Практика Shadowing: Aircraft Gas Turbine Engines #01 - Introduction Part 1 - Изучайте разговорный английский по видео
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Jet propulsion can be defined as the force
Реактивная тяга может быть определена как сила
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which is generated in the opposite direction to that of a discharge of fluid under pressure escaping through an opening.
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The force that makes a lawn sprinkler, similar to the one shown here, rotate when water flows through it is one example of jet propulsion that is readily apparent in everyday life.
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and the thrust that sends rockets like this one into space is another, which is perhaps not such an everyday occurrence.
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Whatever the form that the device utilizing jet propulsion takes,
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it is essentially a reaction engine which operates on the principle of the third law of motion, as stated by the English physicist Sir Isaac Newton in 1687,
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which is that every reaction has an equal and opposite reaction.
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The first recorded use of a reaction engine was by Hero of Alexandria in 250 BC.
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Hero's engine, a representation of which is shown here, consisted of a sphere into which steam was introduced under pressure.
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The steam was fed through apertures in the centre of the bearings upon which the sphere was allowed to rotate.
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Allowing the steam to escape through nozzles in two bent tubes
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mounted opposite one another on the surface of the sphere created thrust, which caused the sphere to rotate around its axis.
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It's alleged that Hero invented his engine while he was investigating different methods of opening the doors of a temple in Alexandria.
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In recent times, one of the first attempts at creating jet-powered aircraft resulted in the development of a hybrid design.
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An Italian, Secondo Campini, designed a system whereby an external power source, in this case a conventional piston engine, powered a compressor.
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The output of the compressor was mixed with fuel, the mixture of air and fuel ignited, and jet thrust resulted.
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collaborated with the Italian aircraft manufacturers Caproni, and in August of 1940, the Campini Caproni CC2 flew.
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Although the Italians were unaware of it, a year earlier than this the Germans had flown their version of a jet aircraft, the Henkel 178.
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This aircraft was powered by an engine designed by a young German scientist called Hans von Ohain.
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Despite the relatively sparkling performance for that era it could travel at speeds in excess of 400 miles per hour,
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the German Air Force initially paid its scant regard and it was never produced in any quantity.
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On the 8th of April 1941, the first official flight of the Gloucester E-2839 aircraft took place at Brockworth in Gloucestershire.
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Sir Frank Whittle had submitted patents for his jet engine in 1930, but it was not until 1939 that sufficient financial
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and technical backing was found to enable him to manufacture a flyable version of his engine.
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The firm of Rover had, reluctantly, initially been contracted to produce the Whittle engine, but Rolls-Royce, who could see its potential,
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eventually took over development of the engine, one of which is shown here.
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Rolls-Royce reworked the Whittle design to produce the Derwent engine, an example of which is depicted here.
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This engine was capable, in its Mark IV version, of producing 2,450 pounds of thrust.
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Later versions of the engine, capable of 3,600 pounds of thrust, were used to power the Gloucester Meteor F-8, like the one shown here,
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flying at an open day at Royal Air Force Kemble in the year 2000.
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During a visit to the United States in early 1944, the leader of the Rolls-Royce design team found
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that General Electric were developing engines capable of producing up to 4,000 pounds of thrust.
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As a response to this, after his return, he initiated a project which culminated in the Neen engine, which at the time was the most powerful engine in the world,
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with 5,000 pounds of thrust.
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Possibly one of the most important but least publicized uses of this engine was its incorporation into the Russian MiG-15 aircraft, which was so effective in the Korean conflict.
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One critical difference between the German engines used in the Heinkel and the later Messerschmitt 262, and those developed from Sir Frank Whittle's original engine,
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was the type of compressor employed.
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While the Whittle engine used a centrifugal compressor, similar to the example shown here,
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the German engines, like the BMW 003 model used in the Heinkel 162,
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utilized an axial flow compressor similar in design to the cutaway model shown.
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Axial flow compressors have several advantages over the centrifugal compressor.
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For instance, whereas the centrifugal compressor compression ratio is limited to approximately 12 to 1, when the maximum of two stages are used in series,
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by adding more stages to an axial flow compressor, compression ratios as great as 40 to 1 can be obtained.
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The term compression ratio refers to the ratio of the pressure at the outlet of a compressor to that at its inlet.
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A second advantage of the axial flow compressor, almost as important as the first, is that the mass flow
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which can be obtained through an axial flow compressor is potentially much greater than the mass flow
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which can be achieved through a centrifugal compressor.
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As a consequence of these factors, the development of the early centrifugal compressor engines was subjugated in favor of the advancement of the axial flow compressor engines,
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which continues today.
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The principle of the gas turbine engine is basically the same as that of the piston engine propeller combination.
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They both propeller mass of air backwards.
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Mass times acceleration equals force.
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In a gas turbine engine the mass, m, mentioned in the equation is the air delivered by the compressor.
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The acceleration in the equation is the difference in the outlet velocity of the air, V0, to that of its inlet velocity,
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V1, due to the addition of heat energy.
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Force equals mass times V0 minus V1, which equals thrust.
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With the piston engine propeller combination, the propeller drives a relatively large mass of air backwards fairly slowly,
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while the gas turbine throws a small mass of air backwards relatively quickly.
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Newton's third law states, for every force acting on a body there is an equal and opposite reaction.
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In the two cases quoted earlier, the piston engine propeller combination and the gas turbine engine,
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the force created by the mass of air being thrown backwards and its velocity generates a reaction in the opposite direction, driving the aircraft forwards.
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It must be remembered that the jet reaction does not result from the pressure of the jet on the atmosphere.
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In all instances the resultant reaction
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or thrust exerted on the engine is proportional to the mass
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or weight of the air expelled by the engine and the velocity change imparted to it.
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The working cycle of the gas turbine engine is called the Brayton cycle after George Brayton, an American mechanical engineer who invented the continuous ignition engine,
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which was the basis of the gas turbine engine.
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The Brayton cycle and the working cycle of the four-stroke piston engine, the Otto cycle, are very similar as can be seen in this diagram.
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The induction, compression, Power and exhaust strokes of the Otto cycle are each matched by induction,
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compression, combustion and exhaust stages in the Brayton cycle.
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One major difference however exists in that in the gas turbine engine combustion theoretically occurs at a constant pressure,
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whereas in the piston engine it occurs, once again theoretically, at a constant volume.
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Power is developed in the turbine of the engine.
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Other differences between the piston engine
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and the gas turbine engine concern the continuous manner in which these processes occur in the gas turbine engine,
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as opposed to the intermittent procedure occurring in the piston engine.
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In the piston engine, only one of the strokes is utilized in producing power.
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The other three are effectively absorbing power, while in the gas turbine engine, the three idle strokes have been eliminated,
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thus allowing more time for the burning of fuel.
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This is just one of the reasons why the gas turbine engine has a greater power-weight ratio than the piston engine.
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The pressure volume diagram shown here, otherwise known as the Brayton cycle, represents the working cycle of the gas turbine engine in its simplest form.
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Air, at atmospheric pressure, enters the engine at point A and is compressed along the line AB.
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is added in the combustion chambers, which is signified by point B, and the mixture is burnt, in theory at a constant pressure.
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In fact, the reduction in pressure shown between points B
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and C indicates that pressure losses do actually occur in the combustion chamber.
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The drop in pressure is created by the need to produce the swirl and turbulence necessary for efficient combustion,
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and this causes a pressure drop throughout the combustion chamber length of between 3 to 6%.
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Notwithstanding this drop, a considerable increase in the volume of the air is generated within the combustion chamber.
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Between points C and D, the gas generated through combustion expands in the turbine,
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where mechanical power is extracted from the energy in the gas stream,
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and the jet pipe, where the remainder of the gas stream energy provides a propulsive jet as it's discharged.
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In theory, the gas stream pressure attains a value equal to atmospheric pressure before being ejected.
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Контекст и основы
Видео рассказывает о истории реактивных двигателей, начиная с древних изобретений и заканчивая современными разработками. Это отличный материал для тех, кто хочет улучшить практику разговорного английского, так как он сочетает научные термины с простым объяснением. Слушая его, вы узнаете, как работает реактивная тяга, познакомитесь с первыми самолетами и разберете разницу между типами компрессоров. Это не только познавательно, но и помогает привыкнуть к английскому языку в контексте технической темы.
5 ключевых фраз для повседневной коммуникации
- "Jet propulsion can be defined as..." — Как определить реактивную тягу. Удобно для объяснений.
- "operates on the principle of..." — Работает по принципу... Полезно для описания механизмов.
- "a critical difference between..." — Ключевое различие между... Отлично для сравнений.
- "as a consequence of these factors..." — В результате этих факторов... Хорошо для выводов.
- "the principle of... is basically the same as..." — Принцип... по сути тот же, что и... Удобно для упрощения объяснений.
Пошаговое руководство по shadow speak
Чтобы эффективно заниматься shadowspeaks на этом видео, следуйте этим шагам. Сначала прослушайте отрывок длиной 10-15 секунд, запомните интонацию и ритм. Затем повторите его вслух, пытаясь подражать звукам и темпу. Если что-то не получается, остановите видео и повторите отдельные слова. Пracтикуйте каждый отрывок 3-5 раз, пока не почувствуете уверенность. Помните, shadow speak помогает улучшить произношение и реакцию. Начните с простых фраз, а потом переходите к более сложным предложениям. Это отличный способ учить английский по видео и стать более уверенным в разговоре!
Грамматика в этом видео
Конструкции, которые говорящий использует чаще всего, с точными словами из видео:
| Конструкция | В видео |
|---|---|
| Пассивный залог be + причастие прошедшего времени — важно, что происходит, а не кто это делает | can be defined · is generated · is shown |
| Придаточные определительные who / which + предложение — уточнение о человеке или предмете | another, which is · aircraft, which was · chambers, which is |
Что такое техника Shadowing?
Shadowing — это научно обоснованная техника изучения языка, изначально разработанная для подготовки профессиональных переводчиков и популяризированная полиглотом доктором Александром Аргуэльесом. Метод прост, но эффективен: вы слушаете аудио на английском от носителей языка и немедленно повторяете вслух — как тень, следующая за говорящим с задержкой в 1–2 секунды. В отличие от пассивного прослушивания или грамматических упражнений, Shadowing заставляет мозг и мышцы рта одновременно обрабатывать и воспроизводить реальные речевые паттерны. Исследования показывают, что это значительно улучшает точность произношения, интонацию, ритм, связную речь, понимание на слух и беглость речи — что делает его одним из самых эффективных методов для подготовки к IELTS Speaking и реального общения на английском.