Tài liệu Diezel 1410 P5

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Tài liệu Diezel 1410 P5

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Normally, diesel fuel oils for use in the Submarine Service are purchased by the Bureau of Supplies and Accounts.

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  1. 5 DIESEL ENGINE FUEL SYSTEMS A. DIESEL FUELS 5A1. General. Normally, diesel fuel stopped at any point, leaving a residue of oils for use in the Submarine Service a heavier viscous liquid. This residue are purchased by the Bureau of may be cracked in cracking stills by the Supplies and Accounts. At the time of application of heat and pressure in the delivery, the diesel fuel oils are presence of a catalyst. This cracking inspected to make sure that they meet process may be controlled so as to get the specifications set up by the Bureau products of almost any given type of of Ships. However, emergencies hydrocarbon molecular structure. The occasionally arise both in the supply products mostly desired are those that and in the handling of diesel fuels that can be used as gasoline and fuel oil make it imperative for operating blends. engineering personnel to have at least a fundamental knowledge of the Fuel oils that meet the specifications for requirements for diesel fuel oil. high-speed diesel engine operation are of two types, distillate and blended. The distillate type is obtained by the direct 5A2. Cleanliness. One of the most important properties necessary in a distillation of crude oil only. Blended diesel fuel oil is cleanliness. Impurities type is obtained by blending the distillate are the prime sources of fuel pump and with the residual products from the injection system trouble. Foreign cracking stills. As a general rule, substances such as sediment and water distillate fuel oil is superior to blended cause wear, gumming, corrosion, and fuel oil for high-speed diesel operation rust in the fuel system. Diesel fuel oil because it possesses better ignition should be delivered clean from the quality, has a lower carbon content, and refinery. However, the transfer and contains fewer impurities. handling of the oil increase the chance of its picking up impurities. The American crude oils are classified into necessity for periodic inspection, three types: paraffin base, asphalt base, cleaning, and care of fuel oil handling and mixed base. These three and filtering equipment is emphasized classifications depend upon whether under the subject of maintenance for paraffin waxes, asphalt, or both remain each system. after all the removable hydrocarbons have been distilled from the petroleum. 5A3. Chemistry of diesel fuel oil. Diesel fuel oils are derived from 5A4. Differences in internal petroleum, more generally known as combustion fuels. The two principal crude oil. All crude oils are composed types of internal combustion fuels are of compounds of carbon and hydrogen gasoline and diesel fuel oil. Both types known as hydrocarbons. The structure are hydrocarbons, but the hydrocarbons of the oil is made up of tiny particles differ radically in their chemical called molecules. In crude oil, a composition. molecule consists of a certain number of atoms of carbon and a certain Gasoline is a fuel adapted to spark number of atoms of hydrogen. The ratio ignition, while diesel fuel oil is adapted between carbon and hydrogen atoms in to compression ignition. In spark a molecule determines the nature of the ignition, the fuel is mixed with crude oil. combustion air before the compression stroke. In compression ignition, the fuel Crude oil is separated into various is injected into the combustion air near products by a process known as the end of the compression stroke. Thus a
  2. fractional distillation. In general, each spark-ignition fuel must have a certain product is obtained at its particular amount of resistance to spontaneous boiling point in the distillation process. ignition from compression heat. The The relative order of products obtained, opposite holds true for diesel fuel oils. Entirely different ignition properties are with their distillation temperature is: required of the two fuels. Gasoline-100 degrees to 430 5A5. Properties of diesel fuel oils. The degrees F following are the chief properties Kerosene-300 degrees to 500 required of diesel fuel oils. With the degrees F definition of each Fuel oil-400 degrees to 700 degrees F Lubrication oil-650 degrees F The fractional distillation process may be 91 property is an explanation of its reference fuel that produced the same application to engine operation. standard delay period with the same compression ratio. For example: if the reference fuel required 60 percent cetane a. The ignition quality of a diesel fuel oil is the ease or rapidity with which it and 40 percent alpha-methyl naphthalene to produce the same standard delay will ignite. period at the same compression ratio as A diesel fuel with good ignition quality the diesel fuel oil tested, then the cetane rating of the diesel fuel oil is 60. will auto-ignite (self-ignite) at a relatively low temperature. In simple NOTE. The cetane rating for gasoline language the fuel will ignite quickly indicates low ignition quality while and easily under relatively adverse conditions. Thus, where diesel engines cetane rating for diesel fuel oil indicates relatively high ignition quality. Cetane must be started at low temperatures, numbers of diesel fuels in use today good ignition quality makes starting range from about 30 for engines least easier. critical to fuel to over 60 for the highest ignition quality fuels. Poor ignition quality will cause an engine to smoke when operating under a light load at a low temperature. It will 2. Diesel index. This method of determining ignition quality is obtained also often cause the engine to knock by a simple laboratory test. This test and overheat due to the accumulation takes into account the fact that there is a of fuel in the cylinder between the definite relationship between the physical injection and ignition period. The and chemical properties of diesel fuel oils sudden ignition of accumulated fuel and their ignition quality. The diesel causes the knock. index number method is based on the There are two widely accepted methods relation between the specific gravity of of determining the ignition quality of a the fuel oil and the aniline point, which is the temperature in degrees Fahrenheit at diesel fuel oil which equal quantities of the fuel oil and 1. Cetane number test. In this method a aniline (a chemical derived from coal tar) standard reference fuel is used in a test will dissolve in each other. To obtain the diesel index number, the gravity of the cylinder. The most widely used fuel oil, in degrees API, is multiplied by reference fuel is a mixture of cetane and alpha-methyl-naphthalene. Cetane the aniline point and divided by 100. The
  3. has an extremely high ignition quality result is the diesel index number of the (ignites quickly) and is rated for the test fuel. at 100. Alpha methyl-naphthalene has a very low ignition quality (is difficult to While the diesel index method is ignite) and is rated for the test at 0. accepted as a fairly reliable method of determining the ignition quality, the The single-cylinder test engine used is cetane number test is considered more like any diesel engine cylinder, except accurate. Hence it is preferable to use the that the compression ratio of the cetane number test where possible. It cylinder is adjustable. Other cylinder must be remembered, however, that the conditions, including the delay period, diesel index test possesses the advantage that is, the interval between injection of simplicity and low cost. The normal and ignition, are held constant. This range of diesel index is from below 20 to delay period is measured by electrical about 60 for diesel fuels in use. equipment. The fuel to be tested is used in the test cylinder and the compression b. Specific gravity. The specific gravity ratio is adjusted until the standard of a diesel fuel oil is the ratio of its length delay period is reached. Fuel weight to the weight of an equal volume with high ignition quality requires a of water, both having the same low compression ratio. Fuel with low temperature of 60 degrees F. The specific ignition quality requires a high gravity of the majority of diesel fuel oils compression ratio. ranges from 0.852 to 0.934. As a matter of convenience and to standardize Next the reference fuel is used in the reference, the American Petroleum cylinder. Using the same compression Institute has established the API gravity ratio, various mixtures or proportions scale calibrated in degrees for diesel fuel of cetane to alpha-methyl-naphthalene oil are used until the standard length delay period is attained. The cetane number of the diesel fuel oil tested is then equal to the percentage of cetane in the 93 gravities. Lighter weight fuel oils have heat value than a pound of the heavy oils, high numbers (about 20 degrees to 40 a gallon of the former is generally lower degrees) and heavier weight fuel oils in heat value than a gallon of the latter. have low numbers (from 10 degrees up The difference, however, in the normal to about 20 degrees). range of diesel fuels is relatively small. For example, a 24 degrees API diesel fuel has approximately 3 percent greater Diesel fuel oils are generally sold by volume. Hence the specific gravity of a heating value per gallon than a 34 degrees API fuel. Considering the many fuel oil plays an important part factors related to gravity which may commercially. Knowing the specific gravity, temperature, and quantity of a affect over-all thermal efficiency, the effect of this difference on fuel economy fuel oil, the volume can easily be is usually negligible. computed from standard tables. The specific gravity of a diesel fuel oil is often referred to, but its significance is e. Flash point. The flash point of an oil is frequently overestimated. Efforts have the lowest temperature at which a flash been made at various times, but with appears on the oil surface when a test little success, to establish a definite flame is applied under specified test relationship between gravity and other conditions. It is a rough indication of the characteristics such as viscosity, boiling tendency of the product to vaporize as it is heated. The flash point is important
  4. primarily with relation to regulations point, and ignition quality. covering handling and storing of inflammable liquids. It is of little c. Viscosity. The viscosity of a fluid is importance to diesel fuel oil the internal resistance of the fluid to performance. Most diesel fuels have a flow. The viscosity of a fuel oil is flash point well above 180 degrees F. determined by the Saybolt Universal The minimum flash point required by Viscosimeter test. In this test, a Navy specifications is 150 degrees F. measured quantity of the fuel oil is allowed to pour by gravity through an opening of established diameter and f. Pour point. The pour point of a diesel with the fuel oil at an established fuel is the temperature at which the fuel temperature, usually 100 degrees F. congeals and will no longer flow freely. The length of time in seconds required This is usually due to the presence of for the given quantity of fuel oil to pass paraffin wax, which crystallizes out of through the opening determines its the fuel at low temperatures. Pour point usually determines the minimum viscosity. temperature at which the fuel can be handled, although in some cases, where Viscosity is important in diesel fuels there is considerable agitation preventing because of its effect on the handling the crystallization of wax, the fuel will and pumping of the fuel, and on the injection of the fuel. Viscosity, together usually flow at temperatures below the pour point. with the rate of fuel consumption, determines the size of fuel lines, filters, and fuel pumps. The efficiency of g. Carbon residue. The carbon residue of filtering is greatly increased in a fuel oil diesel fuels is usually determined by the of lower viscosity. In the injection Conradson test, in which the fuel is system viscosity affects the burned in a covered dish. The carbon characteristics of the fuel spray at the remaining is weighed and expressed as a injection nozzles. It also affects the percentage of the fuel. The test provides amount of leakage past pump plungers a rough indication of the amount of high- and valve stems, and therefore the boiling heavy materials in the fuel, and is lubrication of the various types of particularly useful where, because of high boiling points, distillation data valves and pumps. cannot be obtained. Carbon residue is d. Heating value. The heating value of sometimes taken as an indication of the a diesel fuel oil is its ability to produce tendency of the fuel to form carbon in the a specific Btu output of heat per unit of combustion chamber and on the injection nozzles, although there is a little basis for weight or volume. There is a definite relation between the gravity of a diesel using the test for this purpose due to the difference in the method of combustion fuel oil and the Btu content. The used in the test and that actually relationship is approximately: encountered in an engine. Btu per pound of fuel = 17,680 + 60 x API gravity. It is well to remember that although a pound of the lighter grades of oils has a higher 94 h. Sulphur content. The sulphur content sediment to separate. The percentage by of a diesel fuel includes both volume is then determined. noncorrosive and corrosive forms of sulphur. If the sulphur content is high, The presence of water and sediment is
  5. the copper strip corrosion test should be generally an indication of contamination made to determine whether or not the during transit and while handling. Fuel sulphur is in corrosive form. If sulphur containing water and sediment causes in corrosive form is present, a sample corrosion and rapid wear in fuel pumps of the oil should be sent to the nearest and injectors. laboratory facility for a test to determine the percentage present. 5A6. Engine troubles caused by fuel. Sulphur in excess of Navy maximum As indicated in the discussion of diesel specifications is likely to damage the fuel oil properties, any number of engine engine. When the fuel is burned, the troubles may be caused by unclean or sulphur is combined with oxygen to poor fuel oil. Some of the more common form sulphur dioxide which may react troubles are: with water produced by combustion to form sulphuric acid and cause a. Carbon deposits at injection nozzles excessive cylinder wear. It will also act may be due to excess carbon residue or to corrode other internal engine parts. excessive idling of engine. i. Ash content. The ash content of a b. Excess wear of injection pumps and diesel fuel oil is the percent by weight nozzles may be due to too low a of the noncombustible material present. viscosity, excess ash content, or This is determined by burning a corrosion from water or sulphur content quantity of fuel of known weight and in the fuel oil. weighing the ash residue. Ash is an abrasive material and the presence of c. Exhaust smoke may result when a fuel ash above the maximum amount with too high an auto-ignition allowed by Navy specifications will temperature is used. This is particularly have an obvious wearing effect on true at light loads when engine engine parts. temperatures are low. j. Water and sediment. The percent by d. Combustion knock in a diesel engine is volume of water and precipitable believed to be due to the rapid burning of sediment present in the fuel oil is a large charge of fuel accumulated in the determined by diluting a quantity of cylinder. This accumulation is the result fuel oil with an equal quantity of of nonignition of fuel when it is first benzol, which is then centrifuged, injected into the cylinder, a condition causing water and usually caused by fuel oil of poor ignition quality. B. SHIPS FUEL SYSTEM 5B1. General. The engineering exception of the clean fuel oil tanks installation on present fleet type which are inside the pressure hull. submarines consists of four main engines and one auxiliary engine. The two main piping systems found in These are divided between two engine the main fuel-oil system are the fuel oil rooms, with two main engines in the filling and transfer line and the fuel oil forward engine room, and two main compensating water line. These lines engines and the auxiliary engine in the connect to the various tanks and give the after engine room. The function of the fuel oil system a flexibility which it ship's fuel oil system is to supply clean otherwise would not have. fuel oil to each engine from the ship's storage tanks. The system may be 5B2. The compensating principle. In divided into two parts: 1) the tanks and order to understand the operation of a their arrangement, and 2) the different submarine fuel system, it is important to piping systems. know the basic fuel oil compensating
  6. principle. In a submarine, to assist in maintaining trim it is necessary to have The tanks include normal fuel oil tanks, as little weight change as possible when fuel ballast tanks, clean fuel oil tanks, fuel is being used m a fuel tank. expansion tank, and collecting tank. All Therefore, a compensating system is used of these tanks are in the spaces between which allows salt water to replace fuel oil the inner pressure hull and the outer as the fuel oil is taken from a tank. Let us hull of the submarine with the assume that the weight of fuel 95 used is 7.13 pounds per gallon and the c. Collecting tank. The collecting tank is weight of salt water is 8.56 pounds per one side of a section of tank space gallon. Therefore, when one gallon of between the inner and outer hulls, the fuel is used from a fuel tank, instead of other side being the expansion tank. This the submarine-becoming light by 7.13 tank has a connection to the fuel oil pounds, it becomes heavy by 8.56 - filling and transfer line. All of the fuel 7.13 or 1.43 pounds. The submarine, used by the engines normally passes then, becomes heavy as fuel oil is used. through the collecting tank. A connection This compensating principle is used in from the top of the collecting tank leads the normal fuel oil tanks, fuel ballast to the fuel oil meters, fuel oil purifiers, tanks, expansion tank, and collecting clean fuel oil tanks, and eventually to the tank. These tanks must at all times be attached fuel oil pumps on the engines. filled with a liquid, either fuel oil, sea This tank has a capacity of about 3,000 water, or a combination of both. The gallons, and on submarines is located compensating principle is not used in outboard of the forward engine room. the clean fuel oil tanks. The main function of the collecting tank is to insure that no large amount of water gets to the purifiers, clean fuel oil tanks 5B3. Fuel oil tanks. a. Normal fuel and engine until all the fuel in normal tanks. The normal fuel tanks are used only for the storage of fuel oil. They are fuel oil tanks, fuel ballast tanks, expansion tank, and collecting tank has usually located toward the extremities been used. of the boat rather than close to amidships. They vary in size, but normally have capacities of from d. Expansion tank. The expansion tank is 10,000 to 20,000 gallons each. Most alongside and on the opposite side of the modern submarines have four of these ship from the collecting tank. It is tanks. In a typical installation (Figure connected to the fuel oil compensating 5-1) they are numbered No. 1, No. 2, water line. It serves two important functions: first, as a tank to prevent oil No. 6, and No. 7. from being blown over the side through b. Fuel ballast tanks. Fuel ballast tanks the compensating water line in case of are large tanks, amidships, between the small air leaks in either the fuel ballast pressure hull and the outer hull, which tanks or the normal fuel oil tanks; and may be used either as fuel storage tanks second, as a tank to which oily bilge water may be pumped without danger of or as main ballast tanks. They are leaving a slick. This tank has a capacity connected to the fuel oil system in the of about 3,000 gallons. same manner as the normal fuel oil tanks, but in addition, they have main e. Clean fuel oil tanks. The clean fuel oil vents, main flood valves, and high- tanks, two in number, are used to store pressure air and low-pressure blower connections which are necessary when oil prior to its use in the engine and after the tank is in use as a main ballast tank. it has been purified. These tanks are not When rigged as a main ballast tank, all compensated with compensating water. They have capacities of approximately connections to the fuel oil system are
  7. secured. 600 gallons each. Most fleet type submarines have three 5B4. Fuel oil piping systems. a. Fuel oil fuel ballast tanks varying in capacity filling and transfer line. The fuel oil from about 19,000 to 25,000 gallons. filling and transfer line extends the length On a typical installation (Figure 5-1), of the ship and is used for filling the fuel the fuel ballast tanks are numbered No. system and transferring the fuel from the 3, No. 4, and No. 5. Current practice is various fuel oil tanks to the collecting to depart on war patrol with all fuel tank where it can be piped off, purified, ballast tanks filled with fuel oil. Fuel is and used in the engine. There is a used first from No. 4 fuel ballast tank, connection from the fuel oil filling and and as soon as that tank is empty of fuel transfer line to the top of each side of (filled with salt water) it is converted to each normal fuel oil and fuel oil ballast a main ballast tank. Upon conversion, tank. This may be a direct connection or the tank is flushed out several times to through a manifold, as shown in Figure insure that all fuel oil is out of the tank. 5-1 for normal fuel oil tanks No. 1 and The conversion of No. 4 FBT to a main No. 2. There is also a connection from ballast tank increases the stability of the the fuel submarine and decreases the amount of wetter surface of the hull when on the surface. 96 Figure 5-1. TYPICAL INSTALLATION OF SHIP'S FUEL OIL AND COMPENSATING WATER SYSTEMS. oil transfer line to the bottom of the way of a header box in the conning tower collecting tank. This is the line through shears, but the amount of water needed to which passes all of the fuel from the replace the fuel oil used goes down into main fuel oil tanks. At the forward and the compensating water line by way of a after end of the transfer line is a fuel four-valve manifold. The header box filling line that connects the forward serves to keep a head of water on the and after fuel filling connections on the system, insuring that the entire system is main deck with the fuel oil filling and completely filled at all times. transfer line. The four-valve manifold is really a bypass manifold for the expansion tank. When the fuel system is in use, only one of the normal fuel or fuel ballast The four valves on the manifold (see tanks is in service at a time. This is Figure 5-2) are used as follows: made possible by a stop valve in the fuel oil transfer line to the top of each Valve A cuts off the four-valve manifold side of each tank. This valve permits all from the header box. tanks except the one in service to be secured on the fuel transfer line. Valve B closes the line from the manifold to the bottom of the expansion tank. b.Fuel oil compensating water line. This line runs the length of the ship and Valve C is the bypass valve for has a connection to the bottom of each expansion. If this valve is open, the normal fuel oil and fuel oil ballast tank. compensating water an go directly into The salt water that replaces the fuel oil the compensating water line without in the fuel tanks comes from the main going through the expansion tank. If the engine circulating salt water discharge valve is closed, the compensating water to the compensating water line or, if all must go into the compensating water line engines are secured, from the main through the expansion tank. During
  8. motor cooling circulating salt water normal operation this valve is closed. discharge to the compensating line. Most of this water goes over the side by Valve D closes the line from the manifold to the top of the expansion tank. Figure 5-2. Four-valve manifold. 97 Under ordinary operating conditions, the header box. It must be emphasized all the valves on the compensating that all the above operations are taking water line to the individual tanks are place concurrently and that the entire locked open and valve C is locked movement of the liquids is caused by the closed. This is necessary because sea head of water on the system from the pressure must be maintained on the header box. inside of the fuel ballast tanks, normal fuel tanks, expansion tank, and As soon as the expansion tank is filled collecting tank, when the submarine is with salt water, the salt water comes up submerged. If this were not done, the to the four-valve manifold through valve sea pressure on a deep dive would D into the compensating water line, and become so great as to cause a rupture of thence into the bottom of No. 4 FBT. As the relatively weak outer hull. soon as No. 4 FBT is empty of fuel, salt Therefore, it is vital that all the valves water rises into the fuel oil transfer line mentioned above be open or closed as and then into the bottom of the collecting indicated. If these valves are properly tank. This is a positive indication that the rigged when the submarine is No. 4 FBT has no more fuel in it. In submerged, sea pressure can enter the order to tell when the salt water reaches system through the header box and then the collecting tank, a liquidometer age go to the inside of every fuel oil tank which reads directly the amount of fuel except the clean fuel oil tanks, if the in the tank is placed on the collecting valves on the compensating water tank. As soon as this gage reads less than branch lines to each tank are open. completely filled, it is evident (in this These valves on the individual branch case) that No. 4 FBT has no more fuel. lines are also normally locked open. No. 4 FBT is then secured on the fuel This maintains the same pressure on transfer line and another fuel tank is each side of the submarine outer hull, placed on service. The small amount of insuring that it will not rupture. The water may be left in the bottom of the valves are always locked to prevent collecting tank, as fuel oil that comes into accidental closing or opening. the tank will rise through the water to the top of the tank. The water normally is left in the bottom of the collecting tank until 5B5. Operation of the system. When
  9. the submarine is departing on war the ship is refueled. At that time the patrol, all tanks in the fuel oil system water is withdrawn by pumping it out are completely filled with fuel. Upon with the drain pump through the drain departure, one of the normal fuel oil or line to the bottom of the collecting tank. fuel ballast tanks will be on service. As soon as fuel is drawn from the top of 5B6. Blowing and venting of fuel the collecting tank by means of the fuel tanks. Each side of each tank is provided oil transfer pump, salt water comes into with blow connections which connect to the bottom of the expansion tank, the ship's low-pressure 225-pound air keeping the system completely filled line. In an emergency or to effect repairs, with liquid. it is often necessary to blow a fuel tank completely clear of all liquids. This is The path of the water can be traced by done by closing the tank's stop valves to referring to Figure 5-1: Assume that the fuel oil transfer line and blowing the No. 4 FBT is in service. As fuel is fuel or water over the side or to another taken off the top of the collecting tank, tank (through the compensating water fuel comes from the top of No. 4 FBT line). through the fuel oil filling and transfer line into the bottom of the collecting The air line from the blow valve to the tank, replacing the fuel taken from the tank also has a connection to permit top of that tank. At the same time the venting of the tank if some air has fuel taken from the top of No. 4 FBT is accumulated in its top or if it is desired to replaced by the fuel from the top of the fill a completely empty tank with oil or expansion tank by way of the four- water. All fuel tanks are equipped with valve manifold, the compensating water either liquidometer gages or sampling line, and the compensating water cocks. These sampling cocks are used to branch line to the bottom of No. 4 FBT. take samples of liquid at various fixed The fuel oil drawn from the top of the levels in the, tank in order to ascertain expansion tank is replaced by salt water approximately the entering the bottom of the expansion tank by way of the four-valve manifold and the line to 98 amount of fuel in the tank. The units, a tank unit located in the tank liquidometer gages are adjusted so as to whose capacity is to be measured, and a read directly the number of gallons of dial unit located at some distant point fuel in the tank. away from the tank (such as in the control room of a submarine). Operation 5B7. Liquidometers. In submarine fuel of the instrument is dependent upon the movement of the float in the tank which systems, liquidometers are used to is mechanically connected to an upper determine: and lower bellows of the tank unit. These two bellows are rigidly supported at one 1) the level of oil in partially filled tanks, such as clean fuel oil tanks, and end by a bracket, and both are connected by tubing to two similar bellows in the dial unit. The dial unit bellows are each 2) the level between fuel oil and salt water in completely filled tanks such as supported at one end by a bracket which also provides a bearing connection for normal fuel tanks, fuel ballast tanks, the indicator pointer. The free ends of the collecting tank, and expansion tank. bellows, facing the pointer, are connected to a link which actuates the pointer. The liquidometer is equipped with a When the float moves down, the float mechanism, the movement of mechanical linkage between the float arm which activates a double-acting
  10. opposed hydraulic mechanism which and the upper and lower tank bellows registers upon a properly calibrated dial compresses the lower bellows, forcing a portion of the liquid from it into the the volume of oil in a tank in gallons. interconnected dial unit bellows, causing it to expand. At the same time, the upper The float of a liquidometer used in compensated fuel tanks is usually filled bellows in the tank unit is being elongated through the mechanical with kerosene to a point where it will float in water but sink in fuel oil. Since the water is below the oil, the float will sink through the oil and stop at the compensating water level. The instrument consists essentially of two Figure 5-3. Schematic diagram of liquidometer. 99 connection to the float arm and takes in submarines, the connection between the a portion of the liquid from the other compensating water line and the four- dial unit bellows, which is then caused valve manifold is provided with a plug to contract. Reverse action takes place protected sight glass to check the pipe's if the tank float moves upward. contents. This glass should be kept in clean and readable condition at all times. In most modern fleet type submarines 5B8. Maintenance of ship's fuel this sight glass has been blanked off system. All fuel storage tanks should because of possible breakage during be periodically inspected and cleaned. depth charge attack. This is usually done during submarine overhauls at naval shipyards. It is essential that all air be excluded from the fuel system, or the system may All screen strainers used in connection become air-bound, thus preventing with the fuel oil system should be proper flow of oil to the engines and also periodically removed and cleaned. disturbing the trim of the submarine. This may be done by venting the system The valve seat gaskets used in the fuel through the vent facilities provided. ballast tanks are made of special, oil- resisting rubber. These gaskets should In venting fuel tanks in use, the following be inspected at each filling and order should be observed: first, the
  11. expansion tank, then the fuel tank on replaced if deteriorated or damaged. service, then the collecting tank. The remaining fuel tanks may then be vented In the fuel ballast tanks, all valves are in any order. The discharge line from the enclosed in galvanized wire mesh collecting tank to the clean fuel oil tank screens. These wire mesh screens should be closed during venting should be cleaned whenever inspection operations. indicates that it is necessary. On some C. SUPPLY FROM SHIP'S FUEL SYSTEM TO ENGINE FUEL SYSTEMS 5C1. General. After leaving the through the purifier. It may also be used collecting tank, fuel is piped through a for priming purposes by taking a suction system comprised of strainers, fuel from the clean fuel oil tank and meters, fuel oil transfer pumps, delivering the priming oil to the purifiers, and clean fuel oil tanks before individual engine fuel system. An engine reaching the engine. This section of the normally is primed before starting, fuel oil system is divided into two particularly if it has been secured for parts. One part serves the forward some time. engine room, the other the after engine room. The two are interconnected to Under normal operating conditions this provide flexibility of operation. pump is operated until the clean fuel oil tanks are full. It is then secured until the 5C2. Strainers and meters. Fuel oil to level of oil in the clean fuel oil tanks be used in the engine is normally taken becomes such as to indicate need for from the top of the collecting tank. It replenishment. may, however, in some installations, be drawn directly from the fuel oil filling 5C4. Pure oil purifiers. a. General. The and transfer line. In either case, the oil fuel oil purifiers are Sharples centrifuge should go through a wire mesh type units which operate on the principle of strainer and fuel meter before entering centrifugal force. the suction side of the fuel oil transfer pump. Both strainer and meter are fitted Centrifugal force is the force exerted with bypass connections by means of upon a body or substance by rotation that which a strainer, or meter, or both may impels that body or substance outward be bypassed. from the axis of rotation. When a mixture of liquids is revolved at high speed in a 5C3. Fuel oil transfer and purifier container, the centrifugal force causes the pumps. Located in each engine room is components of the liquid to separate. The a positive displacement type fuel oil component with the greatest specific transfer and purifier pump, driven by an gravity will assume the outermost electric motor. The primary function of position, and the lightest component, the this pump is to transfer fuel oil from the innermost position. Thus, if a mixture of collecting tank to the clean fuel oil tank water and oil is revolved, the water, being the heavier component, will separate from the lighter oil and form 100
  12. Figure 5-4. Fuel oil supply from ship's fuel system to engine fuel system in one engine room. a layer around the wall of the container, reduce the effect of the centrifugal force. while the oil remains near the center of the container. The Sharples fuel oil When the machine is operated as a purifier operates on this principle. separator, the bowl is primed with fresh water until an effective water seal is The Sharples purifier can be used as a created at the water discharge outlet. The separator or a clarifier. When used as a water priming line is sealed off from the separator, the purifier separates oil fuel inlet line by means of a check valve from water and solid sediment. When which prevents water from finding its used as a clarifier, it separates oil from way into the fuel system. Then the fuel solid sediment only. The unit is usually oil supply is forced into the swiftly set up as a separator in fuel oil systems revolving bowl. The centrifugal force and a clarifier in lube oil systems. (See throws the water, which has a heavier specific gravity than the oil, to the Section 7B7.) outside wall of the bowl and creates a b. Operation. The fuel oil transfer and vertical layer of water at this outer purifier pump forces fuel oil through a extremity. The fuel oil, which has a lighter specific gravity, forms a layer short connecting line at the bottom of next to the water. Any particles of the purifier bowl. The purifier bowl is revolved by an attached electric motor sediment in the fuel oil have a heavier specific gravity than either the water or at about 15,000 rpm. A three-wing oil and are drawn and held against the partition extends the full length of the bowl on the inside. The purpose of this wall of the bowl by the centrifugal force. Dirt and sediment are cleaned out of the partition is to keep the liquid in the bowl when necessary. bowl revolving with the bowl. Otherwise there would be slippage of the liquid column which would At the top of the purifier bowl is a barrier called a ring dam, which covers the top
  13. of the 101 Figure 5-6. Attached fuel oil supply pump, F-M. Figure 5-5. Fuel oil transfer and oil can be pumped to either fuel oil purifier pump. purifier by means of the transfer and purifier pumps and discharged to either vertical column of water and fuel oil. clean fuel oil tank. Also, the transfer and There is an opening at the outer purifier pump may be used to draw fuel diameter of the ring dam through which oil from either clean fuel oil tank and only excess water is discharged. At the supply any engine directly, during inner diameter of the ring dam is priming operation. another opening through which only purified fuel oil discharges. Thus, as A hand pump is connected to the clean long as the centrifugal force and the fuel oil tanks to provide a means of effective water seal are maintained, it is checking the contents of the tank for impossible for fuel oil to displace the water, for testing the quality of the oil, water and get out through the water and for removing residual oil in the tank discharge opening. It is just as when it is desired to clean it. impossible for water to get out through the fuel oil discharge opening as long Each engine in a compartment is as the centrifugal force is in effect. connected to the clean fuel oil tank in the same compartment by a fuel line which 5C5. Clean fuel oil tanks. All fuel oil goes from the bottom of the clean fuel oil supplied to the engines is normally tank up to the attached fuel oil pump on drawn from the clean fuel oil tanks. the engine. The attached fuel oil pump There are two clean fuel oil tanks, one takes a suction from the clean fuel oil in the forward engine room and one in tank and delivers the oil to-the engine the after engine room. Under normal fuel system. If the attached fuel oil pump operating conditions, the engines in on one engine should become each compartment draw their supply inoperative, it is possible to connect the from the clean fuel oil tank in that fuel oil transfer and purifier pump so as compartment. to supply fuel up to the engine, thereby preventing a shutdown of the engine. Each tank averages about 600 gallons capacity in fleet type submarine installations. By means of a system of valves and piping, fuel
  14. 102 Figure 5-7. Exploded view of attached fuel all supply pump, F-M. Figure 5-8. Exploded view of attached fuel oil supply pump, GM. 103 Each clean fuel oil tank is equipped with a liquidometer to measure the quantity of fuel oil in the tanks at all times. 5C6. Attached fuel oil supply pump, F-M. The attached fuel oil supply pump (Figures 5-6 and 5-7) draws fuel by suction from the clean fuel oil tank and delivers it through the strainer and filter units to the engine main fuel oil header. The pump is a positive displacement type gear pump and is driven directly from the lower crankshaft of the engine through a flexible gear drive. A packing Figure 5-9. Fuel oil filter.
  15. gland is provided on the fuel oil pump drive gear shaft to prevent fuel oil from Each strainer consists of a body or case leaking out around the shaft. which is fitted with a metal ribbon wound element. A scraper device with 5C7. Attached fuel oil supply pump, long blades that contact the inside surface GM. The function of the GM attached of the element is fitted into each strainer. fuel oil supply pump is the same as that A handle for turning the element extends of the pump described in section 5C6 through the top of the strainer so that the above. This pump is also of the positive operator may occasionally turn the displacement type, but it is driven element, thereby cleaning accumulated directly from one of the engine dirt from the surface of the element. Dirt camshafts instead of the crankshaft as and sediment drop to the bottom of the on the F-M engine. The pump drive case and should be removed at regular shaft is provided with a packing gland cleaning periods. to prevent fuel oil from leaking around the shaft. Each duplex strainer is equipped with a duplex pressure gage which measures the Fuel oil is drawn from the clean fuel oil pressures of the fuel oil fed into the tank by suction created by the pump strainer and of the oil leaving the strainer. and fed into the pump housing through A drop of 10 psi between the inlet an inlet at the top of the pump. Oil is pressure and the outlet pressure indicates forced from the outlet at the bottom of that the element or elements of the the pump into the engine supply line. A strainer needs cleaning. Each strainer has pressure regulating valve in connection a small valve at the top of the case for with the pump may be set to maintain a venting air from the unit. pressure of 40-50 psi in the engine fuel system. A pressure relief valve may be 5C9. Duplex fuel oil filter. Most set at slightly above the desired installations are equipped with duplex pressure to bleed off excess fuel oil fuel oil filters as well as strainers. In when the pressure exceeds the function and operation the maximum setting. This oil returns to the clean fuel oil tank. 5C8. Duplex fuel oil strainer. All fuel oil delivered to the engine fuel header by pressure from the attached pump must pass through a duplex type strainer. This strainer actually consists of two strainer elements which may be used either individually or in pairs. The flow of fuel oil through either or both strainers is controlled by a manually operated valve. When the valve is set to bypass one strainer, the bypassed element may be removed and cleaned without disturbing the flow of fuel oil to the engine. 104 filters are similar to the strainers. In the particles of dirt and foreign matter. The duplex filter, the element is a filter elements are not equipped with removable absorbent type cartridge scrapers. They should be examined when which is removed and thrown away the pressure registered by the duplex when it becomes dirty. The absorbent pressure gage drops a specified value. If
  16. type filter cartridge is a denser element found dirty, they must be removed and than the strainer element and replaced by a new element. consequently filters out finer D. FUEL INJECTION SYSTEMS start slowly so that a limited amount of 5D1. Basic requirements of a fuel injection system. The primary function fuel will accumulate in the cylinder of a fuel injection system is to measure during the initial ignition lag before accurately, vaporize, and inject the fuelcombustion commences. It should at the proper time according to the proceed at such a rate that-the maximum rise in cylinder pressure is moderate, but power requirements of the engine. it must introduce the fuel as rapidly as permissible in order to obtain complete In order to accomplish this there are certain basic requirements that any fuel combustion and maximum expansion of the combustion product. injection system must fulfill. d. It must properly atomize the injected a. It must measure or meter the fuel. fuel. The fuel must be injected into The quantity of fuel injected determines compressed air in the combustion the amount of energy available to the chamber with sufficient force to engine through combustion. The brake accomplish thorough atomization. mean effective pressure and hence, Atomization reduces the fuel to minute economy, are dependent to a great particles or globules. In general, the extent upon the air to fuel ratio. Thus, it smaller the particles of fuel the shorter is important that the fuel injection will be the delay period, that is, the system accurately measure the correct interval between injection and ignition. quantity of fuel according to engine requirements. Opposed to this requirement is the fact that the smallest particles of fuel have a b. It must time the injection. The low penetrating quality. Therefore, with injection timing has a pronounced very fine atomization there is a tendency effect on engine performance. Early toward incomplete mixing of the fuel and injection tends to develop high cylinder air which leads to incomplete pressures, because the fuel is injected combustion. during the part of the cycle when the piston is traveling slowly and therefore the combustion takes place at nearly e. It must inject fuel with sufficient force constant volume. Extremely early for effective penetration and distribution. injection will cause knocking. Late Fuel must be atomized into sufficiently rejection tends toward decreasing the small particles to produce a satisfactory mean effective pressure of the engine delay period. However, if the atomization and consequently lowering the power process reduces the fuel to too small output. Extremely late injection tends particles, they will lack penetration. This toward incomplete combustion lack of penetration results in igniting of the small particles before they can be resulting in a smoky exhaust. injected far enough into the area of the combustion chamber. Consequently, A more complete description of these injection pressure must be of sufficient fuel injection systems is contained in force and the orifice properly the Bureau of Ships publications proportioned to effect good penetration. entitled: Fairbanks-Morse Fuel Injection Systems Maintenance Manual, NavShips 341-5019; and The fuel spray must also be directed by the spray tip to secure a uniform General Motors Diesel Fuel Injector Maintenance Manual, NavShips 341- distribution of the spray charge over the
  17. 5018. entire combustion area. c. It must control the rate of feed during High turbulence in the combustion injection. The rate of injection is chamber causes a more thorough mixing important because it determines the rate of the fuel and air and aids in complete of combustion and influences the combustion. engine efficiency. Injection should 105 branch line. In the General Motors 5D2. Types of fuel injection systems. The earlier diesel engine fuel systems engines each pump is an integral part of utilized the air injection principle in the unit injector which includes, the their design. This method of injection injection nozzle. In both engines the consisted of furnishing both fuel oil and injection pump meters the fuel, delivers it air to an injector valve. The high- to the injection nozzle, and supplies the pressure air carried the fuel into the energy through hydraulic pressure of the cylinder where it was burned. Engines fuel oil for the injection and atomization using air injection usually developed a of fuel at the injection nozzle. high combustion efficiency because of the efficient mixing of fuel and air b. The fuel injection nozzle. The fuel possible in such a system. However, a injection nozzle contains a check valve considerable amount of high-pressure which may be either needle type or air was necessary to inject the mixture spherical head type. The valve is opened into the cylinder against the for injection by hydraulic pressure from compression pressure present in the the injection pump which acts on the cylinder. The necessary air pressure differential area of the valve. The pump was usually supplied by an attached air plunger forces fuel oil through the compressor. These air compressors orifices of the spray tip, atomizing the used a large percentage (10 to 15 fuel delivered into the combustion percent) of the power developed by the chamber. The injection is timed at the engine, and, in addition, it was difficult pump, not at the injection nozzle. to maintain them in proper operating condition. c. High-pressure fuel oil lines. Valve opening pressures up to 3,000 psi are In order to increase the reliability and encountered in many fuel injection compactness of these older engines, it systems, necessitating the use of high- became necessary to do away with the pressure lines. Such tubing should meet attached air compressor and shift to the the following requirements: solid injection system in which the fuel alone was injected into the cylinder in a 1. It should be of uniform inside fine atomized spray. This type of diameter, otherwise the injection injection requires a higher grade fuel characteristics will be seriously impaired. than did the air injection system. Solid For example, if the inside diameter of the injection engines are in general more tubing should occasionally run smaller powerful for their size, more simple in than that specified, excessive pressures construction, and more reliable than are likely to result. Where inside their air injection predecessors. Also diameters exceed specifications, the the total weight per horsepower of the pressures will drop and there is the engine is much less. All of our present possibility that the tubing will develop modern submarine engines operate on structural weakness. the solid injection principle. 2. It should possess sufficient and 5D3. Components of the solid fuel uniform strength to withstand pressures injection system. The solid fuel
  18. injection systems under discussion may up to 9,000 psi without yielding. wary in design but they are alike in principle. The components of the 3. It should have high ductility to permit mechanical fuel injection system are: easy bending to the desired shape and cold swaging without cracking. Bending a. The fuel measuring or injection of the tubing does not affect the injection pump. These pumps are usually of the characteristics as long as the bends do plunger type and are operated from not have a radius of less than 1 1/2 cams on the engine camshafts through a inches. rocker lever or push rod assembly. 4. It should have a smooth, accurate bore, A separate pump (or pumps) is used for absolutely free from scale, seams, laps, each cylinder of the engine. In the laminations, deep pits, or other serious Fairbanks Morse OP engines each defects which would weaken the pump is a separate unit connected to the structure of the metal or cause fuel injection nozzle by a restrictions to the flow of the fluid. 106 E. GENERAL MOTORS ENGINE FUEL OIL SYSTEM 5E1. General. The attached fuel oil at the injector end of the rocker lever. pump draws fuel oil from the supply The quantity of the fuel injected into tank and forces it through the fuel each cylinder (and therefore the power metering block, the strainer, and the developed in that cylinder) is varied by filter. From the filter, the fuel oil flows rotating the plunger by means of the to the fuel supply manifold, which is injector control rack. A rack adjustment, the bottom tube of the multiple called the micro-adjustment and located manifold assembly on each cylinder on the control linkage, permits balancing bank, through a tube to a single jet filter the load of each cylinder while the on each cylinder head. This filter is a engine is running. metal ribbon wound type with passages of approximately 0.001 inch in the The unit injector is comprised of the element. From the filter, the fuel flows various parts illustrated in Figure 5-11. through the jumper tube that supplies Of these, the principal parts are the body, the injector. The injector inlet contains spray valve nut, bushing, plunger, needle a filter to further prevent solid matter valve or spherical type check valve from reaching the spray valve. (depending on the type of injector), valve spring, and the spray tip. Two relief valves in the fuel metering block limit the fuel oil pressure in the The injector body is a heat-treated, alloy system. Any excess oil is bypassed steel forging with two flat surfaces back to the clean fuel oil tank. extending on opposite sides for holding the injector in a vise when necessary. Surplus fuel from the injector flows These surfaces are drilled in line to through a filter in the outlet passage so support a part of the injector control that any reverse flow of fuel cannot linkage. A small vent, just below the carry dirt into the injector. The surplus holding down clamp seat, allows leakage fuel passes from the injector through a fuel which serves as the lubricant for the jumper tube to the bleed manifold plunger and bushing to escape from the which is the middle tube in the multiple plunger spring chamber. This hole also manifold assembly on each cylinder serves as a breather opening to prevent bank. The fuel from the bleed manifold pumping action by the plunger follower. on each bank flows through a metering On some injectors, plunger pump fuel
  19. valve in the metering block, then back leakage flows through a hollow drain dowel, then through a drilled passage in to the clean fuel oil tank. the cylinder head and back to the clean 5E2. The unit injector. a. Description. fuel oil tank. On the GM engine the fuel injection pump and spray valve are combined The bushing is the cylinder for the into a single compact unit called the plunger pumping unit of the injector. It is unit injector, which meters the fuel and located and held against turning in the also atomizes and sprays it into the body by a guide pin that fits into a cylinder. The unit injector is held in groove at the upper end of the bushing. position in a water-cooled jacket in the Two openings in the bushing wall, on center of the cylinder head. At the opposite sides, serve as the inlet and lower end, the injector forms a gastight bypass ports for the fuel oil. The bottom seal with the tapered seat in the surface of the bushing is lapped to form cylinder head. All injectors in the an oiltight seal against the full injection engine are alike and interchangeable. pressure. Fuel is supplied through jumper tubes with spherical type gasketless The unit injector pump plunger is made connections. of a special steel, lapped to a close fit in the bore of the bushing. The clearance The pumping function of the injector is between the surface of the plunger and accomplished by the reciprocating bushing is so fine that it is usually motion of the constant stroke injection measured by forcing a specific amount of plunger which is actuated by the oil of a fixed viscosity between the injector cam on the engine camshaft surfaces and measuring the time through the injector rocker lever. The consumed. position of the plunger, and thereby the timing, is adjusted by means of the ball The lower end of the plunger is cut away stud and lock nut to form a recess with an upper and a lower helical lip. These helical lips cover and uncover the 107
  20. Figure 5-10. Isometric view of fuel injection system, GM. 108


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