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Turbine (I)

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发表于 6-8-2022 13:48:25 | 显示全部楼层 |阅读模式
For about two decades, I have not been able to understand aircraft engines: what are purpose of compressor, combustion or turbine? Which is chichen and which is egg (that is, which starts the engine)? What are the relative contribution of the three (compressor, combustion or turbine)?

(1)
(a) turbine
https://en.wikipedia.org/wiki/Turbine
("from the Greek τύρβη, tyrbē, or Latin turbo, meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. * * * A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels. * * * Credit for invention of the steam turbine is given both to Anglo-Irish engineer Sir Charles Parsons (1854–1931) for invention of the reaction turbine [in 1884 in England], and to Swedish engineer Gustaf de Laval (1845–1913) for invention of the impulse turbine ['in 1880s': Wikipedia]. * * * The word 'turbine' was coined in 1822 by the French mining engineer Claude Burdin from the Greek τύρβη, tyrbē, meaning 'vortex' or 'whirling' ")

section 1 Operation theory: impulse turbine and reaction turbine

section 2 Types: steam turbine, gas turbine, water turbine, wind turbine, among others.

Note:
(i)
(A) Ancient Greek-English dictionary:
* τύρβη (noun feminine; romanization: túrbē): "disorder, confusion, tumult"
https://en.wiktionary.org/wiki/τύρβη
(B) Latin-English dictionary:
* turbo (noun masculine): "1: tornado, whirlwind
2: spinning top, wheel
3: spinning motion"
https://en.wiktionary.org/wiki/turbo
(ii) impulse (physics)
https://en.wikipedia.org/wiki/Impulse_(physics)
("a force, F, over the time interval, t, for which it [force] acts. Since force is a vector quantity, impulse is also a vector quantity")
(iii) A steam turbine uses steam (produced by heating water) to rotate a turbine. James Watt first created Watt steam engine (NOT turbine) in 1776.
(iv) Impulse and reaction turbine will be discussed next.


(b) Chris Woodford, Turbine. ExplainThatStuff, last updated: Jan 13, 2022
https://www.explainthatstuff.com/turbines.html

Quote:

(i) "In an impulse turbine, a fast-moving fluid is fired through a narrow nozzle [in a fixed location] at the turbine blades to make them spin around. The blades of an impulse turbine are usually bucket-shaped so they catch the fluid * * * In a reaction turbine, the blades sit in a much larger volume of fluid and turn around as the fluid flows past them. A reaction turbine doesn't change the direction of the fluid flow as drastically as an impulse turbine: it simply spins as the fluid pushes through and past its blades. Wind turbines are perhaps the most familiar examples of reaction turbines. * * * Turbines capture energy only at the point where a fluid touches them, so a reaction turbine (with multiple blades all touching the fluid at the same time) potentially extracts more power than an impulse turbine the same size (because usually only one or two of its blades are in the path of the fluid at a time).

(ii) "Thinking backwards [which is sectional heading]

"You might have noticed that wind turbines look just like giant propellers—and that's another way to think of turbines: as propellers working in reverse. In an airplane, the engine turns the propeller at high speed, the propeller creates a backward-moving draft of air, and that's what pushes—propels—the plane forward. With a propeller, the moving blades are driving the air; with a turbine, the air is driving the blades.

"Turbines are also similar to pumps and compressors [this Web page does not discuss comparison with compressor]. In a pump, you have a spinning paddle wheel that sucks water in through one pipe and throws it out from another so you can move water (or another liquid) from one place to another. If you take a water pump apart, you can see the internal paddle wheel (which is called an impeller) is very similar to what you'd find inside a water turbine. The difference is that a pump uses energy to make a fluid move, while a turbine captures the energy from a moving fluid.

(iii) "Turbines in action [sectional heading]

"Broadly speaking, we divide turbines into four kinds according to the type of fluid that drives them: water, wind, steam, and gas. Although all four types work in essentially the same way—spinning around as the fluid moves against them—they are subtly different and have to be engineered in very different ways. Steam turbines, for example, turn incredibly quickly because steam is produced under high-pressure. Wind turbines that make electricity turn relatively slowly (mainly for safety reasons), so they need to be huge to capture decent amounts of energy. Gas turbines need to be made from specially resilient alloys because they work at such high temperatures. Water turbines are often very big because they have to extract energy from an entire river, dammed and diverted to flow past them. They can turn relatively slowly, because is water is heavy and carries a lot of energy (because of its high mass) even when it flows at low speeds.

(iv) Steam turbines (which is SUBsectinal heading)

"Steam turbines evolved from the steam engines that changed the world in the 18th and 19th centuries. A steam engine burns coal on an open fire to release the heat it contains. The heat is used to boil water and make steam, which pushes a piston in a cylinder to power a machine such as a railroad locomotive. This is quite inefficient (it wastes energy) for a whole variety of reasons. A much better design takes the steam and channels it past the blades of a turbine, which spins around like a propeller and drives the machine as it goes.

"Unlike water and wind turbines, which place a single rotating turbine in the flow of liquid or gas, steam turbines have a whole series of turbines (each of which is known as a stage) arranged in a sequence inside what is effectively a closed pipe. As the steam enters the pipe, it's channeled past each stage in turn so progressively more of its energy is extracted. If you've ever watched a kettle boiling, you'll know that steam expands and moves very quickly if it's directed through a nozzle. For that reason, steam turbines turn at very high speeds—many times faster than wind or water turbines.

(v) "Gas turbines [subsectonal heading]

"Airplane jet engines are a bit like steam turbines in that they have multiple stages. Instead of steam, they're driven by a mixture of the air sucked in at the front of the engine and the incredibly hot gases made by burning huge quantities of kerosene (petroleum-based fuel). Somewhat less powerful gas turbine engines are also used in modern railroad locomotives and industrial machines. See our article on jet engines for more details.

Note:
(i) impeller
https://en.wikipedia.org/wiki/Impeller
(ii) impel (transitive verb; Impel vs Compel): "2: to impart motion to : PROPEL"
https://www.merriam-webster.com/dictionary/impel


(c) Chris Woodford, Jet Engines. ExplainThat Stuff, last updated Dec 11, 2021.
https://www.explainthatstuff.com/jetengine.html
("So, in a jet engine, exhaust gas powers a turbine [this statement is only half a story, failing to consider exhaust that ALSO pushes the aircraft forward. See next in this citation] —hence the name gas turbine. * * * But not all jet engines work this way: some produce hardly any rocket exhaust at all. Instead, most of their power is harnessed by the turbine—and the shaft attached to the turbine is used to power a propeller (in a propeller airplane) [turboprop], a rotor blade (in a helicopter) [turboshaft], a giant fan (in a large passenger jet) [turbofan] * * * • Compressor: Dramatically increases the pressure of the air (and, to a lesser extent) its temperature")

You may stop at the section that includes the last sentence of the quotation above, plus the additional section titled "Types of jet engines."
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