2. 4 Fuel impact on diesel engines Correct viscosity at the fuel injection pumps gives optimal injection and combustion. Too high or too low preheating temperature causes problems to fuel injection equipment and mechanical loads. It also affects the combustion process. With high density fuel it is advisable to use a high viscosity fuel. Lower CCAD Inadequate preheating will influence combustion, cause increased cylinder wear and may result in too high injection pressure, leading to excessive stress in the fuel oil system
2.4 Fuel impact on diesel engines • Correct viscosity at the fuel injection pumps gives optimal injection and combustion. Too high or too low preheating temperature causes problems to fuel injection equipment and mechanical loads. It also affects the combustion process. With high density fuel it is advisable to use a high viscosity fuel. (Lower CCAI) • Inadequate preheating will influence combustion, cause increased cylinder wear and may result in too high injection pressure, leading to excessive stress in the fuel oil system
2.4 Fuel impact on diesel engines Ignition properties: Poor ignition causes increased ignition delay. Fuel is injected into the cylinder and begins to vaporize and mix with the surrounding air. After a short delay, the heat of compression causes spontaneous ignition to occur, and accumulated vapour formed during the internal injection phase is vigorously burned. This delay between the commencement of injection of the fuel droplets and the moment of spontaneous ignition of the fuel vapour is known as the ignition delay period, and occurs in all diesel engines
2.4 Fuel impact on diesel engines – Ignition properties: Poor ignition causes increased ignition delay. Fuel is injected into the cylinder and begins to vaporize and mix with the surrounding air. After a short delay, the heat of compression causes spontaneous ignition to occur, and accumulated vapour formed during the internal injection phase is vigorously burned. This delay between the commencement of injection of the fuel droplets and the moment of spontaneous ignition of the fuel vapour is known as the ignition delay period, and occurs in all diesel engines
2. 4 Fuel impact on diesel engines Following ignition is a period of controlled e combustion, which maintains pressure on the piston, and is characterized initially by the steady and even combustion for the fuel after injection has terminated. During the ignition phase, the pressure in the engine cylinder rises rapidly and considerable stresses are imposed on the piston. It is desirable to keep the rate of pressure rise as low as possible and this is achieved by ensuring that the minimum quantity of fuel is present in the cylinder prior to the ignition
2.4 Fuel impact on diesel engines • Following ignition is a period of controlled combustion, which maintains pressure on the piston, and is characterized initially by the steady and even combustion for the fuel after injection has terminated. During the ignition phase, the pressure in the engine cylinder rises rapidly and considerable stresses are imposed on the piston. It is desirable to keep the rate of pressure rise as low as possible, and this is achieved by ensuring that the minimum quantity of fuel is present in the cylinder prior to the ignition
2.4 Fuel impact on diesel engines With long ignition delay, a relatively large amount of fuel droplets will have been injected, and thus vaporized in the cylinder by the time ignition occurs. On igniting, this large amount of accumulated vapour will combust almost explosively, leading to sudden and abnormal high rate of pressure rise and high cylinder pressure, beyond that for which engine was designed or can perhaps tolerate. Long ignition delay leads to a sudden pressure rise in the cylinder
2.4 Fuel impact on diesel engines • With long ignition delay, a relatively large amount of fuel droplets will have been injected, and thus vaporized in the cylinder by the time ignition occurs. On igniting, this large amount of accumulated vapour will combust almost explosively, leading to sudden and abnormal high rate of pressure rise and high cylinder pressure, beyond that for which engine was designed or can perhaps tolerate. Long ignition delay leads to a sudden pressure rise in the cylinder
2.4 Fuel impact on diesel engines . Damages: Typical damage that can occur when using fuels with poor ignition properties are: Deterioration in piston ring operation and broken rings. Leakage of gas past the rings (blow by). Deterioration in cylinder lubricant oil film and extreme wear and potential damage to the cylinder liner. cracks and erosion damage to pistons. It is also likely that increased mechanical load over long time can cause damage to bearings
2.4 Fuel impact on diesel engines • Damages:Typical damage that can occur when using fuels with poor ignition properties are: Deterioration in piston ring operation and broken rings. Leakage of gas past the rings (blow by). Deterioration in cylinder lubricant oil film and extreme wear and potential damage to the cylinder liner. Cracks and erosion damage to pistons. It is also likely that increased mechanical load over long time can cause damage to bearings