Effect of injection timing on performance, combustion and emission characteristics of diesel engine using mahua oil methyl ester as fuel

Journal SOLAIMUTHU of Scientific && GOVINDARAJAN: Industrial Research EFFECT OF INJECTION TIMING ON PERFORMANCE OF DIESEL ENGINE FUELED WITH MAHUA BIODIESEL Vol. 71, January 2012, pp. 69-74 69 Effect of injection timing on performance, combustion and emission characteristics of diesel engine using mahua oil methyl ester as fuel Chandrakasan Solaimuthu 1 *and Palanisamy Govindarajan 2 1 Department of Mechanical Engineering, Paavai Engineering College, Namakkal 637 018, India 2 Sona College of Technology, Salem 636 005, India Received 03 August 2011; revised 24 October 2011; accepted 25 October 2011 This study presents effect of injection timing on performance, combustion and emission characteristics of mahua biodiesel (Madhuca indica) and its blends with pure diesel on a 4 stroke tangentially vertical single cylinder (TV 1) direct injection diesel engine. Standard injection pressure (220 bar) is maintained throughout the experiment. Injection timings (22, 23 and 24 btdc) were considered under steady state conditions at maximum load condition of the engine. At injection timing of 22 btdc, blend B25 (25% mahua biodiesel and 75% pure diesel, by vol) gave optimum performance, which is very close to pure diesel. Thus B25 fuel can be effectively used in a diesel engine as an alternative fuel without any modification in the engine. Diesel (25%) thus saved will greatly help the interests of railways in meeting the demand for fuel, as diesel trains are operated at maximum load condition. Keywords: Diesel, Engine performance, Injection pressure, Injection timing, Mahua oil methyl ester Introduction Non-edible vegetable oils are preferred for engine applications in India. Clark et al 1 concluded that soybean biodiesel gives higher specific fuel consumption and lower emissions except NO x than diesel. Kyle et al 2 found that as compared to diesel fuel, soybean methyl ester gives lower emissions of CO, HC, smoke density and NO x. Puhan et al 3 observed significant improvement in engine performance and emission of DI engine with mahua (Madhuca indica) oil methyl ester (MOME), mahua oil ethyl ester, mahua oil butyl ester and diesel fuel. Subramanian et al 4 concluded that 10% diesel, 80% of pongamia oil methyl ester and 10% ethanol gives better performance of diesel engine without any modification. Puhan et al 5 concluded that MOME gives better results as compared with ethyl ester of mahua oil. Puhan & Nagarajan 6 found that MOME gives lowest NOx as compared with diesel fuel. Puhan et al 7 found that emissions impact of biodiesel (B100) is lower than that of diesel (B0). Puhan et al 8 found that MOME (B100) burn more efficiently than diesel (B0) and emissions of *Author for correspondence E-mail: solai9999@gmail.com B100 is lower than that of B0. Saravanan et al 9 observed that pure MOME (B100) gives lower emissions than pure diesel (B0). Ahmed et al concluded that production of hemp oil methyl ester is a promising alternative fuel for diesel engine. Kapilan et al 11 observed that B100 can be a substitute fuel for diesel with advanced injection timing for better performance and lower emissions. Kapilan & Reddy 12 concluded that MOME gives lower emissions than diesel fuel. Kapilan & Reddy 13 observed that MOME can be used as an alternative fuel in dual fuel engine with pilot fuel of 5 mg per cycle and injection pressure of 200 bar. Padhi et al 14 reported biodiesel preparation and discussed its percentage of acid catalyst and esterified and transesterified oils for constant methanol and oil ratio of the fuel. Raheman & Ghadge 15 concluded that biodiesel 20% by volume with 80% diesel formed an optimum mixture for engine parameters. Raheman & Ghadge 16 investigated a technique to produce MOME having high free fatty acids (FFA). Sundarraj et al 17 concluded that 70% diesel, 20% ethanol and 10% dioxane blend gives better performance and lower emissions on diesel engines with and without thermal barrier coating. Sundarraj et al 18 concluded that 60% diesel, 30% ethanol and 10% dioxane by volume gives better performance and lower emissions without

70 J SCI IND RES VOL 71 JANUARY 2012 any engine modification. Godiganur et al 19 observed significant improvement in engine performance and emission parameters with MOME and its blends with diesel. Godiganur et al 20 reported that MOME (B20) gives maximum brake thermal efficiency and lower brake specific fuel consumption of their engine set up. This study analyses injection timings (IT) of 22, 23 and 24 btdc and injection pressure of 220 bar at maximum load of diesel engine with MOME (B0, B25, B50, B75 and B100) as fuel. Experimental Section Experimental Setup and Procedure Experiments were conducted on a 4 stroke, kirloskar, TV 1 vertical single cylinder direct injection diesel engine (Fig. 1) developing power output of 5.2 kw at 1500 rpm connected with water cooled eddy current dynamometer, and having following specifications: bore x stroke, 87.5 mm x 110 mm; compression ratio, 17.5: 1; IT, 22, 23 (standard) and 24 btdc; and standard injection pressure, 220 bar at maximum load. AVL 444 digital gas analyzer was used for measurement of exhaust emission of hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO 2 ), oxygen (O 2 ) and nitrogen oxides (NO x ). Smoke level was measured using standard AVL 437 smoke meter. All experimental readings were taken under steady state conditions of the engine. Thermo-physical Properties of Mahua Biodiesel (MOME) and its Diesel Blends Using standard test facilities, thermo physical properties of mahua biodiesel and its blend in various volumetric proportions with fossil diesel were evaluated. Mahua oil has lower calorific value but higher density (Table 1), indicating that calorific value of mahua oil on a volumetric basis approaches the volumetric calorific value of diesel fuel. In case of mahua oil, cetane number increases along with flash and fire point compared to neat diesel. Ratios of blends were as follows (Table 2): B0 (neat diesel), B25 (25% mahua biodiesel and 75% diesel by vol), B50 (50% mahua biodiesel and 50% diesel by vol), B75 (75% mahua biodiesel and 25% diesel by vol) and B100 (neat mahua biodiesel). Specific gravity, acidity, kinematic viscosity, flash point, fire point and cloud point increases with increase in biodiesel content. Significant increase in fire point shows that volatility of mixture with increased biodiesel content will decrease. Gross calorific value decreases as biodiesel content in Fig. 1 Schematic of engine setup Table 1 Properties of mahua biodiesel and its diesel blends Properties B0 B25 B50 B75 B100 Gross calorific value, MJ/kg 45.59 43.98 43.27 42.52 41.82 Kinematic viscosity 40ºC, cst 2.6 3.49 4.17 4.98 6.04 Flash Point, ºC 65 71 78 112 170 Fire Point, ºC 70 79 88 123 183 Cloud Point, ºC -15 4 8 11 13 Specific gravity 0.82 0.83 0.85 0.87 0.88 Cetane number 46 51.6 51.7 51.8 52.4 Acidity 0.065 0.067 0.070 0.083 0.26 mixture increases, due to oxygen in fuel and it requires more fuel to be burnt for a given heat release. Results and Discussion Brake Thermal Efficiency (BTE) For B0 and B25 fuel, 22 btdc of IT gives highest BTE (%) as compared to all other ITs (Fig. 2). Same trend is followed for B50, B75 and B100. As compared with standard IT of 23 btdc at maximum load, BTE (%) for 22 btdc of IT for fuels was found to be: B0, 1.55; B25, 1.52; B50, 0.71; B75, 0.035; and B100, 0.88%. Among all blends, B0 and B25 give almost same and higher BTE (1.55%) at maximum load as compared to all blends of fuel. BTE depends on heating value and specific gravity. Combination of heating value and mass flow rate indicates energy input to engine, which in case of B50, B75 and B100 are more compared to neat diesel, may be due to lower BTE for all blends of fuel as compared with B0 and B25. The results are quite similar to reported study 7.

SOLAIMUTHU & GOVINDARAJAN: EFFECT OF INJECTION TIMING ON PERFORMANCE OF DIESEL ENGINE FUELED WITH MAHUA BIODIESEL 71 BTE, % SFC, kg/kwh Fig. 2 Blend ratio vs brake thermal efficiency (BTE) Fig. 3 Blend ratio vs specific fuel consumption(sfc) Heat release rate, kj/m 3 deg Maximum cylinder pressure, bar Fig. 4 Blend ratio vs heat release rate Fig. 5 Blend ratio vs maximum cylinder pressure Specific Fuel Consumption (SFC) For B0 and B25 fuel, 22 btdc of IT gives lowest SFC (kg/kwh) as compared to all ITs for all blends (Fig. 3). As compared with standard IT (23 btdc), reduction% in SFC for IT of 22 btdc for fuels was found to be: B0, 0.36; B25, 0.35; B50, 0.27; B75, 0.33; and B100, 0.33%. B0 gave maximum reduction% of SFC (0.36%), and also B25 gave almost same value as that of B0. Therefore, for 22 btdc, B0 and B25 give better results in SFC as compared with all blends, due to higher viscosity and lower calorific value and more fuel quantity at maximum load, which causes better utilisation of air leading to better combustion. The results are quite similar to reported study 7. Heat Release Rate For B0 and B25, 22 btdc of IT gives highest heat release rate (kj/m 3 deg) as compared to all ITs (Fig. 4). As compared with standard IT (23 btdc), increase% of heat release rate for IT of 22 btdc for fuels was found as follows: B0, 29.23; B25, 29.13; B50, 15.74; B75, 11.48; and B100, 12.50%. Among all blends, B0 and B25 give almost same and highest heat release rate (29%), may be due to lower calorific value of B50, B75 and B100 as compared with B0, and lower heat release rate for blends. Lower IT gives better combustion. The results are quite similar to reported study 2. Maximum Cylinder Pressure At maximum load condition, 22 btdc of IT gives highest maximum cylinder pressure (bar) as compared to all other ITs for all blends (Fig. 5). As compared with standard IT (23 btdc), increase% of maximum cylinder pressure for IT of 22 btdc for fuels was found as follows: B0, 1.47; B25, 1.45; B50, 1.40; B75, 1.18; and B100, 1.09%. Excepting B0, B25 has got higher caloric value as compared to other blends. Reduction% of calorific value for B25 is 3.6% as compared with B0, may be due to slight reduction in cylinder pressure for B25 as compare to B0 2. Exhaust Gas Temperature (EGT) At maximum load condition, 22 btdc of IT gives lowest EGT in case of B0 and B25 as compared to all

72 J SCI IND RES VOL 71 JANUARY 2012 EGT, o C SD, HSU Fig. 6 Blend ratio vs Exhaust gas temperature (EGT) Fig. 7 Blend ratio vs smoke density (SD) other ITs and all blends (Fig. 6). As compared with standard IT of 23 btdc, reduction% of EGT for IT of 22 btdc for fuels was found as follows: B0, 1.40; B25, 1.37; B50, 0.84; B75, 0.56; and B100, 0.55%. Among all blends, B0 gives lowest EGT, and B25 is also closer to that of B0. There is an increasing trend of EGT as increase in blend ratio of biodiesel with diesel fuel, could be due to increased heat losses of higher blends, which is also evident from their lower BTEs as compared with neat diesel (B0). Similar finding was obtained by other study 15. Smoke Density (SD) IT (22 btdc) gives lowest SD (HSU) as compared to all other ITs (Fig. 7). B25 (62 HSU) emits lower smoke compared to B0, may be due to the chemistry of fuel blend, which may promise conducive atmosphere for lower SD for B25 compared to B0. Specific gravity change for B25 compared to B0 is quite small (0.82-0.83) and fire point increase is less than 10 C (Table 1). Further there is good increase (46.0-51.6) in cetane number between B0 and B25. As compared with standard IT of 23 btdc, reduction% of SD for IT of 22 btdc for fuels was found as follows: B0, 2.66; B25, 2.82; B50, 0.54; B75, 0.80; and B100, 1.69%. Among all blends, B25 gives 2.82% reduction% of SD at maximum load. As blends of fuel ratio increases, SD also increases, may be due to more fuel is injected into engine to take care of the load of blends of fuel. As engine is running at constant speed of 1500 rpm, there is less time for complete combustion, which can cause an increase in SD. Carbon monoxide (CO) IT (22 btdc) gives lowest CO as compared to all other ITs for all blends of fuel (Fig. 8a). As compared with standard IT (23 btdc), reduction% in CO for IT of 22 btdc for fuels was found as follows: B0, 12; B25, 14.81; B50, 11.11; B75, 12.25; and B100, 11.11%. Among all blends, B25 gives highest reduction% of CO of 14.81% at maximum load, may be due to oxygen concentration and cetane number of blend. Since MOME based fuel contains oxygen in fuel itself and it acts as a lesser combustion promoter inside the cylinder 7. Carbon dioxide (CO 2 ) IT (22 btdc) gives highest CO 2 as compared to all other ITs for all blends (Fig. 8b). As compared with standard IT of 23 btdc, increase% in CO 2 for IT (22 btdc) for fuels was found to be: B0, 8.57; B25, 11.43; B50, 9.83; B75, 8.22; and B100, 8.22%. Among all blends, B25 gives highest increase% in CO 2 at maximum load. B25 gives highest CO 2 in terms of reduction% at maximum load. Therefore better combustion takes place in the case of B25 as compared with all other blends. In general lower CO and higher CO 2 are preferable. Hydrocarbon (HC) IT (22 btdc) gives lowest hydrocarbon as compared to all other injection timings for all blends (Fig 8c). As compared with IT (23 btdc), reduction% of HC for IT of 22 btdc for fuels was found to be: B0, 30.6; B25, 31.25; B50, 13.16; B75, 13.51; and B100, 13.89%. Among all blends, B25 gives highest HC (31.25%) in terms reduction% of HC at maximum load, may be due to viscosity and surface tension affects penetration rate, maximum penetration and droplet size of fuel, which in turn affects mixing of fuel and air. Cetane number of fuel also plays a vital role in ignition process. Cetane number of B25 is higher than that of B0 (46.0-51.6). Therefore, B0 emits more HC than that of B25. Similar result was found in other study 5.

SOLAIMUTHU & GOVINDARAJAN: EFFECT OF INJECTION TIMING ON PERFORMANCE OF DIESEL ENGINE FUELED WITH MAHUA BIODIESEL 73 a) b) HC, ppm NOx, ppm CO, % by vol CO 2, % by vol c) d) Fig. 8 Blend ratio vs emissions: a) CO; b) CO 2 ; c) HC; and d) NOx Oxides of Nitrogen (NOx) IT (22 btdc) gives lowest NO x as compared to all other ITs for all blends (Fig. 8d). As compared with standard IT (23 btdc), reduction% in NO x for IT of 22 btdc for fuels were found to be: B0, 23.71; B25, 24.60; B50, 24.47; B75, 13.27; and B100, 15.53%. Among all blends, B25 gives highest NO x (24.60%) in terms of reduction% in NO x at maximum load, may be due to decrease in EGT. Vegetable based fuel contains a small amount of nitrogen, which contributes towards NO x production. NOx are reported to be increased with biodiesel 1 but present data shows reduction in NO x. Conclusions Under maximum load condition of engine, IT of 22 btdc gives better performance, combustion and lower emissions when compared with standard IT of 23 btdc. Of all blends tested at lower IT of 22 btdc, B25 provides best results in terms of higher BTE, higher heat release rate and low emissions of HC, CO and NO x. Hence B25 can be effectively used as an alternative biodiesel with IT of 22 btdc in tested engine. Even though only 25% of mahua oil ester is added with 75% pure diesel, blend will meet to a certain extent the shortage of availability of pure diesel. Mahua oil is available with lower cost than diesel in present scenario. Hence blend will be economical also for diesel trains, which normally operate on maximum load condition. References 1 Clark S J, Wanger L, Schrock M D & Piennaar P G, Methyl and ethyl soybean ester as renewable fuels for diesel engines, J Am Oil Che Soc, 61 (1984) 1632-1637. 2 Scholl K W & Sorenson S C, Combustion of soybean oil methyl ester in a direct injection diesel engine, SAE 930934, 1993. 3 Puhan S, Vedharaman N, Rambramhmam B V & Nagarajan G, Mahua (Madhuca indica) seed oil: A source of renewable energy in India, J Sci Ind Res, 64 (2005) 890-896. 4 Subramanian R, Rajendiran G, Venkatachalam R, Nedunchezhian N & Myilsamy K, Studies on performance and emission characteristics of multi cylinder diesel engine using hybrid fuel as fuel, J Sci Ind Res, 70 (2011) 539-543. 5 Puhan S, Nagarajan G, Vedaraman N & Ramabramhnam, Mahua oil (Madhuca indica oil) derivatives as a renewable fuel for diesel engine system in India: A performance and emissions comparative study, Int J Green Energy, 4 (2007) 89-104. 6 Puhan S & Nagarajan G, NO x reduction in a direct injection diesel engine using bio diesel as a renewable fuel, Int J Sus Energy, (2008) 143-154. 7 Puhan S, Vedaraman N, Boppana V, Ram B, Sankaranarayanan G et al, Mahua oil (Madhuca indica seed oil) methyl ester as biodiesel preparation and emission characteristics, Biomass Bioenergy, 28 (2005) 87-93.

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