Experimental study of the methane and producer gas blends in an optical spark ignition engine: Combustion characteristics, thermodynamics and emissions

Abstract

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: see text]) 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.

Combustion Diagnosis in a Spark-Ignition Engine Fueled with Syngas at Different CO/H2 and Diluent Ratios

“…Optically accessible engines provide results that can be used to benefit both endeavors, thereby enabling the development of advanced solutions for the optimization of engines, such as the ones developed by Irimesco [19] or Merola et al [20], which can be applied in the development of more efficient commercial engines. The authors of this work have shown in recent studies that the addition of methane to syngas will favor the stability of the flame and the conversion efficiency [15], while the addition of hydrogen will improve not only the flame stability but also its emissions [16,21,22]. The addition of hydrogen to syngas also improves the propagation stability of lean operation [21].…”

“…Since the specific energy of syngas is lower than conventional fossil fuels, consequently, the engine's output will be relatively low when syngas is used to feed it [9,13]. To overcome this issue, some methodologies can be applied, such as using superchargers, increasing the compression ratio [9,14], or blending the syngas with other higher-ranked fuels, such as methane [15], hydrogen [16,17], or others [18]. Currently, the primary focus of research on syngas-powered engines is centered around optimizing the engines to the fullest potential and enhancing numerical models [14].…”