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<p>Growing environmental concerns and stringent emission regulations have driven interest in cleaner fuels and combustion concepts for engine applications. Biomethane is a viable solution due to its environmental and economic benefits. Advanced low-temperature combustion concepts like reactivity-controlled compression ignition (RCCI) aim to simultaneously reduce NO<sub>x</sub> and soot emissions without compromising performance. The present work investigates the achievement of RCCI combustion at low load in a dual-fuel light-duty diesel engine with biomethane surrogate, through variation of diesel injection timings. Experiments were conducted at 13.5&#xa0;N-m and 1800&#xa0;rpm in conventional diesel combustion (CDC) mode and dual-fuel mode with approximately 50% biomethane substitution. The dual-fuel mode is analysed by dividing it into conventional dual-fuel (CDF) and RCCI combustion regimes. A CFD model was developed to better understand the in-cylinder processes at chosen experimental points and compare the combustion modes. The combustion characteristics exhibited a distinct shift in the trends of peak cylinder pressure and heat release rate, with noticeable low-temperature heat release occurring beyond 30 CAD before TDC during dual-fuel combustion. A simultaneous reduction in NO<sub>x</sub> (&lt; 1&#xa0;g/kWh) and smoke (&lt; 0.01 FSN) emissions was achieved at advanced injection timings, indicating successful realization of RCCI combustion strategy. The experimental results revealed that an injection timing of 40 CAD before TDC provided the optimum engine performance and emissions. Under this condition, RCCI operation increased brake thermal efficiency from 17.3% to 18.2% compared to CDF combustion, corresponding to about 5% relative improvement. These results demonstrate the effectiveness of RCCI in achieving reductions in NO<sub>x</sub> and soot emissions without compromising engine performance. A comparative analysis using CFD simulations and bin-wise distribution plots revealed that RCCI reduces localized fuel-rich regions and high-temperature zones within the cylinder, mitigating the NO<sub>x</sub>-soot trade-off. Combustion instability quantified by COV of IMEP was found to be the limiting factor for further advance in injection timing at low load. Meanwhile, maximum pressure rise rates (MPRR) were well within limits pointing to the possibility of exploring RCCI at higher loads.</p>

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Experimental and computational evaluation of achieving RCCI combustion at low load in a dual-fuel light-duty diesel engine with biomethane surrogate

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月1日

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  • Nadeem Abdul Hameed,
  • Mayank Mittal

摘要

Growing environmental concerns and stringent emission regulations have driven interest in cleaner fuels and combustion concepts for engine applications. Biomethane is a viable solution due to its environmental and economic benefits. Advanced low-temperature combustion concepts like reactivity-controlled compression ignition (RCCI) aim to simultaneously reduce NOx and soot emissions without compromising performance. The present work investigates the achievement of RCCI combustion at low load in a dual-fuel light-duty diesel engine with biomethane surrogate, through variation of diesel injection timings. Experiments were conducted at 13.5 N-m and 1800 rpm in conventional diesel combustion (CDC) mode and dual-fuel mode with approximately 50% biomethane substitution. The dual-fuel mode is analysed by dividing it into conventional dual-fuel (CDF) and RCCI combustion regimes. A CFD model was developed to better understand the in-cylinder processes at chosen experimental points and compare the combustion modes. The combustion characteristics exhibited a distinct shift in the trends of peak cylinder pressure and heat release rate, with noticeable low-temperature heat release occurring beyond 30 CAD before TDC during dual-fuel combustion. A simultaneous reduction in NOx (< 1 g/kWh) and smoke (< 0.01 FSN) emissions was achieved at advanced injection timings, indicating successful realization of RCCI combustion strategy. The experimental results revealed that an injection timing of 40 CAD before TDC provided the optimum engine performance and emissions. Under this condition, RCCI operation increased brake thermal efficiency from 17.3% to 18.2% compared to CDF combustion, corresponding to about 5% relative improvement. These results demonstrate the effectiveness of RCCI in achieving reductions in NOx and soot emissions without compromising engine performance. A comparative analysis using CFD simulations and bin-wise distribution plots revealed that RCCI reduces localized fuel-rich regions and high-temperature zones within the cylinder, mitigating the NOx-soot trade-off. Combustion instability quantified by COV of IMEP was found to be the limiting factor for further advance in injection timing at low load. Meanwhile, maximum pressure rise rates (MPRR) were well within limits pointing to the possibility of exploring RCCI at higher loads.