**4.1 Engine tests**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

which shortens the service life of the emission control system besides the additional

*Schematic diagram of a DOC and its operation in reducing emissions of CO and UHC through the process of* 

• parametrical factors, including the density of the DOC filter measured in channels per square inch, the cross-sectional area, the channel wall thickness,

This experiment is making a case for blending of WPPO whose n-alkenes are lower by 25% in auto-ignition, compared to diesel fuel whose n-alkenes are good for auto-ignition. The aromatics, which affect PM emissions, are very low in WPPO blends. According to Refs. [59, 60], WPPO consists of iso-alkanes, n-alkanes, and olefins in the region of 27, 25, and 9%, respectively, with over 30% content being undefined due to complicated and complex chemical bond structures. However, aromatic cyclo-alkanes (naphthalene) and aromatics poor in auto-ignition were also found to be 40% by volume [61]. Blending was preferred to improve the low pour point to improve the cold starting characteristics of WPPO. Second, blending with ethanol was introduced to improve the fuel spray characteristics; ethanol is soluble and miscible in WPPO blends. Third, blending contributed to the reduction of the viscosity of WPPO biodiesel, thus further

and the length of the channels using the external dimensions [57, 58].

effects on the natural environment and human health.

• conversion factor;

**Figure 10.**

*oxidation [6].*

• temperature stability;

• light-off temperature;

• tolerance to poisoning;

improving spray characteristics.

• cost of manufacturing the filter; and

**4. Methodology and experimental set-up**

Six factors affect and influence the choice of a DOC filter:

**44**

The experiment used a naturally aspirated four-cylinder diesel engine power generator, water cooled, direct injection, Iveco engine, in the Mechanical Engineering Department Laboratory, University of Kwazulu-Natal in Durban, South Africa. Using a defined flow rate of particles, PM emissions were detected by photoelectric measurement. Both the mass flow of the PM particles and the fuel were calculated as the sum of inlet air and fuel mass flow rate, and the result expressed in gram per kWh. To help in the analysis of the engine, pressure sensors and crankshaft position sensors and encoders were used. The aim of these sensors was to provide the in-cylinder pressure in relation to the crankshaft position variation.


#### **Table 2.**

*Experimental engine specifications.*


#### **Table 3.**

*List of equipment used in the experiment.*

#### **Figure 11.**

*Schematics of the test engine set up rig: (1) cylinder pressure sensor; (2) EGR control valve; (3) EGR cooler; (4) injection control unit; (5) exhaust gas exit; (6) air box; (7) signal amplifier; (8) gas analyzer; (9) air flow meter; (10) data acquisition system; (11) crank position sensor; (12) dynamometer; (13) engine; (14) cooling water exit from the dynamometer to the cooling tower; (15) cooling water exit from the engine to the cooling tower; and (16) dynamometer drive coupling.*

The engine was coupled to a mechanical dynamometer with engine idling positions divided into two engine speed modes. The two speed modes were set at 500 and 1000 rpm as Mode 1, and Mode 2 as 1500 rpm and full load at 2000 rpm. The details of the engine and specifications and equipment are described in **Tables 2** and **3**. **Figure 11** shows a schematic of the engine test setup.

#### **4.2 Physicochemical property analysis**

WPPO by pyrolysis was obtained from a commercial plant whose production chart is shown in **Figure 12**. Ethanol, conventional diesel, and EHN were purchased

#### **Figure 12.**

*Pyrolysis plant flow chart and its nomenclature: (1) pyrolysis reactor; (2) carbon black discharge; (3) carbon black deep processing; (4) exhaust smoke discharge; (5) gas separator; (6) smoke scrubber to take out color and odor; (7) condenser; (8) chimney; (9) oil tank; (10) synchronized gas purification; (11) synchronized gasrecycling system; (12) extra gas burning; (13) heating furnace during operation; and (14) loading of material.*

**47**

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel…*

**Properties Unit CD WPPO Ethanol** Density @ 20°C kg/m3 845 825 792 Visc.@ 40°C cSt 3.04 2.538 1.05 Cetane number — 55 — 8.5 Flash point °C 50 43 16 Fire point °C 56 45 53 Carbon residue % 22 0.015 — Sulfur content % <0.028 0.248 — Gross calories kJ/kg 46500 43340 29700 Cetane index – 46 65 —

*Properties of diesel, WPPO, and ethanol before blending and addition of EHN.*

*The distillate samples from the waste plastic pyrolysis oil samples.*

*Properties of blended ratio mixtures of diesel, ethanol, WPPO with EHN.*

**Property Unit CD 90/5/5 80/10/10 70/15/15 60/20/20 50/25/25 STANDARD** Density Kg/m3 845 838.5 834 830 825 823 ASTM D1298

GCV kJ/kg 44840 41245 39985 38700 36800 34500 ASTM D4868

Oxygen % 12.35 13.80 14.75 15.15 16.25 17.35 ASTM D5622

Hydrogen % 12.38 7.5 7.55 7.65 7.75 7.95 ASTM D7171

cST 3.452 2.38 2.37 2.365 2.340 2.325 ASTM D445


% <0.0124 0.0248 0.0249 0.0251 0.0253 0.0257 ASTM D4294

% 74.85 75.35 76.40 77.55 78.25 79.65 ASTM D

⁰C 56.5 38.5 37.55 37.35 37.15 36.85 ASTM D93

7662

*DOI: http://dx.doi.org/10.5772/intechopen.92569*

**Table 4.**

**Figure 13.**

Viscosity @ 40

Cetane number

Sulfur content

Carbon residue

Flash point

**Table 5.**

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel… DOI: http://dx.doi.org/10.5772/intechopen.92569*


#### **Table 4.**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

*Schematics of the test engine set up rig: (1) cylinder pressure sensor; (2) EGR control valve; (3) EGR cooler; (4) injection control unit; (5) exhaust gas exit; (6) air box; (7) signal amplifier; (8) gas analyzer; (9) air flow meter; (10) data acquisition system; (11) crank position sensor; (12) dynamometer; (13) engine; (14) cooling water exit from the dynamometer to the cooling tower; (15) cooling water exit from the engine to the cooling* 

The engine was coupled to a mechanical dynamometer with engine idling positions divided into two engine speed modes. The two speed modes were set at 500 and 1000 rpm as Mode 1, and Mode 2 as 1500 rpm and full load at 2000 rpm. The details of the engine and specifications and equipment are described in **Tables 2**

WPPO by pyrolysis was obtained from a commercial plant whose production chart is shown in **Figure 12**. Ethanol, conventional diesel, and EHN were purchased

and **3**. **Figure 11** shows a schematic of the engine test setup.

*Pyrolysis plant flow chart and its nomenclature: (1) pyrolysis reactor; (2) carbon black discharge; (3) carbon black deep processing; (4) exhaust smoke discharge; (5) gas separator; (6) smoke scrubber to take out color and odor; (7) condenser; (8) chimney; (9) oil tank; (10) synchronized gas purification; (11) synchronized gasrecycling system; (12) extra gas burning; (13) heating furnace during operation; and (14) loading of material.*

**46**

**Figure 12.**

**Figure 11.**

*tower; and (16) dynamometer drive coupling.*

**4.2 Physicochemical property analysis**

*Properties of diesel, WPPO, and ethanol before blending and addition of EHN.*

**Figure 13.** *The distillate samples from the waste plastic pyrolysis oil samples.*


#### **Table 5.** *Properties of blended ratio mixtures of diesel, ethanol, WPPO with EHN.*

from local outlets and blended using a homogenizer for 5 min at 3000 rpm. The properties of all samples were measured in the Chemical Engineering Laboratory of the University of Kwazulu-Natal in Durban, South Africa. **Table 3** shows some important physicochemical properties of the fuels before blending. **Table 4** shows physicochemical properties of fuels and their determined fuel properties after blending. **Figure 13** is a photograph of the sample distillates of WPPO obtained from pyrolysis. **Table 5** is showing properties of blended ratio mixtures of diesel, ethanol, WPPO with EHN.

## **5. Experimental results and discussion of diesel engine emissions**

#### **5.1 Brake-specific fuel consumption (BSFC)**

**Figure 14** is a variation in brake-specific fuel consumption (BSFC) with engine speed. The BSFC compared to the engine speed in **Figure 14** shows that as the speed increased, there is an equal increase of fuel consumed by the test engine. The values obtained at full engine speed (2000 rpm) for the blends of 90/WPPO5/ E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, 50/WPPO25/E25, and CD were 0.04 kg/kWh, 0.041 g/kWh, 0.042 kg/kWh, 0.043 kg/kWh, and 0.035 kg/kWh, respectively.

At high engine speeds, the conversion of heat energy to mechanical energy increases with the increase in combustion temperature, leading to increased BSFC for the biodiesel; this increase is proportional to the difference in their heating values, which is identical to the findings of Ref. [62]. These blends of WPPO compare well to CD fuel and other biodiesel blends with comparative differences in the heating values.

However, from the graph, it is evident that as the blend ratio increases, there is a decrease in the BSFC across all the test fuels. Nevertheless, the values for all WPPO blends were slightly higher than the CD test fuel. The closeness of the values and the packed graph reveals a close resemblance and identical BSFC characteristics of WPPO, ethanol, and EHN compared to CD fuel. For example, at 500 rpm engine speed, the blend of 80/WPPO10/E10 had a value of 0.043 g/kWh compared to full engine speed (2000 rpm) with 0.041 kg/kWh, which is higher than CD test fuel with 0.04 kg/kWh at 1000-rpm engine speed and 0.035 kg/kWh at full engine speed (2000 rpm).

**49**

**Figure 15.**

*Brake thermal efficiency versus engine speed.*

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel…*

The brake thermal efficiency (BTE) variations with engine speed are shown in **Figure 15**. The graphs show that as the speed increased, there was an increase in the BTE across all the test fuel blends of WPPO and CD up to 1500 rpm. At 1000 rpm engine speed, the values for blends 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/ E15, 60/WPPO20/E20, 50/WPPO25/E25, and CD were 22, 21, 20, 18, 16.5, and 22.5%, respectively. As the blend ratio and engine speed increased, there was a decrease in the BTE within the WPPO blends but an increase in BTE across the blends. For example, at 500 rpm engine speed, 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/ E15, 60/WPPO20/E20, and 50/WPPO25/E25 had values of 14, 13, 12.5, 11, and 9.5% compared to at 1000 rpm with values of 22, 21, 20, 18, and 16.5%, respectively. The highest BTE value was 24% by blend 90/WPPO5/E5 at 1500-rpm engine speed compared to any other blend of WPPO, ethanol, and/or EHN. This could be due to the density, which is closer to CD, and the effect of blending, which improved this blend's physico-chemical properties. **Figure 15** shows values of 24.8, 23, 21, and 19%, respectively, for blends 80/WPPO10/E10, 70/WPPO15/E15, 60/ WPPO20/E20, and 50/WPPO25/E25. Blend 50/WPPO25/E25 reported the lowest values compared to the other blends. At 500 rpm engine speed, the BTE value was

As the engine speed increased above 1500 rpm, the BTE suddenly dropped as the engine approached full engine speed (2000 rpm), as seen in **Figure 15**. There are a number of factors explaining the above results. For example, at this speed, there is a sudden drop of the air fuel ratio as the mixture becomes richer. This leads to incomplete combustion and heat release energy as more carbon molecules escape the combustion process. These increase the dissociation heat losses by the engine, hence a fall in BTE. Additionally, decreased BTE with biodiesel blends could be due to their low calorific value, higher viscosity, high volatility, and poor spray characteristics. These findings are consistent with other studies by the authors of Refs. [63–65].

Unburnt hydrocarbon (UHC) concentrations largely indicate the quality of the combustion in an internal combustion engine. UHC concentrations are formed from vaporized unburnt hydrocarbon fuel and partially burnt fuel by-products exiting the combustion chamber diesel exhaust system. UHC concentrations are inherently independent of the air fuel ratio of any working engine [6].

*DOI: http://dx.doi.org/10.5772/intechopen.92569*

9.5% compared with full engine speed (2000 rpm) at 19%.

**5.3 Unburnt hydrocarbon (UHC) concentration**

**5.2 Brake thermal efficiency (BTE)**

**Figure 14.** *BSFC versus engine speed.*

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel… DOI: http://dx.doi.org/10.5772/intechopen.92569*

#### **5.2 Brake thermal efficiency (BTE)**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

ethanol, WPPO with EHN.

kg/kWh, respectively.

the heating values.

speed (2000 rpm).

**5.1 Brake-specific fuel consumption (BSFC)**

from local outlets and blended using a homogenizer for 5 min at 3000 rpm. The properties of all samples were measured in the Chemical Engineering Laboratory of the University of Kwazulu-Natal in Durban, South Africa. **Table 3** shows some important physicochemical properties of the fuels before blending. **Table 4** shows physicochemical properties of fuels and their determined fuel properties after blending. **Figure 13** is a photograph of the sample distillates of WPPO obtained from pyrolysis. **Table 5** is showing properties of blended ratio mixtures of diesel,

**5. Experimental results and discussion of diesel engine emissions**

**Figure 14** is a variation in brake-specific fuel consumption (BSFC) with engine

speed. The BSFC compared to the engine speed in **Figure 14** shows that as the speed increased, there is an equal increase of fuel consumed by the test engine. The values obtained at full engine speed (2000 rpm) for the blends of 90/WPPO5/ E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, 50/WPPO25/E25, and CD were 0.04 kg/kWh, 0.041 g/kWh, 0.042 kg/kWh, 0.043 kg/kWh, and 0.035

At high engine speeds, the conversion of heat energy to mechanical energy increases with the increase in combustion temperature, leading to increased BSFC for the biodiesel; this increase is proportional to the difference in their heating values, which is identical to the findings of Ref. [62]. These blends of WPPO compare well to CD fuel and other biodiesel blends with comparative differences in

However, from the graph, it is evident that as the blend ratio increases, there is a decrease in the BSFC across all the test fuels. Nevertheless, the values for all WPPO blends were slightly higher than the CD test fuel. The closeness of the values and the packed graph reveals a close resemblance and identical BSFC characteristics of WPPO, ethanol, and EHN compared to CD fuel. For example, at 500 rpm engine speed, the blend of 80/WPPO10/E10 had a value of 0.043 g/kWh compared to full engine speed (2000 rpm) with 0.041 kg/kWh, which is higher than CD test fuel with 0.04 kg/kWh at 1000-rpm engine speed and 0.035 kg/kWh at full engine

**48**

**Figure 14.**

*BSFC versus engine speed.*

The brake thermal efficiency (BTE) variations with engine speed are shown in **Figure 15**. The graphs show that as the speed increased, there was an increase in the BTE across all the test fuel blends of WPPO and CD up to 1500 rpm. At 1000 rpm engine speed, the values for blends 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/ E15, 60/WPPO20/E20, 50/WPPO25/E25, and CD were 22, 21, 20, 18, 16.5, and 22.5%, respectively. As the blend ratio and engine speed increased, there was a decrease in the BTE within the WPPO blends but an increase in BTE across the blends. For example, at 500 rpm engine speed, 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/ E15, 60/WPPO20/E20, and 50/WPPO25/E25 had values of 14, 13, 12.5, 11, and 9.5% compared to at 1000 rpm with values of 22, 21, 20, 18, and 16.5%, respectively.

The highest BTE value was 24% by blend 90/WPPO5/E5 at 1500-rpm engine speed compared to any other blend of WPPO, ethanol, and/or EHN. This could be due to the density, which is closer to CD, and the effect of blending, which improved this blend's physico-chemical properties. **Figure 15** shows values of 24.8, 23, 21, and 19%, respectively, for blends 80/WPPO10/E10, 70/WPPO15/E15, 60/ WPPO20/E20, and 50/WPPO25/E25. Blend 50/WPPO25/E25 reported the lowest values compared to the other blends. At 500 rpm engine speed, the BTE value was 9.5% compared with full engine speed (2000 rpm) at 19%.

As the engine speed increased above 1500 rpm, the BTE suddenly dropped as the engine approached full engine speed (2000 rpm), as seen in **Figure 15**. There are a number of factors explaining the above results. For example, at this speed, there is a sudden drop of the air fuel ratio as the mixture becomes richer. This leads to incomplete combustion and heat release energy as more carbon molecules escape the combustion process. These increase the dissociation heat losses by the engine, hence a fall in BTE. Additionally, decreased BTE with biodiesel blends could be due to their low calorific value, higher viscosity, high volatility, and poor spray characteristics. These findings are consistent with other studies by the authors of Refs. [63–65].

#### **5.3 Unburnt hydrocarbon (UHC) concentration**

Unburnt hydrocarbon (UHC) concentrations largely indicate the quality of the combustion in an internal combustion engine. UHC concentrations are formed from vaporized unburnt hydrocarbon fuel and partially burnt fuel by-products exiting the combustion chamber diesel exhaust system. UHC concentrations are inherently independent of the air fuel ratio of any working engine [6].

**Figure 15.** *Brake thermal efficiency versus engine speed.*

In compression ignition (CI) engines, UHC concentrations are due to insufficient temperature, especially around the cylinder walls or in pockets. UHC concentrations are also formed through system malfunction, especially in input data failure in modern fuel injection systems. The higher hydrocarbon concentrations may be due to hydrogen radicals in the diesel-ethanol-WPPO-EHN blends. Principally, these concentrations are prevalent during light loads, when the combustion mixture is lean. This period is marked by a lower fuel ratio making the lean fuel-air mixture the primary source of the light load concentrations because of the lack of completion of the combustion during normal engine operating cycles. Hydrocarbon concentrations are not limited to vehicle exhaust systems but can occur in the entire vehicle fuel system from vapors during dispensing and distribution of fuel, which accounts for 15–20%, with the crankcase providing 20–30%. However, diesel exhaust remains the main culprit in engine emissions accounting for 50–60% of all the UHC concentration [66, 67].

**Figure 16** shows the variation of UHC emission with engine speed in the stationary diesel power generator using blends of biodiesel. As the engine speed was increased, the UHC concentration increased too. However, the increase was more significant as the engine speed was in intermediate speeds of 1500 rpm moving to or approaching full engine speed (2000 rpm). For example, at 1000 rpm, the values of blends 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 were 22, 21, 20, 18, and 15 ppm, respectively, compared to full engine speed (2000 rpm) with 35, 34, 32, 29, and 26 ppm. This leads to the conclusion that at high engine speeds, the values of UHC concentration is significantly high for all the blends of WPPO, ethanol, and EHN, although still comparatively low compared to CD fuel.

The UHC concentration from the blends 90/WPPO5/E5 and 80/WPPO10/E10 had higher values although from the graph plot in **Figure 16**, the values are still low compared to the values of CD test fuel. However, the general trend reported by the graph in **Figure 16** shows that as the blend ratio increased, there was a significant reduction in the UHC concentration, observed across all the test fuels irrespective of the engine speed condition, for all the blends tested compared to CD fuel. The reduction in UHC concentration is attributed to the high oxygen content and cetane number of the blends. The high oxygen content supports combustion, while the high cetane number reduces ignition delay. This is identical to other studies by other researchers [68–72].

**51**

**Figure 17.**

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel…*

The high fraction of ethanol in blends 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 contributed to the increase in the concentration of UHC, which is identical to the findings of Refs. [73, 74] who observed it in SI engine cylinder walls, crevices, and quenched cylinder walls, especially when richer air-alcohol mixtures were introduced. This type of UHC depends on the following factors: engine adjustments, engine design, and the type of fuel used in an engine. However, the engineoperating environment can sometimes contribute to the type of UHC concentration produced. This is observed especially when the temperature range is 400–600°C in the combustion chamber. At this temperature range, the hydrocarbons continue to experience reaction in the diesel exhaust pipe, thus lowering or increasing the

CO concentrations are a direct result of incomplete combustion, which results from hydrocarbons due to the failure of oxidation in the combustion process in diesel engines. This is true especially where the excess air factor λ meets the conditions λ < 1 for SI engines. Carbon monoxide is a colorless, tasteless, and odorless toxic gas, which is primarily a product of incomplete combustion of carbon containing fuels [6]. The United States is the single largest producer of carbon monoxide from anthropogenic sources as shown in **Figure 17** [77]. Carbon oxidation mechanisms are mostly determined by the equivalence ratio. Carbon monoxide concentrations mainly form in the areas of heavy traffic, parking garages, and under buildings, overheads, and overhangs. CO health effects include headaches and dizziness, but

**Figure 18** is the variation of CO with engine speed in a stationary diesel power generator. The graph reveals that as the engine speed and the blend ratio increased 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/ WPPO25/E25, the CO concentration decreased up to 1500 rpm of engine speed. Thereafter, the blends reported a continuous increase as the engine speed was approaching full engine speed (2000 rpm). At 500-rpm engine speed, the blends of 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/ WPPO25/E25 reported values of 0.055, 0.0565, 0.06, 0.0615, and 0.0625%.

However, as the speed is increased to 1500 rpm, the values were 0.035, 0.0375, 0.0445, and 0.0475%, respectively. At full engine speed (2000 rpm), all the test fuels showed increased CO concentration with blends 90/WPPO5/E5 and 80/

*Carbon monoxide (CO) concentrations by anthropogenic and biogenic sources in the United States [77].*

*DOI: http://dx.doi.org/10.5772/intechopen.92569*

**5.4 Carbon monoxide (CO) formation**

extreme exposure can lead to death.

concentration of the UHC in the exiting exhaust gas [75, 76].

**Figure 16.** *Unburnt hydrocarbons versus engine speed.*

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel… DOI: http://dx.doi.org/10.5772/intechopen.92569*

The high fraction of ethanol in blends 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 contributed to the increase in the concentration of UHC, which is identical to the findings of Refs. [73, 74] who observed it in SI engine cylinder walls, crevices, and quenched cylinder walls, especially when richer air-alcohol mixtures were introduced. This type of UHC depends on the following factors: engine adjustments, engine design, and the type of fuel used in an engine. However, the engineoperating environment can sometimes contribute to the type of UHC concentration produced. This is observed especially when the temperature range is 400–600°C in the combustion chamber. At this temperature range, the hydrocarbons continue to experience reaction in the diesel exhaust pipe, thus lowering or increasing the concentration of the UHC in the exiting exhaust gas [75, 76].

#### **5.4 Carbon monoxide (CO) formation**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

In compression ignition (CI) engines, UHC concentrations are due to insufficient temperature, especially around the cylinder walls or in pockets. UHC concentrations are also formed through system malfunction, especially in input data failure in modern fuel injection systems. The higher hydrocarbon concentrations may be due to hydrogen radicals in the diesel-ethanol-WPPO-EHN blends. Principally, these concentrations are prevalent during light loads, when the combustion mixture is lean. This period is marked by a lower fuel ratio making the lean fuel-air mixture the primary source of the light load concentrations because of the lack of completion of the combustion during normal engine operating cycles. Hydrocarbon concentrations are not limited to vehicle exhaust systems but can occur in the entire vehicle fuel system from vapors during dispensing and distribution of fuel, which accounts for 15–20%, with the crankcase providing 20–30%. However, diesel exhaust remains the main culprit in engine emissions accounting for 50–60% of all

**Figure 16** shows the variation of UHC emission with engine speed in the stationary diesel power generator using blends of biodiesel. As the engine speed was increased, the UHC concentration increased too. However, the increase was more significant as the engine speed was in intermediate speeds of 1500 rpm moving to or approaching full engine speed (2000 rpm). For example, at 1000 rpm, the values of blends 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 were 22, 21, 20, 18, and 15 ppm, respectively, compared to full engine speed (2000 rpm) with 35, 34, 32, 29, and 26 ppm. This leads to the conclusion that at high engine speeds, the values of UHC concentration is significantly high for all the blends of WPPO, ethanol, and EHN, although still comparatively

The UHC concentration from the blends 90/WPPO5/E5 and 80/WPPO10/E10 had higher values although from the graph plot in **Figure 16**, the values are still low compared to the values of CD test fuel. However, the general trend reported by the graph in **Figure 16** shows that as the blend ratio increased, there was a significant reduction in the UHC concentration, observed across all the test fuels irrespective of the engine speed condition, for all the blends tested compared to CD fuel. The reduction in UHC concentration is attributed to the high oxygen content and cetane number of the blends. The high oxygen content supports combustion, while the high cetane number reduces ignition delay. This is identical to other studies by other

**50**

**Figure 16.**

*Unburnt hydrocarbons versus engine speed.*

the UHC concentration [66, 67].

low compared to CD fuel.

researchers [68–72].

CO concentrations are a direct result of incomplete combustion, which results from hydrocarbons due to the failure of oxidation in the combustion process in diesel engines. This is true especially where the excess air factor λ meets the conditions λ < 1 for SI engines. Carbon monoxide is a colorless, tasteless, and odorless toxic gas, which is primarily a product of incomplete combustion of carbon containing fuels [6]. The United States is the single largest producer of carbon monoxide from anthropogenic sources as shown in **Figure 17** [77]. Carbon oxidation mechanisms are mostly determined by the equivalence ratio. Carbon monoxide concentrations mainly form in the areas of heavy traffic, parking garages, and under buildings, overheads, and overhangs. CO health effects include headaches and dizziness, but extreme exposure can lead to death.

**Figure 18** is the variation of CO with engine speed in a stationary diesel power generator. The graph reveals that as the engine speed and the blend ratio increased 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/ WPPO25/E25, the CO concentration decreased up to 1500 rpm of engine speed. Thereafter, the blends reported a continuous increase as the engine speed was approaching full engine speed (2000 rpm). At 500-rpm engine speed, the blends of 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/ WPPO25/E25 reported values of 0.055, 0.0565, 0.06, 0.0615, and 0.0625%.

However, as the speed is increased to 1500 rpm, the values were 0.035, 0.0375, 0.0445, and 0.0475%, respectively. At full engine speed (2000 rpm), all the test fuels showed increased CO concentration with blends 90/WPPO5/E5 and 80/

#### *Numerical and Experimental Studies on Combustion Engines and Vehicles*

**Figure 18.** *Carbon monoxide versus engine speed.*

WPPO10/E10 reporting the lowest concentration among the test blends across all the engine speed conditions. At 1000 rpm, the blends reported values of 0.0445 and 0.0475% compared to full engine speed (2000 rpm) with 0.0425 and 0.0465%, respectively. The increased CO concentration, although lower than diesel fuel, can be attributed to partial combustion [78] as the speed increased and the presence of ethanol, which shortened ignition delay, thus increasing CO concentration.

As the engine speed and the blend ratio increased, there was an increase in the CO emission across all the engine speeds and within the blends and CD test fuel. At 1000 rpm engine speed, the values of the blends and CD were 0.045, 0.0475, 0.0515, 0.0535, 0.0565, and 0.05% for 90/WPPO5/E5, 80/WPPO10/E10, 70/ WPPO15/E15, 60/WPPO20/E20, 50/WPPO25/E25, and CD, respectively. The above values obtained from **Figure 18** suggest that there was a reduction in CO concentration across all test fuels irrespective of blend ratio and type of fuel except at high engine speeds exceeding 1500 rpm to full engine speed (2000 rpm). After this point, there was a steady increase in the concentration of CO.

CO concentration is a direct result of poor oxidation of the hydrocarbon fuels in the combustion chamber but is determined by the local fuel/air equivalence ratio. The above scenario is due to the air/fuel ratio becoming richer as the speed increased, leading to insufficient mixing of oxygen and fuel molecules. Compared to CD, all the biodiesels tested showed decreased CO concentration due to the high oxygen content in the test biodiesels and the addition of EHN, which greatly increased the cetane number (CN). This is identical to the studies by the authors of Refs. [79, 80]. The initial concentrations were greater at the starting engine speed of 500 rpm due to low temperature and emission instability processes at lower engine speeds, which are identical to the studies of Ref. [81]. However, as the engine speed increased from 1500 rpm toward full engine speed (2000 rpm), there was an observed increase in CO concentration, despite the oxygen content of the biodiesel and increased CN of the blends of WPPO, ethanol, and EHN. This disagreement in experimental results is due to differences in CN for the different biodiesel test fuel blends used. The increment in CN as the blend ratio increased led to increases in fuel quantity burnt during diffusive combustion, hence increasing CO concentration as the quality of combustion decreased.

#### **5.5 Particulate matter (PM) formation**

PM is agglomerates of small particle phase compounds resulting from the combustion of partially burned lubrication oil, the ash content from the fuel, sulfates from the engine cylinder wall, lubrication oil, and water from condensation and the

**53**

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel…*

combustion process [82]. These emitted compounds comprise elemental carbon (EC), organic carbon (OC) trace, and unknown compounds. Both EC and OC contribute to the toxicity of PM, regional haze, and climate change; therefore, PM concentration negatively affects the environment and human health [83]. The Global Burden of Disease Index reports that these types of emission are now responsible for 3.2 million deaths due to PM2.5 ambient pollution [84]. Besides this, PM concentration causes deposit formation in the combustion chamber, fouling of emission control systems such as EGR and DPF and increased engine wear and premature failure. PM concentration is primarily controlled by factors such as fuel quality (sulfur

and ash content in fuel), engine lubrication oil quality, fuel consumption per combustion cycle of the engine, exhaust cooling rate, and the combustion process or strategy applied [85]. A number of PM characterization research works have been conducted categorizing PM concentration as 41% carbon, 7% unburned fuel, 25% unburned oil, 14% sulfates, water, 13% ash, and other concentrations [83]. However, an earlier study conducted by Agrawal et al. [86] reported that particulate concentration contains ≅31% elemental carbon, ≅14% sulfates and moisture, ≅7% unburnt fuel, and ≅40% unburnt lubricating oil. A study by Thiruvengadam et al. [87] yielded a similar outcome in terms of PM concentration except that the study

PM concentration is divided into three main components: SOF, soot, and inorganic fraction (IF), 50% of which is released as soot in the diesel exhaust pipe. SOF emissions are made up of condensed hydrocarbons embedded within the soot emissions in the form of very fine particles. The size distribution of PM concentration has three peaks: the nucleation peak, which includes all volatile hydrocarbons (Dp<~30 nm), the accumulation mode (~30 nm*<* Dp*<*~500 nm), and the coarse mode (~500 nm*<*Dp*<*~10 μm) [88]. These emissions are more pronounced during starting and engine idling when engine temperatures are reportedly very low [89]. Studies on OC/EC in PM samples show that their ratio is elevated in biodiesel combustion as the biodiesel blend ratio increases. This is mainly due to the high oxygen content in biodiesel and plays a major role in the generation of soot particles and final oxidation. For example, in a study by Chuepeng et al. [90], the authors reported that the OC fraction for B30 was greater than ULSD regardless of the engine speed and operating conditions. In another study by Williams et al. [91], a similar pattern was established for OC and EC as B100 > B20 > Diesel. This is identical to the studies of Ref. [90], which suggested an increased OC content with

Cheung et al. [92] used soy methyl esters in an LD engine and found that the EC fraction was lower than during diesel operation. Nevertheless, the OC fraction in the PM concentration sample became identical for both LD and HD engines with the New European Driving Cycle (NEDC). However, a study by Song et al. [10] differs with this finding. Using cottonseed biodiesel, the authors reported decreased OC and EC driving conditions. This was mainly due to engine operating conditions, test methods, and test fuel chemical properties [83]. However, these studies have been inconsistent and inconclusive in the literature surveyed. For example, this is

DPF filters have now become part of virtually all diesel vehicles in the leading industrialized countries in the world (Europe, the United States, and Japan). DPF filters have had a high market penetration in Japanese and American LD and HD trucks since 2007. For smaller vehicle applications, subsequent developments have incorporated the diesel oxidation catalyst (DOC) function into the filter as reported by the authors of Refs. [10, 97]. It should be noted that for PM emission control in medium engines, the methods and approaches used are similar to the LD engines. However, in the US market, auxiliary fuel injectors and burners are incorporated into the

*DOI: http://dx.doi.org/10.5772/intechopen.92569*

was based on natural gas engine technology.

increased biodiesel fraction in a blend.

revealed in the studies of Refs. [90, 92–96].

#### *Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel… DOI: http://dx.doi.org/10.5772/intechopen.92569*

combustion process [82]. These emitted compounds comprise elemental carbon (EC), organic carbon (OC) trace, and unknown compounds. Both EC and OC contribute to the toxicity of PM, regional haze, and climate change; therefore, PM concentration negatively affects the environment and human health [83]. The Global Burden of Disease Index reports that these types of emission are now responsible for 3.2 million deaths due to PM2.5 ambient pollution [84]. Besides this, PM concentration causes deposit formation in the combustion chamber, fouling of emission control systems such as EGR and DPF and increased engine wear and premature failure.

PM concentration is primarily controlled by factors such as fuel quality (sulfur and ash content in fuel), engine lubrication oil quality, fuel consumption per combustion cycle of the engine, exhaust cooling rate, and the combustion process or strategy applied [85]. A number of PM characterization research works have been conducted categorizing PM concentration as 41% carbon, 7% unburned fuel, 25% unburned oil, 14% sulfates, water, 13% ash, and other concentrations [83]. However, an earlier study conducted by Agrawal et al. [86] reported that particulate concentration contains ≅31% elemental carbon, ≅14% sulfates and moisture, ≅7% unburnt fuel, and ≅40% unburnt lubricating oil. A study by Thiruvengadam et al. [87] yielded a similar outcome in terms of PM concentration except that the study was based on natural gas engine technology.

PM concentration is divided into three main components: SOF, soot, and inorganic fraction (IF), 50% of which is released as soot in the diesel exhaust pipe. SOF emissions are made up of condensed hydrocarbons embedded within the soot emissions in the form of very fine particles. The size distribution of PM concentration has three peaks: the nucleation peak, which includes all volatile hydrocarbons (Dp<~30 nm), the accumulation mode (~30 nm*<* Dp*<*~500 nm), and the coarse mode (~500 nm*<*Dp*<*~10 μm) [88]. These emissions are more pronounced during starting and engine idling when engine temperatures are reportedly very low [89].

Studies on OC/EC in PM samples show that their ratio is elevated in biodiesel combustion as the biodiesel blend ratio increases. This is mainly due to the high oxygen content in biodiesel and plays a major role in the generation of soot particles and final oxidation. For example, in a study by Chuepeng et al. [90], the authors reported that the OC fraction for B30 was greater than ULSD regardless of the engine speed and operating conditions. In another study by Williams et al. [91], a similar pattern was established for OC and EC as B100 > B20 > Diesel. This is identical to the studies of Ref. [90], which suggested an increased OC content with increased biodiesel fraction in a blend.

Cheung et al. [92] used soy methyl esters in an LD engine and found that the EC fraction was lower than during diesel operation. Nevertheless, the OC fraction in the PM concentration sample became identical for both LD and HD engines with the New European Driving Cycle (NEDC). However, a study by Song et al. [10] differs with this finding. Using cottonseed biodiesel, the authors reported decreased OC and EC driving conditions. This was mainly due to engine operating conditions, test methods, and test fuel chemical properties [83]. However, these studies have been inconsistent and inconclusive in the literature surveyed. For example, this is revealed in the studies of Refs. [90, 92–96].

DPF filters have now become part of virtually all diesel vehicles in the leading industrialized countries in the world (Europe, the United States, and Japan). DPF filters have had a high market penetration in Japanese and American LD and HD trucks since 2007. For smaller vehicle applications, subsequent developments have incorporated the diesel oxidation catalyst (DOC) function into the filter as reported by the authors of Refs. [10, 97]. It should be noted that for PM emission control in medium engines, the methods and approaches used are similar to the LD engines. However, in the US market, auxiliary fuel injectors and burners are incorporated into the

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

WPPO10/E10 reporting the lowest concentration among the test blends across all the engine speed conditions. At 1000 rpm, the blends reported values of 0.0445 and 0.0475% compared to full engine speed (2000 rpm) with 0.0425 and 0.0465%, respectively. The increased CO concentration, although lower than diesel fuel, can be attributed to partial combustion [78] as the speed increased and the presence of

As the engine speed and the blend ratio increased, there was an increase in the CO emission across all the engine speeds and within the blends and CD test fuel. At 1000 rpm engine speed, the values of the blends and CD were 0.045, 0.0475, 0.0515, 0.0535, 0.0565, and 0.05% for 90/WPPO5/E5, 80/WPPO10/E10, 70/

WPPO15/E15, 60/WPPO20/E20, 50/WPPO25/E25, and CD, respectively. The above values obtained from **Figure 18** suggest that there was a reduction in CO concentration across all test fuels irrespective of blend ratio and type of fuel except at high engine speeds exceeding 1500 rpm to full engine speed (2000 rpm). After this

CO concentration is a direct result of poor oxidation of the hydrocarbon fuels in the combustion chamber but is determined by the local fuel/air equivalence ratio. The above scenario is due to the air/fuel ratio becoming richer as the speed increased, leading to insufficient mixing of oxygen and fuel molecules. Compared to CD, all the biodiesels tested showed decreased CO concentration due to the high oxygen content in the test biodiesels and the addition of EHN, which greatly increased the cetane number (CN). This is identical to the studies by the authors of Refs. [79, 80]. The initial concentrations were greater at the starting engine speed of 500 rpm due to low temperature and emission instability processes at lower engine speeds, which are identical to the studies of Ref. [81]. However, as the engine speed increased from 1500 rpm toward full engine speed (2000 rpm), there was an observed increase in CO concentration, despite the oxygen content of the biodiesel and increased CN of the blends of WPPO, ethanol, and EHN. This disagreement in experimental results is due to differences in CN for the different biodiesel test fuel blends used. The increment in CN as the blend ratio increased led to increases in fuel quantity burnt during diffusive combustion, hence increasing CO concentra-

PM is agglomerates of small particle phase compounds resulting from the combustion of partially burned lubrication oil, the ash content from the fuel, sulfates from the engine cylinder wall, lubrication oil, and water from condensation and the

ethanol, which shortened ignition delay, thus increasing CO concentration.

point, there was a steady increase in the concentration of CO.

tion as the quality of combustion decreased.

**5.5 Particulate matter (PM) formation**

**52**

**Figure 18.**

*Carbon monoxide versus engine speed.*

diesel exhaust to regenerate DPFs. This method has concerns over oil dilution in the crankcase and requires a separation with the engine management system demands, so it has become more complex in the manner of its development and use [98, 99].

Advances in the science of materials have greatly increased and therefore influenced the development in filter materials for LD and HD engines. LD vehicles have seen silicon carbide types of filters becoming standard installation, although the alternative use of aluminum titanate is gradually replacing it [97]. However, aided by better engine controls, the industry has now moved to cordierite filters [101, 102]. **Figure 19** shows new hybrid developments in DPF filtering technology, which reduces 95% of NOX that comes from the DPF filter.

As shown in **Figure 20**, speed affects particle emission of blends. Nevertheless, differences in engine operating conditions, particulate formation, in-cylinder combustion processes, and engine type give mixed results and conclusions in PM emission studies. In **Figure 20**, it is evident that as speed increases, combustion time (residence time) is reduced, which reduces the reoxidation and combustion of the constituents of the process. This aptly explains the reason behind increased PM particle size and concentration as the speed tends toward full engine speed (2000 rpm), as typified in the graph in **Figure 20**. For example, PM concentration at 500 rpm is 0.15, 0.11, 0.094, 0.086, 0.063, and 0.051 kg/kWh, respectively, for CD, 90/WPPO5/ E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25.

However, as the speed increases from 500 to 1500 rpm, which is an intermediate speed, the PM emission increases and almost doubles to 0.29, 0.25, 0.235, 0.213, 0.183, and 0.57 g/kWh. These are for CD, 90/WPPO5/E5, 80/WPPO10/E10, 70/ WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25, respectively. These findings are identical to the studies of Refs. [103, 104]. In other words, these blends, when combusting, produce low heat loss to the wall resulting in increased soot oxidation, which is also reported conclusively in a study by Di Iorio et al. [105] and is identical to the findings of this work in **Figure 20**.

Since PM concentrations are influenced by engine operating conditions at 1500–2000 rpm, PM concentration decreases with increased blend fraction. The reduction is more with higher blend ratios 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 at 2000 rpm. However, there is a reversed reduction in CD fuel compared to the blends of WPPO as shown in **Figure 20**. This is due to diffusive combustion as the blend ratio increases (tends to B100) and the oxygen content of the blends increases. These findings are identical to the findings of a study by Di Iorio et al. [105].

#### **Figure 19.**

*A new NO2 remediation system reduces 95% of the NO2 emissions from catalyzed filter systems (courtesy of Technical University Dresden and Johnson Matthey) [100].*

**55**

**Figure 21.**

*CO2 versus engine speed.*

services [106].

**Figure 20.**

2.55, and 2.25%, respectively.

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel…*

CO2 is one of the gases responsible for maintaining the earth's optimal ecosystem balance. It enriches plants through the photosynthesis process and provides other benefits for the environment. However, CO2 has become a topical global issue in recent decades due to its increase from levels of 0.04% in the atmosphere. The increase in CO2 causes an increase in global temperatures due to the effect of blanketing. There are generally two sources of CO2 formation: human activities and naturally occurring sources such as the ocean-atmosphere exchange, plant and animal respiration, soil respiration, decomposition of waste and elements, and volcanic eruptions. The majority of the human sources are due to the burning of hydrocarbon fuels in transport and power generation, land activities such as mining and agriculture, and industrial processes and manufacturing. The main gas produced from human activity is greenhouse gas associated with activities such as combustion of fossil fuels, namely, coal, natural gas, and oil for commercial and transportation

*PM emission for different blends of WPPO biodiesel fuel from 500 rpm to full engine speed (2000 rpm).*

**Figure 21** shows the variation of CO2 with engine speed. The graph shows that as the blend ratio and engine speed increased, CO2 concentration increased, but compared to CD, their emission levels were still lower and almost identical. At 500 rpm engine speed, the values of CD and the blends of 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 were 3.58, 3.35, 2.95, 2.6,

*DOI: http://dx.doi.org/10.5772/intechopen.92569*

**5.6 Carbon dioxide (CO2) concentration**

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel… DOI: http://dx.doi.org/10.5772/intechopen.92569*

**Figure 20.**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

which reduces 95% of NOX that comes from the DPF filter.

to the findings of this work in **Figure 20**.

*Technical University Dresden and Johnson Matthey) [100].*

diesel exhaust to regenerate DPFs. This method has concerns over oil dilution in the crankcase and requires a separation with the engine management system demands, so it has become more complex in the manner of its development and use [98, 99]. Advances in the science of materials have greatly increased and therefore influenced the development in filter materials for LD and HD engines. LD vehicles have seen silicon carbide types of filters becoming standard installation, although the alternative use of aluminum titanate is gradually replacing it [97]. However, aided by better engine controls, the industry has now moved to cordierite filters [101, 102]. **Figure 19** shows new hybrid developments in DPF filtering technology,

As shown in **Figure 20**, speed affects particle emission of blends. Nevertheless,

differences in engine operating conditions, particulate formation, in-cylinder combustion processes, and engine type give mixed results and conclusions in PM emission studies. In **Figure 20**, it is evident that as speed increases, combustion time (residence time) is reduced, which reduces the reoxidation and combustion of the constituents of the process. This aptly explains the reason behind increased PM particle size and concentration as the speed tends toward full engine speed (2000 rpm), as typified in the graph in **Figure 20**. For example, PM concentration at 500 rpm is 0.15, 0.11, 0.094, 0.086, 0.063, and 0.051 kg/kWh, respectively, for CD, 90/WPPO5/ E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25. However, as the speed increases from 500 to 1500 rpm, which is an intermediate speed, the PM emission increases and almost doubles to 0.29, 0.25, 0.235, 0.213, 0.183, and 0.57 g/kWh. These are for CD, 90/WPPO5/E5, 80/WPPO10/E10, 70/ WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25, respectively. These findings are identical to the studies of Refs. [103, 104]. In other words, these blends, when combusting, produce low heat loss to the wall resulting in increased soot oxidation, which is also reported conclusively in a study by Di Iorio et al. [105] and is identical

Since PM concentrations are influenced by engine operating conditions at 1500–2000 rpm, PM concentration decreases with increased blend fraction. The reduction is more with higher blend ratios 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 at 2000 rpm. However, there is a reversed reduction in CD fuel compared to the blends of WPPO as shown in **Figure 20**. This is due to diffusive combustion as the blend ratio increases (tends to B100) and the oxygen content of the blends increases. These findings are identical to the findings of a study by Di Iorio et al. [105].

*A new NO2 remediation system reduces 95% of the NO2 emissions from catalyzed filter systems (courtesy of* 

**54**

**Figure 19.**

*PM emission for different blends of WPPO biodiesel fuel from 500 rpm to full engine speed (2000 rpm).*

### **5.6 Carbon dioxide (CO2) concentration**

CO2 is one of the gases responsible for maintaining the earth's optimal ecosystem balance. It enriches plants through the photosynthesis process and provides other benefits for the environment. However, CO2 has become a topical global issue in recent decades due to its increase from levels of 0.04% in the atmosphere. The increase in CO2 causes an increase in global temperatures due to the effect of blanketing. There are generally two sources of CO2 formation: human activities and naturally occurring sources such as the ocean-atmosphere exchange, plant and animal respiration, soil respiration, decomposition of waste and elements, and volcanic eruptions. The majority of the human sources are due to the burning of hydrocarbon fuels in transport and power generation, land activities such as mining and agriculture, and industrial processes and manufacturing. The main gas produced from human activity is greenhouse gas associated with activities such as combustion of fossil fuels, namely, coal, natural gas, and oil for commercial and transportation services [106].

**Figure 21** shows the variation of CO2 with engine speed. The graph shows that as the blend ratio and engine speed increased, CO2 concentration increased, but compared to CD, their emission levels were still lower and almost identical. At 500 rpm engine speed, the values of CD and the blends of 90/WPPO5/E5, 80/WPPO10/E10, 70/WPPO15/E15, 60/WPPO20/E20, and 50/WPPO25/E25 were 3.58, 3.35, 2.95, 2.6, 2.55, and 2.25%, respectively.

**Figure 21.** *CO2 versus engine speed.*

**Figure 21** also shows that as the speed increased, there was a significant increase in the CO2 concentration across all test fuels, although with lower values as the blend ratio increased. For example, CD fuel had values of 2, 3.85, 5.95, and 8.95% for engine speeds of 500, 1000, 1500, and 2000 rpm compared to blend 80/WPPO10/ E10 with 1.8, 2.95, 4.85, and 8.55% for similar speeds. The blend with the lowest value of CO2 emission was 50/WPPO25/E25 with values of 1.62, 2.25, 3.65, and 7.35%, respectively, for engine speeds of 500, 1000, 1500, and 2000 rpm, respectively. The increased carbon concentration in biodiesel blends is due to the reduction in the quantity of carbon relative to the increased oxygen ratio. However, the lower CO2 concentration levels in comparison to CD fuel are due to factors explained under BTE and the equal energy balance generated by the addition of alcohol.

### **5.7 Nitrogen oxide (NOX) concentration**

NOX concentration and its oxidized product NO2 are the primary preserve of the diesel engine, constituting 85–95% of the total emission of a diesel engine. There are two fundamental differences between the two gases: whereas NOX is odorless and colorless, NO2 is reddish with a pungent smell [107]. It should be mentioned here that NO2 is five times more toxic than NOX gas and is a health hazard to the human respiratory system. It irritates the respiratory system and lowers the resistance to diseases such as the common cold and influenza [9, 108].

SCR is one of the leading NOX emission control techniques for both LD and HD vehicles. This system entered the market in Japan and Europe for the HD category in 2005 compared to the US market in 2010. In the Japanese market and in Europe, zeolite and vanadium-based catalysts are utilized, respectively. The zeolite SCR catalyst combination performs better and has higher temperature tolerance levels. There is ongoing research to improve low temperature performance for more accurate NO2 and NOX concentration predictions [110–112].

The low NOX trap (LNT) is a cheaper option for engines that are 2000–2500 cc [113, 114]. This type of emission control technique works better with mixed-mode engines to reduce low-load NOX that is a persistent problem in SCR systems. This allows the LNT to focus on high temperature NOX that is entering at temperatures over 300°C, thus eliminating between 60 and 70% of the platinum group metals (PGMs) [115]. This makes the LNT technology cheaper and economically appealing to the LD engine classification of 5000–6000 cc capacity [116, 117]. However, for medium- and heavy-duty vehicles, high temperature solutions have been developed to address the challenge of high load requirements of the US NTE regulatory condition as reported by the authors of Refs. [101, 118].

The LNT technique suffers due to contamination from sulfur, which shortens and affects its service life and durability. Earlier versions of LNT lost 50% filtration capacity, while the current generation of LNTs loses only 25% [119, 120]. Desulfication can be accomplished by passing a rich hot steam of diesel fuel at 700°C for 10 min at service intervals of 5000–10,000 km. **Figure 22** shows a new concept of combining the SCR emission control system with the LNT emission control system.

NOX concentration is now known to be temperature dependent due to their equilibrium concentration presence in the combustion chamber. NOX when mixed in high temperature adiabatically in the temperature range of 2000–3000 k forms NOX concentration, which is then exited through the diesel exhaust system [121]. The NOX concentration has four basic mechanisms of formation within the combustion chamber of a diesel engine: the Zeldovich mechanism also called the thermal NOX route, the prompt mechanism, the fuel mechanism, and the NNH mechanism [122]. The variation of engine speed with NOX concentration is shown in **Figure 23**. The graph shows that as the engine speed was increased, there was an increase in the

**57**

**Figure 23.**

*Oxides of nitrogen versus engine speed.*

to increased NOX.

**Figure 22.**

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel…*

NOX concentration irrespective of fuel, blend ratio, or additive. However, the value of NOX concentration from the blends 90/WPPO5/E5, 80/WPPO10/E10, and 70/ WPPO15/E15 reported lower values than CD fuel. For example, at 1000 rpm, the value of the blends was 385, 396, and 415 ppm, compared to CD fuel at 425 ppm. Blends 60/WPPO20/E20 and 50/WPPO25/E25 had the highest NOX concentration compared to the other blends of 90/WPPO5/E5, 80/WPPO10/E10, and 70/ WPPO15/E15 across all the engine speed conditions tested. At 500 rpm engine speed, the two blends had values of 205 and 200 ppm, respectively. At full engine speed (2000 rpm), NOX concentration values increased to 925 and 885 ppm compared to blend 90/WPPO5/E5 at 197 ppm and 792 ppm at full engine speed (2000 rpm). The graph in **Figure 23** shows that as the blend ratio increased, there was a direct increase in the concentration of NOX across all the blended test fuels. However, blend 90/WPPO5/E5 reported the lowest values of NOX concentration compared to all the other blends. The formation of NOX in biodiesel combustion depends on the combustion temperatures and combustion zone oxygen concentration. With high blend ratios of 70/WPPO15/E15, 60/WPPO20/E20, and 50/ WPPO25/E25, the combustion process is shortened, thus leading to failure to provide enough cooling effect to decrease peak combustion temperatures leading

*The concept of employing a NOX absorber with a double SCR layer configuration [109].*

*DOI: http://dx.doi.org/10.5772/intechopen.92569*

*Effects of Biodiesel Blends Varied by Cetane Numbers and Oxygen Contents on Stationary Diesel… DOI: http://dx.doi.org/10.5772/intechopen.92569*

**Figure 22.**

*Numerical and Experimental Studies on Combustion Engines and Vehicles*

tance to diseases such as the common cold and influenza [9, 108].

accurate NO2 and NOX concentration predictions [110–112].

tion as reported by the authors of Refs. [101, 118].

**5.7 Nitrogen oxide (NOX) concentration**

**Figure 21** also shows that as the speed increased, there was a significant increase

NOX concentration and its oxidized product NO2 are the primary preserve of the diesel engine, constituting 85–95% of the total emission of a diesel engine. There are two fundamental differences between the two gases: whereas NOX is odorless and colorless, NO2 is reddish with a pungent smell [107]. It should be mentioned here that NO2 is five times more toxic than NOX gas and is a health hazard to the human respiratory system. It irritates the respiratory system and lowers the resis-

SCR is one of the leading NOX emission control techniques for both LD and HD vehicles. This system entered the market in Japan and Europe for the HD category in 2005 compared to the US market in 2010. In the Japanese market and in Europe, zeolite and vanadium-based catalysts are utilized, respectively. The zeolite SCR catalyst combination performs better and has higher temperature tolerance levels. There is ongoing research to improve low temperature performance for more

The low NOX trap (LNT) is a cheaper option for engines that are 2000–2500 cc [113, 114]. This type of emission control technique works better with mixed-mode engines to reduce low-load NOX that is a persistent problem in SCR systems. This allows the LNT to focus on high temperature NOX that is entering at temperatures over 300°C, thus eliminating between 60 and 70% of the platinum group metals (PGMs) [115]. This makes the LNT technology cheaper and economically appealing to the LD engine classification of 5000–6000 cc capacity [116, 117]. However, for medium- and heavy-duty vehicles, high temperature solutions have been developed to address the challenge of high load requirements of the US NTE regulatory condi-

The LNT technique suffers due to contamination from sulfur, which shortens and affects its service life and durability. Earlier versions of LNT lost 50% filtration capacity, while the current generation of LNTs loses only 25% [119, 120]. Desulfication can be accomplished by passing a rich hot steam of diesel fuel at 700°C for 10 min at service intervals of 5000–10,000 km. **Figure 22** shows a new concept of combining the SCR emission control system with the LNT emission control system. NOX concentration is now known to be temperature dependent due to their equilibrium concentration presence in the combustion chamber. NOX when mixed in high temperature adiabatically in the temperature range of 2000–3000 k forms NOX concentration, which is then exited through the diesel exhaust system [121]. The NOX concentration has four basic mechanisms of formation within the combustion chamber of a diesel engine: the Zeldovich mechanism also called the thermal NOX route, the prompt mechanism, the fuel mechanism, and the NNH mechanism [122]. The variation of engine speed with NOX concentration is shown in **Figure 23**. The graph shows that as the engine speed was increased, there was an increase in the

in the CO2 concentration across all test fuels, although with lower values as the blend ratio increased. For example, CD fuel had values of 2, 3.85, 5.95, and 8.95% for engine speeds of 500, 1000, 1500, and 2000 rpm compared to blend 80/WPPO10/ E10 with 1.8, 2.95, 4.85, and 8.55% for similar speeds. The blend with the lowest value of CO2 emission was 50/WPPO25/E25 with values of 1.62, 2.25, 3.65, and 7.35%, respectively, for engine speeds of 500, 1000, 1500, and 2000 rpm, respectively. The increased carbon concentration in biodiesel blends is due to the reduction in the quantity of carbon relative to the increased oxygen ratio. However, the lower CO2 concentration levels in comparison to CD fuel are due to factors explained under BTE and the equal energy balance generated by the addition of alcohol.

**56**

*The concept of employing a NOX absorber with a double SCR layer configuration [109].*

NOX concentration irrespective of fuel, blend ratio, or additive. However, the value of NOX concentration from the blends 90/WPPO5/E5, 80/WPPO10/E10, and 70/ WPPO15/E15 reported lower values than CD fuel. For example, at 1000 rpm, the value of the blends was 385, 396, and 415 ppm, compared to CD fuel at 425 ppm.

Blends 60/WPPO20/E20 and 50/WPPO25/E25 had the highest NOX concentration compared to the other blends of 90/WPPO5/E5, 80/WPPO10/E10, and 70/ WPPO15/E15 across all the engine speed conditions tested. At 500 rpm engine speed, the two blends had values of 205 and 200 ppm, respectively. At full engine speed (2000 rpm), NOX concentration values increased to 925 and 885 ppm compared to blend 90/WPPO5/E5 at 197 ppm and 792 ppm at full engine speed (2000 rpm). The graph in **Figure 23** shows that as the blend ratio increased, there was a direct increase in the concentration of NOX across all the blended test fuels. However, blend 90/WPPO5/E5 reported the lowest values of NOX concentration compared to all the other blends. The formation of NOX in biodiesel combustion depends on the combustion temperatures and combustion zone oxygen concentration. With high blend ratios of 70/WPPO15/E15, 60/WPPO20/E20, and 50/ WPPO25/E25, the combustion process is shortened, thus leading to failure to provide enough cooling effect to decrease peak combustion temperatures leading to increased NOX.

**Figure 23.** *Oxides of nitrogen versus engine speed.*

These findings seem to show that there is a correlation between the alcohol content in the fuel and peak flame temperatures, content of nitrogen, and oxygen availability [123]. Increased NOX concentration is attributed to the presence of nitrogen from the cetane number improver ENH and other contaminants from the WPPO composition. Additionally, it could be due to the generation of radicals of hydrocarbon through molecular unsaturation being identical to the findings of Refs. [124, 125]. However, the NOX levels are still low, attributed to high CNs of the tested biodiesels in **Table 3** and increased oxygen content due to the blend ratios. These findings are identical to the findings of Ref. [126].
