Charles Parsons and Turbines

Charles Parsons

We all grew up with the story that James Watt watched a tea kettle boil and invented the steam engine. Rarely do we wonder why the Chinese tea makers never invented a steam engine. In school books, we also read that Faraday discovered electricity or that Thomas Edison invented the light bulb. Even those of us who study physics or engineering later, rarely wonder why Faraday did not invent the light bulb. The nerdier, and more widely read people, know how vital Nikola Tesla’s experiments with Alternating Current were to the modern electrical world.

Of late, Tesla versus Edison has become a cult battle, with “kind, brilliant, public spirited” Tesla who wanted to make electricity free for the whole world winning hearts over cunning, capitalist, greedy, jealous, stubborn Edison, the latter approaching Voldemort in his villainy.

 

Ungrateful world. This is sad ignorance of basic economics and about Parsons and turbines. I would strongly recommend Vaclav Smil’s “Creating the Twentieth Century” to get a more realistic (and less cartoonish) perspective.

But today June 13, is Charles Algernon Parsons’ birthday, and since he is almost completely unknown to all but mechanical engineers, I’ll explain his vital role in making the modern world.

Edison invented the Electric Age (not just a working light bulb), the Spirit of Invention, the Corporate Research Lab, the Phonograph, ad infinitum. I rate Edison as the Man with the greatest impact and transformation of human history and civilization; not just the greatest inventor or engineer. The ones who surpassed him were the inventors of  Fire, Wheel, Agriculture, Cotton etc. whose names are lost in the mists of time. 

Energy and Transportation

Edison massively influenced Energy but not Transportation. James Watt’s steam engine influenced both, and there would be no Electric Age without steam engines – as coal fired power plants.

So did Parsons – his turbines are vital:

1. For electric power – 75% of the world’s power is generated by steam turbines (not steam engines) in coal and nuclear power plants.
2. In jet aircraft engines and large ships
3. For powering the compressors used in the Haber-Bosch process, which helps feed the world.

Engines versus Turbines

Not being a mechanical engineer, and not having read much on engineering until recently, I didn't properly understand the difference between engines and turbines, and how much more efficient the latter are, until I read Vaclav Smil’s book Creating the Twentieth Century. And I did not realize how vital turbines are until I read his other book Prime Movers of Globalization – here is Bill Gates’ somewhat concise review of Smil's book.

James Watt did not invent the steam engine. Others like Savery and Newcomen made working steam engines before him. Their engines are atmospheric engines. Steam pushed up the pistons in their cylinders, but then the whole cylinder was cooled, the steam condensed, and then the piston fell down due to atmospheric pressure pushing downwards. 

 

Watt’s great breakthrough was to devise an external condenser, which made the steam engine efficient and useful, and to invent several instruments which helped to incrementally improve the steam engine. Also Watt built stationary steam engines, which replaced water mills as power sources in factories. He never built a steam locomotive, as in railways.

Richard Trevithick, George Stephenson and others increased its mass/power output ratio, leading to railways and cheap transportation as we know it. But these are reciprocating engines and still use steam power inefficiently. 

Fundamentally, a steam turbine is a specialized steam engine, which doesn’t have a piston, but has multi stage rotors and stators. Steam engines use the pressure of the steam to move the piston – which is the mechanical work. Turbines, also utilize the velocity and pressure to do the mechanical work. High pressure steam powers rotors blades, arranged in a circle around a central axis. The steam flows through these rotors after having propelled them and goes through a set of stators, which constrict the steam thus increasing its velocity. This steam passes through a second set of rotors and stators, then a third set and so on until it no longer has significant pressure to do much mechanical work. Thus turbines are phenomenally more efficient than piston-based engines.

Compound Turbine - Flow of Steam and Working method

Water turbines and windmills had been in existence for centuries. But the metal blades that could withstand the pressure of steam were far beyond the metallurgical capabilities of any country in Europe, or even Britain its leading industrial power, until the invention of Bessemer steel in the 1850s. The velocity of even low pressure steam is calculated as 2500 feet per second or 1700 miles per hour. At those speeds, centrifugal force would tear apart any metal blade used as a rotor. Even James Watt knew this, and expressed it thus when his partners wondered if their business would face competition from steam turbines: “Without God makes it possible for things to move at 1000 feet per second, it cannot do much harm.”

The Parsons Turbines

Bessemer steel and improvements in metallurgy and science changed that. In 1882, Gustaf Patrick de Laval made an impulse steam turbine. And in 1885, Charles Parsons made a small turbine producing 7.5KW.  Parsons’ key insight was to slow down the speed of the jet of steam in a series of steps, each partial drop of pressure being sufficient to power rotor blades that wouldn’t fall apart under the high speed. The principle of subdividing the velocity of steam into a series of steps, so that only moderate speeds are produced, remains the basis of all efficient turbine design.

First Parsons had to invent a new type of blade for the rotors, which would not collapse in a turbine operating fifty times faster than the reciprocating eninges of the time. He had to invent methods to manufacture these blades. Parsons also invented new types of bearings, to handle long rotors to function without damage from vibration at high speeds. He invented a way to continuously lubricate these bearings. Besides stages of rotors, he also invented midway inlet, into the casing of the turbine, so steam would flow in both directions. Subsequently he invented dummy pistons, which rendered double flow princinple unnecessary for smaller turbines.

Parsons revolutionized the efficient use of steam on a scale that neither Trevithick nor Stephenson could have imagined. The power of steam was multiplied a hundredfold. It affected not merely the size and scale of transportation, but also electric power generation and other industries in unthinkable ways.

 

When Edison dazzled the US with his Electric Lighting in 1879, he used a steam engine to generate power. As Smil rightly notes, it is the total design and planning of the electrical system needed to bring electric lighting, that was Edison’s giant transformation of the world. Edison’s use of DC, Tesla’s advocacy of AC, and Westinghouse’s triumph are well known to those who know the history of electricity. But Parsons’ role, and the role of steam turbines, is not properly understood; usually unknown, except to mechanical engineers.

Alternating current is what enables cheap distribution of electricity. Without AC (or transformers), we would need power plants every few miles. Imagine the pollution, the logistics, the cost!

But AC only improves distribution, not the production of power. Here Tesla’s role ends. Early steam engines produced very little power for the amount of coal used. Steam turbines not only delivered more power, but massively improved the output per amount of coal used, as this table shows. Steam engines between 1890 and 1904 showed maximum thermal efficiency of 11-17%. It made no sense, economic or engineering, to install steam engines, rather than turbines, after 1902, says Smil.

Year	Turbine Power in KW	Efficiency in %
1885	7	1.6
1888	75	5.0
1899	1000	25.0
1912	2500	75.0

I have left out the delightful story of Parson’s ship SS Turbinia, his stunt during a naval parade, and its impact on the British Navy, and later all shipping. 

This essay mainly outlines the impact of Parsons' improvements to turbine design and manufacture and their critical importance to the modern world. For more details on the engineering aspects of his work, and a brief biography, please read this.

Note: I edited this on September 17, 2021 by adding a few paragraphs about some components of turbine design.

References

Creating the Twentieth Century, by Vaclav Smil

How a turbine works

The Steam Turbine and other inventions of Sir Charles Parsons, by R.H. Parsons

Westinghouse or Tesla – who should we credit for Alternating Current : Kathy Joseph’s video 

Related blogs

I had earlier blogged in Tamil about Vaclav Smil on Edison.

Inventors and Discoverers