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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

网络出版日期: 2025-09-01

基金资助

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

版权

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

甲醇是一种具有广泛应用前景的清洁可再生能源，具有低碳含量和高辛烷值，这使其非常适合应用于具有可变压缩比特性的自由活塞内燃发电机（free-piston engine generator, FPEG）上。本文通过实验和数值计算方法研究了甲醇替代率（MSR）和负载率对甲烷/甲醇双燃料FPEG性能和燃烧特性的影响。结果表明，在气-液两相燃烧启动策略下，甲烷/甲醇双燃料FPEG能够成功启动并实现稳定运行。由于甲醇具有较高的燃烧速度和氧含量，缸内峰值压力从纯甲烷的13.44 atm增加到MSR=15%的19.34 atm，增加了43.9%，相应的循环波动从3.36减小到1.62。FPEG的运行频率和指示功率随着MSR的增加而增加，当MSR=15%时，二者达到最大值，分别为34.6 Hz和193 W，与纯甲烷相比分别增加了19.3%和49.6%。在特定的MSR下，由于直线发电机的电磁阻力作用，二者均随着负载率的增加而降低。由于甲醇的掺加促进了混合物的燃烧，CO和CH排放量随着MSR的增加而减少，而由于甲醇较高的蒸发潜热降低了燃烧温度，因此氮氧化物的排放量随着MSR的增加而减少。数值仿真表明，随着MSR的增加，甲烷/甲醇混合物呈现出更快的火焰传播速度和更高的燃烧效率，而由于H，OH，O和H2O2等活性基团的增加，点火延迟以及CA10，CA50和CA90则显著缩短。

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

本文引用格式

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]. 热科学学报, 2025 , 34(5) : 1656 -1671 . DOI: 10.1007/s11630-025-2132-3

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. NOx 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

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