Results And Discussion: Emulsified Palm Biodiesel Run Engine
6.4 Emission Analysis
(a) (b)
(c) (d)
Figure 6.11 Variation CO with engine load for different CR and IT for emulsified POME run engine
Figure 6.14 show that the trends of HC emissions for WIP run diesel engine with neat diesel data. The average HC emissions at no load to 110% load regions for WIP are 28.7, 25.2, 21.5, 19.3, 22.7, 26.2 and 28.5 ppm; whereas, for diesel the corresponding values are 60, 35, 19, 15, 20, 40 and 70 ppm. There is a direct connection between HC emission and load variation.
At lower load condition, the temperature becomes insufficient to burn all the fuel quantity supplied. With increase in loads, the amounts of air become insufficient to burn the increased fuel supply to cope up high load (Aziz et al., 2006). Both these facts raise HC emissions at low and high load regions. However, based on load variation, a drop of 33.6% of HC emission is attained for WIP as opposed to baseline diesel. This is due to the shortage of hydrogen ion to form stable HC, as oxygen present in POME carries away hydrogen in the form of OH radicals Owen and Coley (1995).
6.4.2 Effect of Compression Ratio
The increase in CR has a definite relationship with CO emissions as found from the experimental observations (Figure 6.11). For almost all the cases of ITs rise in CR reduce CO emission. The average CO emissions at 18 to 17 CRs are 20.0, 27.1 and 33.7 ppm respectively. Hence increase in CR from 17 to 17.5 and then 17.5 to 18 reduce CO emission by 24% and 36%. This is due to the fact that rise in CR reduces cylinder volume, resulting
10 30 50 70 90 110
0 20 40 60 80 100 120
Carbon Monoxide(ppm)
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
10 30 50 70 90 110
0 20 40 60 80 100 120
Carbon Monoxide (ppm)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):23ºBTDC
10 30 50 70 90 110
0 20 40 60 80 100 120
Carbon Monoxide (ppm)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):25ºBTDC
10 30 50 70 90 110
0 20 40 60 80 100 120
Carbon Monoxide(ppm)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):28ºBTDC
growth in the combustion temperature. This is further attributed to the presence of oxygen in POME (Masjuki et al., 1997). This fact is also liable for the growth of the CO2 emission with the increase in CRs as observed in the plots (Figure 6.12). The average CO2 emissions recorded are 2.80, 2.64, 2.59% (by volume) for the CRs of 18, 17.5 and17. Hence, the increase in CR from 17 to 17.5 and then 17.5 to 18 raise the CO2 emission by 6% and 2%, respectively. The surge of CO2 emission and drop of CO emission at higher CR have also been observed by Owen and Coley (1995). It is emphasized that the water vapor, came out from emulsion, forms OH radicals during combustion process. These radical concentrations promote carbon oxidation to CO and CO2 at higher temperature. As the CR increases, the cylinder becomes warmer, form more OH radicals, and convert CO to CO2.
(a) (b)
(c) (d)
Figure 6.12 Variation of CO2 emission with engine load for different CR and IT for emulsified POME run engine
The trends of NOX emissions (Figure. 6.13) show that increase in CR cuts NOX emission.
The average NOX emission obtained for the CR of 17, 17.5 and 18 are 43.3, 37.8 and 35.5 ppm. The increase in CR from 17 to 17.5 and from 17.5 to 18 causes an overall reduction of 15% and 6% for NOX emission for WIP. At high CR (say, 18), the pressure and temperature increases during the compression stroke and at the primary stages of combustion. This improves fuel vaporization and reduces physical ignition delay. Therefore, combustion is faster near TDC, and diffusion combustion stage is shortened. Further, at higher CR, BSFC is also found to be lower. As a result, the mass of combustible products reduces for the
1 2 3 4 5
0 20 40 60 80 100 120
Carbon Dioxide (%)
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
1 2 3 4 5
0 20 40 60 80 100 120
Carbon Dioxide (%)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):23ºBTDC
1 2 3 4 5
0 20 40 60 80 100 120
Carbon Dioxide (%)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):25ºBTDC
1 2 3 4 5
0 20 40 60 80 100 120
Carbon Dioxide (%)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):28ºBTDC
production of same power. This means, at higher CR, the lower quantity of combustion products reaches at cooler temperature at the end of combustion, which reverses in case of lower CR (say, 17). That is why, the NOX emission is lower at higher CR and vice versa.
Figure 6.14 shows the trend of HC emissions. The average HC emissions obtained for CR=17, 17.5 and 18 are 30.9, 23.6 and 19.2 ppm for WIP. Therefore, HC emission reduces by 31% and 23% as CR increase from 17 to 17.5 and 17.5 to 18. The micro-explosion phenomenon in the emulsified fuel is attributable to the volatility differences between water and diesel fuel. This violent collapse break up the fine droplets and augments the fuel–air mixing in the combustion chamber. That is why the HC formation decreases, as described in the literature (Kadota and Yamasaki, 2002).
(a) (b)
(c) (d)
Figure 6.13 Variation of NOX emission with engine load for different CR and IT for emulsified POME run engine
6.4.3 Effect of Injection Timing
The variations of CO emission with IT changes are shown in Fig. 6.11. For WIP, the IT retardation of 3º and IT advancements of 2º and 5º reduce CO emission by 1.0 % and increase of 4.9% and 1.5%, respectively. This is because at retarded IT of 20ºBTDC (fuel injection with piston reaches close to TDC) the cylinder environment becomes warmer and pressurized than other ITs, resulting faster combustion. The reverse phenomenon takes place at advanced IT. The trends of these results are identical to that of the works performed with canola methyl ester and its blend with diesel (Sequera et al., 2011). It is seen from Fig. 6.12 that retarding
0 30 60 90 120
0 20 40 60 80 100 120
Oxides of Nitrogen (ppm)
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 30 60 90 120
0 20 40 60 80 100 120
Oxides of Nitrogen (ppm)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):23ºBTDC
0 30 60 90 120
0 20 40 60 80 100 120
Oxides of Nitrogen (ppm)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):25ºBTDC
0 30 60 90 120
0 20 40 60 80 100 120
Oxides of Nitrogen (ppm)
Engine Load (%) SPEED:1500 RPM
IT(DIESEL):23ºBTDC IT(WIP):28ºBTDC
IT reduces CO2 emission by 3.1%, whereas IT advancements decrease 9.7% and 9.9%. The drops of CO2 emissions by both advancing and retarding IT is ascertained from the analogous effect on BSFC by performing similar IT changes. However, minor drop of CO2 by advancing IT implies that a bit more CO2 is formed at this IT, and lower CO is formed as discussed earlier.
(a) (b)
(c) (d)
Figure 6.14 Variation of HC with engine load for different CR and IT for emulsified POME run engine
The NOX variation of WIP run diesel engine reveals that IT retardation causes 14.6%
reduction whereas, advancements cause 24.7% and 48.1% increase in NOX emission (Figure 6.13). The discussions in the section 6.3.3 show that IT advancements increase PCPs, which ultimately increases peak temperature (Heywood, 1988). This is the reason for which NOX
concentrations increase by means of IT advancement. These trends are within close agreement with literature (Sequera et al., 2011). The retardation of IT reduces HC by 6.3%
and advancements increase 13.0% and 26.5%, respectively (Figure 6.14). Advancing the IT causes earlier initiation of combustion relative to the TDC. Because of this reason, the cylinder charge, being compressed as the piston moves to the TDC, had fairly higher temperatures. Data analyses demonstrate that the mean temperatures augment by 5% for all the IT modifications. This assists to cut the thickness of the flame-quenching layer. This is responsible for lesser HC emission (AbdAlla et al., 2002).
10 25 40 55 70
0 20 40 60 80 100 120
Hydrocarbon (ppm)
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
10 25 40 55 70
0 20 40 60 80 100 120
Hydrocarbon (ppm)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):23ºBTDC
10 25 40 55 70
0 20 40 60 80 100 120
Hydrocarbon (ppm)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):25ºBTDC
10 25 40 55 70
0 20 40 60 80 100 120
Hydrocarbon (ppm)
Engine Load (%) SPEED:1500 RPM IT(DIESEL):23ºBTDC
IT(WIP):28ºBTDC