Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts

Ömer Türkcan; Seyfi Polat

doi:10.30939/ijastech..1821778

Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts

Abstract

This study examines the combustion and emission behavior of a four-stroke Wankel rotary engine operated in Homogeneous Charge Compression Ignition (HCCI) mode using n-heptane fuel over excess-air ratios of λ = 2.2–2.8. A validated three-dimensional CONVERGE CFD model of the Mazda Renesis RX-8 13B MSP engine—verified against experimental spark-ignition pressure data—was used to assess HCCI performance. The simulations employed semi detailed chemistry (SAGE), Renormalization Group (RNG) k–ε turbulence modelling, and adaptive mesh refinement to capture the multi-stage auto-ignition process. The analysis encompassed key combustion and emission indicators, including in-cylinder and peak pressure, heat-release rate, cumulative heat-release behavior, maximum pressure-rise rate, combustion-phasing metrics crank angle at 10% of total heat released (CA10), crank angle at 50% of total heat released (CA50), crank angle at 90% of total heat released (CA90), combustion duration, and major exhaust species carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC) and nitrogen oxides (NOₓ). Stable HCCI operation was achieved only within a narrow range: λ = 2.2–2.8. Richer mixtures exceeded the 10 bar/°CA knock-related pressure-rise-rate limit, while leaner mixtures resulted in misfire. Increasing λ delayed auto-ignition, weakened high-temperature oxidation, and extended combustion duration. CO and HC emissions rose with λ due to reduced combustion temperature and strong near-wall quenching driven by the Wankel chamber’s high surface-to-volume ratio, whereas NOx remained extremely low and nearly eliminated for λ ≥ 2.4. Overall, the findings confirm that HCCI can be successfully realized in a Wankel rotary engine with ultra-low NOx emissions, provided operation remains within its narrow λ window. These results underscore the potential of Wankel HCCI concepts for lightweight aviation and unmanned aerial vehicle (UAV) propulsion, while highlighting the need for improved mixture preparation and combustion-phasing control for practical implementation.

Keywords

Thanks

The authors thank to Convergent Science for providing CONVERGE Academic licenses and technical support for this work.

References

[1] Heywood JB. Internal Combustion Engine Fundamentals. 2nd ed. McGraw-Hill Education; 2018.
[2] Stone R. Introduction to Internal Combustion Engines. 4th ed. Palgrave Macmillan; 2012.
[3] Ferguson CR, Kirkpatrick AT. Internal Combustion Engines: Ap-plied Thermosciences. 3rd ed. John Wiley & Sons; 2015.
[4] Turns SR. An Introduction to Combustion: Concepts and Applica-tions. 3rd ed. McGraw-Hill Education; 2013.
[5] Nagareddy S, Rajeswaran SS, Jaganathan D, Bala Subramanian VP, Neelakandan V. Turbocharged six-cylinder direct injection hydrogen fueled spark ignition engine combustion and NOx con-trol model. Eng Perspect. 2025;5(3):100–110. https://doi.org/10.29228/eng.pers.82203
[6] Uyumaz A, Boz F, Yılmaz E, Solmaz H, Polat S. Developments in methods for reducing vehicle exhaust emissions. Mehmet Akif Ersoy Univ J Sci Inst. 2017;8(Special Issue 1):15–24.
[7] Zhao H. HCCI and CAI Engines for the Automotive Industry. Woodhead Publishing; 2007. doi: 10.1533/9781845693541
[8] Dec JE. Advanced compression-ignition engines—Understanding the in-cylinder processes. Proc Combust Inst. 2009;32(2):2727–2742. https://doi.org/10.1016/j.proci.2008.08.008

[9] Polat S, Yücesu HS, Kannan K, Uyumaz A, Solmaz H, Shahbakhshi M. Experimental comparison of different injection timings in an HCCI engine fueled with n-heptane. Int J Automot Sci Technol. 2017;1(1):1–10.
[10] Dam QT, Haidar F, Mama N, Chennapalli SJ. Modeling and simulation of an Internal Combustion Engine using Hydrogen: A MATLAB implementation approach. Eng Perspect. 2024;4(3):108-118. https://doi.org/10.29228/eng.pers.76219
[11] Polat S, Solmaz H, Calam A, Yılmaz E. Estimation of the COVIMEP variation in a HCCI engine. J Polytechnic. 2020;23(3):721–727. https://doi.org/10.2339/politeknik.567865
[12] Çınar C, Uyumaz A, Polat S, Yılmaz E, Can Ö, Solmaz H. Com-bustion and performance characteristics of an HCCI engine utiliz-ing trapped residual gas via reduced valve lift. Appl Therm Eng. 2016;100:586–594. https://doi.org/10.1016/j.applthermaleng.2016.01.155
[13] Polat S, Solmaz H, Uyumaz A, Calam A, Yılmaz E, Yücesu HS. An experimental research on the effects of negative valve overlap on performance and operating range in a homogeneous charge compression ignition engine with RON40 and RON60 fuels. J Eng Gas Turbines Power. 2020;142(5):051010. https://doi.org/10.1115/1.4045572
[14] Polat S, Kannan K, Shahbakhshi M, Uyumaz A, Yücesu HS. An experimental study for the effects of supercharging on perfor-mance and combustion of an early direct injection HCCI engine. Presented at the 2nd International Research Conference on Sci-ence, Technology, Engineering and Management; 2015; Dubai, United Arab Emirates.
[15] Polat S. An experimental investigation on combustion, perfor-mance and ringing operation characteristics of a low compression ratio early direct injection HCCI engine with ethanol fuel. Fuel. 2020;277:118092. https://doi.org/10.1016/j.fuel.2020.118092
[16] Uyumaz A, Solmaz H, Boz F, Yılmaz E, Polat S. Effects of lambda on combustion characteristics in a Reactivity Controlled Compression Ignition (RCCI) engine. Afyon Kocatepe Univ J Sci Eng. 2017;17(3):1146–1156. doi: 10.5578/fmbd.66127
[17] Liang J, Chen W. A comprehensive review of Wankel rotary engine dynamics, combustion characteristics, and design ad-vantages for high-power-density applications. Appl Therm Eng. 2019;160:114090. https://doi.org/10.1016/j.applthermaleng.2019.114090
[18] Zhang Y, Liu H, Zhao X. Performance enhancement and struc-tural optimization of small-scale Wankel rotary engines for UAV propulsion. Energy Convers Manag. 2023;286:117028. https://doi.org/10.1016/j.enconman.2023.117028
[19] Ishikawa T, Yamamoto K. Recent advancements in rotary engine technologies for lightweight aerial vehicles. Aerosp Sci Technol. 2021;112:106623. https://doi.org/10.1016/j.ast.2021.106623
[20] Bishop RF, Gray TN, Meyer J. Performance assessment of a Wankel rotary engine for hybrid-electric unmanned aircraft appli-cations. Aerosp Sci Technol. 2020;105:106069. https://doi.org/10.1016/j.ast.2020.106069
[21] Helbling F, Schürmann T, Guzzella L. Modeling and control of a Wankel rotary engine for unmanned aerial vehicle propulsion. Control Eng Pract. 2018;73:41–50. https://doi.org/10.1016/j.conengprac.2018.01.010
[22] Liang J, Chen W. A comprehensive review of Wankel rotary engine dynamics and design for high-power-density applications. Appl Therm Eng. 2019;160:114090.
[23] Yao M, Zheng Z, Liu H. Progress and recent trends in homoge-neous charge compression ignition (HCCI) engines—A compre-hensive review. Renew Sustain Energy Rev. 2020;119:109571. https://doi.org/10.1016/j.rser.2019.109571
[24] Stettler MEJ, Eastham SD, Barrett SRH. Air quality and climate impacts of aviation emissions: Current understanding and future prospects. Prog Energy Combust Sci. 2021;84:100927. . https://doi.org/10.1016/j.pecs.2020.100927
[25] Meng H, Ji C, Shen J, Yang J, Xin G, Chang K, Wang S. Ana-lyzing the effects of cooled EGR on the knock of hydrogen-fueled Wankel rotary engine. Int J Hydrogen Energy. 2022;47:33094–33104. https://doi.org/10.1016/j.ijhydene.2022.07.185
[26] Krastev VK, Silvestri L, Falcucci G. A modified version of the RNG k–ε turbulence model for the scale-resolving simulation of internal combustion engines. Energies. 2017;10:2116. https://doi.org/10.3390/en10122116
[27] Wang BL, Lee CW, Reitz RD, Miles PC, Han Z. A generalized renormalization group turbulence model and its application to a light-duty diesel engine operating in a low-temperature combus-tion regime. Int J Engine Res. 2012;14(3):279–292. https://doi.org/10.1177/1468087412465379
[28] Ikpe AE, Bassey MO. Computational Fluid Dynamics of Four Stroke In-Cylinder Charge Behavior at Distinct Valve Lift Open-ing Clearance in Spark Ignition Reciprocating Internal Combus-tion Renault Engine. Int J Automot Sci Technol. 2024;8(1):1-22. doi:10.30939/ijastech..1337386.
[29] Arslan TA, Bayrakçeken H, Yavuz H. CFD Analysis of Slosh-ing in the Fuel Tank of a Heavy Vehicle with Emergency Braking System. Int J Automot Sci Technol. 2023;7(4):340-348. doi:10.30939/ijastech..1360466.
[30] Halis S, Solmaz H, Polat S, Yücesu HS. Numerical Study of the Effects of Lambda and Injection Timing on RCCI Combustion Mode. Int J Automot Sci Technol. 2022;6(2):120-6. Doi: 10.30939/ijastech..1105470
[31] Andrae JCG, Head RA. HCCI experiments with gasoline surro-gate fuels modelled by a semidetailed chemical kinetic model. Combust Flame. 2009;156:842–851. https://doi.org/10.1016/j.combustflame.2008.10.002
[32] Polat S, Yücesu HS, Uyumaz A, Kannan K, Shahbakhti M. An experimental investigation on combustion and performance char-acteristics of supercharged HCCI operation in low compression ratio engine setting. Appl Therm Eng. 2020;180:115858. https://doi.org/10.1016/j.applthermaleng.2020.115858
[33] Calam A, Solmaz H, Yılmaz E, İçingür Y. Investigation of effect of compression ratio on combustion and exhaust emissions in an HCCI engine. Energy. 2019;168:1208–1216. https://doi.org/10.1016/j.energy.2018.12.023
[34] Cinar C, Uyumaz A, Solmaz H, Topgul T. Effects of valve lift on the combustion and emissions of a HCCI gasoline engine. Energy Convers Manag. 2015;94:159–168. https://doi.org/10.1016/j.enconman.2015.01.066

Details

Primary Language

English

Subjects

Automotive Combustion and Fuel Engineering

Journal Section

Research Article

Authors

Ömer Türkcan
0000-0001-5004-7227
Türkiye

Seyfi Polat ^*
0000-0002-7196-3053
Türkiye

Publication Date

December 31, 2025

Submission Date

November 11, 2025

Acceptance Date

December 24, 2025

Published in Issue

Year 2025 Volume: 9 Number: 4

DOI

https://doi.org/10.30939/ijastech..1821778

IZ

https://izlik.org/JA45RC23ZH

Cite

RIS / Bibtex

APA

Türkcan, Ö., & Polat, S. (2025). Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts. International Journal of Automotive Science And Technology, 9(4), 626-636. https://doi.org/10.30939/ijastech..1821778

AMA

1.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):626-636. doi:10.30939/ijastech.1821778

Chicago

Türkcan, Ömer, and Seyfi Polat. 2025. “Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts”. International Journal of Automotive Science And Technology 9 (4): 626-36. https://doi.org/10.30939/ijastech. 1821778.

EndNote

Türkcan Ö, Polat S (December 1, 2025) Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts. International Journal of Automotive Science And Technology 9 4 626–636.

IEEE

[1]Ö. Türkcan and S. Polat, “Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts”, IJASTECH, vol. 9, no. 4, pp. 626–636, Dec. 2025, doi: 10.30939/ijastech..1821778.

ISNAD

Türkcan, Ömer - Polat, Seyfi. “Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts”. International Journal of Automotive Science And Technology 9/4 (December 1, 2025): 626-636. https://doi.org/10.30939/ijastech. 1821778.

JAMA

1.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;9:626–636.

MLA

Türkcan, Ömer, and Seyfi Polat. “Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts”. International Journal of Automotive Science And Technology, vol. 9, no. 4, Dec. 2025, pp. 626-3, doi:10.30939/ijastech. 1821778.

Vancouver

1.Ömer Türkcan, Seyfi Polat. Combustion and Emission Behaviour of a HCCI Wankel Engine Across Lambda Variations: Insights for Future Aviation-Oriented Rotary Engine Concepts. IJASTECH. 2025 Dec. 1;9(4):626-3. doi:10.30939/ijastech. 1821778