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Effect of vegetable oil share on combustion characteristics and thermal efficiency of diesel engine fueled with different blends
Thermal Science and Engineering Progress 14 (2019) 100404
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Thermal Science and Engineering Progress journal homepage: www.elsevier.com/locate/tsep
Effect of vegetable oil share on combustion characteristics and thermal efficiency of diesel engine fueled with different blends
T
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Brahma Nand Agrawala, Shailendra Sinhab, Andrey V. Kuzminc, , Valeriya A. Pinchukd a
Department of Mechanical Engineering, Dr. APJ Abdul Kalam Technical University, Lucknow, India Department of Mechanical Engineering, Institute of Engineering & Technology, Lucknow, India c National Academy of Sciences in Ukraine, Kiev, Ukraine d National Metallurgical Academy of Ukraine, Dnipro, Ukraine b
A R T I C LE I N FO
A B S T R A C T
Keywords: Diesel ENGINE Combustion characteristics Thermal efficiency Linseed oil Pure diesel Fuel blend
Diesel engines are one of the most widespread internal combustion engines in the world. However, the requirements of the Environmental saving and decreasing in fossil fuels quality demand on searching the alternative fuel composition, which will be more environmentally friendly. Using different Biofuels allows decreasing the impact on the environment. There are a lot of researches devoted to the investigation of different plant oils as additives to diesel fuel. However, most of them are limited to standard engine parameters investigation. Nowhere was an attempt to evaluate the efficiency of the engine in terms of energy conversion. An experimental investigation has been carried out to analyze the combustion characteristics and thermal efficiency of a diesel engine at constant engine speed fuelled with diesel and its blends (10, 20, 30, 40, and 50%) with linseed oil. The methodology for the determination of the thermal efficiency of the thermodynamic cycle was developed. The results show the effect of the amount of linseed oil in the blends with pure diesel has non-monotonous behavior. The best combustion characteristics and energy conversion efficiency were observed with 20% of the linseed oil share. The worst combination is the blend of 30% linseed oil and of 70% pure diesel. The results mean that the addition of the linseed oil to the fuel mixture has an ambiguous influence on engine performance.
1. Introduction Transportation sector consumed a significant amount of energy resources. One of the main kinds of the internal combustion engine is a diesel engine. Diesel engines are powerful and reliable; this determines their widespread applications. However, there are some problems associated with the diesel engines use: fossil fuels usage and ecological issues are few of them. Extensive research has been undertaken to identify the alternate sources of fossil fuel. Several experiments have been done on non-edible oil for a substitute fuel of diesel. The vegetable oils can be used as an alternative fuel in a diesel engine. Those oils can be used in raw form or in the processed in the form of biofuel. Several kinds of literature are available which deal with the vegetable oils as a biofuel. It reduces exhaust emissions and improves thermal efficiency. Biodiesel is one of the substitutes of fossil fuel. It is produced mainly from edible oils [1]. However, some problems may encounter such as piston ring sticking, filter gumming, severe engine deposits, injector
choking, and high viscosity of vegetable oils. These types of problems can be minimized or eliminated by transesterification [2]. An experimental investigation did on ignition delay by using blends of n-pentane and diethyl ether with pure diesel. The results noticed that the diethyl ether reduces the ignition delay of diesel fuel effectively at lower temperatures [3]. An experimental investigation did on combustion characteristics, performance parameters, and emissions in a diesel engine by using mahua oil blends with diesel [4]. The effects of varying injection opening pressure were studied. An author analyzed the combustion characteristics of edible and non-edible oil in diesel engine and showed higher cylinder pressure turned by longer ignition delay [5]. The influence of properties of methyl ester biodiesel has been analyzed which is derived by cottonseed oil, ethanol, n-butanol blends with diesel. The combustion and exhaust emissions were studied of a heavyduty direct injection (HDDI) [6]. The characteristics of premixed combustion in a heated channel have been investigated by Demirbas [7] Maruta et al. [8] and Mo et al. [9] have investigated the recent
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Corresponding author. E-mail addresses: [email protected] (B.N. Agrawal), [email protected] (S. Sinha), [email protected] (A.V. Kuzmin), [email protected] (V.A. Pinchuk). https://doi.org/10.1016/j.tsep.2019.100404 Received 8 June 2019; Received in revised form 27 August 2019; Accepted 29 August 2019 2451-9049/ © 2019 Elsevier Ltd. All rights reserved.
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Fig. 1. Experimental set-up line diagram: 1 – variable compression ratio engine, 2 – eddy current dynamometer, 3 – flywheel, 4 – data acquisition device, 5 – computer, 6 – smoke meter, 7 – exhaust gas analyzer, 8 – calorimeter, 9 – air box, 10 – burette, 11 – fuel tank, 12 – control valve.
In the blended fuel operation, the mean gas temperature, the rate of pressure rise and net heat release rate are higher than those of pure diesel. The result reveals that K50D50 is the optimum blend among all blend without any modification of the engine [22]. It is also found that in most of the cases, the investigation of thermal efficiency of the engine while using the oil blends with diesel fuel has not been reported so far. At the same time, the thermal efficiency of the engine determines the perfection of its thermodynamic cycle, or in other words, it characterizes the level of energy conversion in the engine. In case of using different working fluids, the perfection of the thermodynamics cycle will vary. Thus, the determination of the thermal efficiency of internal combustion engines when operating on nonstandard fuels is important. In the literature, as discussed earlier several reports are available in which edible oils such as Jatropha oil, Neem oil, etc. have been considered as a blend, whereas the reports dealt with the Linseed oil as a blend with Diesel is limited in number. Therefore, the aim of this study has been set to access the suitability of linseed oil as a blend with diesel. In the present study, major characteristics were systematically investigated at compression ratio 18, when fueled with 10% linseed oil and 90% diesel (L10D90), 20% linseed oil and 80% diesel (L20D80), 30% linseed oil and 70% diesel (L30D70), 40% linseed oil and 60% diesel (L40D60), and 50% linseed oil and 50% diesel (L50D50) on volume bases. This study has been carried-out to find an optimum blend for combustion characteristics and thermal efficiency of the engine for linseed oil.
trends and progress of biofuel and the technique to reduce the emissions in internal combustion engine by using biofuel. The engine performance and exhaust emissions have been investigated by Altin et al. [10]. The results reveal that on the basis of performance viewpoint, both vegetable oils and their esters are promising alternatives as fuel for diesel engines. It is easy to make blended diesel with linseed oil while the transesterification process used to make biodiesel. In addition, the rate of linseed oil is comparable to the cost of pure diesel fuel. However, it is observed from the literature review that percentage variation of the blend of different vegetable oils with pure diesel fuel while investigating the combustion and performance characteristics has been limited up to 40% in many reports [11,12]. The biodiesels provide better combustion characteristics than diesel. Of all the tested biodiesel blends, rice bran oil biodiesel decreased CO and hydrocarbon emissions the most, albeit at the cost of increasing NOx emissions [13–15]. The blending of aluminium oxide nanoparticles in biodiesel blends produces the most promising results in engine performance and also reduces the harmful emission from engines [16,17]. The ignition delay of the brassica, cardoon and coffee biodiesel diesel fuel blends at 15% and 30% is lower than diesel fuel on average. The additional oxygen has decreased the CO and THC emissions. An author found that the maximum BTE (brake thermal efficiency) obtained for different biodiesel diesel blends fuels was lower than that of standard diesel fuel [18]. Biofuels produce less harmful emissions at idle conditions, which supports their usage to reduce exhaust emissions in urban areas [19]. An author conclude that the brake thermal efficiency and exhaust gas temperature of the coated engine were considerably enhanced while brake specific fuel consumption, CO, HC, and smoke emission were decreased compared to those of standard engine [20,21]. The blend K50D50 (50% share of karanja oil and 50% share of pure diesel) emits lowest HC emission among all blends and pure diesel irrespective of various loads. However, CO emissions are still comparable to pure diesel. The blend K50D50 shows higher peak cylinder pressure is about 2.21 bar than that of pure diesel at full load.
2. Materials and methods All the studies were carried out with the help of the physical experiment.
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2.4. Experimental errors:
Table 1 Engine specification.
It should be noted that all data collected by the data acquisition system used in this experimental study is subject to small errors. The errors due to the data acquisition systems used in this study are on the order of 0.02% for the 12-bit system and 0.001% for the 16-bit system and are considered negligibly small when compared to the other sources of error. The error in the measurements of the engine speed is ± 1 rpm. Thus, the uncertainty in the values of the engine speed is estimated to be in the range of ± 0.066% (1/1500*100). The error in the measurement of the fuel and other liquids flow rates may be estimated by considering the error in the electronic balances, which have 0.1 g resolutions. The timer used in the test has a resolution of 0.1 s. Hence, the uncertainties in the values of the flow rates are estimated to be in the range of 0.4–0.7%. The error in the measurements of temperatures during the tests may be estimated by considering the error in the type of thermocouples used. Such an error for type T is 2.2 °C or 0.75%, whichever is greater, and for type K, it is 2.2 °C or 0.75%. Thus, the uncertainty in the measurements of temperature is estimated to be in the range of 2–5%. It should be clearly noted that the estimated errors in the measurements of the basic and derived quantities do not significantly influence the overall uncertainty in the final results.
Engine specification Type Rated Power Compression Ratio CR Range Cylinder number Bore and Stroke Total cylinder volume Injector opening pressure Start of IT
DI, naturally aspirated, water cooled, four stroke, 3.5 kW @ 1500 rpm 15 13–18 1 87.5 mm × 110 mm 661 cm3 210 bar 23° CA BTDC
2.1. Experimental set-up In this study, diesel fuel and its blends with linseed oil were tested in a single-cylinder direct-injection (DI) diesel engine to investigate the combustion characteristics of the engine at constant engine speed. The schematic diagram of the engine is shown in Fig. 1 and the necessary details of the engine are given in Table 1. The engine connected to a computer. Engine performance analysis software which named as Engine-soft-LV was used. This software is widely used to evaluate test internal combustion engines. The crank angle sensor, piezo sensor, and temperature sensors are used for measuring crank angle, pressure and temperature respectively. Different loads were applied to the engine coupled with an eddy current type dynamometer.
3. Results and discussion 3.1. Combustion characteristics
2.2. Physico-chemical properties of linseed oil and pure diesel [23]
Properties
Unit
Linseed oil
Pure Diesel
Formula Density @40 °C Lower Calorific Value Viscosity @40 °C Flash Point Cloud Point Pour Point Water Content Ash Content Carbon Residue Cetane Number
Kg/m3 MJ/kg cm2/s °C °C °C % % %
C18HnO 889 38.30 4.22 140 0 −7 0.09 0.04 0.06 52
CnH1.5n 829 43.50 2.68 50 −16 −20 0.02 0.01 0.17 47
This section deals the analysis of the standard combustion characteristics of linseed oil blends and pure diesel at a constant speed. The data for analyzing were collected during the number series of the experimental procedures and collected with the Engine-soft-LV. The comparisons discussed below. 3.2. Cylinder pressure In a diesel engine, cylinder pressure influenced by the combustion because it describes the ability of the fuel to mix with air and then combustion will take place. The variation between the cylinder pressure and crank angle and cylinder volume of various linseed blends and pure diesel is shown in Fig. 2 and Fig. 3 respectively. It is clear from the experimental results that the maximum peak cylinder pressure has been observed for the blend L50D50. This is expected because, for the blend L50D50, the ratio of CP/CV is also maximum among all the blends considered in the present study. The detailed discussion on CP/CV is
2.3. Experimental procedure:
• First of all, prepare the blends of linseed oil as follows: take 10% •
• •
linseed oil and 90% diesel by volume (ml) and mixed properly, named as L10D90, take 20% linseed oil and 80% diesel by volume (ml) and mixed properly, named as L20D80, similarly prepare other blends L30D70, L40D60, and L50D50. To investigate the combustion characteristics of the engine, engine run forty-five minutes for becoming stable condition at a constant speed and fuelled with pure diesel. All sensors attached to the engine at a different location and collect data by the data acquisition device. At various loads conditions, all readings were taking, and report prepared by Engine-soft-LV and stored into the computer. Above step repeat for blends L20D80, L30D70, L40D60, and L50D50. Evaluated data were compared and analyzed with that of the combustion chamber using pure diesel as fuel.
From the observed and recorded values, the combustion characteristics while using diesel and different blended fuels were reported in the form of graphs.
Fig. 2. Cylinder pressure vs. crank angle of linseed oil blends and pure diesel. 3
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Fig. 3. Cylinder pressure vs. Cylinder volume of linseed oil blends and pure diesel.
Fig. 5. Mass fraction burned of linseed oil blends and pure diesel.
which is divided by the total energy is known as mass fraction burned. During a specific combustion cycle and at a specific crank angle, it can be expressed by the energy conversion. Fig. 5 illustrates that the value of MFB 50% to 100% for blend L50D50 is maximum compared to all linseed blends and pure diesel.
given in the subsequent section. The similar kind of results has also been reported by the Warkhade and Babu [23]. The accurate analysis of the results shown in Fig. 2 and Fig. 3 allows observing the regularity following. An increase in linseed oil contents in the mixture from 0% (pure diesel) to 30% (L30D70) leads to a decrease in the cylinder pressure. The further increase in linseed oil concentration from 30% to 50% causes an increase in the cylinder pressure. Thus, 30% of linseed oil in the blend with 70% of diesel is the worst combination. It is clearly visible in Fig. 4. This result significantly differs from [5] and confirms that detailed investigations should be carried out for the deep understanding of the processes which take place. Fig. 4 built only for crank angle equal to 10°. For other values, the graph may be different. We have repeated these investigations for a few times. The results are reproducible. For each experiment, the blend L30D70 shows lower cylinder pressure characteristics, while the blend L50D50 has higher results. We did not attempt to analyze this pattern in the present study. Detailed chemical and physical considerations must be taken into account to understand the result achieved. Here we discuss only the results related to energy and power parameters of the diesel engine.
3.2.2. Cumulative heat release The aggregate sum of instantaneous heat release rates is called the cumulative heat release. Fig. 6 illustrated that the trend of the curve has S shape for a part of a cycle of an engine. In the beginning, the rate of heat release reaching a peak value rapidly then again slow down. It is clear from Fig. 6 that the heat release rate of blend L50D50 is greater than all other blends of linseed oil and pure diesel also. It can be also observed that the dependence of the cumulative heat release from the linseed oil fraction looks similar to the dependence of cylinder pressure, i.e. blend L30D70 is the worst combination. 3.2.3. Mean gas temperature It is clear from Fig. 7 that highest mean gas temperature achieved at blend L50D50. Other blends of linseed oil were quite close to pure diesel in case of mean gas temperature. The experiment shows that a higher concentration of blends mean gas temperature increases because the blending ratio increases its ignition delay.
3.2.1. Mass fraction burned (MFB) The content of trapped charge of the cumulative heat release values
3.2.4. Rate of pressure rise The combustion process imposed a load which is known as the rate
Fig. 4. Variation of cylinder pressure with linseed oil fraction.
Fig. 6. Cumulative heat release of linseed oil blends and pure diesel. 4
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Fig. 7. Mean gas temperature of linseed oil blends and pure diesel. Fig. 9. Net heat release of linseed oil blends and pure diesel.
brief look at the Fig. 4 gives us a very important fact of the engine processing specifics. It has already been noted that in our research the blend of oil 30% and diesel 70% provides the minimum pressure value in the engine cylinder. It is obvious that a decrease in pressure in the cylinder leads to a drop in power of the engines. It also leads to a deterioration in the combustion efficiency and, as a result, worsens the energy conversion and increase in the number of pollutants. On the other hand, the efficiency of the entire thermodynamic cycle is a more important criterion for making the final conclusions. Therefore, we made an additional investigation of the efficiency of the thermodynamic cycle of the engine, which determines the perfection of the engine or efficiency of the energy conversion in it. We have developed the methodology for the determination of the thermodynamic cycle thermal efficiency. Fig. 10 presents the well-known diagram of the diesel thermodynamic cycle: On the basis of this scheme the maximum thermal efficiency of a diesel cycle is dependent on the compression ratio [24] shown in Eq. (1):
Fig. 8. Rate of the pressure rise of linseed oil blends and pure diesel.
of pressure rise. It determines the structural design of the engine. It is clear from Fig. 8 that the result of the rate of pressure rise is near to pure diesel at blend L50D50. However L40D60 blends have a higher rate of pressure rise than pure diesel and other blends.
ηth = 1 −
1 ⎡ αγ − 1 ⎤ r γ−1 ⎢ ⎣ γ (α − 1) ⎥ ⎦
where,
•η
th
3.2.5. Net heat release It is very much clear that from Fig. 9 the net heat release is higher at blend L50D50 among all blends of linseed oil and pure diesel. Maximum net heat release 31.6 J/deg. noticed at blend L50D50. However, the pattern of a graph of blends of linseed oil was quite the same as pure diesel. Net heat release depends upon the combustion phenomenon; better combustion gives maximum net heat release.
– thermal efficiency;
3.3. The thermal efficiency of the diesel engine thermodynamic cycle The analysis of the results above which were get with the standard procedure of the internal combustion engine testing shows that in general terms linseed oil can be mixed with pure diesel fuel and the blends of those fuels can be used for substitution of the pure diesel. This reduces the consumption of hydrocarbon fuels and improves the environmental friendliness of internal combustion engines through the use of renewable Biofuels. The conclusion above is related to any vegetable oil added to the pure diesel and was stated many times before this. Nevertheless, the
Fig. 10. Idealized diesel cycle. 5
(1)
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Fig. 11. PV-chart cycle of linseed oil blends and pure diesel.
Fig. 12. CP/CV of linseed oil blends and pure diesel.
• α – the cut off ratio V /V (ratio between the end and start volume for the heat addition); • r – the compression ratio V /V ; • γ– the ratio of specific heats C /C . 3
The ratio of the specific heats γ – the degree coefficient in the equation pVγ = const (see Fig. 10). Determination of the γ was performed by using Excel trend lines for each of the blends investigated. Dots in Fig. 11 corresponds to the calculated approximation with the power function in the form:
2
1
2
P
V
Thus, for the calculation of thermal efficiency of the thermodynamic cycle, we need to know the V1, V2, V3, and γ. All of these variables except γ can be found from the experimental data as shown in Fig. 11.
P = a + b·(V − c )γ
(2)
Here, a, b and c – are cycle-specific constants. a, and c are horizontal and vertical asymptotes correspondingly. They have a strong physical sense. a – is a lower value of the pressure in the cylinder during engine operation. c – is a minimal possible volume of the cylinder. It is obviously that c = 0. Constant b, as well as degree coefficient γ, were calculated as the
• V – the cylinder volume when the compression stage starts and expanding stage finishes; • V – the volume where the fuel ignition occurs; • V – the volume where fuel-burning stops, can be determined at the 1
2 3
point, where p3 = p2.
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vegetable oils. Those issues were observed because we use untreated oil for investigation. Therefore we did not present those results as they have no sense. The share in 50% of linseed oil seems to be an upper limit for using the untreated oil as an additive to pure diesel. However, the additional investigation should be made for the determination of the long-term use of it. At the same time, from the point of view of engine performance (Fig. 13) the share in 20% of the oil as an additive to the pure diesel is another maximum of the efficiency. Such a minor additive allows increase up to approximately 5% in the efficiency of the energy conversion of the engine. It is noteworthy that the results shown in Fig. 13 have been computed when the crank angle is 10°. It is known that the crank angle directly influences the ratio CP/CV [25], hence, it also has an influence on the thermal efficiency as well (as given in Eq. (1)). Therefore, the aforesaid results can be case-specific (for 10° crank angle) and need to be explored more for the concrete outcome.
Table 2 Average value of CP/CV. S. No.
Linseed oil share
Average value of CP/CV
1 2 3 4 5 6
0% 10% 20% 30% 40% 50%
1.227239 1.237919 1.245411 1.214813 1.232169 1.249032
trend coefficients In the idealized cycle, the γ for the compression stage (1–2) and the expansion stage (3–4) should be equal (Fig. 10). In the real cycle, they differ from each other. However, for the first approach, we can determine the values of γ for the compression stage and expanding stage separately and then take into account its simple average value. All three sets of data for the ratio of specific heats – compression stage, expansion stage and average are shown in Fig. 12. The average value of CP/CV is given in Table 2. In Fig. 13, the thermal efficiency of the diesel thermodynamic cycle has been plotted for various linseed oil share. The average values of specific heats CP/CV used in the calculation are given in Table 2 whereas the value of the cut-off ratio and compression ratio has been computed using experimental data shown in Fig. 11. The thermal efficiency has been computed using Eq. (1). Analyzing the results shows that the influence of the linseed oil share in blends on the engine efficiency is not monotony. It is clearly visible from Fig. 13 that increasing in linseed oil share from 0% (pure diesel) to 20% (L20D80) leads to increasing the engine efficiency. Then at the value of 30% linseed oil share, thermal efficiency falls lower than the efficiency of the pure diesel. For the following increase in the linseed oil share in blend up to 50% (L50D50) the engine efficiency increases again and becomes higher, than of Pure Diesel. In the range of blends investigated, the maximal and minimum thermal efficiency has been observed at the 50% linseed oil share (L50D50) and 30% linseed oil share (L30D70) respectively. It is worth noting that we have also tried to investigate the blends with more than 50% share of linseed oil and pure diesel, however, there were a few problems occur such as piston ring sticking, filter gumming, severe engine deposits, injector choking, by using vegetable oil in longterm use in diesel engines due to poor volatility, and high viscosity of
4. Conclusions The aim of this study was to investigate the effects of blends of linseed oil and pure diesel fuel on the combustion characteristics and thermal efficiency of a diesel engine. For this purpose, we have investigated blends of those fuels with the share of linseed oil from 0% to 50% with pure diesel by volume. The conclusions of the results obtained in this investigation are as follows:
• It • • •
has been shown in the research, that almost all combustion parameters are maximal at blend oil/diesel 50/50%. However, 50% of oil can affect negatively the engine’s long-term operation. We have also found that a blend of 30% of linseed oil and 70% of pure diesel is the worst mixture ratio from the point of view of the engine combustion parameters for the specific case considered in the present study. We have developed an effective procedure for the evaluation of the thermal efficiency of the internal combustion engine’s thermodynamic cycle based on the standard test equipment data of Enginesoft-LV. For the first time, the comparative analysis was performed for thermal efficiency of the thermodynamic cycle of the diesel engine operated with different blends of vegetable oils and pure diesel fuel. The results of the comparative analysis show that the thermal efficiency of some blends of pure diesel fuel and vegetable oil can be
Fig. 13. Thermal efficiency of linseed oil blends and pure diesel. 7
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higher than that of pure diesel.
• The results allow concluding that the addition of 20% of the linseed •
oil increases in the thermodynamic cycle of the investigated diesel engine up to 5%. This means improvement of the performance of the engine, i.e. most efficient energy conversion. The analysis of the engine’s thermal efficiency is very important and should be carried out for any fuel mixture during the investigation.
[12]
[13]
Declaration of Competing Interest
[14]
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.
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biodiesel operated di diesel engine on combustion performance, and emission characteristics, Int. J. Green Energy 10 (2013) 90–102, https://doi.org/10.1080/ 15435075.2011.651753. P. Muthaiyan, S. Gomathinayagam, Combustion characteristics of a diesel engine using propanol diesel fuel blends, Jo. Inst. Eng. (India): Series C 97 (2016) 323–329, https://doi.org/10.1007/s40032-016-0229-x. G. Dhamodaran, R. Krishnan, Y.K. Pochareddy, H.M. Pyarelal, H. Sivasubramanian, A.K. Ganeshram, A comparative study of combustion, emission, and performance characteristics of rice-bran-, neem-, and cottonseed-oil biodiesels with varying degree of unsaturation, Fuel 187 (2017) 296–305, https://doi.org/10.1016/j.fuel. 2016.09.062. E. Alptekin, Emission, injection and combustion characteristics of biodiesel and oxygenated fuel blends in a common rail diesel engine, Energy 119 (2017) 44–52, https://doi.org/10.1016/j.energy.2016.12.069. A.S. Silitonga, H.H. Masjuki, H.C. Ong, A.H. Sebayang, S. Dharma, F. Kusumo, J. Siswantoro, J. Milano, K. Daud, T.M.I. Mahlia, W.-H. Chen, B. Sugiyanto, Evaluation of the engine performance and exhaust emissions of biodiesel-bioethanol-diesel blends using kernel-based extreme learning machine, Energy 159 (2018) 1075–1087, https://doi.org/10.1016/j.energy.2018.06.202. M. Sivakumar, N. Shanmuga Sundaram, R. Ramesh Kumar, M.H. Syed Thasthagir, Effect of aluminium oxide nanoparticles blended pongamia methyl ester on performance, combustion and emission characteristics of diesel engine, Renew. Energy 116 (2018) 518–526, https://doi.org/10.1016/j.renene.2017.10.002. M.M. Musthafa, T.A. Kumar, T. Mohanraj, R. Chandramouli, A comparative study on performance, combustion and emission characteristics of diesel engine fuelled by biodiesel blends with and without an additive, Fuel 225 (2018) 343–348, https:// doi.org/10.1016/j.fuel.2018.03.147. F. Jaliliantabar, B. Ghobadian, A.P. Carlucci, G. Najafi, A. Ficarella, L. Strafella, A. Santino, S. De Domenico, Comparative evaluation of physical and chemical properties, emission and combustion characteristics of brassica, cardoon and coffee based biodiesels as fuel in a compression-ignition engine, Fuel 222 (2018) 156–174, https://doi.org/10.1016/j.fuel.2018.02.145. F. Soto, G. Marques, E. Torres-Jiménez, B. Vieira, A. Lacerda, O. Armas, F. GuerreroVillar, A comparative study of performance and regulated emissions in a mediumduty diesel engine fueled with sugarcane diesel-farnesane and sugarcane biodieselLS9, Energy 176 (2019) 392–409, https://doi.org/10.1016/j.energy.2019.04.011. U. Öztürk, H. Hazar, F. Yılmaz, Comparative performance and emission characteristics of peanut seed oil methyl ester (PSME) on a thermal isolated diesel engine, Energy 167 (2019) 260–268, https://doi.org/10.1016/j.energy.2018.10.198. M.A. Ghadikolaei, C.S. Cheung, K.-F. Yung, Study of combustion, performance and emissions of a diesel engine fueled with ternary fuel in blended and fumigation modes, Fuel 235 (2019) 288–300, https://doi.org/10.1016/j.fuel.2018.07.089. B.N. Argrawal, S. Shailendra, Influence of various blends of karanja oil with pure diesel on performance emission and combustion characteristics of diesel engine: an experimental investigation, Int. J. Recent Technol. Eng. 8 (2019) 1245–1250 https://www.ijrte.org/wp-content/uploads/papers/v8i1/A3171058119.pdf. G.S. Warkhade, A.V. Babu, Combustion characteristics of linseed (Linum usitatissimum) methyl ester fuelled biodiesel blends in variable compression ratio diesel engine, Aust. J. Mech. Eng. 17 (2019) 38–51, https://doi.org/10.1080/14484846. 2018.1525170. Applied Thermodynamics: For Engineering Technologists, European Journal of Engineering Education. 18 (1993) 313–315. doi:10.1080/03043799308923249. M.L. Wissink, D.A. Splitter, A.B. Dempsey, S.J. Curran, B.C. Kaul, J.P. Szybist, An assessment of thermodynamic merits for current and potential future engine operating strategies, Int. J. Engine Res. 18 (2017) 155–169, https://doi.org/10.1177/ 1468087416686698.
Contents lists available at ScienceDirect
Thermal Science and Engineering Progress journal homepage: www.elsevier.com/locate/tsep
Effect of vegetable oil share on combustion characteristics and thermal efficiency of diesel engine fueled with different blends
T
⁎
Brahma Nand Agrawala, Shailendra Sinhab, Andrey V. Kuzminc, , Valeriya A. Pinchukd a
Department of Mechanical Engineering, Dr. APJ Abdul Kalam Technical University, Lucknow, India Department of Mechanical Engineering, Institute of Engineering & Technology, Lucknow, India c National Academy of Sciences in Ukraine, Kiev, Ukraine d National Metallurgical Academy of Ukraine, Dnipro, Ukraine b
A R T I C LE I N FO
A B S T R A C T
Keywords: Diesel ENGINE Combustion characteristics Thermal efficiency Linseed oil Pure diesel Fuel blend
Diesel engines are one of the most widespread internal combustion engines in the world. However, the requirements of the Environmental saving and decreasing in fossil fuels quality demand on searching the alternative fuel composition, which will be more environmentally friendly. Using different Biofuels allows decreasing the impact on the environment. There are a lot of researches devoted to the investigation of different plant oils as additives to diesel fuel. However, most of them are limited to standard engine parameters investigation. Nowhere was an attempt to evaluate the efficiency of the engine in terms of energy conversion. An experimental investigation has been carried out to analyze the combustion characteristics and thermal efficiency of a diesel engine at constant engine speed fuelled with diesel and its blends (10, 20, 30, 40, and 50%) with linseed oil. The methodology for the determination of the thermal efficiency of the thermodynamic cycle was developed. The results show the effect of the amount of linseed oil in the blends with pure diesel has non-monotonous behavior. The best combustion characteristics and energy conversion efficiency were observed with 20% of the linseed oil share. The worst combination is the blend of 30% linseed oil and of 70% pure diesel. The results mean that the addition of the linseed oil to the fuel mixture has an ambiguous influence on engine performance.
1. Introduction Transportation sector consumed a significant amount of energy resources. One of the main kinds of the internal combustion engine is a diesel engine. Diesel engines are powerful and reliable; this determines their widespread applications. However, there are some problems associated with the diesel engines use: fossil fuels usage and ecological issues are few of them. Extensive research has been undertaken to identify the alternate sources of fossil fuel. Several experiments have been done on non-edible oil for a substitute fuel of diesel. The vegetable oils can be used as an alternative fuel in a diesel engine. Those oils can be used in raw form or in the processed in the form of biofuel. Several kinds of literature are available which deal with the vegetable oils as a biofuel. It reduces exhaust emissions and improves thermal efficiency. Biodiesel is one of the substitutes of fossil fuel. It is produced mainly from edible oils [1]. However, some problems may encounter such as piston ring sticking, filter gumming, severe engine deposits, injector
choking, and high viscosity of vegetable oils. These types of problems can be minimized or eliminated by transesterification [2]. An experimental investigation did on ignition delay by using blends of n-pentane and diethyl ether with pure diesel. The results noticed that the diethyl ether reduces the ignition delay of diesel fuel effectively at lower temperatures [3]. An experimental investigation did on combustion characteristics, performance parameters, and emissions in a diesel engine by using mahua oil blends with diesel [4]. The effects of varying injection opening pressure were studied. An author analyzed the combustion characteristics of edible and non-edible oil in diesel engine and showed higher cylinder pressure turned by longer ignition delay [5]. The influence of properties of methyl ester biodiesel has been analyzed which is derived by cottonseed oil, ethanol, n-butanol blends with diesel. The combustion and exhaust emissions were studied of a heavyduty direct injection (HDDI) [6]. The characteristics of premixed combustion in a heated channel have been investigated by Demirbas [7] Maruta et al. [8] and Mo et al. [9] have investigated the recent
⁎
Corresponding author. E-mail addresses: [email protected] (B.N. Agrawal), [email protected] (S. Sinha), [email protected] (A.V. Kuzmin), [email protected] (V.A. Pinchuk). https://doi.org/10.1016/j.tsep.2019.100404 Received 8 June 2019; Received in revised form 27 August 2019; Accepted 29 August 2019 2451-9049/ © 2019 Elsevier Ltd. All rights reserved.
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Fig. 1. Experimental set-up line diagram: 1 – variable compression ratio engine, 2 – eddy current dynamometer, 3 – flywheel, 4 – data acquisition device, 5 – computer, 6 – smoke meter, 7 – exhaust gas analyzer, 8 – calorimeter, 9 – air box, 10 – burette, 11 – fuel tank, 12 – control valve.
In the blended fuel operation, the mean gas temperature, the rate of pressure rise and net heat release rate are higher than those of pure diesel. The result reveals that K50D50 is the optimum blend among all blend without any modification of the engine [22]. It is also found that in most of the cases, the investigation of thermal efficiency of the engine while using the oil blends with diesel fuel has not been reported so far. At the same time, the thermal efficiency of the engine determines the perfection of its thermodynamic cycle, or in other words, it characterizes the level of energy conversion in the engine. In case of using different working fluids, the perfection of the thermodynamics cycle will vary. Thus, the determination of the thermal efficiency of internal combustion engines when operating on nonstandard fuels is important. In the literature, as discussed earlier several reports are available in which edible oils such as Jatropha oil, Neem oil, etc. have been considered as a blend, whereas the reports dealt with the Linseed oil as a blend with Diesel is limited in number. Therefore, the aim of this study has been set to access the suitability of linseed oil as a blend with diesel. In the present study, major characteristics were systematically investigated at compression ratio 18, when fueled with 10% linseed oil and 90% diesel (L10D90), 20% linseed oil and 80% diesel (L20D80), 30% linseed oil and 70% diesel (L30D70), 40% linseed oil and 60% diesel (L40D60), and 50% linseed oil and 50% diesel (L50D50) on volume bases. This study has been carried-out to find an optimum blend for combustion characteristics and thermal efficiency of the engine for linseed oil.
trends and progress of biofuel and the technique to reduce the emissions in internal combustion engine by using biofuel. The engine performance and exhaust emissions have been investigated by Altin et al. [10]. The results reveal that on the basis of performance viewpoint, both vegetable oils and their esters are promising alternatives as fuel for diesel engines. It is easy to make blended diesel with linseed oil while the transesterification process used to make biodiesel. In addition, the rate of linseed oil is comparable to the cost of pure diesel fuel. However, it is observed from the literature review that percentage variation of the blend of different vegetable oils with pure diesel fuel while investigating the combustion and performance characteristics has been limited up to 40% in many reports [11,12]. The biodiesels provide better combustion characteristics than diesel. Of all the tested biodiesel blends, rice bran oil biodiesel decreased CO and hydrocarbon emissions the most, albeit at the cost of increasing NOx emissions [13–15]. The blending of aluminium oxide nanoparticles in biodiesel blends produces the most promising results in engine performance and also reduces the harmful emission from engines [16,17]. The ignition delay of the brassica, cardoon and coffee biodiesel diesel fuel blends at 15% and 30% is lower than diesel fuel on average. The additional oxygen has decreased the CO and THC emissions. An author found that the maximum BTE (brake thermal efficiency) obtained for different biodiesel diesel blends fuels was lower than that of standard diesel fuel [18]. Biofuels produce less harmful emissions at idle conditions, which supports their usage to reduce exhaust emissions in urban areas [19]. An author conclude that the brake thermal efficiency and exhaust gas temperature of the coated engine were considerably enhanced while brake specific fuel consumption, CO, HC, and smoke emission were decreased compared to those of standard engine [20,21]. The blend K50D50 (50% share of karanja oil and 50% share of pure diesel) emits lowest HC emission among all blends and pure diesel irrespective of various loads. However, CO emissions are still comparable to pure diesel. The blend K50D50 shows higher peak cylinder pressure is about 2.21 bar than that of pure diesel at full load.
2. Materials and methods All the studies were carried out with the help of the physical experiment.
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2.4. Experimental errors:
Table 1 Engine specification.
It should be noted that all data collected by the data acquisition system used in this experimental study is subject to small errors. The errors due to the data acquisition systems used in this study are on the order of 0.02% for the 12-bit system and 0.001% for the 16-bit system and are considered negligibly small when compared to the other sources of error. The error in the measurements of the engine speed is ± 1 rpm. Thus, the uncertainty in the values of the engine speed is estimated to be in the range of ± 0.066% (1/1500*100). The error in the measurement of the fuel and other liquids flow rates may be estimated by considering the error in the electronic balances, which have 0.1 g resolutions. The timer used in the test has a resolution of 0.1 s. Hence, the uncertainties in the values of the flow rates are estimated to be in the range of 0.4–0.7%. The error in the measurements of temperatures during the tests may be estimated by considering the error in the type of thermocouples used. Such an error for type T is 2.2 °C or 0.75%, whichever is greater, and for type K, it is 2.2 °C or 0.75%. Thus, the uncertainty in the measurements of temperature is estimated to be in the range of 2–5%. It should be clearly noted that the estimated errors in the measurements of the basic and derived quantities do not significantly influence the overall uncertainty in the final results.
Engine specification Type Rated Power Compression Ratio CR Range Cylinder number Bore and Stroke Total cylinder volume Injector opening pressure Start of IT
DI, naturally aspirated, water cooled, four stroke, 3.5 kW @ 1500 rpm 15 13–18 1 87.5 mm × 110 mm 661 cm3 210 bar 23° CA BTDC
2.1. Experimental set-up In this study, diesel fuel and its blends with linseed oil were tested in a single-cylinder direct-injection (DI) diesel engine to investigate the combustion characteristics of the engine at constant engine speed. The schematic diagram of the engine is shown in Fig. 1 and the necessary details of the engine are given in Table 1. The engine connected to a computer. Engine performance analysis software which named as Engine-soft-LV was used. This software is widely used to evaluate test internal combustion engines. The crank angle sensor, piezo sensor, and temperature sensors are used for measuring crank angle, pressure and temperature respectively. Different loads were applied to the engine coupled with an eddy current type dynamometer.
3. Results and discussion 3.1. Combustion characteristics
2.2. Physico-chemical properties of linseed oil and pure diesel [23]
Properties
Unit
Linseed oil
Pure Diesel
Formula Density @40 °C Lower Calorific Value Viscosity @40 °C Flash Point Cloud Point Pour Point Water Content Ash Content Carbon Residue Cetane Number
Kg/m3 MJ/kg cm2/s °C °C °C % % %
C18HnO 889 38.30 4.22 140 0 −7 0.09 0.04 0.06 52
CnH1.5n 829 43.50 2.68 50 −16 −20 0.02 0.01 0.17 47
This section deals the analysis of the standard combustion characteristics of linseed oil blends and pure diesel at a constant speed. The data for analyzing were collected during the number series of the experimental procedures and collected with the Engine-soft-LV. The comparisons discussed below. 3.2. Cylinder pressure In a diesel engine, cylinder pressure influenced by the combustion because it describes the ability of the fuel to mix with air and then combustion will take place. The variation between the cylinder pressure and crank angle and cylinder volume of various linseed blends and pure diesel is shown in Fig. 2 and Fig. 3 respectively. It is clear from the experimental results that the maximum peak cylinder pressure has been observed for the blend L50D50. This is expected because, for the blend L50D50, the ratio of CP/CV is also maximum among all the blends considered in the present study. The detailed discussion on CP/CV is
2.3. Experimental procedure:
• First of all, prepare the blends of linseed oil as follows: take 10% •
• •
linseed oil and 90% diesel by volume (ml) and mixed properly, named as L10D90, take 20% linseed oil and 80% diesel by volume (ml) and mixed properly, named as L20D80, similarly prepare other blends L30D70, L40D60, and L50D50. To investigate the combustion characteristics of the engine, engine run forty-five minutes for becoming stable condition at a constant speed and fuelled with pure diesel. All sensors attached to the engine at a different location and collect data by the data acquisition device. At various loads conditions, all readings were taking, and report prepared by Engine-soft-LV and stored into the computer. Above step repeat for blends L20D80, L30D70, L40D60, and L50D50. Evaluated data were compared and analyzed with that of the combustion chamber using pure diesel as fuel.
From the observed and recorded values, the combustion characteristics while using diesel and different blended fuels were reported in the form of graphs.
Fig. 2. Cylinder pressure vs. crank angle of linseed oil blends and pure diesel. 3
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Fig. 3. Cylinder pressure vs. Cylinder volume of linseed oil blends and pure diesel.
Fig. 5. Mass fraction burned of linseed oil blends and pure diesel.
which is divided by the total energy is known as mass fraction burned. During a specific combustion cycle and at a specific crank angle, it can be expressed by the energy conversion. Fig. 5 illustrates that the value of MFB 50% to 100% for blend L50D50 is maximum compared to all linseed blends and pure diesel.
given in the subsequent section. The similar kind of results has also been reported by the Warkhade and Babu [23]. The accurate analysis of the results shown in Fig. 2 and Fig. 3 allows observing the regularity following. An increase in linseed oil contents in the mixture from 0% (pure diesel) to 30% (L30D70) leads to a decrease in the cylinder pressure. The further increase in linseed oil concentration from 30% to 50% causes an increase in the cylinder pressure. Thus, 30% of linseed oil in the blend with 70% of diesel is the worst combination. It is clearly visible in Fig. 4. This result significantly differs from [5] and confirms that detailed investigations should be carried out for the deep understanding of the processes which take place. Fig. 4 built only for crank angle equal to 10°. For other values, the graph may be different. We have repeated these investigations for a few times. The results are reproducible. For each experiment, the blend L30D70 shows lower cylinder pressure characteristics, while the blend L50D50 has higher results. We did not attempt to analyze this pattern in the present study. Detailed chemical and physical considerations must be taken into account to understand the result achieved. Here we discuss only the results related to energy and power parameters of the diesel engine.
3.2.2. Cumulative heat release The aggregate sum of instantaneous heat release rates is called the cumulative heat release. Fig. 6 illustrated that the trend of the curve has S shape for a part of a cycle of an engine. In the beginning, the rate of heat release reaching a peak value rapidly then again slow down. It is clear from Fig. 6 that the heat release rate of blend L50D50 is greater than all other blends of linseed oil and pure diesel also. It can be also observed that the dependence of the cumulative heat release from the linseed oil fraction looks similar to the dependence of cylinder pressure, i.e. blend L30D70 is the worst combination. 3.2.3. Mean gas temperature It is clear from Fig. 7 that highest mean gas temperature achieved at blend L50D50. Other blends of linseed oil were quite close to pure diesel in case of mean gas temperature. The experiment shows that a higher concentration of blends mean gas temperature increases because the blending ratio increases its ignition delay.
3.2.1. Mass fraction burned (MFB) The content of trapped charge of the cumulative heat release values
3.2.4. Rate of pressure rise The combustion process imposed a load which is known as the rate
Fig. 4. Variation of cylinder pressure with linseed oil fraction.
Fig. 6. Cumulative heat release of linseed oil blends and pure diesel. 4
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Fig. 7. Mean gas temperature of linseed oil blends and pure diesel. Fig. 9. Net heat release of linseed oil blends and pure diesel.
brief look at the Fig. 4 gives us a very important fact of the engine processing specifics. It has already been noted that in our research the blend of oil 30% and diesel 70% provides the minimum pressure value in the engine cylinder. It is obvious that a decrease in pressure in the cylinder leads to a drop in power of the engines. It also leads to a deterioration in the combustion efficiency and, as a result, worsens the energy conversion and increase in the number of pollutants. On the other hand, the efficiency of the entire thermodynamic cycle is a more important criterion for making the final conclusions. Therefore, we made an additional investigation of the efficiency of the thermodynamic cycle of the engine, which determines the perfection of the engine or efficiency of the energy conversion in it. We have developed the methodology for the determination of the thermodynamic cycle thermal efficiency. Fig. 10 presents the well-known diagram of the diesel thermodynamic cycle: On the basis of this scheme the maximum thermal efficiency of a diesel cycle is dependent on the compression ratio [24] shown in Eq. (1):
Fig. 8. Rate of the pressure rise of linseed oil blends and pure diesel.
of pressure rise. It determines the structural design of the engine. It is clear from Fig. 8 that the result of the rate of pressure rise is near to pure diesel at blend L50D50. However L40D60 blends have a higher rate of pressure rise than pure diesel and other blends.
ηth = 1 −
1 ⎡ αγ − 1 ⎤ r γ−1 ⎢ ⎣ γ (α − 1) ⎥ ⎦
where,
•η
th
3.2.5. Net heat release It is very much clear that from Fig. 9 the net heat release is higher at blend L50D50 among all blends of linseed oil and pure diesel. Maximum net heat release 31.6 J/deg. noticed at blend L50D50. However, the pattern of a graph of blends of linseed oil was quite the same as pure diesel. Net heat release depends upon the combustion phenomenon; better combustion gives maximum net heat release.
– thermal efficiency;
3.3. The thermal efficiency of the diesel engine thermodynamic cycle The analysis of the results above which were get with the standard procedure of the internal combustion engine testing shows that in general terms linseed oil can be mixed with pure diesel fuel and the blends of those fuels can be used for substitution of the pure diesel. This reduces the consumption of hydrocarbon fuels and improves the environmental friendliness of internal combustion engines through the use of renewable Biofuels. The conclusion above is related to any vegetable oil added to the pure diesel and was stated many times before this. Nevertheless, the
Fig. 10. Idealized diesel cycle. 5
(1)
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Fig. 11. PV-chart cycle of linseed oil blends and pure diesel.
Fig. 12. CP/CV of linseed oil blends and pure diesel.
• α – the cut off ratio V /V (ratio between the end and start volume for the heat addition); • r – the compression ratio V /V ; • γ– the ratio of specific heats C /C . 3
The ratio of the specific heats γ – the degree coefficient in the equation pVγ = const (see Fig. 10). Determination of the γ was performed by using Excel trend lines for each of the blends investigated. Dots in Fig. 11 corresponds to the calculated approximation with the power function in the form:
2
1
2
P
V
Thus, for the calculation of thermal efficiency of the thermodynamic cycle, we need to know the V1, V2, V3, and γ. All of these variables except γ can be found from the experimental data as shown in Fig. 11.
P = a + b·(V − c )γ
(2)
Here, a, b and c – are cycle-specific constants. a, and c are horizontal and vertical asymptotes correspondingly. They have a strong physical sense. a – is a lower value of the pressure in the cylinder during engine operation. c – is a minimal possible volume of the cylinder. It is obviously that c = 0. Constant b, as well as degree coefficient γ, were calculated as the
• V – the cylinder volume when the compression stage starts and expanding stage finishes; • V – the volume where the fuel ignition occurs; • V – the volume where fuel-burning stops, can be determined at the 1
2 3
point, where p3 = p2.
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vegetable oils. Those issues were observed because we use untreated oil for investigation. Therefore we did not present those results as they have no sense. The share in 50% of linseed oil seems to be an upper limit for using the untreated oil as an additive to pure diesel. However, the additional investigation should be made for the determination of the long-term use of it. At the same time, from the point of view of engine performance (Fig. 13) the share in 20% of the oil as an additive to the pure diesel is another maximum of the efficiency. Such a minor additive allows increase up to approximately 5% in the efficiency of the energy conversion of the engine. It is noteworthy that the results shown in Fig. 13 have been computed when the crank angle is 10°. It is known that the crank angle directly influences the ratio CP/CV [25], hence, it also has an influence on the thermal efficiency as well (as given in Eq. (1)). Therefore, the aforesaid results can be case-specific (for 10° crank angle) and need to be explored more for the concrete outcome.
Table 2 Average value of CP/CV. S. No.
Linseed oil share
Average value of CP/CV
1 2 3 4 5 6
0% 10% 20% 30% 40% 50%
1.227239 1.237919 1.245411 1.214813 1.232169 1.249032
trend coefficients In the idealized cycle, the γ for the compression stage (1–2) and the expansion stage (3–4) should be equal (Fig. 10). In the real cycle, they differ from each other. However, for the first approach, we can determine the values of γ for the compression stage and expanding stage separately and then take into account its simple average value. All three sets of data for the ratio of specific heats – compression stage, expansion stage and average are shown in Fig. 12. The average value of CP/CV is given in Table 2. In Fig. 13, the thermal efficiency of the diesel thermodynamic cycle has been plotted for various linseed oil share. The average values of specific heats CP/CV used in the calculation are given in Table 2 whereas the value of the cut-off ratio and compression ratio has been computed using experimental data shown in Fig. 11. The thermal efficiency has been computed using Eq. (1). Analyzing the results shows that the influence of the linseed oil share in blends on the engine efficiency is not monotony. It is clearly visible from Fig. 13 that increasing in linseed oil share from 0% (pure diesel) to 20% (L20D80) leads to increasing the engine efficiency. Then at the value of 30% linseed oil share, thermal efficiency falls lower than the efficiency of the pure diesel. For the following increase in the linseed oil share in blend up to 50% (L50D50) the engine efficiency increases again and becomes higher, than of Pure Diesel. In the range of blends investigated, the maximal and minimum thermal efficiency has been observed at the 50% linseed oil share (L50D50) and 30% linseed oil share (L30D70) respectively. It is worth noting that we have also tried to investigate the blends with more than 50% share of linseed oil and pure diesel, however, there were a few problems occur such as piston ring sticking, filter gumming, severe engine deposits, injector choking, by using vegetable oil in longterm use in diesel engines due to poor volatility, and high viscosity of
4. Conclusions The aim of this study was to investigate the effects of blends of linseed oil and pure diesel fuel on the combustion characteristics and thermal efficiency of a diesel engine. For this purpose, we have investigated blends of those fuels with the share of linseed oil from 0% to 50% with pure diesel by volume. The conclusions of the results obtained in this investigation are as follows:
• It • • •
has been shown in the research, that almost all combustion parameters are maximal at blend oil/diesel 50/50%. However, 50% of oil can affect negatively the engine’s long-term operation. We have also found that a blend of 30% of linseed oil and 70% of pure diesel is the worst mixture ratio from the point of view of the engine combustion parameters for the specific case considered in the present study. We have developed an effective procedure for the evaluation of the thermal efficiency of the internal combustion engine’s thermodynamic cycle based on the standard test equipment data of Enginesoft-LV. For the first time, the comparative analysis was performed for thermal efficiency of the thermodynamic cycle of the diesel engine operated with different blends of vegetable oils and pure diesel fuel. The results of the comparative analysis show that the thermal efficiency of some blends of pure diesel fuel and vegetable oil can be
Fig. 13. Thermal efficiency of linseed oil blends and pure diesel. 7
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higher than that of pure diesel.
• The results allow concluding that the addition of 20% of the linseed •
oil increases in the thermodynamic cycle of the investigated diesel engine up to 5%. This means improvement of the performance of the engine, i.e. most efficient energy conversion. The analysis of the engine’s thermal efficiency is very important and should be carried out for any fuel mixture during the investigation.
[12]
[13]
Declaration of Competing Interest
[14]
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.
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