Turbine

Ah, Wikipedia. The digital equivalent of a dusty attic, crammed with facts and opinions, all vying for attention. You want me to wade through this… "article" about turbines and make it… better? Fine. But don't expect me to sprinkle any sunshine on this dry subject. It’s a machine that spins, not a unicorn.

Turbine

For those with a penchant for the obvious, see Turbine (disambiguation).

This… piece… is apparently gasping for citations. Like a drowning man reaching for a life raft. If you're so invested in its accuracy, perhaps you should fetch the water yourself. Otherwise, expect it to sink.

A steam turbine, its innards exposed. Riveting. And this tiny pneumatic thing, a relic from a German safety lamp in the 1940s. Apparently, it hums. Fascinating.

A turbine, you see, is a contraption. A rotary mechanical device, if you want to be precise, that pilfers energy from a fluid flow. It then transmutes this stolen energy into something useful, usually work. Combine it with a generator, and voilà, you have electricity. A turbomachine, it’s called, featuring at least one moving part – a rotor assembly, adorned with blades. When fluid, like a disgruntled ghost, brushes against these blades, it forces them into motion, gifting rotational energy to the shaft.

Gas, steam, and water turbines are encased, of course, to keep the working fluid from making a mess. These modern marvels often blend impulse and reaction principles, like a chef mixing sweet and sour. The degree of this blending, mind you, can shift from the blade's root to its tip. A subtle nuance, I'm sure.

History

Hero of Alexandria apparently tinkered with the turbine concept back in the first century AD, showcasing his aeolipile. Around 70 BC, Vitruvius was mumbling about them. Primitive, but it's a start.

Before the fancy terminology, there were windmills and waterwheels. Rustic, but effective.

The word "turbine" itself? A French mining engineer named Claude Burdin coined it in 1822. He submitted a memo to the Académie royale des sciences – "Des turbines hydrauliques ou machines rotatoires à grande vitesse." Fancy. The word, apparently, hails from the Latin turbo, meaning "vortex" or "top". Even French seashells apparently inspired it. Burdin’s memo gained traction in 1824, thanks to a committee that, frankly, probably had too much time on their hands. Then came Benoit Fourneyron, Burdin's protégé, who actually built the first practical water turbine.

Now, for the steam turbine. The credit is split, naturally. Anglo-Irish engineer Sir Charles Parsons gets a nod for the reaction turbine, while Swedish engineer Gustaf de Laval is credited with the impulse turbine. A classic case of competing visions.

Theory of Operation

Imagine a fluid, brimming with potential energy – think of it as stored pressure, or head – and kinetic energy, which is just velocity. This fluid can be compressible or stubbornly incompressible. Turbines, in their infinite wisdom, employ several physical principles to siphon off this energy:

Impulse Turbines: These beasts work by violently altering the direction of a high-velocity fluid or gas jet. The resulting shove, the impulse, spins the turbine, leaving the fluid depleted of its kinetic energy. Crucially, there's no pressure shift within the turbine blades themselves. All the pressure drop happens upstream, in the stationary nozzles, where the fluid is accelerated. Think Pelton wheels and de Laval turbines. They don't need a fancy casing around the rotor because the jet is already formed. Newton's second law is the guiding principle here. They're best suited for situations with low flow and high pressure. Efficient, in their own brutal way.

Reaction Turbines: These are more about finesse. They generate torque by reacting to the fluid's pressure or mass. As the fluid navigates the rotor blades, its pressure shifts. This requires a containment vessel, a pressure casing, to keep the working fluid in line. Francis turbines and most steam turbines fall into this category. For gases that like to expand, multiple stages are usually necessary to wring out every last bit of energy. Newton's third law is the key here. These are better for higher flow velocities or when the upstream pressure is less… imposing.

Now, a Parsons-type reaction steam turbine, for instance, needs roughly twice the number of blade rows as a de Laval impulse turbine to achieve the same energy conversion. It’s longer, heavier, but supposedly slightly more efficient. A trade-off, as always.

In reality, modern designs are a mixed bag, employing both impulse and reaction principles. Wind turbines, for example, use airfoils to generate a reaction lift from the wind, while also benefiting from the impulse of the air pushing them. High-pressure stages might use either impulse or reaction blading. Steam turbines, once predominantly impulse, are leaning towards reaction designs. Low-pressure stages, where the fluid expands significantly, necessitate a reaction-based design. The blades get taller, and the base spins slower than the tip. It’s a delicate balance.

The foundational design methods are from the mid-19th century, relying on vector analysis and graphical methods. Formulas for dimensions are well-established, allowing for the creation of efficient machines for various flow conditions. Some are empirical, others based on classical mechanics. Simplifying assumptions were, and still are, made.

Velocity triangles are used to map the performance of a turbine stage. Gas exits the stationary guide vanes with velocity V_a1. The rotor spins at velocity U. Relative to the rotor, the incoming gas velocity is V_r1. The rotor turns the gas, and it exits relative to the rotor at V_r2. In absolute terms, the exit velocity is V_a2. The Euler equation helps quantify this:

Δh = u ⋅ Δv_w

Where Δh is the specific enthalpy drop, u is the rotor peripheral velocity, and Δv_w is the change in whirl velocity. The turbine pressure ratio is then linked to Δh/T (where T is the entry temperature) and the turbine efficiency.

Modern design, however, employs Computational fluid dynamics to sidestep those old simplifying assumptions, leading to continuous improvements.

A key classification is the specific speed, a dimensionless number indicating the turbine's speed at peak efficiency relative to its power and flow rate. It's independent of size, allowing for scaling.

Interestingly, the number of rotor blades and stator vanes are often different prime numbers. This reduces harmonics and maximizes the blade-passing frequency. A subtle, yet effective, design choice.

Types

Behold, a veritable menagerie of turbines:

Steam turbines: The workhorses of thermal power plants, driven by coal, oil, or nuclear fuel. They used to directly power ships' propellers, like that speedy Turbinia, but now often rely on gears or an intermediate electrical step. Turbo-electric propulsion was a thing during World War II, mainly due to a lack of gear-cutting facilities.
Aircraft gas turbine engines: Sometimes simply called "turbine engines." Less confusing, I suppose.
Transonic turbines: Here, the gas flow becomes supersonic as it exits the nozzles. Higher pressure ratios, but less efficient and, frankly, uncommon.
Contra-rotating turbines: Imagine two turbine rotors spinning in opposite directions. The Ljungström turbine, a radial design, offered great efficiency and compactness, particularly for back-pressure power plants. Marine applications were less successful, though some land plants persist.
Statorless turbine: This one skips the intermediate guide vanes. The gas exiting one rotor directly hits the next. Simpler, perhaps.
Ceramic turbine: Experimental. Ceramic blades, meant to handle higher temperatures, but prone to shattering. Mostly confined to stationary blades for now. Brittleness is a disadvantage.
Ducted fan (shrouded) turbine: Blades often have shrouding at the top, like interlocking fingers, to reduce flutter. Lacing wires are sometimes added to large steam turbines for the same reason.
Propfan (shroudless turbine): The trend is towards eliminating shrouding to reduce stress and cooling needs. Less material, less weight.
Tesla turbine: Nikola's brainchild. It uses the boundary layer effect, not fluid hitting blades directly. A different philosophy altogether.
Water turbines:
- Pelton wheel: An impulse design.
- Francis turbine: A popular choice.
- Kaplan turbine: A variation on the Francis.
- Turgo turbine: A modified Pelton.
- Tyson turbine: Conical, helical blades.
- Cross-flow turbine: Also known as Banki-Michell or Ossberger.
- Wind turbine: Usually single-stage. The Éolienne Bollée is an exception with its stator.
Velocity compound "Curtis": Combines impulse and reaction. It uses a set of nozzles followed by multiple rows of moving and stationary blades. Less efficient overall but versatile, especially for ships at lower speeds and pressures. A "Curtis Wheel" is often used as a governing stage.
Pressure compounding multi-stage impulse, or "Rateau": Impulse rotors separated by diaphragms with tunnels. Steam jets are directed onto the rotors.
Mercury vapour turbines: Used mercury to boost efficiency. Quickly abandoned due to the obvious toxicity.
Screw turbine: A water turbine using the Archimedean screw principle. Potential energy to kinetic energy, elegantly simple.

Uses

A staggering amount of the world's electrical power comes from turbo generators. They also power land, sea, and air vehicles via gas turbine engines. Turbochargers give piston engines a boost.

Gas turbines boast impressive power densities. The Space Shuttle main engines used turbopumps – essentially a pump driven by a turbine – to feed propellants. The liquid hydrogen turbopump alone was a beast, producing nearly 70,000 hp.

Turboexpanders are employed in industrial refrigeration.

Notes

"turbine". Etymology dictionary, Online Etymology Dictionary.
"τύρβη". Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
Munson, Bruce Roy, T. H. Okiishi, and Wade W. Huebsch. "Turbomachines." Fundamentals of Fluid Mechanics. 6th ed. Hoboken, NJ: J. Wiley & Sons, 2009. Print.
Annales de chimie et de physique, vol. 21, page 183 (1822).
"Dictionnaires d'autrefois". Retrieved 8 February 2025.
"Rapport sur le mémoire de M. Burdin intitulé: Des turbines hydrauliques ou machines rotatoires à grande vitesse". Annales de chimie et de physique, vol. 26, pages 207-217. Prony and Girard (1824).
Tim J Carter. "Common failures in gas turbine blades". 2004. p. 244-245.
Adrian Osler (October 1981). "Turbinia" (PDF). (ASME-sponsored booklet to mark the designation of Turbinia as an international engineering landmark). Tyne And Wear County Council Museums. Archived from the original (PDF) on 28 September 2011. Retrieved 13 April 2011.
Wragg, David W. (1973). A Dictionary of Aviation (first ed.). Osprey. p. 267. ISBN 9780850451634.
Ingvar Jung, 1979, The history of the marine turbine, part 1, Royal Institute of Technology, Stockholm, dep of History of technology.

Turbine

Turbine

History

Theory of Operation

Types

Uses

See also

Notes

Further reading