Методические указания для студентов 2 курса судомеханического факультета заочного отделения
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Fuel System The fuel piping system comprises the fuel supply lines, high-pressure fuel lines and fuel heating pipes, if heavy fuel is used. Fuel supply lines include the supply lines from the fuel transfer pumps and preheating arrangement to the fuel filters and fuel pumps on the engine supply also the fuel supply lines to the installation. High-pressure fuel lines connect the fuel pumps with the fuel valves and are under very high intermittent pressure. Fuel system fittings are: fuel transfer pump, fuel filter, fuel pressure -maintenance valve, fuel shut-off valve, fuel non-return valve. The fuel transfer pump is driven separately by an electric motor. The fuel filter contains several filter elements which can be switched over during operation and is designed for steam heating. The fuel pressure-retaining valve is designed for adjustable back pressure. The pressure adjusted should be so high that there is no formation of vapour on the suction side of the pumps. The fuel shut-off valve opens during operations and is provided with a double cone seat to prevent leakage, so that the main pipe can be isolated for dismantling the fuel pumps or preheating. The non-return valve is situated between the fuel pumps and the overflow line with single-controlled fuel pumps. During operation the surplus fuel delivered by the fuel transfer pumps runs off into the overflow line. When dismantling a fuel pump, the letter is isolated from the overflow line by the non-return valve. Each cylinder possesses its own fuel pump, which discharges a definite quantity of fuel through the discharge line to the fuel valve at the correct moments and under high pressure, the fuel is then sprayed into the combustion chamber. Vocabulary
10 11   ВАРИАНТ 31. Перепишите следующие предложения, подчеркните в каждом из них глагол-сказуемое, определите его видовременную форму и залог. l)Two sailors of our crew have been hospitalized in a foreign port.
2. Перепишите следующие предложения , подчеркните Participle I и Participle II и установите, является ли оно определением, обстоятельством или частью глагола-сказуемого. Переведите предложения на русский язык.
3) Two or more furnaces may be fitted depending on the size of the boiler. 4)The energy normally lost in the exhaust is relatively high. 3. Перепишите следующие предложения, подчеркните в каждом из них модальный глагол или его эквивалент. Переведите на русский язык.
4. Прочитайте и письменно переведите текст, обращая внимание на пояснения к тексту. Engine lubrication The problem involved in lubrication is the maintenance of a film of lubricant between any two surfaces that have relative motion, so that the surfaces do not come in contact with each other. In the diesel engine there are two general types of surfaces - those inside the cylinders and those in the bearings. The only lubricant is mineral oil. The oil used for lubrication of the cylinders must be applied in small quantities, but the oil used for bearing lubrication can be applied in any quantity and used repeatedly. Cylinder lubrication has two purposes - to maintain the required film to separate the liner surface and the faces of the piston rings as they slide up and down, and act as a seal to prevent gases blowing past the rings. The things must be done despite the high temperature of combustion. The customary method of applying oil to the cylinder walls is by means of small pumps, assembled in units, known as mechanical lubrication, with common suction reservoir and a discharge pipe from each pump leading to a connection in the side of the cylinder, through which the oil passes into a hole in the liner. After passing into the cylinder the oil is spread over the surface of the liner by the piston rings as they slide along the liner. Bearing lubrication is effected by means of a circulatory system through which a large amount of oil under pressure is forced through the bearings. In general, the system is made up of a sump or reservoir, from which a circulating pump draws the oil and discharges it through the coolers and filters to a manifold which has a branch to each main bearing. Vocabulary
12 13  ВАРИАНТ 41. Перепишите следующие предложения, подчеркните в каждом из них глагол-сказуемое, определите его видовременную форму и залог.
2. Перепишите следующие предложения , подчеркните Participle I и Participle II и установите, является ли оно определением, обстоятельством или частью глагола-сказуемого. Переведите предложения на русский язык.
3. Перепишите следующие предложения, подчеркните в каждом из них модальный глагол или его эквивалент. Переведите на русский язык.
4. Прочитайте и письменно переведите текст, обращая внимание на пояснения к тексту. Supercharging Supercharging, or pressure charging, is a means of increasing the power output of a given engine. It is the process of filling the engine cylinder with air before the compression stroke starts. The pressure of this air is above atmospheric in order to get a greater weight of air into the cylinder. If to start with a higher pressure, the final compression pressure will be higher. This means that if the engine is supercharged, the volume of the compression space must be enlarged if the compression pressure, will be higher. This means that if the engine is supercharged, the volume of the compression space must be enlarged if the compression pressure is to be kept the same. Having a greater weight of air in the cylinder more fuel is burnt. Although more oil is burnt there is more air present and the ratio of oil to air is the same as without supercharging. Exhaust occurs at a higher pressure, but the temperature of the exhaust is lower than with ordinary operation. The inlet valve opens before the exhaust valve closes and the inlet air being higher in pressure than the exhaust gases at the time the inlet valve opens. The air is blown through the compression space, scavenging out the gases and cooling them, the piston and cylinder walls. This action completely fills the cylinder space with fresh air and the net increase in power developed in the engine may be as much as 50 %. In modern Diesel engines exhaust gas turbocharging is widely used. The exhaust-driven turbochargers operate on the pulse system or on the constant-pressure principle, and are independent of the crankshaft. Their speed changes with the load on the engine. The air compressed by the turbochargers flows into the scavenging-air receiver and through non-return valve into the chambers below each cylinder. Here it is further compressed by the pistons on their downward stoke before flowing into the combustion space when the pistons uncover the scavenge ports. When the turbocharger is out of action, the ship can run at 75% of her normal speed. Vocabulary
14 15  ВАРИАНТ 51. Перепишите следующие предложения, подчеркните в каждом из них глагол-сказуемое, определите его видовременную форму и залог.
2. Перепишите следующие предложения , подчеркните Participle I и Participle II и установите, является ли оно определением, обстоятельством или частью глагола-сказуемого. Переведите предложения на русский язык.
3. Перепишите следующие предложения, подчеркните в каждом из них модальный глагол или его эквивалент. Переведите на русский язык.
4. Прочитайте и письменно переведите текст, обращая внимание на пояснения к тексту. Turbocharging In the four-stroke naturally aspirated engine, the air for combustion is drawn in from atmosphere the suction stroke. In the turbocharged engine, the air is supplied pre-compressed and, in some cases, cooled. A greater weight of air for combustion is thus available in the cylinder and due to the valve overlap the cylinder is scavenged of the exhaust gases. The effect of turbocharging is:
With the greater air weight, a greater quantity of fuel can be burned and an increase of power obtained without increasing the temperature and the heat stresses in the engine. The turbocharger comprises a single stage axial flow exhaust gas driven turbine, driving a centrifugal air compressor which draws air from the atmosphere and delivers it under pressure to the air inlet manifold, then through the air inlet valves to the cylinders the gas turbine wheel and air impeller are mounted on a common rotor shaft carried in bearings mounted at each end of the shaft. The impulse energy of the gases from the various cylinders is used to drive the turbocharger and there is no loss of engine power. To ensure efficient scavenging it is necessary to have a large overlap of the air and exhaust valves. With this overlap on multi-cylinder engines it is essential to avoid interference in the exhaust pipes between the exhaust impulses from successive cylinders, as this would interfere with efficient scavenging. To eliminate this, two, three or four exhaust pipes are used depending on the number of cylinders. Vocabulary
16 17   ЧАСТЬ 3. РАЗГОВОРНЫЕ ТЕМЫ1. My Speciality I The principal aim of the shipmechanical faculty is to train certificated specialists in the following fields:
The graduates of the faculty get the specialities of a mechanical engineer, a ship builder and an environment protection engineer. The educational course begins with mastering mathematics, physics, chemistry, drawing, descriptive geometry. Students also have humanitarian sciences: history of Russia, philosophy, political history, foreign languages, etc. The graduates of the faculty get the speciality of a mechanical engineer. II Junior students study both technical and social sciences. Senior students study special subjects such as details of machines, theory of machines and mechanism, ship internal combustion engines and others. Special attention is paid to studying fuel system, cooling and lubricating systems. Students study engine arrangement and types of engines. Besides they study turbine arrangement. III Each year students of the faculty have an industrial training. After the first year they have one-month industrial training. After the third year students have a ship-board training lasting 6 month. Students keep watch, do work as motormen, help to repair damages of an engine. Traditional students practical training takes place in different ports of Siberian rivers and at the Sea of Japan. Undergraduates collect necessary information for their graduation papers. IV The faculty comprises several chairs: such as ship internal combustion engines chair, shipbuilding chair, shiprepairing chair, technology of metals chair and others. There are some mechanical workshops, labs of internal combustion engines, labs of auxiliary mechanisms, a metal-cutting lab at the disposal of students. According to the 5-year program the faculty gives fundamental knowledge combined with practical skills. Vocabulary
18 19   Questions to be answered:
2. Diesel Engine Diesels are the most economical heat engines. The Diesel engine is an "internal combustion" engine; that is to say, the fuel is burnt inside the engine cylinders and not externally in a separate boiler. The principle of operation is as follows,- a charge of pure air is drawn, or pumped, into the engine cylinder and then compressed by the moving piston to a pressure of about 500 lbs per square inch. When air is compressed, it's temperature rises. Fuel is now sprayed into the engine cylinder, is ignited by the hot air and in burning supplies more heat to the air charge thus causing it to expand and drive the engine piston. There are two main types of diesels: two-stroke and four- stroke engines. In two-stroke diesels compression occurs during the first stroke, combustion and expansion occur during the second stroke; exhaust, scavenging and recharging with air occur at the end of the second stroke and at the beginning of the first stroke. The working cycle of a four-stroke diesel requires four separate strokes of the engine piston to complete the operation. These four strokes are called suction, compression, combustion-expansion and exhaust, but only the third stroke provides the power to drive the ship while the other three require power from the remaining cylinders to perform their various duties. So, what happens during these four cycles? First stroke: suction Inlet valve is open, exhaust valve is closed. Air is drawn into the cylinder. Second stroke: compression Both valves are closed. Piston compresses the air to high temperature. Third stroke: combustion- expansion Fuel injected burns. Temperature and pressure of combustion gases increase. Gas pressure forces the piston down (valves are closed). As the volume available for the gases increases, their pressure and temperature decrease. Piston displacement is used to produce power. Fourth stroke: exhaust Exhaust valve is open; inlet valve is closed. Burnt gases are forced out of the engine. The Diesel Engine is made up of stationary and moving parts. Stationary parts These are principally: bedplate, cylinders, cylinder covers and cylinder liners. Moving parts. These include: piston, connecting-rod, crankshaft, flywheel and valves. Vocabulary
20 21 
The turbine is a heat engine consisting of a rotor carrying moving blades, a casing in which the rotor revolves, and stationary nozzles through which the steam is expanded or directed. Glands, bearings, throttle valve, governor and other devices are necessary for operation of the unit. There are two kinds of turbines: steam turbines and gas turbines. The steam turbine consists of two principal elements: 1) nozzles, a device for converting some of the thermal energy of the steam into kinetic energy, and 2) moving blades, an arrangement for converting the kinetic energy of the steam into shaftwork. Steam turbines may be classified as impulse turbines and reaction turbines. In the impulse turbine the steam expands only through stationary nozzles, dropping in pressure and increasing in velocity. The steam then impinges against the moving blades causing rotation and mechanical work. In the reaction turbine the stationary nozzles have the same appearance as the moving blades. The steam drops in pressure and at the same time expands while passing through both the stationary nozzles and the moving blades. Turbines are classed also as: 1) high, 2) intermediate and 3) low pressure. There may be single-cylinder and compound turbines. Single-cylinder indicates that the unit consists of one turbine contained in one casing. A compound unit consists of two or more individual turbines. Compound turbines are further classified as: 1) tandem-compound, and 2) cross-compound. In the tandem- compound unit all the individual turbines are mounted upon a common shaft. In the cross- compound unit each turbine has a separate shaft. According to the direction of steam flow the turbines are axial-flow and radial-flow. They may be condensing and non-condensing as well. The condensing turbine exhaust their steam to a condenser which maintains back pressure, while the non-condensing unit usually exhaust its steam to another device where it is used for heating. Gas turbines work on exactly the same thermodynamic cycle as an ordinary Diesel engine: they draw in air from the atmosphere, compress it, heat the compressed air by the direct burning of fuel in it and then make the air perform work. The units which make up a complete gas turbine power plant are: the compressor, combustion chamber, intercooler, reheater and gas turbine itself. Vocabulary
22 23  28. casing
31. to expand 32. gland 33. bearing 34. shaft 35. throttle valve 36. governor 37. pressure drop 38. to impinge 39. to cause 40. rotation 41. to constitute 42. drive 43. to increase 44. to decrease
корпус вращаться направляющие сопла расширяться уплотнение подшипник вал дроссельный клапан регулятор перепад давления ударяться вызывать вращение составлять привод увеличивать уменьшать перегородка последовательная ступень чугун цельнолитой толстолистовая сталь литая сталь сваривать сопло отверстие коррозийно-стойкий сплав сплав поперечное сечение сплошная секция перегородка суживающийся расширяющийся стальная поковка цельнокованый составной ротор шейка вала паз уплотнительное кольцо 24
комплект лопаток газотурбинная силовая установка компрессор камера сгорания промежуточный охладитель нагреватель аксиально-проточный или турбокомпрессор
Suggest English equivalents for the following and memorize them: тепловой двигатель, движущиеся лопатки, ротор, корпус, неподвижные сопла, подшипник, дроссельный клапан, уплотнение, регулятор, механизм, установка, активная турбина, реактивная турбина, паровая турбина, газовая турбина, преобразование тепловой энергии пара в кинетическую энергию, преобразование кинетической энергии пара в работу вала, расширяться, падение давления, увеличение скорости, ударяться о лопатки, вращение, однокорпусная турбина, составная турбина, одновальная и двухвальная турбина, осевая турбина, радиальная турбина, конденсатор, сжатый воздух, газотурбинная силовая установка, компрессор, камера сгорания, промежуточный охладитель, нагреватель. 25   | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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