**3. Result and discussions**

Performance, emissions and combustion characteristics of blends B10, B20, B30, B40 and B50 with conventional diesel are investigated on single cylinder computerized diesel engine and are discussed in the following subsections.

#### **3.1 Brake thermal efficiency, brake-specific fuel consumption, and exhaust gas temperature**

**Figure 2a** shows that the variation of brake thermal efficiency (BTE) with a load for different blends. It has been observed that the brake thermal efficiency for all test fuel is increasing with the increase in applied load. It happens due to a reduction in heat land increase in power developed with an increase in load [22]. Blend B30 and diesel has been shown the BTE of 33.75 and 34.57% respectively. Hence B20 gave the little difference in efficiency among all test fuel, which is about 0.82% less than the diesel. Initially, efficiency was found to be increased with increased blend ratios up to B30 and after that, it got a decrease as shown in **Figure 2a**. The decrease in brake thermal

**Figure 2.** *Variation of brake power with (a) BT efficiency and (b) BSFC.*

efficiency for higher blends may be due to the combined effect of its lower heating value and increase in fuel consumption [23]. In spite of this increasing viscosity may be the other reason for decreasing efficiency with higher blend ratio fuel, thereby, poor pray and poor atomization occurred due to which charge was not properly burned.

The variation of brake specific fuel consumption with regard to load is given in **Figure 2b**. It is obvious from the name that the BSFC of the engine gradually decreases with increasing load and then becomes constant up to full load condition. The same trend for brake specific fuel consumption (BSFC) can be viewed as it was seen in efficiency **Figure 2**; B30 has given lowest brake specific fuel consumption to all other blends and diesel at full load condition [24–28]. Diesel and B30 have been read 0.25 and 0.25 kg/kWh of BSFC respectively, at full load which is more or less same as diesel. For a higher percentage of biodiesel blends, BSFC is found to be increased. This may be due to high density, high viscosity and lower heating value of the fuels. B30 has a minimal value of fuel consumption among B10, B20, B50, and B100 at and above 100% load.

#### **3.2 Results and discussion regarding the engine emission in term CO, CO2, NOx, and unburned HC are as follows**

#### *3.2.1 Carbon monoxide (CO) emission*

The figure shows the variation of carbon monoxide emission of blends and diesel under various loads. The discharge of CO is found to be diminished with increasing load at the initial stage up to approximate 75% load after that it increases for B10 up to 0.2 (%Volume). But for B30 decrement of 0.2 (%Volume) of CO at the stage of 75–100% load. This is because of more fuel accumulates at a higher load to produce more power due to which higher temperature achieved in the fumes. This increased temperature helps in the oxidation of CO on account that its value decreases. Blend B10, B20, B50, and B100 have been given equal amount of CO to that of diesel at full load stage, because for B10 due to the inefficient inherited oxygen of biodiesel CO could not oxidize to CO2, and for B50 increased viscosity and high non-volatility of biodiesel caused poor spray, atomization and burning of CO into CO2 (**Figure 3**).

#### *3.2.2 Hydrocarbon emission*

Variation of unburned hydrocarbon can be seen in the figure. Significant reduction in HC emission has been found with decreasing the blend ratio of biodiesel in fuel. Blends B10, B20, B30, B50, B100 and diesel are given 36.5, 34.8, 30.2, 23, 23.2 and 27.4 ppm of HC emission on an intermediate basis. Hence B50 and B100 have been given the lowest HC compare to all test fuels due to the optimum level of oxygen and viscosity of the fuel. This decrease indicates that more complete combustion of fuels due to which low HC level was obtained (**Figure 4**).

#### *3.2.3 NOx emission*

Variations of NOx emission with loads for different blends are presented in the figure.

The NOx emission is found to be increased with growth in shipment due to less heat rejection at higher load. That is the way all test fuels shows the highest value of discharge at full load condition. Blends B10, B20, B30, B50, B100 and diesel show 549, 743, 608, 704, 669, and 730 ppm respectively at full load condition. In initial blends, only B20 has been given higher. NOx due to higher temperature compared to B10 and B20. In universal, vegetable-based fuel contains a low quantity of

*Performance, Emissions, and Combustion Evaluations of a Diesel Engine Fuelled with Biodiesel… DOI: http://dx.doi.org/10.5772/intechopen.83845*

**Figure 3.** *CO vs. BP emission for Mahua oil BD blends and diesel.*

**Figure 4.** *BP vs. unburned HC for Mahua oil BD blends and diesel.*

**Figure 5.** *BP vs. NOx for Mahua oil BD blends and diesel.*

nitrogen that contributes towards NOx production. In malice of this NOx emission is the function of temperature also, more NOx is emitted at high load because of the higher temperature of gas oxidized the nitrogen oxides into nitrogen and thus NOx increase. From this figure, it can be concluded that B20 exhibiting proper complete combustion compare to others fuels (**Figure 5**).

### *3.2.4 CO2 emission*

Percent of CO2 in the exhaust is the direct indication of complete combustion of fuel in the combustion chamber. The figure shows the variation of CO2 under varying load for different biodiesel blends. All test fuels show increasing trends, CO2 emission with an increase in shipment due to an increase in the accumulation of fuel. Blends B10, B20, B30, B50, B100 and diesel shows 3.6, 4, 3.7, 4.2, 3.7 and 4.5% of CO2 respectively at full load condition. Only B50 has been shown higher CO2 emission compare to diesel due to the significant issue of higher cetane number compare to other test fuel. Other blends have been presented the lower value of CO2 than diesel. It can also be cleared from exhaust gas temperature vs. load curves in which B50 has been shown a higher temperature than other blends (**Figure 6**).

### *3.2.5 Combustion analysis*

Combustion characteristics parameter like pressure-crank angle, rate of cylinder pressure rise, heat release rate and cumulative heat release are analyzed for different blends of Soybean oil biodiesel under varying load to compare the combustion characteristics of the engine with conventional diesel fuel.

#### *3.2.5.1 In-cylinder pressure vs. crank angle*

The figure shows the variation of in-cylinder pressure with a crank angle for blends B10, B20, B30, B50 and B100 in comparison of baseline data obtained from standard diesel. Pressure rise has been found to be comparable with diesel for higher biodiesel blends fuel. Moreover, low biodiesel blends such as B10 and B20 show delayed pressure rise with respect to standard diesel at full load due to longer physical ignition delay period because of the higher boiling point range of biodiesel compared to diesel. It can as well be visualized in the figure that all test fuel has shown decreases in ignition delay with an increase in shipment. This was passed due to an increase in gaseous state temperature at high load operation; therefore, a reduction in the physical ignition delay period was held (**Figure 7**).

I all cases higher biodiesel blends as B100 and B50 has been shown higher incylinder peak pressure compared to diesel and other low biodiesel blends. Two elements are mostly responsible for that first presence of inherited oxygen molecules

**Figure 6.** *BP vs. CO2 for Mahua oil BD blends and diesel.*

*Performance, Emissions, and Combustion Evaluations of a Diesel Engine Fuelled with Biodiesel… DOI: http://dx.doi.org/10.5772/intechopen.83845*

**Figure 7.** *In-cylinder pressure vs. crank angle.*

in biodiesel helps in combustion and the second is the lower viscosity of mineral diesel which ensures adequate air-fuel blending.

#### *3.2.5.2 Rate of cylinder pressure rise vs. crank angle*

The figure shows the variation in the rate of pressure rise (dP/dθ) with a crank angle (θ) under varying load for all test fuels. It can as well be visualized in the figure that the maximum rate of pressure rise is 4.55 bar/deg. for B30 blend and 4.51 bar/deg. for B20 blend, biodiesel blend B20 has been shown the highest rate of pressure rise compares to diesel. It can be due to higher accumulation of fuel during premixed combustion on account of that B20 biodiesel blends showed the earlier start of combustion with a consequence high rate of pressure rise (**Figure 8**).

#### *3.2.5.3 Heat release rate vs. crank angle*

The figure shows the heat release rate for biodiesel blends in comparison of standard diesel at different engine operating conditions. After burning of fuel, fluctuation of heat release rate occurs. However, at B100 shows the highest rate of heat release compare to diesel and other biodiesel blends are two other blends, because of the higher cetane number and higher oxygen capacity of biodiesel that improves

**Figure 8.** *Pressure rise rate vs. crank angle.*

**Figure 9.** *Heat release rate vs. crank angle.*

the burning quality of fuel and helps in firing at a higher charge per units. Moreover B10, B20 and B50 have been established a corresponding rate of heat release with diesel. This is because in low blends the concentration of biodiesel is low, that is way fuel does not cause a significant force on a certain number, but it touches the air-fuel mixture formation due to changes in viscosity and evaporation properties of the fuel. That is way lower blends showed a less charge per unit of heat release than B100 (**Figure 9**).

#### *3.2.5.4 Cumulative heat release vs. crank angle*

Cumulative heat release is the total heat energy that has been dropped for a given production. The figure shows the cumulative heat release for all blends at various engine loads in comparison of diesel. It can be pictured in figures that cumulative heat increases with increasing engine load for all test fail because the bulk of the fuel increases with a gain in shipment. It is also cleared from the diagram that up to 40% load all blends show low cumulative heat compare to diesel, but after that, blends have been shown gradually increase in cumulative heat than diesel in which B30, B50, and B100 show high cumulative heat.

### **4. Conclusions**

High acid value Mahua oil was used to produce biodiesel by a two-step process of esterification followed by transesterification. In etherification, the molar ratio of methanol to oil and quantity of sulfuric acid was two main reaction parameters which were optimized to produce a low acid value of oil. Molar ratio 18:1 and 0.8% w/w to oil of sulfuric acid was observed optimum reaction parameters. While reaction temperature, reaction time and a stirrer speed of 60°C, 1 h and 300 rpm respectively were maintained during esterification. For transesterification, the molar ratio of alcohol to oil of 6:1, 9.9 g of catalyst (KOH), 60°C temperature, 1 h reaction time and stirring speed 1300 rpm were used.

The performance, emission and combustion characteristics of an engine fuelled with crude Mahua oil biodiesel and diesel blends were investigated and compared with that of standard diesel. The experimental results confirm that the BTE, BSFC, exhaust gas temperature is the function of biodiesel blend and load. For similar operating conditions, a particular blend gave better engine performance and reduced emissions compared to other blends in comparison of standard diesel. B30 of Mahua oil biodiesel blend gave the better overall performance among all other blends in comparison of diesel. However, Mahua oil gave 33.75% BTE for B30,

#### *Performance, Emissions, and Combustion Evaluations of a Diesel Engine Fuelled with Biodiesel… DOI: http://dx.doi.org/10.5772/intechopen.83845*

which is less compared to diesel, the increased value of BSFC reduced CO, HC, NOx and CO2 emissions with high-value smoke which indicates better combustion of fuel, which can be considered as acceptable results in overall performance with biodiesel without any modification of engine. In combustion characteristics, higher blends showed the earlier start of combustion and for lower blends start of combustion was slightly delayed in comparison of standard diesel. Almost identical trends were to be seen for all the biodiesel blends in heat release rate. The very negligible difference was seen in combustion duration for blends and diesel however under full load condition, blends showed insignificant shorter duration of combustion than diesel. Therefore, Mahua oil biodiesel blends, B30 can be used in unmodified CI engines.
