Experimental Study on the Impact of using Fe₂O₃ Nanoparticles on the Emissions and Performance Characteristics of a Diesel Engine

Diesel fuel finds widespread applications in many fields, including agriculture, industry, and transportation. It is used in buses, trucks, and trains, as well as for equipment in power plants-all of which are very important to the economy [1]. Combustion of diesel oil continues to have significant environmental effects. The combustion of diesel emits particulate matter and nitrogen oxides (NOx) into the atmosphere, while carbon dioxide (CO₂) emitted during combustion contributes to global warming. Development of renewable energy sources of energy is afoot, and so are setting higher standards for emissions. The path forward to sustainable development has to marry the economic importance of diesel with its serious environmental impacts [2, 3].

Rising petroleum prices, increasing air pollution, and the alarming effects of global warming have revitalized global interest in the development of alternative engine fuels. Of the many, Nano-diesels have received considerable attention, with various formulations having been tried over the years as viable alternatives to conventional petroleum-based fuels. Nano-additives in fuel are one promising solution to both environmental and energy problems. Metal oxide nanoparticles like Fe₂O₃, TiO₂, CO₃O₄, CeO₂, and Al₂O₃ were used for reducing the exhaust emissions and specific fuel consumption [4-6].

The inclusion of Nano-particles enhances the performance of the engine by increasing ($\eta$Bth) and reducing the amount of Bsfc since a high surface-to-volume ratio also lowers pollutant emissions and accelerates the rate of reactions. The accelerated combustion is a result of a shorter ignition delay compared with neat diesel [7, 8]. The combustion efficiency of diesel fuel is enhanced when Iron-oxide (Fe₂O₃) nanoparticles are combined with it, since their oxygen-rich molecular structure [9]. Enhancing combustion leads to reduced emissions of nitrogen oxides (NOx) and particulate matter compared with pure diesel engines. The added Fe₂O₃ also promotes a more homogeneous fuel–air mixture, which reduces incomplete combustion and enhances engine performance. Furthermore, the higher cetane number of these additives contributes to improving engine smooth operation and fuel efficiency [10, 11].

Nouri et al. [12] focus on the added Fe₂O₃ Nano-particles (30, 60, and 90 mg/L) to pure diesel fuel on the combustion characteristics, enactment, and emissions of diesel engines. The effects of Fe₂O₃ fuel mixtures on (Bp), $\eta$Bth, and CO₂ releases have been detected to be greater than those of neat diesel fuel blends, with increased thermal efficiency ($\eta$Bth) and power, reduced BSFC by 7.40%, 14%, and 8.2%, respectively, and decreased CO₂ releases by 21.2% compared with pure diesel fuel. Saxena et al. [13] added G and Fe₂O₃ nanoparticles to the fuel at mass amounts of 50, 100, and 150 ppm. It found indicate a positive correlation between nanoparticle dosage and the enhancement of $\eta$Bth. This improvement is likely attributed to the increased reactivity and surface area of the nanoparticles. Also, the presence of nanoparticles enhanced the thermal conductivity of the fuel. The maximum ($\eta$Bth) was enhanced by 26.1% at the highest dosage level (D150G). Ahmed et al. [14] reported that adding graphite (G) and iron oxide (Fe₂O₃) nano-particles to neat diesel can reduce the brake specific fuel consumption Bsfc of the engine. The highest reductions in Bsfc were found to be 2.6 and 2.2% at 150 mg/L for G and Fe₂O₃, respectively. The findings also reveal that raising the dosages of G and Fe₂O₃ in diesel decreases CO releases and increases NOx releases. Maximum CO reductions of 14.2 and 9.8% at 150 mg/L for G and Fe₂O₃, respectively, were reported. Besides, the maximum NOx increases were 29.2 and 34.7% at 150 mg/L of G and Fe₂O₃, respectively. This might be because, at higher velocities, the engine does not have sufficient time to accomplish the process of combustion. Zhang et al. [15] paid attention to the impact of a Fe₂O₃-based selective decrement catalyst on the emission and combustion performance of a biofuel-fueled diesel engine that was investigated. The findings demonstrated an average increase in Bsfc of 10.60, 5.35, and 5.22% for the diesel, RME, and CSME catalysts, respectively. Additionally, the use of biodiesel led to an average reduction in (CO) by 35%, (HCl) by 64%, and smoke by 45%. However, nitrogen oxide (NOx) releases increased by 11% under medium and high engine loads. Jumaa and Mashkour [16] focus on the effect of humidification of the air on the performance of CI engine operating on diesel, biodiesel with added Fe₂O₃ Nano-particles (10, 30, 50 ppm, 70, and 100 mg/L). The experiment was carried out on a single-cylinder, 4-stroke, direct injection (E6/US) diesel engine under varying loads and a constant speed of 1800 rpm. Taguchi Method by DOE was used for the optimization in this investigation. The results manifested that BTE improved by 17.62% and BSFC decreased by 12.72%, while NOx and PM reduced by 8.45%, 24.17%, respectively.

The aim of this research is to present a comprehensive analysis that explores and compares the impacts of various amounts of Fe₂O₃ with pure diesel fuel, at amounts of 25, 50, and 75 mg/L in diesel engine combustion on the emission and performance behaviors with variable speed and constant load.

In this study, iron oxide (Fe₂O₃) Nano-particles, which originated from Arej Al-Furat Office, were used to test the effect of using such particles on the performance as well as releases of a compression ignition (CI) engine. Experiments were conducted using a single-cylinder TD111 diesel engine at (1000, 1250, 1500, 1750, and 2000 rpm) speeds for a constant load condition. Three quantities (20, 50, and 75 mg/L) of each of the Nano-particles were employed to examine their effects on engine performance as well as releases.

3.1 Preparation of various fuel mixtures

The usual procedure to stabilize the fuel additives in Nano-sized particles is ultra-sonication, which helps in evenly dispersing nanoparticles in fuel, besides increasing fuel blend stability. For this study, an ultrasonic bath having a power of 240W, a frequency of 40 KHz, and a temperature (temp) of 50℃ is used to mix nanoparticles in diesel fuel for at least 30-40 minutes. A slight aggregation of nanoparticles is observed after 48 hours. Re-homogenation of fuel for testing is facilitated by further subjecting fuel to ultrasonic waves for a period of an additional 15 minutes; this is ascertained by two ways, namely, visual verification of tests and further spectroscopic verification, which is strong confirmation of the readiness of the fuel samples for tests to proceed as scheduled. During the experiments, the engine was fueled with various mixtures: pure diesel (Di+25mg/L Fe₂O₃, Di+50mg/L Fe₂O₃, and Di+75mg/L Fe₂O₃) as shown in Figure 1. The specifications of the Nano-sized and Fe₂O₃ particles are provided in Table 1.

Table 1. Features of diesel fuel mixed with nanoparticles

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Figure 1. Pure diesel, (Di +25 mg/L Fe₂O₃, Di +50 mg/L Fe₂O₃, and Di + 75 mg/L Fe₂O₃)

3.2 The features of the nanoparticles

The features of the Nano-particles utilized in this investigation are listed in Table 2. Figure 2 displays the TEM and SEM analyses, which confirm the Nano-particle sizes. Additionally, Figure 2 demonstrates the uniformity in the shape and size of the Nano-particles an important and desirable characteristic.

Table 2. Nanoparticles features utilized in the present investigation

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Figure 2. SEM and TEM analysis of Fe₂O₃ Nano-particles

3.3 Experimental setup

The experiments evaluated the various kinds of fuel influence on the performance and emissions of four-stroke diesel engines operating under flexible speed at a constant load condition. All tests have been performed at the (ICE- Lab) in the PME Techniques Department at Al-Mussaib Technical College (TCM), a branch of (ATU) in Kufa, Iraq. The experimental setup featured a single-cylinder, air-cooled diesel engine model TD111 equipped with a direct-injection system and a piston bowl combustion chamber, as shown in Figure 3. Key engine specifications are provided in Table 3. Three different fuels were tested at variable engine speeds to determine their effects on engine emissions and performance.

Table 3. Diesel engine requirements

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Figure 3. The engine test set-up

3.4 The performance characteristics

The braking power at the output shaft represents the brake power, whereas $\tau$ represents torque and N denotes engine speed in rpm [17].

$\mathrm{Bp}=\frac{2 \pi N \tau}{60}$            (1)

Brake specific consumption of fuel - Bsfc - is the quotient obtained by the division of the fuel mass flow rate ($m \dot{f}$), by the Brake Pressurization - BP [18].

$\mathrm{Bsfc}=\frac{\dot{m f}}{B p}$            (2)

The brake thermal efficiency ($\eta$_bth) itself presents the ratio of the energy in braking power to the propelling fuel energy [19].

$\eta_{\mathrm{bth}}=\frac{B P}{{m \dot{f }\times Q_{H V}}}$             (3)

This study conducted engine experiments to assess the impact of Fe₂O₃ nanoparticle additions at amounts of 25, 50, and 75 mg/L on the performance (Bp, $\eta$Bth, BSFC) and release (CO, NOx, and HC) features of a compression ignition engine. The main conclusions of this research are:

1. Fuel mixes with elevated amounts of nanoparticles in the fuel combination enhanced brake thermal efficiency and power by 17.6 and 11.4%, respectively, while reducing Bsfc by 22.8% in comparison to pure diesel fuel at 2000 rpm engine speeds.

2. Carbon monoxide emissions decreased from 1.05% to 0.9% with the addition of 75 mg/L Fe₂O₃ to pure diesel, an improvement of approximately 14.3%, at 2000 rpm.

3. Increasing the mixing amount of the Nano-particles Fe₂O₃ (25-75 mg/L) by weight, an improvement of approximately 24.9% of NOx, and 14.4%. HC releases at 2000 rpm.