Variance of engine power and fuel consumption in percent (%) comparing with those parameters before 300 hours durability test of each testing engine is depicted in Fig. 23.23. Where D243-B5 and D243-Do are in turn of the testing engine fuelled with biodiesel B5 and market diesel; D243-B5-150h means the testing engine D243 fuelled with biodiesel B5 after 150 hours. The same definitions are applied for D243-B5-300h, D243-Do-150h and D243-Do-300h.

As shown in Fig. 23.23 the engine power decreased and the fuel consumption increased after 150 hours and 300 hours durability test. Although the differences are not much due to short period running time, there is a clear consensus in the changes of engine power and fuel consumption. The fact that the engine fuelled with biodiesel B5 had lower changes of engine power and fuel consumption after 150 hours and 300 hours durability test is not relevant with other research results which showed higher engine wear when the engine was fuelled with biodiesel.1

Exhaust emissions were measured before, after 150 hours and after 300 hours durability test following R49 driving cycle. Results are given in Fig. 23.24.

It is shown in Fig. 23.24 that none of the emission components meets Euro2 emission standard limits. This reveals somehow the current emission quality of the diesel engine in Vietnam. The emission components HC, CO and PM were risen but NOx depleted with the test period. These results match with the deflection of engine power and fuel consumption as mentioned above, again longer testing period is needed to have better evaluation of engine durability.

Principally, as the wear of engine’s parts increased after a certain time of operation, compression pressure reduced and more combustion products blew to

Emissions deflection (%)

23.23

Deflection in percent of engine power and fuel consumption during 300 hours durability test.

Deflection (%)

23.24 Deflection in percent of emission components during 300 hours durability test.

crankcase, the combustion process of the engine deteriorated causing worse engine’s performance, high hydrocarbon, carbon monoxide and particulate matter were formed, whilst nitrogen oxide reduced due to lower temperature.

There was no damage observed to the engine’s components during 300 hours durability test with biodiesel B5 fuel. The potential coking of the injector was not found as the kinematic viscosity of the biodiesel B5 fuel is almost equal to that of the market diesel. However, this has to be considered with higher biodiesel blends because high viscosity of the biodiesel causes larger fuel droplet sizes. The fuel droplet size is a function of surface tension, density and viscosity. Since the viscosity of biodiesel is high, the fuel droplets are large and hence may not be fully burned. The remaining biodiesel may then decompose at high temperatures (430-480°C) and form deposits.