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HỘI THẢO QUỐC TẾ ATiGB LẦN THỨ CHÍN - The 9 ATiGB 2024 175

EXPERIMENTAL ADJUSTMENT

OF THE BIOGAS - HYDROGEN FUEL SUPPLY

PROCESS FOR A SPARK IGNITION ENGINE

Bui Van Hung*, Nguyen Minh Tien, Ho Tran Ngoc Anh, Le Anh Van
University of Technology and Education, the University of Da Nang
*bvhung@ute.udn.vn
Abstract: The main task of the fuel supply system is to decreases as the hydrogen content in the biogas mixture
maintain the equivalence ratio of the mixture close to the increases. The equivalence ratio is determined based on the
theoretical value for complete combustion. Current air-fuel fuel flow rate and the airflow rate supplied to the engine.
ratio control systems are typically applied to traditional The amount of air supplied to the engine depends on the
fuels. However, for renewable gaseous fuels such as biogas- throttle opening and speed. For stationary engines, the
hydrogen, the fuel supply system requires special attention. engine speed only varies within a narrow range, allowing us
When the composition of the biogas-hydrogen fuel changes, to simplify the influence of engine speed when determining
the equivalence ratio also changes to ensure the engine the airflow and fuel flow rates.
achieves the highest indicated mean effective pressure and Keywords: Renewable fuels; biogas-hydrogen; Gas
the lowest pollutant emissions. The equivalence ratio engine; Net Zero.
Symbol studied the combustion efficiency of the
TK Degrees according to crankshaft angle hydrogen/biogas mixture in a spark-ignition engine
TDC Top dead center through simulation and found that increasing the
p Pressure (bar) hydrogen content in the fuel mixture increases both
n Engine speed (rpm) peak pressure and the maximum heat release rate.
MxCy Biogas is composed of 10x% CH 4 and 10y% CO 2 Porpatham et al. [10] observed similar results when
by volume.
MxCy-zH Biogas is composed of 10x% CH 4 and 10y% CO 2 studying a spark-ignition engine running on biogas
and z% H 2 by volume enriched with 5%, 10%, and 15% hydrogen at various
 Equivalence factor equivalence ratios. Silvana Di Iorio et al. [11] studied
 Crankshaft angle the combustion process of a hydrogen-methane
 Throttle angle from 0° (fully open) to 60° mixture in a small spark-ignition engine using high-
(fully closed) speed digital filming and found that peak pressure
1. INTRODUCTION increased, approaching TDC, and combustion time
decreased as the hydrogen content in the fuel mixture
One of the fundamental properties of fuel that
affects engine performance is the flammability limit increased.
and the basic combustion speed [1]. Biogas contains Regarding pollutant emissions, engines running on
50-70% methane, 30-50% carbon dioxide, and a small biogas exhibit low levels of pollutant emissions [12].
amount of other impurities [2-3]. Many studies have Engines running on hydrogen generally have even
shown that impurities have a significant impact on the lower pollutant emissions than engines using traditional
combustion process of fuel. The results indicate that or alternative fuels [13]. When hydrogen is mixed into
impurities reduce the quality of the combustion biogas, the level of NOx emissions depends on the
process. CO2 in biogas narrows the flammability limit hydrogen content. With an appropriate hydrogen
and reduces the flame propagation speed [4-6]. content, NOx decreases, but when the hydrogen
Recent studies show that the biogas-air mixture can content is high, NOx increases due to the increased
only ignite when the CO2 content in biogas is less combustion temperature [14-15]. NOx emissions have a
than 62.5% by volume [7]. strong correlation with peak cylinder pressure - the
higher the peak pressure, the greater the NOx
When the hydrogen content mixed into biogas is
altered, the combustion characteristics of the engine emissions [16]. When the engine operates at a
improve. Ilbas et al. [8] found that increasing the stoichiometric ratio (φ=1), with an appropriate
hydrogen content in the mixture with methane hydrogen content, the engine's economic, technical
increases the flame propagation speed and extends the performance, and pollutant emission levels improve.
flammability limit. This shortens the time from However, when the hydrogen content exceeds 10%, the
ignition to peak pressure, bringing the peak pressure amount of heat transferred to the cooling water
point closer to top dead center (TDC), thereby increases, reducing thermal efficiency while NOx
increasing the heat release rate. Chung et al. [9] emissions increase [17]. When the engine operates with
ISBN: 978-604-80-9779-0