Experimental study on the effect of cetane improver with turpentine oil on CI engine characteristics

Fuel xxx (xxxx) xxxx

Contents lists available at ScienceDirect

Fuel journal homepage: www.elsevier.com/locate/fuel

Full Length Article

Experimental study on the effect of cetane improver with turpentine oil on CI engine characteristics A.K. Jeevananthama, D. Madhusudan Reddya, Neel Goyala, Devansh Bansala, ⁎ ⁎ Gopalakrishnan Kumarb, Aman Kumara, K. Nanthagopala, ,1, B. Ashoka, ,1 a b

School of Mechanical Engineering, Vellore Institute of Technology, Vellore 632014, India Institute of Chemistry, Bioscience and Environmental Engineering, Faculty of Science and Technology, University of Stavanger, Box 8600 Forus, 4036 Stavanger, Norway

G R A P H I C A L A B S T R A C T

A R T I C LE I N FO

A B S T R A C T

Keywords: Turpentine oil Cetane enhancer SC5D CRDI engine Pilot injection EGR

The Turpentine oil has getting wider attention in recent times due to many significant benefits. In this present study, 20% Turpentine oil has been blended with 80% diesel fuel by volume. A novel cetane improver called SC5D has been doped with 20% biofuel at 2.5% and 5% concentrations. All the properties of all the blends are evaluated and it has been identified that the 5% of cetane improver has increases the fuel density. All the fuel samples have been tested in a single cylinder CRDI diesel engine under different pilot injection rate of 15% and 30% at 600 bar injection pressure. For the higher NOx emission condition, the 10% EGR has also been applied. The experimental study revealed that the addition of cetane improver with biofuel blends has shown comparable performance behaviours at all concentrations. Furthermore, the unburned hydrocarbon and smoke emissions are remarkably lower for biofuel blends at both the injection rate with cetane improver addition. Significant reductions has been noticed by 10% EGR addition for PI15% rate at 2.5% and 5% concentrations without much defect in other emissions. All the combustion behaviours have shown comparable behaviours with cetane improver addition and 10% EGR implementation with biofuel blends. Therefore, it can be concluded that the novel cetane improver could be used as additive with Turpentine oil in diesel engine applications.

Abbreviations: CI, Compression Ignition; BTE, Brake Thermal Efficiency; CRDI, Common Rail Direct Injection; BSFC, Brake Specific Fuel Consumption; BSEC, Brake Specific Energy Consumption; CO, Carbon monoxide; EGR, Exhaust Gas Recirculation; CHRR, Cumulative Heat Release Rate; HC, Hydrocarbons; ECU, Electronic Control Unit; HRR, Heat Release Rate; MFB, Mass fraction burnt; NOx, Oxides of nitrogen; TPO, Turpentine Oil; BP, Brake power; PM, Particulate Matter; PI, Pilot injection; B20, 80% of diesel + 20% of TPO; IP, Indicated pressure; CD, Combustion delay; ID, Ignition delay ⁎ Corresponding authors. E-mail addresses: [email protected] (K. Nanthagopal), [email protected] (B. Ashok). 1 B. Ashok and K. Nanthagopal contributed equally to this manuscript. https://doi.org/10.1016/j.fuel.2019.116551 Received 9 May 2019; Received in revised form 26 October 2019; Accepted 30 October 2019 0016-2361/ © 2019 Elsevier Ltd. All rights reserved.

Please cite this article as: A.K. Jeevanantham, et al., Fuel, https://doi.org/10.1016/j.fuel.2019.116551

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

1. Introduction

investigation, the 40% of pure Turpentine oil has been blend with diesel for diesel engine operation and results are revealed that brake thermal efficiency was better than diesel fuel by 2.5% without deteriorating emission behaviours [14]. From the above discussed technical literature, it was clearly evident that the Turpentine oil was suitable for partial replacement of diesel fuel due to its lower cetane number. Therefore, in many research works, the NOx emission was remarkably higher during biofuel blends operation. The autoigntion ability of Turpentine oil can be improved by the addition of suitable cetane improvers in a small quantity. Many cetane improvers’ additives have been used by the researchers like alkyl-nitrates, 2-eth-ylhexyl nitrate (EHN) in recent times for the improvement auto ignition quality of diesel and other biofuels [15]. Imdadul et al. [16] investigated performance and emission of n-butanol and diesel blends with 2- EHN as cetane improver. Reduced NOx emissions and increased BTE were observed by adding EHN to the blend, this was because of the free radicals in the combustion chamber that are provided by EHN, they speed up the oxidation process, reducing the ignition delay hence improved combustion. Mustafa [17] investigated the performance and emission characteristics for biodiesel fuelled, zirconia coated diesel engine mixed with cetane enhancing additive Di-tert-butyl peroxide (DTBP). The biodiesel used was prepared from palm oil and the additive was added 1% by volume. Significant reduction in NOx and CO levels was noted for the sample with additive because of large oxygen content of bio diesel and reduced ignition delay due to high cetane number of the additive. Very recently, Karthikeyan [18] evaluated the impact of Progallol cetane enhancer with Morginga Oleifera oil biodiesel. The study revealed that the brake thermal efficiency has improved upto 28.1% with reduction in brake specific fuel consumption (BSFC) at all concentrations. Rajkumar et al. [19] worked on experimental investigation of polymer based additive called SC5D that is mixed in different proportions with B15 (15% of Mamey Sapote oil + 85% of diesel) bio diesel in a variable compression ration CI engine. It has been noted that the BTE of B15 blend has been increased by 4.16% during 3 ml SC5D cetane improver addition. Furthermore, the CO, HC and smoke emissions are decreased by 10%, 16% and 11.12% respectively at same operating conditions. From the in-depth cited technical literatures, it has been noticed that the Turpentine could be a viable alternative fuel for diesel engine applications. All the previous studies have resulted in much improved performance when the Turpentine oil has been used upto 30% and after that the reverse results are witnessed. This is mainly because of lower cetane number of Turpentine oil which prevents them to use it for higher concentration with diesel fuel. Furthermore, many cetane improvers have been used by the researchers recently with diesel or biodiesel or any biofuel at small fractions and these have shown much better performance in a diesel engine without major modifications. Notably, only one technical study on SC5D diesel additive biodiesel blend is available and there is no other technical literature on SC5D cetane improver additive with any other low viscous biofuel. In particular, no technical reports on fuel injection variation for Turpentine oil blend with cetane improver. Therefore, in this present study, an impact of SC5D cetane improver additive with 20% Turpentine oil–80% diesel at 2.5% and 5% concentrations on common rail direct injection diesel engine characteristics. All the biofuel blends have been tested at two different pilot injection rates under variable loading conditions. The experimental results are compared to conventional diesel fuel. During experimental works, the NOx emission has been continuously monitored and 10% exhaust gas recirculation is applied for which the fuel sample produced higher NOx emission.

Today even with so much development in the area of renewable energy, still most of the automotive sectors are dependent on fossil fuels. With the ever-increasing population of the world, the utilization of energy in transportation has multiplied in the past three decades, and it is relied upon to be multiplied in the following thirty years [1]. This dependency is only increasing while the source is becoming scarcer. The problem is not just the scarcity even the emissions produced by the fossil fuels upon combustion like oxides of carbon and nitrogen are toxic, harmful and responsible for major climatic anomalies [2]. Biofuels are the renewable fuels which can be utilized in a certain quantity with petroleum products so that the harmful emissions could be greatly reduced [3]. In recent times, the direct production of renewable biofuels from various parts of the plants, waste resources and from other biological resources seem to be more attractive than the esterified biodiesel from different form of edible and non-edible oils [4]. Many renewable biofuels like lemon peel oil, lemon gross oil, pine oil, orange peel oil have low viscosity, inherent oxygen content and low flash point and comparable heating value compared to diesel fuel [5]. However, the calorific values of these kinds of biofuels are extremely lower than diesel which makes them unsuitable for complete replacement of diesel fuel [6]. Significant feasibility studies of these light viscous biofuels have been evident that all these biofuels showed remarkable improvement in diesel engine behaviours [7]. Ashok et al. [8] have made an comparative analysis on two biofuel blends in diesel engine performance characteristics. They have pointed out that the both the biofuels have produced much improved performance with remarkable benefits in engine emissions. However, this biofuels could not control the oxides of nitrogen emission (NOx) due to longer delay period that has enhanced by their poor ignition quality. Among the available biofuel, Turpentine oil is one of the renewable biofuel and it has been widely used as solvent in medical applications. This biofuel would be prepared from pine trees through steam distillation process and pyrolysis process. It had been used as fuel in many thermal systems in the early 1700s around the globe. Anand et al. [9] have reported that the Turpentine oil has better miscible property in diesel and this quality had not witnessed in other biofuels. Physically it looks yellow, obscure, dull, foul, water-immiscible fluid. Artificially, turpentine is inflammable, volatile and ignitable; and possesses 40% by weight of alpha-pinene. It is composed of 52–64% gamma–pinene alongside beta-pinene and other isometric terpenes [10]. There are considerable research works that have been carried on the turpentine as alternate fuels in CI engine applications. Anand et al. [11] have examined the suitability of Turpentine oil as fuel in a diesel engine as fuel through 50% volume addition with diesel. They have stated that the diesel engine fuelled with 30% Turpentine oil–70% diesel has increased the power output and heat release rate and the results are reversed by concentration of biofuel in the blend. Interestingly, all the Turpentine oil blends have shown remarkable reductions in carbon monoxide (CO), unburned hydrocarbon (UBHC) and smoke emissions. The reasons for this behaviour are due to the significant reduction in heating value of the blend. Karthikeyan and Mahalakshmi [12] used the Turpentine oil as fuel in dual fuel mode in a specially designed diesel engine. They have pointed out that the diesel engine performance was in better form upto 75% loading condition and afterwards, the results are not within satisfied limit. The experimental study has revealed that around 75% of diesel fuel replacement is quite achievable with minor modifications. Dubey and Gupta [13] used a blend of turpentine and Jathropa biodiesel to completely replace diesel in a CI diesel engine without any alterations. All the performance characteristics at different blend ratios showed improvement; also, emissions like NOx and CO were reduced at 50% blend ratio (BT50). This was mainly because of lesser burning time and increased ignition delay. Moreover, during full load it was observed that HC and smoke emissions reduced by 4.56% and 29.16% respectively, while CO2 emission is increased by 10.5%. In another

2. Material and methods This chapter focuses on the production of Turpentine oil and biofuels blends preparation methods. In this work, the newly obtained cetane improver SC5D has been used as additive with 20% of 2

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

is increase the availability of oxygen within the blend, which encourages improved combustion. Also the lower calorific value of B20 + 5% SC5D blend was found out to be lower than 2.5% blend, this fluctuation can be attributed to the lack of proper polymerisation within the blend because of the presence of excess amount of cetane additive. Another property that influences the combustion of the fuel is its viscosity, higher viscosity results in poor atomisation of the fuel, which reduces the quality of combustion. It is noted that the B20 + 5% SC5D blend has lower viscosity than B20 + 2.5% SC5D blend, the trend that is opposite of lower calorific value, this variation can affect the performance of the engine in an unpredictable manner. On the other hand, density apart from influencing the viscosity, also affects the emission characteristics of the fuel. Higher density generally leads to more particulate matter emissions because within the same volume of fuel more mass of the fuel is being burnt. As it can be contemplated from the table, addition of more cetane enhancer is increasing the density of the blend and it can cause both BSFC and particulate emissions to rise. The auto ignition ability of diesel and all biodiesel blends are estimated using Cetane Index correlation which is given below.

Turpentine oil–80% diesel by volume at 2.5 ml and 5 ml fractions. 2.1. Fuel production In this research work, the Turpentine oil has been purchased from the market which is prepared by steam distillation process as per the following procedure. The Turpentine oil is obtained from pinewood and it is initially separated from wood chips after they have been “cooked” in the kraft papermaking process as CST (crude sulphate turpentine). Wood chips are cooked in the bunch procedure, where turpentine is acquired by venting the digester and afterward isolating the strands and black alcohol from the turpentine and water inside a cyclone separator. The vapor blend of turpentine and water is then funneled to a condenser and thus to a partitioned tank, where the fluid and turpentine stages separate because of their density difference. The fluid undercurrent is channeled off, and the CST flood is likewise funneled off to storage tanks. The yield of CST is around 12 L for each ton of air-dried mash, and around 1500 tons of unrefined turpentine is delivered every year at Kinleith. The CST plant is a batch operation and a kettle associated with a distillation section is loaded up with rough turpentine and a vacuum is drawn while the energize is heated up to the point where the lightest mixes start to boil off. These “heads” are of no utilization as they contain generally water and light sulfurous compounds, and they are sent to an incinerator. When these heads have been driven off, temperature can be expanded and vacuum increased. As the pinenes boil off the reflux proportion can be expanded to improve the level of partition accomplished in the section. The distinction in volatility between the alpha and beta structures is adequate to allow very great detachment by distillation, yet to guarantee item quality in the least distillation time a little moderate cut of blended alpha and beta pinenes is taken. These moderate cuts are put away until adequate sum is held to make up a bunch for re-distillation. By and large time for a bunch distillation is around 20–24 h. An average charge would be around 15 m3 of turpentine offering up to 25% alpha-pinene and 45% betapinene.

Cetene Index = 454.74 − 1641.416 D+ 774.74 D2 − 0.554 T50 + 97.803 (log T50 )2 where D = fuel density at 15 °C in g/ml T50 = Temperature corresponding to the 50% point in the distillation curve in °C 3. Experimental setup The engine used to perform the testing was Kirloskar-TV 1 make with rated power output of 3.5 kW @1500 rpm engine speed. Engine’s technical specifications of the engine are presented in the Table 2. The setup comprises of single cylinder, four-stroke CRDI engine with an eddy current based dynamometer as shown in Fig. 1. The dynamometer functions as a loading device, a feat that is accomplished by switching the load resistances on or off. To improve the engine characteristic output the mechanical injection is converted into electronic injection by attaching the necessary components to the engine. The engine is mounted with programmable open ECU of make Nira i7r to manage and monitor all the actuators and sensors within the setup. To inject the fuel at required pressure a common direct rail injection system had to be fixed onto the engine since the standard mechanical injection mechanism cannot sustain the pressure required for the testing. Alterations were made to the fuel supply line to accommodate a high pressure inducing pump ahead of the mechanism used to filter the fuel. The common rail mechanism was fixed after it; this performs the job of a reservoir by maintaining the pressure of the fuel at required injection pressure. The rail has an attached pressure sensor and a pressure adjusting valve, which is connected to the ECU. Every time the sensor detects decrement in the injection pressure the valve opens and rail is injected with required amount of fuel to ensure that the pressure is maintained at required amount. A solenoid controlled injector consisting six holes is being used since it provides better control over the injection pressure. The completion of the setup is followed by calibration of the sensors and actuators that is recorded by ECU to safeguard full functioning of all the components. The most common application of this kind of engine was found in agricultural fields with multiple cylinders attached to the engine, but the flexibility and freedom it provides by giving various injection methods to choose from, makes it a viable choice for this research. Also this type of engine is suitable for turpentine oil because it has the function of EGR which can provide the solution for the problem of higher NOx emissions which is generally associated with biofuels.

2.2. Blends preparation After preparing the Turpentine oil, three biofuel samples have been prepared for the experimental investigation. Initially, the 20% of Turpentine oil is blended with 80% diesel by volume which is named as B20 blend. In a second phase, the SC5D cetane enhancer has been added with B20 fuel at 2.5 ml and 5 ml concentrations. These fuel samples are named as B20 + 2.5% SC5D and B20 + 5% SC5D respectively. After preparing all the three biofuel blends, these blends have thoroughly mixed with the help of mechanical stirrer at 1500 rpm in atmospheric conditions for 30 min duration. A stability of all B20 biofuels with and without cetane enhancer has been tested by standard gravitational technique through keeping these samples for three days. There has been no phase separation issue in all the biofuel samples and these fuel samples are very stable. 2.3. Fuel properties The properties of TPO blend and diesel along with cetane additive SC5D have been experimentally found out and are shown in the Table 1. All the properties have been evaluated as per the ASTM testing methods. These properties help in observing and understanding the basic trends and variation among the different samples. One of the properties that greatly influence the performance of the engine is lower calorific value (CV) of the fuel. As it can be observed that the lower heating value of B20 is slightly higher than diesel fuel. Furthermore, the addition of SC5D cetane enhancer with B20 fuel has not shown significant improvement with respect to concentrations. The addition of biofuel reduces the calorific value of pure diesel because of higher moisture content within these fuels, though what cetane enhancer does 3

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Table 1 Standard fuel properties for diesel, turpentine and it’s blend with ASTM standards of measurement. Properties

ASTM Std.

Diesel

B20

Turpentine oil

B20 + 2.5% SC5D

B20 + 5% SC5D

Name of the equipment

Density (kg/m ) Kinematic viscosity @ 40 °C (cSt) Flash point (°C)

D1298 D445 D93

846 3.1 66

848 2.7 52

850 2.5 41

868.5 2.8 35

870 3.1 38

Fire point (°C)

D92

76

59

43

38

40

Calorific value (kJ/kg)

D420

42,700

43,090

44,400

42,270

41,208

Cetane Index Latent heat of vaporization (kJ/kg)

D976 –

53 230

45 –

38 285

–

– –

Hydrometer Brookfield Amertek viscometer Pensky-Martens Flash point Apparatus Make: Micromech Instruments Pensky-Martens Flash point Apparatus Make: Micromech Instruments Digital Bomb calorimeter Make: Micromech Instruments – –

3

The sensors viz. cam position sensor, coolant temperature sensor, crank position sensor, rail weight sensor and mass-air stream sensor work in a joint effort with the actuators namely, Injector (Solenoid: 300–600 bar), Rail Pressure Controller and so forth. With the support of ECU to maintain and regulate engine performance. U tube manometer is used to quantify the parameter of air flow rate that is fixed in the path of the pipe through which air flows. To measure the combustion and performance productivity of the engine the software used is EngineSoft, developed by Apex Innovations Pvt Ltd. It assessed various parameters like BP, IP, frictional power, BMEP, IMEP, BTE, Mechanical efficiency, volumetric efficiency, SFC, Air fuel ratio and heat balance. To calculate in cylinder pressure variation piezo electric sensor was used. Stopwatch is used to determine the fuel consumption by recording the time needed

Table 2 Specifications of CRDI Engine used for testing. SI. No.

Parameter

Specification

1 2 3 4 5 6 7 8

Rated power Rated speed No. of cylinders Stroke length Bore diameter Cooling system Injector Fuel tank capacity

3.5 kW 1500 rpm Single 110 mm 87.5 mm Water cooled Solenoid, Six-Holed 15 L

Fig. 1. Constant speed, CRDI CI engine setup with pertinent sensors and DAQ software. 4

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Table 3 Accuracy and uncertainty of various measuring instruments. Instruments

Range

Accuracy

Uncertainty (%)

Digital Tachometer Dynamometer load cell Thermocouple Pressure pickup Rotary crank angle encoder U-tube manometer Burette system Exhaust Emission Analyser

0–10,000 rpm 0–60 kg 0–900 °C 0–110 bar 0–360° 0–500 mm 0–100 cc CO: 0–10% vol HC: 0–20000 ppm CO2: 0–20% vol NOx: 0–5000 ppm 0–10

± 10 rpm ± 50 g ± 1°C ± 0.1 bar ± 1° ± 1 mm ± 0.1 cc ± 0.01% ± 10 ppm ± 0.02% ± 10 ppm ± 0.1

0.2 0.2 0.2 0.1 0.2 1.0 1.0 0.2 0.2 0.2 0.2 1.0

AVL Smoke meter

for the consumption of 10 cc of fuel. For determination of exhaust gas emissions AVL Digas 444 exhaust gas emissions analyser was utilized. To measure to smoke content is exhaust AVL 437C smoke meter was used. Many precautionary measures were employed during testing to warrant the integrity of the experiment. The accuracy and uncertainty of all measuring instruments is listed in Table 3.

Fig. 2. Comparison of brake thermal efficiency against brake power.

to a crucial way to deal with making a decision about the engine operations and gives special bits of knowledge about the proficiency of the fuel utilized.

3.1. Experimental test procedure In this present study, the CRDI diesel engine is fuelled with conventional diesel fuel initially and then all biofuel samples are used. All the fuel samples have been used under various loading conditions of No load, 25%, 50%, 75% and 100% loads. Each fuel sample is performed for three times and the average readings are taken for performance analysis purpose. Since the study is focused on the impact of SC5D cetane enhancer on B20 fuel in diesel engine characteristics, the B20 blend with cetane enhancer also tested at same operating conditions. In this research work, the diesel, B20. B20 + 2.5%@PI15% and B20 + 5% @PI15% are injected at 600 bar injection pressure with 15% pilot injection rate along with 85% main injection rate under standard injection timing of 23° bTDC. In second phase of research work, the B20 + 2.5%@PI30% and B20 + 5%@PI30% fuel samples are injected at same injection pressure of 600 bar with 30% pilot injection rate and 70% main injection rate under same injection timing. During these fuel samples testing, the NOx emission is continuously monitored and it has been found that the higher NOx emission is observed for P15% rate. Therefore, the B20 fuel is tested under 10% cooled EGR condition and these testing conditions are named as B20 + 2.5%@PI15%–EGR10% and B20 + 5%@PI15%–EGR10%. The detailed experimental test matrix is presented in Table 4. Every fuel sample is performed at atmospheric conditions under 1500 rpm of engine speed.

4.1. Performance characteristics Various interpretations can be done from the performance characteristics of the CI engine. In the present sector the parameters, for instance, BTE, BSEC is discussed in progressively significant detail. 4.1.1. Brake thermal efficiency It is a general thought that how productively an engine is changing over the heat from fuel into valuable mechanical vitality. Fig. 2 demonstrates the variety of brake thermal efficiency (BTE) of different tried fuels over the engine loads. A general pattern that can be effectively watched is expanding BTE and this is because of increment in brake power yield with expanding load conditions at steady speed. As noted from the Fig. 2 that the brake thermal efficiency of B20 fuel is 2.46% higher than diesel fuel at maximum brake power. From the Table 2, it is evident that the net calorific value of B20 is substantially higher than diesel fuel and this has resulted in higher heat content and this has caused improved brake thermal efficiency. Notably, the kinematic viscosity of B20 is slightly lower than diesel fuel that enhances the better mixing process with air. On another hand, the addition of cetane enhancer in B20 at various concentrations shows the decrease in efficiency contrasted with B20 and this is due to an increment in density which causes high mass injection for a similar volume [18]. It is to be noted that an increase in pilot injection rate from 15% to 30% has reduced the BTE from 30.4% to 28.7% at same injection pressure of 600 bar for B20 fuel operation with SC5D cetane improver. As noted from the Table, the additions of SC5D at all concentrations increase the

4. Results and discussions The information is gathered by testing different blends in the diesel engine and is comprehensively separated into three classifications: Performance, Combustion and Emission behaviours. Every class speaks Table 4 Experimental test matrix followed in the present work. Test No

Test Abbreviations

Load

Fuel

Pressure (bar)

Pilot injection (%)

Main injection (%)

EGR (%)

1. 2. 3. 4. 5. 6. 7. 8.

Diesel B20 B20 + 2.5%@PI15% B20 + 2.5%@PI30% B20 + 2.5%@PI15%–EGR10% B20 + 5%@PI15% B20 + 5%@PI30% B20 + 5%@PI15%–EGR10%

Variable 0–100% Speed 1500 rpm

Diesel 20% TPO–80% diesel by volume

600 600 600 600 600 600 600 600

15 15 15 30 15 15 30 15

85 85 85 70 85 85 70 85

0 0 0 0 10 0 0 10

5

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 3. Comparison of brake specific energy consumption against brake power.

fuel density and reduce the calorific value and therefore low BTE has been observed. Furthermore, an increase in pilot injection rate from 15% to 30% has increased the fuel accumulation inside the combustion chamber which leads to incomplete combustion. However, the implementation of 10% EGR during B20 fuel operation has resulted in slight reduction in BTE at 2.5% and 5% of cetane enhancer addition compared to without EGR operation. This is due to the reduction if fresh air availability for combustion process which has played a dominant role in BTE reduction. 4.1.2. Brake specific energy consumption The impact of turpentine oil when blended with diesel on BSEC appears in Fig. 3. The variety in BSEC of diesel and turpentine blends pursues a diminishing pattern with the expansion in brake power. A higher BSEC is constantly wanted to imply that engine is utilizing less fuel to deliver a similar measure of work. At maximum power output, the BSEC of diesel fuel is 11.10 MJ/kWh and whereas for B20 fuel is 10.3 MJ/kWh. The reduction in BSEC is caused due to the reduction in net calorific value which increases the fuel consumption for developing same power output. On adding cetane improver to the B20 at various concentrations it was seen that blends with 5% SC5D cetane enhancer indicate more abatement in BSEC contrasted with the blends with 2.5% SC5D at full load condition. The BSEC contrasts between these test fuels are to a great extent because of different calorific values while minor effect is because of change in pilot injection quantity. It can be noted that the B20 + 2.5%@PI15% fuel demonstrates slightly lower brake energy consumption when compared to PI30% and PI15%–EGR10% at maximum power output. Notably, the BSEC is increased by 5.8% when the pilot inject rate has been increased from 15% to 30% for B20 fuel operation. The same trend has been noted with 10% EGR operation as well. This is a result of increment in the time taken for complete combustion due to EGR prompts a increases the in brake specific energy consumption. This expansion in fuel request is because of the decrease of external air used during the combustion and subsequently a prerequisite for more prominent fuel amount to keep up the power production [20].

Fig. 4. Variations of in-cylinder pressure with respect to crank angle at (a) 50% load and (b) 100% load.

4.2.1. In-cylinder pressure It is the inherent pressure developed inside the combustion cylinder during the engine operation, helps to quantify the timing and quality of the way it combusts inside the cylinder. The rate at which pressure rises determines the smooth operation, transfer of all the pressure forces onto the crankshaft and is obtained by high speed data acquisition system. Fig. 4(a) and (b) represents the comparison of In-cylinder pressure vs crank angle at 50% and 100% load respectively. It is to be noted that all the diesel and B20 blends followed a similar pattern in incylinder pressure with respect to crank angle at 50% and 100% loads. At full load condition peak values of in-cylinder pressure was found to be 79.57, 81.14, 82.84, 83.85, 79.52, 79.54, 82.12, 80.51 bar for diesel, B20, B20 + 2.5%@PI15%, B20 + 2.5%@PI30%, B20 + 2.5%@ PI15%–EGR10%, B20 + 5%@PI15%, B20 + 5%@PI30% and B20 + 5%@PI15%–EGR10% respectively. It is discernible that the peak value of In-cylinder pressure of TPO20 is marginally higher than diesel fuel at same pilot injection conditions of PI15%. Fig. 5 shows the peak pressure of all fuel samples with respect to brake power. This is due to the combined effect of lower viscosity of Turpentine oil which accelerates the air–fuel mixing process and therefore, higher incylinder pressure is achieved [21]. Moreover the cetane index of Turpentine oil is slightly lower than diesel fuel and therefore an increase in fuel accumulation inside the cylinder has resulted in higher incylinder pressure generation. An interesting trend was observed that on increasing

4.2. Combustion characteristics The potential of the engine combustion properties are greatly influenced by the varieties of qualities and factors inside the engine cylinder. Various combustion characters like incylinder pressure, heat release rate, cumulative heat release rate, mass fractions burned and mean gas temperature are discussed in this section. 6

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 5. Variation of peak pressure with respect to brake power.

the amount of pilot injection from 15% to 30%, the peak in-cylinder pressure increases for both the samples of 2.5% and 5% SC5D and highest peak in-cylinder pressure is shown by B20 + 2.5%@PI30%. The reason for this behaviour is an increase in pilot injection rate caused more fuel accumulation at same injection timing and therefore, higher incylinder pressure has been developed. Furthermore, the SC5D addition at 5% concentration with B20 fuel sample has not shown any significant improvement in combustion behaviour. Meanwhile it is also increased the fuel density and reduced the heating value drastically. Some previous studies suggest that In-cylinder pressure is strongly affected by the oxygen availability, which is related to the mixture formation in the combustion chamber. Therefore, EGR is introduced at 10% for two of the blends, but it shows reduction in In-cylinder pressure compared to results at 15% pilot injection. The reason behind this is that using EGR increases the rate of exhaust gas recirculation, reducing the fresh air intake, due to which oxygen concentration reduces resulting in reduction of brake thermal efficiency, which directly affects the In-cylinder pressure. Therefore, the impact on fresh air circulation for combustion process has not affected the heat development inside the cylinder.

Fig. 6. Variations for heat release rate vs crank angle at (a) 50% load and (b) 100% load.

the HRR of B20 + 2.5%@PI30% [23]. The blends having 5% SC5D shows lower HRR than 2.5% SC5D ones because high amount of cetane improver leads to the polymerization of fuel resulting in reduction of calorific value which finally results in lower heat release. Also as the EGR is introduced; HRR decreases gradually and the ignition delay was longer because oxygen concentration decreases which results in poor combustibility. Fig. 7(a) and (b) shows the variations of cumulative heat release rate vs crank angle at 50% and 100% loads respectively. Cumulative heat release rate is obtained by integration of individual HRR produced inside the combustion chamber over the crank angle as the piston moves through the cylinder. This helps in understanding the phenomenon of total heat release and absorption by the fuel injected at different crank angles to sustain combustion. Application of EGR to mitigate the emissions has a negative effect on the CHRR of the turpentine blends. This is explained by drop in in-cylinder temperature and oxygen availability upon EGR injection. A progressive trend was seen in CHRR curves when plotted against crank angle.

4.2.2. Heat release rate It is a decisive characteristic that indicates the efficiency of fuel combustion by substituting the first law of thermodynamics on the Incylinder Pressure. There are three distinguished phases of heat release i.e., pre-mixed combustion phase, mixed combustion phase and late combustion phase. HRR plays a key role in designing of CI engines since it directly affects the emission parameters. Comparison of heat release rate vs crank angle for standard diesel fuel and turpentine oil blends at 50% and 100% load is plotted in Fig. 6(a) and (b) respectively. It is clearly evident from both the graphs of HRR that all the turpentine blends and diesel fuel show analogous trend. At full load conditions for pure diesel, B20, B20 + 2.5%@PI15%, B20 + 2.5%@PI30%, B20 + 2.5%@PI15%–EGR10%, B20 + 5%@PI15%, B20 + 5%@PI30% and B20 + 5%@PI15%–EGR10%, peak heat release rate amount touched is 69.9, 68.61, 65.76, 85.1, 63.09, 61.54, 67.17, 60.01 J/deg crank angle respectively. At 50% load B20 shows highest HRR whereas at 100% load B20 + 2.5%@PI30% shows highest HRR value. This is because at part load condition effect of turpentine’s high calorific value and lower viscosity compared to conventional diesel fuel assist in fast burning which results in easier atomization and air–fuel mixing [22], giving complete combustion in short duration and hence increasing the HRR of B20 blend. Whereas at full load condition the cause dominating all other possible factors is the 30% pilot injection and passable amount of cetane enhancerwhich leads to the accumulation of large fuel quantity during the premixed combustion phase and hence increasing

4.2.3. Mass fraction burnt Mass fraction burnt is the ratio of CHRR to the net HRR in accordance with the crank angle inside the combustion chamber. Fig. 8 represents the variations of mass burnt fraction plotted against crank angle at (a) 50% load condition and 8. (b) 100% load condition. Mass burnt fraction is greatly influenced by in-cylinder gas pressure and heat release rate in combustion process. Despite the fact that, injection starting timing for diesel and B20 fuel is same as 23°BTDC but at full 7

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 7. Variations for cumulative heat release rate vs crank angle at (a) 50% load and (b) 100% load.

Fig. 8. Comparison of mass fraction burnt against crank angle at (a) 50% load and (b) 100% load.

load MFB of both diesel and B20 shows different trend with respect to crank angle. It is clear that B20 shows less mass fraction burnt than diesel till 7° BTDC. The effect of addition of cetane improver of SC5D has very negligible effect on mass fraction burnt when compared to pilot injection rate variation. From the Fig. 8(b) it can be depicted that both the blends having 15% pilot injection rate shows less mass fraction burnt compared to blends with 30% pilot injection rate. Also a blend with 30% pilot injection seems to burn better than diesel fuel and this is due to the accumulation of more amount of fuel before the main injection process [23,24]. The enforcement of EGR generally results in decrease in mass fraction burnt due to the oxygen depletion upon nonreactive exhaust gas intake with air. Interestingly, the diesel engine operation with B20 + 2.5%@PI15%–EGR10% fuel and B20 + 5%@ PI15%–EGR10% fuels has not evident in reduction in mass fraction burning rate at 50% and 100% loads. This is probably due to the presence of SC5D cetane enhancer with B20 fuel which improves the autoignition quality of B20 blend and therefore the 10% EGR implementation could not affect the fuel burning rate. This is also due to the split up in fuel injection rate during combustion process which might played a dominant role at the time of combustion process.

increments. The deviation of mean gas temperature for pure diesel and all B20 blends is shown in Fig. 9(a) and (b). The pattern pursued by MGT is strangely like that of CHRR till 20° roughly. The cumulative heat release rate demonstrates consistent ascent in heat release rate, on other hand the mean gas temperature drops as on the grounds that almost all the fuel has been burnt and furthermore the way that incylinder pressure is falling as a result of the descending movement of the cylinder. As noted from the Fig. 9(b) an easy observation can be made that is B20 shows low MGT than diesel during the start of combustion and till 20° crank angle and this is because of superior latent heat of vaporization of turpentine and low flame temperature than conventional diesel fuel. A fascinating perception can be seen that after a certain level of crank angle all the turpentine blends indicates increment in MGT, because of the high calorific value of turpentine which aids total combustion at higher loads. On introducing cetane improver to the B20, it was found that blends having 2.5% SC5D shows lower MGT compared to the blends having 5% SC5D. The primary reason for this behaviour is the higher viscosity of Turpentine oil could worsen the fuel. The expansion of pilot injection from 15% to 30% prompts generous enhancement in MGT as the underlying consumption of more fuel elevates the mean gas temperature. Moreover, an introduction of EGR at 10% rate with B20 fuel blends at all concentrations reduces the mean gas temperature and this is due to the reduction in fresh air circulation inside the cylinder which has leads to incomplete combustion.

4.2.4. Mean gas temperature It is a temperature derivative of all other combustion parameters that helps in understanding the correlated relationship between the performance and emission characteristics. MGT is an impression of the CHRR, as the fuel infused combusts the mean gas temperature 8

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 10. Variations of unburnt hydrocarbon emissions at various brake power.

fuel, which causes it to mix properly with air and hence produce a lean mixture, which burns more efficiently as opposed to pure diesel. For further improvement in the output, cetane enhancer SC5D is added to the blends, it reduces the viscosity and helps in better atomisation of the fuel due to fine droplet size [26], which improves the homogeneity of the air- fuel mixture and as it is clearly visible in the graph, for the samples with SC5D added to them, HC emissions are lower. Among the samples with cetane enhancer, the ones with lower concentration of it, that is 2.5% of SC5D showed marginally higher emissions, which is because of formation of rich in fuel zones within the chamber. The improper mixing of fuels with air, because of its high specific gravity leads to its deposition in certain areas. Subjecting the blends to pilot injection has also yielded positive results, as it is evident from the graph. Also increasing the pilot injection percentage tends to reduce the HC emissions. For samples of B20, B20 + 2.5%@PI15% and B20 + 2.5%@PI30% HC emissions was found out to be 0.1077 g/kWh, 0.1058 g/kWh, 0.1050 g/kWh respectively at full load conditions. From this data, inference made is that introducing 15% PI has shown marginal reduction in emissions, simultaneously increasing the amount of pilot injection from 15% to 30% showed similar variations. Explanation for the cause is the presence of more suitable conditions for self-ignition, which are provided by burning some percentage of fuel within the chamber before main injection; this increases the pressure and temperature within the cylinder thereby yielding better results. Moreover, the samples that have undergone EGR, like, B20 + 2.5%@ PI15%–EGR10% and B20 + 5%@PI15%–EGR10% show least HC emissions, 0.089 g/kWh and 0.088 g/kWh respectively. Though using EGR reduces the fresh air intake of the engine but higher temperature of the charge coupled with better diffusion of fuel particles in air have an overall positive affect over the combustion.

Fig. 9. Comparison of mean gas temperature vs crank angle at (a) 50% load and (b) 100% load.

4.3. Emission characteristics The emission attributes of the engine spotlight on the emission gas quality and approves the nature of the burning of the fuel and power generation by estimating the total and fragmented combustion items just as other results. The components that are examined are: Unburnt HC, CO, Oxides of nitrogen and Smoke. It is additionally basic to take note of that the discharge qualities of the engine must fall under the BS IV standards to which particulars the engine was manufactured. Varieties from the standard are credited to the way that the engine has been altered to a CRDI setup with higher injection pressures without changing its injection timing.

4.3.2. Carbon monoxide CO emissions inform us about the extent of combustion happening inside the chamber, if it is complete, less will be the emissions and if it is incomplete, the inverse is true. The major reasons behind excessive CO emissions are, deficiency of O2 in the air–fuel mixture, inadequate blending of fuel particles in air, varying injection strategies. As observed from Fig. 11 that, at higher loads emissions are higher for pure diesel as opposed to the blends with turpentine oil present in them, which is due to the higher amounts of inborn oxygen in biofuels. On the contrary, similar trend did not follow up at lower loads, which is because; at lower loads the temperature and pressure conditions are not suitable enough to utilize fully turpentine oil’s added oxygen. Another interesting observation is that, for the samples with 2.5% SC5D, increasing the percentage of pilot injection from 15% to 30% decreases the CO emissions at all loads while the case is entirely contrasting with

4.3.1. Unburnt Hydrocarbons Unburnt hydrocarbon (UBHC) emissions are the product of improper burning of fuel; they are produced because of the hydrogen and carbon content of the fuel. As it is clearly observable from the Fig. 10, at lower loads, HC emissions are quite higher when compared at higher loading conditions; this is mainly because at higher loads, temperature and pressure within the chamber is higher, since the fuel burns more efficiently. In addition to that, diesel is showing much higher HC emissions as compared to its other counterparts, which is due to the presence of turpentine oil within the blends, its high oxygen content, and lesser carbon to hydrogen ratio leads to better combustion of blend [25]. Another reason that could provide an explanation for this trend is the lower viscosity of other blends, it leads to proper atomisation of the 9

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 14. Variations of smoke emissions at various brake power. Fig. 11. Variations of carbon monoxide emissions at various brake power.

thereby reducing the efficiency of ignition and if in such state additional fuel is injected through pilot injection it only makes the matter worse. Though at full load condition, fresh air intake increases therefore the engine output is improved somewhat, which is justified by the drop of emissions by 27.56% from sample B20 + 2.5%@PI15% to B20 + 2.5%@PI30%. At lower loads, using EGR recirculates the unused oxygen within the cylinder, which leads to better burning of fuel and in turn lesser emissions [28]. On the other hand, at full load conditions, exhaust gas mostly constitutes of gaseous products like NOx, CO, CO2, smoke and lesser oxygen, which makes the air–fuel mixture lean thereby reducing the quality of combustion. For the sample with 2.5% SC5D using 10% EGR along with 15% pilot injection has led to decreased emissions by 9.03% as compared to the case without EGR. On the other hand, for the sample with 5% SC5D, under similar injection conditions 19.9% rise was observed in emissions from sample B20 + 5%@PI30% to B20 + 5%@PI30%. + EGR10%. Because of the lower viscosity of 5% SC5D sample, it leads to better atomisation of fuel, but because of its higher density it doesn’t diffuse properly with air which causes poor combustion. 4.3.3. Nitrogen oxides Oxides of nitrogen (NOx) emissions are mostly formed due to excessive combustion temperature, presence of high amount of oxygen. The oxides of nitrogen mostly consist of two compositions- nitrogen monoxide (NO) and nitrogen dioxide (NO2) [29]. The trend for NOx emissions for different fuel samples is shown in Fig. 12. Various preinjection and post injection strategies have been developed to control the tail pipe emissions [30]. The predominantly used pre-injection technique is EGR, which facilitates NOx reduction. The production of NOx depends mainly upon in-cylinder temperature, pressure conditions and availability of oxygen within the air–fuel mixture. This is the reason why the emissions show a sudden spike in case of blends with biodiesel, since biodiesel have that extra oxygen content [13]. Adding cetane enhancer also contributes towards the growth in NOx emissions since it increases the cetane number of the blend and helps in better burning of the fuel and also reducing the ignition delay. All these combined factors are responsible for the trend shown by the blends with SC5D. As noted from the Fig. 12, the NOx emission formation has been followed a similar trend for diesel and B20 fuels at all conditions. The diesel engine operation with B20 fuel at PI15% and PI30% rate has increased the NOx emission compared to diesel fuel. This is because of the reduction in ignition delay period due to split injection and this has enhances the combustion process and therefore higher NOx emission. Furthermore, the addition of cetane improver at 2.5% and 5% concentrations has also increased the NOx emissions significantly. Using 10% EGR has shown positive results and has brought down the NOx emissions to a very comparable value to diesel at all loads. At full load condition the sample

Fig. 12. Variations of oxides of nitrogen emission at various brake power.

Fig. 13. Variations of carbon di-oxide emissions at various brake power.

samples that have 5% SC5D, with an exception at 100% load. The trend for the former case is because of increased pilot injection percentage that leads to better in-cylinder conditions. However, in latter case the increased density of blends overshadows that effect [27]. Since the density is higher, proper mixing of fuel with air does not take place 10

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Table 5 ANOVA and its fit statistic for the engine emission study. Response

Sources of variation

Sum of square

df

Mean square

%Influence

F-value

p-value

Fit statistic

HC

Model A-BMEP B-Fuel AB Pure Error Cor Total

2305.9857 1498.6145 257.6137 516.4390 0.0159 2306.0016

31 3 7 21 5 36

74.3866 499.5382 36.8020 24.5923 0.0032

100.00 64.99 11.17 22.40 0.00

23344.6567 156769.3886 11549.5089 7717.7784

< 0.0001 Significant < 0.0001 < 0.0001 < 0.0001

Mean = Std. Dev. or RMSE = R2 = Adjusted R2 =

15.90 0.0564 1.0000 1.0000

CO

Model A-BMEP B-Fuel AB Pure Error Cor Total

0.5027 0.4237 0.0589 0.0401 0.0002 0.5030

31 3 7 21 5 36

0.0162 0.1412 0.0084 0.0019 0.0000

99.95 84.24 11.71 7.96 0.05

336.4222 2929.9622 174.4791 39.5661

< 0.0001 Significant < 0.0001 < 0.0001 0.00034

Mean = Std. Dev. or RMSE = R2 = Adjusted R2 =

0.2233 0.0069 0.9995 0.9965

NOx

Model A-BMEP B-Fuel AB Pure Error Cor Total

1230.2591 366.1511 497.9316 300.2196 0.0330 1230.2921

31 3 7 21 5 36

39.6858 122.0504 71.1331 14.2962 0.0066

100.00 29.76 40.47 24.40 0.00

6022.0216 18520.2357 10793.9162 2169.3375

< 0.0001 Significant < 0.0001 < 0.0001 < 0.0001

Mean = Std. Dev. or RMSE = R2 = Adjusted R2 =

28.77 0.0812 1.0000 0.9998

Smoke

Model A-BMEP B-Fuel AB Pure Error Cor Total

2087.5511 1604.4901 276.9415 63.9323 0.1080 2087.6591

31 3 7 21 5 36

67.3404 534.8300 39.5631 3.0444 0.0216

99.99 76.86 13.27 3.06 0.01

3117.6092 24760.6491 1831.6235 140.9443

< 0.0001 Significant < 0.0001 < 0.0001 < 0.0001

Mean = Std. Dev. or RMSE = R2 = Adjusted R2 =

41.89 0.1470 0.9999 0.9996

CO2

Model A-BMEP B-Fuel Residual Lack of Fit Pure Error Cor Total

126.9580 122.7818 1.0557 0.6793 0.6171 0.0622 127.6373

10 3 7 26 21 5 36

12.6958 40.9273 0.1508 0.0261 0.0294 0.01243

99.47 96.20 0.83 0.53 0.48 0.05

485.9305 1566.4870 5.7724

< 0.0001 Significant < 0.0001 0.00041

Mean =

6.38

2.3643

0.1725 not significant

Std. Dev. or RMSE = R2 = Adjusted R2 =

0.1616 0.9947 0.9926

mixture [31]. At higher loads increasing the concentration of SC5D from 2.5% to 5% leads to increment in amount of CO2 emission because due to lower viscosity better atomisation of the fuel occurs which leads to more efficient burning of fuel [32]. Another useful observation that can be made out from the graph is that increasing the amount of pilot injection from 15% to 30%, leads to reduction in emissions across all loads for the blends with 2.5% cetane enhancer. This is because at 30% pilot injection the temperature of the chamber gets too high and some of the oxygen gets used up in oxidation of nitrogen into NOx emissions. Subsequently introducing 10% EGR instigates escalation in CO2 emissions since some of the CO that gets recirculated into the chamber gets converted into the CO2 thereby increasing the emissions.

B20 + 5%@PI15% + EGR10% has the value 15.62 g/kWh, which is just 4% more than that of diesel’s 14.99 g/Kwh. By recirculating the exhaust gas within the chamber the amount of fresh oxygen intake is reduced which leads to poor oxidation of nitrogen compounds thereby reducing NOx emissions. 4.3.4. Carbon dioxide It is a secondary product of any complete combustion reaction of the carbon-based fuel. Carbon dioxide emissions are one of major tail pipe emission norms that the government has been working to curb since they have been contributing the greenhouse effect. Carbon dioxide emissions occur due to high in-cylinder temperature and oxygen availability, which contributes towards CO to CO2 oxidation and complete combustion of the air–fuel mixture. Fig. 13 represents the variation of carbon dioxide with respect to BP for all test samples. General trend suggests that with increase in brake power, there is a linear increase in the carbon dioxide emissions and reaches maximum at full load conditions. High quantity of fuel injected to keep up with the higher rpm of the engine results in higher in-cylinder temperature thus contributing to spontaneous combustion of the air–fuel mixture. Among all the test samples, all B20 blends emit lower CO2 than diesel fuel under all brake powers. Diesel emits only 4.05%, 7.22% of CO2 at brake power of 1.07 kW and 3.13 kW respectively, while the B20 blends emit CO2 values greater than 3.98% and 7.12% for 1.07 kW and 3.13 kW respectively. The lower carbon to hydrogen ratio for turpentine oil and increased volumetric efficiency can explain this trend. A general trend that can be observed from the Fig is that, at lower loads addition of cetane enhancer has led to decrease in CO2, since the oxygen content of the blend becomes higher also the calorific value is increased. While at full load conditions these blends shows higher values in comparison to B20 blend, but still lower than diesel. The value has increased in comparison to B20 because higher density leads to improper diffusion of fuel throughout the air therefore reducing the homogeneity of the

4.3.5. Smoke Smoke is mixture of solid and liquid particulate matter aggregated with soot, Sulphur oxide and aromatic compounds in the fuel. To measure the smoke particles present in visible exhaust gas optical meters are used. Incomplete combustion of hydrocarbon and carbon particles in the test fuel or blends encourage the formation of smoke. From Fig. 14 a general trend that is clearly observable is, increase in smoke emissions with increase in engine load. This is because as the load increases, the amount of fuel and air drawn in by the engine also increases, which leads to fuel accumulation. Using turpentine oil leads to decrement in smoke emissions since the availability of oxygen within the blends increases, which leads to improved combustion. Adding cetane enhancer in small proportions i.e. 2.5% SC5D helps in decreasing the smoke emissions. On the other hand, the samples with 5% SC5D has shown higher smoke emissions as compared to 2.5% SC5D samples but still lower than B20. The Cetane enhancer increases the density of the blends, which leads to poor mixing with air. While at higher concentration of cetane enhancer, the calorific value of the blend is lower which increases the production of smoke. In case of samples with 2.5% SC5D, subjection to 15% pilot injection show results 11

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 15. Factor effects and respective interaction effects plots for engine emission analysis.

12

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

(a). Half-Normal % Probability Plots

(b). Interaction Plots

Fig. 15. (continued)

performed for all the emission characteristics. During this analysis, the three sets readings of CO, HC, CO2, NOx and smoke emissions. An Ioptimal design type of 2 factor factorial design model was developed for the response surface study of BMEP and fuel type on the engine emission. With three levels of BMEP (1.07, 2.1, 3.13, 4.22 bar) was planned on eight different operating conditions (Diesel, B20, B20 + 2.5%@ PI15%, B20 + 2.5%@PI30%, B20 + 2.5%@PI15%–EGR10%, B20 + 5%@PI15%, B20 + 5%@PI30%, and B20 + 5%@ PI15%–EGR10%) to analyze the engine emissions such as HC, CO, NOx, smoke and CO2. An I-optimal design with 37 numbers of experiments were developed using Design Expert 11 software. The analysis of variance (ANOVA) table for the output variables is presented in Table 5. The Root Mean Square (RSM) i.e., standard error deviation values (σHC = 0.0564; σCO = 0.0069; σNOx = 0.0812; σSmoke = 0.1470; σCO2 = 0.1616) and the multiple correlation coefficients (R2 and Adjusted R2) presented in ANOVA table proves the adequacy of experimental data. The p value < 0.0001 indicates the significant influence of respective input parameter on engine emission. The percent influence of BMEP on the engine emissions are obtained as 64.99% to HC, 84.24% to CO, 29.76% to NOx, 76.86% to smoke and 96.20% to CO2. Similarly, the influence of operating conditions was estimated as 11.17% to HC, 11.71% to CO, 40.47% to NOx, 13.27% to smoke and

comparable to B20. The samples B20 and B20 + 2.5%@15%PI have the emission values 49.1% and 52.8% respectively. This is because using pilot injection increases the pressure and temperature condition inside the combustion chamber and ignition delay is reduced which results in more efficient utilization of fuel and hence lesser smoke emissions. For both samples with 2.5% and 5% SC5D, increasing the amount of pilot injection from 15% to 30% shows significant increase in smoke emissions. A possible explanation for this could be that the due to lower fuel viscosity and higher density the consumption of the fuel reduces and fuel accumulation increases, hence at 30% pilot injection the mixture becomes too lean to burn properly thereby increasing smoke emissions. Interestingly, the 10% EGR addition at both cetane improver fractions with B20 has resulted in higher smoke emissions and this is the general trend in EGR technique. The addition of exhaust gas with fresh air inside the cylinder increases the CO2 concentration and this has leads to incomplete combustion. Furthermore, the latent heat vaporization of Turpentine oil is 285 kJ/kg and this is extremely higher than diesel fuel which may cause more cooling effect. The earlier discussion on NOx emissions has clearly evident in higher NOx emission reduction. 4.3.6. Statistical analysis In the present study, the statistical uncertainty analysis has been 13

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

Fig. 16. Three dimensional surface plot showing the engine performance as a function of engine load & operating condition using Design Expert 11.0.3.0.

Moreover, it is identified that CO2 emission has been caused only by BMEP. Fuel type is insignificant (only 0.83%) on CO2 emission. In contrast, NOx emission is primarily activated by the fuel type. Moreover, HC and NOx are influenced by the interaction between BMEP and fuel type. But this interaction is insignificant for CO, smoke and CO2

0.83% to CO2. Interaction between BMEP and fuel type also shows much significant influence 22.40% to HC, 7.96% to CO, 24.40% to NOx, 3.06% to smoke and 0.48% to CO2. It can also be verified through the half-normal % probability plots (Fig. 15(a)). The engine load shows much influence on engine emissions of HC, CO, smoke and CO2. 14

Fuel xxx (xxxx) xxxx Present Study

[16]

[35]

4.3.7. Comparative analysis of cetane improvers with various biofuels A comparative analysis has been carried out on the effect of various cetane improvers with diesel and biofuels at different concentrations and the results are compared with present research work in Table 6. All the investigations have shown that the addition of cetane improver like EHN improved the emission and performance behaviours on par with diesel fuel in all forms for diesel engine. Fewer reports revealed that the CO and HC emission are marginally higher during cetane improver addition. However, in the present study, remarkable improved has been noticed in these emissions except NOx emission. Moreover, the 2.5% addition of SC5D seems to be an optimum concentration for the effective utilization in diesel engine.

↓: CO, smoke ↑: NOx

↓: NOx, Smoke ↑: HC, CO

↓: Smoke, NOx ↑: HC, CO

↑: HC, CO ↓: NOx, smoke

brake power. • Less density, lower viscosity, and lower energy • Lower content of blend improved in cetane number • 11% • complete combustion, higher power, lower NOx lower combustion performance • Slightly seems to be an optimum for better • 2.5% performance

[34]

[33]

combustion duration • Longer higher load, the cetane improver added diesel• Atethanol performance on par with diesel fuel Cetane number from 45.5 to 63.5 • Shorten ignitionhasdelayincreased and prolonged combustion • duration

↓: BSFC, ↑: BTE, BP

↑: BTE ↓: BSFC

10% n-Butnaol + 80% Diesel + 10% Biodiesel

80% Diesel + 20% Turpentine oil

In the present study the SC5D cetane improver has been doped with B20 biofuel at 2.5% and 5% concentrations. It has been noted that after doping 5% of cetane enhancer, the density of fuel has increased significantly and therefore, only 5% SC5D has been added with B20 fuel. During the experimental work, the NOx emission has been continuously monitored for PI15% and 30% rate at all the biofuel samples. It can be noted that 15% pilot injection of B20 fuel sample has increased the NOx emission at 2.5% and 5% of SC5D cetane enhancer addition. Therefore 10% EGR has been used at higher NOx emission conditions. The CRDI diesel engine was running smoothly with all biofuel samples. The following conclusions are drawn from the experimental works; The BTE of B20 fuel is found to be higher compared to diesel fuel. Furthermore, the addition of SC5D cetane improver has shown further improvement of BTE at all concentrations due to increase in density and reduction in net heating value. Moreover, the 10% EGR at PI15% has resulted in lower BTE. The brake specific energy consumption of all B20 fuel samples with cetane enhancer at 2.5% and 5% are lower than diesel and pure B20 fuel samples. On the other hand the 10% EGR implementation has resulted in slight reduction in BSEC value. The combustion characteristics are greatly dominated by the pilot injection variation and SC5D addition. Even though, the fuel density is greatly affected by cetane improver addition, the incylinder pressure, heat release rate and cumulative heat release rate are slightly lower than diesel fuel. The lower cetane index and higher latent heat of vaporization of Turpentine oil played a dominant role in combustion process initiation and maximum heat release rate development. An increase in pilot injection rate and 10% EGR addition for B20 with SC5D cetane improver have shown significant reduction in HC emissions under all loading conditions compared to diesel fuel. The reasons for this behaviour are the presence of cetane improver and low viscosity of Turpentine oil which have resulted in complete mixing with air and reduced the HC emission formation. The carbon monoxide formation is significantly lower for B20 fuel with 2.5% SC5D under 15% and 30% pilot injection rate. However, the CO emission is increased drastically for 5% SC5D addition and this is due to an increase in fuel density. Furthermore, the latent heat of Turpentine oil along with 10% EGR addition might played a

2-Ethylhexyl nitrate (EHN) 500, 1000 and 2000 ppm

Ethyl hexyl nitrate 1000 and 2000 ppm

SC5D 2.5%, 5%

Land Rover Multi cylinder, 4S, WS, CI, DI, CR19.5:1, RP: 82 kW, RS: 3800 rpm

Yanmar, Single cylinder, 4S, CI, CR-17.7:1, FIP: 200 bar, RP: 7.7 kW RS: 2400 rpm

Single cylinder, 4S, CI RP: 3.5 kW RS: 1500 rpm

Diesel

↑: BTE ↓: BSFC 70% Diesel 20% hazelnut oil + 10% n-Butanol or 10% Pentanol

2-Ethylhexyl nitrate, cyclohexyl nitrate, 2methoxyethyl ether 0, 0.3%, 3% (wt.) Single cylinder, 4S, WC, CI, DI, CR-19:1, RP: 5.7 kW, RS: 3000 rpm

Diesel

↑: BTE 10% Methanol + 90% Biodiesel Diesel

Cetane Improver 0, 0.2%, 0.4% Four cylinder, 4S, WC, CI, DI, CR-18.5:1, RP: 58.5 kW, RS: 3400 rpm

Diesel

↑: BSFC ↑: Power, BTE 15% Methanol + 85% Diesel Diesel

↓: HC ↓: NOx, Smoke

Performance Reference fuel Cetane Improver Engine

Table 6 Comprehensive analysis of various cetane improvers with biofuels.

emissions. The effect of interaction is depicted in Fig. 15(b). The effect of individual combination of levels of operating condition and BMEP on each engine emission is illustrated using the tree dimensional surface plats as shown in Fig. 16. The complex phenomenon of identifying the optimal engine load setting and best fuel type to minimize the engine emission was achieved by the desirability analysis. With 0.635 desirability index, 2.1 bar of BMEP and the fuel type of B20 + 5%@ PI15%–EGR10% are identified as optimal input parameters to reduce the engine emissions range to 15.54 g/kWh of HC and 0.188 g/kWh of CO, 26.85 g/kWh of NOx, 36.2% of smoke and 5.43% of CO2.

5. Conclusion

Blend

Emission

Technical Finding

Reference

A.K. Jeevanantham, et al.

15

Fuel xxx (xxxx) xxxx

A.K. Jeevanantham, et al.

vital role in CO emission. The combined effect of SC5D cetane improver at both fractions with 15% pilot injection rate showed higher NOx emission and the same trend has not been evident in PI30%. Moreover, the 10% EGR addition for both the fuel samples has resulted in significant NOx reduction. The smoke emissions of all biofuel samples are lower than diesel fuel at all pilot injection rates. However, the PI30% has produced more smoke emission when compared to PI15% at 2.5% and 5% fraction of SC5D with B20 fuel.

[12] [13]

[14]

[15] [16]

Therefore from the all the above results and observations it is clear that turpentine oil holds a good future in replacing diesel fuel at partial level. The usage of SC5D with Turpentine oil -diesel blend could be with lower fraction upto 2.5% and beyond that the fuel density become significantly higher and this can cause many issues like fine atomization and other combustion related issues. Moreover the chemical kinetics of SC5D with diesel and other biofuels need to be studied further. Lot more research works need to be done in various diesel engine under different operating conditions as well before adapting this Turpentine oil- SC5D cetane enhancer for regular applications.

[17]

[18] [19]

[20]

[21]

Funding [22]

No funding was received for this work. Declaration of Competing Interest

[23]

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.

[24]

[25]

References [26]

[1] Paulauskiene T, Bucas M, Laukinaite A. Alternative fuels for marine applications: biomethanol-biodiesel-diesel blends. Fuel 2019;248:161–7. [2] Raman LA, Deepanraj B, Rajakumar S, Sivasubramanian V. Experimental investigation on performance, combustion and emission analysis of a direct injection diesel engine fuelled with rapeseed oil biodiesel. Fuel 2019;246:69–74. [3] Bueno AV, Pereira MP, de Oliveira Pontes JV, de Luna FM, Cavalcante Jr CL. Performance and emissions characteristics of castor oil biodiesel fuel blends. Appl Therm Eng 2017;125:559–66. [4] Mohr A, Raman S. Lessons from first generation biofuels and implications for the sustainability appraisal of second generation biofuels. Energy Policy 2013;63:114–22. [5] Devarajan Y, Mahalingam A, Munuswamy DB, Nagappan B. Emission and combustion profile study of unmodified research engine propelled with neat biofuels. Environ Sci Pollut Res 2018;25(20):19643–56. [6] Naik SN, Goud VV, Rout PK, Dalai AK. Production of first and second generation biofuels: a comprehensive review. Renew Sustain Energy Rev 2010;14(2):578–97. [7] Vallinayagam R, Vedharaj S, Yang WM, Roberts WL, Dibble RW. Feasibility of using less viscous and lower cetane (LVLC) fuels in a diesel engine: a review. Renew Sustain Energy Rev 2015;51:1166–90. [8] Ashok B, Nanthagopal K, Chaturvedi B, Sharma S, Raj RT. A comparative assessment on Common Rail Direct Injection (CRDI) engine characteristics using low viscous biofuel blends. Appl Therm Eng 2018;145:494–506. [9] Yumrutaş R, Alma MH, Özcan H, Kaşka Ö. Investigation of purified sulfate turpentine on engine performance and exhaust emission. Fuel 2008;87(2):252–9. [10] Charoo NA, Shamsher AA, Kohli K, Pillai K, Rahman Z. Improvement in bioavailability of transdermally applied flurbiprofen using tulsi (Ocimum sanctum) and turpentine oil. Colloids Surf, B 2008;65(2):300–7. [11] Anand BP, Saravanan CG, Srinivasan CA. Performance and exhaust emission of

[27]

[28]

[29] [30]

[31]

[32] [33]

[34]

[35]

16

turpentine oil powered direct injection diesel engine. Renewable Energy 2010;35(6):1179–84. Karthikeyan R, Mahalakshmi NV. Performance and emission characteristics of a turpentine–diesel dual fuel engine. Energy 2007;32(7):1202–9. 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. Karthikeyan R, Nallusamy N, Alagumoorthi N, Ilangovan V. Optimization of engine operating parameters for turpentine mixed diesel fueled DI diesel engine using Taguchi method. Mod Appl Sci 2010;4(12):182. Ghosh P. Predicting the effect of cetane improvers on diesel fuels. Energy Fuels 2008;22(2):1073–9. Imdadul HK, Masjuki HH, Kalam MA, Zulkifli NW, Kamruzzaman M, Shahin MM, et al. Evaluation of oxygenated n-butanol-biodiesel blends along with ethyl hexyl nitrate as cetane improver on diesel engine attributes. J Cleaner Prod 2017;141:928–39. Musthafa MM. Development of performance and emission characteristics on coated diesel engine fuelled by biodiesel with cetane number enhancing additive. Energy 2017;134:234–9. Karthickeyan V. Effect of cetane enhancer on Moringa oleifera biodiesel in a thermal coated direct injection diesel engine. Fuel 2019;235:538–50. Raj Kumar A, Janardhana Raju G, Hemachandra Reddy K. Performance and emission analysis of mamey sapote biodiesel with SC 5D polymer additive. Elixir Mech Eng 2016;94:40565–9. Agarwal D, Singh SK, Agarwal AK. Effect of Exhaust Gas Recirculation (EGR) on performance, emissions, deposits and durability of a constant speed compression ignition engine. Appl Energy 2011;88(8):2900–7. Nour M, Attia AM, Nada SA. Combustion, performance and emission analysis of diesel engine fuelled by higher alcohols (butanol, octanol and heptanol)/diesel blends. Energy Convers Manage 2019;185:313–29. Teoh YH, How HG, Masjuki HH, Nguyen HT, Kalam MA, Alabdulkarem A. Investigation on particulate emissions and combustion characteristics of a commonrail diesel engine fueled with Moringa oleifera biodiesel-diesel blends. Renewable Energy 2019;136:521–34. Ashok B, Nanthagopal K, Saravanan B, Somasundaram P, Jegadheesan C, Chaturvedi B, et al. A novel study on the effect lemon peel oil as a fuel in CRDI engine at various injection strategies. Energy Convers Manage 2018 Sep;15(172):517–28. Nabi MN, Rasul MG. Influence of second generation biodiesel on engine performance, emissions, energy and exergy parameters. Energy Convers Manage 2018;169:326–33. Stroke F. Corrosion and engine test analysis of neem (Azadirachta indica) oil blends in a single cylinder, four stroke, and air-cooled compression ignition engine. Am J Mech Eng. 2014;2(6):151–8. Ashok B, Raj RT, Nanthagopal K, Krishnan R, Subbarao R. Lemon peel oil–A novel renewable alternative energy source for diesel engine. Energy Convers Manage 2017;139:110–21. Sheykhi M, Chahartaghi M, Balakheli MM, Hashemian SM, Miri SM, Rafiee N. Performance investigation of a combined heat and power system with internal and external combustion engines. Energy Convers Manage 2019;185:291–303. Ashok B, Nanthagopal K, Perumal DA, Babu JM, Tiwari A, Sharma A. An investigation on CRDi engine characteristic using renewable orange-peel oil. Energy Convers Manage 2019;180:1026–38. Dimitriou P, Tsujimura T, Suzuki Y. Adopting biodiesel as an indirect way to reduce the NOx emission of a hydrogen fumigated dual-fuel engine. Fuel 2019;244:324–34. Uyumaz A. Combustion, performance and emission characteristics of a DI diesel engine fueled with mustard oil biodiesel fuel blends at different engine loads. Fuel 2018;212:256–67. Deep A, Sandhu SS, Chander S. Experimental investigations on castor biodiesel as an alternative fuel for single cylinder compression ignition engine. Environ Prog Sustainable Energy 2017;36(4):1139–50. Kumar S, Rosen MA. Cashew nut shell liquid as a fuel for compression ignition engines: a comprehensive review. Energy Fuels 2018;32(7):7237–44. Xing-cai L, Jian-Guang Y, Wu-Gao Z, Zhen H. Effect of cetane number improver on heat release rate and emissions of high speed diesel engine fueled with ethanol–diesel blend fuel. Fuel 2004;83(14–15):2013–20. Li R, Wang Z, Ni P, Zhao Y, Li M, Li L. Effects of cetane number improvers on the performance of diesel engine fuelled with methanol/biodiesel blend. Fuel 2014;128:180–7. Atmanli A. Effects of a cetane improver on fuel properties and engine characteristics of a diesel engine fueled with the blends of diesel, hazelnut oil and higher carbon alcohol. Fuel 2016;15(172):209–17.