A numerical investigation of the combustion kinetics of reactivity controlled compression ignition (RCCI) combustion in an optical engine

Abstract This work numerically investigates the detailed combustion kinetics occurring in an optical, reactivity controlled compression ignition (RCCI) engine. Experimental data from the engine combustion network (ECN) relating to spray H and optical RCCI engine spray/combustion were used for model validation. It was found that the RCCI combustion ignition occurred in the squish, bowl rim edge, and downstream of the spray periphery. To provide insight into key reaction pathways, an in-cylinder reaction pathway analysis method was used, and four characteristic RCCI combustion features were selected: (1) initial low temperature heat release (LTHR) from the high-reactivity fuel (n-heptane) on the spray periphery; (2) intense LTHR, where both iso-octane and n-heptane were converted to intermediates (e.g., CH2O) through oxygen-related reactions; (3) early stage high temperature heat release (HTHR) with CH2O as the core source species; (4) and intense HTHR, characterized by a substantial energy release. Further analysis of the reactive combustion surfaces demonstrated that the interior flame structure was controlled by OH-CO-O2 combustion kinetics and the exterior was controlled by CH2O-HCO (formyl radical) combustion kinetics. In addition, surrounding the reactive surfaces, iso-octane was consumed primarily through decomposition reactions, forming CH2O, which further fueled the following high temperature combustion.

[1]  Quanchang Zhang,et al.  Experimental investigation of the effects of diesel injection strategy on gasoline/diesel dual-fuel combustion , 2013 .

[2]  Mingfa Yao,et al.  Progress and recent trends in homogeneous charge compression ignition (HCCI) engines , 2009 .

[3]  P. Senecal,et al.  Multi-Dimensional Modeling of Direct-Injection Diesel Spray Liquid Length and Flame Lift-off Length using CFD and Parallel Detailed Chemistry , 2003 .

[4]  Zunqing Zheng,et al.  Experimental and modelling investigations of the diesel surrogate fuels in direct injection compression ignition combustion , 2017 .

[5]  M. Yao,et al.  A numerical study on the chemical kinetics process during auto-ignition of n-heptane in a direct injection compression ignition engine , 2018 .

[6]  Sibendu Som,et al.  Development and validation of spray models for investigating diesel engine combustion and emissions , 2009 .

[7]  Yu Li,et al.  A numerical investigation on NO2 formation reaction pathway in a natural gas–diesel dual fuel engine , 2018 .

[8]  Graham K. Hargrave,et al.  Time-Resolved Particle Image Velocimetry of dynamic interactions between hydrogen-enriched methane/air premixed flames and toroidal vortex structures , 2012 .

[9]  M. Musculus,et al.  Conceptual models for partially premixed low-temperature diesel combustion , 2013 .

[10]  John E. Dec,et al.  Comparisons of diesel spray liquid penetration and vapor fuel distributions with in-cylinder optical measurements , 2000 .

[11]  Zunqing Zheng,et al.  Experimental and numerical study on different dual-fuel combustion modes fuelled with gasoline and diesel , 2014 .

[12]  Zunqing Zheng,et al.  Development of a combined reduced primary reference fuel-alcohols (methanol/ethanol/propanols/butanols/n-pentanol) mechanism for engine applications , 2016 .

[13]  R. Reitz,et al.  Modeling the effects of drop drag and breakup on fuel sprays. Technical paper , 1993 .

[14]  S. Kokjohn.  Reactivity controlled compression ignition (RCCI) combustion , 2012 .

[15]  Zunqing Zheng,et al.  Experimental and Modelling Investigations of the Gasoline Compression Ignition Combustion in Diesel Engine , 2017 .

[16]  A. Di Benedetto,et al.  Effects of non-equidiffusion on unsteady propagation of hydrogen-enriched methane/air premixed flames , 2013 .

[17]  Zunqing Zheng,et al.  Experimental study of RCCI combustion and load extension in a compression ignition engine fueled with gasoline and PODE , 2016 .

[18]  Charles J. Mueller,et al.  Recent progress in the development of diesel surrogate fuels , 2009 .

[19]  Mingfa Yao,et al.  A reduced toluene reference fuel chemical kinetic mechanism for combustion and polycyclic-aromatic hydrocarbon predictions , 2015 .

[20]  M. Jia,et al.  Thermodynamic energy and exergy analysis of three different engine combustion regimes , 2016 .

[21]  P. K. Senecal,et al.  Large eddy simulation of a reacting spray flame with multiple realizations under compression ignition engine conditions , 2015 .

[22]  R. Reitz,et al.  Turbulence Modeling of Internal Combustion Engines Using RNG κ-ε Models , 1995 .

[23]  B. Johansson,et al.  Optical study on combustion transition from HCCI to PPC with gasoline compression ignition in a HD engine , 2016 .

[24]  Haifeng Liu,et al.  Multiple optical diagnostics on effect of fuel stratification degree on reactivity controlled compression ignition , 2017 .

[25]  M. Yao,et al.  Experimental and Modeling Investigations on Soot Formation of Ethanol, n-Butanol, 2,5-Dimethylfuran, and Biodiesel in Diesel Engines , 2017 .

[26]  C. Westbrook,et al.  A Comprehensive Modeling Study of n-Heptane Oxidation , 1998 .

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

[28]  M. Yao,et al.  A numerical investigation on methane combustion and emissions from a natural gas-diesel dual fuel engine using CFD model , 2017 .

[29]  Bengt Johansson,et al.  Gasoline partially premixed combustion, the future of internal combustion engines? , 2011 .

[30]  P. K. Senecal,et al.  An Investigation of Grid Convergence for Spray Simulations using an LES Turbulence Model , 2013 .

[31]  M. Musculus,et al.  Evaluating temperature and fuel stratification for heat-release rate control in a reactivity-controlled compression-ignition engine using optical diagnostics and chemical kinetics modeling , 2015 .

[32]  Mingfa Yao,et al.  Experimental and kinetic modeling study of a rich and a stoichiometric low-pressure premixed laminar 2,5-dimethylfuran/oxygen/argon flames , 2015 .

[33]  Christopher J. Rutland,et al.  A new droplet collision algorithm , 2000 .