Combust. Sci. 31 75 121 2005
- De Zilwa, S. Steeper, R. “Predicting Emissions from HCCI Engines using LIF Imaging,” SAE paper 2005-01-3747 2005
- De Zilwa, S. Steeper, R. “Predicting NO x Emissions from HCCI Engines Using LIF Imaging,” SAE paper 2006-01-0025 2006
- Steeper, R. R. De Zilwa, S. “Improving the NO x -CO 2 Trade-Off of an HCCI Engine Using a Multi-Hole Injector,” SAE paper 2007-01-0180 2007
- Heywood, J. B. Internal Combustion Engine Fundamentals McGraw-Hill New York 1988
- Koban, W. Koch, J. D. Hanson, R. K. Schulz, C. “Absorption and fluorescence of toluene vapor at elevated temperatures,” Phys. Chem. Chem. Phys. 6 2940 2945 2004
- Hwang, W. Dec, J. E. “A Laser-Induced Fluorescence Diagnostic for Measuring Fuel and Corresponding Temperature Distributions in Direct-Injection Internal Combustion Engines,” Appl. Phys. B 2007
- Sjöberg, M. Dec, J. E. “An Investigation of the Relationship between Measured Intake Temperature, BDC Temperature, and Combustion Phasing for Premixed and DI HCCI Engines,” SAE Paper 2004-01-1900 2004
- VanDerWege, B. A. Hochgreb, S. “Effects of Fuel Volatility and Operating Conditions on Fuel Sprays in DISI Engines: (1) Imaging Investigation,” SAE Paper 2000-01-0535 2000
- Christensen, M. Hultqvist, A. Johansson, B. “The effect of top-land geometry on emissions of unburned hydrocarbons from a homogeneous charge compression ignition (HCCI) engine,” SAE paper 2001-01-1893 2001
- Aceves, S. M. Flowers, D. L. Espinosa-Loza, F. Martinez-Frias, J. Dibble, R. W. Christensen, M. Johansson, B. Hessel, R. P. “Piston-Liner Crevice Geometry Effect on HCCI Combustion by Multi-Zone Analysis,” SAE paper 2002-0-2869 2002
- Hwang, W. Dec, J. E. Sjöberg, M. “Spectroscopic and Chemical-Kinetic Analysis of the Phases of HCCI Autoignition and Combustion for Single- and Two-Stage Ignition Fuels,” Combust. Flame 2007