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Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil
Alexandria Engineering Journal (2015) xxx, xxx–xxx
H O S T E D BY
Alexandria University
Alexandria Engineering Journal www.elsevier.com/locate/aej www.sciencedirect.com
ORIGINAL ARTICLE
Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil S. Prasanna Raj Yadav *, C.G. Saravanan, M. Kannan Annamalai University, Annamalai Nagar, Tamil Nadu, India Received 24 November 2014; revised 23 June 2015; accepted 22 July 2015
KEYWORDS Waste transformer oil; Injection timing; Diesel engine; Emission; Trans-esterification
Abstract This research work targets on the effective utilization of WTO (waste transformer oil) in a diesel engine, which would rather reduce environmental problems caused by disposing of it in the open land. The waste transformer oil was compared with the conventional diesel fuel and found that it can also be used as fuel in compression ignition engines since the WTO is also a derivative of crude oil. In this present work, the WTO has been subjected to traditional base-catalyzed transesterification process in order to reduce the high viscosity of the WTO which helps to effectively utilize WTO as a fuel in DI diesel engine. The objective of the work is to study the influence of injection timing on the performance, emission and combustion characteristics of a single cylinder, four stroke, direct injection diesel engine using TWTO (trans-esterified waste transformer oil) as a fuel. Experiments were performed at four injection timings (23, 22, 21, and 20 bTDC). The results indicate that the retarded injection timing of 20 bTDC resulted in decreased oxides of nitrogen, carbon monoxide and unburned hydrocarbon by 11.57%, 17.24%, and 10% respectively while the brake thermal efficiency and smoke increased under all the load conditions when compared to that of standard injection timing. ª 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction Rapid depletion of conventional fossil fuels, increasing pollution levels by combustion of fossil fuels and their increasing prices make alternative fuel sources more attractive. Petroleum-based fuels are limited reserves, concentrated in certain regions of the world and are shortening day by day [4–6]. Huge amount of dollars is being invested in the search for alternative fuels. Meanwhile, the disposal of waste or used * Corresponding author. Tel.: +91 9786190834. E-mail address: [email protected] (S.P.R. Yadav). Peer review under responsibility of Faculty of Engineering, Alexandria University.
transformer oil from electrical power stations and from the large number of transformers located throughout the country is becoming increasingly complex. Over a long period of time, petroleum-based mineral oils have been used in liquid-filled electrical transformers primarily [24]. It is well known that the transformer oil is employed in the electrical transformer for insulating purpose, additionally, cooling is another purpose of using transformer oil in the electrical transformer while the transformer is in operation. The insulating oil used in electric transformers consists of complex blends of more than 3000 hydrocarbons and all the transformer oil is essentially highly branched aliphatic and aromatic, napthenic or parafenic crudes [31,17] that are extracted or refined and conditioned into hydrocarbon oils.
http://dx.doi.org/10.1016/j.aej.2015.07.008 1110-0168 ª 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
2 Conversion of waste-to-energy aims to replace conventional fuels. Fuels such as alcohol, biodiesel, and liquid fuel from plastics are alternative fuels for internal combustion engines [19–21]. Most of the research works are focussed on different waste energy sources such as waste lubrication oil, plastic oils, and tire pyrolysis oil. A large amount of waste energy sources are discharged without utilizing the energy content available in the waste disposals. In this work, the used transformer oils disposed as waste from power generation plant are collected and then refined in order to utilize the available energy content in the waste oils. The disposal of waste transformer oil is also becoming complex since it could contaminate the soil and waterways, if serious spills occur. Government regulatory agents are already looking into this problem and are imposing penalties for spills. Many transformers are located in populated areas and shopping centers. The long term usage of the transformer oil in the power or electric transformer causes some changes in its physic-chemical characteristics [31,17] and makes the oil unfit to be used for insulating purpose in the electric transformer. So the waste transformer oil becomes one of the most important energy sources. The effective utilization of waste transformer oil may reduce environmental problems rather disposing it in the open land. After a proper treatment, waste transformer oil can be used as an alternative fuel in CI engine. The use of transformer oil as a substitute for diesel fuel provides an opportunity to minimize the over exploitation of already depleting natural resources. Previously studies have been carried out on the utilization of tire pyrolysis oil, waste lubricating oil, and waste cooking oil as an engine fuel substitute. In this regard [22], demonstrated the effective utilization of waste plastic oil, a renewable and biodegradable fuel produced by crackling process, in a diesel engine. Based on their study, reports on reduction in NOx (oxides of nitrogen), CO (carbon monoxide) and UHC (un-burnt hydrocarbon) emission and increase in BTE (brake thermal efficiency) were documented for waste plastic oil at a retarded injection timing of 14 CA (crank angle) BTDC (before top dead center). Similarly [1], identified that the engine lubrication oil is being discarded as waste and thus, initiated an attempt to utilize it as a fuel for diesel engine. In their venture, DLF (diesel like fuel) was produced from waste engine lubricating oil by pyrolytic distillation method and the measured properties of the produced DLF were found conducive for its use in a diesel engine [26–30]. Subsequently, the experimental investigation of it in a diesel engine revealed an increase in engine torque and BTE, while emissions such as CO and NOx were shown to be reduced. But very few attempts have been made on the usage of waste transformer oil as an engine fuel substitute. [2] experimentally investigated the waste transformer oil without any processing has been directly blended with diesel and used as a fuel in the engine and it was reported the increase in brake thermal efficiency with significant reduction of smoke. In this work, waste transformer oil collected from dieselelectric power station located in the Annamalai University campus has been decidedly chosen for necessary processing and utilized as an engine fuel substitute. Transformer oil, stable under all conditions of use and storage can be blended with petrol-based fuel readily. The oil used in this study is golden brownish color with high viscosity and having higher hydrocarbon compounds as a major constituent. The waste transformer oil cannot be used directly on the engine because
S.P.R. Yadav et al. of its high viscosity which could result in poor atomization. The solution to the problem has been approached in several ways, such as preheating the oil, blending them with diesel, pyrolysis, traditional base-catalyzed trans-esterification and catalytic cracking. In this work, traditional base-catalyzed trans-esterification has been implemented to reduce the viscosity of the waste transformer oil and thereby converting it into TWTO (trans-esterified waste transformer oil) as fuel for diesel engine. The objective of the work is to study the influence of injection timing on the performance, emission and combustion characteristics of a DI diesel engine using TWTO as a fuel. The TWTO obtained after traditional base-catalyzed transesterification process is subject to FTIR (Fourier transform infrared) analysis to identify the functional group and compositional analysis. The physical properties of TWTO such as specific gravity, kinematic viscosity, flash point, gross calorific value, density and cetane number have also been obtained. 2. Traditional base-catalyzed trans-esterification procedure The fuel used in this study was extracted from the transesterification of waste transformer oil, purified from dust, metal particles, gum-type materials and other impurities have been treated with methanol (CH3OH) catalyzed by potassium hydroxide (KOH). A titration was performed to determine the amount of KOH needed to neutralize and break the long chain hydrocarbons present in the waste transformer oil. The amount of KOH needed as catalyst for every liter of waste transformer oil was determined as 12 g. For transesterification, 210 ml CH3OH plus the required amount of KOH were added for every liter of waste transformer oil, and the reactions were carried out at 45 C. One liter of waste transformer oil is first subjected to 65 C for 30 min and then 12 g of KOH, which is dissolved in 210 ml of CH3OH is poured into one liter of waste transformer oil. The water wash process was performed by using a sprinkler which slowly sprinkled water into the oil container until there was an equal amount of water and oil in the container. The water hydrocarbon mixture was then agitated gently for 20 min, allowing the water to settle out of the hydrocarbon mixture. After the mixture had settled, the water was drained out. The properties of the trans-esterified waste transformer oil and diesel are shown in Table 1.
Table 1 Properties of trans-esterified waste transformer oil and diesel. Property
Measurement standards
WTO
Diesel
100% TWTO
Specific gravity @ 27 C Kinematic viscosity @40 C in CSt Flash Point in C Fire Point in C Gross calorific value in kcal/kg Density@15 C in gm/cc Cetane number
ASTM D1298
0.8512
0.8298
0.8503
ASTM D445
11.06
2.57
10.80
ASTM D92 ASTM D92 ASTM D240
144 152 10,218
37 40 10,738
136 143 10,233
ASTM D1298
0.8604
0.8072
0.8494
ASTM D976
52.7
52
49.1
Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
Influence of injection timing on DI diesel engine characteristics 3. Experimental 3.1. Fuel characteristic evaluation The TWTO is subjected to the evaluation of thermal and physical characteristics. FTIR analysis is also performed to determine the functional groups and compositional analysis. The physical properties of TWTO such as specific gravity, density, flash point, fire point, gross calorific value and cetane number were calculated by ASTM methods and compared to that of diesel fuel in Table 1. It is indicated from the table that the values of standard diesel fuel and TWTO are reasonably close. From the above mentioned test results, it is inferred the TWTO resembles and is almost close to that of diesel. So it can be concluded that TWTO can be used as fuel in the engine. 3.2. Fourier transform infrared (FTIR) spectra for diesel fuel and TWTO The FTIR spectrums of conventional diesel and TWTO (transesterified waste transformer oil) were recorded after scanning
Figure 1
3 on FTIR is shown in Figs. 1 and 2 respectively. Table 2 represents the family, bond types for the diesel fuel and transesterified waste transformer oil. In case of diesel fuel, the strong absorbance frequencies 2921.40 and 2853.56 cm 1 represent C–H stretching. The absorbance peaks 1459.56 cm 1 represented the C–H bending which indicates the presence of alkanes. For catalytic cracked transformer oil strong absorbance peaks 2921.16 cm 1 and 2852.87 cm 1 represent the C–H stretching. The absorbance peaks 1460.80 cm 1 and 750.5 cm 1 represented the C–H bending and C–H out of plane bend respectively indicating the presence of alkanes. From the FTIR graph it is seen that major transmittance spectrums peaks both of the fuels are alkanes. Based on the above discussion it is clear that both of the oil is saturated hydrocarbon. The presence of hydrocarbon groups C–H indicates that the liquid has a potential to be used as fuels. Similar FTIR results for transformer oil have been reported by [23]. 3.3. Engine test The compression ignition engine used for the study was Kirloskar TV-I, single cylinder, four stroke, constant speed, vertical, water cooled and direct injection diesel engine and the details are given in Table 3. The experimental setup was shown in Fig. 3. The engine was coupled with an eddy current dynamometer to apply different engine loads. Measurement of combustion chamber pressure was obtained by installing an AVL make transducer with the sensitivity 16:11 PC/bar, water cooled piezoelectric pressure transducer into the cylinder head of the combustion chamber. An AVL 3057 charge amplifier converts the charge yield by the piezoelectric transducer into
Table 3
FTIR of diesel fuel.
Test engine specification.
Make General details Number of cylinder Bore Stroke Compression ratio Rated speed Rated output Injection pressure Fuel injection timing Lubricating oil
Figure 2
Table 2
Kirloskar-TV 1 Four stroke, compression ignition, constant Speed, vertical, water cooled, direct injection One 87.5 mm 110 mm 17.5:1 1500 rpm 5.2 kW 220 bar 23 bTDC SAE 40
FTIR of TWTO.
FTIR results for diesel and TWTO.
Diesel
WTO 1
Frequency range (cm )
Bond types
Family
Frequency range (cm 1)
Bond types
Family
2921.40–2853.56 1459.56 1375.32 752.59
C–H stretching C–H bending C–X C–H bend
Alkanes Alkanes Fluoride Alkanes
2921.16–2852.87 1460.8 1348.75 654.39
C–H stretching C–H bending C–X C–H bend
Alkanes Alkanes Fluoride Alkanes
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S.P.R. Yadav et al.
Figure 3
Experimental setup.
proportional electric signals. A personal computer (PC) was interfaced with an AVL 619 Indimeter Hardware and Indwin – software version 2.2 data acquisition system to collect combustion parameter data, such as heat release rate, in-cylinder pressure and cyclic variations. ChromelAlumel (k-type) thermocouples were installed to measure gas temperature at inlet and outlet ducts. The engine speed was measured by inhouse designed magnetic pickup sensor connected to frequency meter. The smoke intensity was measured by an AVL 413 smoke meter and Nitrous oxides (NOx), Carbon monoxide (CO), Hydrocarbon (HC) and Carbon dioxide (CO2) were measured by an AVL 444 DI gas analyzer. The engine was started and warmed up at every stage and the cold water temperature was maintained. Then the fuel consumption, exhaust gas temperature and exhaust emissions of NOx, CO, HC, smoke, were measured and recorded for different loads. At each operating point, the combustion parameters were also processed and stored in the personal computer (PC) for post-processing of the results. The tests were repeated for three times and each test was done for 3 h. Finally, the average value of the three readings was taken for the calculation. 3.4. Estimation of uncertainty The uncertainties and errors can arise from instrument selection, environmental condition, calibration, testing, observation and while taking readings. Uncertainty in any repeatability and the other is random errors which can be calculated analytically. In this research, an uncertainty analysis was performed using the method described by J.P. Holman. The details of the instruments used are given in Table 4. The total percentage of the uncertainty of this experiment is calculated as given below. Total percentage of uncertainty of this experiment = [(TFC)2 + (BP)2 + (BSFC)2 + (brake
Table 4
Instrument details.
Instrument
Measurement
Accuracy uncertainty
Burette Load cell Speed Sensor Temperature indicator
Fuel consumption Loading device Speed Exhaust gas measurement
±0.2 cc ±10 N ±10 rpm ±2 C
1.5 0.2 1.0 0.30
Exhaust gas analyzer
CO HC NOx
±0.02% ±10 ppm ±12 ppm
0.2 0.1 0.2
Smoke Pressure transducer Crank angle encoder
Smoke density Cylinder pressure Crank angle
±1 ±0.3 kg ±1
1 0.3 1
thermal efficiency)2 + (CO)2 + (UBHC)2 + (NOx)2 + (smoke number)2 + (EGT)2 + (uncertainty of pressure pick up)2 + (crank angle encoder)2]1/2 = [(1.5)2 + (0.2)2 + (1.5)2 + (1) 2 + (0.2) 2 + (0.1) 2 + (0.2) 2 + (1) 2 + (0.3) 2 + (0.3) 2 + (1) 2 ] = ± 2.79%. 4. Results and discussion 4.1. Performance analysis Fig. 4 compares the variation of specific fuel consumption (SFC) of trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. The SFC of the diesel fuel with standard and retarded injection timing is also compared. The Graph Sit and Rit represents standard injection timing and retarded injection timing respectively whereas DF and
Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
Influence of injection timing on DI diesel engine characteristics
5 4.2. Emission tests
Figure 4 power.
Variation of specific fuel consumption against brake
WTO represents diesel fuel and Trans-esterified waste transformer oil respectively. The brake specific fuel consumption varies from 0.62 kg/kW h at initial load to 0.33 kg/kW h at maximum load for standard injection timing and it varies from 0.61 kg/kW h at initial load to 0.32 kg/kW h for retarded injection timing. Fig. 5 shows the variation of brake thermal efficiency (BTE) with brake power for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. The BTE of the diesel fuel with standard and retarded injection timing is also compared. The BTE of the engine is improved when fueled with trans-esterified waste transformer oil (TWTO) with retarded injection timing. It can be observed from the figure that the thermal efficiency is 25.06% at maximum load for standard injection timing and for the retarded injection timing, and it is 27.19%. The possible reason for this is that the retardation of injection timing leads to rapid start of combustion and the combustion phenomenon prolongs during the power stroke. This results in complete combustion and enables to attain higher efficiency while operating with retarded injection timing.
Fig. 6 shows the variation of CO emissions with load for transesterified waste transformer oil (TWTO) with standard and retarded injection timing. The engine emits less CO using TWTO operating with retarded injection timing when compared to standard injection timing. TWTO operating with retarded injection timing provides sufficient ignition delay for the excess oxygen content present in the TWTO to mix well with air. That is, the amount of the CO produced during combustion of TWTO may be converted into CO2 by taking up the additional oxygen molecule present in the TWTO chain and thus reduced CO formation [14–16,25]. Fig. 7 shows the smoke density variation of the engine for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. It is observed from the graph that the smoke increases with retarded injection timing when compared to that of standard injection timing. Smoke varies from 20.8 HSU at initial load to 62.1 HSU at maximum load whereas it varies from 22.638 HSU at initial load to 64.328 HSU at maximum load for retarded injection timing. The possible increase may be probably due to aromatic content present in TWTO.
Figure 6
Figure 5 power.
Variations of CO against brake power.
Variations of brake thermal efficiency against brake Figure 7
Variations of smoke density against brake power.
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Fig. 8 shows the variation of NOx emission with brake power for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. NOx is formed by chain reactions involving nitrogen and oxygen in the air. These reactions depend especially on temperature arising from high activation energy. Since diesel engines always operate with excess air, NOx emissions are mainly a function of gas temperature and residence time [11–13]. At the same time, it is known that the NOx formation is dependent upon the volumetric efficiency [8–10]. In many studies, it was seen that the NOx emission varied linearly with the engine load, and similar results were obtained in this study also. The NOx emission of the engine with trans-esterified waste transformer oil (TWTO) with retarded injection timing is 12. When the injection timing is retarded, a decrease in the NOx emissions at all the loads was observed. When the injection timing is retarded, the crank angle at which the cylinder peak pressure occurs is delayed due to the late combustion of fuel. At the time of start of combustion, the accumulated fuel is less when injection timing is retarded and therefore premixed combustion stage is less intense leading to lower rate of heat release. It is seen in Fig. 9 that there is an important decrease in the HC emission with TWTO operating with retarded injection
Figure 8
Figure 9 power.
Variations NOx against brake power.
timing when compared to that of standard injection timing. The increased gas temperature and the cetane number are the reasons for this decrease. The high temperature of the burned gases precludes the condensation of the heaviest hydrocarbons in the sampling line, recommending proper conditions for HC emission analysis [18,7]. Also, the higher oxygen content of the blended fuels compared to that of diesel fuel improves the combustion quality, thus leading to lower HC emission [3]. 4.3. Combustion parameters Fig. 10 shows the variation of cylinder pressure with crank angle for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. From this figure, it is clear that the peak cylinder pressure is slightly decreased with retarded injection timing when compared to that of standard injection timing. The cylinder pressure of a compression ignition engine mainly depends on the amount of fuel accumulated in the delay period and the combustion rate in the initial stages of premixed combustion [32]. The reason for the slight decrease in cylinder pressure with retarded injection timing of TWTO may probably because of reduced evaporation and mixing with air. However, the combustion process is similar, consisting of a phase of premixed combustion following by a phase of diffusion combustion. Premixed combustion phase is controlled by the ignition delay period and the spray envelope of the injected fuel. Fig. 11 shows the variation of heat release rate with crank angle for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. The heat release rate in the premixed combustion phase depends on the ignition delay, the mixture formation and the combustion rate in the initial stages of combustion [10]. From this figure, it is clear that the heat release rate of retarded injection timing is lower when operating with standard injection timing. The reason may probably be a shorter ignition delay exhibited during retarded injection timing and its blends cause the air–fuel mixture to accumulate in the combustion chamber. Further, due to entrapment of fuel/air mixture in the combustion chamber during the delay period, more quantity of fuel is burnt in the premixed combustion phase.
Variations of HC against brake power against brake Figure 10
Variations of cylinder pressure against crank angle.
Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
Influence of injection timing on DI diesel engine characteristics
Figure 11
Variations of heat release rate against crank angle.
5. Conclusion In this experimental study, effects of trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing were investigated. When the injection timing is retarded from 23 bTDC to 20 bTDC, the most important conclusions are outlined as follows: 1. It is observed that the trans-esterified waste transformer oil (TWTO) can be used as a fuel in diesel engines without any problems in terms of engine performance. 2. The properties of trans-esterified waste transformer oil (TWTO) are comparable to conventional diesel fuel. The physical properties such as specific gravity, kinematic viscosity, calorific value, cetane number, flash point and fire point were determined. The results of the FTIR analysis of trans-esterified waste transformer oil showed that it has the characteristics similar to that of conventional diesel fuel. 3. From the experimental investigation, it is observed that TWTO operating with retarded injection timing shows slight improvement in brake thermal efficiency when compared to that of standard injection timing. An increase in thermal efficiency at the expense of higher smoke is achieved for a constant speed diesel engine. 4. Exhaust emissions reduced with TWTO operating with the retarded injection timing when compared to that of standard injection timing. At maximum load conditions, it reduces CO (carbon monoxide), NOx, HC (hydrocarbon) emission by 17.24%, 11.57%, and 10% respectively.
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Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
H O S T E D BY
Alexandria University
Alexandria Engineering Journal www.elsevier.com/locate/aej www.sciencedirect.com
ORIGINAL ARTICLE
Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil S. Prasanna Raj Yadav *, C.G. Saravanan, M. Kannan Annamalai University, Annamalai Nagar, Tamil Nadu, India Received 24 November 2014; revised 23 June 2015; accepted 22 July 2015
KEYWORDS Waste transformer oil; Injection timing; Diesel engine; Emission; Trans-esterification
Abstract This research work targets on the effective utilization of WTO (waste transformer oil) in a diesel engine, which would rather reduce environmental problems caused by disposing of it in the open land. The waste transformer oil was compared with the conventional diesel fuel and found that it can also be used as fuel in compression ignition engines since the WTO is also a derivative of crude oil. In this present work, the WTO has been subjected to traditional base-catalyzed transesterification process in order to reduce the high viscosity of the WTO which helps to effectively utilize WTO as a fuel in DI diesel engine. The objective of the work is to study the influence of injection timing on the performance, emission and combustion characteristics of a single cylinder, four stroke, direct injection diesel engine using TWTO (trans-esterified waste transformer oil) as a fuel. Experiments were performed at four injection timings (23, 22, 21, and 20 bTDC). The results indicate that the retarded injection timing of 20 bTDC resulted in decreased oxides of nitrogen, carbon monoxide and unburned hydrocarbon by 11.57%, 17.24%, and 10% respectively while the brake thermal efficiency and smoke increased under all the load conditions when compared to that of standard injection timing. ª 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction Rapid depletion of conventional fossil fuels, increasing pollution levels by combustion of fossil fuels and their increasing prices make alternative fuel sources more attractive. Petroleum-based fuels are limited reserves, concentrated in certain regions of the world and are shortening day by day [4–6]. Huge amount of dollars is being invested in the search for alternative fuels. Meanwhile, the disposal of waste or used * Corresponding author. Tel.: +91 9786190834. E-mail address: [email protected] (S.P.R. Yadav). Peer review under responsibility of Faculty of Engineering, Alexandria University.
transformer oil from electrical power stations and from the large number of transformers located throughout the country is becoming increasingly complex. Over a long period of time, petroleum-based mineral oils have been used in liquid-filled electrical transformers primarily [24]. It is well known that the transformer oil is employed in the electrical transformer for insulating purpose, additionally, cooling is another purpose of using transformer oil in the electrical transformer while the transformer is in operation. The insulating oil used in electric transformers consists of complex blends of more than 3000 hydrocarbons and all the transformer oil is essentially highly branched aliphatic and aromatic, napthenic or parafenic crudes [31,17] that are extracted or refined and conditioned into hydrocarbon oils.
http://dx.doi.org/10.1016/j.aej.2015.07.008 1110-0168 ª 2015 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
2 Conversion of waste-to-energy aims to replace conventional fuels. Fuels such as alcohol, biodiesel, and liquid fuel from plastics are alternative fuels for internal combustion engines [19–21]. Most of the research works are focussed on different waste energy sources such as waste lubrication oil, plastic oils, and tire pyrolysis oil. A large amount of waste energy sources are discharged without utilizing the energy content available in the waste disposals. In this work, the used transformer oils disposed as waste from power generation plant are collected and then refined in order to utilize the available energy content in the waste oils. The disposal of waste transformer oil is also becoming complex since it could contaminate the soil and waterways, if serious spills occur. Government regulatory agents are already looking into this problem and are imposing penalties for spills. Many transformers are located in populated areas and shopping centers. The long term usage of the transformer oil in the power or electric transformer causes some changes in its physic-chemical characteristics [31,17] and makes the oil unfit to be used for insulating purpose in the electric transformer. So the waste transformer oil becomes one of the most important energy sources. The effective utilization of waste transformer oil may reduce environmental problems rather disposing it in the open land. After a proper treatment, waste transformer oil can be used as an alternative fuel in CI engine. The use of transformer oil as a substitute for diesel fuel provides an opportunity to minimize the over exploitation of already depleting natural resources. Previously studies have been carried out on the utilization of tire pyrolysis oil, waste lubricating oil, and waste cooking oil as an engine fuel substitute. In this regard [22], demonstrated the effective utilization of waste plastic oil, a renewable and biodegradable fuel produced by crackling process, in a diesel engine. Based on their study, reports on reduction in NOx (oxides of nitrogen), CO (carbon monoxide) and UHC (un-burnt hydrocarbon) emission and increase in BTE (brake thermal efficiency) were documented for waste plastic oil at a retarded injection timing of 14 CA (crank angle) BTDC (before top dead center). Similarly [1], identified that the engine lubrication oil is being discarded as waste and thus, initiated an attempt to utilize it as a fuel for diesel engine. In their venture, DLF (diesel like fuel) was produced from waste engine lubricating oil by pyrolytic distillation method and the measured properties of the produced DLF were found conducive for its use in a diesel engine [26–30]. Subsequently, the experimental investigation of it in a diesel engine revealed an increase in engine torque and BTE, while emissions such as CO and NOx were shown to be reduced. But very few attempts have been made on the usage of waste transformer oil as an engine fuel substitute. [2] experimentally investigated the waste transformer oil without any processing has been directly blended with diesel and used as a fuel in the engine and it was reported the increase in brake thermal efficiency with significant reduction of smoke. In this work, waste transformer oil collected from dieselelectric power station located in the Annamalai University campus has been decidedly chosen for necessary processing and utilized as an engine fuel substitute. Transformer oil, stable under all conditions of use and storage can be blended with petrol-based fuel readily. The oil used in this study is golden brownish color with high viscosity and having higher hydrocarbon compounds as a major constituent. The waste transformer oil cannot be used directly on the engine because
S.P.R. Yadav et al. of its high viscosity which could result in poor atomization. The solution to the problem has been approached in several ways, such as preheating the oil, blending them with diesel, pyrolysis, traditional base-catalyzed trans-esterification and catalytic cracking. In this work, traditional base-catalyzed trans-esterification has been implemented to reduce the viscosity of the waste transformer oil and thereby converting it into TWTO (trans-esterified waste transformer oil) as fuel for diesel engine. The objective of the work is to study the influence of injection timing on the performance, emission and combustion characteristics of a DI diesel engine using TWTO as a fuel. The TWTO obtained after traditional base-catalyzed transesterification process is subject to FTIR (Fourier transform infrared) analysis to identify the functional group and compositional analysis. The physical properties of TWTO such as specific gravity, kinematic viscosity, flash point, gross calorific value, density and cetane number have also been obtained. 2. Traditional base-catalyzed trans-esterification procedure The fuel used in this study was extracted from the transesterification of waste transformer oil, purified from dust, metal particles, gum-type materials and other impurities have been treated with methanol (CH3OH) catalyzed by potassium hydroxide (KOH). A titration was performed to determine the amount of KOH needed to neutralize and break the long chain hydrocarbons present in the waste transformer oil. The amount of KOH needed as catalyst for every liter of waste transformer oil was determined as 12 g. For transesterification, 210 ml CH3OH plus the required amount of KOH were added for every liter of waste transformer oil, and the reactions were carried out at 45 C. One liter of waste transformer oil is first subjected to 65 C for 30 min and then 12 g of KOH, which is dissolved in 210 ml of CH3OH is poured into one liter of waste transformer oil. The water wash process was performed by using a sprinkler which slowly sprinkled water into the oil container until there was an equal amount of water and oil in the container. The water hydrocarbon mixture was then agitated gently for 20 min, allowing the water to settle out of the hydrocarbon mixture. After the mixture had settled, the water was drained out. The properties of the trans-esterified waste transformer oil and diesel are shown in Table 1.
Table 1 Properties of trans-esterified waste transformer oil and diesel. Property
Measurement standards
WTO
Diesel
100% TWTO
Specific gravity @ 27 C Kinematic viscosity @40 C in CSt Flash Point in C Fire Point in C Gross calorific value in kcal/kg Density@15 C in gm/cc Cetane number
ASTM D1298
0.8512
0.8298
0.8503
ASTM D445
11.06
2.57
10.80
ASTM D92 ASTM D92 ASTM D240
144 152 10,218
37 40 10,738
136 143 10,233
ASTM D1298
0.8604
0.8072
0.8494
ASTM D976
52.7
52
49.1
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Influence of injection timing on DI diesel engine characteristics 3. Experimental 3.1. Fuel characteristic evaluation The TWTO is subjected to the evaluation of thermal and physical characteristics. FTIR analysis is also performed to determine the functional groups and compositional analysis. The physical properties of TWTO such as specific gravity, density, flash point, fire point, gross calorific value and cetane number were calculated by ASTM methods and compared to that of diesel fuel in Table 1. It is indicated from the table that the values of standard diesel fuel and TWTO are reasonably close. From the above mentioned test results, it is inferred the TWTO resembles and is almost close to that of diesel. So it can be concluded that TWTO can be used as fuel in the engine. 3.2. Fourier transform infrared (FTIR) spectra for diesel fuel and TWTO The FTIR spectrums of conventional diesel and TWTO (transesterified waste transformer oil) were recorded after scanning
Figure 1
3 on FTIR is shown in Figs. 1 and 2 respectively. Table 2 represents the family, bond types for the diesel fuel and transesterified waste transformer oil. In case of diesel fuel, the strong absorbance frequencies 2921.40 and 2853.56 cm 1 represent C–H stretching. The absorbance peaks 1459.56 cm 1 represented the C–H bending which indicates the presence of alkanes. For catalytic cracked transformer oil strong absorbance peaks 2921.16 cm 1 and 2852.87 cm 1 represent the C–H stretching. The absorbance peaks 1460.80 cm 1 and 750.5 cm 1 represented the C–H bending and C–H out of plane bend respectively indicating the presence of alkanes. From the FTIR graph it is seen that major transmittance spectrums peaks both of the fuels are alkanes. Based on the above discussion it is clear that both of the oil is saturated hydrocarbon. The presence of hydrocarbon groups C–H indicates that the liquid has a potential to be used as fuels. Similar FTIR results for transformer oil have been reported by [23]. 3.3. Engine test The compression ignition engine used for the study was Kirloskar TV-I, single cylinder, four stroke, constant speed, vertical, water cooled and direct injection diesel engine and the details are given in Table 3. The experimental setup was shown in Fig. 3. The engine was coupled with an eddy current dynamometer to apply different engine loads. Measurement of combustion chamber pressure was obtained by installing an AVL make transducer with the sensitivity 16:11 PC/bar, water cooled piezoelectric pressure transducer into the cylinder head of the combustion chamber. An AVL 3057 charge amplifier converts the charge yield by the piezoelectric transducer into
Table 3
FTIR of diesel fuel.
Test engine specification.
Make General details Number of cylinder Bore Stroke Compression ratio Rated speed Rated output Injection pressure Fuel injection timing Lubricating oil
Figure 2
Table 2
Kirloskar-TV 1 Four stroke, compression ignition, constant Speed, vertical, water cooled, direct injection One 87.5 mm 110 mm 17.5:1 1500 rpm 5.2 kW 220 bar 23 bTDC SAE 40
FTIR of TWTO.
FTIR results for diesel and TWTO.
Diesel
WTO 1
Frequency range (cm )
Bond types
Family
Frequency range (cm 1)
Bond types
Family
2921.40–2853.56 1459.56 1375.32 752.59
C–H stretching C–H bending C–X C–H bend
Alkanes Alkanes Fluoride Alkanes
2921.16–2852.87 1460.8 1348.75 654.39
C–H stretching C–H bending C–X C–H bend
Alkanes Alkanes Fluoride Alkanes
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S.P.R. Yadav et al.
Figure 3
Experimental setup.
proportional electric signals. A personal computer (PC) was interfaced with an AVL 619 Indimeter Hardware and Indwin – software version 2.2 data acquisition system to collect combustion parameter data, such as heat release rate, in-cylinder pressure and cyclic variations. ChromelAlumel (k-type) thermocouples were installed to measure gas temperature at inlet and outlet ducts. The engine speed was measured by inhouse designed magnetic pickup sensor connected to frequency meter. The smoke intensity was measured by an AVL 413 smoke meter and Nitrous oxides (NOx), Carbon monoxide (CO), Hydrocarbon (HC) and Carbon dioxide (CO2) were measured by an AVL 444 DI gas analyzer. The engine was started and warmed up at every stage and the cold water temperature was maintained. Then the fuel consumption, exhaust gas temperature and exhaust emissions of NOx, CO, HC, smoke, were measured and recorded for different loads. At each operating point, the combustion parameters were also processed and stored in the personal computer (PC) for post-processing of the results. The tests were repeated for three times and each test was done for 3 h. Finally, the average value of the three readings was taken for the calculation. 3.4. Estimation of uncertainty The uncertainties and errors can arise from instrument selection, environmental condition, calibration, testing, observation and while taking readings. Uncertainty in any repeatability and the other is random errors which can be calculated analytically. In this research, an uncertainty analysis was performed using the method described by J.P. Holman. The details of the instruments used are given in Table 4. The total percentage of the uncertainty of this experiment is calculated as given below. Total percentage of uncertainty of this experiment = [(TFC)2 + (BP)2 + (BSFC)2 + (brake
Table 4
Instrument details.
Instrument
Measurement
Accuracy uncertainty
Burette Load cell Speed Sensor Temperature indicator
Fuel consumption Loading device Speed Exhaust gas measurement
±0.2 cc ±10 N ±10 rpm ±2 C
1.5 0.2 1.0 0.30
Exhaust gas analyzer
CO HC NOx
±0.02% ±10 ppm ±12 ppm
0.2 0.1 0.2
Smoke Pressure transducer Crank angle encoder
Smoke density Cylinder pressure Crank angle
±1 ±0.3 kg ±1
1 0.3 1
thermal efficiency)2 + (CO)2 + (UBHC)2 + (NOx)2 + (smoke number)2 + (EGT)2 + (uncertainty of pressure pick up)2 + (crank angle encoder)2]1/2 = [(1.5)2 + (0.2)2 + (1.5)2 + (1) 2 + (0.2) 2 + (0.1) 2 + (0.2) 2 + (1) 2 + (0.3) 2 + (0.3) 2 + (1) 2 ] = ± 2.79%. 4. Results and discussion 4.1. Performance analysis Fig. 4 compares the variation of specific fuel consumption (SFC) of trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. The SFC of the diesel fuel with standard and retarded injection timing is also compared. The Graph Sit and Rit represents standard injection timing and retarded injection timing respectively whereas DF and
Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
Influence of injection timing on DI diesel engine characteristics
5 4.2. Emission tests
Figure 4 power.
Variation of specific fuel consumption against brake
WTO represents diesel fuel and Trans-esterified waste transformer oil respectively. The brake specific fuel consumption varies from 0.62 kg/kW h at initial load to 0.33 kg/kW h at maximum load for standard injection timing and it varies from 0.61 kg/kW h at initial load to 0.32 kg/kW h for retarded injection timing. Fig. 5 shows the variation of brake thermal efficiency (BTE) with brake power for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. The BTE of the diesel fuel with standard and retarded injection timing is also compared. The BTE of the engine is improved when fueled with trans-esterified waste transformer oil (TWTO) with retarded injection timing. It can be observed from the figure that the thermal efficiency is 25.06% at maximum load for standard injection timing and for the retarded injection timing, and it is 27.19%. The possible reason for this is that the retardation of injection timing leads to rapid start of combustion and the combustion phenomenon prolongs during the power stroke. This results in complete combustion and enables to attain higher efficiency while operating with retarded injection timing.
Fig. 6 shows the variation of CO emissions with load for transesterified waste transformer oil (TWTO) with standard and retarded injection timing. The engine emits less CO using TWTO operating with retarded injection timing when compared to standard injection timing. TWTO operating with retarded injection timing provides sufficient ignition delay for the excess oxygen content present in the TWTO to mix well with air. That is, the amount of the CO produced during combustion of TWTO may be converted into CO2 by taking up the additional oxygen molecule present in the TWTO chain and thus reduced CO formation [14–16,25]. Fig. 7 shows the smoke density variation of the engine for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. It is observed from the graph that the smoke increases with retarded injection timing when compared to that of standard injection timing. Smoke varies from 20.8 HSU at initial load to 62.1 HSU at maximum load whereas it varies from 22.638 HSU at initial load to 64.328 HSU at maximum load for retarded injection timing. The possible increase may be probably due to aromatic content present in TWTO.
Figure 6
Figure 5 power.
Variations of CO against brake power.
Variations of brake thermal efficiency against brake Figure 7
Variations of smoke density against brake power.
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Fig. 8 shows the variation of NOx emission with brake power for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. NOx is formed by chain reactions involving nitrogen and oxygen in the air. These reactions depend especially on temperature arising from high activation energy. Since diesel engines always operate with excess air, NOx emissions are mainly a function of gas temperature and residence time [11–13]. At the same time, it is known that the NOx formation is dependent upon the volumetric efficiency [8–10]. In many studies, it was seen that the NOx emission varied linearly with the engine load, and similar results were obtained in this study also. The NOx emission of the engine with trans-esterified waste transformer oil (TWTO) with retarded injection timing is 12. When the injection timing is retarded, a decrease in the NOx emissions at all the loads was observed. When the injection timing is retarded, the crank angle at which the cylinder peak pressure occurs is delayed due to the late combustion of fuel. At the time of start of combustion, the accumulated fuel is less when injection timing is retarded and therefore premixed combustion stage is less intense leading to lower rate of heat release. It is seen in Fig. 9 that there is an important decrease in the HC emission with TWTO operating with retarded injection
Figure 8
Figure 9 power.
Variations NOx against brake power.
timing when compared to that of standard injection timing. The increased gas temperature and the cetane number are the reasons for this decrease. The high temperature of the burned gases precludes the condensation of the heaviest hydrocarbons in the sampling line, recommending proper conditions for HC emission analysis [18,7]. Also, the higher oxygen content of the blended fuels compared to that of diesel fuel improves the combustion quality, thus leading to lower HC emission [3]. 4.3. Combustion parameters Fig. 10 shows the variation of cylinder pressure with crank angle for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. From this figure, it is clear that the peak cylinder pressure is slightly decreased with retarded injection timing when compared to that of standard injection timing. The cylinder pressure of a compression ignition engine mainly depends on the amount of fuel accumulated in the delay period and the combustion rate in the initial stages of premixed combustion [32]. The reason for the slight decrease in cylinder pressure with retarded injection timing of TWTO may probably because of reduced evaporation and mixing with air. However, the combustion process is similar, consisting of a phase of premixed combustion following by a phase of diffusion combustion. Premixed combustion phase is controlled by the ignition delay period and the spray envelope of the injected fuel. Fig. 11 shows the variation of heat release rate with crank angle for trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing. The heat release rate in the premixed combustion phase depends on the ignition delay, the mixture formation and the combustion rate in the initial stages of combustion [10]. From this figure, it is clear that the heat release rate of retarded injection timing is lower when operating with standard injection timing. The reason may probably be a shorter ignition delay exhibited during retarded injection timing and its blends cause the air–fuel mixture to accumulate in the combustion chamber. Further, due to entrapment of fuel/air mixture in the combustion chamber during the delay period, more quantity of fuel is burnt in the premixed combustion phase.
Variations of HC against brake power against brake Figure 10
Variations of cylinder pressure against crank angle.
Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008
Influence of injection timing on DI diesel engine characteristics
Figure 11
Variations of heat release rate against crank angle.
5. Conclusion In this experimental study, effects of trans-esterified waste transformer oil (TWTO) with standard and retarded injection timing were investigated. When the injection timing is retarded from 23 bTDC to 20 bTDC, the most important conclusions are outlined as follows: 1. It is observed that the trans-esterified waste transformer oil (TWTO) can be used as a fuel in diesel engines without any problems in terms of engine performance. 2. The properties of trans-esterified waste transformer oil (TWTO) are comparable to conventional diesel fuel. The physical properties such as specific gravity, kinematic viscosity, calorific value, cetane number, flash point and fire point were determined. The results of the FTIR analysis of trans-esterified waste transformer oil showed that it has the characteristics similar to that of conventional diesel fuel. 3. From the experimental investigation, it is observed that TWTO operating with retarded injection timing shows slight improvement in brake thermal efficiency when compared to that of standard injection timing. An increase in thermal efficiency at the expense of higher smoke is achieved for a constant speed diesel engine. 4. Exhaust emissions reduced with TWTO operating with the retarded injection timing when compared to that of standard injection timing. At maximum load conditions, it reduces CO (carbon monoxide), NOx, HC (hydrocarbon) emission by 17.24%, 11.57%, and 10% respectively.
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Please cite this article in press as: S.P.R. Yadav et al., Influence of injection timing on DI diesel engine characteristics fueled with waste transformer oil, Alexandria Eng. J. (2015), http://dx.doi.org/10.1016/j.aej.2015.07.008