© IMechE 2025Ducted fuel injection (DFI) is a promising technology that can modify the combustion process in compression ignition engines to mitigate soot formation. By guiding the spray through ducts, air entrainment is enhanced, promoting a more pronounced premixed combustion phase, reducing the diffusion flame, and consequently suppressing soot generation. While previous studies using constant-volume chambers and optical research engines have demonstrated the potential of DFI and the influence of injector geometry on emissions, few have implemented this approach directly in engines due to the substantial modifications required to the cylinder head. This study proposes and evaluates an alternative DFI configuration suitable for light-duty compression ignition engines, implemented without significant modifications to the engine head. Experiments were conducted in a single-cylinder research engine using a sleeve fitted to the injector, aligning the ducts with the nozzle holes. The limited space introduces constraints such as a trade-off between duct length and stand-off distance, and a duct length shorter than the theoretical liquid penetration length. Results show that the configuration with a 3.5 mm stand-off distance achieved up to a 70% reduction in soot emissions compared to the free-spray baseline, while shorter stand-off distances (2.5 and 3.0 mm) were less effective. Although DFI delays ignition, it enhances air entrainment and premixed combustion, ultimately accelerating the combustion process.

© 2024Producer gas from biomass gasification offers a renewable alternative to fossil fuels. However, its low energy density results in low conversion efficiency in engines. Blending producer gas with higher-ranked fuels such as hydrogen has been proposed to overcome this issue. This study investigates the combustion of artificially made producer gas and hydrogen mixtures in an optical SI engine. The molar fraction of hydrogen in producer gas ranged from 14 to 62%, which simulated additions of hydrogen to a low calorific producer gas. The experiments are conducted at a constant speed and stoichiometric ratio. The spark timing is varied to achieve the highest power for each mixture. Results include data on emissions, thermodynamics, and flame morphology. The molar fraction of 33% hydrogen on producer gas improves the flame morphology of the mixture to resemble that of pure natural gas, while 24–36% was found to be the optimal range for engines initially designed to run on natural gas with lower NOx and UHC emissions.

© IMechE 2022.Thermal processes and power generation systems may employ producer gas generated through gasification as an alternative to replace natural gas with lower carbon footprint. However, pure producer gas in engines is associated with a significant power derating that can be mitigated by blending it with other biofuels. This work evaluated the effects of methane and producer gas blends on the performance of a SI engine. The additions of methane were 10%, 25% and 50% on a molar basis. The results demonstrated that adding 25% methane to producer gas is enough to sustain the combustion reaction with good stability and a power derating of 10.8%. The addition of 50% methane to producer gas attains efficiency and combustion characteristics remarkably similar to pure natural gas with a power de-rating of 5.4%. Emissions indicated that carbon monoxide (CO) has decreased with the addition of methane to producer gas from 85 to 3.43 g/kWh, while nitrogen oxides ((Formula presented.)) emissions have increased from 0 to 8.85 g/kWh. In the case of unburned hydrocarbons (UHC), emissions did not considerably change before adding 25% methane to producer gas and stayed constant at approximately 10 g/kWh. Engines designed to run on natural-gas could use this mixture without significant modifications to the combustion chamber while decreasing NOx emissions.