Case Study for Ethanol Blending
Performance, combustion and emission characteristics investigations on a diesel engine fueled with diesel/ ethanol /n-butanol blends
Abstract
In this study, a three-dimensional computational fluid dynamics (CFD) model of a diesel engine cylinder was developed by AVL-Fire software, and a chemical reaction mechanism containing 377 reactions and 81 species was established by the CHEMKIN program. The purpose of this work is to investigate the effect of diesel/ethanol/n-butanol blends on combustion and emission characteristics such as in-cylinder pressure, in-cylinder temperature, brake power, brake thermal efficiency, brake specific fuel consumption, NOx emission, CO emission and soot emission. The results showed that the diesel/ethanol/n-butanol blended fuels reduced the brake power and increased the brake specific fuel consumption of the diesel engine, but improved the brake thermal efficiency. In addition, the blend fuels reduced nitrogen oxides, carbon monoxide, and soot emissions. At 100% load, when the diesel engine fueled with E5N13, E10N5, E10N18, E15N10, E15N18, and E20N10, the brake thermal efficiencies were increased by 2.72%, 2.69%, 4.52%, 4.49%, 5.565%, and 5.53% respectively. However, the brake specific fuel consumption increased by 2.79%–5.84%, and the brake power decreased by 2.76%–5.59%. At 50% load, blended fuels with different mixture ratios reduced nitrogen oxides by 8.39%–21.81%, carbon monoxide by 12.1%–22.91%, and soot by 26.71%–48.59% compared to diesel. This is influenced by a combination of higher oxygen content, lower cetane number and calorific value of ethanol and n-butanol.
Introduction
With the rapid development and progress of society, the number of motor vehicles worldwide is increasing [1]. The diesel engine is widely used in automobiles, transportation, industry, and agriculture due to its excellent fuel economy and durability [2]. Diesel engines have become the primary power source for ships, trucks, and other large machinery equipments, accounting for over 80% of the global transport industry [3]. On the other hand, as the primary fuel source of engines, the consumption of fossil fuels is also increasing [4]. For example, the fuel consumption of internal combustion engines in China had reached 455 million tons in 2020. Fossil fuels are non-renewable energy sources, and their massive use will lead to an energy crisis [5]. More importantly, the massive burning of fossil fuels has caused severe environmental pollution [6], aggravating environmental crises and causing severe harm to human health [7,8]. The combustion products of fossil fuels, such as carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), and particulate matter (PM), are considered to be the main contributors to global climate change [9,10]. Therefore, looking for clean energy and controlling the emission of exhaust pollutants has always been an area of great concern to the public [11].
In order to control the emission of vehicle exhaust pollutants, the control laws and regulations of engine exhaust emissions are becoming increasingly strict all over the world [12]. The national VI emission regulations for heavy-duty diesel vehicles in China require that the standard steady-state engine cycle CO emission shall not exceed 1500 mg/kW·h, NOx emission shall not exceed 400 mg/kWh. In addition, the latest European Union (EU) VII emission standard requires that the NOx emission shall not exceed 30 mg/km and the CO emission shall not exceed 300 mg/km. Therefore, a series of problems such as global climate change and the energy crisis have aroused people's interest in researching clean and renewable fuels [13]. The search for clean and renewable fuels is significant to alleviate the energy crisis and protect the environment [14].
For diesel engines, the currently available alternative fuels include biodiesel, methanol, ethanol and n-butanol etc. [15,16]. With the advantages of renewable and environment-friendly, these alternative fuels can cope well with the energy crisis and environmental crisis challenges [17], which have attracted widespread attention worldwide and received strong support from governments [18]. For example, the EU Advisory Committee on Biofuels Research recommends that the share of biofuels used for transportation fuel consumption must increase to 25% by 2030. According to the US Energy Independence and Security Act, the use of renewable fuels in transportation needs to increase to 36 billion gallons by 2022. China's National Energy Administration announced that ethanol and biodiesel production would reach 4 million tons and 2 million tons, respectively, by 2020.
Alcohol fuels are renewable energy sources [19]. The partial replacement of diesel fuel with methanol, ethanol, and butanol has been proven to improve engine combustion characteristics [20], improve engine performance [21] and reduce exhaust pollutant emissions [22]. Yan et al. [23] studied the spray and combustion characteristics of diesel engine fueled with butanol-diesel and ethanol-diesel at high altitudes. The results showed that both butanol and hexanol blended with diesel reduced soot emission. Chen et al. [24] had studied the combustion and emission characteristics of dual-fuel engine fueled with diesel-methanol, diesel/ethanol, and diesel/n-butanol. The results showed that incorporating methanol, ethanol, and n-butanol into diesel fuels prolonged the ignition delay period and reduced the emission of inhalable particulate matter. Tian et al. [25] studied the effect of n-butanol/diesel composite fuel on light-duty diesel engine emissions. The results showed that as the content of n-butanol in the blended fuel increased, NOx and soot emissions decreased, and hydrocarbons (HC) and CO emissions increased.
Kurre et al. [26] investigated the performance and emission characteristics of diesel engine fueled with diesel/ethanol blends. The results showed that with the increase of ethanol content, the brake thermal efficiency (BTE) decreased slightly, and the brake specific fuel consumption (BSFC) and exhaust temperature increased. In addition, the emissions of NOx, CO2, HC, and CO decreased with increasing ethanol content in the fuel blend, and soot emissions drop sharply. Armas et al. [27] studied the effects of diesel/ethanol and diesel/methanol blended fuels on engine emissions. The results showed that the emissions of NOx and total hydrocarbons (THC) increased, and the CO emission decreased. Padala et al. [28] studied the effect of diesel blended with ethanol on engine performance. The results showed that the increased ethanol content in the blended fuel improved engine efficiency. But the emissions of unburned hydrocarbons, CO, and NOx increased with the ethanol content.
Tipanluisa et al. [29] studied the effect of n-butanol/diesel blended fuels on the performance and emission characteristics of heavy-duty diesel engine. The results showed that the engine had better performance when 10% n-butanol was blended with diesel. Sahin et al. [30] studied the effect of n-butanol/diesel on engine performance and emission characteristics. The results showed that 2% and 4% n-butanol in the blended fuel reduced NOx emission. Lapuerta et al. [31] studied the effect of n-butanol blended fuels on Euro VI diesel engine. The results showed that diesel/n-butanol blended fuels increased the emissions of CO and THC, while had little effect on NOx emission. Nayyar et al. [32] studied the combustion and emission characteristics of an n-butanol/diesel engine. The results showed that compared with diesel, the 20% n-butanol/diesel blend reduced soot, NOx, and CO emissions by 56.52%, 17.19%, and 30.43%, respectively. Siwale et al. [33] studied the combustion and emission characteristics of n-butanol/diesel blended fuel engine. The results showed that n-butanol in n-butanol/diesel fuel reduced CO and soot emissions but increased NOx emission.
In summary, the addition of an appropriate percentage of ethanol or n-butanol to the fuel blend can improve the combustion and emission characteristics of the engine compared to diesel. However, the disadvantage of poor mutual solubility of ethanol and diesel fuel limits its application in practice. Therefore, n-butanol can be used as a co-solvent to promote the mutual solubility of diesel and ethanol. In addition, researchers are currently studying more binary blends such as diesel/ethanol and diesel/n-butanol, but less ternary blends such as diesel/ethanol/n-butanol. Therefore, this paper selects diesel/ethanol/n-butanol ternary blends as the research object with certain research significance. In addition, the combustion of diesel engines is a complex process that is both time consuming and expensive [34]. The use of numerical simulation software for modeling and simulation can both reduce research costs and save computational time [35], which is increasingly favored by researchers and has been widely used [36]. Therefore, in this study, the effect of diesel ethanol n-butanol fuel blends with different blending ratios on the combustion and emission characteristics of the engine was studied by modeling and simulating the engine cylinders with AVL-Fire software.
In this study, a three-dimensional CFD model of the engine cylinder was developed by AVL-Fire software combined with CHEMKIN program. The purpose was to study the effects of diesel/ethanol/n-butanol fuel blends with different blend ratios on the combustion and emission characteristics of the engine. Firstly, the accuracy of the model was verified based on the experimental results under different operating conditions. Secondly, the combustion processes of blended fuels including diesel (D100), E5N13, E10N5, E10N18, E15N10, E15N18 and E20N10 were simulated and compared with a chemical reaction mechanism containing 377 reactions and 81 species. The effects of diesel/ethanol/n-butanol fuels with different blending ratios on engine combustion and emission characteristics were also analyzed and studied. This finding is of interest because the use of diesel/ethanol/n-butanol blended fuels can both prevent performance loss and reduce emissions.
Section snippets
Basic conservation equations
The CFD simulation calculation follows the law of conservation of mass, the law of conservation of momentum, and the law of conservation of energy. Then the relationship between the physical quantities of the flow field in the cylinder over time is obtained. The basic conservation law equation is as follows:
Results and discussion
The simulation considered four loads of 25%, 50%, 75%, and 100% combined with seven blended fuels of D100, E5N13, E10N5, E10N18, E15N10, E15N18, and E20N10. The effects of different blended fuels proportions on diesel engines' combustion and emission characteristics were investigated in terms of brake power, BSFC, BTE, cylinder pressure, cylinder temperature, NOx emission, CO emission, and soot emission.
Conclusions
With the increasing environmental crisis [[49], [50], [51], [52]] and energy crisis [[53], [54], [55], [56], [57], [58]], it is a very important task to improve the performance of diesel engines [59] and reduce the emission of polluting gases from diesel engines [60]. Therefore, the development and use of diesel alternative fuel is inevitable [[61], [62], [63], [64]]. Thus, in this work, a 3D-CFD model of the engine cylinder was established in the AVL-Fire environment, and the engine was
Credit author statement
Zhiqing Zhang: Method, Funding acquisition, Conceptualization, Writing – review & editing; Jiangtao Li: Resources, Project administration, Method, Software, Data curation, Writing – original draft, Writing – review & editing; Jie Tian: Data curation, Writing – review & editing; Rui Dong: Software, Formal analysis, Investigation, Method; Zhi Zou: Project administration, Writing – review & editing; Sheng Gao: Investigation Method, Project administration, Formal analysis; Dongli Tan:
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work is supported by the Natural Science Foundation of Guangxi under the research grant 2018GXNSFAA281267 and 2018GXNSFAA294072; This research is supported by the Guangxi University of Science and Technology Doctoral Fund under the research grants of 20Z22, 20S04 and 21Z34; This research is supported by the Innovation Project of Guangxi Graduate Education under the research grants of YCSW2022440
References (64)
D. Zhou et al.
Appl Energy
(2018)
H. Wang et al.
Energy Pol
(2017)
Z. Zhang et al.
Fuel
(2021)
X. Ou et al.
Appl Energy
(2012)
J. E et al.
Renew Sustain Energy Rev
(2017)
T. Peng et al.
Appl Energy
(2018)
T. Wu et al.
Energy
(2018)
D. Zhao et al.
A review of cavity-based trapped vortex, ultra-compact, high-g, inter-turbine combustors
Prog Energy Combust Sci
(2018)
T. Cai et al.
Chem Eng J
(2021)
T. Cai et al.
Fuel
(2020)
Z. Zhang et al.
Fuel
(2022)
Z. Huang et al.
Fuel
(2022)
J. E et al.
Energy Convers Manag
(2018)
M. Nour et al.
Fuel Process Technol
(2017)
W. Zhao et al.
Fuel
(2022)
Q. Ma et al.
The performance and emissions characteristics of diesel/biodiesel/alcohol blends in a diesel engine
Energy Rep
(2021)
L. Fan et al.
Tetrahedron Lett
(2021)
J. Yan et al.
Fuel
(2022)
Z. Chen et al.
Fuel
(2021)
O. Armas et al.
Pollutant emissions from New European Driving Cycle with ethanol and butanol diesel blends
Fuel Process Technol
(2014)
S. Padala et al.
Ethanol utilisation in a diesel engine using dual-fuelling technology
Fuel
(2013)
L. Tipanluisa et al.
Fuel
(2021)
Z. Şahin et al.
Renew Energy
(2015)
L. Siwale et al.
Fuel
(2013)
Q. Peng et al.
Appl Energy
(2021)
V. Karthickeyan et al.
Fuel
(2019)
J. Sun et al.
Oxides of nitrogen emissions from biodiesel-fuelled diesel engines
Prog Energy Combust Sci
(2010)
X. Jiang et al.
Prog Energy Combust Sci
(2010)
Z. Zhang et al.
Appl Therm Eng
(2020)
A. Datta et al.
Appl Therm Eng
(2016)
T. Balamurugan et al.
Energy
(2014)
M. Yao et al.
Fuel
(2010)
There are more references available in the full text version of this article.
