**4. Emission characteristics of HDRD in CI engines**

Kim et al. [34] reported the outcomes of the exhaust test carried out on a passenger car with an intercooler fueled with unblended HDRD and compared the results with when PBD fuel was used. They reported a reduction in particulate matter (PM), nitrogen oxide (NOx), carbon monoxide (CO), and total hydrocarbon content (THC) emissions. They attributed these results to the properties of HDRD which allows more complete combustion. Mangus et al. [33] also reported the same pattern of results affirming that the CI engine fueled with HDRD emits less NOx, CO, PM, and THC than when the same engine is fueled with PBD fuel under the same engine speed and load. In another research, da Costa et al. [39] reported that a single cylinder power generation CI engine operated with HDRD synthesize from sugarcane emitted less CO, HC, NOx, and PM when compared with PBD fuel. The same pattern of results was reported by Ogunkoya et al. [32], Vojtisek-Lom et al. [40], and Na et al. [41] who, in their separate studies, affirmed that CI engines fueled on HDRD emitted less CO, CO2, HC, NOx, and soot.

However, Karavalakis et al. [42] and Gysel et al. [43] reported a slight increment in the CO, CO2, NOx, and PM emissions in their studies, as shown in **Table 5**. The higher PM was attributed to the higher cetane number of the tested HRDR fuel which promoted the growth of the diffusive combustion. The higher NOx and PM emissions eliminate the benefits of the aromatic-free characteristics associated with using HDRD fuels. The emission of two greenhouse gases, CO2 and N2O were found to be lower with the use of HDRD. This is one of the benefits of the application of HDRD in CI engines. Janarthanam et al. [35] studied the emission characteristics of compared the engine performance of a vertical single cylinder, four strokes, 4.3 kW Kirloskar fueled with HDRD and biodiesel. They reported lower emissions of CO, HC, NOx, and smoke due to higher methyl esters and oxygen contents of the tested HDRD. Similarly, Singh et al. [36], compared the performance of HDRD with biodiesel and PBD blends in a single cylinder, four strokes 3.5 kW direct injection water-cooled test rig at various engine loads. They reported that HDRD generates lower CO, UHC, and smoke but higher NOx emission compared with biodiesel and PBD and their blends (**Figure 7**). Reduction in CO, CO2, and smoke emissions were due to higher oxygen content and cetane index of HDRD while the increment in NOx emission was attributed to the higher cetane index, ignition delay, higher cylinder temperature, and pressure as compared to biodiesel and PBD [36]. When HDRD and biodiesel blends


*Performance and Emission Characteristics of Hydrogenation Derived Renewable Diesel… DOI: http://dx.doi.org/10.5772/intechopen.104820*


↑ *= increased,* ↓ *= reduced, L = liters, C = Cylinder, S = Stroke, DI = Direct injection, NA = Naturally aspirated, AC = aircooled, WC = water-cooled.*

#### **Table 5.**

*Emission characteristics of CI engine fueled with HDRD.*

**Figure 7.** *Emission characteristics of HDRD at various engine loads [36].*

**Figure 8.** *NOx and PM emissions of HDRD [44].*

were tested a six-cylinder, 6.37 L Mercedes-Benz CI engine equipped with a turbocharger and intercooler, HDRD generated less NOx but more PM emissions. The NOx and PM emissions generated from HDRD were found to be lesser than that from PBD and within the acceptable Euro III limit, as shown in **Figure 8** [44].

Similarly, light and heavy duty CI engines were fueled with HDRD and PBD fuels blends across various engine loads. The light duty engine was fixed a single cylinder, common rail, Ricardo Hydra, and Volvo NED4 cylinder head engine while the heavy duty engine consisted of a single cylinder, common rail, AVL 501, and Volvo D13 cylinder head. The outcome of the emission characteristics showed HDRD a slight increment in NOx emission and reduction in PM and soot emissions for both engine types fueled with HDRD across tested engine loads [37]. Shepel et al. [38] reported a reduction in CO, smoke, HC, and NOx emissions when HDRD was tested in a 4 cylinder, direct injection, water cooled, 66 kW, 1.9 TDI diesel engine test blend and the results compared with biodiesel fuel. There was, however an increment of 8% in CO2 emission which was a result of the higher oxygen content of HDRD compared to other tested fuels. Similar results were obtained when Dobrzyńska et al. [45] tested both HDRD and PBD fuels on a Euro 3, 51 kW Fiat Panda vehicle. They recorded a 27% reduction in HC, 30% in NOx, 18%, in CO, 3% in CO2, and 5% in PM emissions. They concluded that the adoption of HDRD as fuel for CI engines, particularly in the transport sector will reduce the emission of environmentally hazardous gasses, ensure cleaner air quality, and ultimately improve human health.

*Performance and Emission Characteristics of Hydrogenation Derived Renewable Diesel… DOI: http://dx.doi.org/10.5772/intechopen.104820*
