武汉理工大学：《船舶辅机》课程教学资源（PPT课件，英文版）3.1 fuel and lubricating oil treatment

3.1 fuel and lubricating oi treatment

3.1 fuel and lubricating oil treatment

3.1 fuel and lubricating oil treatment To ensure good combustion in diesel engines and reduce wear and corrosion in this type of engine it may be necessary to remove certain impurities from fuel and lubricating oils These include ash. various salts and water present in fuel oil and carbonaceous matter metals, acids and water present in used lubricating oil carbonaceous

3.1 fuel and lubricating oil treatment • To ensure good combustion in diesel engines and reduce wear and corrosion in this type of engine it may be necessary to remove certain impurities from fuel and lubricating oils. • These include ash, various salts and water present in fuel oil and carbonaceous matter, metals, acids and water present in used lubricating oil. carbonaceous

3.1 fuel and lubricating oil treatment When the impurities are heterogeneous i.e suspended solids or immiscible liquids, they can be removed reasonably successfully by one or more of a number of methods The main methods used at sea are centrifuging filtration and coalescing. Of these three methods centrifuging is the most widely used heterogeneous suspended immiscible coalescing

3.1 fuel and lubricating oil treatment • When the impurities are heterogeneous i.e. suspended solids or immiscible liquids, they can be removed reasonably successfully by one or more of a number of methods. • The main methods used at sea are centrifuging, filtration and coalescing. Of these three methods centrifuging is the most widely used. heterogeneous suspended immiscible coalescing

3.1 fuel and lubricating oil treatment 3.1.1 gravity separation formula It was shown in the section on oil/water separators how liquids with a specific gravity difference can be separated by gravity. The process was expressed mathematically as F_忑D(Po=P)g 6

3.1 fuel and lubricating oil treatment • 3.1.1 gravity separation formula ➢ It was shown in the section on oil/water separators how liquids with a specific gravity difference can be separated by gravity. The process was expressed mathematically as Fs D ( )g 6 3    = −

3.1 fuel and lubricating oil treatment 3.1.2 centrifugal force formula Cleary in a standing vessel the acceleration cannot be altered to enhance the separation force Fs, but by subjecting the operation to centrifugal force the above expression can be replaced by F=D(p。-P)Or where ◆0= angular velocity y=effective radius

3.1 fuel and lubricating oil treatment • 3.1.2 centrifugal force formula ➢Cleary in a standing vessel the acceleration cannot be altered to enhance the separation force Fs, but by subjecting the operation to centrifugal force the above expression can be replaced by where:  = angular velocity  = effective radius F D r s 3 2 ( ) 6     =  − 

3.1 fuel and lubricating oil treatment 3.1.3 Centrifugal force can be great Both the rotational speed and the effective radius are controllable within certain engineering limitations Thus if our standing vessel is replaced by a rotating cylinder the separating force and hence the speed of separation can be increased This effectively is what happens ina centrifuge

3.1 fuel and lubricating oil treatment • 3.1.3 Centrifugal force can be great – Both the rotational speed and the effective radius are controllable within certain engineering limitations. – Thus if our standing vessel is replaced by a rotating cylinder the separating force and hence the speed of separation can be increased. – This effectively is what happens in a centrifuge

3.1 fuel and lubricating oil treatment 3.1.4 batch operation For many years marine centrifuges were designed for batch operation, which is the machines were run for a period during which solids accumulated in the bowl The machine was stopped when the accumulated solids began to impair its performance and the solids were removed

3.1 fuel and lubricating oil treatment • 3.1.4 batch operation – For many years marine centrifuges were designed for batch operation, which is the machines were run for a period during which solids accumulated in the bowl. – The machine was stopped when the accumulated solids began to impair its performance and the solids were removed

3.1 fuel and lubricating oil treatment 3.1.5 Lub. Oil batch centrifuging Batch centrifuging is still commonly used especially for lubricating oil purification, but many machines capable of continuous or semi-continuous sludge discharge are now at sea Two distinct types of batch operated machines have een used These are illustrated in Figure 3. 1 and classified in Table 3.1

3.1 fuel and lubricating oil treatment • 3.1.5 Lub. Oil batch centrifuging – Batch centrifuging is still commonly used especially for lubricating oil purification, but many machines capable of continuous or semi-continuous sludge discharge are now at sea. – Two distinct types of batch operated machines have been used. – These are illustrated in Figure 3.1 and classified in Table 3.1

LIGHT PHASE: LIGHT: PHAS IFEED → HEAVY PHASE FEED TUBULAR BOWL DISC TYPE ROTOR TYPE ROFOR. Figure3.1

Figure 3.1 Figure 3.1

3.1 fuel and lubricating oil treatment Table 3.1 Details of tubular and disc type centrifuges used for batch treatment ofliquids Maximum Bowl dia Length/dia Ive force (mm Batch tubu Bowl 130002000 g Up to180 Up to 7 Bowl suspended from above ty Batch dr 50008000*g Up to, say 600 Generally (1 Bowl supported form below type

3.1 fuel and lubricating oil treatment Maximum centrifugal force Bowl dia. (mm) Length/dia. (of bowl) Drive Batch tubular Bowl type 13,000–20,000 * g Up to 180 Up to 7 Bowl suspended from above Batch disc bowl type 5,000–8000 * g Up to, say 600 Generally ‹1 Bowl supported form below Table 3.1 Details of tubular and disc type centrifuges used for batch treatment of liquids