What a Diesel Engine Is

A diesel engine is a machine which produces power by burning oil in a body of air which has been squeezed to a high pressure by a moving piston. Since it is a machine that produces power, it is called an engine, and since the burning or combustion takes place within the engine itself, it is called an internal-combustion engine. A steam engine uses steam made by burning fuel outside the engine. That is external combustion.

To compress the air, put in the oil, and produce power, every diesel engine must have certain basic parts. It must have a round sleeve, or cylinder, in the bore of which a close-fitting plug or piston can slide in and out to make strokes. The piston must be connected to a mechanism which controls its sliding. For this purpose ordinary engines use a crank mechanism. This consists of, first, a round bar or shaft which can turn or revolve in circular guides called bearings and which has an offset or crank (which turns in a circle when the shaft revolves), and, second, a connecting rod which, as the name implies, connects the crank to the piston. The connecting rod is a straight rod with a bear­ing at each end. The crank mechanism (which is also used in many other kinds of machinery) is a device for converting the in-and-out motion of the piston to rotating motion of the crankshaft. The power produced by the engine is taken off the crankshaft.

Other basic parts are necessary. Valves or ports are needed to let the air into the cylinder, and also to let out the burned or spent gases after they have done their work. Also a spray nozzle, or fuel injector, is needed to deliver the oil for burning in the form of a finely divided spray. (It works something like the nozzle on a garden hose.) To do this the oil must be put under pressure. This is accomplished by a pump which is called a fuel-injection pump.

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Steam Turbines

Turbines have developed to their present forms along various lines according to steam conditions, condensing water available, types of service, and requirements as to cost and economy; and this process is still going on, with all builders continually changing, experimenting with and improving their product. There has been a growing amount of standardization of the smaller sizes of machines, but not until the urgent requirements of the Second World War forced it was there a serious attempt to standardize the operating conditions and certain physical characteristics of the units in the range from 11,500 to 60,000-kw rating.

Definitions – A steam turbine may be defined as a form of heat engine in which -the energy of the steam is transformed into kinetic energy by means of expansion through nozzles, and the kinetic energy of the resulting jet is in turn converted into force doing work on rings of blading mount­ed on a rotating part.

The usual turbine consists of four fun­damental parts: the rotor which carries the blades or buckets; the stator consisting of cylinder and casing, which are often com­bined and within which the rotor turns; the nozzles or flow passages for the steam, which are generally fixed to the inside of the cylinder; and the frame or base for supporting both the stator and the rotor, the latter being carried in bearings. Cylinder, casing, and frame are often combined, particularly in small turbines. Accessories necessary for the successful continuous commercial operation are a controlling or governing system for adjusting the energy supply to the turbine to suit the load to be carried and for maintaining constant speed, a lubricating system, piping for steam supply and exhaust, and (for economical power generation in large quantities) a condensing system.

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а) по каким двум направлениям ведутся исследования в этой области;

б) над какими уже известными моделями производства электричества ведется работа;

в) каковы преимущества электромобиля.

Researchers are trying to develop new systems of generating electricity, some of which involve new sources of energy. One part of this research has concentrated on finding a new source of power to drive the turbine such as the kinetic energy (energy that comes from motion) of the wind and tides. Another line of research attempts to develop other known but so far impracticable methods for generating electricity. These include piezoelectricity – electricity that comes from pressure or weight applied to certain kinds of crystals. More promising is thermoelectricity, or the generation of electricity through heat. When the joint between two different metals is heated, a weak electromotive force is created. The joint is called a thermocouple, and several thermocouples joined in a series, like cells in a battery, increase the electromotive force. Thermo­electric generators, with heat supplied from radioactive materials, have been used in equipment for the space program. The action of light on some substances can also produce a release of electrons with an electromotive force. This effect is known as photoelectricity. It is familiar to most of us in the photoelectric cells that open and close automatic doors when a beam of light is broken.

Finally, attempts are being made to improve the means of producing electricity from chemical reactions in cells and batteries. Although electric cars powered by batteries have existed for a long time, they still cannot compete with cars powered by internal combustion engines, which burn increasingly scarce and expensive gasoline. There have been some promising discoveries in battery research, which may hasten the development of a practical battery-powered car. An electric car produced at a low enough price and with a long enough operation time would offer two advantages over the internal combustion engine: it would save fuel and avoid further pollution of the atmosphere.

• Используя информацию текста, ответьте на следующие вопросы.

1 What sources of power could be used to drive the turbine? 2 What is the name for electricity that comes from pressure applied to certain crystals? 3 Does thermoelectricity create a strong or weak electromotive force? How can the force be strengthened? 4 Where have thermoelectric generators been used? 5 How is photoelectricity produced? 6 What is a familiar example of the use of photoelectricity? 7 What is being done to improve electric cars? 8 What advantages would electric cars have over those with internal combustion engines?