Experimental and Numerical Investigation on Performance and Combustion Characteristics of a Free-Piston Engine Generator Fueled with Methane/Methanol

HUANG Fujun; GUO Shuman; WANG Lijun; KONG Wenjun

doi:10.1007/s11630-025-2132-3

2025 , Vol. 34 >Issue 5: 1656 - 1671

DOI: https://doi.org/10.1007/s11630-025-2132-3

Experimental and Numerical Investigation on Performance and Combustion Characteristics of a Free-Piston Engine Generator Fueled with Methane/Methanol

HUANG Fujun ,
GUO Shuman ,
WANG Lijun ,
KONG Wenjun

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1. School of Mechanics, North China University of Water Resources and Electric Power, Henan 450045, China
2. Henan International Joint Laboratory of Thermo-Fluid Electro-Chemical System for New Energy Vehicle, Henan 450045, China
3. School of Astronautics, Beihang University, Beijing 102206, China

Online published: 2025-09-01

Supported by

This work was supported by the Space Application System of China Manned Space Program.

Copyright

Science Press, Institute of Engineering Thermophysics, CAS and Springer-Verlag GmbH Germany, part of Springer Nature 2025

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Abstract

Methanol is a very promising clean alternative fuel with low carbon content and high octane number, and this makes it well suited to the free-piston engine generator (FPEG) with variable compression ratio characteristics. To the authors’ knowledge there are no relevant studies on the application of methanol for FPEG in recent literatures. In this paper, the effects of methanol substitution ratios (MSR) and load ratios on the performances and combustion characteristics of a methane/methanol dual-fuel FPEG have been investigated experimentally and numerically. The results show that the under the gas-liquid two-phase combustion startup strategy, the methane/methanol dual-fuel FPEG can be successfully started and achieve steady operation. Due to higher laminar flame speed (LFS) and the oxygen content of methanol resulting in a faster burning rate, the peak pressure increases by 43.9% from 1.344 MPa for pure methane to 1.934 MPa for 15% of MSR and the corresponding cycle-to-cycle variation decreases from 3.36 to 1.62. The FPEG operating frequency and indicated power gradually increase with the increase of the MSR. Both of them reach maximum values of 34.6 Hz and 193 W at 15% of MSR, which are increased by 19.3% and 49.6% in comparison with the pure methane. However, under specific MSR, both of them decrease with the load ratio increasing because of the large electromagnetic resistance force from the linear generator. CO and CH emissions decrease with the increase of MSR because methanol addition promotes complete combustion of mixture. NO_x emissions gradually decrease with MSR increasing owing to the low combustion temperature resulting from the high latent heat of methanol evaporation. The numerical results show that with the increase of MSR, the methane/methanol mixture presents faster flame propagation speed and higher combustion efficiency; while the ignition delay as well as CA10, CA50 and CA90 is significantly shortened due to the increase of active radicals such as H, OH, O and H₂O₂.

Key words： free-piston linear engine generator; gas-liquid two-phase combustion startup strategy; cycle-to-cycle variation; active radicals

Cite this article

HUANG Fujun , GUO Shuman , WANG Lijun , KONG Wenjun . Experimental and Numerical Investigation on Performance and Combustion Characteristics of a Free-Piston Engine Generator Fueled with Methane/Methanol[J]. Journal of Thermal Science, 2025 , 34(5) : 1656 -1671 . DOI: 10.1007/s11630-025-2132-3

References

[1] Zhang W.K., Kong W.J., Sui C.J., et al., Effect of hydrogen-rich fuels on turbulent combustion of advanced gas turbine. Journal of Thermal Science, 2022, 31: 561–570.
[2] Huang F.J., Kong W.J., Experimental investigation of operating characteristics and thermal balance of a miniature free-piston linear engine. Applied Thermal Engineering, 2020, 178: 115608.
[3] Huang F.J., Kong W.J., Experimental study on the operating characteristics of a reciprocating free piston linear engine. Applied Thermal Engineering, 2019, 161: 114131.
[4] Mishra M.P., Assessment of performance, combustion and emissions characteristics of methanol-diesel dual-fuel compression ignition engine: A review. Journal of Traffic and Transportation Engineering (English Edition), 2021, 8(5): 638–680.
[5] Chen Z.M., Wang L., Yuan X.A., et al., Experimental investigation on performance and combustion characteristics of spark-ignition dual-fuel engine fueled with methanol/natural gas. Applied Thermal Engineering, 2019, 150: 164–174.
[6] Zhen X.D., Li X.Y., Wang Y., et al., Effects of the initial flame kernel radius and EGR rate on the performance, combustion and emission of high-compression spark-ignition methanol engine. Fuel, 2020, 262: 116633.
[7] Zhang M.M., Hong W., Xie F.X., et al., Effects of diluents on cycle-by-cycle variations in a spark ignition engine fueled with methanol. Energy, 2019, 182: 1132–1140.
[8] Ming Z.Y., Liu B., Zhang X., et al., Study of methanol spray flame structure and combustion stability mechanisms by optical phenomenology and chemical kinetics. Fuel Processing Technology, 2023, 252: 107947.
[9] Li L.P., Wei J.N., Liu H.F., et al., The exergy analysis of low carbon or carbon free fuels: Methane, methanol and hydrogen under engine like conditions. Fuel Processing Technology, 2023, 252: 107975.
[10] Liu H.F., Zhang X.T., Zhang Z., et al., Experimental and numerical study on the performances of a free-piston engine generator using ammonia and methane fuel mixtures. Fuel, 2023, 341: 127684.
[11] Liu H.F., Ampah J.D., Zhao Y., et al., A perspective on the overarching role of hydrogen, ammonia, and methanol carbon-neutral fuels towards net zero emission in the next three decades. Energies, 2023, 16(1): 280.
[12] Verhelst S., Turner J., Sileghem L., et al., Methanol as a fuel for internal combustion engines. Progress in Energy and Combustion Science, 2019, 70: 43–88.
[13] Awad O.I., Mamat R., Ibrahim T.K., et al., Overview of the oxygenated fuels in spark ignition engine: environmental and performance. Renewable and Sustainable Energy Reviews, 2018, 91: 394–408.
[14] Awad O.I., Mamat R., Ali O.M., et al., Alcohol and ether as alternative fuels in spark ignition engine: a review. Renewable and Sustainable Energy Reviews, 2018, 82: 2586–2605.
[15] Chen Z.M., He J.J., Chen H., et al., Comparative study on the combustion and emissions of dual-fuel common rail engines fueled with diesel/methanol, diesel/ethanol, and diesel/n-butanol. Fuel, 2021, 304: 121360.
[16] Panda K., Ramesh A., Diesel injection strategies for reducing emissions and enhancing the performance of a methanol based dual fuel stationary engine. Fuel, 2021, 289: 119809.
[17] Canakci M., Ozsezen A.N., Alptekin E., et al., Impact of alcohol-gasoline fuel blends on the exhaust emission of an SI engine. Renew Energy, 2013, 52: 111–117.
[18] Prasad B.N., Pandey J.K., Kumar G.N., Effect of hydrogen enrichment on performance, combustion, and emission of a methanol fueled SI engine. International Journal of Hydrogen Energy, 2021, 46(49): 25294–25307.
[19] Chen Z.M., Wang L., Zhang Q.G., et al., Effects of spark timing and methanol addition on combustion characteristics and emissions of dual-fuel engine fuelled with natural gas and methanol under lean-burn condition. Energy Conversion and Management, 2019, 181: 519–527.
[20] Du N., Kong W.J., Experimental and numerical studies of a microscale internal combustion swing engine (MICSE). Journal of Thermal Science, 2021, 30: 1705–1717.
[21] Huang F.J., Xiao H.H., Guo S.M., et al., Effect of disturbances on the operation process of a methane-fueled free-piston engine generator. Journal of Thermal Science, 2023, 32: 881–896.
[22] Nandkumar S., Two-stroke linear engine. West Virginia University, Morgantown, USA, 1998.
[23] Jia B.R., Tian G.H., Feng H.H., et al., An experimental investigation into the starting process of free-piston engine generator. Applied Energy, 2015, 157: 798–804.
[24] Woo Y., Lee Y., Lee Y., The performance characteristics of a hydrogen-fuelled free piston internal combustion engine and linear generator system. International Journal of Low-Carbon Technologies, 2009, 4(1): 36–41.
[25] Huang F.J., Kong W.J., Effect of hydrogen addition on the operating characteristics of a free piston linear engine. International Journal of Hydrogen Energy, 2020, 45(30): 15402–15413.
[26] Huang F.J., Kong W.J., Effects of hydrogen addition on combustion characteristics of a free-piston linear engine with glow-assisted ignition. International Journal of Hydrogen Energy, 2021, 46(44): 23040–23052.
[27] Huang F.J., Guo S.M., Wang L.J., et al., Experimental and numerical study on the performances of a free-piston engine generator using ammonia and methane fuel mixtures. Fuel, 2023, 341: 127654.
[28] Pichler C.S., Nilsson E.J.K., Reduced kinetic mechanism for methanol combustion in spark-ignition engines. Energy & Fuel, 2018, 32(12): 12805–12813.
[29] Chen Z., Yang F., Xue S., et al., Impact of higher n-butanol addition on combustion and performance of GDI engine in stoichiometric combustion. Energy Conversion and Management, 2015, 106: 385–392.
[30] Li Y., Gong J.K., Deng Y.W., et al., Experimental comparative study on combustion, performance and emissions characteristics of methanol, ethanol and butanol in a spark ignition engine. Applied Thermal Engineering, 2017, 115: 53–63.
[31] Eng J.A., Characterization of pressure waves in HCCI combustion. SAE Technical Paper, 2002, 2002-01-2859.
[32] Sjöberg M., Dec J.E., Babajimopoulos A., et al., Comparing enhanced natural thermal stratification against retarded combustion phasing for smoothing of HCCI heat release rates. SAE Technical Paper, 2004: 2004-01-2994.
[33] Jarquin-Lopez G., Polupan G., Toledo-Velazquez M., et al., Analytical and experimental research for decreasing nitrogen oxides emissions. Applied Thermal Engineering, 2009, 29(8–9): 1614–1621.

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