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Article

Comparison of the Engine Performance of Soybean Oil Biodiesel Emulsions Prepared by Phase Inversion Temperature and Mechanical Homogenization Methods

by
Cherng-Yuan Lin
* and
Keng-Hung Lin
Department of Marine Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan
*
Author to whom correspondence should be addressed.
Processes 2023, 11(3), 907; https://doi.org/10.3390/pr11030907
Submission received: 12 February 2023 / Revised: 13 March 2023 / Accepted: 14 March 2023 / Published: 16 March 2023
(This article belongs to the Section Environmental and Green Processes)
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Abstract

:
The engine performance and emission characteristics of burning emulsions of soybean oil biodiesel in a compression-ignition diesel engine prepared through the phase inversion temperature method were compared with those of neat soybean oil biodiesel and the emulsion prepared by the mechanical homogenization method. The engine torque was set constantly at 98 N·m with varying engine speeds. The experimental results show that the emulsion prepared by the method of phase inversion temperature had higher O2 and NOx emissions, a higher excess air ratio, a higher exhaust gas temperature, and a higher brake fuel conversion efficiency than the emulsion prepared by the mechanical homogenization method, which had lower CO and CO2 emissions, a lower equivalence ratio, and lower brake-specific fuel consumption. While the neat soybean oil biodiesel was found to have the lowest fuel consumption rate, brake-specific fuel consumption, and CO and CO2 emissions, it had the highest exhaust gas temperature and brake fuel conversion efficiency, NOx and O2 emissions, and excess air ratio among those three fuels. Therefore, the phase inversion temperature method is considered promising for preparing fuel emulsions as an alternative to petro-derived diesel for compression-ignition engines.

1. Introduction

Emulsions, in which two or more immiscible phases are mixed together for a period of time, are widely applied to the engine fuel, pharmaceutical, and chemical industries [1,2]. Two-phase emulsions generally include oil-in-water (O/W) or water-in-oil (W/O) types. W/O emulsion fuel has been successfully used to increase combustion efficiency and reduce fuel consumption due to the occurrence of micro-explosion phenomenon when water droplets of relatively lower boiling point are evaporated to explode through the enveloping continuous oil phase [3].
Due to global acute climate change arising partially from burning fossil fuel, biodiesel made from vegetable oils or lignocellulose feedstocks has been used as an alternative to petro-derived diesel to alleviate the emission of greenhouse gases [4]. Various emulsification methods have been developed to produce emulsions of different types. Dispersion and condensation methods, which are regarded as high- and low-energy methods, are generally used to prepare emulsions. Among these methods, the phase inversion temperature (PIT) which is a low-energy method which requires much less energy consumption and simpler equipment than high-energy methods, such as mechanical homogenization or microwave irradiation [5,6], which produce much more disruptive forces to reduce the droplet sizes of the emulsions [7]. The low-energy emulsification method is considered more cost-efficient because the formed droplet sizes are not affected by the external energy acted on the emulsion mixture [8]. The physicochemical properties of the surfactant, oil, and water phases are the decisive factors for producing an emulsion with small, dispersed droplet sizes [9]. In addition, high yield and low processing time are also the advantages of the low-energy emulsification methods [10]. The emulsification method of phase inversion temperature is applied to the emulsion system with a polyoxyethylene-type nonionic surfactant whose hydrophilic-lipophilic properties are sensitive to temperature change [11]. The temperature change of the emulsion system results in the hydration of the polyoxyethylene chains. Moreover, such surfactants possess a large positive spontaneous curvature at low a temperature and become negative reverse structures at high temperatures [12]. The temperature of phase inversion is also called the temperature of hydrophilic–lipophilic balance (HLB) [13]. This is ascribed to the phenomenon when the O/W emulsion is heated from the atmospheric temperature to its corresponding PIT during emulsification processes. Subsequent to this occurrence, the electrical conductance of the emulsion decreases sharply, and the emulsion is turned into a W/O emulsion [14]. Through this, the hydrophilic and lipophilic characteristics of the surfactant would be completely balanced.
Emulsion fuel has been used in internal combustion engines to improve engine power output and reduce toxic pollutant emissions. Ettefaghi et al. [15] found that diesel emulsion decreases brake-specific fuel consumption by 1~8%, exhaust gas temperature, NOx emission, and black smoke. The occurrence of micro-explosions during the burning of emulsion fuel [16] causes second-atomization of the injected liquid fuel, resulting in a more violent mixing between fuel droplets and surrounding air and a reduction in the stoichiometric air-to-fuel mass ratio. Meanwhile, the existence of water in the emulsion facilitates the water–gas shift reaction to further burn carbon monoxide (CO) and unburned hydrocarbons (UHC) to produce complete combustion products of H2O and CO2 [17]. The combustion efficiency can therefore be enhanced together with toxic pollutant mitigation.
Vegetable oils, such as soybean oil, rapeseed oil, and palm oil, are not suitable to be used directly in an internal combustion engine mainly due to their high viscosity and carbon deposits, which results in abnormal operation of the engine [18]. Biodiesel is composed of mono-alkyl esters of long-chain fatty acids, also termed fatty acid methyl esters (FAME) or fatty acid ethyl esters (FAEE). The manufacture of vegetable oils to biodiesel primarily through transesterification reactions with short-chain alcohols such as methanol by virtue of nucleophilic substitution can improve their combustion characteristics, with them nearly comparable to those of diesel fuel. The major compounds of soybean oil biodiesel include palmitic acid (C16:0), oleic acid (C18:1), and linoleic acid (C18:2), whose carbon numbers are similar to those of petro-derived diesel [19]. Biodiesel, which can emit much less CO2, black smoke, sulfur oxides (SOx), and no carcinogenic polycyclic aromatic hydrocarbons (PAHs), is considered an environmentally friendly alternative to petro-derived fuel [20]. However, biodiesel generally possesses significant disadvantages of inferior low-temperature fluidity, higher kinematic viscosity, and lower heating value in comparison with those of diesel fuel. For the formation of biodiesel emulsion, adding adequate antifreeze or heating the biodiesel might improve those fuel characteristics.
The emulsion of soybean oil biodiesel can be an excellent alternative to diesel fuel in improving burning efficiency and reducing toxic emissions. Elumalai et al. [21] found that the emulsion of Nerium oil biodiesel appeared to have higher brake thermal efficiency by 13.72% than neat diesel. The emissions of carbon monoxide, nitrogen oxides, and unburned hydrocarbons were also reduced by 42.87%, 6.5%, and 31.94%, respectively. They considered that the availability of the oxygen content in biodiesel and the occurrence of micro-explosions during emulsion burning were responsible for those results. The application of emulsified biodiesel in diesel engines without any engine modification improves engine performance and reduces engine emissions. The application of adequate emulsifying approaches [22], reducing dispersed droplet sizes, adding stabilizers such as plant polysaccharides or antioxidants [23], processing with some stabilizing reactions on the emulsion system such as glycosylation [24], and keeping emulsions in a low-temperature environment [25], etc., are considered effective to improve the emulsification stability for even more than several months. Studies on the engine characteristics of the emulsion of soybean oil biodiesel prepared by the phase inversion temperature method remain unavailable in the literature. In this study, the soybean oil biodiesel was emulsified by phase inversion temperature and mechanically emulsifying methods. The successful development of biodiesel emulsion would serve to reduce carbon dioxide emissions from diesel engines and mitigate the threat of global climate change. The application potential of using the phase inversion temperature which is a low-energy emulsification method for preparing biodiesel emulsion as a clean, environmentally friendly alternative fuel to petro-derived diesel is systematically evaluated in this study. The properties of the biodiesel emulsion prepared by the low-energy emulsification method such as the phase inversion temperature were investigated as well. The emission characteristics and engine performance of the emulsions by the two different emulsification methods and neat soybean oil biodiesel were analyzed and compared based on their engine characteristics. Additionally, the effects of emulsion structure and properties on the combustion characteristics of the engine were investigated.

2. Experimental Details

2.1. Experimental Materials

The soybean oil, provided by Formosa Oilseed Processing Co., Ltd. (Taichung City, Taiwan), was refined from raw pressed soybean oil. The specific gravity, acid value, peroxide value, and kinematic viscosity were 0.922, 0.07 mg KOH/g oil, 0.21 meq/kg, and 79.1 mm2/s, respectively [26]. Span 80 and Tween 20 surfactants, composed of sorbitan fatty acid esters and polyoxyethylene sorbitan carboxylic esters, respectively, were supplied by First Chemical Ltd. (New Taipei City, Taiwan). These surfactants are alcohols attached to three or more hydrocarbon groups. They have high boiling points, excellent solubility capability to polar compounds, low toxicity, and low volatility.
The hydrophilic–lipophilic balance (HLB) values of Span 80 and Tween 20 are 4.3 and 16.7, respectively. The weight proportions of Span 80 and Tween 20 were adjusted to obtain the combined HLB value equal to 10. The surfactant mixture of Span 80 and Tween 20 was used to prepare the emulsion of soybean oil biodiesel by either the phase inversion temperature method or the mechanical homogenization method.

2.2. Preparation of Soybean Oil Biodiesel

The soybean oil biodiesel was produced from soybean oil through transesterification with methanol. The specific gravity, acid value, peroxide value, kinematic viscosity, and moisture content of the soybean oil for producing the biodiesel were 0.922, 0.070 mg KOH/g, 0.21 meq/kg, 79.1 mm2/s, and 0.019 wt.%, respectively. The molar ratio of the soybean oil and methanol was set at 1:6. The reacting tank was stored with the weighted soybean oil and 1 wt. % strong alkali catalyst-sodium methoxide (CH3NaO), while methanol was fed into the tank by a wriggling pump to mix the oil. The reactant mixture was heated to 60 °C to undergo a transesterification reaction for 1 h until the mixture color turned clear. The crude biodiesel product was then separated into glycerol and crude biodiesel by virtue of their gravity difference. Subsequently, the crude biodiesel was water-washed, neutralized with acetic acid, and separated from the water to obtain the soybean oil biodiesel product.
The soybean oil biodiesel was mixed with 2 wt. % Span 80/Tween 20 surfactant mixture in a tank. A mechanical homogenizer (T50 model, IKA Ltd., Staufen town, Germany) was used to mechanically stir the mixture at a speed of 3000 rpm while de-ionized water was fed into the tank by a wriggling pump. The mixture stirring lasted for 20 min until its color turned opaque milky white so that the formation of the emulsion of biodiesel with water was completed. Simple equipment and a short processing time are required to complete the emulsion preparation. While the phase inversion temperature method was applied to prepare the emulsion, the same weight proportion of the mixture components was used. The O/W emulsion was heated to reach its corresponding phase inversion temperature once an abrupt drop of the electrical conductance occurred. The O/W emulsion then turned into a W/O emulsion.

2.3. Analysis of Emulsion Fuel Properties

The amounts of heat release of the three test fuels were analyzed by an oxygen bomb calorimeter (Model 1261 automatically adiabatic type, Parr Inc., Demopolis, AL, USA). A Pensky–Marten closed-cup flash point analyzer was used to measure the flash points of the test fuels, in which an instantaneous spark at such temperature was produced and distinguished immediately. A hydrometer (Model 0709, Ho Yu Inc., Taoyuan City, Taiwan) stabilized in a graduated cylinder filled with the test fuel was used to observe the specific gravity of the fuel.
A distillation temperature analyzer (Model HAD-620, Petroleum Analyzer Inc., Houston, TX, USA) was used to obtain the temperature data of 50 vol. % of the test liquid fuel distilled and condensed, denoted as T50. The data of T50 and the specific gravity of the test fuels were then used to calculate the cetane index (CI) of the fuel [27], which indicates the time delay of compression-ignition of the fuel. The acid value of the test fuel in the unit of mg KOH/g oil was determined by titrating 0.01 N potassium hydroxide (KOH) into the mixture of chemical reagents and the fuel sample until the color of the mixture turned pink [28].

2.4. Engine Performance Analysis

A four-stroke, four-cylinder, naturally aspirated, and direct-injection diesel engine (Model UMBD1, Isuzu Motors Ltd., Nishi-ku, Yokohama, Japan) was used to carry out the diesel engine experiment. The maximum engine power is 88 PS at 2800 rpm. The compression ratio and displacement volume of the engine are 17 and 3856 cc, respectively. The start of injection (SOI) angle of the diesel engine was set at 13° before the top dead center (BTDC) and kept constant during the engine operation whether the neat biodiesel or biodiesel emulsion was used as the engine fuel. The liquid fuel is injected directly into the cylinder by a mechanical pump. The compression-ignition engine was accompanied by an engine dynamometer (FE-150S model, Borghi & Saveri Ltd., Bologna, Pieve di Cento (BO), Italy) to control engine loading. The engine test data were acquired by an automatic engine data acquisition system. The engine torque remained constant at 98 N·m with varying engine speeds from 800 rpm to 2000 rpm.
A gas analyzer (CA-300 NSX model, Bacharach Ltd., Pittsburgh, PA, USA) was used to measure the gaseous emissions, such as NOx, CO, CO2, and O2, the excess air ratio, and the combustion efficiency from the burning of the three test fuels in the engine. A K-type thermocouple was aligned with the gas probe to record the exhaust gas temperature from the engine. The mean values of the experimental data were calculated by carrying out each experiment three to five times. The experimental uncertainties for the amount of heat release, exhaust gas temperature, combustion efficiency, CO2, O2, NOx, CO, and excess air ratio, were 2.14%, 3.56%, 2.89%, 2.21%, 1.72%, 3.35%, 2.37%, and 1.83%, respectively.

3. Results and Discussion

The phase inversion temperature method was used to prepare the emulsions of soybean oil biodiesel. The emission characteristics and engine performance from burning the emulsions by phase inversion temperature were compared with those of the neat soybean oil biodiesel and the emulsions by a mechanical homogenizer.

3.1. Fuel Properties of the Test Fuels

The fuel properties of the three test fuels are compared in Table 1. The fatty acid methyl esters (FAME) reached 98.7 wt. %, which exceeded the FAME composition standards, such as ASTM D6751 and EN 14214, for biodiesel [29]. The FAME compositions made from soybean oil, palm oil, grape seed oil, Philippine tung oil, and kesambi oil were primarily composed of C16~C18 [30], whose carbon numbers are similar to those of petro-derived diesel. In comparison with the amount of heat release (44.8 MJ/kg) of palm oil methyl ester (POME) [30], the soybean oil biodiesel appeared to have a lower amount of heat release (39.62 MJ/kg). There was a 20 wt. % water content in the two emulsions, resulting in a significantly lower amount of heat release of about 20.34% than the neat biodiesel. In addition, the kinematic viscosities of the two emulsions were obviously larger than the neat soybean oil biodiesel. The emulsions prepared by the mechanical homogenizer had the highest kinematic viscosity, 52.26 mm2/s, in comparison with the lowest one of the neat biodiesel (4.71 mm2/s). The emulsion prepared by the PIT method was observed to have a much smaller mean droplet size of 1378 nm than the 1797 nm size of the emulsion prepared by the mechanical homogenization method. The specific gravity of these emulsions (0.93) was relatively larger than that of the neat biodiesel (0.88).

3.2. Exhaust Gas Temperature

The exhaust gas temperatures from burning the three test fuels at a constant engine torque of 98 N·m are shown in Figure 1. The increase in the engine speed resulted in an increase in engine power output, raising the amounts of both injected fuel and heat release [31]. Hence, the exhaust gas temperatures for the three fuels increased with the engine speed accordingly. The increase in biodiesel proportion to 10 vol. % in its blend with ultra-low sulfur diesel (ULSD) resulted in a decrease in exhaust gas temperature by approximately 4% [32]. The two biodiesel emulsions prepared by either mechanical homogenization or phase inversion temperature methods had nearly similar heat release values, which were 31.28 MJ/kg and 31.56 MJ/kg, respectively. The biodiesel emulsions contained about 80% heat release of the neat biodiesel because there was nearly no heat release from burning de-ionized water in the emulsion. It was also found that the neat biodiesel appeared to have the highest exhaust gas temperature among the test fuels in Figure 1. The mean droplet sizes of the emulsions by the phase inversion temperature method are smaller than those of the emulsions by the mechanical homogenization one. More heat was released from a more intense micro-explosion occurrence of a higher number of smaller water droplets of the former emulsion [33], leading to higher exhaust gas temperature from burning the emulsion prepared by the PIT method. Moussa et al. [34] also observed that a higher number of small water droplets caused a higher rate of micro-explosions, higher burning efficiency, and consequently a higher burning gas temperature.

3.3. BSFC

Brake-specific fuel consumption (BSFC) is defined as follows:
BSFC   ( g / kWh ) = m ˙ f   g ∕ h r P b   k W
where
Pb (kW) = 2πN (rev/s) × Tb (N × m) × 10−3
is the engine brake power of the engine, Tb is the brake torque of the engine, m ˙ f   is the fuel consumption rate of the engine required to provide brake power output Pb, and N is the engine speed.
Lower BSFC values represent either higher heat release from fuel burning or higher energy conversion efficiency of the engine, which is preferable. In this study, the BSFC values appeared to decrease with the increase in engine speed due to larger energy conversion efficiency at an increasing engine speed in Figure 2. Therefore, less fuel is required to attain the same engine power output [35].
The soybean oil biodiesel was observed to have the lowest BSFC value because of its highest heat release among the three test fuels. Maawa et al. [36] observed that the blend of diesel and 20 vol. % biodiesel emulsified with 5 vol. % water might reduce the BSFC by 7.27%. In contrast, the emulsion prepared by a mechanical homogenizer produced a lower number of coarser dispersed droplets, leading to a lesser extent of micro-explosions, a lower burning efficiency, and less heat release than the emulsion prepared by the PIT method. As a consequence, the extent of complete combustion of the emulsion prepared by the mechanical homogenizer in the diesel engine was inferior to that of the PIT method. Hence, the emulsion prepared by the mechanical homogenization method required the highest fuel consumption rate and thus the highest BSFC among the three fuels.

3.4. Brake Fuel Conversion Efficiency

Brake fuel conversion efficiency (bfce) is defined as the ratio of brake power output to the rate of heat release for each engine cycle [37], which is expressed below:
η f   = P b           m ˙ f Q H V   = 3600   k W b s f c   g ∕ k W ⋅ h r × Q H v   M J k g
where QHV is the higher heating value of the fuel. The denominator of the above equation denotes the amount of heat released from burning the test fuel.
Higher brake fuel conversion efficiency implies larger conversion efficiency of brake power output from the heat release through fuel burning [38], which is preferable. Figure 3 displays the comparison of bfce among the three test fuels under a constant engine torque of 98 N∙m and varying engine speeds. The curve trend of ηf in Figure 3 differs from that of BSFC in Figure 2. The brake fuel conversion efficiency was observed to increase with the increase in the engine speed. This finding implies that the higher engine speed incurred more efficient engine operation to convert more power output from burning the test fuels, leading to higher brake fuel conversion efficiency. Duda et al. [39] found that the blend of 80 vol. % rapeseed oil biodiesel with diesel reduced the brake fuel conversion efficiency by 3%. The soybean oil biodiesel appeared to have the highest brake fuel conversion efficiency primarily due to its higher oxygen content than the two emulsions to enhance the burning efficiency [40]. Moreover, the start of injection (SOI) angle was kept constant during the diesel engine operation powered with the three different fuel samples. The burning efficiency would be reduced for those two biodiesel emulsions because of the increase in injection duration and triggering a delay in compression-ignition. However, the micro-explosion effects during the burning of the emulsion of many water droplets distributed within the outer-continuous phase of soybean oil biodiesel enhanced the extent of the second atomization of the injected emulsion fuel and increased the burning efficiency afterward. The two emulsions, which comprised 20 wt. % water content, decreased the amount of heat release and brake fuel conversion efficiency accordingly. However, the three ηf curves approached together when the engine speed increased to 2000 rpm. This finding implies that the degree of the micro-explosion phenomenon was further facilitated at a higher engine speed to produce more engine power output and thus increase the brake fuel conversion efficiency. In addition, there are far more smaller dispersed droplets in the emulsion prepared by the PIT method than that prepared by the mechanical homogenization one. The burning efficiency of the latter emulsion was thus lower than the former, resulting from the higher BSFC and lower ηf values of the emulsion prepared by a mechanical homogenizer.

3.5. NOx Emissions

The comparison of nitrogen oxides (NOx) from burning the three test fuels in a compression-ignition diesel engine is shown in Figure 4. The formation of NOx emissions was influenced by the peak flame temperature, the amounts of oxygen and nitrogen available in the reactant mixture, the residence time of high-temperature burning gas, the peak pressure value, etc. [41]. The NOx emissions were observed to decrease with the engine speed in Figure 4. This finding is ascribed to the fact that although the burning gas temperature and peak pressure value increased with the increase in engine speed, the residence time of high-temperature burning gas was reduced, leading to a reduction in NOx formation.
The neat soybean oil biodiesel appeared to have the highest NOx emissions among the test fuels due to it having the highest heat release from burning the neat biodiesel. In contrast, the water droplets in the emulsion absorb a lot of latent heat from the surrounding flame during their evaporation processes. The occurrence of an endothermic water–gas reaction during the burning process also consumed a partial amount of heat release. Hence, the two emulsions composed of de-ionized water and soybean oil biodiesel emitted much less NOx during their burning processes than the neat biodiesel. The results agreed well with Abdollahi et al. [42]. They considered that the emulsion of base fuel is an adequate technology for reducing NOx emissions, which might reduce 90% NOx when the blend of diesel and 5 vol. % waste cooking oil biodiesel emulsified with 5 vol. % water is used as the engine fuel. Compared with the emulsion prepared by a mechanical homogenizer, the emulsion prepared by the PIT method emitted more NOx because of larger heat release from more intense micro-explosions by a higher number of smaller water droplets, enhancing the extent of complete combustion and thus producing ahigher burning gas temperature. Hence, the NOx emissions from burning the latter emulsion prepared by the PIT method were higher than that from the former emulsion.

3.6. CO Emissions

Figure 5 shows the carbon monoxide (CO) emissions from burning the three test fuels in the diesel engine. Higher CO formation indicates a larger extent of incomplete combustion and less heat release. The increase in engine speed reduced the CO emissions from burning the test fuels due to more heat release and higher burning efficiency at larger engine speeds. The CO concentration in an engine cylinder is strongly related to the burning gas temperature. The lower gas temperature would prevent the conversion from CO to CO2, leading to increased CO emissions from the engine. The reaction rate equation of CO is as follows:
CO + OH → CO2 + H
K+CO (cm3/gmol·s) = 6.76 × 1010 exp [T/1104]
where K+CO is the reaction rate constant of CO oxidation and T is the burning gas temperature in unit K. As seen from Equations (4) and (5), the oxidation rate of CO increases with the burning gas temperature at an exponential rate [43]. A higher burning gas temperature enhances the oxidation rate from CO to CO2, resulting in a lower CO concentration. Hence, the CO emissions at a lower engine speed are higher than that at a higher engine speed in Figure 5. The neat biodiesel was observed to have the lowest CO emissions because of it having the highest amount of heat release and the highest exhaust gas temperature in Figure 1 among the three test fuels. Elumalai et al. [44] found that the increase of biodiesel percentage in its blend with diesel caused the reduction in CO emissions. The B20 blends of 20 vol. % biodiesel with the remaining diesel might significantly decrease CO emissions by 36.56% in comparison with neat diesel [44]. The biodiesel emulsions prepared by the PIT method contained a higher number of smaller water droplets, resulting in more intense micro-explosions, more heat release, and thus a higher exhaust gas temperature in Figure 1 than that of the emulsion prepared by a mechanical homogenizer. Hence, lower CO emissions from burning the former emulsion were observed. The lower kinematic viscosity of the neat biodiesel than the two emulsions was also prone to burning the fuel more completely to cause a higher extent of CO oxidation, leading to the lowest CO emissions in Figure 5.

3.7. CO2 Content

Higher CO2 content indicates a higher extent of complete combustion. The CO2 content from burning the three fuels is shown in Figure 6. The CO2 content of the three test fuels increased with the increase in engine speed. This finding is attributed to the fact that the increased engine speed requires more fuel consumption to provide higher power output. Therefore, a higher burning gas temperature was produced to enhance the oxidation rate of CO and unburned hydrocarbons [45].
The neat soybean oil biodiesel was observed to have slightly lower CO2 because less surrounding air is required during the burning process under the higher oxygen content (10 wt. %) of the neat biodiesel. The higher brake fuel conversion efficiency of the neat biodiesel in Figure 3 required a lesser amount of air during the burning process. In addition, a lesser amount of biodiesel fuel than the two emulsions was burned to attain the same engine power output. Hence, less CO2 formation appeared from burning the neat biodiesel. In contrast, the biodiesel emulsion prepared by a mechanical homogenizer, with the lowest amount of heat release and brake fuel conversion efficiency in Figure 3, required more fuel consumption and surrounding air to react, hence producing the highest CO2 content. Estrada et al. [46] also found that the application of H2–diesel dual fuel might increase brake fuel conversion efficiency by around 3–36% under various engine speeds, resulting in a drop in CO2 emissions by about 5–34%.

3.8. O2 Content

Greater formation of carbon dioxide (CO2) content consumed greater amounts of O2 in the reacting environment. Hence, the variation in the O2 content with the engine speeds and fuel samples were complementary to the CO2 ones. The O2 content was found to decrease with the increased engine speed. This finding is ascribed to the fact that higher oxygen consumption is required to burn with the increased fuel consumption at higher engine speeds, leading to lower oxygen emissions. The neat biodiesel appeared to have the highest O2 content due to its higher oxygen content (10 wt. %) than the emulsions of de-ionized water-in-soybean-oil biodiesel. In addition, less air is burned with the neat biodiesel under the same engine power output. Thus, more oxygen was left in the exhaust gas system. Mohammed et al. [47] also observed that the increase in biodiesel percentages to 30 vol. % in its blend with diesel might reduce CO2 emission by 22%. The emulsion prepared by the PIT method produced smaller droplets to facilitate more intense second-atomization and higher burning efficiency, resulting in less air being consumed in the engine cylinder. A higher O2 content than that of the biodiesel emulsion prepared by a mechanical homogenizer was thus observed, as shown in Figure 7.

3.9. Excess Air Ratio and Equivalence Ratio

Figure 8 illustrates the curve trends of the excess air ratios from burning the three test fuels. The excess air ratios (%) which were analyzed by a gas analyzer were observed to be reduced with the increase in engine speed. The burning efficiency was enhanced with a higher burning gas temperature at an increased engine speed. Thus, more air was consumed at a higher engine speed, thus decreasing the excess air ratio at the increased engine speed. The neat biodiesel was shown to have the highest excess air ratio among the three test fuels due to it having the highest oxygen content. The emulsion prepared by the PIT method formed many smaller water droplets to facilitate the burning extent; thus, less air was consumed to produce a higher excess air ratio than that of the emulsion prepared by a mechanical homogenizer.
The fuel–air equivalence ratio is defined as follows:
Φ = (mF/mA)actual/(mF/mA)stoichiometric
which is the ratio of the actual fuel-to-air mass ratio to the stoichiometric fuel-to-air mass ratio. Φ > 1 indicates fuel-rich combustion, while Φ < 1 is fuel-lean burning.
As shown in Equation (6), the equivalence ratio is reciprocal to the excess air ratio. Hence, the curve trends of the excess air ratio in Figure 8 are contrary to the equivalence ratio in Figure 9. This finding implies that the equivalence ratio increased with the engine speed, and the neat biodiesel appeared to have the lowest equivalence ratio among the three test fuels. Diesel engines are generally operated under fuel-lean burning conditions. The CO2 emissions are positively related to the equivalence ratio [48]. The soybean oil biodiesel had a lower equivalence ratio, hence the lower CO2 emissions, as shown in Figure 6 and Figure 9. Moreover, the trend in O2 emissions is contrary to that of the equivalence ratio. The neat biodiesel emitted the highest O2 associated with the lowest equivalence ratio. Saha et al. [49] found that the emulsion of diesel with water had a higher equivalence ratio than neat diesel. The equivalence ratio of the emulsion prepared by the PIT method was lower than that of the emulsion prepared by a mechanical homogenizer and it had higher O2 emissions and a higher amount of heat released from burning the former emulsion. In addition, the emulsion prepared by the PIT method produced smaller water droplets; hence, more intense micro-explosions and less fuel were required than that of the emulsion prepared by a mechanical homogenizer to attain the same engine power output. This approach resulted in a lower equivalence ratio and a higher excess air ratio of the former emulsion prepared by the PIT method.

4. Conclusions

The engine performance and emission characteristics of the diesel engine fueled with the neat soybean oil biodiesel and the emulsions of soybean oil biodiesel with de-ionized water prepared by the phase inversion temperature (PIT) method and a mechanical homogenizer were analyzed and compared. The major results of this experimental study are summarized as follows.
(1)
In comparison with those emulsions containing 20 wt. % de-ionized water, the neat biodiesel was found to have the highest amount of heat release and the lowest brake-specific fuel consumption (BSFC). The biodiesel emulsion prepared by the PIT method appeared to have a smaller mean droplet size and a lower bsfc value. On the other hand, it had a higher amount of heat release than that of the emulsion prepared by a mechanical homogenizer.
(2)
The neat biodiesel was observed to have a lower equivalence ratio and CO2 and CO emissions and a higher excess air ratio, higher O2 and NOx emissions, higher brake fuel conversion efficiency, and a higher exhaust gas temperature than the two biodiesel emulsions.
(3)
The emulsion produced by the mechanical homogenizer appeared to have lower brake fuel conversion efficiency, excess air ratio, O2 and NOx emissions, and exhaust gas temperature and higher CO and CO2 emissions and a higher equivalence ratio than the emulsion prepared by the PIT method.
(4)
The emulsions prepared by the phase inversion temperature (PIT) method were found to produce superior engine performance and lower emissions than those prepared by other traditional emulsification methods such as the mechanical homogenization one. The PIT method is considered a promising emulsification method for preparing emulsion fuel as an alternative environmentally friendly fuel to petro-derived diesel.

Author Contributions

Conceptualization, C.-Y.L.; methodology, C.-Y.L.; validation, K.-H.L.; investigation, K.-H.L.; resources, C.-Y.L.; data curation, K.-H.L.; writing—original draft preparation, C.-Y.L. and K.-H.L.; writing—review and editing, C.-Y.L.; supervision, C.-Y.L.; project administration, C.-Y.L.; funding acquisition, C.-Y.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Science and Technology Council, Taiwan; grant numbers NSTC 109-2221-E-019-024 and NSTC 107-2221-E-019-056-MY2. The APC was funded by National Taiwan Ocean University, Taiwan.

Data Availability Statement

Data are available in the article or upon request from the authors.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Hamid, M.F.; Teoh, Y.H.; Idroas, M.Y.; Mohamed, M.; Sa’ad, S.; Mat, S.C.; Nguyen, H.T. A review of the emulsification method for alternative fuels used in diesel engines. Energies 2022, 15, 9429. [Google Scholar] [CrossRef]
  2. Kumar, N.; Verma, A.; Mandal, A. Formation, characteristics and oil industry applications of nanoemulsions: A review. J. Pet. Sci. Eng. 2021, 206, 109042. [Google Scholar] [CrossRef]
  3. Ittoo, B.; Ooi, J.B.; Tran, M.V.; Jaliliantabar, F.; Najafi, G.H.; Swamy, V. Effects of dispersed multiwalled carbon nanotubes on the micro-explosion and combustion characteristics of 2-methylfuran–diesel mixture droplets. Fuel 2022, 316, 123308. [Google Scholar] [CrossRef]
  4. Lin, C.Y. The influences of promising feedstock variability on advanced biofuel production: A review. J. Mar. Sci. Tech-Taiw. 2021, 29, 714–730. [Google Scholar] [CrossRef]
  5. Sousa, A.M.; Pereira, M.J.; Matos, H.A. Oil-in-water and water-in-oil emulsions formation and demulsification. J. Pet. Sci. Eng. 2021, 210, 110041. [Google Scholar] [CrossRef]
  6. Kumar, S.; Pandey, A.; Trifkovic, M.; Bryant, S.L. A facile and economical configuration for continuous generation and separation of oil in water emulsions. Sep. Purif. Technol. 2021, 256, 117849. [Google Scholar] [CrossRef]
  7. Feng, J.; Esquena, J.; Rodriguez-Abreu, C.; Solans, C. Key features of nano-emulsion formation by the phase inversion temperature method. J. Dispers. Sci. Technol. 2021, 42, 1073–1081. [Google Scholar] [CrossRef]
  8. Choradiya, B.R.; Patil, S.B. A comprehensive review on nanoemulsion as an ophthalmic drug delivery system. J. Mol. Liq. 2021, 339, 116751. [Google Scholar] [CrossRef]
  9. Souto, E.B.; Cano, A.; Martins-Gomes, C.; Coutinho, T.E.; Zielińska, A.; Silva, A.M. Microemulsions and nanoemulsions in skin drug delivery. Bioengineering 2022, 9, 158. [Google Scholar] [CrossRef]
  10. Azmi, N.A.N.; Elgharbawy, A.A.; Motlagh, S.R.; Samsudin, N.; Salleh, H.M. Nanoemulsions: Factory for food, pharmaceutical and cosmetics. Processes 2019, 7, 617. [Google Scholar] [CrossRef] [Green Version]
  11. Islam, F.; Saeed, F.; Afzaal, M.; Hussain, M.; Ikram, A.; Khalid, M.A. Food grade nanoemulsions: Promising delivery systems for functional ingredients. J. Food Sci. Technol. 2022, 1–11. [Google Scholar] [CrossRef]
  12. Solanki, K.; Rathi, N.; Patani, P. Microemulsions: Current Trends in Novel Drug Delivery Systems. J. Pharm. Negat. Results 2022, 13, 2327–2334. [Google Scholar]
  13. Dado, G.P.; Knox, P.W.; Lang, R.M.; Knock, M.M. Nonlinear changes in phase inversion temperature for oil and water emulsions of nonionic surfactant mixtures. J. Surfactants Deterg. 2022, 25, 63–78. [Google Scholar] [CrossRef]
  14. Liu, R.; Tian, X.; Wang, Z.; Zhang, J.; Lu, P.; Huang, C. Water vapor barrier coating based on nanocellulose crystals stabilized AESO oil-in-water Pickering emulsion. Prog. Org. Coat. 2021, 159, 106479. [Google Scholar] [CrossRef]
  15. Ettefaghi, E.; Rashidi, A.; Ghobadian, B.; Najafi, G.; Ghasemy, E.; Khoshtaghaza, M.H.; Mazlan, M. Bio-nano emulsion fuel based on graphene quantum dot nanoparticles for reducing energy consumption and pollutants emission. Energy 2021, 218, 119551. [Google Scholar] [CrossRef]
  16. Masharuddin, S.M.S.; Karim, Z.A.A.; Said, M.A.M.; Amran, N.H.; Ismael, M.A. The evolution of a single droplet water-in-palm oil derived biodiesel emulsion leading to micro-explosion. Alex. Eng. J. 2022, 61, 541–547. [Google Scholar] [CrossRef]
  17. Lee, J.; Li, C.; Kang, S.; Park, J.; Kim, J.M.; Kim, D.H. Pt nanoparticles encapsulated in CeO2 over-layers synthesized by controlled reductive treatment to suppress CH4 formation in high-temperature water-gas shift reaction. J. Catal. 2021, 395, 246–257. [Google Scholar] [CrossRef]
  18. Thiyagarajan, S.; Varuvel, E.; Karthickeyan, V.; Sonthalia, A.; Kumar, G.; Saravanan, C.G.; Pugazhendhi, A. Effect of hydrogen on compression-ignition (CI) engine fueled with vegetable oil/biodiesel from various feedstocks: A review. Int. J. Hydrogen Energy 2022, 47, 37648–37667. [Google Scholar] [CrossRef]
  19. Lin, C.Y.; Lin, Y.W. Fuel characteristics of biodiesel produced from a high-acid oil from soybean soapstock by supercritical-methanol transesterification. Energies 2012, 5, 2370–2380. [Google Scholar] [CrossRef] [Green Version]
  20. Lin, C.Y. Effects of the degree of unsaturation of fatty acid esters on engine performance and emission characteristics. Processes 2022, 10, 2161. [Google Scholar] [CrossRef]
  21. Elumalai, P.V.; Parthasarathy, M.; Hariharan, V.; Jayakar, J.; Mohammed Iqbal, S. Evaluation of water emulsion in biodiesel for engine performance and emission characteristics. J. Therm. Anal. Calorim. 2022, 147, 4285–4301. [Google Scholar] [CrossRef]
  22. Safaya, M.; Rotliwala, Y.C. Nanoemulsions: A review on low energy formulation methods, characterization, applications and optimization technique. Mater. Today Proc. 2020, 27, 454–459. [Google Scholar] [CrossRef]
  23. Shao, P.; Feng, J.; Sun, P.; Xiang, N.; Lu, B.; Qiu, D. Recent advances in improving stability of food emulsion by plant polysaccharides. Food Res. Int. 2020, 137, 109376. [Google Scholar] [CrossRef] [PubMed]
  24. Feng, S.; Zhang, S.; Jiang, M.; Liu, F.; Chen, K.; Zhang, Y. Effects of glycation methods on the interfacial behavior and emulsifying performance of soy protein isolate-gum Arabic conjugates. Int. J. Biol. Macromol. 2023, 233, 123554. [Google Scholar] [CrossRef] [PubMed]
  25. Lin, C.Y.; Chiu, C.C. Effects of oxidation during long-term storage on the fuel properties of palm oil-based biodiesel. Energy Fuels 2009, 23, 3285–3289. [Google Scholar] [CrossRef]
  26. Formosa Oilseed Processing Co. Ltd. Test Report for Frying Vegetable Oil. Available online: https://www.fopco.com.tw/index.php (accessed on 20 November 2022).
  27. Prak, D.L.; Cooke, J.; Dickerson, T.; McDaniel, A.; Cowart, J. Cetane number, derived cetane number, and cetane index: When correlations fail to predict combustibility. Fuel 2021, 289, 119963. [Google Scholar] [CrossRef]
  28. Cho, K.; Rana, B.S.; Cho, D.W.; Beum, H.T.; Kim, C.H.; Kim, J.N. Catalytic removal of naphthenic acids over Co-Mo/γ-Al2O3 catalyst to reduce total acid number (TAN) of highly acidic crude oil. Appl. Catal. A Gen. 2020, 606, 117835. [Google Scholar] [CrossRef]
  29. Jamaluddin, N.A.M.; Riayatsyah, T.M.I.; Silitonga, A.S.; Mofijur, M.; Shamsuddin, A.H.; Ong, H.C.; Rahman, S.A. Techno-economic analysis and physicochemical properties of Ceiba pentandra as second-generation biodiesel based on ASTM D6751 and EN 14214. Processes 2019, 7, 636. [Google Scholar] [CrossRef] [Green Version]
  30. Ong, H.C.; Mofijur, M.; Silitonga, A.S.; Gumilang, D.; Kusumo, F.; Mahlia, T.M.I. Physicochemical properties of biodiesel synthesised from grape seed, philippine tung, kesambi, and palm oils. Energies 2020, 13, 1319. [Google Scholar] [CrossRef] [Green Version]
  31. Hoang, A.T.; Tran, Q.V.; Al-Tawaha, A.R.M.S.; Nguyen, X.P. Comparative analysis on performance and emission characteristics of an in-Vietnam popular 4-stroke motorcycle engine running on biogasoline and mineral gasoline. Renew. Energy Focus 2019, 28, 47–55. [Google Scholar] [CrossRef]
  32. Tran, V.D.; Le, A.T.; Hoang, A.T. An experimental study on the performance characteristics of a diesel engine fueled with ULSD-biodiesel blends. Int. J. Renew. Energy Dev. 2021, 10, 183. [Google Scholar] [CrossRef]
  33. Avulapati, M.M.; Megaritis, T.; Xia, J.; Ganippa, L. Experimental understanding on the dynamics of micro-explosion and puffing in ternary emulsion droplets. Fuel 2019, 239, 1284–1292. [Google Scholar] [CrossRef]
  34. Moussa, O.; Tarlet, D.; Massoli, P.; Bellettre, J. Parametric study of the micro-explosion occurrence of W/O emulsions. Int. J. Therm Sci. 2018, 133, 90–97. [Google Scholar] [CrossRef]
  35. Wen, J.; Zhao, D.; Zhang, C. An overview of electricity powered vehicles: Lithium-ion battery energy storage density and energy conversion efficiency. Renew. Energy 2020, 162, 1629–1648. [Google Scholar] [CrossRef]
  36. Maawa, W.N.; Mamat, R.; Najafi, G.; De Goey, L.P.H. Performance, combustion, and emission characteristics of a CI engine fueled with emulsified diesel-biodiesel blends at different water contents. Fuel 2020, 267, 117265. [Google Scholar] [CrossRef]
  37. Mahabadipour, H.; Srinivasan, K.K.; Krishnan, S.R. An exergy analysis methodology for internal combustion engines using a multi-zone simulation of dual fuel low temperature combustion. Appl. Energy 2019, 256, 113952. [Google Scholar] [CrossRef]
  38. Fattah, I.R.; Masjuki, H.H.; Kalam, M.A.; Mofijur, M.; Abedin, M.J. Effect of antioxidant on the performance and emission characteristics of a diesel engine fueled with palm biodiesel blends. Energy Convers. Manag. 2014, 79, 265–272. [Google Scholar] [CrossRef]
  39. Duda, K.; Wierzbicki, S.; Mikulski, M.; Konieczny, Ł.; Łazarz, B.; Letuń-Łątka, M. Emissions from a medium-duty crdi engine fuelled with diesel: Biodiesel blends. Transp. Probl. 2021, 16, 39–49. [Google Scholar] [CrossRef]
  40. Xia, C.; Brindhadevi, K.; Elfasakhany, A.; Alsehli, M.; Tola, S. Performance, combustion and emission analysis of castor oil biodiesel blends enriched with nanoadditives and hydrogen fuel using CI engine. Fuel 2021, 306, 121541. [Google Scholar] [CrossRef]
  41. Zhao, Z.; Zhang, Z.; Zha, X.; Gao, G.; Li, X.; Wu, F.; Zhang, L. Internal association between combustion behavior and NOx emissions of pulverized coal MILD-oxy combustion affected by adding H2O. Energy 2023, 263, 125878. [Google Scholar] [CrossRef]
  42. Abdollahi, M.; Ghobadian, B.; Najafi, G.; Hoseini, S.S.; Mofijur, M.; Mazlan, M. Impact of water–biodiesel–diesel nano-emulsion fuel on performance parameters and diesel engine emission. Fuel 2020, 280, 118576. [Google Scholar] [CrossRef]
  43. Zhao, S.; Chen, F.; Duan, S.; Shao, B.; Li, T.; Tang, H.; Zhang, T. Remarkable active-site dependent H2O promoting effect in CO oxidation. Nat. Commun. 2019, 10, 3824. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  44. Elumalai, P.V.; Krishna Moorthy, R.; Parthasarathy, M.; Samuel, O.D.; Owamah, H.I.; Saleel, C.A.; Afzal, A. Artificial neural networks model for predicting the behavior of different injection pressure characteristics powered by blend of biofuel-nano emulsion. Energy Sci. Eng. 2022, 10, 2367–2396. [Google Scholar] [CrossRef]
  45. Ghaffarzadeh, S.; Toosi, A.N.; Hosseini, V. An experimental study on low temperature combustion in a light duty engine fueled with diesel/CNG and biodiesel/CNG. Fuel 2020, 262, 116495. [Google Scholar] [CrossRef]
  46. Estrada, L.; Moreno, E.; Gonzalez-Quiroga, A.; Bula, A.; Duarte-Forero, J. Experimental assessment of performance and emissions for hydrogen-diesel dual fuel operation in a low displacement compression ignition engine. Heliyon 2022, 8, e09285. [Google Scholar] [CrossRef]
  47. Mohammed, A.A.; Yaseen, A.A.; Atiyah, I.K. Experimental study for the effect of damaged vegetable oil biofuels on diesel engine performance and exhaust emission. J. Eng. Sci. Technol. 2021, 16, 1110–1121. [Google Scholar]
  48. Valera-Medina, A.; Gutesa, M.; Xiao, H.; Pugh, D.; Giles, A.; Goktepe, B.; Bowen, P. Premixed ammonia/hydrogen swirl combustion under rich fuel conditions for gas turbines operation. Int. J. Hydrogen Energy 2019, 44, 8615–8626. [Google Scholar] [CrossRef]
  49. Saha, D.; Sinha, A.; Roy, B.; Mishra, L. Effects of water-diesel emulsification on performance and emission characteristics of CI engine: A review. In Innovations in Energy, Power and Thermal Engineering 2022; Springer: Singapore, 2022; pp. 95–107. [Google Scholar]
Processes 11 00907 g001 550
Figure 1. Exhaust gas temperature from burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 1. Exhaust gas temperature from burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 2. BSFC of burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 2. BSFC of burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 3. Brake fuel conversion efficiency of burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 3. Brake fuel conversion efficiency of burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 4. Nitrogen oxide (NOx) emissions from burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 4. Nitrogen oxide (NOx) emissions from burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 5. Carbon monoxide (CO) emissions from burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 5. Carbon monoxide (CO) emissions from burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 6. Carbon dioxide (CO2) content from burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 6. Carbon dioxide (CO2) content from burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 7. O2 content from burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 7. O2 content from burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 8. Excess air ratio from burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 8. Excess air ratio from burning the three test fuels under a constant engine torque and varying engine speeds.
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Figure 9. Equivalence ratio of burning the three test fuels under a constant engine torque and varying engine speeds.
Figure 9. Equivalence ratio of burning the three test fuels under a constant engine torque and varying engine speeds.
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Table
Table 1. Fuel properties of the test fuels.
Table 1. Fuel properties of the test fuels.
Fuel PropertySoybean Oil BiodieselEmulsions by PITEmulsions by a Mechanical Homogenizer
FAME (wt. %)98.7──
Amount of heat release (MJ/kg)39.6231.5631.28
Kinematic viscosity
(at 40 °C)		4.7149.6852.26
Specific gravity0.880.9300.930
Mean droplet size (nm)─13781697
Acid value (mg KOH/g)0.26──
Moisture content (wt. %)0.042──
Cetane index47.85──
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Lin, C.-Y.; Lin, K.-H. Comparison of the Engine Performance of Soybean Oil Biodiesel Emulsions Prepared by Phase Inversion Temperature and Mechanical Homogenization Methods. Processes 2023, 11, 907. https://doi.org/10.3390/pr11030907

AMA Style

Lin C-Y, Lin K-H. Comparison of the Engine Performance of Soybean Oil Biodiesel Emulsions Prepared by Phase Inversion Temperature and Mechanical Homogenization Methods. Processes. 2023; 11(3):907. https://doi.org/10.3390/pr11030907

Chicago/Turabian Style

Lin, Cherng-Yuan, and Keng-Hung Lin. 2023. "Comparison of the Engine Performance of Soybean Oil Biodiesel Emulsions Prepared by Phase Inversion Temperature and Mechanical Homogenization Methods" Processes 11, no. 3: 907. https://doi.org/10.3390/pr11030907

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