Experimental investigation on effect of MgO nanoparticles on cold flow properties, performance, emission and combustion characteristics of waste cooking oil biodiesel

Fuel 220 (2018) 780–791

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Full Length Article

Experimental investigation on effect of MgO nanoparticles on cold flow properties, performance, emission and combustion characteristics of waste cooking oil biodiesel

T

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Alok Ranjana, S.S. Dawna,b, , J. Jayaprabakarc, N. Nirmalaa, K. Saikiranc, S. Sai Sriramc Centre of Excellence for Energy Research, Sathyabama Institute of Science and Technology, Chennai 600 119 Tamilnadu, India Centre for Waste Management, Sathyabama Institute of Science and Technology, Chennai 600 119 Tamilnadu, India Department of Mechanical Engineering, Sathyabama Institute of Science and Technology, Chennai 600 119, Tamilnadu, India

G RA P H I C A L AB S T R A C T

A R T I C L E I N F O

A B S T R A C T

Keywords: Pour point Cold filter plugging point Waste cooking oil Biodiesel Performance Emission

Commercialization and effective use of biodiesel is still unattained due to its poor cold storage property. Biodiesel produced from waste cooking oil (WCO) using methanol was blended with 0%, 80% and 90% petroleum-based diesel (PBD) fuel and 20 ppm, 30 ppm, 40 ppm and 50 ppm of magnesium oxide (MgO) nanoparticles. The test fuels quality was found to be within limits of the ASTM standards. 30 ppm concentration of MgO nanoparticles showed improvement in cloud point (CP), cold filter plugging point (CFPP) and pour point (PP) of the test fuels. The results showed that the brake specific fuel consumption (BSFC) of B100W30A, B20W30A and B10W30A fuels were 28.2%, 9.48%, and 2.45% higher than the B100, B20 and B10 fuel respectively. PBD showed lower BSFC but higher brake power (BP) and brake thermal efficiency (BTE) when compared to the other test fuels. The BTE and BP of the B100W30A, B20W30A and B10W30A fuels were 4.57% and 1.17% on an average higher than those of B100, B20 and B10 respectively. In general, MgO nanoparticles blended fuel released relatively lesser emissions than B100, B20, B10 and PBD. Combustion analysis of nanoparticles blended fuel was better than other test fuels and comparable with PBD.

⁎

Corresponding author at: Centre of Excellence for Energy Research, Sathyabama Institute of Science and Technology, Chennai 600 119, Tamilnadu, India. E-mail address: [email protected] (S.S. Dawn).

https://doi.org/10.1016/j.fuel.2018.02.057 Received 29 August 2017; Received in revised form 29 November 2017; Accepted 8 February 2018 0016-2361/ © 2018 Elsevier Ltd. All rights reserved.

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Nomenclature

B100W30A 100% WCO biodiesel blended with 30 ppm MgO nanoparticles B20W30A20% WCO biodiesel and 80% PBD + 30 ppm MgO nanoparticles B10W30A10% WCO biodiesel and 90% PBD + 30 ppm MgO nanoparticles XRD X-ray powder diffraction MC Moisture content

Pmax Maximum cylinder pressure °CAPmax Crank angle at maximum cylinder pressure HRRmax Maximum heat release rate °CAHRRmax Crank angle at maximum heat release rate B100 100% WCO biodiesel B20 20% WCO biodiesel and 80% PBD B10 10% WCO biodiesel and 90% PBD

1. Introduction

rapeseed methyl ester was slightly increased with the addition of SiO2 and MgO nanoparticles [17]. A literature reported that use of MnO2 or MgO additive has enhanced the properties (viscosity, flash point, CP and PP) of diesel fuel [18]. In general, there is less work given on the utilization of metal-based additive to enhance cold flow properties of waste cooking oil biodiesel. Oxygenates have been reported to vary the physicochemical properties, performance and reduced emissions when used as additives in a biodiesel, especially in nanoparticles form, with increased surface area to volume ratio. Numbers of literature have investigated the role of various metal additives in engine performance and emission. Metals additives like barium, cerium, iron, manganese, copper, magnesium, calcium and platinum have catalytic activity and is employed for blending with biodiesel to improve combustion, the performance of the engine and reduce emissions [16,19–21]. Some researcher have reported the application of manganese oxide and copper oxide as additives to improve diesel fuel properties (like flash point, fire point and viscosity) and performance of the fuel in internal combustion (IC) engine [22]. The investigation of SiO2 and MgO nanoparticles as an additive in rapeseed methyl ester showed that emission of NOx and CO was reduced and the performance of engine increased marginally. However, there is no literature available on the use of MgO nanoparticles for enhancing WCO biodiesel-PBD blends performance, emission, combustion and cold flow property. The effect of MgO nanoparticles on cold flow property, engine performance, emission and combustion for WCO biodiesel blends is yet to be reported. The aim of this study is to investigate the effects of MgO nanoparticles additive at different concentration (20 ppm, 30 ppm, 40 ppm and 50 ppm) on the improvement of cold flow properties of WCO biodiesel blends. The study also aims to investigate the impact of the MgO nanoparticles addition in the WCO biodiesel blends for improvement of the performance, emissions and combustion characteristics in a IC engine. The nanoparticles addition proved efficient in the present study is lesser in concentration than that has been reported earlier with other additives. This process is an easy and good alternative for the modification of biodiesel cold flow property.

The need for transportation is increasing and PBD being a very important fuel is in great demand. Reports from experts say that the existing fossil fuel reserve will last no longer than a decade [1]. Moreover, harmful vehicular emissions like CO, HC and SOx, leads to the need for an alternative fuel, which is safer and should be more economical than PBD [2]. In this specific circumstance, biodiesel can be a promising solution because of its practically identical properties to PBD fuel. Biodiesel will play an important role in achieving a significant reduction in emissions [3]. Biodiesel fuel is produced from biomass. Biodiesel is perceived to be non-toxic, non-flammable, sustainable giving less ozone-harming substance outflow and security of supply. Biofuels have several beneficial properties [4]. They emit very less carbon dioxide and carbon monoxide when compared to PBD [1]. Biofuels helps in reduction of carbon dioxide depletion since the biomass burnt releases carbon dioxide, which is in turn taken in by plants for its growth. Because of the excess oxygen molecules in the biodiesel, the emission of carbon monoxide is almost zero [5]. Biodiesel contains a high amount of saturated fatty acid esters, which are prone to form wax/crystals at low temperatures [4]. Wax/ crystal formation arrests the free flow of fuel along pipes and filters, thus influencing the operation of engines, in this way, the poor cold flow properties significantly restrain the utilization of biodiesel in cold climate [6]. There are numerous methods to enhance the cold flow properties of biodiesel, like the application of branched chain alcohol for transesterification, alteration of fatty acid profiles of biodiesel, winterization, mixing petroleum-based diesel with biodiesel and adding additives [7]. In general, mixing PBD with biodiesel shows an improvement in the essential fuel properties of biodiesel, specifically to its low-temperature performance [8]. Chemical additives referred as cold flow improvers when blended with biodiesel improve the biodiesel property. These chemical additives added additionally to biodiesel improves the performance of the engine, combustion characteristics and reduce emission [2,9,10]. Different researchers have investigated the potential of cold flow improvers to enhance the cold flow properties of biodiesel. To the best of our knowledge, very limited researchers have worked on the use of MgO nanoparticles to improve the cold flow property of biodiesel produced from WCO. The CP of madhuca biodiesel was reduced by 10 °C and 13 °C by the addition of 20 (vol.%) ethanol and kerosene respectively, but Lubrizol had no impact on the cloud point [11]. Ethyl acetoacetate was explored as a potential bio-based diluent for enhancing the cold flow properties of biodiesel from WCO [12]. Blends of ethylene vinyl acetate and naphthenic distillates were used for enhancing cold flow properties of Soybean biodiesel [13]. Diesel-biodiesel blend with a cold flow improver Wintron Synergy was explored and was found to bring down CP of the fuel blends [14]. The mixtures of ethyl acetoacetate, iso-decyl methacrylate and iso-octyl methacrylate in various concentrations are used for the study to enhance the cold flow properties of WCO biodiesel [8]. Different cold flow improvers like Poly-alpha-olefin [15]surfactants, including sugar esters, silicone oil, polyglycerol ester and diesel conditioner were explored [16]. PP of the

2. Materials and methods 2.1. Chemicals Methanol (assay 99.0%, HPLC grade), glycine (assay ≥99.7%), NaOH (assay 98.0%, GR grade) and magnesium nitrate hexahydrate (assay 99.0%, GR grade) were purchased from Central Drug House Private Limited, Chennai. PBD used in the current work was purchased from Hindustan Petroleum. 2.2. Production of biodiesel from WCO WCO was obtained from the kitchen of Sathyabama Institute of Science and Technology, Chennai, Tamil Nadu, India. Methanol to WCO (6:1 Molar ratio), NaOH (0.5 wt% of WCO) and the reaction time of 90 min. were maintained in the transesterification process [23]. A batch reactor of 0.5 L capacity comprising of a three-necked round bottom 781

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glass flask equipped with a condenser, a magnetic stirrer with an installed tachometer and a thermometer pocket was used to maintain the reaction temperature within ± 1 °C. The recommended amount of WCO was preheated in the batch reactor. The catalyst and methanol were mixed in a conical flask. The solution in the conical flask was transferred into the batch reactor, on attaining the required reaction temperature. After the reaction, the solution was poured into a separating funnel to remove the lower glycerol layer. Residual methanol was separated with a batch distillation process. The obtained crude biodiesel was then washed several times with warm water to bring the pH value to normal. The fatty acid (FA) composition of WCO and B100 were analyzed by YL6500 GC System coupled with Hewlett Packard’s (HP) system installed with YL-Clarity software for data acquisition. The GC was equipped with flame ionization detector (FID). A TR-WAX (Thermo Scientific) capillary column of length 30 m, diameter 0.53 mm and thickness 1 μm packed with Polyethylene Glycol was used in the present study. Helium was used as a carrier gas at a constant flow rate of 3 mL/ min. The ignition and maximum temperature for FID were set to 471 K and 513 K respectively. After the sample run was over, the oven temperature was cooled back to 323 K so that the subsequent run could be started. Fourier-transform infrared spectroscopy (FT-IR) analysis of B100 was carried out using ALPHA spectrometer equipped with a roomtemperature DTGS detector and was air cooled, supplied by BRUKER OPTIK GmbH, Rudolf-Plank-Straβe 27. The spectrometer uses a permanently aligned ROCKSOLID interferometer which ensures a highenergy throughput and low polarization effects. A Lenovo system with the OPUS spectroscopic software installed was used to control the instrument and perform data processing.

2.5. Blending of nanoparticles The biodiesel blends were prepared in the following proportions: 10% (B10), 20% (B20) and 100% (B100). MgO nanoparticles in different concentration 20 ppm, 30 ppm, 40 ppm and 50 ppm were added to prepared blends. The mixtures were stirred at 500 rpm for 30 min. and then subjected to ultrasonicator for 10 min. to ensure the mixture was well-blended.

2.6. Property testing for test fuels The CP and PP of the test fuels were measured using cloud and pour point apparatus equipped with single compartment cooling with a lowest temperature of −55 °C. The physical and chemical properties of B100, B20, B10, B100W30A, B20W30A and B10W30A such as CP, PP, cold filter plugging point (CFPP), viscosity, density, moisture content (MC), copper strip corrosion test (CCST), flash point, fire point and calorific value were measured according to ASTM standard methods. Table 1 shows outline of the equipments used to determine the fuel properties.

2.7. Setup for engine test A vertical, single cylinder, constant speed, water-cooled, compression ignition Kirloskar TV1 diesel engine was used to test the combustion, performance and emission characteristics of the test fuels. Each sample was poured into the fuel line one after the other and each of the samples were tested for their respective characteristics. Engine tests were performed at five different engine loads of 0%, 25%, 50%, 75% and 100%. A hydraulic dynamometer was used to load the engine. The experimental setup for engine test rig used for the study is shown in Fig. 1. Emission parameters such as CO, HC, CO2, NOX, smoke opacity (SO) and exhaust gas temperature (EGT) were measured by AVL (model Digas 444 N) exhaust gas analyzer. The specifications of the engine used to carry out the various measurements are mentioned in Table 2a and details of AVLDigass 444 N is shown in Table 2b.

2.3. Preparation of MgO nanoparticles Glycine-nitrate combustion method was used to synthesize MgO nanoparticles from Magnesium nitrate [24]. Glycine and nitrate salts were dissolved in a beaker containing 20 mL water and the solution was stirred for an hour at room temperature. This solution was later heated for 1 h at a temperature of 160 °C. The magnetic pellet was removed from the solution when the liquid became a gel. Foam like substance was formed on further heating. Combustion of this substance took place at a temperature of 170 °C. The particles formed on combustion were collected and was ground into fine particles using a mortar and pestle. Calcination was performed for two hours at 600 °C to obtain MgO nanoparticles.

2.8. Uncertainties analysis Experimental uncertainties can arise due to instrument selection, calibration, environment, planning experiment and data collection. Thus, there is need to prove the accuracy of the experiments by performing uncertainty analysis. For this, all observed and calculated performance and emission parameters have been used in the uncertainty equation (Eq. (1)) to obtain% uncertainty in experiments [25].

2.4. XRD test for nanoparticles The MgO nanoparticles was characterized by XRD (Rikagu-SMART lab) operating at a wavelength of 1.5406A° with a scan rate of 4°/min. and scan range between 10° and 80° in a continuous mode. The phases of MgO nanoparticles were identified using the powder diffraction file (PDF).

Table 1 List of equipments for fuel property testing. Property

Equipment

Manufacturer

Model

CP PP CFPP Viscosity (@ 40 °C) CSCT (@ 60 °C for 3 h.) Flash point Fire point Calorific value

CP and PP tester CP and PP tester CFPP apparatus Canon-Fenske Viscometer CSCT bomb Pensky-Martin closed cup tester Pensky-Martin closed cup tester Digital bomb calorimeter apparatus

Hindustan Apparatus Mfg. Co., India Hindustan Apparatus Mfg. Co., India EIE Instruments Pvt. Ltd. Universal lab product Co., India Kochler, India Deep vision instruments Pvt. Ltd., India Deep vision instruments Pvt. Ltd., India M. K. Scientific Instruments, India

HAMCO9C HAMCO9C EIE-PTLT-126A – K25200 – – MK001

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Table 3 FA composition of WCO and B100. Chemical formulae

C14H28O2 C16H32O2 C16H30O2 C18H36O2 C18H34O2 C18H32O2 C18H30O2

Fatty acid

Myristic acid Palmitic acid Palmitoleic acid Stearic acid Oleic acid Linoleic acid Linolenic acid

Fig. 1. Graphical setup for engine test. Arachidic acid C20H40O2 C20H38O2 Gondoic acid C22H44O2 Behenic acid Lingnoceric acid C24H48O2 Saturated Fatty acid Unsaturated fatty acid

Table 2a Engine specifications. Engine Parameters

Conditions

Cooling Model No. of Cylinders Cubic Capacity (litre) Rated Speed (rpm) Governing Power Power rating Cylinder Bore Stroke Length Connecting Rod Length Compression Ratio Swept Volume Overall Dimensions

Water-Cooled Engine TV1 1 0.661 1500 Class “A2/B1” 5.20 kW 7 hp. 87.50 mm 110.00 mm 234 mm 17.50 661.45 cc 617 × 504 × 877 (Length × Width × Height)

IUPAC Name

Tetradecanoic acid Hexadecanoic acid Hexadec-9-enoic acid Octadecanoic acid Octadec-9-enoic acid 9,12-Octadecanoic acid 9,12,15-Octadecanoic acid Icosanoic acid Eicos-11-enoic acid Docosanoic acid Tetracosanoic acid

Composition (%) WCO

B100

0.22 6.81 0.36 3.20 36.04 50.90 0.07

0.26 7.7 0.49 3.5 32.32 53.25 0.06

0.27 0.29 1.36 0.48 12.34 87.66

0.28 0.31 1.33 0.50 13.57 86.43

%Uncertainty = ± Square root of(uncertainty of TFC)2 + (uncertainty of BP)2 + (uncertainty of BSFC)2 + (uncertainty of BTE)2 + (uncertainty of CO)2 + (uncertainty of CO2)2 + (uncertainty of HC)2 + (uncertainty of NOx )2 + (uncertainty of EGT)2

Fig. 2. FT-IR spectrum of B100.

+ (uncertainty of SO)2

(1)

B100 is shown in Fig. 2. The sharp peak at 1740 cm−1 can be attributed to the stretching of C]O, typical of esters and thus are common in fatty acid methyl esters (FAME). The same was reported by another researcher [27]. The main spectrum region that allows for chemical discrimination between oil and its respective FAME is in the range 1500–900 cm−1, known as “fingerprint” region. The peak at 1450 cm−1 corresponds to the asymmetric stretching of –CH3 present in the B100. The stretching of O–CH3, represented by the band peak at 1167 cm−1, is typical of biodiesel. The strong peak at 2855 cm−1 and 2922 cm−1 are due to stretching vibration of –CH2– group. A sharp absorption peak at 845 cm−1 is due to rocking of –CH2– group. A weak signal at 3002 cm−1 is due to olefinic group ]C–H which indicates the presence of unsaturated FA in B100. These results are in good agreement with other reported work [28].

%uncertainty = √ ((1.5)2 + (0.2)2 + (1.5)2 + (1)2 + (0.1)2 + (0.5)2 + (0.005)2 + (0.02)2 + (1)2 + (0.1)2) %uncertainty = ±2.60%

3. Results and discussions 3.1. FA composition of WCO/B100 and FT-IR spectra of B100 The FA composition of WCO and B100 are given in Table 3. It was analyzed that, WCO is composed of 12.34% saturated, 36.69% monounsaturated and 50.97% polyunsaturated FA. The high content of Oleic acid results in poor cold flow properties of B100. It was observed that B100 has more unsaturated fatty acids (86.43%) in comparison to soybean (84.36%) and palm (53.46%) biodiesel which pose positive effect on cold flow properties of biodiesel [26]. The FT-IR spectrum of Table 2b Details of AVL Digass 444 N. Parameters CO CO2 HC NOx SO

Range 0–10% vol. 0–20% vol. 0–20,000 ppm 0–5000 ppm 0–100%

Resolution 0.01% vol. 0.1% vol. 1 ppm 1 ppm 0.1%

783

Accuracy 0.01 0.01 ± 15 ppm ± 15 ppm ± 1% full scale reading

% uncertainties ± 0.1 ± 0.5 ± 0.005 ± 0.02 ± 0.1

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3.2. Characterization of nanoparticles

3.4. Effect of additive on test fuels properties

The XRD pattern of the MgO nanoparticles is shown in Fig. 3. A significant peak shift was observed at 43.1° which confirmed the formation of the crystalline MgO nanoparticles (JCPDS PDF No. 4,509,460). The crystalline size of the catalyst was calculated as 20.76 nm using Debye Scherer’s equation. The phase of the material is cubic face centred.

The addition of MgO nanoparticles to biodiesel blends also had an impact on various fuel properties other than CP, CFPP and PP. The effects of MgO nanoparticles on the viscosity, density, MC, oxygen content, CSCT, flash point, fire point and calorific value of B100, B20, B10, B100W30A, B20W30A and B10W30A are listed in Table 4b. The calorific value of B100W30A, B20W30A and B10W30A were improved by 0.81%, 0.7% and 0.63% when compared to B100, B20 and B10 test fuels respectively on 30 ppm addition of the MgO nanoparticles. However, the change of viscosity, density and MC was small. The density and viscosity of B100W30A, B20W30A and B10W30A changed and was within ASTM limit. However, the MC of B100W30A, B20W30A and B10W30A was decreased by average 28.33% when comparing to B100, B20 and B10 test fuels respectively, and were within the limits of standards. Oxygen content in B100, B20 and B10 were 11.1727%, 2.2345% and 1.1172% respectively. It can be seen that, the oxygen content in the B100W30A, B20W30A and B10W30A test fuels was enhanced marginally by addition of MgO nanoparticles, owing to extra oxygen molecule coming from the MgO. From the CSCT, it was observed that all the test fuels displayed the same results. The addition of MgO nanoparticles did bring major change in the flash and fire point of the samples. The fire point and flash point for B100W30A, B20W30A and B10W30A were increased by 2.65% and 5.21% on average than B100, B20 and B10 respectively.

3.3. Effect of additive on cold flow properties Crystallization of the saturated FAME in biodiesel is of noteworthy significance in areas with low surrounding temperatures [29]. Poorer cold flow properties of fuel prompt fuel starvation and operability issues as solidified material block filters and fuel lines. The CP, CFPP and PP are major three parameters which describes the cold flow properties of biodiesel. CP is the temperature at which fuel start forming a cloudy appearance. It is the lowest temperature at which fuel start forming wax/crystal [30]. CFPP is the lowest temperature, expressed in degrees Celsius (°C), at which fuel is no longer filterable in a specified time when cooled under certain conditions [8]. PP is measured as the lowest temperature at which the fuel progresses toward becoming semi-solid and loses flow properties. Thus, it is the measure of the fuel gelling point [30]. In general, CP is higher than the PP. Much research has been taken up on biodiesel to overcome issues identified with low-temperature operability using cold flow improvers like polymers, esters, Lubrizol and diesel conditioners [8,11,12,15,16,31]. Minimal research has been carried out on the utilization of MgO nanoparticles for cold flow improvements of WCO biodiesel and its blends. Therefore, MgO nanoparticles were researched to enhance the cold flow properties of WCO biodiesel. MgO nanoparticles influenced the CP, CFPP and PP of the biodiesel blends, as shown in Table 4a. The effect of MgO nanoparticle in the test fuels showed no significant change on the CP. Instead, were found to inhibit the growth of existing wax crystals thereby improving the CP and PP [31]. MgO nanoparticles had considerable effects on the CFPP and PP of the biodiesel blends. The CP, CFPP and PP of B100, B20 and B10 test fuels were found to be 6 °C, −2 °C, −3 °C; 2 °C, −5 °C, −7 °C and 1 °C, −6 °C, −9 °C respectively. While examining the effect of MgO concentration on the PP of the B100, B20 and B10, it was observed that, as the MgO concentration was increased from 20 ppm to 30 ppm, the PP of the blend improved from −16 °C to −20 °C, from −11 °C to −16 °C and from −9°C to −11 °C for B10, B20 and B100 respectively, as shown in Table 4a. The PP of all biodiesel blends with the MgO nanoparticles addition were diminished. From all the analyzed test samples, the CFPP of the blend improved from −7 °C to −8 °C, from −9 °C to −12 °C and from −11 °C to −15 °C for B100, B20 and B10 respectively, when MgO addition was increased from 20 ppm to 30 ppm. This finding indicates that the experimental result of the present study was comparable to those reported in the literature [17]. Cold flow property also depends on FAME. Cold flow property is good when unsaturated FAME is high [27]. From Table 3 it is quite evident that the B100 contains 86.43% of unsaturated FA, which improves the synergistic effect between MgO nanoparticles and FAME in B100, thereby retarding the aggregation of crystals and inhibiting the formation of larger crystals at a low temperature. Moreover, the published literature has also attributed the improvement in cold flow property of biodiesel by addition of metal additives to the synergistic effect [8]. Increasing the MgO nanoparticles concentration beyond 30 ppm in the biodiesel blends posed a negative impact on the CFPP and PP. These results are in good agreement with the work reported in other literature [9,18,32]. Biodiesel blends with 30 ppm MgO nanoparticles showed better results for the CP, CFPP and PP. Therefore, 30 ppm MgO nanoparticles concentration was used to prepare biodiesel blend B100, B20 and B10 for fuel property testing, performance, combustion and emission studies, which will be detailed in the next section.

3.5. Performance characteristics 3.5.1. Brake specific fuel consumption The important parameter to inspect engine performance is by the comparison of BSFC along with engine load. BSFC usually decreases with increase in load. Density, viscosity, calorific value and volumetric fuel injection are the main factors governing the BSFC requirement of diesel engines [33]. Fig. 4a shows the BSFC values of various test fuels with variation in load on the engine. The maximum amount of BSFC was found with B100W30A (0.49 kg/kW h) and the least was found with PBD (0.35 kg/kW h) at 4.73 kg engine load as compared with other test fuels. When the load on the engine was increased from 4.73 kg to 18.11 kg, the BSFC of all the test fuels decreased simultaneously. Since in-cylinder, air movement improves at low engine load more homogeneous air-fuel mixture can be obtained [34]. This enhancement in the air-fuel mixture formation might be effective on the decrease of BSFC values with higher engine load. The mean BSFC of PBD was 10.37%, 9.43%, 7.54%, 41.5%, 19.81% and 10.18% less than the B100, B20, B10, B100W30A, B20W30A and B10W30A respectively. This is because PBD fuel is less dense than other test fuels. As BSFC is calculated on a weight basis, higher density will lead to higher BSFC. In the same way, other

Fig. 3. XRD pattern of MgO nanoparticles.

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fuels. Mean BTE of PBD, B100W30A, B20W30A, B10W30A, B100, B20 & B10 were 28.78%, 28.50%, 28.17%, 27.72%, 27.40%, 26.85% & 26.45% respectively. The B100 showed the least average BTE (27.4%). The maximum amount of BTE for PBD fuel was 34.3% at 13.41 kg engine load. The PBD fuel has low viscosity, density and high calorific value. The low viscosity and density of PBD fuel leads to increase in fuel atomization, evaporation and combustion, thereby increasing the BTE. This types of phenomena were observed by other researcher [38]. When analyzing the BTE of nanoparticles blended biodiesel, it was found that the average BTE of B100W30A, B20W30A and B10W30A were 4.01%, 4.91% and 4.8% higher than the B100, B20 and B10 fuel respectively. This could be probably due to the effect of secondary atomization along with the presence of potential nanoparticles, as shown in Fig. 5. Moreover, the nanoparticles in general, possess an enhanced surface area and reactive surfaces which lead to higher chemical reactivity to act as a catalyst [39]. Under these circumstances, the BTE of nanoparticles blended biodiesel fuels is improved.

Table 4a CP, CFPP and PP of the test fuels. Sample

B100

B20

B10

MgO nanoparticles Concentration (ppm)

0 20 30 40 50 0 20 30 40 50 0 20 30 40 50

Test Method ASTM D2500

ASTM D-97

ASTM D6371

CP (°C)

PP (°C)

CFPP (°C)

6 3 4 5 8 2 −2 5 10 3 1 −1 −3 −3 −4

−3 −9 −11 −5 −8 −7 −11 −16 −3 −11 −9 −16 −20 −18 −15

−2 −7 −8 −4 −6 −5 −9 −12 −2 −9 −6 −11 −15 −14 −11

3.5.3. Brake power The engine BP of test fuels at different engine load condition is shown in Fig. 4c. It is seen from the figure that the engine BP of all fuels gradually increased with increase in load. The maximum power output for PBD fuel was measured at 5.75 kW at an engine load of 18.11 kg. The average BP of PBD were 11.69%, 9.26%, 11.35%, 11.08%, 8.92%, and 9.12% higher than those of B100, B20, B10, B100W30A, B20W30A and B10W30A respectively. A lower amount of average BP (2.612 kW) was found with B100. The higher BP of PBD fuel is due to its low viscosity and high calorific value. The combustion takes place more efficiently in the combustion chamber leading to rise in BP and found to be in agreement with other reported work [40,41]. When comparing BP of nanoparticles blended biodiesel fuel with biodiesel blends it was analyzed that, average BP of B100W30A, B20W30A and B10W30A has 0.68%, 0.37% and 2.45% more BP compared to B100, B20 and B10 respectively. This could be due to the existence of MgO nanoparticles in the biodiesel fuel [19]. This could have improved surface area and sufficient fuel could have built up in the combustion chamber leading to enhancement of the air–fuel mixture formation. Secondly, high viscosity and density of nanoparticles blended fuel can reduce the pump leakage and thereby increase BP [19].

literature reported that a higher density of fuel leads to higher fuel flow rate, thereby increasing BSFC [35]. When comparing BSFC of nanoparticles blended biodiesel fuel, it was analyzed that BSFC of B100W30A, B20W30A and B10W30A has 28.2%, 9.48% and 2.45% more BSFC (on average 13.37%) compared to B100, B20 and B10 respectively. It is observed that the BSFC has improved for the nanoparticles blended biodiesel fuels compared to that of B100, B20 and B10. This could be due to the existence of MgO nanoparticles in the biodiesel fuel. Owing to the enhanced surface area and shortened ignition delay characteristics of nanoparticles, sufficient fuel could have built up in the combustion chamber to undergo a possible catalytic effect in the unit volume of the fuel during the combustion [36]. Secondly, nanoparticles blended test fuels density is more than the B100, B20 and B10 therefore, the same fuel consumption on volume basis resulted in higher specific fuel consumption in this case. So higher densities of nanoparticles blended fuel lead to higher mass injection for the same volume of fuel in the combustion chamber, leading to increase in BSFC.

3.6. Exhaust emissions characteristics

3.5.2. Brake thermal efficiency The BTE is defined as the ratio between the actual brake work produced by the engine and the energy delivered to the engine with the fuel and is a critical parameter regarding determining the effects of various fuels on the engine performance [37]. The major parameter for testing engine performance is by the comparison of BTE with engine load. Fig. 4b shows that the BTE of all test fuels increased as the engine load was increased. All test fuels showed higher BTE at 18.11 kg engine load. The BTE of PBD fuels were slightly higher than those of other test

In this segment of the study, the changes in the exhaust emissions with engine load are discussed. The various exhaust parameters studied are carbon monoxide (CO), carbon dioxide (CO2), hydrocarbon emission (HC), oxides of nitrogen (NOx), smoke opacity (SO) and exhaust gas temperature (EGT). 3.6.1. Carbon monoxide emissions Incomplete combustion of fuel results in the increased emission of

Table 4b Properties of test fuels. Property

Density (27 °C)

MC

Kinematic Viscosity (40 °C)

Oxygen Content

Calorific Value

Flash Point

Fire Point

Unit Test Method

CSCT (3 h, 60 °C) Degree of corrosivity ASTM D-130

(g/cc) –

% ASTM D-2709

(cSt) ASTM D-445

% –

(kJ/kg) ASTM D-240

(°C) ASTM D-93

(°C) –

B100 B20 B10 B100W30A B20W30A B10W30A (ASTM) D6751-07 (2007)

1A 1A 1A 1A 1A 1A No. 3 Max.

0.874 0.826 0.816 0.883 0.829 0.817 0.878

0.020 0.010 0.008 0.012 0.008 0.006 0.050 max.

3.23 2.67 2.43 3.26 2.69 2.44 1.9–6.0

11.1727 2.2345 1.1172 11.1738 2.2356 1.1184 –

25817.69 29594.09 32950.78 26027.49 29803.94 33160.74 –

150 98 76 154 103 82 130 min.

160 109 90 163 112 93 53 min.

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Fig. 4. Effects of engine load on (a) BSFC, (b) BTE, (c) BP.

content as compared to B100, B20 and B10, due to this, the nanoparticles blended biodiesel undergoes better combustion when compared to B100, B20 and B10 [44]. 3.6.2. Carbon dioxide emissions Complete combustion of the air fuel mixture is characterized by higher percentage of CO2 in the emission. CO2 is one of the basic greenhouse gases, which get released into the atmosphere along with the other exhaust gases [45]. CO2 does not harm the atmosphere as much as compared to CO since plants take it for its survival. CO2 emissions measured as a function of the engine load for the test fuels are plotted in Fig. 6b. As seen in the figure, CO2 emissions of all test fuels increased slightly with the increasing engine load. When the load on the engine was increased from 0 kg to 18.11 kg, CO2 emission increased from 21.14 g/kWh to 114.63 g/kWh, from 22.49 g/kWh to 114.89 g/kWh, from 23.3 g/kWh to 118.94 g/kWh, from 21.95 g/kWh to 111.12 g/kWh, from 22.62 g/kWh to 112.6 g/kWh, from 22.76 g/ kWh to 116.51 g/kWh and from 20.2 g/kWh to 96.98 g/kWh for B100, B20, B10, B100W30A, B20W30A and B10W30A and PBD respectively. This increasing trend in CO2 emissions with increasing load might be caused by the decrease in BSFCs of test fuels as seen in Fig. 4a. The average CO2 emitted by PBD was 17.85%, 18.85%, 20.21%, 16.86%, 17.45% and 19.64% less (on average 18.47%) when compared to B100, B20, B10, B100W30A, B20W30A and B10W30A respectively. The higher CO2 emissions of biodiesel fuels may be attributed to their higher carbon and oxygen contents which improve the combustion quality causing an increase in CO2 concentration when compared to PBD [46]. When examining the average percent CO2 emissions of nanoparticles blended biodiesel to B100, B20 and B10 at 100% load, it is realized that B100W30A, B20W30A and B10W30A emitted 1.12%,

Fig. 5. Secondary atomization effect.

carbon monoxide. Insufficient supply of oxygen, inefficient mixing of air fuel mixture, deficiency of time and oxygen concentration required for oxidizing the CO to CO2 are three major factors leading to incomplete combustion [42]. Fig. 6a illustrates CO emissions of all test fuels at full load condition. The high CO emissions for all test fuels at 100% engine load might be interpreted as the result of the inefficient mixing of air and fuel due to low turbulence, large fuel droplets from injectors resulting from poor atomization, long penetrations of the large fuel droplets inside the combustion chamber resulting in formation of locally fuel-rich zones. The lowest amount of CO emissions were produced by B100W30A and the maximum amount of CO was emitted by PBD. Moreover, PBD emitted 52.77%, 38.88%, 27.77%, 55.55%, 50% and 44.44% more CO than B100, B20, B10, B100W30A, B20W30A and B10W30A respectively. Biodiesel blends have higher oxygen content than PBD, which can complete better combustion and reduce CO emissions [43]. When comparing the nanoparticles blended fuels to other test fuels, it is realized that B100, B20 and B10 emitted 5.88%, 18.18% and 23.07% more CO emission (15.71% on average) when compared to B100W30A, B20W30A and B10W30A at 100% load, respectively. The higher air–fuel ratios of nanoparticles blended biodiesel over biodiesel blend could be a reason to impact the CO emission. Moreover, from Table 4b the nanoparticles blended test fuels have higher oxygen 786

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Fig. 6. variation in (a) CO, (b) CO2, (c) HC, (d) NOx, (e) SO for different test fuels.

3.6.3. Hydrocarbon emissions HC is emitted due to incomplete combustion of fuel in the combustion chamber. The structure/composition of the fuel, construction of the engine operating conditions are crucial parameters that affects HC emissions [42]. Fig. 6c shows the change in HC emissions for different test fuels. The

1.7% and 0.71% less CO2 emission (1.2% on average) as compared to B100, B20 and B10 respectively. This can be attributed to the enhanced catalytic activity of MgO nanoparticles present in the biodiesel fuel, which has led to shortened ignition delay. Due to this effect, there is an improvement in the air-fuel mixture in the combustion chamber, leading to complete combustion [44].

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will generate more NOx. Moreover, the WCO biodiesel has the presence of unsaturated fatty acid, which will increase the NOx emissions [50]. The results obtained is found to be in accordance with the previously reported work [46,50]. When analyzing the average NOx emissions of nanoparticles blended biodiesel to B100, B20 and B10, it is noticed that B100W30A, B20W30A and B10W30A emitted 4.06%, 2.13% and 1.83% lesser NOx (2.67% on average) when compared to B100, B20 and B10, respectively. This can be attributed to the fact that the metals associated with the nanoparticles function either by reacting with water to produce hydroxyl radicals, which enhance soot oxidation or by direct reaction with the carbon atoms in the soot, thereby lowering the oxidation temperature and subsequent decrease in NOx emissions. Higher latent heat of vaporization and lower heat value of test fuels without additive results in higher volume of fuel injection consequently cylinder charge temperature and combustion temperature fall and NOx emissions shrink [51]. Moreover, B100W30A emitted more NOx when compared to B20W30A and B10W30A because the exhaust gas temperature is also the important factor for NOx formation. So, decrease exhaust gas temperature (Table 5) caused by higher latent heat of vaporization of B20W30A and B10W30A test fuels led to reduce NOx emissions.

Table 5 Exhaust Gas Temperature values in °C for the tested fuels at different engine load conditions. Engine Load Condition (%)

Test Fuels

PBD B10W30A B20W30A B100W30A B10 B20 B100

0

25%

50%

75%

100%

169 174 178 185 175 180 190

200 205 212 219 210 213 225

256 260 267 271 265 270 279

320 325 330 346 325 338 345

368 375 380 395 385 390 408

HC emissions was found to be 0.0182 g/kWh, 0.01 g/kWh, 0.0162 g/ kWh, 0.0141 g/kWh, 0.0081 g/kWh, 0.0121 g/kWh and 0.1273 g/kWh for B100, B20, B10, B100W30A, B20W30A, B10W30A and PBD respectively at 100% engine load. At high load conditions, high HC emission is observed; this is because at high load to maintain the uniform engine speed the requirement of fuel is more. As a result of this fuel is injected into the combustion chamber rapidly. The injected fuel cannot be oxidized or is partially oxidized resulting in decreased combustion duration leading to increased HC emission. Secondly, the high HC emission of PBD fuel, when compared to other test fuels, can be attributed to the higher C/H ratio of PBD. Moreover, PBD emitted on an average 89.68% more HC than B100, B20, B10, B100W30A, B20W30A and B10W30A respectively. Biodiesel blends and nanoparticles blended biodiesel have higher oxygen content than PBD and hence undergo enhanced combustion with reduced HC emissions [43]. While correlating the HC emissions of B100, B20, and B10 to B100W30A, B20W30A and B10W30A, it is realized that B100, B20, and B10 emitted 22.52%, 19% and 25.30% more HC emission (22.27% on average) as compared to B100W30A, B20W30A and B10W30A at 100% load, respectively. In the case of nanoparticles blended biodiesel fuels, the degree of air-fuel mixing could have improved, on account of secondary atomization and improved catalytic effect associated with the dispersion of nanoparticles in the biodiesel fuels [44].

3.6.5. Smoke opacity The SO indirectly indicates the soot content in the exhaust gasses. Smoke opacity is due to the presence of particulate matters, oxygen content, aromatic compounds, and sulfur content in the exhaust gas [52]. The particulate matter includes CO, CO2, NOx and other greenhouse gases. The more the content the opaque the smoke is. The opacity of the smoke decides the level of contamination of the atmospheric air. Fig. 6e illustrates the variations of SO for test fuels at different load conditions. As seen in the figure, SO showed similar trends for all test fuels. As the load on the engine was increased from 0 kg to 18.11 kg, SO increased due to the lower oxygen content coming from, the lower air to fuel ratio. To maintain uniform speed at higher load conditions the fuel requirement increases. Thus, more and more fuel flow in the combustion chamber, resulting in incomplete combustion. The partially oxidized fuel produces more particulate matter thereby increasing the smoke density [53]. The average smoke opacities of PBD were 24.36%, 12.57%, 21.11%, 25.57%, 20.39%, and 23.88% higher than those of B100, B20, B10, B100W30A, B20W30A and B10W30A, respectively. B100W30A produced the lowest average smoke opacity compared with other test fuels at approximately 24.74%. This can be attributed to the fact that biodiesel contains more oxygen as compared PBD and cetane number of biodiesel is better than diesel. The extra oxygen in biodiesel enhances the combustion process. While correlating SO of nanoparticles blended biodiesel with B100, B20 and B10, it is observed that B100W30A, B20W30A and B10W30A smokes were 1.59%, 8.94% and 3.5% less opaque (on average 4.68%). The MgO nanoparticles blended biodiesel fuels also show a similar characteristic trend as that of biodiesel fuel, with further reductions in smoke opacity. The addition of nanoparticles to the biodiesel fuel has imparted shorter ignition delay. Due to the above effect associated with the nanoparticles blended biodiesel fuels, an ample fuel could have been induced in the combustion chamber before ignition, leading to better combustion, air-fuel mixing and, in turn, resulting in reduced smoke emissions.

3.6.4. NOx emissions Nitric oxide (NO) and nitrogen dioxide (NO2) are usually combined as NOx. Diesel engines release more amounts of oxides of nitrogen than the engines which run on petrol and other fuels because the combustion in diesel engine takes place at temperatures higher than 1800 K. Temperature, oxygen concentration and combustion duration are three important parameters which affect the NOx formation [47]. Combustion chamber type and shape, compression ratio, injection timing and pressure, the start of combustion and its duration and the physicochemical characteristics of fuel such as viscosity, density and cetane number also influence NOx emissions from internal combustion engines [48]. NOx emissions of the test fuels and their variations with the engine load were determined as given in Fig. 6d. As seen in the figure, NOx emissions show similar trends for all test fuels. As the load on the engine was increased from 0 kg to 18.11 kg, NOx emissions increased. This may be due to the higher oxygen content coming from, the higher air fuel ratio. The average NOx emissions of PBD were 14.09%, 15.46%, 17.01%, 10.45%, 13.62%, and 15.46% lower (14.35% on average) than those of B100, B20, B10, B100W30A, B20W30A and B10W30A, respectively. Biodiesel has a high oxygen content than diesel fuel, approximately 12% higher [46]. Higher NOx emissions are because of the pure ester property of biodiesel. When cetane number is high, it leads to shorter ignition delay [49]. Increasing cetane number reduces the size of the premixed combustion by reducing the ignition delay, thereby allowing less time for mixing of air-fuel. Consequently, the weak air-fuel mixture

3.6.6. Exhaust gas temperature The exhaust gas temperature (EGT) indicates the effective use of the heat energy of the fuel. The heat loss in the exhaust pipe or rise in the exhaust temperature reduces the conversion of heat energy to work. Higher exhaust gas temperature values are indicating the deprived heat energy utilization by the engine, in other ways it indicates lower thermal efficiency [48]. Table 5 shows a comparison of the EGT values obtained for the fuels tested over the varying load condition. It is 788

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when compared to other test fuels. The maximum cylinder pressure of B100 and B100W30A were 1.94% and 0.79% less than the PBD, respectively. Table 6b summarizes the maximum in-cylinder pressures (Pmax) and the crank angle at which these pressures were attained (°CAPmax). For 100% engine load, Pmax of PBD fuel was higher than those of other test fuels. The other interpretation can be made that when increasing the volumetric percentage of biodiesel in test fuel the cylinder pressure increases, which is due to the decrease in ignition delay with increase in the percentage of biodiesel in test fuels resulting in earlier combustion consequently leading to higher peak pressures. The above result was in good agreement with other reported work [53]. Furthermore, nanoparticles blended biodiesel blends showed higher peak cylinder pressure than other biodiesel blends. The maximum cylinder pressure of B100W30A, B20W30A and B10W30A were 1.16%, 0.346% and 0.315% more (on average 0.27%) than the B100, B20 and B10 respectively. This could be due to the presence of nanoparticles in the fuel which has lead to a shortened ignition delay leading to early combustion, and improved ignition characteristics [36].

evident from the EGT values that the amount of EGT is just reversal of the amount of brake thermal efficiency (BTE) at a particular load. By comparing all the EGT values, PBD has lower EGT value than the other test fuels. The B100W30A, B20W30A and B10W30A blends are having slightly lesser EGT values than their counterparts at all loads. The MgO nanoparticles content in biodiesel provides better combustion reducing the exhaust temperatures when compared to the B10, B20 and B100. Simultaneously, the biodiesel blends produced higher EGT values than PBD which may be assumed to be due to higher viscosity and poor volatility leading to insufficient mixture development. Hence, diffusion combustion is more governing which lengthens the heat release progression leading to higher exhaust gas temperature, particulate smoke opacity and NOx emissions [18,35]. 3.7. Combustion characteristics 3.7.1. Combustion efficiency Combustion efficiency is a measurement of the extent by which the fuel being burned is being utilized in the combustion process. The combustion efficiency was calculated in accordance with the equation (Eq. (2)) by using the enthalpy of formation of the experimental emissions [54].

ηcom =

LHVfuel−HNO NO−HNO2 NO2−HCO CO−LHVfuel HC LHVfuel

∗100

3.7.3. Heat release rate and crank angle The heat release rate of test fuels with varying crank angle at full load condition is shown in Fig. 7b. From the heat release rate plot it is evident that heat release rate gradually increases during the primary stage of combustion because of vaporization of the fuel accumulated during the ignition delay; when combustion is initiated, the heat release rate rapidly becomes positive [41]. From the heat release rate analysis, the peak heat release rate was determined as 65.74 kJ/°CA with PBD fuel at 360°CA. This may be due to higher volatility of diesel and its ability to mix with air [52]. Fig. 7b shows that B100 exhibited a lower peak heat release rate (49.17 kJ/°CA) than those of B100WA. Fig. 7b shows that the B20 and B20W30A fuels displayed peak heat release rates of 54.32 kJ/°CA and 53.49 kJ/°CA, at 369°CA and 372°CA ATDC respectively; these rates are approximately 17.37% and 18.63% lower, respectively than the that of the PBD fuel. Overall the PBD fuel showed higher heat release rate than other test fuels. These results can be attributed to the low density, low viscosity and high calorific value of the PBD. Therefore, this condition may cause rapid vaporization of the PBD, thereby contributing to premixed combustion. Another observation from the peak heat release rate plot is that the B100W30A, B20W30A and B10W30A showed less heat release than B100, B20 and B10 fuel. This trend may also be attributed to the higher density and viscosity (Table 4b) of the nanoparticles blended fuel due to which, the vaporization of fuel is slow thereby, imparting a negative effect on the heat release rate.

(2)

where ƞcom is the calculated combustion efficiency, LHVfuel is the net calorific value of the fuel, HNO, HNO₂ and HCO are the enthalpies of formation of NO, NO2 and CO respectively. NO, CO, NO2 and HC are the exhaust emission levels of NO, CO, NO2 and HC respectively. Combustion efficiency of various test fuels is tabulated in Table 6a. The engine BTE and combustion efficiency values increased with increase in the biodiesel content in the blends due to the increasing oxygen content in the biodiesel blends. The more oxygen in the blend more is the BTE and the combustion efficiency. Also, combustion efficiency is observed to improve slightly with increase in the engine load as higher loads lead to better volumetric efficiency and good atomization rate [54]. 3.7.2. Cylinder pressure and crank angle Cylinder pressure of an engine varies throughout the four-stroke engine cycle. Work is done on the fuel by the piston during compression, and the gases produce energy through the combustion process. The pressure change in the cylinder of an engine affects the start of injection (SOI) timing, ignition delay (ID) and the start of combustion (SOC). Fig. 7a shows the changes in the cylinder pressure of the test fuels with varying crank angle (CA) under at full load condition. For combustion analysis, the peak cylinder pressure is correlated with the crank angle. Biodiesel possesses lower peak cylinder pressure because of the long ignition delay [53]. Fig. 7a indicates that PBD exhibited a maximum cylinder peak pressure of 64.29 bar at 371°CA after top dead center (ATDC), whereas the minimum cylinder peak pressure was 63.23 bar at 372°CA ATDC with the B10 fuel. This can be attributed to the low viscosity of PBD, due to which the flow of fuel will be smoother and result in enhancing the fuel-air ratio and building more cylinder pressure. Moreover, earlier ignition of PBD results in the early start of combustion and hence higher pressure values for PBD was observed

4. Conclusions

• CP, CFPP and PP of the biodiesel fuel were significantly improved

•

with the addition of MgO nanoparticles. The 30 ppm concentration of MgO nanoparticles was optimum for the improvement in CFPP and PP. There was no significant variation in density, viscosity and moisture content of the biodiesel blend, due to the addition of MgO nanoparticles. The CSCT of the test fuels remains unchanged after the addition of MgO nanoparticles. The fuel properties of all test fuels met the ASTM standards. Nanoparticles blended test fuels had higher BSFC, BTE and BP than

Table 6a Combustion efficiency of test fuels at 100% and 50% load condition.

100% LOAD 50% LOAD

BTE% Combustion Efficiency% BTE% Combustion Efficiency%

PBD

B100 W30A

B20W30A

B10W30A

B10

B20

B100

33.81 99.45 28.50 97.55

33.20 98.65 28.50 97.5

32.60 98.25 28.20 97.25

32.20 99.25 27.60 96.55

31.80 98.5 27.30 96.25

31.20 98.56 26.80 95.75

30.80 98.35 26.40 95.25

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Fig. 7. Relationship between CA and (a) cylinder pressure, (b) heat release rate.

Table 6b Pmax, °CAPmax, HRRmax and °CA Test Fuels

B100 B20 B10 B100W30A B20W30A B10W30A PBD

•

• •

HRRmax

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for test fuels.

100% load Pmax (bar)

°CAPmax (ATDC)

HRRmax (kJ/°CA)

°CA HRRmax (ATDC)

63.04 63.29 63.23 63.78 63.51 63.43 64.29

372 371 372 372 371 373 371

49.17 54.32 52.39 45.83 53.49 51.97 65.74

370 369 370 372 372 371 358

B100, B20 and B10. B100W30A, B20W30A and B10W30A emitted less CO and HC, but more CO2 emissions than B100, B20, B10 and PBD. NOx emissions of the B100W30A, B20W30A, B10W30A, B100, B20 and B10 were more than PBD. B100W30A, B20W30A and B10W30A smoke were less opaque, on average 4.68% when compared to B100, B20 and B10. B100W30A, B20W30A and B10W30A showed high peak cylinder pressure and lesser heat release rate than B100, B20 and B10. As a result of the study, the MgO nanoparticles at 30 ppm concentration can be used as additives for the biodiesel to improve cold flow properties, performance and combustion characteristics and to decrease exhaust emissions when used in diesel engines.

Acknowledgements The authors thank, Ministry of Human Resource Development, Government of India for funding the research work (Award No. 5-5/ 2014-TS.VII 4th September 2014). The authors thank Mr. Vishwanathan E. (Junior Research Fellow, Physics Department (DSTFIST sponsored), Sathyabama Institute of Science and Technology) for FT-IR analysis. References [1] Singh SP, Singh D. Biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: a review. Renew Sustain Energy Rev 2010;14:200–16. http://dx.doi.org/10.1016/j.rser.2009.07. 017. [2] Khalife E, Tabatabaei M, Demirbas A, Aghbashlo M. Impacts of additives on performance and emission characteristics of diesel engines during steady state operation. Prog Energy Combust Sci 2017;59:32–78. http://dx.doi.org/10.1016/j.pecs. 2016.10.001.

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