|Hussein A. Mahmood||Department of Reconstruction and Projects, University of Baghdad, Iraq|
|Ali O. Al-Sulttani||Department of Water Resources Engineering, College of Engineering, University of Baghdad, Iraq|
|Naseer A. Mousa||Department of Reconstruction and Projects, University of Baghdad, Iraq|
|Osam H. Attia||Department of Reconstruction and Projects, University of Baghdad, Iraq|
understanding of the ignition characteristics of syngas-diesel under different
lambda values is essential for the application of dual-fuel combustion. In this
study, the effect of increasing the lambda value was examined along with the
emission characteristics and engine performance of syngas-diesel dual-fuel
engines under a constant syngas-to-diesel substitution ratio of 52% at 2000 rpm
engine speed. The work involved computational fluid dynamics analysis related
to combustion for a four-stroke single-cylinder direct-injection engine.
Combustion analysis was carried out using ANSYS Workbench (FLUENT) V16.1
software. According to the simulation results, the maximum pressure,
temperature, and nitric oxide emission inside
the combustion chamber increased with each increase in the value of lambda,
while the emission of carbon dioxide and carbon monoxide decreased inside the
CFD; Combustion; Emission, Lambda; Syngas-diesel dual-fuel engine
Internal combustion engines, and particularly diesel engines, have been utilized by the industrial, agricultural, and automotive sectors due to their low cost of operation, robustness, reliability, high efficiency, resilience, and robustness. Widespread use of engines that run on diesel fuel has resulted in a huge increase in demand for petroleum fuels, which will lead to their depletion. Due to the tremendous exploitation of the traditional petroleum fuels needed for obtaining diesel, it is vital that there is research on alternate fuels that minimize the need for traditional fuels and serve new application areas (Chintala & Subramanian, 2013; Dhole et al., 2014; Mahmood et al., 2017a; Mahmood et al., 2017b; Said et al., 2018; Ali et al., 2019; Wibowo et al., 2020).
In spite of the significant use conventional diesel fuels, their emissions contribute to environmental pollution. In addition, unburnt hydrocarbons, carbon monoxide (CO), nitrogen oxides (NOx), particulate matter, sulfur oxides, and soot are the main pollutants emitted by engines operating on diesel fuel, particularly in urban areas with high population density. Such pollutants have a tendency to aggravate environmental problems such as acid rain, climate change, global warming, and smoke and have a detrimental impact on human health (Re?ito?lu et al., 2015; Ibrahim et al., 2016; Alhamdany et al., 2018; Vellaiyan et al., 2018; Hamid et al., 2020).
Because of the fast depletion of fossil fuels and growing concern for the climate and human health, both engine manufacturers and researchers are being forced to look for alternatives that are reliable, low-cost, and environmentally friendly. Biomass is one of the most promising alternative energy sources that researchers in the field of internal combustion engines have recently been focusing on (Said et al., 2018; Pathak et al., 2021) and can be defined as an environmentally friendly renewable resource. The fermentation or vaporization of different types of biomass goes on to form hydrogen-rich “synthesis gas (syngas)”, which could be used as a main fuel for vehicles or as a partial substitute for traditional types of fuel (Anggraini et al., 2019; Krishnamoorthi et al., 2020). Syngas may be formed from many different raw materials through methane steam reforming, biomass fermentation, autothermal reforming of fossil fuel, ethanol steam reforming, ammonia cracking, partial methane oxidation, and other techniques. In addition, the syngas components acquired from various methods and materials can differ significantly. Carbon dioxide, hydrogen, methane, nitrogen, and carbon monoxide are the major elements of the syngas (Azimov et al., 2011; Feng, 2017; Stylianidis et al., 2017; Ali et al., 2019; Anggraini et al., 2019 ).
Two different methods have been devised for converting diesel engines for syngas, namely the syngas-dedicated and dual-fuel approaches. In the syngas-dedicated approach, ignition is achieved by (typically) using a spark plug, as in a gasoline engine, and the diesel injector is no longer used, following a suitable redesign of the engine’s combustion chamber head. Furthermore, the air intake manifold must be changed to include a syngas injector, control valve, and control unit. The conversion of the engine from diesel to syngas results in a decrease in brake power. The dual-fuel approach, however, applies syngas as the main fuel along with small quantity of diesel as a pilot fuel for ignition. With regard to this approach to conversion, the engine’s combustion chamber head is not changed due to the fact that spark plugs are also needed, while liquid fuel injection continues to be performed by an in-cylinder system of injection. Furthermore, due to the poor autoignition performance of syngas, a small amount of diesel is pumped into the engine’s cylinder to ignite it when it is used as fuel in dual-fuel engines that work under compression ignition (Mahmood et al., 2016; Mahmood et al., 2019).
According to previous literature, little research has been conducted on modifying diesel engines to work under the dual-fuel mode for enhancing fuel economy and decreasing emissions. However, the majority of studies do not take into account the effect of an increase in the lambda value on the emission characteristics and engine performance of syngas-diesel engines. As a result, published work on mixing ratios, combustion characteristics, and pollution for dual-fuel engines with various lambda values remain limited. The goal of this research is to investigate the characteristics of diesel and syngas combustion against different lambda values (1, 1.2, 1.4, and 1.6) under a constant replacement ratio of 52% at an engine speed of 2000 rpm.
this study, the emission and combustion characteristics in syngas-diesel
dual-fuel engines at different lambda values were numerically investigated
using ANSYS Workbench (FLUENT) software. The main results are outlined from the
investigation as follows: (1) At a constant replacement ratio for diesel fuel
with syngas of 52%, combustion performance improved with increased air content
in the combustion chamber. Moreover, the maximum pressure and temperature in
the combustion chamber increased with each increase in the lambda value.
Moreover, the peak pressure increased from 5,800,428.603 Pa to 6,099,471.415
Pa, 6,291,275.301 Pa, 6,708,188.479 Pa, and 6,708,188 Pa for lambda values of
1, 1.2, 1.4, and 1.6, respectively; (2) At a constant replacement ratio of 52%
for diesel fuel with syngas, increases in air content led to decreases in the
emission of carbon dioxide and carbon monoxide inside the engine, along with an
increase in nitric oxide emission. In addition, the carbon monoxide mass
fraction values inside the engine decreased from 0.012865317 to 0.009972716,
0.007938363, and 0.006670433 for lambda values of 1, 1.2, 1.4, and 1.6,
respectively. Moreover, the nitric oxide mass fraction values inside the engine
raised from 0.00554054 to 0.006849439, 0.007600012, and 0.011217929 for lambda
values of 1, 1.2, 1.4, and 1.6, respectively.
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