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Text 3. Районные и промышленные котельные
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Do the following task:
1) Translate the text into English.
Районные и промышленные котельные
При централизованном теплоснабжении в качестве источника тепла могут выступать (помимо ТЭЦ) районные котельные, обеспечивающий теплом определенный район. Если котельная отпускает тепло в тепловую сеть промышленного предприятия, то они называются промышленными котельными. По назначению и набору оборудования районные и промышленные котельные одинаковы, и поэтому они объединяются под общим названием «районные котельные». В районных котельных, в отличие от ТЭЦ, вырабатывается только один вид продукции – тепло, которое отпускается в виде пара или горячей воды. Выработка тепла осуществляется в котельных установках. Котельные агрегаты разделяются н два основных класса: паровые, предназначаемые для производства пара, водогрейные, предназначаемые для получения горячей воды. Паровой котельный агрегат (парогенератор) характеризуется паропроизводительностью, давлением и температурой производимого пара. Паровые котлы используют, что бы произвести пар для промышленного использования. Котлы различаются по формам и размерам. Котлы нагревают воду и циркулируют горячую воду через трубы и радиаторы, обогревающие комнату.
Unit 5
Memorize the words
shaft-driven – приводимый от вала;
reciprocation – возвратно-поступательное движение;
torque – крутящий (закручивающий) момент; вращающий момент;
rotor – роторный процесс; ротор;
blades – лопасть, лопатка (турбины), лопатка с регулируемым углом установки;
nozzle – насадок; сопло; форсунка, выпускное отверстие; наконечник;
impinge – налетать, сталкиваться, отражаться;
grid – сетка, решетка; энергосистема; электрическая сеть;
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curve – кривая, график, изгибать;
tandem – последовательно соединенный;
compound – состав; смесь; соединение, составлять; смешивать; составной, сложный;
turbine – турбина;
photovoltaics – фотоэлектрический;
mitigate – смягчать, уменьшать;
trough – жёлоб для стока воды, лоток, корыто; котловина;
loop – петля, скоба, отверстие, рамочная антенна; пучность(волны, тока или напряжения); обводной трубопровод.
Text 3. Turbine
Do the following tasks:
1) Give a written translation of the text into Russian.
2) Look through the text. What information did you get about turbines.
Turbines
The steam turbine is prime mover in which a part of that form of energy of the steam evidenced by a high pressure and temperature is converted into kinetic energy of the steam and then into shaft work.
The basic advantage of the turbine over other forms of prime movers is the absence of any reciprocating parts. With only rotating motion involved, high speeds are attainable. Since power is directly proportional to torque times speed, an increase in the rotative speed materially decreases the value of the torque required for a given power output. A decrease in the required torque permits a reduction in the size of the prime mover by reducing the length of the torque arm or the force acting on the torque arm. Also, with the absence of any reciprocating parts, vibration is greatly minimized. Owing to the high rotative speeds available with relatively little vibration, the size and cost of the driven machinery, of the building space, and of the foundations are greatly reduced. These advantages are most apparent in large prime movers and permit the steam turbine to be built in sizes of over 350,000 hp in single units, and 760,000 hp in compound units.
Text 3. Types of turbine
Do the following tasks:
1) Read and retell each part of the text separately.
2)Write down the terms given in the text and give their meanings in English.
Types of turbines
Steam turbines may be broadly grouped into three types, the classification being made in accordance with the conditions of operation of the steam on the rotor blades.
The groups are as follows:
1) Impulse. This may be divided into
| a) Simple impulse | Pressure compounded |
| b) Compound impulse | Velocity compounded |
| c) Combined impulse | Pressure velocity compounded |
2) Reaction subdivided into
a) Axial flow
b) Radial and axial flow
3) Combination of 1 and 2.
1. Impulse Turbines. In an impulse turbine the potential energy in the steam due to pressure and superheat is converted into kinetic energy in the form of weight and velocity by expanding it in suitably shaped nozzles.
The whole of the expansion takes place in the fixed nozzle passages. As there is no expansion in the passage between the rotor blades, the steam pressure is the same at the inlet and outlet edges of these blades. The steam impinges on the wheel blades causing the wheels to rotate. The expansion is carried out in stages referred to as “pressure stages”, each stage being separated from the next by a diaphragm with nozzle openings through which the steam passes on its way through the turbine.
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a) Simple impulse. This type has a considerable number of pressure stages, a wheel in each stage having one row of blades. To obtain high economy it is necessary that the steam should flow through the turbine with high velocity. This is attained by provision of a large number of pressure stages, the greater the available heat drop, the greater the number of stages. In the simple impulse turbine a wheel of comparatively large diameter is used in the first stage which can deal efficiently with a large energy drop. This large wheel, under nozzle control of the steam can maintain a higher efficiency over a wider range of load than a small one could and is less liable to be affected by changes of steam conditions. An added advantage of a large wheel is that the maximum rating of the machine can be obtained without by-passing which results in a flat consumption curve being maintained over the whole output range.
b) Compound impulse. This turbine has comparatively few pressure stages, a wheel in each of them provided with two or more rows of blades. Low velocity steam is obtained by the provision of what are usually termed “velocity stages” in each of the pressure stages. In these velocity stages the steam after passing through the first row of blades on a wheel is re-directed on to the second row of blades on the same wheel, and successively on to other rows of blades on this wheel, if provided. The steam is re-directed by arranging stationary blading between each two adjacent rows of wheel blading so that the steam leaving the first row of blades on a wheel in a backwards direction enters the first row of stationary blades where its direction is reversed ready for entering the second row of blades on the wheel and so on. This action is repeated in each pressure stage on the turbine.
c) Combined impulse. This turbine is a combination of the types a) and b). It consists of one or more pressure stages with a wheel in each of these stages provided with two or more rows of blades. In the velocity compounded impulse turbine the “carry-over” velocity and-the speed of the shaft are much less than with the simple impulse machine. Each disk carrying the moving blades is perforated, thus maintaining the same pressure on both sides of the wheel. The pressure velocity compounded design is generally known as the “Curtis” type. The pressure compounded turbine has a higher efficiency since the pressure drop per stage may be arranged to give the most suitable jet velocity for a given speed of the machine.
2. Reaction Turbines. In the reaction turbines expansion takes place in both the stationary and rotating passages-and the pressure at entrance to the rotor blades is therefore greater than at exit.
a) Axial flow. In a pure reaction turbine expansion should take place only as the steam passes through the moving blades, the turning effect being due to the reaction consequent on the increase in velocity which accompanies expansion. The reaction turbine has a ring of stationary blades instead of a diaphragm with nozzle passages between the blades of each pair of adjacent wheels. The steam expands in the fixed blades, increasing its velocity, which is imparted to the moving blades on the impulse principle.
Steam is supplied direct to the blading system without expansion in nozzles and the rotation produced is chiefly due to the reaction set up by the steam between the stationary and rotating blades while expanding in them.
b) Radial flow. The Ljungstrom turbine is really a combined radial and axial flow machine. The flow of steam is radial, being admitted at the center of the blade discs and flowing outwards, the steam then being inverted to axial flow in the last stages. The turbine may be constructed for single or double motion. With the double motion design the discs rotate in opposite directions at equal speeds and the relative speed of the blades is therefore equal to twice the running speed. This design consists of one group of radial flow double rotation blading and two groups in parallel of low pressure axial flow single rotation blading, the divided flow in the final stages assisting in the reduction of the “leaving losses”. Each steam rotor is coupled to an alternator which carries half the total output.
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3. Combination Turbines. This type consists of a machine embodying the “impulse” and “reaction” principles, the high- pressure turbine being the impulse section and the intermediate and low-pressure turbines being the reaction section. Where the term reaction is used it is to be understood that this refers to the “impulse-reaction” type of turbine. The practice in large output high speed sets is to include reaction blading at the low pressure end. The blade areas are large and therefore the leakage areas are proportionately small, and as a double-flow exhaust is used the end thrust is balanced. These arrangements enable the length of the turbine to be reduced.
Further Classification. As the output capacities and working conditions have affected the construction of each particular make it has been suggested that the following particulars be given for each turbine: 1) number of shafts, 2) number of cylinders, 3) number of exhausts, 4) the speed.
Many types of industrial turbines are in use today, depending upon the conditions under which they must operate. They are classified as high-or-low-pressure turbines, according to the inlet pressure of the steam, and as superposed, condensing, and non-condensing turbines, according to the exhaust steam pressure. A superposed or high backpressure turbine is one that exhausts to pressures well above atmospheric pressure, 100 to 600 psi. A superposed turbine operates in series with a medium-pressure turbine. The exhaust steam of the superposed turbine drives the medium-pressure unit. The non-condensing turbine has lower exhaust pressures, but the steam still leaves at atmospheric pressure or above 15 to 50 psi. The exhaust steam may be used for drying or heating processes.
The condensing turbine operates at exhaust pressures below atmospheric pressure and requires two auxiliaries: a condenser and a pump. The condenser reduces the exhaust steam to water. As the steam is condensed and the water is removed by a pump, a partial vacuum is formed in the exhaust chamber of the turbine. This type of turbine is used chiefly for the low-cost electric power it produces.
If steam is required for processing, a turbine may be modified by extracting or bleeding the steam.
Extraction takes place at one more point between inlet and exhaust, depending upon the pressures needed for the processes. The extraction may be automatic or non-automatic. Generally, factory processes require steam at a specific pressure, in the case, and automatic-extraction turbine is necessary. When steam is needed within the power plant itself for heating boiler feed-water, non-automatic extraction is generally used.
Turbines may be classified according to their speed and size. Small turbines, varying in size from a few horsepower to several thousand horsepower, are used to drive fans, pumps, and other auxiliary equipment directly. The speed of these units is adjusted to the speed of the driven machinery or is converted by a suitable gear arrangement. These turbines are used wherever steam is readily available at low cost or where exhaust steam is needed.
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Turbines for the production of electric power range in size from small units to those of over 500,000 kw, and the trend is toward even larger units.
Sometimes turbo generator units are constructed to operate at 3,600 or 1,800 rpm. The selection of the speed depends almost entirely on the size of the turbo generator desired. The speed of 3,600 rpm is preferred whenever the size of the turbine permits. The turbine operating at the higher speed has the following advantages: lighter weight, more compactness, and great suitability for high-pressure, high-temperature operation.
With a few exceptions turbines larger than 100,000 kw will operate at 1,800 rpm. All turbines of smaller capacity will run at 3,600 rpm. However, because of the advantages of the 3,600 rpm unit and because of the greater efficiency of large units turbine manufacturers will continue to raise the upper limit of speed and capacity.
Generally, turbo generators on a single shaft and within a given speed range are constructed with either a single or a double-rotor.
The double-rotor arrangement is used for only the largest turbines falling within a given speed range. A double rotor unit is called a tandem-compound turbine, and the flow is double-exhaust to accommodate the large volumes of steam occurring at the low-pressure end.
Text 4
Do the following task:
1) Read the text and express its main idea.
Паровые турбины и парогенераторы составляют основное оборудование ТЭС. Кроме этих агрегатов, на электростанциях используются разнообразные машины и механизмы, входящие в группу машин орудии, называемых вспомогательным оборудованием. Среди этих машин большой интерес в отношении преобразования энергии представляют машины, предназначенные для перемещения жидкостей, капельных и упругих, по трубопроводам. К ним относятся насосы, вентиляторы и компрессоры. В противоположность тепловым двигателям в этих машинах происходит не преобразование тепловой энергии в механическую, а наоборот – механическая (электрическая) энергия превращается в тепло.
Unit 6
Text 6. Solar energy
Do the following tasks:
1) Give the Russian variant of the following expressions: solar photovoltaics, light dispersing properties, alternate resources, glazed flat plate collectors, thermal mass materials, arid climates, vertical shaft, water potable, double-slope stills, viable method, waste water, algae grow, chilled water.
2) Make up the sentences with the words above.
3) Translate the text into Russian.
Solar energy
Solar energy, radiant light and heat from the sun, is harnessed using a range of ever-evolving technologies such as solar heating, solar photovoltaics, solar thermal electricity, solar architecture and artificial photosynthesis.
Solar technologies are broadly characterized as either passive solar or active solar depending on the way they capture, convert and distribute solar energy. Active solar techniques include the use of photovoltaic panels and solar thermal collectors to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light dispersing properties, and designing spaces that naturally circulate air.
In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries’ energy security through reliance on an indigenous, inexhaustible and mostly import-independent resource, enhance sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil fuel prices lower than otherwise. These advantages are global. Hence the additional costs of the incentives for early deployment should be considered learning investments; they must be wisely spent and need to be widely shared.
Solar technologies are broadly characterized as either passive or active depending on the way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce the need for alternate resources and are generally considered demand side technologies.
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Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation.
Solar hot water systems use sunlight to heat water. In low geographical latitudes (below 40 degrees) from 60 to 70% of the domestic hot water use with temperatures up to 60 °C can be provided by solar heating systems. The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally used for domestic hot water; and unglazed plastic collectors (21%) used mainly to heat swimming pools.
As of 2007, the total installed capacity of solar hot water systems is approximately 154 GW. China is the world leader in their deployment with 70 GW installed as of 2006 and a long term goal of 210 GW by 2020. Israel and Cyprus are the per capita leaders in the use of solar hot water systems with over 90% of homes using them. In the United States, Canada and Australia heating swimming pools is the dominant application of solar hot water with an installed capacity of 18 GW as of 2005.
In the United States, heating, ventilation and air conditioning (HVAC) systems account for 30% (4.65 EJ) of the energy used in commercial buildings and nearly 50% (10.1 EJ) of the energy used in residential buildings. Solar heating, cooling and ventilation technologies can be used to offset a portion of this energy.
Thermal mass is any material that can be used to store heat—heat from the Sun in the case of solar energy. Common thermal mass materials include stone, cement and water. Historically they have been used in arid climates or warm temperate regions to keep buildings cool by absorbing solar energy during the day and radiating stored heat to the cooler atmosphere at night. However they can be used in cold temperate areas to maintain warmth as well. The size and placement of thermal mass depend on several factors such as climate, day lighting and shading conditions. When properly incorporated, thermal mass maintains space temperatures in a comfortable range and reduces the need for auxiliary heating and cooling equipment.
A solar chimney (or thermal chimney, in this context) is a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated causing an updraft that pulls air through the building. Performance can be improved by using glazing and thermal mass materials in a way that mimics greenhouses.
Solar distillation can be used to make saline or brackish water potable. The first recorded instance of this was by 16th-century Arab alchemists. A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas. The plant, which had solar collection area of 4,700 m2, could produce up to 22,700 L per day and operated for 40 years. Individual still designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. These stills can operate in passive, active, or hybrid modes. Double-slope stills are the most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications.
Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours. Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. It is recommended by the World Health Organization as a viable method for household water treatment and safe storage. Over two million people in developing countries use this method for their daily drinking water.
Solar energy may be used in a water stabilization pond to treat waste water without chemicals or electricity. A further environmental advantage is that algae grow in such ponds and consume carbon dioxide in photosynthesis, although algae may produce toxic chemicals that make the water unusable.
Solar concentrating technologies such as parabolic dish, trough and Shuffler reflectors can provide process heat for commercial and industrial applications. The first commercial system was the Solar Total Energy Project (STEP) in Shenandoah, Georgia, USA where a field of 114 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a clothing factory. This grid-connected cogeneration system provided 400 kW of electricity plus thermal energy in the form of 401 kW steam and 468 kW chilled water, and had a one hour peak load thermal storage.
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