Study of performance and emission characteristics of a single cylinder CI engine using diethyl ether and ethanol blends

Journal of the Energy Institute 88 (2015) 1e10

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Journal of the Energy Institute journal homepage: http://www.journals.elsevier.com/journal-of-the-energyinstitute

Study of performance and emission characteristics of a single cylinder CI engine using diethyl ether and ethanol blends Abhishek Paul a, *, Probir Kumar Bose b, RajSekhar Panua a, Durbadal Debroy a a b

Department of Mechanical Engineering, National Institute of Technology, Agartala 799055, India Jadavpur University, Kolkata 700032, India

a r t i c l e i n f o

a b s t r a c t

Article history: Received 24 February 2014 Received in revised form 18 July 2014 Accepted 22 July 2014 Available online 30 July 2014

In this paper, the performance and emission of a single cylinder Diesel engine has been studied by using the blends of Dieselediethyl ether (DEE) and Dieselediethyl ethereethanol. The used blends are D95DEE5 (5% DEE, 95% Diesel by volume), D90DEE10 (10% DEE, 90% Diesel by volume), D90DEE5E5 (5% ethanol, 5% DEE and 90% Diesel by volume), D85DEE5E10 (10% ethanol, 5% DEE and 85% Diesel by volume), D85DEE10E5 (5% ethanol, 10% DEE and 85% Diesel by volume) and D80DEE10E10 (10% ethanol, 10% DEE and 80% Diesel by volume). The thermal efficiency of the engine increased with the blend of 5% DEE blend whereas, decreased with 10% DEE blend. Ethanol addition to DieseleDEE blends increased the efficiency of the engine for both the cases. Use of ethanol along with DEE reduced CO, NOx, hydrocarbon and particulate matters remarkably. Blend D80DEE10E10 showed the best potential of achieving the paradoxical objective of high performance with low emission among the tested fuel samples. © 2014 Energy Institute. Published by Elsevier Ltd. All rights reserved.

Keywords: BSEC Diethyl ether Ethanol NOx reduction Particulate matter

1. Introduction Over the past few decades, there has been a significant growth in awareness regarding the degrading environmental condition. As a result, stringent regulations strongly limited the exhaust emission levels for the internal combustion engines. Diesel engines also have been recognized as the dominating power-train solution in the world market [1]. Diesel engines are also the main power source in the transportation sector. Substantial improvements have been achieved for reducing the fuel consumption and exhaust emissions (Mainly NOx and particulate emissions) of Diesel engines by introducing common rail injection [2e4], exhaust gas recirculation (EGR) [5,6], exhaust gas after treatment [7,8], turbo charging [9] etc. Further, as the global petroleum reserves are depleting at an alarming rate, researchers are compelled to focus their research towards finding alternative fuel sources that can gradually replace the fossil fuel based energy sector. Fuels such as Methane [10e16] or Hydrogen [17e22] in CI engine has been well researched to produce better performance characteristics in terms of higher brake thermal efficiency and lower fuel consumption with reduced exhaust emissions. However, these non-conventional fuels are also found to increase emissions of NOx. Use of suitable additives could be useful for achieving both high performance and low exhaust emission. Fuel additives with a high cetane number can significantly improve the performance of a CI engine by improving the combustion of the charge inside the cylinder [23]. Additionally, additives with high-oxygenated content can also have the additional effect of reducing the emission of hydrocarbon, CO and smoke of a CI engine. Chemical compounds such as dimethyl ether, diethyl ether etc. can offer such benefits. Dimethyl ether (DME) is a short carbon chain of ether (CH3OCH3) [1] that has been experimented for improving ignition characteristics of the engine due to its high cetane number [1,24]. Along with that, it is also found to reduce the emissions of smoke and NOx [25]. However, the DME is gaseous by nature and requires major modification in engine design to incorporate it in the combustion process. Diethyl ether (DEE), on the other hand is less volatile than DME and has a very high cetane number (more than 125) [26]. DEE also has a latent heat of vaporization of 356 kJ/kg [25], for which it can also provide charge cooling, necessary for reduction in NOx emissions [12]. DEE also has an oxygen content of 21.6% [24], which can significantly improve performance of the engine and reduce CO and HC emissions. Again,

* Corresponding author. Tel.: þ91 9612878658. E-mail address: [email protected] (A. Paul). http://dx.doi.org/10.1016/j.joei.2014.07.001 1743-9671/© 2014 Energy Institute. Published by Elsevier Ltd. All rights reserved.

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Nomenclature DEE diethyl ether DME dimethyl ether BSEC brake specific energy consumption DI direct injection CI compression ignition hbth brake thermal efficiency CO/CO2 carbon monoxide/carbon dioxide NOx oxides of nitrogen HC hydrocarbon

as per Equation (1), 1 mol of DEE produces only 4 mol of CO2, whereas, 1 mol of Diesel produces 12 mol of CO2 (Equation (2)). Hence, there is always a possibility of CO2 emission reduction when DEE is used as an additive. C2 H5 OC2 H5 þ 6O2 ¼ 4CO2 þ 5H2 O

(1)

4C12 H23 þ 71O2 ¼ 48CO2 þ 46H2 O

(2)

Despite of these favorable properties of DEE as fuel for CI engine, there has been only a handful number of works done in this field. Subramanian and Ramesh [24] carried out experiments with 5%, 10% and 15% (by weight) of DEE, blended with Diesel on a single cylinder Diesel engine. They observed significant increase in brake thermal efficiency of the engine with 10% DEE in Diesel. The blend didn't produce any significant increase in NOx emission. It was also found that this blend decreased the smoke and carbon monoxide (CO) emissions drastically at all load conditions. Mohanan and Kapilan [26] studied the performance and emission characteristics of a 4 stroke single cylinder CI engine using Diesel fuel blended with 5%, 10%, 15%, 20% and 25% DEE (by vol). They found that 5% DEE blended with Diesel reduces the BSEC with a simultaneous decrease in CO and smoke emission. The blend was also found to increase the brake thermal efficiency of the engine in all load conditions. However, it was also seen that a DEE concentration of 10% and above produced a detrimental effect on performance and emission of the engine as it reduced brake thermal efficiency and increased smoke emission. Hence the authors concluded that a higher percentage of DEE may not be suitable for CI engine application. In a different study, Kapilan et al. [27] examined the effect of DEE by increasing its percentage from 1 to 10% with the increment of 1%. This study also concluded with slight improvement in brake thermal efficiency and reduction in CO, hydrocarbon and smoke emissions by 5% DEE in Diesel. Increasing DEE percentage beyond 5% again showed a decrease in brake thermal efficiency and an increase in CO and hydrocarbon emissions. Iranmanesh et al. [25] conducted tests on a single cylinder DI engine with blends of Karanja oil methyl ester and 5, 10, 15 and 20% DEE. The results obtained from this study showed significant reduction in NOx and smoke emission with increasing DEE percentage. However, a decrease of brake thermal efficiency and increase of CO and hydrocarbon emission were also observed in this study. Anand and Mahalakshmi [28] studied the NOx and smoke reduction potential of different DieseleDEE blends by varying the DEE percentage up to 30% by vol. in steps of 10% (By vol.) with exhaust gas recirculation. It was found from the study that 20% (By vol.) DEEeDiesel blend resulted in the optimum performance and emission characteristics. From the above, it is made obvious that DEE concentration above 5% (by vol.) generally causes a decrease in brake thermal efficiency and increases BSEC and smoke emission of the engine. Hence a second additive may be employed to improve the performance and emission of the engine. Further, a second bio based additive will also help in substituting higher percentage of fossil fuel. A good solution might be ethanol since it is a bio based additive with high oxygenated content. Ethanol is one of the most widely researched fuel additive for it's spark ignition (SI) as well as compression emission (CI) engine applications. Ethanol has a high-octane number, which makes is suitable for SI engine application. It also has an oxygen content of 34% and a latent heat of vaporization of 840 kJ/kg [29]. As a result, it also has potential for CI engine application, as it can assist in better combustion of the charge and reduce the thermal NOx formation of the engine by charge cooling. Due to this, a lot of work has been done with ethanol in CI engines. Irshad Ahmed [30] studied the effect of ethanoleDiesel blends on the performance and emission of a CI engine. It was found in this study that the blends produced a 41% reduction in particulate emission, 27% reduction in CO, and 5% reduction in NOx emissions. Hardenberg and Schaefer [31] studied the effect of ethanol on a CI engine. It was also found from their study that, ethanol produced lower smoke and NOx emissions. Li et al. [32] studied the effect of ethanol on a CI engine combustion and found that simultaneous reduction in smoke, NOx and CO emissions is possible with 15% ethanol blended with Diesel. Some previous works conducted by the same researchers [10,33] also concluded with similar results of reduced emission and marginal increase in performance of the engine using ethanol as an additive. Study of literature in this field thus reveals the fact that there is obviously a scope of investigating the potential of utilizing DEE and ethanol together with Diesel. In the present study, the performance and emission characteristics of a CI engine have been investigated using different blends of DieseleDEE and ethanol. The motivation behind this study is to improve the combustion quality of the charge by using a high cetane additive DEE and a high-oxygenated additive ethanol. Side by side, the cooling effect of ethanol will also be able to reduce the NOx emissions of the engine. 2. Equipment and experiments 2.1. Experimental fuels The commercial Diesel fuel used in the tests was obtained locally. Analysis-grade anhydrous diethyl ether of 99.8% purity and analysis grade anhydrous ethanol of 99.9% purity were used in this study. Table 1 shows the properties of these base fuels. In the study, 6 blends have

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Table 1 Properties of base fuels. Properties

Diesel

Diethyl ether (DEE)

Ethanol

Calorific value (kJ/kg) Density (gm/cm3) Cetane Stoichiometric air fuel ratio Latent heat of evaporation (kJ/kg) Oxygen content (%) Self ignition temperature ( C)

43,000 0.863 49 14.76 250 0 250

33,900 0.713 125 11.2 350 21.6 380

26,950 0.789 8 8.95 840 34.8 420

been tested in comparison with baseline Diesel. It was found that DEE has no miscibility issue when it is mixed with Diesel. In a previous study [10] by the same research group, it was found that maximum 10% ethanol (by volume) can be mixed with Diesel without using any cosolvent or emulsifying agent. Hence, the maximum concentration of ethanol and DEE is 10% (by volume). At first, 5% and 10% DEE (by vol.) was mixed with 95% and 90% Diesel respectably to produce D95DEE5 and D90DEE10 blends. In the next phase, 5% and 10% of ethanol was added to these DieseleDEE blends by reducing Diesel percentage. The blends prepared in this process are D90DEE5E5 (90% Diesel, 5% DEE and 5% ethanol), D85DEE5E10 (85% Diesel, 5% DEE and 10% ethanol), D85DEE10E5 (85% Diesel, 10% DEE and 5% ethanol) and D80DEE10E10 (80% Diesel, 10% DEE and 10% ethanol). DEE and ethanol showed complete miscibility in Diesel for all of these blends and the blends were found to be stable. The experimentation was conducted at an ambient temperature of 28e29  C, which is lower than the boiling point of ethanol and DEE [32,41]. Hence, all of these blends were tested in the existing engine to find the effect of the set of additives. These blends are shown in Fig. 1 and their main properties are shown in Table 2. 2.2. Experimental setup and procedure The engine tests were conducted on a Kirloskar TV 1 single cylinder, naturally aspirated, water-cooled CI engine that has been modified to provide a variable compression ratio and a maximum output of 3.6 kW at 1500 rpm. The engine was synchronized with an eddy current dynamometer (Make:Saj test plant Pvt. Ltd, Model-AG10) for loading purpose. A crank angle sensor (Make-Kubler-Germany, Model 8.3700.1321.0360) was used to measure the engine rpm. It was calibrated in terms of 1 degree of interval. The fuel flow into the engine was measured by means of differential pressure transducer (Model-EJA110A-DMS5A-92NN, make-Yokogawa) and a fuel burette of 12.4 mm diameter by measuring the difference in fluid pressure while the fluid flows through the burette. A Testo 350 gas analyzer was used to measure the gaseous emission from the engine. The emission of particulate matters was measured by AVL 415S smoke meter .The detailed specification of the experimental setup is given in Table 3 and the same is shown in Fig. 2. The experiments were carried out at load equivalents of 0.6 kW, 1.2 kW, 1.8 kW, 2.4 kW, 3.0 kW and 3.6 kW. Prior to testing the fuel blends, the engine was tested with Diesel, which provided the base dataset to compare the variation of different performance and emission parameters. Before testing with a new blend sample, the engine worked for sufficient time to consume the remaining fuel from the previous experiment. Special care was taken to keep the constant speed of the engine (±10 rpm) during data acquisition for each case of engine operation at different loads. The authenticity of the reading increased by taking 6 consecutive readings at the same condition and averaging them. The whole experimentation was done at an ambient temperature of 28e29  C and at a relative humidity of 70%. 2.3. Measured data uncertainty analysis All measurements of the physical quantities include some degree of uncertainty owing to their different sources, namely the instrumentation used, its calibration, observation accuracy and the experimentation methodology [10,33]. Hence, it is of prime importance to establish an uncertainty analysis with respect to the repeatability and precision of the experimentation. The combined uncertainty analysis

Fig. 1. The tested fuel blends.

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Table 2 Composition of the test fuels and main properties. Blend

D95DEE5

D90DEE10

D90DEE5E5

D85DEE10E5

D85DEE5E10

D80DEE10E10

% of Diesel % of DEE % of ethanol Calorific value (kJ/kg) Cetane number Density (gm/cm3) Stoichiometric air fuel ratio

95 5 0 42,620 53.75 0.855 14.6116493

90 10 0 42,234 57.5 0.848 14.4606745

90 5 5 41,875.807 51.65 0.8518 14.341922

85 10 5 41,481.579 55.4 0.8443 14.18789

85 5 10 40,832.9 55.8 0.8481 14.069842

80 10 10 40,721.65715 53.3 0.8406 13.91270402

for the performance parameters has been carried out on the basis of the root mean square method, where the total uncertainty U of a quantity Q has been estimated, depending on the independent variables x1, x2,…, xn (i.e., Q ¼ f[x1,x2,…,xn]) having individual errors Dx1, Dx2,…,Dxn as given by Equation (3) [10]. The percentages of uncertainty of the performance parameters are shown in Table 4.

sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2  2 2   vU vU vU DU ¼ DX1 þ DX2 þ…þ DXn vX1 vX2 vXn

(3)

Table 5 shows the accuracy of the measurements of TESTO 350 5 gas analyzer and AVL 415S smoke meter used in this study. 3. Results and discussion The variation of different performance and emission parameters for different blends are compared with reference to brake power of the engine. 3.1. Performance analysis 3.1.1. Brake thermal efficiency Fig. 3 shows the variation of brake thermal efficiency (hbth) with load for different fuel blends. It can be seen from the graph that 5% (by vol.) DEE in Diesel improved the hbth of the engine over the entire loading range. This increase in hbth may be attributed to the higher cetane number of the DEE, which allowed ignition of the charge at an earlier crank angle. As a result, the charge got more time to burn properly and release higher amount of its chemical energy. Side by side 21.6% oxygen content of DEE also helped in proper combustion of the charge. It was again observed that the hbth of the engine marginally decreased with 10% (by vol.) DEE in Diesel. The blend D90DEE10 has a higher cetane number than D95DEE5 due to increased DEE percentage. Due to the higher cetane number, D90DEE10 blend has a shorter ignition delay. A reduced ignition delay implies a lower time for mixing the fuel with the air, inducing higher differences in local airefuel ratios, reducing the combustion efficiency. This hypothesis is confirmed by the higher production of CO, as reported in the Section 3.2. Mohanan et al. [26] also obtained similar results. Addition of ethanol to these blends showed encouraging trends as the hbth of the engine was found to increase with ethanol addition. It was found that 5% ethanol addition with 5% DEE (D90DEE5E5 blend), increased the hbth at medium and high load conditions. At full load condition, D90DEE5E5 blend produced 4.34% higher hbth as compared to D95DEE5. 10% Ethanol with 5% DEE (D85DEE5E10 blend) further increased the hbth of the engine by 4.46% with respect to D95DEE5 blend at full load. Ethanol addition also produced significant increase in hbth for blends with 10% DEE. 5% Ethanol with 10% DEE (D85DEE10E5 blend) produced an increase of 7.35% with respect to Diesel and 8.23% with respect to D90DEE10 at full load condition. The maximum increase in hbth among all the tested fuel samples was observed with D80DEE10E10 blend, where hbth was increased by 15.95% with respect to Diesel and 18.46% with respect to D90DEE10 at load equivalent of 1.8 kW. These consistent increases in hbth with ethanol addition may be attributed to the increased oxygen content of the blend. Side by side, ethanol being a low cetane fuel brought down the cetane number of the blends by a small amount. This brings the ignition delay close to 13 , which is the standard ignition delay period for the engine. As a result of that, the charge ignited at appropriate crank angle that resulted in better performance. 3.1.2. Brake specific energy consumption Fig. 4 shows the BSEC of the engine for different fuel blends. It can be seen from the graph that the energy consumption of the engine decreases with D95DEE5 blend with a maximum decrease of 3.59% at full load condition. This may be due to the higher cetane number of DEE that allows the blend to ignite earlier than Diesel. Along with that, DEE also has an oxygen content of 21.6%, which allow better combustion of the charge. As a result, the engine required less amount of energy, which subsequently reduced the BSEC. It is also seen that

Table 3 Specifications of test engine. Engine type Bore and stroke Max. power CR range Swept volume Combustion system Fuel injection pressure

Kirloskar, Model TV-1, 4 stroke water cooled, VCR engine 87.5 mm and 110 mm 3.6 kW 12e18 661 cc Direct injection 205 bar

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Fig. 2. Complete experimental setup.

the BSEC increased with D90DEE10 blend with a maximum increase of 10.3% at low load, equivalent of 0.6 kW. It was also due to the effect of higher cetane number of the blend that caused small ignition delay. Hence, the charge got less time to mix with air. This heterogeneous mixture reduced the combustibility and increased the energy requirement. It can also be seen that D90DEE5E5 blend with 5% ethanol and D85DEE5E10 with 10% ethanol, increased the BSEC at low load. As the load increased, BSEC of the engine also decreased. This is because, at low load, least amount of fuel was injected into the combustion chamber, which resulted in lower in-cylinder pressure and temperature. As a result, the ethanol part of the blend may not reach its ignition temperature and it may have refrained from burning. As the load increased, higher amount of fuel was injected into the cylinder and higher incylinder pressure and temperature were achieved. At this elevated temperature, ethanol reached its ignition temperature and participated in combustion to release energy. Due to this, the BSEC gradually decreased with increasing load. Ethanol addition with 10% DEE was found to improve the BSEC of the engine significantly. This decrease in BSEC may have been caused by higher cetane number of DEE, for which burning of the charge initiated at an earlier crank angle and attained complete combustion, thus releasing higher amount of energy. This also increased the in-cylinder pressure and temperature, which simultaneously helped ethanol to burn and release energy. This improvement in BSEC was most prominent with D80DEE10E10 blend with a maximum decrease of 10.06% with respect to Diesel and 13.49% with respect to D90DEE10 at full load condition. 3.2. Emission analysis 3.2.1. CO emission Fig. 5 shows the CO emission for different fuel blends. It can be seen from the figure that at low load condition, CO emission from the engine increased with D95DEE5 blend. However, with the inclusion of ethanol, it again decreased significantly. This decrease may be due to the lower C/O ratio of DEE and ethanol. Due to this, a few carbon radicals were participating in combustion. Along with that, the oxygen released by the decomposition of the two additives also helped in oxidation of the carbon to CO2. It was also observed that CO emission increased significantly with D90DEE10 blend having 10% DEE. Adding ethanol with 10% DEE was found to improve CO emission significantly. It is a well-known fact that CO oxidizes to produce CO2and the reactions are shown below [34]. CO þ O2 / CO2 þ Oð3Þ O þ OH / OH þ OH

(4)

CO þ OH / CO2 þ H

(5)

H þ O2 / OH þ O

(6)

Table 4 Total percentage of uncertainty of the computed performance parameters. Computed performance parameter

Measured variables

Instrument involved in measurement

% Uncertainty of the measuring instrument [10]

BP (brake power)

Load, RPM

Fuel flow

SFC (liquid fuel)

Load sensor, Load indicator, Speed measuring unit Fuel measuring unit, Fuel flow transmitter

0.2, 0.1, 1.0 0.065, 1.5

Calculation qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð0:2Þ2 þ ð0:1Þ2 þ ð1:0Þ2 qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð0:065Þ2 þ ð1:5Þ2

Total % uncertainty of the computed parameters 1.02

1.501

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A. Paul et al. / Journal of the Energy Institute 88 (2015) 1e10 Table 5 Accuracy of the emission measuring. Parameter

Range

Resolution

O2 CO NO NO2 CO2 HC Particulate matters

0e25 vol. % 0e10,000 ppm 0e4000 ppm 0e500 ppm 0e50 vol. % 100e40,000 ppm 0.03e123 kg/h

0.01 vol. % 1 ppm 1 ppm 0.1 ppm 0.01 vol. % 10 ppm Volume/mass  0.1e0.2%

Equations (3) and (5) are the main oxidation reactions, whereas Equations (4) and (6) are the chain branching reactions. The first reaction shown in Equation (3) is the initialization reaction, but it is slow. The second reaction shown in Equation (5) is the main oxidation step [34]. Hence, it is evident that the increase in the ‘H’ molecule and the ‘OH’ radical is conducive to a reduction in the CO emission. During combustion, thermal decomposition of ethanol (C2H5OH) molecules produced ‘OH’ radicals, which helped in further conversation of CO to CO2. 3.2.2. NOx emission Fig. 6 shows the variation of NOx emission from the engine. It can be seen from the graph that NOx emission decreased with D95DEE5 blend at low load, but increased with medium and high load conditions. At lower load conditions, the energy requirement of the engine was relatively lower. Because of this, less amount of fuel was injected and burned in the combustion chamber, producing lower in-cylinder temperature and pressure. Since NOx formation is prominently dependent on high in-cylinder temperature, so reduced NOx emission was observed for the blend D95DEE5 at low loads. However, at the higher load conditions, higher amount of fuel was injected and burned, producing higher in-cylinder temperature. D90DEE10 blend also followed the same trend of low NOx emission at low load and increased NOx emission at high load conditions. However, it was seen that the NOx emission for D90DEE10 was significantly lower than D95DEE5. It may be due to the reduced ignition delay that truncated the fueleair mixing time and deteriorated the combustion condition. This reduced combustion of the charge produced lower cylinder heat generation that resulted lower NOx emission. It is also seen that, the NOx emission was significantly reduced with the ethanol addition to the DieseleDEE blends. D90DEE5E5 blend with 5% DEE and 5% ethanol reduced the NOx emission by 14.28% at full load condition as compared to baseline Diesel. This reduction in NOx emission may be attributed to the cooling effect of ethanol [33,35]. This effect was more prominent for D85DEE5E10 blend, where it produced a maximum reduction of 20.76% at medium load condition (1.8 kW BP). This was also a reduction of 23.59% with respect to D95DEE5 blend. For D85DEE10E5 and D80DEE10E10 blends, a prominent reduction in NOx emission was observed. D85DEE10E5 blend with 10% DEE and 5% ethanol produced a maximum decrease of 25.95% at 2.4 kW BP, whereas D80DEE10E10 with 10% DEE and 10% ethanol produced a reduction of 27.58% at the same load condition. These reductions may have been caused by charge cooling due to ethanol vaporization. Similar trends of NOx emission reduction with increase in ethanol content is also observed in different studies [10,36]. 3.2.3. Hydrocarbon emission Fig. 7 shows the variation in hydrocarbon (HC) emission for different fuel blends. It can be seen from the graph that all fuel blend produced lower hydrocarbon emission than Diesel for medium and high load conditions. At these load conditions, DieseleDEE blends (D95DEE5 and D90DEE10) produced lower hydrocarbon emission than Diesel. This reduction in HC emission may have happened because of the improved combustion condition due to the release of molecular oxygen of DEE. In comparison to baseline Diesel, D95DEE5 blend

Fig. 3. Variation of hbth with blends.

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Fig. 4. Variation of BSEC with blends.

reduced the HC emissions by 31.34% at 1.20 kW, 36.35% at 1.80 kW, 40.56% at 2.40 kW, 33.92% at 3.00 kW and 30.66% at3.60 kW respectably, whereas D90DEE10 blend reduced the HC emission by 52.074%, 57.343%, 60.829%, 52.988%, and 49.228% at same load conditions. This reduction is also an indication that the increasing oxygenated content of fuel helps in reduction of HC emission. Addition of ethanol to these blends further reduced the HC emission. It was found that 5 and 10% ethanol addition to DieseleDEE blends reduced the HC emission in a significant manner.D90DEE5E5 and D85DEE5E10 blends produce 90.13% and 80.481% less hydrocarbon than baseline Diesel at 2.4 kW, whereas D85DEE10E5 and D80DEE10E10 blends produces a maximum reduction of 84.33% and 91.12% at 3 kW brake power. This decreases were due to better combustion of the charge, which was supported by the oxygen, liberated from decomposition of ethanol and DEE. Hence, major portion of the oxidizer was utilized for oxidizing the fuel hydrocarbon. 3.2.4. Particulate matter emission Fig. 8 shows the PM emission from the engine for different tested blends. It can be seen from the graph that PM emission from the engine had drastically reduced with all the blends at medium and high load conditions. At low loads, DieseleDEE blends showed reduced or similar PM emission rates as compared to Diesel. This may be due to lower in-cylinder temperature and pressure that reduced the quality of combustion. At medium and high load conditions, the PM emission from the engine decreased for all the tested fuel blends. The high cetane number and 21.6% oxygen content of DEE was advantageous to the combustion as the former reduced the ignition delay and the later helped in better combustion of the charge. As a result, the carbon and soot elements burned and reduced the PM emission. This was reflected in the drastic reduction in PM emission with DieseleDEE blends. It was also found that addition of ethanol further reduced the PM emission. This was because combustion of ethanol liberates the ‘OH’ radicals into the combustion chamber. These ‘OH’ radicals are instrumental in soot

Fig. 5. Variation of CO emission with blends.

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Fig. 6. Variation of NOx emission with blends.

decomposition in diffusion flame [37e39]. Hence, with the increase of ethanol content in fuel, the PM emission reduced invariably. Similar decrease in PM emission with increasing ethanol content was also observed previously [32e40].

4. Conclusion An extended experimental study was conducted to evaluate and compare the effect of Dieselediethyl ether and Dieselediethyl ethereethanol blends on performance and emission of a 4 stroke single cylinder CI test engine. The tested fuel blends are consisting of two blends of Dieselediethyl ether with blend ratios of 95/5 (D95DEE5) and 90/10 (D90DEE10) and 4 blends of Dieselediethyl ethereethanol with blend ratios of 90/5/5 (D90DEE5E5), 85/5/10 (D85DEE5E10), 85/10/5 (D85DEE10E5), and 80/10/10 (D80DEE10E10). The series of tests are conducted using each of the above fuel blends with an engine speed of 1500 rpm at six different loads. The major findings of this experimental study is summarize below. The brake thermal efficiency of the engine increased with 5% DEE addition but decreased with 10% concentration. Although 5% concentration of DEE in Diesel was found to decrease the BSEC but any further increase in DEE percentage increased the BSEC of the engine. The particulate emission from the engine was found to decrease with increasing DEE percentage of fuel. The D95DEE5 blend with 5% DEE increased the NOx emission from the engine. However, further increase in DEE percentage (10%) produced lower NOx emission than D95DEE5 blend. The unburned hydrocarbons (HC) emissions also decreased with the use of the DEE/Diesel fuel blends with respect to those of the neat Diesel fuel and as percentage of DEE is increased, the reduction in HC emission was found to be more prominent. The CO emission from the engine decreased with D95DEE5 but increased a bit with D90DEE10 blend.

Fig. 7. Variation of HC emission with blends.

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Fig. 8. Variation of PM emission with blends.

Addition of ethanol to the DieseleDEE blends further increased the brake thermal efficiency and BSEC of the engine. Among all the blends tested in this work, D80DEE10E10 blend with 10% DEE and 10% ethanol is found to be the best as it increased the brake thermal efficiency by 15.94% and reduces BSEC by 14.26% as compared to Diesel at a load equivalent of 1.8 kW. It was also observed that particulate emission had an inverse relation with ethanol percentage as the lowest emission of particulate matter was observed with D80DEE10E10 blend, which was a reduction of 91% as compared to Diesel at full load condition. Ethanol addition also reduced the NOx emission from the engine. The blends D80DEE10E10 produced the lowest NOx emission consistently in almost all load conditions. The blend also produced the lowest CO emission among all the blends with a decrease of 53.14% as compared to Diesel at full load condition. The experimental work thus reveals the prospect of using multiple additives to Diesel for improving its performance and emission characteristics. Further, the study also shows that addition of 10% ethanol to a blend of 80% Diesel and 10% diethyl ether can produce better results than DieseleDiethyl ether blends.

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