Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review

Journal of the Energy Institute xxx (xxxx) xxx

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Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review Maryom Dabi, Ujjwal K. Saha* Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 16 June 2018 Received in revised form 16 December 2018 Accepted 3 January 2019 Available online xxx

Vegetable oils have been identified as the promising alternative source to replace fossil based fuel in the compression ignition (CI) engine. It is renewable and possesses characteristics that is similar to that of the diesel. Biodiesel, transesterifiedform of vegetable oil (VO), is now being commercially used in CI engines. However, biodiesel production from VO involves use of alcohols and chemicals which results the need of skilled labor and investment for its production. In view of this, many studies are also being carried out on the direct use of VO in the engine. The direct use of VO oil in engine is as good as that of the diesel. The superior quality of diesel however makes it better performance in engine as compared to the vegetable oil. Preheating and blending of VO are found to be the most common solution to overcome its inferior properties. The use of preheated and blended VO is found to improve the engine overall performance. This paper is focused exclusively on the one-to-one basis of study pertaining to the effect of neat, preheated and blended vegetable oils on diesel engine performance and emission through supplementation of illustrative figures from the various experimental studies. © 2019 Energy Institute. Published by Elsevier Ltd. All rights reserved.

Keywords: Vegetable oils CI engines Preheating Blending Emission

1. Introduction Vegetable oils derived from plants, includes both edible and non-edible feed stocks such as cotton seed, corn, hazelnut, soybean, sunflower and others. Oil is extracted from the seeds either through the methods of mechanical, solvent or enzymatic extraction processes. The seeds are either sundried or oven dried before extraction [1]. Since the oil is extracted directly from vegetables, it is generally termed as straight vegetable oil (SVO) or crude filtered oil. Vegetable oil (VO) is composed of 90e98% triglycerides and small amount of mono and diglycerides. Triglycerides are esters of three fatty acids and one glycerol [2]. The most common fatty acids that are found in the vegetable oils are shown in Table 1 [2,3], that shows the nomenclature, structure, formula and molecular mass of fatty acid (FA). Fatty acids are classified into saturated and unsaturated based on the number of double bonds. A saturated fatty acid does not have any double bond while unsaturated fatty acids have one or more double bond. The composition of FA in vegetable oils is determined using gas chromatography. The typical composition of common fatty acids for the different feed stock is shown in Table 2 [4e10]. Stearic, oleic and linoleic fatty acids constitute the major composition of vegetable oils. Their composition varies with the feedstock. Canola, rapeseed, olive and hazelnut oil respectively are composed of 53.36, 64.4, 75 and 77.15% oleic fatty acid. While corn, cottonseed, poon, sunflower and soybean oil are composed of more than 50% linoleic fatty acid. In the study of Machacon et al. [5], coconut oil exceptionally found to have 9.5, 4.5 and 51% of caprilic, capric and lauric respectively, along with the common FAs. Even the same feedstock shows variations in the composition of FA. This variation in the composition may be due to the growing of feedstock at different parts of the world having different climatic and geographical conditions. Other than the FA composition, vegetable oils are generally characterized on the basis of their density, viscosity and calorific value. These properties have significant importance especially in the context of their applicability in CI engines. Table 3 [7,11e37] shows the density, viscosity and calorific value of oil derived from different feedstock. The average calorific value is in the range of 36e39 MJ/kg, while density and viscosity shows fluctuating values depending upon the temperature of oil. The same feedstock is showing different properties due to the variation in FA compositions.

* Corresponding author. E-mail addresses: [email protected] (M. Dabi), [email protected] (U.K. Saha). https://doi.org/10.1016/j.joei.2019.01.003 1743-9671/© 2019 Energy Institute. Published by Elsevier Ltd. All rights reserved.

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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Table 1 Common fatty acids found in VO [2,3]. FA Name (common)

FA Name (systematic)

Structurea

Formula

Molecular Mass

Myristic Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Arachidic Eicosenoic Behenic Erucic Lignoceric

Tetradecanoic Hexadecanoic Hexadec-9-enoic Octadecanoic Cis-9-Octadecanoic Cis-9-cis-12 Octadecanoic Cis-9-cis-12, cis-15-Octadecatrienoic Eicosanoic Cis-11-eicosenoic acid Docosanoic Cis-13-docosenoic Tetracosanoic

14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 22:0 22:1 24:0

C14H28O2 C16H32O2 C16H30O2 C18H36O2 C18H34O2 C18H32O2 C18H30O2 C20H40O2 C20H38O2 C22H44O2 C22H42O2 C24H48O2

228 256 254 284 282 280 278 312 310 341 339 369

a

xx:y indicates xx carbons in the fatty acid chain with y double bonds.

Vegetable oils are emerging as an alternative fuel, to replace/supplement diesel, in CI engines. Most of the studies and investigations recommend the applicability of vegetable oils in CI engines. The use of vegetable oils in engines results in the lower performance in comparison of diesel due to the inferior quality of former against the later. Vegetable oil has the characteristics of high density and viscosity with lower calorific value in comparison to the diesel. For making the vegetable oil compatible for use in engines, the viscosity is reduced either through preheating, blending or esterification of the vegetable oil. In preheating, the vegetable oil is heated to a certain value before injecting it into the engine cylinders. While in blending, vegetable oil is mixed with the diesel at the different proportion. The esterification of the vegetable oil yield ester is generally known as biodiesel. In esterification, vegetable oil reacts with alcohol (either methanol or ethanol) using sodium or potassium hydroxide as catalyst. As compared to vegetable oils, biodiesels have lower viscosity. The comparison of viscosities of vegetable oils and biodiesels derived from different feedstock has been shown in Table 4 [7,14,38e42]. Many reviews have been carried out on the use of using vegetable oils in the CI engines. Misra and Murthy [43] a carried out a comprehensive and critical review on the use of SVO in a diesel engine with reference to Indian conditions and international research work. The study reveals that the use of straight vegetable oil or in blend with diesel in a CI engine shows promising, especially in the tropical country like India, where it has a great potential. The potential lies on the better adaptively of diesel engines as tropical temperature lowers the viscosity of the vegetable oil. It also recommends the use of pre-chamber diesel engine and preheating of fuel. Sidibe' et al. [44] reviewed the state-of-the-art for use of SVO as fuel in diesel engines which was based on a bibliographic study. The study reveals the need of either upstream adaptions or engine modifications for using SVO in the diesel. The recommended upstream adaptions include dual fueling, blending up to 30% and preheating. It also suggested modification in fuel injection systems and combustion chamber. Dwivedi and Sharma [45] studied the oxidation stability index and cold flow properties of nine vegetable oil available in India, consisting of four non-edible and five edible vegetable oils. The best oxidation stability index, in decreasing order, was found with castor, mahua, neem and karanja oil. The cloud point and cold filter plugging point of non-edible vegetable oil, in decreasing order, was found with mahua, neem, karanja and jatropha. For the edible vegetable oil, it was in the order of castor, rapeseed, canola and soybean. No [46] reviewed the application of hydrotreated vegetable oils (HVO) to CI engines. The use of HVO results in appreciable reduction in the emission of particulate matters, hydrocarbon, carbon monoxide and oxides of nitrogen without any changes in engine or its control. Lawlor and Olabi [47] studied the effect of using pure plant oil, recovered vegetable oil and tallows in diesel engine with Table 2 Typical Fatty acid compositions of VO derived from different feedstock. Feed stock

Canola Coconut Corn Cottonseed

Hazelnut Jatropha Olive Poon oil Rapeseed Rubberseed Soybean

Sunflower

Fatty acid compositions (wt%)

References

14:0

16:0

16:1

18:0

18:1

18:2

18:3

20:0

22:0

24:0

0.11 18.5 0.09 e e e 0.79 0.04 0.1 e e e e e e 0.10 0.10 e e 0.08

6.45 7.50 11.17 12.00 28.00 11.67 23.13 5.50 12.80 5.00 22.4 3.49 10.2 11.75 10.58 10.26 10.80 6.00 6.80 5.33

0.27 e 0.15 e e e 0.20 0.08 0.90 e e e e e e 0.11 0.10 e e 0.12

2.54 3.00 2.20 2.00 1.00 0.89 2.28 2.00 5.90 2.00 7.30 0.85 8.70 3.15 4.76 3.52 3.20 3.00 3.26 3.45

53.36 5.00 31.80 25.00 13.00 13.27 19.08 77.15 39.70 75.00 16.42 64.40 24.60 23.26 22.52 26.55 25.20 17.00 16.93 37.13

29.81 1.00 52.36 61.00 58.00 57.51 52.50 14.86 39.20 18.00 45.89 22.30 39.60 55.53 52.34 51.04 53.00 74.00 73.73 52.01

5.63 e 0.91 e e e 0.22 0.04 0.50 e

0.42 e 0.40 e e e 0.29 0.04 0.30 e 6.47 e e e 0.36 0.23 0.40 e e 0.16

0.33 e 0.16 e e e 0.51 0.04 0.10 e e e e e e 0.26 0.50 e e 0.65

0.30 e 0.16 e e e 0.13 e 0.10 e e e e e e 0.27 0.20 e e 0.14

8.23 16.3 6.31 8.19 7.06 6.20 e e 0.13

Atmanlı et al. [4] Machacon et al. [5] Atmanlı et al. [4] Rakopoulos et al. [6] Rakopoulos et al. [6] Ramadhas et al. [7] Atmanlı et al. [4] Atmanlı et al. [4] Koder et al. [8] Rakopoulos et al. [6] Devan and Mahalakshmi [9] Ramadhas et al. [7] Ramadhas et al. [7] Ramadhas et al. [7] Canakci [10] Atmanlı et al. [4] Koder et al. [8] Rakopoulos et al. [6] Ramadhas et al. [7] Atmanlı et al. [4]

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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Table 3 Properties of VO derived from different feedstock. Feed stock

Heating Value (MJ/kg)

Density (kg/m3)

Viscosityf (cSt)

References

Canola Cashew nut Camelina sativa oil Corn

37.400 35.800 38.200 36.300 37.825 39.600 36.800 39.648 39.648 36.980 37.900 38.720 39.840 38.200 37.500 34.000 41.660 37.304 e 41.510 36.270 39.750 38.863 37.000 38.820 34.650 39.920 35.600 39.650 37.600 36.995 37.620 36.890 39.500 37.500 38.207 39.600 37.000 39.623 36.500 39.525 39.500 39.500 37.680 38.590

915.00b 958.10a 925.40a 915.00a 915.00 912.00 910.00a 912.00 914.00 920.00d 927.00a 913.00e 910.00a 932.92e 918.00 912.00 938.00 913.00 956.00 853.00 984.00c 864.50 904.00 925.00a 921.00 816.90e 893.00 934.00a 926.40f 914.00 912.00b 914.00 918.00 916.30 910.00 904.00 920.00 925.00a 914.00 920.00a 918.00 923.10a 918.00 900.00 904.40a

31.80 55.30 28.94 35.00 46.00 50.00 34.00 50.00c 50.00 33.38 38.8 53.00e 24.00 52.76e 37.00 27.84 35.98 27.84 59.84 1.06 04.18 16.23 37.18 32.00 56.00c 3.52 1.763b 38.20 49.70 39.50 23.91 39.50c e 44.52 66.2 46.42 65.00 33.00 65.00c 34.00 58.00c 34.20 58.00 52.00e 49.05

Bayındır et al. [11] Kasiraman et al. [12] Kruczynski [13] Rakopoulos et al. [14] Altin et al. [15] Ramadhas et al. [7] Rakopoulos et al. [14] Altin et al. [15] Raj et al. [16] Lujaji et al. [17] Abedin et al. [18] Hebbal et al. [19] Atmanli et al. [20] Pramanik [21] Chauhan et al. [22] Raheman and Phadatare [23] Agarwal and Rajamanoharan [24] Bajpai et al. [25] Shah and Ganesh [26] Ashok et al. [27] Sathiyamoorthi and Sankaranarayanan [28] Agarwal et al. [29] Agarwal et al. [29] Rakopoulos et al. [14] Altin et al. [15] Purushothaman and Nagarajan [30] Huang et al. [31] Abedin et al. [18] Devan and Mahalakshmi [9] Ramadhas et al. [7] Qi et al. [32] Altin et al. [15] Nwafor et al. [33] Agarwal et al. [29] Ramadhas et al. [7] Misra and Murthy [34] Ramadhas et al. [7] Rakopoulos et al. [14] Altin et al. [15] Rakopoulos et al. [14] Altin et al. [15] Karaosmanoglu et al. [35] Ramadhas et al. [7] Krishnamoorthy et al. [36] Milano et al. [37]

Cotton seed

Croton mogalocarpus Crude rice brawn oil Deccan hemp Hazelnut Jatropha Karanja

Lemon peel Lemongrass Linseed Mahua Olive kernel Opium poppy Orange seed Pine oil Pongamia oil Poon Rapeseed

Rice bran Rubber seed Soapnut Soybean

Sunflower

Waste cooking oil

a, b, c, d, e and f at the temperature of 15, 20, 27, 28, 30 and 40  C respectively.

reference to perspective of these fuels in Ireland. The study reveals the limited information quantified scientifically and vouch for more study in this field in order to establish the effects of these fuels on engine performance, engine degradation and suitable measures for optimize the diesel engine when fuelled with these fuels. The study also recommends the use of pure plant oil than biodiesel in the Ireland as it reduces the fuel production cost. Melo-Espinosa et al. [48] reviewed the use of emulsified animal fats and vegetable oils in diesel engine. Emulsified biofuels is found to improve in atomization process due to reduction in viscosity. The use of emulsified fuel increases ignition delay, specific fuel consumption, carbon monoxide and hydrocarbon emission. Capuano et al. [49] carried out a comprehensive review to evaluate the effect of direct use of waste vegetable oil (WVO) in the CI engines. The use of WVO reduces the torque, power and efficiency while it increases brake specific fuel consumption and ignition delay. They recommend the direct use of WVO than converting to biodiesel. No [50] studied the application of SVO in CI engines and gas turbines. In the study it was reported that 20% non-edible SVO blend with diesel as the optimum blend and optimal preheating temperatures of 60e85  C and 80e120  C respectively for edible and non-edible SVOs. The availability and distribution of vegetable oil resources in India and across world has been extensively covered in some of past studies [1,51e54]. In most of these reviews, the emphasis is mainly on overall outcome of investigations and present the summary of the studies. However, to have a clear understanding on effects of vegetable oil on engines, it needs to identify the parameters which are getting affected. Based on these parameters, the study is needed to be carried out to bring out the effect, cause(s) of effect and exceptional outcome at the different modes engine operations. The present review thus makes an attempt to analyze the engine performance and emission parameters that are affected due to use of the neat, preheated and blended vegetable oil in the engine. Brake thermal efficiency (BTE), brake specific fuel consumption (BSFC) and exhaust gas temperature (EGT) are the performance parameters considered while carbon monoxide (CO), oxides of nitrogen (NOX), hydrocarbon (HC) and smoke were considered for the analysis. The graphical results, recreated through extraction of data [55], have been used for the analysis.

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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M. Dabi, U.K. Saha / Journal of the Energy Institute xxx (xxxx) xxx Table 4 Viscosities of VO and biodiesel derived from different feedstock. Feedstock

Corn Cotton seed Jatropha Karanja Mahua Palm Rapeseed Rubber seed Soybean Sunflower

Viscosity at 40  C (mm2/s)

Reference

Vegetable oil

Biodiesel

35.1 34.0 49.9 46.5 37.84 41.0 39.5 66.2 33.0 34.0

4.5 4.00 5.65 4.41 5.24 4.56 4.50 5.81 4.10 4.40

Shehata et al. [38] Rakopoulos et al. [14] Reddy and Ramesh [39] Reddy et al. [40] Sonar et al. [41] Gad et al. [42] Ramadhas et al. [7] Ramadhas et al. [7] Rakopoulos et al. [14] Rakopoulos et al. [14]

2. Effects of neat vegetable oil in CI engines Many vegetable oils, in their neat form, have been tried and tested in CI diesel engines. Altin et al. [15] used oils, derived from sunflower, cotton seed, soybean, corn, opium poppy and rapseed to study the effect of these oils on performance and emission characteristics of diesel engine. Jatropha oil was used in some studies [21,22,56]. While de Almeida et al. [57], Hebbal et al. [19], Cetin and Yuksel [58], Agarwal and Rajamanoharan [24], Devan and Mahalakshmi [9], and Shah and Ganesh [59] respectively used the oil derived from palm, deccan hemp, hazelnut, karanja, poon, and karanja with sunflower. The long term test of the CI engine conducted under part load condition and speed of 1600 rpm for 50 h by Karaosmanoglu et al. [35] was fuelled by sunflower oil. Rapeseed oil was used in the investigation of Nwafor et al. [33] to study the effect of advanced injection timing. Purushothaman and Nagarajan [30] used orange oil to study the performance, emission and combustion behavior of the engine. The outcome of these studies has been summarized in the following sub-sections. 2.1. Brake thermal efficiency The use of neat vegetable oil in the engine results in the drop of engine's brake thermal efficiency [9,19,21,22,24,56,59e62]. It varies with feedstock used as shown in Fig. 1 [19,22,24]. The use of deccan hemp, karajna and jatropha oil respectively leads to drop of 3e13%, 3e11% and 7e12% BTE of the engine. This drop in BTE is due to the combined effects of lower calorific value, high viscosity and poor volatility of vegetable oil, in comparison to diesel, resulting in the poor combustion characteristics [9,19,21,22,59]. The higher viscosity of vegetable oil results in poor atomization and larger fuel droplets size in the fuel spray which leads to inadequate mixing of oil droplets and heated air [24,56]. However, in some studies [60,63], the BTE of engine is found to be slightly higher or equal to diesel when neat vegetable oil is used as a fuel. According to Nwafor [63] the viscosity of vegetable oil might have acted as a lubricant, as well as a sealant between the piston rings and cylinder wall falsifying the engine compression and leads to efficient combustion in diesel engines. 2.2. Brake specific fuel consumption The brake specific fuel consumption generally decreases with increasing engine load irrespective of fuel used. This is due to the relatively lower heat loss with the increasing engine loads [64]. The comparative BSFC of the typical vegetable oils against the diesel has been shown in Fig. 1 [19,22,24]. It follows a similar trend to that of the diesel with higher quantity across the all operating range of the engine. However, it goes up by 8e13%, 14e21%, and 24e31% respectively, as compared to diesel, when karanja, deccan hemp, and jatropha oil have been used in the engine. Similar trends of higher BSFC with the use of vegetable oils derived from different feedstock have been reported [9,19,21,22,24,56,57,59,61,62]. It is obvious that when a fuel with lower heating value (vegetable oil) is used in an engine, it is bound to consume more quantity of fuel to produce same unit of power as compared to the use of diesel having higher heating value fuel. Therefore,

Fig. 1. Effect of different vegetable oils on the BTE and BSFC of the engine.

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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vegetable oils need larger mass of fuel flows to maintain a constant energy input to the engine [9,56,57,59]. Along with lower heating value, the higher density and viscosity of vegetable oil is also responsible for higher BSFC. Higher density of vegetable oil leads to greater fuel flow rate for the same displacement of the plunger in the fuel injection pump leading to increase in the BSFC [21,22,24]. 2.3. Exhaust gas temperature Higher exhaust temperature is the indicative of the lower thermal efficiencies of the engine as lesser amount of the energy input in the fuel is converted to work [22]. In most of the investigations, vegetable oil as a fuel in engine gives higher exhaust gas temperature in comparison to diesel [9,19,22,24,57,59e62,65]. The comparative EGT of engine when diesel and vegetable oils are used is shown in Fig. 2 [9,19,60]. Poon oil, as compared to other vegetable oils, shows a larger EGT variation against that of diesel. The poor combustion characteristics of vegetable oils, attributed to their higher viscosity, results in the higher EGT [21,22]. However, Hebbal et al. [19] believed that the low volatility of vegetable oil effected the spray formation in combustion chamber leading to slow combustion. Devan and Mahalakshmi [9] further added that this higher EGT might be due to the presence of constituents with higher boiling points in poon oil (vegetable oil), than in diesel, which were not well evaporated at the time of main combustion phase and this continued to burn in the late combustion phase thereby increasing EGT. 2.4. Carbon monoxide emission The presence of carbon monoxide emission in the exhaust gases indicates loss in chemical energy of the fuel which is not being utilized fully to develop engine power [59]. The CO emission of engine increases with the increase in the engine load/brake mean effective pressure (bmep) as shown in Fig. 3 [9,57,59]. At higher load, richer fuel-air mixture is burnt resulting in more CO production [24,57]. However, in some investigations [9,45], it decreases in the intermediate and maximum loads and they have not cited the reason(s). Neat vegetable oil increases the CO emission throughout the operating range as compared to that of diesel. The viscosity of vegetable oil has been considered as the factor responsible for it. The higher viscosity of oil creates difficulty in fuel atomization leading to locally rich mixtures. This rich mixture results in incomplete combustion and produces CO due to lack of oxygen [9,19,22,24,57,59e61,65]. Shah and Ganesh [59] have further added the fact that spray cone angle reduces due to the higher viscosity of vegetable oil. This reduction in spray cone angle leading to less air entrainment which results in incomplete combustion and ultimately the CO formation. 2.5. Oxides of nitrogen According to Huang et al. [66], the primary sources of oxides of nitrogen in the combustion processes consists of thermal NOX, fuel NOX and prompt NOX. Thermal NOX, which is highly temperature dependent and formed through high temperature oxidation of nitrogen in combustion chamber, is the most recognized and relevant source from engine combustion. NOX emission in the engine increases with the increasing load [22,57,65,66]. With an increased load, more fuel is injected and combusted in the cylinder which results in higher gas temperature. This higher gas temperature leads to more NOX formation in the engine cylinder thereby higher NOX emission from the engine. The rate of NOX formation in the engine is primarily a function of combustion (flame) temperature, the residence time of nitrogen at that temperature, and the contents of oxygen in reaction regions in the combustion chamber [66]. As compared to diesel, the use of vegetable oil in the engine reduces the NOX emission [9,22,24,57,61,65] as shown in Fig. 4 [57,61,65]. The lower heating value of vegetable oil is believed to cause this reduction [9,22,65]. Agarwal and Rajamanoharan [24] further elaborated that because of the higher viscosity of vegetable oil, it is expected to have larger fuel droplet size. And this, larger fuel droplet size, will have longer combustion duration with significant energy release during the late burning phase. Because of this, the peak combustion chamber temperature is possibly lower due to lower heat release in the pre-mixed combustion phase as well as mixing controlled combustion phase, leading to lower formation and emission of NO. However, in the investigations of Yilmaz and Morton [60] and Shah and Ganesh [59], NOX emission was found to increase with the use of vegetable oil derived from peanut, sunflower and karanja. Yilmaz and Morton [60] assume that most vegetable oils contain small quantities of nitrogen containing proteins, which in addition to atmospheric nitrogen, releases extra

Fig. 2. Comparative EGT of vegetable oil against diesel.

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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Fig. 3. Trends of CO emission for vegetable oil against diesel in CI Engine.

NOX emissions through combustion. This might be a contributing factor for vegetable oils to have higher nitric oxide (NO) emissions than diesel fuel. While Shah and Ganesh [59] points out that the 13.35% and 9.34% oxygen content respectively by sunflower and karanja oil, can help in improving oxidation of nitrogen available during combustion process which leads to increase the combustion bulk temperature responsible for thermal NOX formation. They further added that higher bulk modulus of elasticity of vegetable oils (sunflower and karanja) leads to advanced injection timing which also contributes higher NOx emission. 2.6. Hydrocarbon emission The hydrocarbon emitted from the incomplete combustion of fuel are lower in partial engine load and it increases with the higher load. This is because of relatively less oxygen available for reaction as more fuel is injected into the engine cylinder at higher load of the engine [22,24,57,58,65]. The comparative illustration of HC emission in engine when diesel and vegetable oil is used as a fuel is shown in Fig. 5 [9,22,62]. It reflects a significant amount of HC emission when vegetable oil is used in the engine in comparison to diesel. Hebbal et al. [19] believed that the low volatility of vegetable oil might have affected the spray formation in the combustion chamber leading to slow combustion and formation hydrocarbon. In the opinion of Devan and Mahalakshmi [9], the higher viscosity of vegetable oil is responsible for higher HC emission. The higher fuel viscosity may lead to higher fuel spray droplet size which affects fuel spray quality. In some exceptional investigations, HC emission is found to be lower in engines when vegetable oil is used. However, they have not substantiated their findings. 2.7. Smoke emission Smoke is a by-product resulted from the incomplete combustion of fuel. As shown in Fig. 6 [9,19,56], it increases with the increase in engine load irrespective of the type of fuel used. The vegetable oil shows higher smoke emission as compared to diesel in the engine operating range [9,19,22,24,56,62]. This increase in smoke emission goes even beyond 100% to that of the smoke emitted by diesel. The bulky fuel molecules with higher viscosity and low volatility of vegetable oil results in poor atomization of fuel. This poor atomization leads to higher smoke emission with vegetable oil [24].

Fig. 4. Trends of NOX emission for vegetable oil against diesel in CI Engine.

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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Fig. 5. Trends of HC emission for vegetable oil against diesel in CI Engine.

3. Effects of preheated neat VO in CI engine The preheating of vegetable oil before its injection into the combustion chamber of engine is done to reduce the viscosity of the oil. The viscosity of oil drastically gets reduced with preheating. Fig. 7 shows the variation in the kinematic viscosity of vegetable oil and diesel at elevated temperature [41,62,67].The kinematic viscosity of mahua, rapeseed and jatropha oil is reduced by 81, 73 and 86% respectively when the oil is heated from 40 to 100  C. While diesel shows a little variation in the same range of temperature. In the most of investigations, the vegetable oils have been preheated in the range of temperature from 70 to 90  C. However, the optimal value of this preheated temperature range could not have been ascertained as mostly the studies have been done on a single fixed preheated temperature. 3.1. Brake thermal efficiency The BTE of engine is found to improve with the use of preheated vegetable oil in comparison to without preheating. However, it remains lower as compared to diesel. In Fig. 8(a) [24,56] the results of neat and preheated karanja and jatropha oil is illustrated. Preheating shows better results in the intermediate and higher engine loads. Preheating of karanja and jatropha oil respectively results in 11e24% and 2e4% higher BTE as compared to their respective neat oil. The preheating of oil reduces the viscosity which facilitates better atomization of fuel particles ensuring better combustion and improved BTE of the engine [41,56,60,62,68]. In the studies of Agarwal and Rajamanoharan [24], the preheating of vegetable oil leads to higher thermal efficiency than that of diesel. This is because of the reduction in the viscosity and increase in volatility along with the oxygen content of vegetable oil that gives better fuel combustion which improves the BTE. However, in the study of Nwafor [63] the use of preheated oil deteriorates the engine efficiency. 3.2. Brake specific fuel consumption The preheating of vegetable oil results in the lower BSFC as compared to neat vegetable oil [24,41,56,62]. The typical results when jatropha and mahua oil were used is shown in Fig. 8(b) [41,56]. The reduction in BSFC is in the range of 3e8% and 4e7% respectively when preheated jatropha and mahua oil are used in the engine. This reduction in BSFC is due to preheating which reduces the oil viscosity leading

Fig. 6. Trends of smoke emission for vegetable oil against diesel in CI Engine.

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Fig. 7. Effect of preheating temperature on the kinematic viscosity of the fuel.

to better combustion in the engine [41]. However, it was higher in the study of Nwafor [63] when preheated rapeseed oil was used. Pradhan et al. [64] found it to be lower at 25 and 50% of engine load and relatively higher at engine load of 75 and 100%. 3.3. Exhaust gas temperature The exhaust gas temperature was generally found to be higher when preheated vegetable oil was used in the engine as compared to the neat vegetable oil [41,60,62,68e70]. The typical results when preheated jatropha and rapeseed oil were used against the neat oil is shown in Fig. 9 [62,69]. EGT increases by an average of around 31  C when preheated jatropha oil is used in the engine while preheated rapseed oil showing a very little variation. The increase in combustion gas temperature due to preheating of oil, as it increases the fuel temperature, is the probable cause for the increase in EGT [41,68]. 3.4. Carbon monoxide emission -vis neat oil on the CO emission has been illustrated in Fig. 10 The effect of preheated vegetable oil, jatropha and waste frying oil, vis-a [62,68]. It indicates a reduction in the CO emission with the preheating especially at higher engine loads [70]. The preheating reduces the oil viscosity results in better fuel atomization which improves the spray characteristics and better fuel air mixing. This ultimately leads to better combustion and reduced CO emission [64,68]. 3.5. Oxides of nitrogen The effect of preheated canola and waste frying oil on NOX emission is presented in Fig. 11 [60,68]. It reflects a relatively higher NOX in the exhaust when preheated vegetable oil is used. Similar results has also been reported [70]. Agarwal and Rajamanoharan [24] also reported a higher NO emission with the preheated karanja oil. However, mass of NO emission decreases with the increased engine load with lowest emission at the highest load of the engine. The increase in combustion gas temperature with the preheated fuel may be attributed to the increase of NOX [68]. In the investigation of Pradhan et al. [64], NOX emission found to be higher at

Fig. 8. Effects of preheated vegetable oil on BTE and BSFC of the engine.

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Fig. 9. Effects of preheated vegetable oil on EGT of the engine.

Fig. 10. Effects of preheated vegetable oil on CO emission of the engine.

0 and 25% of engine load while it lowers at 50, 75 and 100% of load with preheated jatropha oil as compared to the neat oil. This lower NOX emission at the higher engine load has been attributed to the instantaneous chemical reaction and low air-fuel ratio of preheated oil. 3.6. Hydrocarbon emission In comparison to the neat vegetable oil, the engine driven on the preheated vegetable oils, releases lower unburned hydrocarbon [41,62,64,70]. Typical results illustrated in Fig. 12(a) [62,64] indicates that preheating effectively mitigates the HC emission at the higher engine loads. It reduces by up to 34% when preheated jatropha oil is used. This reduction in HC emission may be due to more complete and

Fig. 11. Effects of preheated vegetable oil on NOX emission of the engine.

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cleaner combustion with better atomization of fuel molecules because of preheated oil [64]. Nwafor [69] reported a higher HC emission with the preheated oil compared to the neat oil while using rapeseed oil.

3.7. Smoke emission As compared to neat vegetable oil, the use of preheated vegetable reduces the smoke emission [24,56,62,68,70]. The preheating results in the reduction of fuel viscosity which subsequently improves spray, mixing of air-fuel and combustion characteristics [67]. Fig. 12(b) [24,56] illustrates the comparative smoke emission of neat and preheated jatropha and karanja oil. It indicates a higher degree of reduction at the intermediate loads while lower variation in the higher engine loads.

4. Effects of vegetable oil blends on engine Blending of vegetable oil with diesel is another method of improvising the vegetable oil property as a fuel. Unlike the preheating, which requires an extra arrangement for heating, in blending vegetable oil is simply mixed with diesel in certain proportion. The blending results in the reduction of oil viscosity. The typical reduction in the viscosities of jatropha, karanja, soapnut and poon oil blend has been shown in Fig. 13 [9,21,24,34].

4.1. Brake thermal efficiency Fig. 14 [9,21] shows the effect of poon oil (PO) and jatropha oil (JO) blends on BTE of the engine. It reflects a decrease in engine BTE with increasing percentage of vegetable oil in the blend. The effect is insignificant at the lower engine load. The increased volume of vegetable oil in the blend increases the fuel viscosity and reduces fuel volatility which results in the decrease of BTE of engine [9,21,25,34,62]. The vegetable blends upto 20% shows BTE comparable to that of diesel. Rakopoulos et al. [14], Bajpai et al. [25] and Rakopoulos et al. [6] reported even better BTE with vegetable oil than that of the diesel under 20% blend. However, in the investigation of Agarwal and Rajamanoharan [24] while using karanja oil, the blend upto 75% shows better BTE than that of diesel.

4.2. Brake specific fuel consumption The BSFC of engine increases with the increase in blend percentage of vegetable oil. In Fig. 15 [21,62], the blending of jatropha oil 30, 40, 50, 60 and 70% by volume increases the BSFC on average by 7, 15, 24 and 38% respectively. While the blending consists of 10, 20, 50 and 75% by volume of karanja oil increases it by an average of 4, 6, 12 and 17% respectively. This has been mainly attributed to the lower calorific value of vegetable oil as compared to that of diesel. The blending reduces the calorific value of fuel which resulted in higher BSFC [6,14,21,25,32,62].

4.3. Exhaust gas temperature The increasing percentage of vegetable oil in the blend increases the EGT of the engine [9,19,21,24,62]. The typical results of poon and jatropha oil blends used are shown in Fig. 16 [9,21]. With higher amount of vegetable oil in the blend, the engine shows a higher degree of gas temperature throughout the entire range of operation. As reported by Devan and Mahalakshmi [9], the presence of higher boiling point constituents in the vegetable oil is responsible for the higher EGT with vegetable oil and its blend. The details have already been described in the previous sections.

Fig. 12. Effects of preheated vegetable oil on HC and smoke emission of the engine.

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Fig. 13. Effects of diesel blending on viscosity of vegetable oil.

Fig. 14. Effects of vegetable oil blending on BTE of the engine.

Fig. 15. Effects of vegetable oil blending on BSFC of the engine.

4.4. Carbon monoxide emission The blending of vegetable oil with diesel is found to improve the CO emission in the engine although it remains higher than that of neat diesel. At the lower blend it is comparable to that of the diesel. The CO emission was found to be lower than that diesel at 5, 10 and 15% blends [25]. In Fig. 17 [9,62], the comparative results of diesel, vegetable oil and their blending with respect to CO emission are presented. The CO emission in the engine increases with the increase in the amount of vegetable oil in the blend. The increment is relatively high at the higher load. The increase amount of vegetable oil in the blend increase the fuel viscosity results poor atomization and combustion of fuel and higher CO emission. However, Qi et al. [32] reported a lower CO emission from 20 to 50% blend as compared to that of diesel at the high engine load.

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Fig. 16. Effects of vegetable oil blending on EGT of the engine.

4.5. Oxides of nitrogen The impact of vegetable oil blend, derived from soapnut and poon, on the NOX emission is shown in Fig. 18 [9,34]. It reveals that higher percentage of vegetable oil in the blend reduces the NOX. This trend has also been reported in the studies of Agarwal and Rajamanoharan [24] and Rakopoulos et al. [14]. This reduction in emission is probably because of the lower heating value of vegetable oil [9]. However, Qi et al. [32] found NOX emission to be higher for vegetable oil blends as compared to diesel at higher engine loads. The increase in engine load results in more fuel injection and higher combustion temperature in the combustion chamber due to which the effect of viscosity might not become a dominating factor and oxygen content in the reaction regions has an increased effect on the formation of NOX [32]. Similar higher NOX emission has been observed by Rakopoulos et al. [6] at 10 and 20% blend with higher NOx emission at higher blend. 4.6. Hydrocarbon emission As the engine powered on vegetable oil produces higher HC emission as compared to that of diesel fuel due to higher viscosity of the former than the later, it is obvious that the blending with diesel will reduce it. It is evident from Fig. 19 [34,62] that the HC emission reduces through blending vegetable oil with diesel. It decreases with the decreasing proportion of vegetable oil in the blends. Bajpai et al. [25] reported a lower HC emission, at 10% blend of karanja oil, as compared to diesel upto 70% of engine load. However, it increases beyond 75% load. 4.7. Smoke emission The use of higher blend vegetable oil in the engine results in the higher smoke emission as compared to that of diesel. This is due to the higher viscosity of vegetable oil which has already been elaborated in previous sections. The typical results of poon and deccan hemp oil blends are depicted in Fig. 20 [9,19]. However, lower blends give lower emission which is even better than the diesel. Misra and Murthy [34] reported that soapnut oil blend upto 30% results in lower smoke than that of the diesel upto 75% of engine load. Rakopoulos et al. [6] found it to be lower when 20% blend of sunflower, cotton, corn and olive oil were used in the engine. While Bajpai et al. [25] reported upto 15% for the karanja oil. The reduction in smoke emission at the lower blend has been attributed to complete and stable combustion of the blend as it contained a greater number of oxygen atoms [25].

Fig. 17. Effects of vegetable oil blending on CO emission of the engine.

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Fig. 18. Effects of vegetable oil blending on NOX emission of the engine.

Fig. 19. Effects of vegetable oil blending on HC emission of the engine.

5. Combustion analysis The combustion studies on the use of neat VOs in diesel engines [9,12,63,64,71] indicate a lower cylinder pressure and heat release rate (HRR) as compared to that of neat diesel. This has been attributed to the higher viscosity of VOs as compared to neat diesel. Higher viscosity leads to the poor atomization of fuel which reduces the air entrainment and air-fuel mixing rates [9,12,64]. Figs. 21 and 22 illustrate the variation of cylinder pressure and HRR with crank angle (CA) when poon oil and jatropha oil have been used. However,

Fig. 20. Effects of vegetable oil blending on smoke emission of the engine.

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Fig. 21. Variation of cylinder pressure and heat release rate at full load [9].

Fig. 22. Variation of cylinder pressure and heat release rate at full load [64].

Shah and Ganesh [59] reported a higher cylinder pressure and HRR with the use of sunflower and karanj oil as compared to that of diesel. This observation has been credited to the presence of higher amount of unsaturated fatty acids in sunflower and karanj resulting a longer ignition delay and allowing more time to form a flammable air fuel mixture leading to higher HRR and cylinder pressure. The higher bulk modulus and viscosity of VO has also been attributed as it advances the injection leading to higher cylinder pressure. Preheated VOs show better combustion characteristics as compared to that of normal VOs [63,64]. The preheating of oil reduces the fuel viscosity and helps to form the better combustible mixture. It also reduces the ignition delay and increases the combustion gas temperature. The variation of cylinder pressure and HRR with CA with the use of diesel, neat jatropha and preheated jatropha in engines are shown in Fig. 22. It indicates a higher HRR and cylinder pressure with preheated oil compared to the neat jatropha oil. Jatropha oil has been preheated to 70  C. In some of the investigations [9,32,34,71], it has been reported that the blending of VOs with diesel improves the combustion and this is found to be higher with larger percentage of diesel in the blend as the diesel has higher calorific value and lower viscosity in comparison to vegetable oils. Fig. 21 shows the variation of cylinder pressure and HRR when poon oil and its blend poon20 (20% poon oil and 80% diesel by volume) is used in the engine. With the use of poon20 blend in engine, the peak cylinder pressure of the engine increases to 63 bar as compared to neat poon oil which is 60 bar. While peak HRR increases from about 34.5 to 51 J/deg CA.

6. Conclusions and recommendations In this paper, the study was focused on understanding the effect of using neat and modified vegetable oils on the performance and emission of compression ignition diesel engines. The modified vegetable oil under consideration is the use of preheated neat vegetable oil and blending of vegetable oil with diesel in the engine. The salient features of this study are summarized as below:  The vegetable oils are characterized by high viscosity and lower heating value compared to that the diesel. The preheating of vegetable oil reduces its viscosity. The reduction at an average of approximately 80% is achieved at the temperature of 100  C. The normally the preheating temperature range of 70e90  C has been used in most of the studies. The blending of vegetable with diesel also improves the viscosity of the fuel. Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003

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 The BTE of engine drops when neat vegetable oil was used in the engine. This drop extends up to 14% which is due to the combined effects of lower calorific value, high viscosity and poor volatility of vegetable oil resulting in the poor combustion characteristics. The use of preheated oil improves the efficiency to some extent but lower than that of the diesel. Blending up to 20% shows efficiency comparable to that of the diesel. The efficiency was even better than diesel when blending under 20% were used in the engine. However, it decreases with the increase in the amount of vegetable oil in the blend.  The BSFC of engine goes up to 31% higher than diesel when vegetable oil was used due to the lower heating of vegetable oil, as compared to that of the diesel. This creates a need of larger mass fuel flow to maintain constant energy input to the engine. The preheating of vegetable oil results in the lower BSFC as compared to neat vegetable oil. The typical results show up to 8% reduction due to preheating. The increase in the percentage of vegetable oil in the blend increases the BSFC.  In most of the studies, vegetable oil as a fuel in engine gives higher EGT in comparison to diesel. This has been attributed to the higher viscosity which results in the poor combustion characteristics. In general, it was found to be higher when preheated vegetable oil was used in the engine as compared to the neat vegetable oil. This was due to increase in the combustion gas temperature. The increasing percentage of vegetable oil in the blend increases the exhaust gas temperature of the engine.  Neat vegetable oil increases the CO emission throughout the operation range as compared to that of diesel due higher viscosity of oil which creates difficulty in fuel atomization leading to locally rich mixtures and incomplete combustion. A reduction in CO emission with preheating especially at higher engine load is observed. The CO emission in the engine increases with the increase in the amount of vegetable oil in the blend. The increment is relatively high at the higher load. However, at the lower blend it is comparable or sometimes even better than that of the diesel.  The NOX emission in the engine reduces with the use of vegetable oil. In some studies, higher amount of NOX emission compared to that of the diesel has also been reported. As compared to the neat vegetable oil, preheated oil indicates relatively higher NOX in the exhaust. This is attributed to the increase in combustion temperature due to preheating. The higher percentage of vegetable oil in the blend reduces the NOX. However, opposite trend has also been reported with blending.  A significant amount of HC emission is observed when vegetable oil is used in the engine. The emission is reduced with the use of preheated oil. The increase in the percentage of vegetable oil in the blend increases the HC emission in the engine.  The vegetable oil shows higher smoke emission as compared to diesel in the engine operating ranges. This is due to the bulky fuel molecules with higher viscosity and low volatility of vegetable oil which results in poor atomization of fuel and leading to higher smoke emission. The use of preheated vegetable reduces the smoke emission as the preheating results in the reduction of fuel viscosity which subsequently improves spray, mixing of air-fuel and combustion characteristics. The higher amount of vegetable oil in the blend results in the higher smoke emission compared to that of the diesel. This review reveals that neat vegetable oil can been used in the engine although it may need some extra maintenance of engine aroused out of higher viscous nature of the oil. This may include regular inspection and cleaning of fuel injection system, running the engine with diesel mode at the starting and stopping of engine. By preheating and blending, vegetable oil will give better engine performance. The preheating may need additional system to heat the oil. In addition to that, the optimization of preheating temperature will be an important factor. As it will not be always true that higher the preheating temperature better will be the engine performance. The use of too high preheated oil may interfere injection system, combustion and emission characteristics of the engine. Moreover, maintaining of such higher preheated temperature itself will need extra investment to sustain. Therefore, the oil preheating temperature has to be optimized before implementing the scheme to the engine. The optimization can be worked out by running engine at different preheating temperature and by analyzing its effect on the engine performance and emission at respective preheating temperature. Blending will be simplest and best way to use vegetable oil in the engine as it does not involve any modification or addition of supplementary system to engine. In blending, certain volume of vegetable oil is simply mixed with diesel and it does not require any skill. This simple technology can be effectively utilized especially in the rural areas for driving the stationary engines used for irrigation and power supply. The need is to exploration and systematic exploitation of these natural fuel source. An estimate based on the National Policy on Biofuels 2009, Ministry of New and Renewable Energy, India is endowed with more than 400 species of plant that bearing non-edible oil seed. Through proper research, planning and management, these resources can be utilized to supplement the energy need. The blending of vegetable oil up to 20% with diesel makes a comparable performance with that of diesel. The supplement of even 10% can make a huge impact in economics of fuel supply and demand, which are in million dollars. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.joei.2019.01.003. References [1] A.E. Atabani, A.S. Silitonga, H.C. Ong, T.M.I. Mahlia, H.H. Masjuki, I.A. Badruddin, H. Fayaz, Non-edible vegetable oils : a critical evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production, Renew. Sustain. Energy Rev. 18 (2013) 211e245. [2] A. Srivastava, R. Prasad, Triglycerides-based diesel fuels, Renew. Sustain. Energy Rev. 4 (2000) 111e133. [3] A. Sanjid, H.H. Masjuki, M.A. Kalam, S.M.A. Rahman, M.J. Abedin, S.M. Palash, Production of palm and jatropha based biodiesel and investigation of palm-jatropha combined blend properties, performance, exhaust emission and noise in an unmodified diesel engine, J. Clean. Prod. 65 (2014) 295e303. [4] A. Atmanlı, E. Ileri, B. Yuksel, Experimental investigation of engine performance and exhaust emissions of a diesel engine fueled with dieselen-butanolevegetable oil blends, Energy Convers. Manag. 81 (2014) 312e321. [5] H.T.C. Machacon, S. Shiga, T. Karasawa, H. Nakamura, Performance and emission characteristics of a diesel engine fueled with coconut oil-diesel fuel blend, Biomass Bioenergy 20 (2001) 63e69. [6] D.C. Rakopoulos, C.D. Rakopoulos, E.G. Giakoumis, A.M. Dimaratos, M.A. Founti, Comparative environmental behavior of bus engine operating on blends of diesel fuel with four straight vegetable oils of Greek origin: sunflower, cottonseed, corn and olive, Fuel 90 (2011) 3439e3446. [7] A.S. Ramadhas, S. Jayaraj, C. Muraleedharan, Biodiesel production from high FFA rubber seed oil, Fuel 84 (2005) 335e340. [8] A. Koder, P. Schwanzer, F. Zacherl, H. Rabl, W. Mayer, G. Gruber, T. Dotzer, Combustion and emission characteristics of a 2.2L common-rail diesel engine fueled with jatropha oil, soybean oil, and diesel fuel at various EGR rates, Fuel 228 (2018) 23e29.

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M. Dabi, U.K. Saha / Journal of the Energy Institute xxx (xxxx) xxx

[9] P.K. Devan, N.V. Mahalakshmi, Performance, emission and combustion characteristics of poon oil and its diesel blends in a DI diesel engine, Fuel 88 (2009) 861e867. [10] M. Canakci, Performance and emissions characteristics of biodiesel from soybean oil, J. Automobile Eng. Proc. IMechE 219 (Part D) (2005) 915e921. [11] H. Bayındır, M.Z. Isık, H. Aydın, Evaluation of combustion, performance and emission indicators of canola oil-kerosene blends in a power generator diesel engine, Appl. Therm. Eng. 114 (2017) 234e244. [12] G. Kasiraman, B. Nagalingam, M. Balakrishnan, Performance, emission and combustion improvements in a direct injection diesel engine using cashew nut shell oil as fuel with camphor oil blending, Energy 47 (2012) 116e124. [13] S.W. Kruczynski, Performance and emission of CI engine fuelled with camelina sativa oil, Energy Convers. Manag. 65 (2013) 1e6. [14] C.D. Rakopoulos, K.A. Antonopoulos, D.C. Rakopoulos, D.T. Hountalas, E.G. Giakoumis, Comparative performance and emissions study of a direct injection Diesel engine using blends of Diesel fuel with vegetable oils or bio-diesels of various origins, Energy Convers. Manag. 47 (2006) 3272e3287. [15] R. Altin, S. Centinkaya, H.S. Yucesu, The potential of using vegetable oil fuels as fuel for diesel Engines, Energy Convers. Manag. 42 (2001) 529e538. [16] V.M. Raj, L.R.G. Subramanian, G. Manikandaraja, Experimental study of effect of isobutanol in performance, combustion and emission characteristics of CI engine fuelled with cotton seed oil blended diesel, Alexandria Eng. J. 57 (2018) 1369e1378. f, A. Bereczky, M. Mbarawa, Experimental investigation of fuel properties, engine performance, combustion and emissions of blends containing croton [17] F. Lujaji, L. Kristo oil, butanol, and diesel on a CI engine, Fuel 90 (2011) 505e510. [18] M.J. Abedin, H.H. Masjuki, M.A. Kalam, A. Sanjid, A.M. Ashraful, Combustion, performance, and emission characteristics of low heat rejection engine operating on various biodiesels and vegetable oils, Energy Convers. Manag. 85 (2014) 173e189. [19] O.D. Hebbal, K.V. Reddy, K. Rajagopal, Performance characteristics of a diesel engine with deccan hemp oil, Fuel 85 (2006) 2187e2194. [20] A. Atmanli, E. Ileri, N. Yilmaz, Optimization of diesel-butanol-vegetable oil blend ratios based on engine operating parameters, Energy 96 (2016) 569e580. [21] K. Pramanik, Properties and use of jatropha curcas oil and diesel fuel blends in compression ignition engine, Renew. Energy 28 (2003) 239e248. [22] B.S. Chauhan, N. Kumar, H.M. Cho, Performance and emission studies on an agriculture engine on neat Jatropha oil, J. Mech. Sci. Technol. 24 (2) (2010) 529e535. [23] H. Raheman, A.G. Phadatare, Diesel engine emissions and performance from blends of karanja methyl ester and diesel, Biomass Bioenergy 27 (2004) 393e397. [24] A.K. Agarwal, K. Rajamanoharan, Experimental investigations of performance and emissions of Karanja oil and its blends in a single cylinder agricultural diesel engine, Appl. Energy 86 (2009) 106e112. [25] S. Bajpai, P.K. Sahoo, L.M. Das, Feasibility of blending karanja vegetable oil in petro-diesel and utilization in a direct injection diesel engine, Fuel 88 (2009) 705e711. [26] P.R. Shah, A. Ganesh, Study the influence of pre-heating on atomization of straight vegetable oil through Ohnesorge number and Sauter mean diameter, J. Energy Inst. xxx (2017) 1e7. [27] B. Ashok, R.T.K. Raj, K. Nanthagopal, R. Krishnan, R. Subbarao, Lemon peel oil e a novel renewable alternative energy source for diesel Engine, Energy Convers. Manag. 139 (2017) 110e121. [28] R. Sathiyamoorthi, G. Sankaranarayanan, The effects of using ethanol as additive on the combustion and emissions of a direct injection diesel engine fuelled with neat lemongrass oil-diesel fuel blend, Renew. Energy 101 (2017) 747e756. [29] D. Agarwal, L. Kumar, A.K. Agarwal, Performance evaluation of a vegetable oil fuelled compression ignition engine, Renew. Energy 33 (2008) 1147e1156. [30] K. Purushothaman, G. Nagarajan, Performance, emission and combustion characteristics of a compression ignition engine operating on neat orange oil, Renew. Energy 34 (2009) 242e245. [31] H. Huang, W. Teng, Q. Liu, C. Zhou, Q. Wang, X. Wang, Combustion performance and emission characteristics of a diesel engine under low-temperature combustion of pine oilediesel blends, Energy Convers. Manag. 128 (2016) 317e326. [32] D.H. Qi, C.F. Lee, C.C. Jia, P.P. Wang, S.T. Wu, Experimental investigations of combustion and emission characteristics of rapeseed oilediesel blends in a two cylinder agricultural diesel engine, Energy Convers. Manag. 77 (2014) 227e232. [33] O.M.I. Nwafor, G. Rice, A.I. Ogbonna, Effect of advanced injection timing on the performance of rapeseed oil in diesel engines, Renew. Energy 21 (2000) 433e444. [34] R.D. Misra, M.S. Murthy, Performance, emission and combustion evaluation of soapnut oilediesel blends in a compression ignition engine, Fuel 90 (2011) 2514e2518. [35] F. Karaosmanoglu, G. Kurt, T. Ozaktas, Long term CI engine test of sunflower oil, Renew. Energy 19 (2000) 219e221. [36] V. Krishnamoorthy, R. Dhanasekaran, D. Rana, S. Saravanan, B.R. Kumar, A comparative assessment of ternary blends of three bio-alcohols with waste cooking oil and diesel for optimum emissions and performance in a CI engine using response surface methodology, Energy Convers. Manag. 156 (2018) 337e357. [37] J. Milano, H.C. Ong, H.H. Masjuki, A.S. Silitonga, W.H. Chen, F. Kusumo, S. Dharma, A.H. Sebayang, Optimization of biodiesel production by microwave irradiation-assisted transesterification for waste cooking oil-Calophyllum inophyllum oil via response surface methodology, Energy Convers. Manag. 158 (2018) 400e415. [38] M.S. Shehata, A.M.A. Attia, S.M.A. Razek, Corn and soybean biodiesel blends as alternative fuels for diesel engine at different injection pressures, Fuel 161 (2015) 49e58. [39] J.N. Reddy, A. Ramesh, Parametric studies for improving the performance of a Jatropha oil-fuelled compression ignition engine, Renew. Energy 31 (2006) 1994e2016. [40] S.M. Reddy, N. Sharma, N. Gupta, A.K. Agarwal, Effect of non-edible oil and its biodiesel on wear of fuel injection equipment components of a genset engine, Fuel 222 (2018) 841e851. [41] D. Sonar, S.L. Soni, D. Sharma, A. Srivastava, R. Goyal, Performance and emission characteristics of a diesel engine with varying injection pressure and fuelled with raw mahua oil (preheated and blends) and mahua oil methyl ester, Clean Technol. Environ. Policy 17 (2015) 1499e1511, https://doi.org/10.1007/s10098-014-0874-9. [42] M.S. Gad, R. El-Araby, K.A. Abed, N.N. El-Ibiari, A.K. El Morsi, G.I. El-Diwani, Performance and emissions characteristics of C.I. engine fueled with palm oil/palm oil methyl ester blended with diesel fuel, Egypt J Petrol 27 (2018) 215e219. [43] R.D. Misra, M.S. Murthy, Straight vegetable oils usage in a compression ignition engineda review, Renew. Sustain. Energy Rev. 14 (2010) 3005e3013. , J. Blin, G. Vaitilingom, Y. Azoumah, Use of crude filtered vegetable oil as a fuel in diesel engines state of the art: literature review, Renew. Sustain. Energy Rev. [44] S.S. Sidibe 14 (2010) 2748e2759. [45] G. Dwivedi, M.P. Sharma, Potential and limitation of straight vegetable oils as engine fuel e an Indian perspective, Renew. Sustain. Energy Rev. 33 (2014) 316e322. [46] S.Y. No, Application of hydrotreated vegetable oil from triglyceride based biomass to CI engines e a review, Fuel 115 (2014) 88e96. [47] V. Lawlor, A.G. Olabi, Review of scientific research regarding PPO, tallow and RVO as diesel engine fuel, Fuel 145 (2015) 25e38. rez, R. Sierens, S. Verhelst, Emulsification of animal fats and vegetable oils for their use as a diesel engine fuel: an [48] E.A. Melo-Espinosa, R. Piloto-Rodríguez, L. Goyos-Pe overview, Renew. Sustain. Energy Rev. 47 (2015) 623e633. [49] D. Capuano, M. Costa, S.D. Fraia, N. Massarotti, L. Vanoli, Direct use of waste vegetable oil in internal combustion engines, Renew. Sustain. Energy Rev. 69 (2017) 759e770. [50] S.Y. No, Application of straight vegetable oil from triglyceride based biomass to IC engines e a review, Renew. Sustain. Energy Rev. 69 (2017) 80e97. [51] A.M. Ashraful, H.H. Masjuki, M.A. Kalam, I.M.R. Fattah, S. Imtenan, S.A. Shahir, H.M. Mobarak, Production and comparison of fuel properties, engine performance, and emission characteristics of biodiesel from various non-edible vegetable oils: a review, Energy Convers. Manag. 80 (2014) 202e228. [52] A.E. Atabani, A.S. Silitonga, I.A. Badruddin, T.M.I. Mahlia, H.H. Masjuki, S. Mekhilef, A comprehensive review on biodiesel as an alternative energy resource and its characteristics, Renew. Sustain. Energy Rev. 16 (2012) 2070e2093. [53] M. Mofijur, A.E. Atabani, H.H. Masjuki, M.A. Kalam, B.M. Masum, A study on the effects of promising edible and non-edible biodiesel feedstocks on engine performance and emissions production: a comparative evaluation, Renew. Sustain. Energy Rev. 23 (2013) 391e404. [54] A.S. Silitonga, H.H. Masjuki, T.M.I. Mahlia, H.C. Ong, W.T. Chong, M.H. Boosroh, Overview properties of biodiesel diesel blends from edible and non-edible feedstock, Renew. Sustain. Energy Rev. 22 (2013) 346e360. [55] Rohatgi A. WebPlotDigitizer.https://arohatgi.info/WebPlotDigitizer. [56] B.P. Singh, Performance and emission characteristics of conventional engine running on jatropha oil, J. Mech. Sci. Technol. 27 (8) (2013) 2569e2574. [57] S.C.A. de Almeida, C.R. Belchior, M.V.G. Nascimento, LdSR. Vieira, G. Fleury, Performance of a diesel generator fuelled with palm oil, Fuel 81 (2002) 2097e2102. [58] M. Cetin, F. Yuksel, The use of hazelnut oil as a fuel in pre-chamber diesel engine, Appl. Therm. Eng. 27 (2007) 63e67. [59] P.R. Shah, A. Ganesh, A comparative study on influence of fuel additives with edible and non-edible vegetable oil based on fuel characterization and engine characteristics of diesel engine, Appl. Therm. Eng. 102 (2016) 800e812. [60] N. Yilmaz, B. Morton, Effects of preheating vegetable oils on performance and emission characteristics of two diesel engines, Biomass Bioenergy 35 (2011) 2028e2033. [61] P. Singh, J. Khurma, A. Singh, Coconut oil based hybrid fuels as alternative fuel for diesel engines, Am. J. Environ. Sci. 6 (1) (2010) 71e77. [62] D. Agarwal, A.K. Agarwal, Performance and emissions characteristics of Jatropha oil (preheated and blends) in a direct injection compression ignition engine, Appl. Therm. Eng. 27 (2007) 2314e2323. [63] O.M.I. Nwafor, The effect of elevated fuel inlet temperature on performance of diesel engine running on neat vegetable oil at constant speed conditions, Renew. Energy 28 (2003) 171e181. [64] P. Pradhan, H. Raheman, D. Padhee, Combustion and performance of a diesel engine with preheated Jatropha curcas oil using waste heat from exhaust gas, Fuel 115 (2014) 527e533.

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[65] Y.D. Wang, T. Al-Shemmeri, P. Eames, J. McMullan, N. Hewitt, Y. Huang, S. Rezvani, An experimental investigation of the performance and gaseous exhaust emissions of a diesel engine using blends of a vegetable oil, Appl. Therm. Eng. 26 (2006) 1684e1691. [66] J. Huang, Y. Wang, S. Li, A.P. Roskilly, H. Yu, H. Li, Experimental investigation on the performance and emissions of a diesel engine fuelled with ethanolediesel blends, Appl. Therm. Eng. 29 (2009) 2484e2490. [67] H. Hazar, H. Aydin, Performance and emission evaluation of a CI engine fueled with preheated raw rapeseed oil (RRO)ediesel blends, Appl. Energy 87 (2010) 786e790. [68] M. Pugazhvadivu, K. Jeyachandran, Investigations on the performance and exhaust emissions of a diesel engine using preheated waste frying oil as fuel, Renew. Energy 30 (2005) 2189e2202. [69] O.M.I. Nwafor, Emission characteristics of diesel engine running on vegetable oil with elevated fuel inlet temperature, Biomass Bioenergy 27 (2004) 507e511. [70] H. Hazar, H. Sevinc, Investigation of the effects of pre-heated linseed oil on performance and exhaust emission at a coated diesel engine, Renew. Energy 130 (2019) 961e967. [71] O.M.I. Nwafor, G. Rice, Performance of rapeseed oil blends in a diesel engine, Appl. Energy 54 (4) (1996) 345e354.

Please cite this article as: M. Dabi, U.K. Saha, Application potential of vegetable oils as alternative to diesel fuels in compression ignition engines: A review, Journal of the Energy Institute, https://doi.org/10.1016/j.joei.2019.01.003