SavedAdd your journal

Journals / International Journal of Automotive Science and Technology / 2026 / Volume: 10 Issue: 3

Numerical Investigation of the Effects of Equivalence Ratio and EGR on Combustion Characteristics in an n-Heptane Fueled HCCI Engine

Şükrü Ayhan Baydır(AFYON KOCATEPE ÜNİVERSİTESİ)0000-0001-7136-7860
H. Serdar Yücesu(GAZI UNIVERSITY, FACULTY OF TECHNOLOGY, DEPARTMENT OF AUTOMOTIVE ENGINEERING, AUTOMOTIVE ENGINEERING PR.)0000-0002-7805-6085
Pages
—
Publication Date
2026-10-25
🏛️Bibliographic metadata and full text access for this article are provided via DergiPark.
DergiPark Record ↗
✨

AI Summary & Key Takeaways

AI Insight
⚡ TL;DR(Too Long; Didn't Read)

Equivalence ratio therefore primarily governs the transition between misfire and stable ignition, whereas EGR modifies combustion phasing, temperature, and pressure within the stable-ignition condition.

📌 3 Key Takeaways

🎯
Objective & Hypothesis:Homogeneous Charge Compression Ignition (HCCI) combustion offers low nitrogen oxides and soot emissions with high thermal efficiency, but direct control of combustion phasing is lacking.
📊
Key Findings & Data:The model employed the Seiser et al. n-heptane mechanism and was validated against in-cylinder pressure data from an Antor 6LD400 single cylinder engine converted to HCCI operation (maximum pressure error 0.99%, RMSE 0.70 bar, R² 0.998).
💡
Conclusion & Impact:Equivalence ratio therefore primarily governs the transition between misfire and stable ignition, whereas EGR modifies combustion phasing, temperature, and pressure within the stable-ignition condition.
🔬Design:Modeling & Simulation
📍Scope:Comprehensive Sample
⚙️Variables:Combustion phasing · Equivalence ratio · Exhaust gas recirculation

Abstract

Homogeneous Charge Compression Ignition (HCCI) combustion offers low nitrogen oxides and soot emissions with high thermal efficiency, but direct control of combustion phasing is lacking. In this study, the effects of fuel-air equivalence ratio and exhaust gas recirculation (EGR) on the combustion characteristics of an n-heptane fueled HCCI engine were investigated using a single-zone chemical kinetic model implemented in Chemkin. The model employed the Seiser et al. n-heptane mechanism and was validated against in-cylinder pressure data from an Antor 6LD400 single cylinder engine converted to HCCI operation (maximum pressure error 0.99%, RMSE 0.70 bar, R² 0.998). The equivalence ratio was varied from 0.01 to 0.50, and the EGR rate from 0% to 35% at a fixed equivalence ratio of 0.4. A distinct transition from misfire to stable ignition occurred at equivalence ratios of approximately 0.34–0.36. Stable ignition at ϕ≥0.36 was predicted by all three mechanisms (Seiser et al., LLNL v3.1, and CRECK/POLIMI), whereas the response at ϕ=0.34 was mechanism-dependent. Above the threshold, the maximum in-cylinder temperature reached 1447 to 1919 °C and thermal efficiency 50% to 53%. Increasing the EGR rate from 0% to 35% reduced the maximum temperature from 1674 °C to 1449 °C and IMEP from 7.69 bar to 3.80 bar; at 35% EGR, the lower fuel energy supplied per cycle accounted for 87–92% of this IMEP reduction across the three mechanisms, and the remainder was attributable to a decrease in indicated thermal efficiency. All three mechanisms predicted an advance of combustion phasing with EGR, whereas the low-EGR response was mechanism-dependent. Cycle-end CO did not increase substantially because the predicted temperature remained above the CO oxidation threshold. Equivalence ratio therefore primarily governs the transition between misfire and stable ignition, whereas EGR modifies combustion phasing, temperature, and pressure within the stable-ignition condition.

🔖

Cite This Article

Baydır, Ş. A., Yücesu, H. S. (2026). Numerical Investigation of the Effects of Equivalence Ratio and EGR on Combustion Characteristics in an n-Heptane Fueled HCCI Engine. International Journal of Automotive Science and Technology, Volume: 10 Issue: 3. https://doi.org/10.30939/ijastech..2026087

📄 Full Text PDF Viewer

📄

PDF görüntüleyici hazırlanıyor...

References (71)

  1. Anderlohr JM, Bounaceur R, Pires Da Cruz A, Battin-Leclerc F. Modeling of Autoignition and NO Sensitization for the Oxidation of IC Engine Surrogate Fuels. Combust Flame. 2009;156(2):505–21. https://doi.org/10.1016/j.combustflame.2008.09.009
  2. Juttu S, Thipse SS, Marathe NV, Gajendra Babu MK. Diesel HCCI Combustion Control Parameters Study Using N-Heptane Reduced Chemical Kinetic Mechanism. Presented at Fifth International SAE India Mobility Conference on Emerging Automotive Technologies Global and Indian Perspective; 2008; New Delhi, India. https://doi.org/10.4271/2008-28-0036
  3. Anderlohr JM, Piperel A, Pires da Cruz A, Bounaceur R, Battin-Leclerc F, Dagaut P, et al. Influence of EGR Compounds on the Oxidation of an HCCI-Diesel Surrogate. Proc Combust Inst. 2009;32(2):2851–9. https://doi.org/10.1016/j.proci.2008.06.019
  4. Baydır ŞA. HCCI (homojen şarjlı sıkıştırma ile ateşlemeli) bir motorda yanma analizi (in Turkish) [the combustion analysis on HCCI (homogeneous charge compression ignition) engine] [thesis]. Gazi University; 2012.
  5. Curran HJ, Gaffuri P, Pitz WJ, Westbrook CK. A Comprehensive Modeling Study of N-Heptane Oxidation. Combust Flame. 1998;114(1–2):149–77. https://doi.org/10.1016/S0010-2180(97)00282-4
  6. Zheng Z, Yao M. Numerical Study on the Chemical Reaction Kinetics of N-Heptane for HCCI Combustion Process. Fuel. 2006;85(17–18):2605–15. https://doi.org/10.1016/j.fuel.2006.05.005
  7. Zhong B, Xi J. Reduced Kinetic Mechanism of N-Heptane Oxidation in Modeling Polycyclic Aromatic Hydrocarbon Formation in Opposed-Flow Diffusion Flames. Front. Energy Power Eng. China. 2008;2(3):326–32. https://doi.org/10.1007/s11708-008-0047-9
  8. Patel A, Kong S-C, Reitz RD. Development and Validation of a Reduced Reaction Mechanism for HCCI Engine Simulations. SAE International; 2004. https://doi.org/10.4271/2004-01-0558
  9. Curran HJ, Pitz WJ, Westbrook CK, Callahan CV, Dryer FL. Oxidation of Automotive Primary Reference Fuels at Elevated Pressures. Proc Combust Inst. 1998;27(1):379–87. https://doi.org/10.1016/S0082-0784(98)80426-8
  10. Tsurushima T. A New Skeletal PRF Kinetic Model for HCCI Combustion. Proc Combust Inst. 2009;32(2):2835–41. https://doi.org/10.1016/j.proci.2008.06.018
  11. Payri R, García-Oliver JM, Novella R, Pastor JM, López-Pintor D, Shang W. Application of an Optimized Mechanism of Primary Reference Fuel to Single Hole Sprays. Atomiz Spr. 2024;34(9):37–52. https://doi.org/10.1615/AtomizSpr.2024051862
  12. Niu B, Jia M, Chang Y, Dong X, Wang P, Cao J. Construction of Reduced Chemical Mechanisms Orientated toward Specific Applications: A Case Study of Primary Reference Fuel. Combustion Theory and Modelling. 2022;26(3):560–89. https://doi.org/10.1080/13647830.2022.2035824
  13. Duan J, Yang A, Wei W, Qin G. An N-Heptane Oxidation Mechanism Suitable for Low- to High-Temperature Combustion. Energies. 2025;18(5):1305. https://doi.org/10.3390/en18051305
  14. Komninos NP. Modeling HCCI Combustion: Modification of a Multi-Zone Model and Comparison to Experimental Results at Varying Boost Pressure. Appl Energy. 2009;86(10):2141–51. https://doi.org/10.1016/j.apenergy.2009.01.026
  15. Xu H, Liu M, Gharahbaghi S, Richardson S, Wyszynski M, Megaritis T. Modelling of HCCI Engines: Comparison of Single-Zone, Multi-Zone and Test Data. Presented at 2005 SAE Brasil Fuels & Lubricants Meeting; 2005; Rio de Janeiro, Brazil. https://doi.org/10.4271/2005-01-2123
  16. De Bellis V, Malfi E, Lanotte A, De Felice M, Teodosio L, Bozza F. A Tabulated Chemistry Multi-Zone Combustion Model of HCCI Engines Supplied with Pure Fuel and Fuel Blends. Energies. 2023;16(1):265. https://doi.org/10.3390/en16010265
  17. Fasulo G, Bozza F, Malfi E, Teodosio L. Development of a 0D Multi-Zone Model for Fast and Accurate Prediction of Homogeneous Charge Compression Ignition (HCCI) Engine. E3S Web Conf. 2021;312:07006. https://doi.org/10.1051/e3sconf/202131207006
  18. Çelik A, Kunt MA. A Study on Predicting Engine Performance Outputs by Machine Learning Algorithms in a Single Cylinder HCCI Engine. Engineering Perspective. 2026;6(1):57–68. https://doi.org/10.64808/engineeringperspective.1782349
  19. Aceves SM, Flowers DL, Westbrook CK, Smith JR, Pitz W, Dibble R, et al. A Multi-Zone Model for Prediction of HCCI Combustion and Emissions. Presented at SAE 2000 World Congress; 2000; Detroit, Michigan, United States. https://doi.org/10.4271/2000-01-0327
  20. Fiveland SB, Assanis DN. Development of a Two-Zone HCCI Combustion Model Accounting for Boundary Layer Effects. Presented at SAE 2001 World Congress; 2001; Detroit, Michigan, United States. https://doi.org/10.4271/2001-01-1028
  21. Ogink R, Golovitchev V. Gasoline HCCI Modeling: An Engine Cycle Simulation Code with a Multi-Zone Combustion Model. Presented at Spring Fuels & Lubricants Meeting & Exhibition; 2002; Reno, Nevada, United States. https://doi.org/10.4271/2002-01-1745
  22. Zhang H, Kaczmarek D, Rudolph C, Schmitt S, Gaiser N, Oßwald P, et al. Dimethyl Ether (DME) and Dimethoxymethane (DMM) as Reaction Enhancers for Methane: Combining Flame Experiments with Model-Assisted Exploration of a Polygeneration Process. Combust Flame. 2022;237:111863. https://doi.org/10.1016/j.combustflame.2021.111863
  23. Machrafi H. Experimental Validation of a Kinetic Multi-Component Mechanism in a Wide HCCI Engine Operating Range for Mixtures of n-Heptane, Iso-Octane and Toluene: Influence of EGR Parameters. Energy Convers Manag. 2008;49(11):2956–65. https://doi.org/10.1016/j.enconman.2008.06.016
  24. Sanci ME. A Physics-Constrained Neural Network Framework for Surrogate Modeling and Multi-Objective Optimization of an RCCI Engine. IJASTECH. 2026;10(3):572–85. https://doi.org/10.30939/ijastech.1935208
  25. Dec JE, Sjöberg M. Isolating the Effects of Fuel Chemistry on Combustion Phasing in an HCCI Engine and the Potential of Fuel Stratification for Ignition Control. Presented at SAE 2004 World Congress & Exhibition; 2004; Detroit, Michigan, United States. https://doi.org/10.4271/2004-01-0557
  26. Sjöberg M, Dec JE. An Investigation into Lowest Acceptable Combustion Temperatures for Hydrocarbon Fuels in HCCI Engines. Proc Combust Inst. 2005;30(2):2719–26. https://doi.org/10.1016/j.proci.2004.08.132
  27. Chen YH, Chen JY. Development of Isooctane Skeletal Mechanisms for Fast and Accurate Predictions of SOC and Emissions of HCCI Engines Based on LLNL Detailed Mechanism. Presented at 2005 Fall Meeting Western States Combustion Institute; 2005; Stanford, CA, USA.
  28. Belkebir SM, Khelidj B, Abbes MT. Effects of EGR and Alternative Fuels on Homogeneous Charge Compression Ignition (HCCI) Combustion Mode. IJDNE. 2021;16(2):135–44. https://doi.org/10.18280/ijdne.160203
  29. Soyhan HS, Yasar H, Walmsley H, Head B, Kalghatgi GT, Sorusbay C. Evaluation of Heat Transfer Correlations for HCCI Engine Modeling. Appl Therm Eng. 2009;29(2–3):541–9. https://doi.org/10.1016/j.applthermaleng.2008.03.014
  30. Sanli A, Ozsezen AN, Kilicaslan I, Canakci M. The Influence of Engine Speed and Load on the Heat Transfer between Gases and In-Cylinder Walls at Fired and Motored Conditions of an IDI Diesel Engine. Appl Therm Eng. 2008;28(11–12):1395–404. https://doi.org/10.1016/j.applthermaleng.2007.10.005
  31. Chang J, Güralp O, Filipi Z, Assanis DN, Kuo T-W, Najt P, et al. New Heat Transfer Correlation for an HCCI Engine Derived from Measurements of Instantaneous Surface Heat Flux. SAE International; 2004. https://doi.org/10.4271/2004-01-2996
  32. Rabeti M, Ranjbar AA, Jahanian O, Safieddin Ardebili SM, Solmaz H. Investigation of Important Semi-Empirical Heat Transfer Models for a Natural Gas-Fueled HCCI Engine. Energy Rep. 2021;7:8652–66. https://doi.org/10.1016/j.egyr.2021.11.011
  33. Kethüdaoğlu G, Aktaş F, Karaaslan S, Polat S, Dinler N. Investigation of Conversion of a Diesel Engine to Homogeneous Charge Compression Ignition Engine Using N-Heptane: A Zero-Dimensional Modeling. Int J Energy Studies. 2023;8(3):535–56. https://doi.org/10.58559/ijes.1325924
  34. Veza I, Said MFM, Latiff ZA, Hasan MF, Jalal RIA, Ibrahim NMIN. Simulation of Predictive Kinetic Combustion of Single Cylinder HCCI Engine. AIP Conf Proc. 2019;2059(1):020017. https://doi.org/10.1063/1.5085960
  35. Türkcan Ö, Polat S. Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts. IJASTECH. 2025;9(4):626–36. https://doi.org/10.30939/ijastech.1821778
  36. Seiser R, Pitsch H, Seshadri K, Pitz WJ, Curran HJ. Extinction and Autoignition of N-Heptane in Counterflow Configuration. Proc Combust Inst. 2000;28(2):2029–37. https://doi.org/10.1016/S0082-0784(00)80610-4
  37. Woschni G. A Universally Applicable Equation for the Instantaneous Heat Transfer Coefficient in the Internal Combustion Engine. Presented at National Fuels and Lubricants, Powerplants, Transportation Meetings; 1967; Pittsburgh, Pennsylvania, United States. https://doi.org/10.4271/670931
  38. Hohenberg GF. Advanced Approaches for Heat Transfer Calculations. Presented at 1979 SAE International Off-Highway and Powerplant Congress and Exposition; 1979; Milwaukee, Wisconsin, USA. https://doi.org/10.4271/790825
  39. Curran HJ, Gaffuri P, Pitz WJ, Westbrook CK. A Comprehensive Modeling Study of Iso-Octane Oxidation. Combust Flame. 2002;129(3):253–80. https://doi.org/10.1016/S0010-2180(01)00373-X
  40. Willmott CJ, Ackleson SG, Davis RE, Feddema JJ, Klink KM, Legates DR, et al. Statistics for the Evaluation and Comparison of Models. J Geophys Res Oceans. 1985;90(C5):8995–9005. https://doi.org/10.1029/JC090iC05p08995
  41. Montgomery DC, Peck EA, Vining GG. Introduction to Linear Regression Analysis. John Wiley & Sons; 2013.
  42. Komiyama K, Heywood JB. Predicting NOx Emissions and Effects of Exhaust Gas Recirculation in Spark-Ignition Engines. SAE International; 1973. https://doi.org/10.4271/730475
  43. Heywood JB. Internal Combustion Engine Fundamentals. 2nd ed. McGraw Hill; 2018.
  44. Zheng M, Reader GT, Hawley JG. Diesel Engine Exhaust Gas Recirculation – A Review on Advanced and Novel Concepts. Energy Convers Manag. 2004;45(6):883–900. https://doi.org/10.1016/S0196-8904(03)00194-8
  45. Sjöberg M, Dec JE, Hwang W. Thermodynamic and Chemical Effects of EGR and Its Constituents on HCCI Auto-ignition. Presented at SAE World Congress & Exhibition; 2007; Detroit, Michigan, United States. https://doi.org/10.4271/2007-01-0207
  46. Dec JE. A Computational Study of the Effects of Low Fuel Loading and EGR on Heat Release Rates and Combustion Limits in HCCI Engines. Presented at SAE 2002 World Congress & Exhibition; 2002; Detroit, Michigan, United States. https://doi.org/10.4271/2002-01-1309
  47. Hutter R, Ritzmann J, Elbert P, Onder C. Low-Load Limit in a Diesel-Ignited Gas Engine. Energies. 2017;10(10):1450. https://doi.org/10.3390/en10101450
  48. Aceves SM, Flowers DL, Martinez-Frias J, Smith JR, Dibble R, Au M, et al. HCCI Combustion: Analysis and Experiments. SAE International; 2001. https://doi.org/10.4271/2001-01-2077
  49. Ladommatos N, Abdelhalim SM, Zhao H, Hu Z. The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 1: Effect of Reducing Inlet Charge Oxygen. SAE International; 1996. https://doi.org/10.4271/961165
  50. Ladommatos N, Abdelhalim SM, Zhao H, Hu Z. The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 2: Effects of Carbon Dioxide. SAE International; 1996. https://doi.org/10.4271/961167
  51. Ladommatos N, Abdelhalim SM, Zhao H, Hu Z. The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 3: Effects of Water Vapour. SAE International; 1997. https://doi.org/10.4271/971659
  52. Ladommatos N, Abdelhalim SM, Zhao H, Hu Z. The Dilution, Chemical, and Thermal Effects of Exhaust Gas Recirculation on Diesel Engine Emissions - Part 4: Effects of Carbon Dioxide and Water Vapour. SAE International; 1997. https://doi.org/10.4271/971660
  53. Yücesu HS, Çanakçı M, Çınar C, Can Ö, Şahin F, Öztürk E, et al. Homojen Dolgulu Sıkıştırma İle Ateşlemeli Motorlarda Yanma, Motor Performansı ve Egzoz Emisyonlarının İncelenmesi (in Turkish) [Investigation of Combustion, Engine Performance, and Exhaust Emissions in Homogeneous Charge Compression Ignition Engines]. Ankara: TÜBİTAK; 2011.
  54. Can Ö. Bir DI dizel motorda etanol ön karışımlı kısmi-HCCI uygulamasının yanma ve emisyonlar üzerine etkilerinin incelenmesi (in Turkish) [an investigation of the effects of partial HCCI application with premixed ethanol on combustion and emissions in a DI diesel engine] [thesis]. Gazi University; 2012.
  55. Babushok VI, Tsang W. Kinetic Modeling of Heptane Combustion and PAH Formation. Journal of Propulsion and Power. 2004;20(3):403–14. https://doi.org/10.2514/1.2323
  56. Coskun G, Delil Y, Demir U. Analysis of an HCCI Engine Combustion Using Toluene Reference Fuel for Different Equivalence Ratios – Comparison of Experimental Results with CFD and SRM Simulations. Fuel. 2019;247:217–27. https://doi.org/10.1016/j.fuel.2019.03.046
  57. Zhang J, Huang Z, Han D. Effects of Mechanism Reduction on the Exergy Losses Analysis in N-Heptane Autoignition Processes. International Journal of Engine Research. 2020;21(9):1764–77. https://doi.org/10.1177/1468087419836870
  58. Niemeyer KE, Sung C-J. Mechanism Reduction for Multi-component Surrogates: A Case Study Using Toluene Reference Fuels. Combust Flame. 2014;161(11):2752–64. https://doi.org/10.1016/j.combustflame.2014.05.001
  59. Chandrakar CK, Varma PS, Mittal M. Thermodynamics Based Modeling of Various In-Cylinder Processes and Spark Ignition Engine Cycle with a Focus on Sub-Models Assessment. Sci Rep. 2025;15(1):30345. https://doi.org/10.1038/s41598-025-15819-7
  60. Mehl M, Pitz WJ, Sjöberg M, Dec JE. Detailed Kinetic Modeling of Low-Temperature Heat Release for PRF Fuels in an HCCI Engine. SAE International; 2009. https://doi.org/10.4271/2009-01-1806
  61. Mehl M, Pitz WJ, Westbrook CK, Curran HJ. Kinetic Modeling of Gasoline Surrogate Components and Mixtures under Engine Conditions. Proc Combust Inst. 2011;33(1):193–200. https://doi.org/10.1016/j.proci.2010.05.027
  62. Ranzi E, Frassoldati A, Stagni A, Pelucchi M, Cuoci A, Faravelli T. Reduced Kinetic Schemes of Complex Reaction Systems: Fossil and Biomass-Derived Transportation Fuels. Int. J. Chem. Kinet. 2014;46(9):512–42. https://doi.org/10.1002/kin.20867
  63. Stagni A, Cuoci A, Frassoldati A, Faravelli T, Ranzi E. Lumping and Reduction of Detailed Kinetic Schemes: An Effective Coupling. Ind. Eng. Chem. Res. 2014;53(22):9004–16. https://doi.org/10.1021/ie403272f
  64. Stagni A, Frassoldati A, Cuoci A, Faravelli T, Ranzi E. Skeletal Mechanism Reduction through Species-Targeted Sensitivity Analysis. Combust Flame. 2016;163:382–93. https://doi.org/10.1016/j.combustflame.2015.10.013
  65. Battin-Leclerc F. Detailed Chemical Kinetic Models for the Low-Temperature Combustion of Hydrocarbons with Application to Gasoline and Diesel Fuel Surrogates. Progress in Energy and Combustion Science. 2008;34(4):440–98. https://doi.org/10.1016/j.pecs.2007.10.002
  66. Westbrook CK, Pitz WJ, Herbinet O, Curran HJ, Silke EJ. A Comprehensive Detailed Chemical Kinetic Reaction Mechanism for Combustion of n-Alkane Hydrocarbons from n-Octane to n-Hexadecane. Combust Flame. 2009;156(1):181–99. https://doi.org/10.1016/j.combustflame.2008.07.014
  67. Han X, Weng W, He Y, Wang Z, Konnov AA. Experimental and Kinetic Modelling Study on the Laminar Burning Velocities of Ultra-Lean n-Heptane Flames at Atmospheric Pressure. Combust Flame. 2024;268:113613. https://doi.org/10.1016/j.combustflame.2024.113613
  68. Machrafi H, Cavadias S, Amouroux J. A Parametric Study on the Emissions from an HCCI Alternative Combustion Engine Resulting from the Auto-Ignition of Primary Reference Fuels. Appl Energy. 2008;85(8):755–64. https://doi.org/10.1016/j.apenergy.2008.02.005
  69. Machrafi H, Cavadias S, Guibert P. An Experimental and Numerical Investigation on the Influence of External Gas Recirculation on the HCCI Autoignition Process in an Engine: Thermal, Diluting, and Chemical Effects. Combust Flame. 2008;155(3):476–89. https://doi.org/10.1016/j.combustflame.2008.05.001
  70. Sanci ME. A Physics-Constrained Neural Network Framework for Surrogate Modeling and Multi-Objective Optimization of an RCCI Engine. IJASTECH. 2026;10(3):572–85. https://doi.org/10.30939/ijastech.1935208
  71. Türkcan Ö, Polat S. Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts. IJASTECH. 2025;9(4):626–36. https://doi.org/10.30939/ijastech.1821778