Combustion, Performance, and Emission Study of a Research Diesel


Combustion, Performance, and Emission Study of a Research Diesel...

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Combustion, Performance, and Emission Study of a Research Diesel Engine Fueled with Palm Oil Biodiesel and Its Additive Yuvarajan Devarajan,*,† Arulprakasajothi Mahalingam,† Dinesh Babu Munuswamy,‡ and T. Arunkumar§ †

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Department of Mechanical Engineering, Vel Tech Rangarajan Dr. Sagunthala R&D Institute of Science and Technology, Chennai 600062, India ‡ Department of Mechanical Engineering, Panimalar Engineering College, Chennai 600123, India § Department of Mechanical Engineering, Sathyabama R&D Institute of Science and Technology, Chennai 600119, India ABSTRACT: More requirements for diesel fuel and a huge rise in air pollution, owing to the surplus usage of diesel fuel, give us a prospect to discover environmentally friendly and clean fuels for the existing unmodified diesel engines. The present work is aimed to analyze the combustion, performance, and emission characteristics of a neat palm oil biodiesel (POBD)-fueled diesel engine with silver oxide (Ag2O) as a additive in various mass fractions (5 and 10 ppm), and the results are compared to conventional diesel. Experiments were conducted in a natural aspirated, two-cylinder diesel engine at a constant speed and compression ratio of 2400 rpm and 17:1, respectively. Ag2O was added with neat POBD using an ultrasonicator. The experimental investigation on the diesel engine reveals that the addition of Ag2O nanoparticles to palm oil mill effluent (POME) resulted in enhancement in ignition characteristics because of the enhanced surface area/volume ratio. In addition, the addition of Ag2O nanoparticles to POME resulted in enhancement in brake thermal efficiency with a reduction in brake specific fuel consumption. The experimental results also show that the Ag2O nanoparticles promote an improved level of hydrocarbon, carbon monoxide, smoke, and nitrogen (NOx) emissions. van18 conducted a research work on adding metal oxides [at different parts per million (ppm)] to neat BD in a compression-ignition (CI) engine. Results showed a notable drop in all emissions than diesel. Venkata Ramanan and Yuvarajan19 studied a emission study on adding ferrofluid to neat rice bran BD. A significant reduction of HC, carbon monoxide (CO), NO, and smoke emissions was obtained by adding ferrofluid to neat rice bran BD. Yuvarajan et al.20 investigated the effect of nanoadditives (titanium dioxide) in mustard BD and found a considerable reduction in fuel consumption and a significant reduction in all of the emissions. Many investigations have employed palm BD as a prospective candidate as a possible option fuel to diesel. Devarajan et al.21 investigated the engine output parameters of a diesel engine using palm BD and found that 100% of palm BD can be fed as fuel. Joy et al.22 investigated the engine output parameters using various blends of palm oil methyl ester, and their results have shown a significant improvement in thermal efficiency with lower fuel consumption. Further, CO, HC, and NOx are reduced by blending palm oil methyl ester with diesel. An in-detail review of the previous study has shown a space in accomplishing the addition of palm oil biodiesel (POBD) with a silver oxide (Ag2O) nanoparticle in a CI engine application. Thus, this study analyzes the effect of a Ag2O nanoparticle with POBD and employs it in an unmodified CI engine. However, the removal of the nanoparticle after combustion is in the future scope of research.

1. INTRODUCTION Rapid growth in the automobile sectors has ended in higher fuel consumption and greater emissions from engines. Specifically, engines using fossil fuels liberate a higher amount of hydrocarbon (HC) and carbon dioxide (CO2) emissions.1 HC, CO, NOx, and CO2 are the major sources of global warming. From 1975 to 2005, the greenhouse gas emissions increased by 1.5% every year, while CO2 emissions from petroleum products were found to increase by 1.9% every year. Agricultural, power generation, and transportation sectors rely on internal combustion engines. Hence, extensive research in diesel and gasoline is essential for emission reduction and enhancement in efficiency. Even a minimal reduction in emission will have an immense impact on pollution. Alternative fuels cause environmental preservation, sustainable development, and energy conservation. Biodiesel reduces all of the emissions from diesel engines.2 The non-toxic nature, biodegradability, inherent lubricity, and higher flash point are some of the major benefits of biodiesel (BD).4 However, high viscosity and poor atomization of BD cause higher NOx emissions and lower efficiency.3 Many authors have agreed to the reductions in pollutant emissions and comparable performance when diesel engines run by BD or its blends with the raise in NOx.5−8 Many investigations have proven that adding additives (metal-based) in powder form to BD facilitates as a catalyst in boosting the engine combustion and performance and improves its fuel properties.9−16 Nanoadditives alter the chemical composition of BD and enhance the oxidation characteristics. Nanoadditives also aid the engine combustion and performance characteristics of fuel.17 Venu and Madha© XXXX American Chemical Society

Received: March 31, 2018 Revised: June 29, 2018

A

DOI: 10.1021/acs.energyfuels.8b01125 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels

2. MATERIALS AND METHODS

Table 2. Specification of the Experimental Setup

2.1. Test Fuel Preparations. The silver nanoparticle was procured from Reinste Nano Ventures. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images of the silver nanoparticle dispersed to BD are shown in Figure 1. The

stroke cylinder rated power (kW) rated speed (rpm) bore diameter, D (mm) stroke, L (mm) load type cubic capacity (cm3) pressure sensor compression ratio injection timing (deg BTDC) injection pressure (bar) cooling system combustion

Figure 1. SEM and TEM images of Ag2O nanoparticles. raw palm oil procured from the local market is processed via transesterification to minimize its viscosity. A magnetic stirrer with a hot plate was used for the transesterification reaction. The collected raw palm oil is preheated to 80 °C to remove the moisture content associated with it. Sulfuric acid (H2SO4) is used for acid pretreatment to lower the free fatty acid (FFA) content of the palm oil. In an acid pretreatment step, an addition of 0.6% (v/v) H2SO4 of raw palm oil with a molar ratio of 1:5 oil/alcohol, reaction temperature of 65 °C, reaction speed of 550 rpm, and reaction time of 75 min was obtained as the optimum condition for esterification. Table 1 shows the properties of POBD + Ag2O (5 and 10 ppm), POBD, and diesel. An ultrasonicator with a frequency of 60 kHz and 440 W was employed to disperse the silver nanoparticle to BD. It was found that the silver nanoparticle was found stable in POBD. 2.2. Experimental Setup. In this study, the experiments were carried out in a naturally aspirated, two-cylinder, four-stroke, and direct injection (DI) diesel engine with a rated power of 9 kW at 2400 rpm. The engine technical specifications of the experimental setup are tabulated in Table 2. The experimental setup consisted of an engine, a dynamometer, a fuel supply system, a data acquisition unit, an emission analyzer, and a smoke opacimeter. The AVL emission analyzer was employed to measure HC, NOx, and CO emissions. The AVL 437C model opacimeter was employed to measure smoke opacity. The entire experiment was carried out at a constant speed of 1500 rpm by varying the load. The engine is made to warm up for 30 min after feeding each fuel blend to attain the static operating conditions. Uncertainty of all measured values was evaluated by the square root method and shown in Table 3.

4 2 9 2400 85 100 eddy current dynamometer loading 567 piezo sensor, 4999 psi range 17:1 21 260 water direct injection

Table 3. Accuracy and Uncertainty of Instruments model of gas analyzer measured quantity CO HC NOx smoke cylinder pressure crank angle performance BTE

3. RESULTS AND DISCUSSION This section details the variation of emission and combustion attributes of the engine at the partial and full loads for various fuel blends. 3.1. In-Cylinder Pressure Variation. The in-cylinder pressure variations for the tested fuels are depicted in Figure 2. The diesel engine produces a similar in-cylinder pressure pattern for all test fuels. The peak pressure for POBD and diesel is 81.18 and 79.12 bar. Because the viscosity of diesel is lower than that of POBD, the ignition delay of diesel is shortened and results in uniform combustion and lower peak

AVL gas analyzer range 0−5000 ppm 0−19999 0−4999 ppm AVL 437 smoke meter 0−250 bar 0−360°

accuracy 0.02% ±10 ppm ±10 ppm 0.01% ±0.1 bar ±1°

uncertainty ±0.5 ±0.1 ±0.3 ±1.0

(%) (%) (%) (%)

±0.1 ±0.2 absolute relative ±0.01% ±1

Figure 2. Variation of in-cylinder pressure for tested fuels.

Table 1. Properties of Tested Fuels property

POBD

POBD + Ag2O (5 ppm)

POBD + Ag2O (10 ppm)

diesel

density at 15 °C (g/cm3) kinematic viscosity at 40 °C (mm2/s) calorific value (kJ/kg) flash point (°C) cetane number

0.801 3.85 39385 146 53

0.813 3.91 39746 142 55

0.818 3.97 40017 139 57

0.820 2.4 42957 50 48

B

method ASTM ASTM ASTM ASTM ASTM

D4052 D445 D240 D976 D613

DOI: 10.1021/acs.energyfuels.8b01125 Energy Fuels XXXX, XXX, XXX−XXX

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Energy & Fuels pressure.21,23 The other reason for the lower peak pressure for diesel is due to its higher calorific value. Fuel with a higher calorific value requires a lesser quantity of fuel during combustion.21,24 It is observed that adding 5 and 10 ppm of Ag2O nanoparticles to POME observes a considerable increase in the peak pressure. The thermal conductivity of the fuel mixture is increased upon the addition of Ag2O nanoparticles to POBD.19,20 As a result of higher thermal conductivity, the combustion is initiated early, causing a higher peak pressure. Further, the combustion starts early for POBD with an increase in the content of the Ag2O nanoparticle.25 This is due to the improved ignition quality and higher thermal conductivity of the Ag2O nanoparticle.25 These results match with many studies21−25,33,36,39 that reported a similar pressure variation of the diesel engine fueled with the BD and nanoparticle mixture. 3.2. Heat Release Rate (HRR). The variation in the HRR for the tested fuels is shown in Figure 3. The maximum HRRs

Figure 4. Effect of Ag2O nanoparticles on the BTE with BP for tested fuels.

atomization of fuel as a result of the presence of nanoparticles has promoted the combustion process and improved BTE.18,19 In addition, BTE for POBD + Ag2O (10 ppm) is considerably higher than that for POBD + Ag2O (5 ppm) at all conditions. The catalytic activity of nanoparticles enhances the heat transfer with an increase in the Ag2O nanoparticle content (5− 10 ppm), which results in improved combustion and higher BTE.27,28,33,36,38 These results match with many studies24−28 that reported a higher BTE of the diesel engine fueled with the BD and nanoparticle mixture. BTE at peak conditions for diesel, POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is 29.8, 26.6, 27.7, and 28.2%, respectively. 3.4. Brake Specific Fuel Consumption (BSFC). Figure 5 depicts the change in BSFC of POBD, POBD + Ag2O (5

Figure 3. Variation of the HRR for tested fuels.

for POBD and diesel are 81.18 and 92.98 J/° crank angle (CA). The possible reason for the higher HRR for diesel is due to its higher calorific value. Fuel with a higher calorific value produces more quantity of heat during combustion.21 Adding 5 and 10 ppm of Ag2O nanoparticles to POME observes a considerable increase in the HRR. This is due to the higher surface area/volume ratio of Ag2O nanoparticles, which results in improved combustion, a reduced delay period, and a higher HRR.22,23 Further, the HRR raises for POBD with an increase in the content of Ag2O nanoparticles. This is due to their improved ignition quality and higher thermal conductivity of Ag2O nanoparticles. A higher thermal conductivity of Ag2O nanoparticles accelerates the combustion and releases the maximum HRR.23,24,36 These results match with many studies21−25 that reported a similar HRR variation of the diesel engine fueled with the BD and nanoparticle mixture. 3.3. Brake Thermal Efficiency (BTE). BTE of POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm), and diesel is presented in Figure 4. The BTE for POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is lower than that for diesel at all engine loads. This is attributed to the lower viscosity and higher calorific value of diesel.21,25−27 BTE for POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is higher than that for POBD at all brake power (BP). Enhanced

Figure 5. Effect of Ag2O nanoparticles on BSFC with BP for tested fuels.

ppm), POBD + Ag2O (10 ppm), and diesel. BSFC of all tested fuels is reduced with an increase in BP. With the rise in BP, the quantity of fuel consumption increases but the BP increases more effectively, for which the BSFC decreases. The BSFC for POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is higher than that for diesel at all conditions. A lower calorific value of the biofuels increases the fuel consumption rate at all BP.26 Higher viscosity of biofuels [POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm)] reduces the air−fuel mixing rate and ends up with incomplete combustion, which results in a higher BSFC than diesel.21,25,26 BSFC for POBD + Ag2O (5 ppm) and POBD + Ag2O (10 ppm) is higher than that for POBD at all BP. Nanoparticles present in POBD enhance the oxidation reaction and lower BSFC.27,28 In addition, BSFC for POBD + Ag2O (10 ppm) is considerably C

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Energy & Fuels lower than that for POBD + Ag2O (5 ppm) at all conditions. Excess oxygen present in nanoparticles activates the combustion reaction and lowers BSFC. These results match with many studies27−29,36 that reported lower BSFC of the diesel engine fueled with the BD and nanoparticle mixture. BSFC at peak conditions for diesel, POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is 8.2, 9.0, 8.3, and 8.1 g/ kWh, respectively. 3.5. Brake Specific Oxides of Nitrogen Emissions. Figure 6 shows the change in brake specific oxides of NOx

Figure 7. Effect of Ag2O nanoparticles on the HC emission with BP for tested fuels.

all conditions. A higher existence of nanoparticles (5−10 ppm) enhances the combustion by providing excess oxygen during combustion and reduces HC emission.34 These results match with many studies24−28,33 that reported a lower HC emission of the diesel engine fueled with the BD and nanoparticle mixture. The HC emission at peak conditions for diesel, POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is 0.42, 0.33, 0.25, and 0.23 g/kWh, respectively. 3.7. Smoke Opacity. Figure 8 shows the variation in smoke emission with BP for POBD, POBD + Ag2O (5 ppm),

Figure 6. Effect of Ag2O nanoparticles on the NOx emission with BP for tested fuels.

emission with BP for POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm). NOx emission increases with BP for all tested fuels because of the increasing gas temperature.21,29 Diesel fuel has shown a lower NOx emission compared to POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) because of the 10−15% enriched oxygen concentration.30 NOx emission for POBD + Ag2O (5 ppm) and POBD + Ag2O (10 ppm) is significantly lower than that for POBD at all conditions. The presence of the Ag2O nanoparticle improved the heat transfer rate and lowered NOx emission.31 In addition, NOx emission for POBD + Ag2O (10 ppm) is considerably lower than that for POBD + Ag2O (5 ppm) at all conditions; this could be due to the increase in the cetane number with an increase in the Ag2O concentration.32 These results match with many studies27−29,36 that reported a lower NOx emission of the diesel engine fueled with the BD and nanoparticle mixture. The NOx emission at peak conditions for diesel, POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is 10.9, 12.9, 11.7, and 11.3 g/kWh, respectively. 3.6. Brake Specific Unburned HC Emissions. Figure 7 shows the variation in brake specific HC emission with BP for POBD, POBD + Ag2O (5 ppm), POBD + Ag2O (10 ppm), and diesel. The HC emission increases with BP for all test fuels, owing to the increase in the magnitude of the fuel, which results in a rich mixture, incomplete combustion, and a higher HC emission.21,26 The HC emission from diesel is higher than that from POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm). Natural oxygen in BD promotes the process of combustion and reduces HC emission. The HC emission for POBD + Ag2O (5 ppm) and POBD + Ag2O (10 ppm) is significantly lower than that for POBD at all conditions. The increase in thermal conductivity of nanoparticles enhances the combustion process and lowers the HC emission.33 Further, nanoparticles provide extra oxygen for the oxidation reaction of HC emission. The HC emission for POBD + Ag2O (10 ppm) is considerably lower than that for POBD + Ag2O (5 ppm) at

Figure 8. Effect of Ag2O nanoparticles on smoke opacity with BP for tested fuels.

POBD + Ag2O (10 ppm), and diesel. Smoke emission also increases with BP for all test fuels, owing to the increase in the magnitude of the fuel, which results in a rich mixture, incomplete combustion, and a higher smoke emission, as stated in the HC emission.21,26 Generally, the fuel with a higher HC emission exhibits a higher smoke emission. The smoke emission from POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is lower than that from diesel at BP. The inherent oxygen content of BD promotes the combustion process and reduces smoke emission.21,29,30 The smoke emission for POBD + Ag2O (5 ppm) and POBD + Ag2O (10 ppm) is significantly lower than that for diesel at all conditions. Nanoparticles improve the evaporation rate of POBD because of its natural oxygen.35 The smoke emission of POBD is further reduced by increasing Ag2O nanoparticles from 5 to 10 ppm. A higher content of Ag2O nanoparticles provides overindulgence of oxygen, boosts the combustion, and reduces smoke emission.36 These results match with many studies33−36 that reported a lower smoke emission of the diesel engine fueled with the BD and nanoparticle mixture. The smoke emission at peak conditions for diesel, POBD, POBD + D

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inclusion with POBD further reduces the HC, smoke, and CO emissions of the POBD-fueled diesel engine.

Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is 1.3, 1.2, 1.1, and 0.9%, respectively. 3.8. Brake Specific CO Emission. Figure 9 shows the variation in brake specific CO emission with BP for POBD,



AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] ORCID

Yuvarajan Devarajan: 0000-0002-6227-8935 Notes

The authors declare no competing financial interest.



REFERENCES

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Figure 9. Effect of Ag2O nanoparticles on CO emission with BP for tested fuels.

POBD + Ag2O (5 ppm), POBD + Ag2O (10 ppm), and diesel. CO emission increases with BP, owing to the increase in the fuel supplied with the same quantity of air in the cylinder, causing a rich mixture and a higher CO emission.21,37 CO emission from BD [POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm)] is lower than that from diesel at all BP. CO emission from diesel fuel is higher than that from POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) at all BP. This is owing to lesser availability of oxygen in diesel for possible conversion of CO to CO2.21,37 CO emission from POBD is higher than that from POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) at BP. Nanoparticles provide excess oxygen during the combustion process and reduce CO emissions.37 The CO emission of POBD + Ag2O (10 ppm) is significantly lower than that of POBD + Ag2O (5 ppm). A higher content of Ag2O nanoparticles provides overindulgence of oxygen, boosts the combustion, and reduces CO emission.38 These results match with many studies34−38 that reported a lower CO emission of the diesel engine fueled with the BD and nanoparticle mixture. The CO emission at peak conditions for diesel, POBD, POBD + Ag2O (5 ppm), and POBD + Ag2O (10 ppm) is 3.7, 3.6, 2.7, and 2.5 g/kWh, respectively.

4. CONCLUSION The ignition characteristics of POBD and various concentrations of Ag2O nanoparticles (5 and 10 ppm) added in neat POBD are detailed in the present study, and the results are compared to diesel. The study conclusions are as follows: (1) The dosage of 5 and 10 ppm of Ag2O nanoparticles improves the combustion attributes, such as HRR and cylinder pressure, owing to the improved thermal conductivity of POBD. (2) BTE for POBD is lesser than that for diesel at all conditions. However, the nanoparticle inclusion with POBD effectively enhanced the efficiency of POBD. In addition, the BSFC values of POBD reduced with inclusion of Ag2O nanoparticles across the entire engine operating conditions. (3) POBD releases more amount of NOx emission compared to diesel. However, the nanoparticle inclusion with POBD significantly reduces the NOx emission of the POBD-fueled diesel engine. (4) POBD releases considerably less amount of HC, smoke, and CO emissions than diesel. Additionally, the nanoparticle E

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DOI: 10.1021/acs.energyfuels.8b01125 Energy Fuels XXXX, XXX, XXX−XXX