Results And Discussion: Emulsified Palm Biodiesel Run Engine
6.2 Performance Analysis
The performance analyses discussed in following sections contain the variation of BP, BTHE, BSFC and EGT. The experiments are performed for constant speed of 1500±50 rpm. During the experiment the CR variations are executed for WIP at constant IT and plotted accordingly. The results obtained are discussed with respect to the three design and performance parameters, namely, load, CR and IT.
6.2.1 Effect of Load
It is known that BP has a liner relation with load, if speed is maintained constant. The trend is maintained linear (Fig. 6.1). Figure 6.2 shows the comparisons of BTHEs between neat diesel and WIP. The results shown in these figures are calculated by ignoring the water quantity contained in the emulsion. BTHE is defined as the ratio of BP and the product of fuel consumption and calorific value (Heywood, 1988). The rise in load increases BTHE for both neat diesel and 5% WIP for the tested CRs. For 5% WIP, the BTHEs at 100% load for CR of 16, 17, 17.5 and 18 are 27.4%, 27.7%, 27.9% and 28.7% as opposed to 28.9% for neat diesel.
At overload conditions (110% of full load) efficiency is found maximum for both, WIP and diesel irrespective of CR-IT combinations. For 5% WIP, the average BTHEs at the entire load range are 1.6%, 12.4%, 19.4%, 24.0%, 27.1%, 29.4% and 30.2%, whereas, for neat diesel, these values are 1.2%, 11.6%, 18.5%, 23.2%, 26.5%, 28.9% and 29.4%, respectively.
The increase in BTHE based on load for WIP compared to diesel is 7%. The BSFCs obtained for WIP are 5.66, 0.70, 0.45, 0.36, 0.32, 0.30 and 0.29 kg/kW-h, respectively (Figure 6.3). By average, these values are 4.6% lower than diesel and look interesting. Table 3.4 shows that 5% WIP emulsion has a calorific value, around 11% inferior than that of diesel. Still, it has not only covered up this shortage of LHV, but also produced same BP at lower fuel consumption compared to neat diesel. It clearly reveals that, ‘micro-explosion’ is present in the combustion, which promotes fuel-air mixing prior to combustion (Lin and Chen, 2008).
The variations of EGTs for various CR and IT combinations are shown in Fig. 6.4. The EGTs for load variations are 138ºC, 159ºC, 187ºC, 248ºC, 283ºC, 387ºC and 403ºC for 5% WIP tested whereas for diesel these are 132ºC, 149ºC, 178ºC, 226ºC, 306ºC, 425ºC and 498ºC. It means, the average EGT produced by WIP run engine at low-to-mid load range (0-60%) is higher than diesel. However, at higher loads (80%-110%) it is the reverse. This is because, at the lower load region, the cooler atmosphere inside the cylinder causes slow evaporation of water droplets in WIP and hence delays the combustion. This increases the exhaust gas temperature. However, at higher loads the engine consumes more fuel (which also contains more water droplets), resulting the cylinder to have ample heat and raises the rate of water
bubble explosion, consequently. As a result, more water vapor formation takes place, which have higher capacity of soaking heat, in the later phases of combustion as discussed by Abu- Zaid 2004. This causes more heat to be carried away from exhaust and notably cuts the EGT.
(a) (b)
(c) (d)
Figure 6.1 Variation of BP with engine load for different CR and IT for emulsified POME run engine
(a) (b)
(c) (d)
Figure 6.2 Variation of BTHE with engine load for different CR and IT for neat POME run engine
0 1 2 3 4
0 20 40 60 80 100 120
Brake Power (kW)
Engine Load (%)
DIESEL(CR:17.5) CR(WIP):17 CR(WIP):17.5 CR(WIP):18 SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):20ºBTDC
0 1 2 3 4
0 20 40 60 80 100 120
Brake Power (kW)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):23ºBTDC
0 1 2 3 4
0 20 40 60 80 100 120
Brake Power (kW)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):25ºBTDC
0 1 2 3 4
0 20 40 60 80 100 120
Brake Power (kW)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):28ºBTDC
0 7 14 21 28 35
0 20 40 60 80 100 120
Brake Thermal Efficiency (%)
Engine Load (%)
DIESEL(CR:17.5) CR(WIP):17 CR(WIP):17.5 CR(WIP):18 SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):20ºBTDC
0 7 14 21 28 35
0 20 40 60 80 100 120
Brake Thermal Efficiency (%)
Engine Load (%)
SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):23ºBTDC
0 7 14 21 28 35
0 20 40 60 80 100 120
Brake Thermal Efficiency (%)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):25ºBTDC
0 7 14 21 28 35
0 20 40 60 80 100 120
Brake Thermal Efficiency (%)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):28ºBTDC
6.2.2 Effect of Compression Ratio
The BP of the engine is a function of torque and speed. In the experiment, WIP emulsion is tested in VCR diesel engine at particular loads where speed remains constant. Hence, for each CR and IT combinations, BPs at those specific loads are constant. The comparisons of BTHEs of WIP at 100% load for various CRs at standard IT of 23ºBTDC with neat diesel operation are shown at Fig. 6.5.The increase in CR generally tends to increase BP (Jindal et al., 2010b). However, in this study, since the speed (hence the BP) is kept constant, the increase in CR reduces the BSFC. The result is obtained in the form of increased BTHEs for CR enhancement at 23ºBTDC. For 5% WIP, at 100% load, the BTHEs are 28.0%, 29.3% and 30.3% for CR=17, 17.5 and 18 as compared to 28.9% for diesel. That means both at standard CR of 17.5 and higher CR of 18, WIP performed more efficiently than diesel at the highest load. Similar behavior is observed at 110% load too, where maximum BTHEs of 5% WIP are obtained as 28.8%, 30.6% and 31.0% for CR of 17, 17.5 and 18 compared to 29.4% for neat diesel. Although WIP has a calorific value, lesser than diesel, still the WIP intake is almost close to diesel or even lesser than that. Till now, literature confirms this point for the emulsions made by ultrasonication with diesel as a continuous phase (Lin and Chen, 2006b).
Now it is also proved for biodiesel. Since ultrasonic emulsification produces emulsion with smaller water droplet in the dispersed phase (Lin and Chen, 2008).
(a) (b)
(c) (d)
Figure 6.3 Variation of BSFC with engine load for different CR and IT for emulsified POME run engine
0.20 0.34 0.48 0.62 0.76 0.90
0 20 40 60 80 100 120
Brake Specific Fuel Consumption(kg/kW-h)
Engine Load (%)
DIESEL(CR:17.5) CR(WIP):17 CR(WIP):17.5 CR(WIP):18 SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):20ºBTDC
0.20 0.34 0.48 0.62 0.76 0.90
0 20 40 60 80 100 120
Brake Specific Fuel Consumption(kg/kW-h)
Engine Load (%)
SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):23ºBTDC
0.20 0.34 0.48 0.62 0.76 0.90
0 20 40 60 80 100 120
Brake Specific Fuel Consumption(kg/kW-h)
Engine Load (%)
SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):25ºBTDC
0.20 0.34 0.48 0.62 0.76 0.90
0 20 40 60 80 100 120
Brake Specific Fuel Consumption(kg/kW-h)
Engine Load (%)
SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):28ºBTDC
The increase in CR reduced the EGT of the 5% WIP, except for the case of 28ºBTDC (Figure 6.4). The average temperatures at CR of 18, 17.5 and 17 are 238ºC, 242ºC and 251ºC. Hence, reduction of CR increased EGT from 1.6% to 3.5%. This is because, as CR increases the rate of micro-explosion increases. This produces heat sink effect by consuming heat and reduces the burning time during premixed combustion phase (Lin and Lin, 2007b).
(a) (b)
(c) (d)
Figure 6.4 Variation of EGT with engine load for different CR and IT for emulsified POME run engine
6.2.3 Effect of Injection Timing
The variation of IT has no consequence on the BP of the engine. This is because, the change of IT may modify the combustion phenomena, but then again it has to produce the equivalent power to adjust for the specific load. Side by side at each load, speed is also constant. Hence, BP also remains unchanged with IT variation. The variations of BTHEs with respect to IT modifications are seen in Fig. 6.2, where 20ºBTDC shows the superior performance among other ITs. The overall increase in BTHEs by IT retardation is around 6.1%, whereas, IT advancement of 5º reduces overall BTHE by 2.1%. Figure 6.6 shows that at 20ºBTDC, 18 CR provides 11% higher BTHE than neat diesel. Higher CR with retarded IT creates a very hot and pressurized environment inside the cylinder, which accelerates the mico-explosion, resulting faster burning and higher rate of flame propagation (Park et al., 2000). As a result, the fuel consumption is also reduced. Figure 6.3 reveals that the retardation of IT cuts the
100 200 300 400 500
0 20 40 60 80 100 120
Exhaust Gas Temperature (ºC)
Engine Load (%) DIESEL(CR:17.5)
CR(WIP):17 CR(WIP):17.5 CR(WIP):18 SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):20ºBTDC
100 200 300 400 500
0 20 40 60 80 100 120
Exhaust Gas Temperature (ºC)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):23ºBTDC
100 200 300 400 500
0 20 40 60 80 100 120
Exhaust Gas Temperature (ºC)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):25ºBTDC
100 200 300 400 500
0 20 40 60 80 100 120
Exhaust Gas Temperature (ºC)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):28ºBTDC
average WIP intake by 6.2%. This reduction in fuel supply demonstrates the fact of increase of BTHE for IT reduction. Except 28ºBTDC, the injection advancements (20, 23 and 25ºBTDC) show a uniform trend of increase in EGT. This is because, advancing the injection results the spray of fuel at relatively cooler temperature, as the piston stays comparatively faraway than TDC, which is an adverse condition of mico-explosion and water vaporization.
Hence, more retarded injection of fuel, better is the combustion and lower is the EGT.
Figure 6.5 Comparison of maximum BTHE with CR (IT=23ºBTDC) for emulsified POME run engine
Figure 6.6 Comparison of maximum BTHE with CR and IT for emulsified POME run engine