2. 4 Fuel impact on diesel engines The main objective of this section is to make you acquainted with the relevance of fuel parameters on: Abnormal ignition and combustion. Wear, piston ring collapse and breakage. Gas leakage. Ignition, combustion and exhaust gas emission. Engine damages and operational problems. Prevention of engine damages with off spec fuels and to recognize their impact on the operation of marine diesel engines. Abnormal ignition and combustion
2.4 Fuel impact on diesel engines The main objective of this section is to make you acquainted with the relevance of fuel parameters on: Abnormal ignition and combustion. Wear, piston ring collapse and breakage. Gas leakage. Ignition, combustion and exhaust gas emission. Engine damages and operational problems. Prevention of engine damages with off spec. fuels and to recognize their impact on the operation of marine diesel engines. • Abnormal ignition and combustion
2.4 Fuel impact on diesel engines Density: Density of a fuel oil decreases with rise in temperature. The density has no direct importance for the engine operating condition, but a high density indicates that a fuel contains heavy or complex hydrocarbons. high density can lead to slow combustion and an increased degree of late combustion slow combustion and late combustion will have the following effects on the engine: Increased metal temperature(increased thermal loads Reduced efficiency and thereby, increased specific fuel consumption, increased exhaust temperature increased tendency for fouling, increased wear due to thermal overload of the oil film on the liners
2.4 Fuel impact on diesel engines – Density: Density of a fuel oil decreases with rise in temperature. The density has no direct importance for the engine operating condition, but a high density indicates that a fuel contains heavy or complex hydrocarbons. High density can lead to slow combustion and an increased degree of late combustion. Slow combustion and late combustion will have the following effects on the engine: Increased metal temperature (increased thermal loads). Reduced efficiency and thereby, increased specific fuel consumption, increased exhaust temperature, increased tendency for fouling, increased wear due to thermal overload of the oil film on the liners
2. 4 Fuel impact on diesel engines Viscometers, regulators: Viscosity is a measure of resistance to flow and is not an indication of the fuel quality. Automatic viscosity controllers are recommended in order to obtain constant viscosity regardless of engine fuel demands. It is of great importance to know the viscosity in order to select the right temperature to ensure that the fuel oil viscosity is correct for atomization. The viscosity meter is installed in the fuel supply line, to ensure the right viscosity regardless of the consumption
2.4 Fuel impact on diesel engines – Viscometers, regulators: Viscosity is a measure of resistance to flow and is not an indication of the fuel quality. Automatic viscosity controllers are recommended in order to obtain constant viscosity regardless of engine fuel demands. It is of great importance to know the viscosity in order to select the right temperature, to ensure that the fuel oil viscosity is correct for atomization. The viscosity meter is installed in the fuel supply line, to ensure the right viscosity regardless of the consumption rate
2.4 Fuel impact on diesel engines Viscosity depends on the fuel oil temperature, (decreases with increasing temperature), but will not change by fuel treatment. Due to the cracking process, heavy fuel oil viscosity can not be used to indicate oil quality. Fuel oil viscosity is important for determining the preheat temperature in order to reach the correct viscosity at the injection pumps. Typical values at injection is in the range 10 to 20 cst
2.4 Fuel impact on diesel engines Viscosity depends on the fuel oil temperature, (decreases with increasing temperature), but will not change by fuel treatment. Due to the cracking process, heavy fuel oil viscosity can not be used to indicate oil quality. Fuel oil viscosity is important for determining the preheat temperature in order to reach the correct viscosity at the injection pumps. Typical values at injection is in the range 10 to 20 cst
able 2. 4 Viscosity/temperature relations viscosity /temperature relations: Pumping viscosity, Kinematic viscosity, Centistokes ==|380 usually about 1.000 cSt 1000 500 100 Boiler atomisation usually between 15 and 60 cst 15 DIesel injection Viscosity usually between 8 and 27 cSt. 515 30405060708090100110120130140150160170 Temperature- degrees celcius
Table 2.4 Viscosity/temperature relations