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Pine oil-soapnut oil methyl ester blends: A hybrid biofuel approach to completely eliminate the use of diesel in a twin cylinder off-road tractor diesel engine
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Full Length Article
Pine oil-soapnut oil methyl ester blends: A hybrid biofuel approach to completely eliminate the use of diesel in a twin cylinder off-road tractor diesel engine ⁎
V. Venkatesana, , N. Nallusamyb a b
GKM College of Engineering and Technology, New Perungalathur, Chennai, India SSN College of Engineering, Kalavakkam, Kanchipuram, India
G R A P H I C A L A B S T R A C T
Tractor engine performance using hybrid biofuel (Soapnut oil methyl ester and pine oil blends)
A R T I C LE I N FO
A B S T R A C T
Keywords: Hybrid biofuel Pine oil Soapnut oil methyl esters Off-road vehicles Agricultural tractor engine Combustion
Off-road vehicles used for construction and agricultural activities are one among the major source of exhaust emission. In order to reduce the environmental impact caused by these vehicles, it is encouraged to use biofuels which are renewable and locally available throughout the year. In the present work, a light biofuel- pine oil was introduced to blend with a methyl ester derived from soapnut oil. This paper details the experimental investigations of the performance, combustion and emission characteristics of an agricultural tractor engine using the combination of biofuels as a complete replacement of conventional diesel fuel. The methyl esters of soapnut oil was blended with pine oil at different proportions. The blends P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100 were prepared on volume basis and complied with ASTM D-6751 specifications. The experiments were conducted in a Simpson S217, Twin cylinder tractor diesel engine to study the performance, combustion and emission characteristics of the prepared biofuel. The results showed that the specific fuel consumption of P100SNB0 and biofuel blends decreases up to 4% with the increased engine load. The brake thermal efficiency of the blend P50SNB50 and P75SNB25 were increased by 8% and 10% respectively at full load condition compared with diesel. The biofuel blends outperformed conventional Petro-diesel in terms of smoke, unburnt hydrocarbon (HC) and carbon monoxide (CO) with a slight penalty on NOx emissions. Up to 50% pine oil blended biodiesel (P75SNB25, P50SNB50) fuel can be used in diesel engines without affecting its performance, emission and combustion characteristics.
⁎
Corresponding author. E-mail address: [email protected] (V. Venkatesan).
https://doi.org/10.1016/j.fuel.2019.116500 Received 21 August 2019; Received in revised form 12 October 2019; Accepted 23 October 2019 0016-2361/ © 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: V. Venkatesan and N. Nallusamy, Fuel, https://doi.org/10.1016/j.fuel.2019.116500
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1. Introduction
viscous non-edible oil.
In the future, our traditional hydrocarbon fuels which are typically non-renewable would be depleted. Also, the amount of CO2 released by burning petroleum diesel is trapped in the earth, increasing the temperature of earth’s atmosphere resulting in global warming, whereas the CO2 released by biodiesel mostly consumed by plants for its growth. One way to reduce the amount of CO2 produced from internal combustion (IC) engines is to increase the use of renewable biofuels. It is the time to explore alternative and renewable sources of fuel for the future. The alternative fuel must be technically feasible, economically competitive and easily available. In this regard, biodiesel is considered as the only alternative for the diesel engines that can be used directly without any modifications. The low emission level of biodiesel make it an ideal fuel for use in automotive engines, stationary engines, generator engines and off road vehicle engines. Biodiesel are generally prepared from vegetable oil seeds, plants, animal fat and used cooking oil etc., Among these, biodiesel prepared from oilseeds has gained considerable importance, which in turn reduces the dependence on crude oil and petroleum import. Ultimately, this can generates agricultural revenue and creates rural jobs. It is found that the commonly used oilseeds for the biofuel productions are soya bean, rape seed, sunflower seed, palm seeds etc., Fuel prepared from the above edible oil seeds are called as first generation biofuels [1]. Though these fuels alternate the petroleum based fuels effectively, there are some downsides in the usage of these edible oil feedstock. Biodiesel production using these edible oil leads to the increase in price of cooking oil, which in turn increases the cost of the biodiesel. Moreover, for plantation it requires massive land, ultimately affects our agriculture and also food production [2]. The second generation biofuels are usually derived from the non-edible seed crops like jatropha, karanja, waste cooking oil and animal fats, etc., Even though these kind of plants do not compete with food production, only few oil producing crops are economical on a large scale. Biofuel has certain disadvantages like high viscosity, clogging of injector nozzles, carbon deposition on cylinder walls, gum formation in the presence of oxygen and thickening of lubricating oil. Over the decades, researchers have made rigorous efforts to resolve the major issues associated with biofuels. The problem of gum formation and clogging of nozzle can be alleviated by trans esterification of biofuel [3]. The high viscosity of the biofuels causes poor atomization leading to incomplete combustion. Viscosity of biofuel can be reduced effectively by blending it with some proportion of diesel by volume. Another approach is to combine the low viscosity fuels such as alcohols, plant based biofuels like eucalyptus oil and turpentine with standard diesel or highly viscous biodiesel like Jatropha, Karanja, Soapnut, Waste cooking oil, Cashew Nut Shell oil etc., to attain viscosity closer to diesel [4]. Recent researches on advanced cultivation methods, extraction and processing techniques have made it possible to produce biodiesel at economical costs and quantities from plant based oil. The blends of biodiesel with fossil diesel has many benefits like reduction in emissions, higher cetane rating, lower engine wear and reduction in oil consumption etc. Some biofuels offer better engine performance and emission characteristics compared with diesel and conventional biodiesel [5]. The utilization of these plant based biofuels will have a great impact on Indian economy. The on road vehicles like cars, buses and trucks are recognized as important source of air pollution, less attention has been paid in controlling emissions from off road engines. The exhaust gas emission especially NOx and particulate matter of agricultural engines are very high compared to on road vehicle engines [6]. But the efforts taken to cut down emissions from these off road engines are still very less. One such effort is the hybrid biofuel approach which eliminates the use of diesel completely using the blends of a low viscous fuel with a high
1.1. Hybrid biofuel approach for diesel engines Past biofuel researches targeted the blending of biofuels with low viscous diesel up to a certain percentage. In recent years, studies have been carried out to explore the potential of hybrid biofuels which completely eliminates the usage of conventional diesel in compression ignition (CI) engines. Studies revealed that there is a considerable improvement in engine performance and reduced emission levels by using a less viscous fuel such as alcohol, eucalyptus oil and pine oil blended with high viscous biodiesel fuels. A study conducted using 100% pine oil in diesel engines reduced carbon monoxide (CO) emission by 65%, hydrocarbon (HC) emission by 30%, smoke emission by 70%, increased brake thermal efficiency and maximum heat release rate by 5% and 27% respectively at full load condition [7]. In a research using methyl ester derived from paradise oil and eucalyptus oil in 50: 50 ratio blend volume for the complete replacement of diesel fuel resulted in 49% reduction in smoke, 34.5% reduction in HC emissions and 37% reduction in CO emissions. Increase in brake thermal efficiency of 2.4% with 2.7% increase in NOx emission at full load is also reported [8]. For a B50 blend of paradise oil methyl ester and diesel, 33% reduction in smoke, 22% reduction in HC emission and 5% increase in NOx emission were noticed. The brake thermal efficiencies of all the blends are slightly lower than that of standard diesel [9]. The performance, combustion and emission characteristics of biofuels from ceiba pentandra methyl ester (CPME) – pine oil blends were studied and the results were compared with diesel. The high viscosity CPME is blended with low viscosity pine oil and directly used in a naturally aspirated compression ignition engine. The increase in the percentage of pine oil exhibited increase in brake thermal efficiency, increase in ignition delay due to the low cetane number and increase in cylinder pressure due to higher calorific value and low viscosity. The experimental fuels up to B50 (50:50% of pine oil and CPME) blends are known potential energy sources for the diesel engines [10]. The performance and emission characteristics of Pine oil blended with Kapok Methyl Ester in different proportions were tested in a single cylinder diesel engine to exclude the use of fossil diesel completely. In which, for the blend B25P75 the brake thermal efficiency of the engine was increased by 8% in comparison with diesel. The reduction in HC, CO and smoke emission is 14.9%, 43.2% and 33.4% respectively in comparison with the blend B50P50 where the values are 12.5%, 8.1% and 18.9% for similar studies. In dual biofuel strategy using low viscous oils, B50 could be regarded as the optimum blend ratio which is feasible for long term usage in diesel engines with some additives [11]. Experimental studies on combustion, performance and emission characteristics were carried out on a single cylinder, naturally aspirated and variable compression ratio diesel engine using conventional diesel fuel and different blends like B100T0, B90T10, B70T30 and B50T50 of Jatropha biodiesel and turpentine oil. The tested blends were found to be a greatest substitute to diesel fuel in all aspects such as emission and performance [12]. Further the blend B50T50 at a compression ratio of 20:1, results in 2.17% increase in brake thermal efficiency and 13.04%, 17.5%, 4.21% and 30.8% decrease in CO, HC, NOx and smoke opacity respectively while CO2 was observed to increase by 11.04%. The effect of Melaleuca Cajuputi Oil (MCO) and Refined Palm Oil (RPO) in a four stroke, single cylinder diesel engine was investigated and the regression analysis was carried out to identify the optimum blend ratio. For the optimum hybrid biofuel blend RPO32MCO68, incylinder peak pressure, NOx and the smoke opacity were dropped by 10.7%, 17.3% and 64.5% respectively at maximum engine speed [13]. Neat Rubber seed Oil (RSO) and Babassu Oil (BSO) blend was used to study the performance and emission characteristics of a twin cylinder, direct injection diesel engine. Rubber seed oil and babassu oil were blended in various proportions of 75:25, 50:50 and 25:75 and tested at a constant speed of 1200 rpm. With the optimum blend R50B50, 20% 2
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has lower viscosity, lower boiling point, lower cetane number, higher calorific value and high latent heat of vaporization than diesel. However, the higher self-ignition temperature of pine oil hampers its direct use in diesel engines. Hence it is decided to blend the pine oil with the methyl esters of soapnut oil at different proportions to balance most of the properties and to bring it closer to petro diesel. Recently, researchers turned their attention to use lower viscosity and lower cetane index fuels like eucalyptus oil, pine oil and camphor oil in Compression Ignition (CI) engines [17]. By using such fuels, the atomization, evaporation and air/fuel mixing process can be improved. Moreover, it creates sufficient delay time and the fuel to air equivalence ratio is reduced to decrease the soot emission without compromising. Experiments were conducted on CI engine using diesel, palm oil biodiesel blends with turpentine oil at 10, 20, 30 and 40 percentages by volume [18]. The fuel characterization study revealed that the low viscosity of turpentine oil makes combustion process of biodiesel easier with no unburned hydrocarbon and carbon monoxide emissions. Similarly low flash point makes fuel to catch fire rapidly with no ignition delay and the higher calorific value is useful in giving more power output. With this scope, this experimental work was carried out to blend the low viscosity, low cetane indexed pine oil with the high viscosity, high cetane indexed soapnut oil methyl ester. Addition of soapnut oil methyl ester with pine oil increases the flash point of pine oil blend. Hence it is safer to store the blends as compared to pine oil alone.
by volume of an oxygenated additive Diglyme (DGE), which has a higher cetane number and latent heat of vaporization was added [14]. The addition of 20% diglyme with R50B50 blend improved combustion and increased BTE by 6% at full load condition. The addition of diglyme also reduced harmful emissions like HC, CO and smoke opacity with a slight increase in NOx emission. Most of the research based on biodiesel has been conducted in laboratories using the heavy duty highway and stationary engines, but little attention was given to off-road engines. The idling speed of offroad engines are relatively low, only a small amount of fuel is supplied in order to maintain the engine crankshaft revolution and the combustion efficiency drops significantly which results in higher hydrocarbon emissions [15]. The literature survey reveals that the usage of dual biofuel (100% biofuel) in the automotive diesel engines is very limited. Detailed experimental studies are still needed to counter the short comings of increased NOx emission with the usage of biodiesel. This paper summarizes the performance, combustion and emission characteristics of soapnut oil methyl esters and its blends with pine oil (hybrid biofuels) in a tractor diesel engine (off-road vehicles). 2. Materials and methods 2.1. Fuel preparation Soap nuts are well-known worldwide in different names such as soapberry, washing nuts, soap nut shells, wash shells, Ritha, Chinese soapberry and many more. There are several varieties of soapnuts found in India, Indonesia, Pakistan, China, many parts of Europe, U.S and few countries in the eastern hemisphere. Sapindus Mukorossi and Sapindus Trifoliatus are the two major species found in southern India. The soapnut is considered as the third most productive vegetable oil producing crop in the world, after algae and oil palm, having significant potential for biodiesel production [16]. The soapnuts for this research were purchased in open markets in their dried form and de-shelled to obtain the oil containing seed. The seeds were de-hulled to clean and separate the oil containing kernels. A cold pressed oil expeller was used to crush the kernels and squeeze the oil using friction and continuous pressure. The extracted oil was cleaned and processed to remove impurities such as dirt and plant matters. Soap nut oil biodiesel was produced by base catalyzed trans esterification reaction as it is the most economical process, requiring only low temperatures and producing 98% conversion yield. Esterification was carried out using 0.50% KOH w/w of oil, 6:1 M ratio of methanol to oil at a reaction temperature of 60 °C for a duration of 1 h. Pine oil is an odorous, colorless, flammable biofuel obtained from the pine needles by steam distillation process. The viscosity, boiling point and flash point of the pine oil are lower, when compared to that of diesel and the calorific value is comparable to diesel. Hence it can be directly used in diesel engines without transesterification. In the present work, the readily available pine oil was purchased from chemical dealers, the fatty acid composition of the neat pine oil was examined by using GC–MS at Sophisticated Analytical Instruments Facility, IITM, Chennai, India. The results revealed that the major component present in the pine oil is α-terpineol (C10H18O) and α-pinene (C10H16) with simple molecular structure and lower molecular weight than diesel. The hybrid biofuel blends with different combination of pine oil and soapnut biodiesel namely P100SNB0 (100:0%), P75SNB25 (75%:25%), P50SNB50 (50%:50%), P25SNB75 (25%:75%) and P0SNB100 (0:100%) were prepared on volume basis.
2.3. Experimental setup The engine used for this experimental work is Simpson’s S217 twincylinder CI engine used in agricultural tractors. The engine develops a maximum power of 15 kW at 1500 rpm. The engine is coupled with an eddy current dynamometer of Accurate make for loading. The compression ratio of the engine is 18.5:1 and a hemispherical-type combustion chamber is used to create the necessary swirl. The detailed specifications of the engine are listed in Table 2. A mechanical-type fuel injection system with a multi hole nozzle injector is used. The fuel injection timing is fixed at 23°bTDC and the constant injection pressure is maintained at 200 bar throughout the test. The time taken for 20 cc of fuel consumption was noted manually using a burette and stopwatch for calculating total fuel consumption. The air flow rate was measured using an orifice meter fitted with a U-tube manometer in the intake air supply system. Fig. 1 shows the schematic diagram of the experimental setup. In-cylinder combustion pressure and its cyclic variations were obtained using Kistler 701A pressure transducer mounted over the cylinder head and the corresponding crank angle was measured through crank angle encoder placed in the crankshaft. The combustion parameters such as heat release rate and ignition delay were measured using the software Engine Performance Analyzer EPA 1.0.1. In the present study, exhaust emissions such as CO (Carbon monoxide), CO2 (Carbon dioxide), and O2 (Exhaust oxygen) are measured in terms of percentage volume. The HC (Unburnt hydrocarbon) and NO (Oxides of nitrogen) are measured in terms of parts per million (ppm) using AVL 444 di gas analyzer based on Non Dispersive Infra-Red (NDIR) principle. The smoke opacity was measured using AVL 432C smoke meter. 2.4. Experimental procedure and uncertainty analysis Before starting the experiment, the engine was allowed to run at 1400 rpm without load for 30 min so as to attain the steady state conditions. At the steady state conditions, the base test was carried out using diesel as fuel at different loads. The engine was loaded at 0%, 25%, 50%, 75% and 100% progressively in steps by controlling the current applied to the eddy current dynamometer. When changing engine load, the rack position of fuel pump is adjusted to regulate the fuel supply so that a constant speed of 1400 rpm is maintained.
2.2. Fuel properties The physical and chemical properties of the biofuel blends were determined as per ASTM standard and tabulated in Table 1. The pine oil 3
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Table 1 Properties of pine oil and soapnut biodiesel blends compared with diesel. Parameter 3
Density at 15 °C (kg/m ) Viscosity at 50 °C (mm2/s) Flash point (°C) Lower calorific value (kJ/kg) Cetane No.
Diesel
P100
SNB100
SNB25P75
SNB50P50
SNB75P25
Test method
832 3.42 52 40,290 53
847 1.2 36 41,848 22
868 3.6 158 37,723 56
851 1.8 67 40,816 30
857 2.4 97 39,785 39
862 3.0 127 38,754 47
ASTM ASTM ASTM ASTM ASTM
D1298 D445 D93 D240 D613
uncertainty of the various equipments used for this experimental study as shown in Table 3.
Table 2 Test engine specifications. Model
Simpsons S217 tractor engine
Type Cooling system No of cylinders Bore X stroke Compression ratio Cubic capacity Rated power Fuel pump Dynamometer Pressure pick up
Inline direct injection diesel engine, naturally aspirated Water cooling 2 91.44 X 127 mm 18.5:1 1670 C.C 15 kW at 1500 rpm Mico-Bosch Inline pump Eddy current Kistler 701A
3. Results and discussion 3.1. Brake specific fuel consumption The brake specific fuel consumption (BSFC or SFC) of the engine is influenced by the properties of fuel, engine design and operating conditions. The Fig. 2 shows the variation of BSFC with respect to load for diesel, pine oil and pine oil-soapnut methyl ester blends. There is a significant reduction in BSFC of pine oil than diesel beyond 50% load. This is due to its higher calorific value and lower viscosity of pine oil than diesel fuel and other biofuel blends. Based on the volume of soapnut biodiesel in the blend, the calorific value decreases considerably and thereby increasing the brake specific fuel consumption. From the experimental results, it was inferred that all the biofuel blends (P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100) produce optimum results at full loads. A reduction of 18% of BSFC was observed in the blend P75SNB25 and P50SNB50 at full load condition than diesel.
Whenever, the fuel is changed the engine was allowed to run for about 15 min to attain steady state condition with the new fuel before measurements were taken. The experiments were repeated for all the test fuels, three trials were conducted for each loading and finally the average values were taken for calculations. Calculations were made to find out the Specific fuel consumption, Brake power, and Brake thermal efficiency for all the fuel samples (Diesel, P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100) and the engine emissions were also noted. To ensure the legitimacy of the measured values, uncertainty analysis [19] was carried out based on the percentage
Fig. 1. Schematic of experimental setup. 4
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Table 3 Uncertainty of the measuring instruments/equipments. Sl. No.
Instrument
Make
Type
Accuracy
% Uncertainty
1 2 3 4 5 6 7 8 9 10
Pressure sensor Crank angle encoder Load indicator CO HC CO2 NOx Smoke meter Burette Orifice meter
Kistler
Piezo electric sensor Magnetic pickup type Strain gauge type load cell NDIR principle NDIR principle NDIR principle NDIR principle Hatridge smoke meter Volumetric measurement of fuel U tube manometer
± 0.5 bar ± 1o ± 0.1 kg ± 0.02% ± 20 ppm ± 0.03% ± 10 ppm ± 1% ± 0.1 cm3 ± 1 mm
±1 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.15 ±1 ±1 ±1 ±1
AVL AVL AVL AVL AVL
444 444 444 444
digas digas digas digas
thermal efficiency. For the blends P50SNB50, P75SNB25 and P100SNB0, the brake thermal efficiency was increased by 8%, 10% and 13% respectively at full load condition compared with diesel. 3.3. Cylinder pressure and heat release rate Variation of cylinder pressure with respect to crank angle for the different biofuel blends and diesel at full load is presented in Fig. 4. No significant differences in peak cylinder pressure were noted within biodiesel blends. The exhaust gas temperature and heat release rate of all the fuel blends were higher than diesel due to the better combustion of fuel. The cylinder peak pressure for diesel, P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100 were recorded as 88.57 bar, 91.22 bar, 87.54 bar, 85.38 bar, 85.09 bar and 84.62 bar respectively. The cylinder peak pressure of P100SNB0 was 4–8% higher than the biodiesel blends and 3% higher than diesel. This could be due to the lower viscosity of pine oil that is a favorable property as a fuel for combustion through better vaporization and atomization. The increase in the soapnut biodiesel blend ratio decreases the peak pressure as compared to diesel and pine oil. This is due to the higher viscosity of the blends and lower heating value. Fig. 5, shows the heat release rate of methyl esters of soapnut oil and its blends of pine oil. The P100SNB0 shows higher heat release than diesel and other blends due to its higher calorific value.
Fig. 2. The variation of specific fuel consumption with load.
3.2. Brake thermal efficiency The brake thermal efficiency (BTE) of the engine is inversely proportional to the brake specific fuel consumption and depends upon the properties of fuel and combustion parameters. Due to high volatility and low viscosity of pine oil, atomization and vaporization are improved. Fig. 3 shows the variation of brake thermal efficiency with respect to engine load for diesel, pure pine oil and pine oil-soapnut biodiesel blends at different loads. From the Fig. 3, it is inferred that the increase in the percentage of pine oil in the blends, increases the brake
3.4. Exhaust gas temperature Diesel engine operates at higher compression ratio than the gasoline engines, which increases the temperature in the combustion chamber that results in higher exhaust gas temperature. The formation of NOx
Fig. 3. The variation of brake thermal efficiency with load.
Fig. 4. The variation of cylinder pressure with crank angle. 5
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Fig. 5. The variation of engine heat release rate with crank angle. Fig. 7. The variation of smoke emission with load.
3.6. Unburnt hydrocarbon emission Incomplete combustion of fuel leads to unburnt hydrocarbon (HC) emissions resulting from lean combustion and improper mixing of air and fuel inside the combustion chamber. The viscosity of fuel, ignition quality, spray characteristics and engine operating conditions play a vital role in the formation of HC emission. The variation of HC emission for the tested fuel at different engine loads are presented in the Fig. 8. HC emissions of Soapnut biodiesel blends are lower than that of pure pine oil owing to post flame oxidation. Due to the excess oxygen present in the plant based oils and higher the cetane number, the complete combustion is ensured. From the experimental results, it was observed that the reduction of 40%–60% of Unburnt hydrocarbon emission at full load for the blends P75SNB25 and P50SNB50 than diesel.
3.7. Carbon monoxide emission Fig. 6. The variation of exhaust gas temperature with load.
The carbon monoxide (CO) emission is generally formed when there is insufficient oxygen for the combustion of fuel. Some other factors affecting the CO emission are Cetane number, carbon-to- hydrogen ratio of the fuel used [20]. Diesel engines working with excess air normally emits lower CO. The carbon monoxide emission of all the test fuel increases as the load increases and is shown in Fig. 9. The diesel
emission depends mainly on the temperature of the combustion. At higher cylinder temperatures, the emissions of NOx is higher because more energy promotes the chemical reaction. Lower the temperatures, lower the NOx. The exhaust gas temperature rises as the load on the engine increases. The variation of exhaust gas temperature with respect to engine load is presented in Fig. 6. The diesel has the least exhaust gas temperature than all other biofuel blends at full load operation. The exhaust gas temperature of P100SNB0 is slightly lower than diesel at higher loads. Increasing biodiesel percentage in the blends increases the exhaust gas temperature by 5%–20% due to excess oxygen present in the soapnut biodiesel.
3.5. Smoke density Smoke emission increases with the increase in engine load due to overall richer fuel-air ratios. Hence, engine power is normally specified based on the maximum tolerable smoke density to curtail the black smoke emissions from engine. The smoke opacity indicates the soot content on exhaust gas, it is also a component of particulate matter. The variation of smoke emission with respect to engine load is presented in Fig. 7. The smoke opacity of all the tested fuels are lower than that of diesel at all the load. Hence it can be concluded that the blends P75SNB25 and P50SNB50 would be better blend from the view point of smoke level.
Fig. 8. The variation of hydrocarbon emission with load. 6
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4. Conclusions The current work focusses on the salient features in the usage of hybrid biofuel pine oil-soapnut oil methyl ester blends in a tractor diesel engines thereby swapping the use of conventional diesel fuel completely. The fuel properties of pine oil is unique and superior to conventional diesel whereas for soapnut biodiesel, it is similar to other edible and non-edible biodiesel fuels. The blends also have similar physical and chemical properties as per the ASTM biofuel standard and favorable for diesel engine operation. The concept of blending low viscous neat pine oil with the high viscous soapnut oil methyl ester reduces the cost of fuel substantially. The lower cetane value of pure pine oil could be balanced by higher cetane value of soapnut oil methyl ester so as to achieve better combustion. The following conclusions were made with respect to engine performance, combustion and emission characteristics.
• For the blends P100SNB0, P75SNB25 and P50SNB50, the increase in Fig. 9. The variation of carbon monoxide emission with load.
• • • • •
brake thermal efficiency of about 13%, 10% and 8% respectively was observed at full load condition compared with diesel. All the biofuel blends (P100SNB0, P75SNB25, P50SNB50 and P25SNB75) offers enhanced fuel economy beyond 50% load. A reduction of 18% in BSFC was observed for the blend P50SNB50 at full load condition than diesel. The cylinder peak pressure for P50SNB50 was recorded as 85.38 bar which is slightly lesser than diesel. The exhaust gas temperature for the blends P75SNB25 and P50SNB50 is similar to that of diesel at higher loads. There is a reduction of 40% in unburnt Hydrocarbon emission with the blends P75SNB25 and P50SNB50 as compared to diesel at full load. The Carbon monoxide emission for the blend P75SNB25 is lower by 6% than all the test fuels at full load condition. The increase in NOx emission of about 3%–5% was found for the blend P75SNB25 at low loads compared with diesel. It is observed that the blends P100SNB0, P75SNB25, P50SNB50 and P25SNB75 have smoke emission less than diesel up to 75% load and almost same as that of diesel at full load.
The experimental results proved that the hybrid biofuel blend P75SNB25 can be considered as a potentially good substitute for the tractor diesel engine. Overall, the performance, combustion and emission characteristics of the tested fuels showed better results than conventional biodiesel fuels and its blends with diesel. The homogeneous composition of two or more biofuels facilitate their use in advanced engine concepts such as HCCI, Lean burn engines and LHR engines. The hybrid biofuel approach is highly compatible with the long term strive towards advanced and more efficient engines.
Fig. 10. The variation of NOx emission with load.
and P75SNB25 has almost same value of CO emission up to 50% load and beyond that the CO emission is very lower than diesel, P100SNB0 and other higher blends. From the experimental results, it can be concluded that P75SNB25 gives better result in terms of CO reduction at higher loads. The obtained CO emission results are similar to the results achieved in a F1145 John Deere Front Mower off-road engine using waste cooking oil biodiesel blends with diesel at idling condition [21].
Declaration of Competing Interest 3.8. Oxides of nitrogen emission
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Oxides of Nitrogen (NOx) emission depends upon the time needed for the reaction to take place and the in-cylinder temperature. The variation of NOx emission with respect to engine load for different fuels are presented in Fig. 10. The NOx emission of P75SNB25 has shown very slight increase than diesel and low values than other soapnut biodiesel blends as well as pine oil. Increase in the pine oil content in the blend in turn increases the ignition delay due to the lower cetane number which leads to higher heat release rate. The better combustion of these blends increases the cylinder temperature and thereby increasing the NOx emission at all the loads. From the results, it can be concluded that the blend P75SNB25 has little increase in NOx emission of about 3%–5% in part load conditions.
References [1] Knothe G. Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Tech 2005;86:1059–70. [2] Giuliano Dragone, Bruno Fernandes, Antonio A. Vicente, Jose A. Teixeira, Third generation biofuels from microalgae. Current Research, Technology and Education Topics in Applied Microbiology and Microbial Biotechnology 2010; 1355-1366. [3] Agarwal Avinash Kumar. Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energy Combust Sci 2007;33:233–71. [4] Dubey P, Gupta R. Effects of dual bio-fuel (Jatropha biodiesel and turpentine oil) on a single cylinder naturally aspirated diesel engine without EGR. Appl Therm Eng 2017;115:1137–47. [5] Anand BP, Saravanan C, Srinivasan CA. Performance and exhaust emission of
7
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[6] [7]
[8]
[9] [10]
[11]
[12]
[13]
2018;11(3146):1–20. [14] Edwin Geo Varuvel, Thiyagarajan Subramanian & Prakhar Khatri, Effect of diglyme addition on performance and emission characteristics of hybrid minor vegetable oil blends (rubber seed and babassu oil) in a tractor engine – an experimental study, Biofuels, DOI: 10.1080/17597269.2017.1418568. [15] Pekula N, Kuritz B, Hearne J, Marchese AJ, Hesketh RP. The effect of ambient temperature, humidity, and engine speed on idling emissions from heavy-duty diesel trucks. SAE Paper 2003;01:01–0290. [16] Karmakar A, Karmakar S, Mukherjee S. Biodiesel production from neem towards feedstock diversification: Indian Perspective. Renewable Sustainable Energy Rev 2012;16:1050–60. [17] Kasiraman G, Nagalingam B, Balakrishnan M. Performance, emission and combustion improvements in a direct injection diesel engine using cashew nut shell oil as fuel with camphor oil blending. Energy 2012;47:116–24. [18] Venkateswara Rao P, Prabhakara Chary D. Diesel engine performance analysis with blend fuel of biodiesel and Turpentine oil as biofuel additive. Int J Eng, Sci Math 2018;7:176–82. [19] Holman JP. Experimental Methods for Engineers. McGraw-hill Publishers; 2012. ISBN 978-0-07-352930-1. [20] Gang Wu, Jiang Guohe, Yang Zhiyuan, Huang Zhijian. Emission characteristics for waste cooking oil biodiesel blend in a marine diesel propulsion engine. Polish J Environ Stud 2019;28:2911–21. [21] Guo Jing, Peltier Edward, Stagg-Williams Susan M, Carter Ray E, Krejci Alex J, Depcik Christopher. Waste cooking oil biodiesel use in two off-road diesel engines. ISRN Renewable Energy 2012;130782:1–10.
turpentine oil powered direct injection diesel engine. Renew Energy 2010;35:1179–84. Kean Andrew J, Sawyer Robert F, Harley Robert A. A fuel-based assessment of offroad diesel engine emissions. J Air Waste Manage 2011;50:1929–39. Vallinayagam R, Vedharaj S, Yang WM, Lee PS, Chua KJE, Chou SK. Combustion performance and emission characteristics study of pine oil in a diesel engine. Energy 2013;57:344–51. Devan PK, Mahalakshmi NV. A study of the performance, emission and combustion characteristics of a compression ignition engine using methyl ester of paradise oileucalyptus oil blends. Appl Energy 2009;86:675–80. Devan PK, Mahalakshmi NV. Utilization of unattended methyl ester of paradise oil as fuel in diesel engine. Fuel 2009;88:1828–33. Panneerselvam N, Ramesh M, Murugesan A, Vijayakumar C, Subramaniam D. Effect on direct injection naturally aspirated diesel engine characteristics fuelled by pine oil, ceiba pentandra methyl ester compared with diesel. Transp Res Part D 2016;48:225–34. Vallinayagam R, Vedharaj S, Yang WM, Lee PS, Chua KJE, Chou SK. Pine oil-biodiesel blends: a double biofuel strategy to completely eliminate the use of diesel in a diesel engine. Appl Energy 2014;130:466–73. Dubey P, Gupta R. Influences of dual bio-fuel (Jatropha biodiesel and turpentine oil) on single cylinder variable compression ratio diesel engine. Renewable Energy 2018;115:1294–302. Mat Sharzali Che, Idroas Mohamad Yusof, Teoh Yew Heng, Hamid Mohd Fadzli. Physicochemical, performance, combustion and emission characteristics of melaleuca cajuputi oil-refined palm oil hybrid biofuel blend. Energies
8
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Full Length Article
Pine oil-soapnut oil methyl ester blends: A hybrid biofuel approach to completely eliminate the use of diesel in a twin cylinder off-road tractor diesel engine ⁎
V. Venkatesana, , N. Nallusamyb a b
GKM College of Engineering and Technology, New Perungalathur, Chennai, India SSN College of Engineering, Kalavakkam, Kanchipuram, India
G R A P H I C A L A B S T R A C T
Tractor engine performance using hybrid biofuel (Soapnut oil methyl ester and pine oil blends)
A R T I C LE I N FO
A B S T R A C T
Keywords: Hybrid biofuel Pine oil Soapnut oil methyl esters Off-road vehicles Agricultural tractor engine Combustion
Off-road vehicles used for construction and agricultural activities are one among the major source of exhaust emission. In order to reduce the environmental impact caused by these vehicles, it is encouraged to use biofuels which are renewable and locally available throughout the year. In the present work, a light biofuel- pine oil was introduced to blend with a methyl ester derived from soapnut oil. This paper details the experimental investigations of the performance, combustion and emission characteristics of an agricultural tractor engine using the combination of biofuels as a complete replacement of conventional diesel fuel. The methyl esters of soapnut oil was blended with pine oil at different proportions. The blends P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100 were prepared on volume basis and complied with ASTM D-6751 specifications. The experiments were conducted in a Simpson S217, Twin cylinder tractor diesel engine to study the performance, combustion and emission characteristics of the prepared biofuel. The results showed that the specific fuel consumption of P100SNB0 and biofuel blends decreases up to 4% with the increased engine load. The brake thermal efficiency of the blend P50SNB50 and P75SNB25 were increased by 8% and 10% respectively at full load condition compared with diesel. The biofuel blends outperformed conventional Petro-diesel in terms of smoke, unburnt hydrocarbon (HC) and carbon monoxide (CO) with a slight penalty on NOx emissions. Up to 50% pine oil blended biodiesel (P75SNB25, P50SNB50) fuel can be used in diesel engines without affecting its performance, emission and combustion characteristics.
⁎
Corresponding author. E-mail address: [email protected] (V. Venkatesan).
https://doi.org/10.1016/j.fuel.2019.116500 Received 21 August 2019; Received in revised form 12 October 2019; Accepted 23 October 2019 0016-2361/ © 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: V. Venkatesan and N. Nallusamy, Fuel, https://doi.org/10.1016/j.fuel.2019.116500
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1. Introduction
viscous non-edible oil.
In the future, our traditional hydrocarbon fuels which are typically non-renewable would be depleted. Also, the amount of CO2 released by burning petroleum diesel is trapped in the earth, increasing the temperature of earth’s atmosphere resulting in global warming, whereas the CO2 released by biodiesel mostly consumed by plants for its growth. One way to reduce the amount of CO2 produced from internal combustion (IC) engines is to increase the use of renewable biofuels. It is the time to explore alternative and renewable sources of fuel for the future. The alternative fuel must be technically feasible, economically competitive and easily available. In this regard, biodiesel is considered as the only alternative for the diesel engines that can be used directly without any modifications. The low emission level of biodiesel make it an ideal fuel for use in automotive engines, stationary engines, generator engines and off road vehicle engines. Biodiesel are generally prepared from vegetable oil seeds, plants, animal fat and used cooking oil etc., Among these, biodiesel prepared from oilseeds has gained considerable importance, which in turn reduces the dependence on crude oil and petroleum import. Ultimately, this can generates agricultural revenue and creates rural jobs. It is found that the commonly used oilseeds for the biofuel productions are soya bean, rape seed, sunflower seed, palm seeds etc., Fuel prepared from the above edible oil seeds are called as first generation biofuels [1]. Though these fuels alternate the petroleum based fuels effectively, there are some downsides in the usage of these edible oil feedstock. Biodiesel production using these edible oil leads to the increase in price of cooking oil, which in turn increases the cost of the biodiesel. Moreover, for plantation it requires massive land, ultimately affects our agriculture and also food production [2]. The second generation biofuels are usually derived from the non-edible seed crops like jatropha, karanja, waste cooking oil and animal fats, etc., Even though these kind of plants do not compete with food production, only few oil producing crops are economical on a large scale. Biofuel has certain disadvantages like high viscosity, clogging of injector nozzles, carbon deposition on cylinder walls, gum formation in the presence of oxygen and thickening of lubricating oil. Over the decades, researchers have made rigorous efforts to resolve the major issues associated with biofuels. The problem of gum formation and clogging of nozzle can be alleviated by trans esterification of biofuel [3]. The high viscosity of the biofuels causes poor atomization leading to incomplete combustion. Viscosity of biofuel can be reduced effectively by blending it with some proportion of diesel by volume. Another approach is to combine the low viscosity fuels such as alcohols, plant based biofuels like eucalyptus oil and turpentine with standard diesel or highly viscous biodiesel like Jatropha, Karanja, Soapnut, Waste cooking oil, Cashew Nut Shell oil etc., to attain viscosity closer to diesel [4]. Recent researches on advanced cultivation methods, extraction and processing techniques have made it possible to produce biodiesel at economical costs and quantities from plant based oil. The blends of biodiesel with fossil diesel has many benefits like reduction in emissions, higher cetane rating, lower engine wear and reduction in oil consumption etc. Some biofuels offer better engine performance and emission characteristics compared with diesel and conventional biodiesel [5]. The utilization of these plant based biofuels will have a great impact on Indian economy. The on road vehicles like cars, buses and trucks are recognized as important source of air pollution, less attention has been paid in controlling emissions from off road engines. The exhaust gas emission especially NOx and particulate matter of agricultural engines are very high compared to on road vehicle engines [6]. But the efforts taken to cut down emissions from these off road engines are still very less. One such effort is the hybrid biofuel approach which eliminates the use of diesel completely using the blends of a low viscous fuel with a high
1.1. Hybrid biofuel approach for diesel engines Past biofuel researches targeted the blending of biofuels with low viscous diesel up to a certain percentage. In recent years, studies have been carried out to explore the potential of hybrid biofuels which completely eliminates the usage of conventional diesel in compression ignition (CI) engines. Studies revealed that there is a considerable improvement in engine performance and reduced emission levels by using a less viscous fuel such as alcohol, eucalyptus oil and pine oil blended with high viscous biodiesel fuels. A study conducted using 100% pine oil in diesel engines reduced carbon monoxide (CO) emission by 65%, hydrocarbon (HC) emission by 30%, smoke emission by 70%, increased brake thermal efficiency and maximum heat release rate by 5% and 27% respectively at full load condition [7]. In a research using methyl ester derived from paradise oil and eucalyptus oil in 50: 50 ratio blend volume for the complete replacement of diesel fuel resulted in 49% reduction in smoke, 34.5% reduction in HC emissions and 37% reduction in CO emissions. Increase in brake thermal efficiency of 2.4% with 2.7% increase in NOx emission at full load is also reported [8]. For a B50 blend of paradise oil methyl ester and diesel, 33% reduction in smoke, 22% reduction in HC emission and 5% increase in NOx emission were noticed. The brake thermal efficiencies of all the blends are slightly lower than that of standard diesel [9]. The performance, combustion and emission characteristics of biofuels from ceiba pentandra methyl ester (CPME) – pine oil blends were studied and the results were compared with diesel. The high viscosity CPME is blended with low viscosity pine oil and directly used in a naturally aspirated compression ignition engine. The increase in the percentage of pine oil exhibited increase in brake thermal efficiency, increase in ignition delay due to the low cetane number and increase in cylinder pressure due to higher calorific value and low viscosity. The experimental fuels up to B50 (50:50% of pine oil and CPME) blends are known potential energy sources for the diesel engines [10]. The performance and emission characteristics of Pine oil blended with Kapok Methyl Ester in different proportions were tested in a single cylinder diesel engine to exclude the use of fossil diesel completely. In which, for the blend B25P75 the brake thermal efficiency of the engine was increased by 8% in comparison with diesel. The reduction in HC, CO and smoke emission is 14.9%, 43.2% and 33.4% respectively in comparison with the blend B50P50 where the values are 12.5%, 8.1% and 18.9% for similar studies. In dual biofuel strategy using low viscous oils, B50 could be regarded as the optimum blend ratio which is feasible for long term usage in diesel engines with some additives [11]. Experimental studies on combustion, performance and emission characteristics were carried out on a single cylinder, naturally aspirated and variable compression ratio diesel engine using conventional diesel fuel and different blends like B100T0, B90T10, B70T30 and B50T50 of Jatropha biodiesel and turpentine oil. The tested blends were found to be a greatest substitute to diesel fuel in all aspects such as emission and performance [12]. Further the blend B50T50 at a compression ratio of 20:1, results in 2.17% increase in brake thermal efficiency and 13.04%, 17.5%, 4.21% and 30.8% decrease in CO, HC, NOx and smoke opacity respectively while CO2 was observed to increase by 11.04%. The effect of Melaleuca Cajuputi Oil (MCO) and Refined Palm Oil (RPO) in a four stroke, single cylinder diesel engine was investigated and the regression analysis was carried out to identify the optimum blend ratio. For the optimum hybrid biofuel blend RPO32MCO68, incylinder peak pressure, NOx and the smoke opacity were dropped by 10.7%, 17.3% and 64.5% respectively at maximum engine speed [13]. Neat Rubber seed Oil (RSO) and Babassu Oil (BSO) blend was used to study the performance and emission characteristics of a twin cylinder, direct injection diesel engine. Rubber seed oil and babassu oil were blended in various proportions of 75:25, 50:50 and 25:75 and tested at a constant speed of 1200 rpm. With the optimum blend R50B50, 20% 2
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has lower viscosity, lower boiling point, lower cetane number, higher calorific value and high latent heat of vaporization than diesel. However, the higher self-ignition temperature of pine oil hampers its direct use in diesel engines. Hence it is decided to blend the pine oil with the methyl esters of soapnut oil at different proportions to balance most of the properties and to bring it closer to petro diesel. Recently, researchers turned their attention to use lower viscosity and lower cetane index fuels like eucalyptus oil, pine oil and camphor oil in Compression Ignition (CI) engines [17]. By using such fuels, the atomization, evaporation and air/fuel mixing process can be improved. Moreover, it creates sufficient delay time and the fuel to air equivalence ratio is reduced to decrease the soot emission without compromising. Experiments were conducted on CI engine using diesel, palm oil biodiesel blends with turpentine oil at 10, 20, 30 and 40 percentages by volume [18]. The fuel characterization study revealed that the low viscosity of turpentine oil makes combustion process of biodiesel easier with no unburned hydrocarbon and carbon monoxide emissions. Similarly low flash point makes fuel to catch fire rapidly with no ignition delay and the higher calorific value is useful in giving more power output. With this scope, this experimental work was carried out to blend the low viscosity, low cetane indexed pine oil with the high viscosity, high cetane indexed soapnut oil methyl ester. Addition of soapnut oil methyl ester with pine oil increases the flash point of pine oil blend. Hence it is safer to store the blends as compared to pine oil alone.
by volume of an oxygenated additive Diglyme (DGE), which has a higher cetane number and latent heat of vaporization was added [14]. The addition of 20% diglyme with R50B50 blend improved combustion and increased BTE by 6% at full load condition. The addition of diglyme also reduced harmful emissions like HC, CO and smoke opacity with a slight increase in NOx emission. Most of the research based on biodiesel has been conducted in laboratories using the heavy duty highway and stationary engines, but little attention was given to off-road engines. The idling speed of offroad engines are relatively low, only a small amount of fuel is supplied in order to maintain the engine crankshaft revolution and the combustion efficiency drops significantly which results in higher hydrocarbon emissions [15]. The literature survey reveals that the usage of dual biofuel (100% biofuel) in the automotive diesel engines is very limited. Detailed experimental studies are still needed to counter the short comings of increased NOx emission with the usage of biodiesel. This paper summarizes the performance, combustion and emission characteristics of soapnut oil methyl esters and its blends with pine oil (hybrid biofuels) in a tractor diesel engine (off-road vehicles). 2. Materials and methods 2.1. Fuel preparation Soap nuts are well-known worldwide in different names such as soapberry, washing nuts, soap nut shells, wash shells, Ritha, Chinese soapberry and many more. There are several varieties of soapnuts found in India, Indonesia, Pakistan, China, many parts of Europe, U.S and few countries in the eastern hemisphere. Sapindus Mukorossi and Sapindus Trifoliatus are the two major species found in southern India. The soapnut is considered as the third most productive vegetable oil producing crop in the world, after algae and oil palm, having significant potential for biodiesel production [16]. The soapnuts for this research were purchased in open markets in their dried form and de-shelled to obtain the oil containing seed. The seeds were de-hulled to clean and separate the oil containing kernels. A cold pressed oil expeller was used to crush the kernels and squeeze the oil using friction and continuous pressure. The extracted oil was cleaned and processed to remove impurities such as dirt and plant matters. Soap nut oil biodiesel was produced by base catalyzed trans esterification reaction as it is the most economical process, requiring only low temperatures and producing 98% conversion yield. Esterification was carried out using 0.50% KOH w/w of oil, 6:1 M ratio of methanol to oil at a reaction temperature of 60 °C for a duration of 1 h. Pine oil is an odorous, colorless, flammable biofuel obtained from the pine needles by steam distillation process. The viscosity, boiling point and flash point of the pine oil are lower, when compared to that of diesel and the calorific value is comparable to diesel. Hence it can be directly used in diesel engines without transesterification. In the present work, the readily available pine oil was purchased from chemical dealers, the fatty acid composition of the neat pine oil was examined by using GC–MS at Sophisticated Analytical Instruments Facility, IITM, Chennai, India. The results revealed that the major component present in the pine oil is α-terpineol (C10H18O) and α-pinene (C10H16) with simple molecular structure and lower molecular weight than diesel. The hybrid biofuel blends with different combination of pine oil and soapnut biodiesel namely P100SNB0 (100:0%), P75SNB25 (75%:25%), P50SNB50 (50%:50%), P25SNB75 (25%:75%) and P0SNB100 (0:100%) were prepared on volume basis.
2.3. Experimental setup The engine used for this experimental work is Simpson’s S217 twincylinder CI engine used in agricultural tractors. The engine develops a maximum power of 15 kW at 1500 rpm. The engine is coupled with an eddy current dynamometer of Accurate make for loading. The compression ratio of the engine is 18.5:1 and a hemispherical-type combustion chamber is used to create the necessary swirl. The detailed specifications of the engine are listed in Table 2. A mechanical-type fuel injection system with a multi hole nozzle injector is used. The fuel injection timing is fixed at 23°bTDC and the constant injection pressure is maintained at 200 bar throughout the test. The time taken for 20 cc of fuel consumption was noted manually using a burette and stopwatch for calculating total fuel consumption. The air flow rate was measured using an orifice meter fitted with a U-tube manometer in the intake air supply system. Fig. 1 shows the schematic diagram of the experimental setup. In-cylinder combustion pressure and its cyclic variations were obtained using Kistler 701A pressure transducer mounted over the cylinder head and the corresponding crank angle was measured through crank angle encoder placed in the crankshaft. The combustion parameters such as heat release rate and ignition delay were measured using the software Engine Performance Analyzer EPA 1.0.1. In the present study, exhaust emissions such as CO (Carbon monoxide), CO2 (Carbon dioxide), and O2 (Exhaust oxygen) are measured in terms of percentage volume. The HC (Unburnt hydrocarbon) and NO (Oxides of nitrogen) are measured in terms of parts per million (ppm) using AVL 444 di gas analyzer based on Non Dispersive Infra-Red (NDIR) principle. The smoke opacity was measured using AVL 432C smoke meter. 2.4. Experimental procedure and uncertainty analysis Before starting the experiment, the engine was allowed to run at 1400 rpm without load for 30 min so as to attain the steady state conditions. At the steady state conditions, the base test was carried out using diesel as fuel at different loads. The engine was loaded at 0%, 25%, 50%, 75% and 100% progressively in steps by controlling the current applied to the eddy current dynamometer. When changing engine load, the rack position of fuel pump is adjusted to regulate the fuel supply so that a constant speed of 1400 rpm is maintained.
2.2. Fuel properties The physical and chemical properties of the biofuel blends were determined as per ASTM standard and tabulated in Table 1. The pine oil 3
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Table 1 Properties of pine oil and soapnut biodiesel blends compared with diesel. Parameter 3
Density at 15 °C (kg/m ) Viscosity at 50 °C (mm2/s) Flash point (°C) Lower calorific value (kJ/kg) Cetane No.
Diesel
P100
SNB100
SNB25P75
SNB50P50
SNB75P25
Test method
832 3.42 52 40,290 53
847 1.2 36 41,848 22
868 3.6 158 37,723 56
851 1.8 67 40,816 30
857 2.4 97 39,785 39
862 3.0 127 38,754 47
ASTM ASTM ASTM ASTM ASTM
D1298 D445 D93 D240 D613
uncertainty of the various equipments used for this experimental study as shown in Table 3.
Table 2 Test engine specifications. Model
Simpsons S217 tractor engine
Type Cooling system No of cylinders Bore X stroke Compression ratio Cubic capacity Rated power Fuel pump Dynamometer Pressure pick up
Inline direct injection diesel engine, naturally aspirated Water cooling 2 91.44 X 127 mm 18.5:1 1670 C.C 15 kW at 1500 rpm Mico-Bosch Inline pump Eddy current Kistler 701A
3. Results and discussion 3.1. Brake specific fuel consumption The brake specific fuel consumption (BSFC or SFC) of the engine is influenced by the properties of fuel, engine design and operating conditions. The Fig. 2 shows the variation of BSFC with respect to load for diesel, pine oil and pine oil-soapnut methyl ester blends. There is a significant reduction in BSFC of pine oil than diesel beyond 50% load. This is due to its higher calorific value and lower viscosity of pine oil than diesel fuel and other biofuel blends. Based on the volume of soapnut biodiesel in the blend, the calorific value decreases considerably and thereby increasing the brake specific fuel consumption. From the experimental results, it was inferred that all the biofuel blends (P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100) produce optimum results at full loads. A reduction of 18% of BSFC was observed in the blend P75SNB25 and P50SNB50 at full load condition than diesel.
Whenever, the fuel is changed the engine was allowed to run for about 15 min to attain steady state condition with the new fuel before measurements were taken. The experiments were repeated for all the test fuels, three trials were conducted for each loading and finally the average values were taken for calculations. Calculations were made to find out the Specific fuel consumption, Brake power, and Brake thermal efficiency for all the fuel samples (Diesel, P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100) and the engine emissions were also noted. To ensure the legitimacy of the measured values, uncertainty analysis [19] was carried out based on the percentage
Fig. 1. Schematic of experimental setup. 4
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Table 3 Uncertainty of the measuring instruments/equipments. Sl. No.
Instrument
Make
Type
Accuracy
% Uncertainty
1 2 3 4 5 6 7 8 9 10
Pressure sensor Crank angle encoder Load indicator CO HC CO2 NOx Smoke meter Burette Orifice meter
Kistler
Piezo electric sensor Magnetic pickup type Strain gauge type load cell NDIR principle NDIR principle NDIR principle NDIR principle Hatridge smoke meter Volumetric measurement of fuel U tube manometer
± 0.5 bar ± 1o ± 0.1 kg ± 0.02% ± 20 ppm ± 0.03% ± 10 ppm ± 1% ± 0.1 cm3 ± 1 mm
±1 ± 0.2 ± 0.2 ± 0.2 ± 0.2 ± 0.15 ±1 ±1 ±1 ±1
AVL AVL AVL AVL AVL
444 444 444 444
digas digas digas digas
thermal efficiency. For the blends P50SNB50, P75SNB25 and P100SNB0, the brake thermal efficiency was increased by 8%, 10% and 13% respectively at full load condition compared with diesel. 3.3. Cylinder pressure and heat release rate Variation of cylinder pressure with respect to crank angle for the different biofuel blends and diesel at full load is presented in Fig. 4. No significant differences in peak cylinder pressure were noted within biodiesel blends. The exhaust gas temperature and heat release rate of all the fuel blends were higher than diesel due to the better combustion of fuel. The cylinder peak pressure for diesel, P100SNB0, P75SNB25, P50SNB50, P25SNB75 and P0SNB100 were recorded as 88.57 bar, 91.22 bar, 87.54 bar, 85.38 bar, 85.09 bar and 84.62 bar respectively. The cylinder peak pressure of P100SNB0 was 4–8% higher than the biodiesel blends and 3% higher than diesel. This could be due to the lower viscosity of pine oil that is a favorable property as a fuel for combustion through better vaporization and atomization. The increase in the soapnut biodiesel blend ratio decreases the peak pressure as compared to diesel and pine oil. This is due to the higher viscosity of the blends and lower heating value. Fig. 5, shows the heat release rate of methyl esters of soapnut oil and its blends of pine oil. The P100SNB0 shows higher heat release than diesel and other blends due to its higher calorific value.
Fig. 2. The variation of specific fuel consumption with load.
3.2. Brake thermal efficiency The brake thermal efficiency (BTE) of the engine is inversely proportional to the brake specific fuel consumption and depends upon the properties of fuel and combustion parameters. Due to high volatility and low viscosity of pine oil, atomization and vaporization are improved. Fig. 3 shows the variation of brake thermal efficiency with respect to engine load for diesel, pure pine oil and pine oil-soapnut biodiesel blends at different loads. From the Fig. 3, it is inferred that the increase in the percentage of pine oil in the blends, increases the brake
3.4. Exhaust gas temperature Diesel engine operates at higher compression ratio than the gasoline engines, which increases the temperature in the combustion chamber that results in higher exhaust gas temperature. The formation of NOx
Fig. 3. The variation of brake thermal efficiency with load.
Fig. 4. The variation of cylinder pressure with crank angle. 5
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Fig. 5. The variation of engine heat release rate with crank angle. Fig. 7. The variation of smoke emission with load.
3.6. Unburnt hydrocarbon emission Incomplete combustion of fuel leads to unburnt hydrocarbon (HC) emissions resulting from lean combustion and improper mixing of air and fuel inside the combustion chamber. The viscosity of fuel, ignition quality, spray characteristics and engine operating conditions play a vital role in the formation of HC emission. The variation of HC emission for the tested fuel at different engine loads are presented in the Fig. 8. HC emissions of Soapnut biodiesel blends are lower than that of pure pine oil owing to post flame oxidation. Due to the excess oxygen present in the plant based oils and higher the cetane number, the complete combustion is ensured. From the experimental results, it was observed that the reduction of 40%–60% of Unburnt hydrocarbon emission at full load for the blends P75SNB25 and P50SNB50 than diesel.
3.7. Carbon monoxide emission Fig. 6. The variation of exhaust gas temperature with load.
The carbon monoxide (CO) emission is generally formed when there is insufficient oxygen for the combustion of fuel. Some other factors affecting the CO emission are Cetane number, carbon-to- hydrogen ratio of the fuel used [20]. Diesel engines working with excess air normally emits lower CO. The carbon monoxide emission of all the test fuel increases as the load increases and is shown in Fig. 9. The diesel
emission depends mainly on the temperature of the combustion. At higher cylinder temperatures, the emissions of NOx is higher because more energy promotes the chemical reaction. Lower the temperatures, lower the NOx. The exhaust gas temperature rises as the load on the engine increases. The variation of exhaust gas temperature with respect to engine load is presented in Fig. 6. The diesel has the least exhaust gas temperature than all other biofuel blends at full load operation. The exhaust gas temperature of P100SNB0 is slightly lower than diesel at higher loads. Increasing biodiesel percentage in the blends increases the exhaust gas temperature by 5%–20% due to excess oxygen present in the soapnut biodiesel.
3.5. Smoke density Smoke emission increases with the increase in engine load due to overall richer fuel-air ratios. Hence, engine power is normally specified based on the maximum tolerable smoke density to curtail the black smoke emissions from engine. The smoke opacity indicates the soot content on exhaust gas, it is also a component of particulate matter. The variation of smoke emission with respect to engine load is presented in Fig. 7. The smoke opacity of all the tested fuels are lower than that of diesel at all the load. Hence it can be concluded that the blends P75SNB25 and P50SNB50 would be better blend from the view point of smoke level.
Fig. 8. The variation of hydrocarbon emission with load. 6
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4. Conclusions The current work focusses on the salient features in the usage of hybrid biofuel pine oil-soapnut oil methyl ester blends in a tractor diesel engines thereby swapping the use of conventional diesel fuel completely. The fuel properties of pine oil is unique and superior to conventional diesel whereas for soapnut biodiesel, it is similar to other edible and non-edible biodiesel fuels. The blends also have similar physical and chemical properties as per the ASTM biofuel standard and favorable for diesel engine operation. The concept of blending low viscous neat pine oil with the high viscous soapnut oil methyl ester reduces the cost of fuel substantially. The lower cetane value of pure pine oil could be balanced by higher cetane value of soapnut oil methyl ester so as to achieve better combustion. The following conclusions were made with respect to engine performance, combustion and emission characteristics.
• For the blends P100SNB0, P75SNB25 and P50SNB50, the increase in Fig. 9. The variation of carbon monoxide emission with load.
• • • • •
brake thermal efficiency of about 13%, 10% and 8% respectively was observed at full load condition compared with diesel. All the biofuel blends (P100SNB0, P75SNB25, P50SNB50 and P25SNB75) offers enhanced fuel economy beyond 50% load. A reduction of 18% in BSFC was observed for the blend P50SNB50 at full load condition than diesel. The cylinder peak pressure for P50SNB50 was recorded as 85.38 bar which is slightly lesser than diesel. The exhaust gas temperature for the blends P75SNB25 and P50SNB50 is similar to that of diesel at higher loads. There is a reduction of 40% in unburnt Hydrocarbon emission with the blends P75SNB25 and P50SNB50 as compared to diesel at full load. The Carbon monoxide emission for the blend P75SNB25 is lower by 6% than all the test fuels at full load condition. The increase in NOx emission of about 3%–5% was found for the blend P75SNB25 at low loads compared with diesel. It is observed that the blends P100SNB0, P75SNB25, P50SNB50 and P25SNB75 have smoke emission less than diesel up to 75% load and almost same as that of diesel at full load.
The experimental results proved that the hybrid biofuel blend P75SNB25 can be considered as a potentially good substitute for the tractor diesel engine. Overall, the performance, combustion and emission characteristics of the tested fuels showed better results than conventional biodiesel fuels and its blends with diesel. The homogeneous composition of two or more biofuels facilitate their use in advanced engine concepts such as HCCI, Lean burn engines and LHR engines. The hybrid biofuel approach is highly compatible with the long term strive towards advanced and more efficient engines.
Fig. 10. The variation of NOx emission with load.
and P75SNB25 has almost same value of CO emission up to 50% load and beyond that the CO emission is very lower than diesel, P100SNB0 and other higher blends. From the experimental results, it can be concluded that P75SNB25 gives better result in terms of CO reduction at higher loads. The obtained CO emission results are similar to the results achieved in a F1145 John Deere Front Mower off-road engine using waste cooking oil biodiesel blends with diesel at idling condition [21].
Declaration of Competing Interest 3.8. Oxides of nitrogen emission
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Oxides of Nitrogen (NOx) emission depends upon the time needed for the reaction to take place and the in-cylinder temperature. The variation of NOx emission with respect to engine load for different fuels are presented in Fig. 10. The NOx emission of P75SNB25 has shown very slight increase than diesel and low values than other soapnut biodiesel blends as well as pine oil. Increase in the pine oil content in the blend in turn increases the ignition delay due to the lower cetane number which leads to higher heat release rate. The better combustion of these blends increases the cylinder temperature and thereby increasing the NOx emission at all the loads. From the results, it can be concluded that the blend P75SNB25 has little increase in NOx emission of about 3%–5% in part load conditions.
References [1] Knothe G. Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Tech 2005;86:1059–70. [2] Giuliano Dragone, Bruno Fernandes, Antonio A. Vicente, Jose A. Teixeira, Third generation biofuels from microalgae. Current Research, Technology and Education Topics in Applied Microbiology and Microbial Biotechnology 2010; 1355-1366. [3] Agarwal Avinash Kumar. Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energy Combust Sci 2007;33:233–71. [4] Dubey P, Gupta R. Effects of dual bio-fuel (Jatropha biodiesel and turpentine oil) on a single cylinder naturally aspirated diesel engine without EGR. Appl Therm Eng 2017;115:1137–47. [5] Anand BP, Saravanan C, Srinivasan CA. Performance and exhaust emission of
7
Fuel xxx (xxxx) xxxx
V. Venkatesan and N. Nallusamy
[6] [7]
[8]
[9] [10]
[11]
[12]
[13]
2018;11(3146):1–20. [14] Edwin Geo Varuvel, Thiyagarajan Subramanian & Prakhar Khatri, Effect of diglyme addition on performance and emission characteristics of hybrid minor vegetable oil blends (rubber seed and babassu oil) in a tractor engine – an experimental study, Biofuels, DOI: 10.1080/17597269.2017.1418568. [15] Pekula N, Kuritz B, Hearne J, Marchese AJ, Hesketh RP. The effect of ambient temperature, humidity, and engine speed on idling emissions from heavy-duty diesel trucks. SAE Paper 2003;01:01–0290. [16] Karmakar A, Karmakar S, Mukherjee S. Biodiesel production from neem towards feedstock diversification: Indian Perspective. Renewable Sustainable Energy Rev 2012;16:1050–60. [17] Kasiraman G, Nagalingam B, Balakrishnan M. Performance, emission and combustion improvements in a direct injection diesel engine using cashew nut shell oil as fuel with camphor oil blending. Energy 2012;47:116–24. [18] Venkateswara Rao P, Prabhakara Chary D. Diesel engine performance analysis with blend fuel of biodiesel and Turpentine oil as biofuel additive. Int J Eng, Sci Math 2018;7:176–82. [19] Holman JP. Experimental Methods for Engineers. McGraw-hill Publishers; 2012. ISBN 978-0-07-352930-1. [20] Gang Wu, Jiang Guohe, Yang Zhiyuan, Huang Zhijian. Emission characteristics for waste cooking oil biodiesel blend in a marine diesel propulsion engine. Polish J Environ Stud 2019;28:2911–21. [21] Guo Jing, Peltier Edward, Stagg-Williams Susan M, Carter Ray E, Krejci Alex J, Depcik Christopher. Waste cooking oil biodiesel use in two off-road diesel engines. ISRN Renewable Energy 2012;130782:1–10.
turpentine oil powered direct injection diesel engine. Renew Energy 2010;35:1179–84. Kean Andrew J, Sawyer Robert F, Harley Robert A. A fuel-based assessment of offroad diesel engine emissions. J Air Waste Manage 2011;50:1929–39. Vallinayagam R, Vedharaj S, Yang WM, Lee PS, Chua KJE, Chou SK. Combustion performance and emission characteristics study of pine oil in a diesel engine. Energy 2013;57:344–51. Devan PK, Mahalakshmi NV. A study of the performance, emission and combustion characteristics of a compression ignition engine using methyl ester of paradise oileucalyptus oil blends. Appl Energy 2009;86:675–80. Devan PK, Mahalakshmi NV. Utilization of unattended methyl ester of paradise oil as fuel in diesel engine. Fuel 2009;88:1828–33. Panneerselvam N, Ramesh M, Murugesan A, Vijayakumar C, Subramaniam D. Effect on direct injection naturally aspirated diesel engine characteristics fuelled by pine oil, ceiba pentandra methyl ester compared with diesel. Transp Res Part D 2016;48:225–34. Vallinayagam R, Vedharaj S, Yang WM, Lee PS, Chua KJE, Chou SK. Pine oil-biodiesel blends: a double biofuel strategy to completely eliminate the use of diesel in a diesel engine. Appl Energy 2014;130:466–73. Dubey P, Gupta R. Influences of dual bio-fuel (Jatropha biodiesel and turpentine oil) on single cylinder variable compression ratio diesel engine. Renewable Energy 2018;115:1294–302. Mat Sharzali Che, Idroas Mohamad Yusof, Teoh Yew Heng, Hamid Mohd Fadzli. Physicochemical, performance, combustion and emission characteristics of melaleuca cajuputi oil-refined palm oil hybrid biofuel blend. Energies
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