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Steam Engine

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Mechanical Features and Designs
Steam Locomotive, Essex, Connecticut, 12/18/2004
A steam engine is a mechanical device or machine that converts the heat energy of steam into mechanical energy through the movement of a piston inside a cylinder. A steam engine can also be classified as a type of external combustion engine because it burns fuel outside the engine.[1]

The invention of the steam engine largely propelled the advancement of the Industrial Revolution and was the first engine to ever be adopted into wide use in the powering of everything from locomotives, to steamboats, to factories, and even some of the very first automobiles.[2]


[edit] History

The principle of steam power was actually a concept that was toyed around with by the Greeks during the first century A.D. Hero, a Greek engineer and mathematician, devised a crude steam engine type invention called an aeliopile that consisted of a steam-producing boiler attached to small hollow sphere with two tubes. The invention was built in a context of playfulness and other inventions such as a steam organ and automatic doors were also designed in the same matter and never for the purpose of exploiting steam for practical application. Despite this, the Greeks were the first civilization to establish the principle of steam power.

[edit] Papin’s Pressure Cooker

The idea of steam power lay dormant for about 1,500 years until being resurrected in Europe by French physicist Denis Papin in 1680. Within this 1,500-year time frame, people had to largely rely both on manual power and draft animals. Wind and waterpower were later utilized to carry out slow, repetitive tasks such as mill grinding. Papin’s steam engine was actually the world’s first pressure cooker and spurred out of necessity for a power source that could adequately pump water out of coalmines more quickly than the water-powered pumps used at the time. Papin realized he had created the world’s first steam engine when he placed water in the bottom of a tube, heated it, converted it to steam, and watched as the steam expanded, generating enough force to move a piston ahead of it. Once the piston cooled down, it returned to its former position. Papin, overwhelmed by the mechanical difficulties presented in adapting his invention to a larger-scale workable version, chose to focus on a small-scale model instead.[3]

[edit] The Miner’s Friend

Based on Papin’s original pressure cooker type design, Thomas Savery, an English engineer and inventor, built the world’s first workable steam engine, patented in 1698. Savery too was concerned with finding a solution for pumping water out of coalmines.[4] The operation of his machine, the “Miner’s Friend,” involved connecting a vessel to a tube that led to the water below and creating a vacuum that drew the water back up through the tube and then blew it out by steam pressure. The difference from Papin’s design was that the Miner’s Friend machine featured no piston and was exclusively used to draw up water.[5]

Full Scale Working Replica of Thomas Newcomen's Steam Engine, circa 1712

[edit] The Atmospheric Steam Engine

Savery later partnered with an English blacksmith by the name of Thomas Newcomen to reintroduce the piston into his original design. The collaboration led to the introduction of the Newcomen steam engine in 1712 that relied on atmospheric pressure (ordinary boiling water) to do mechanical work.[6] The engine worked by pumping steam into a cylinder that was then condensed by cold water. This created a vacuum inside the cylinder resulting in an atmospheric pressure that operated a downward stroking piston.[7] The Newcomen steam engine, also called a beam engine because of a large rocking-arm positioned on top that was used to transfer power from the cylinder to the water pump, was relatively easy to build and very reliable with wide use adoption occurring around 1725.[8]

[edit] Automation of the Steam Engine

Perhaps the most substantial improvement made to the steam engine took place in 1763 when a Scottish engineer by the name of James Watt was asked to repair a Newcomen steam engine. Watt noticed inefficiency in the performance of Newcomen’s steam engine right away. Contributing to the problem was the fact that the machine lacked a separate condenser and quickly cooled down. With a separate condenser the heating and cooling processes could be kept separate allowing the machine to work at a constant rate instead of having to wait long periods between each reheating cycle. What Watt achieved in his work was to design the steam engine as a self-regulated and therefore, automated machine.[9] By 1790, Watt’s steam engine was a power source that could be situated practically anywhere, meaning factories no longer had to be based next to water but could move closer to raw materials and transportation systems. His steam engine became the dominant design for all steam engines that followed. Inevitably, the genius of this one change in Newcomen’s design precipitated the advancement of the Industrial Revolution in Europe and eventually throughout the rest of the world.[10]

[edit] Low-pressure vs. High-pressure Steam Engines

One drawback of Newcomen’s engine was that it used steam at low pressure. High-pressure steam in small engines translated into greater power but was also more dangerous since poorly made boilers being produced at the time were known to explode. In 1803, Richard Trevithick, an English inventor, was convinced that he could deliver a system that could handle high-pressure steam. He proceeded to build a high-pressure steam engine that was powerful enough to fully operate a locomotive. But despite this technological development, it took another 20 years before high-pressure steam engines were well established. This was partly due to the negative reputation they had already received for exploding.[11]

[edit] The High-pressure Steam Engine

The U.S. lagged way behind Europe in the development of steam engines. Near the end of the 18th century, however, the country caught up when Oliver Evans began developing a high-pressure steam engine that could act as a stationary power source for industrial purposes as well as land and water transportation. Within a 50-year span, he built over 50 steam engines that were used in factories and even to power a dredger that could operate on land and in water, making it the first actual powered road vehicle in the U.S. American manufacturers, however, were somewhat reluctant to convert to steam, choosing rather to rely on old methods. Poor roads, a reliance on horsepower, and poor building materials all contributed to the very slow adoption of steam power in the U.S. However, with time and access to iron rather than timber to build engines, Evans' high-pressure steam engine became widely accepted and catapulted American industrialization.[12]

[edit] The Steam Turbine Engine

During the 1880s, English engineer Charles A. Parsons invented the very first steam turbine engine that produced mechanical energy and electrical energy simultaneously. The steam engine had evolved into a very powerful engine that could now power large ocean liners and run electrical turbo-generators.[13]

[edit] Features/How it Works

The high-pressure steam for a steam engine came from a boiler. The function of the boiler was to heat the water so it would produce steam.

During the 1800s, the primary means to accomplish this was by using a fire-tube boiler. The boiler was a tank full of water and perforated with pipes. The gas let off from burning coal or wood traveled through the pipes and heated up the water inside the tank, producing steam. In the early use of steam engines, coal was usually the primary fuel used to heat the water. Fire-tube boilers were susceptible to explosion though, since the entire tank was under pressure.[14]

Today, water-tube boilers, in which water travels through a rack of tubes positioned in the hot gases from fire, are more commonly used.[15]

[edit] References

  1. Steam Engine. Science. 2008-09-30.
  2. Steam Engine History. Science. 2008-09-30.
  3. Steam Engine History. Science. 2008-09-30.
  4. Engine History. 2008-09-30.
  5. Steam Engine History. Science. 2008-09-30.
  6. Steam Engine History. Science. 2008-09-30.
  7. Engine History. 2008-09-30.
  8. Steam Engine History. Science. 2008-09-30.
  9. Steam Engine History. Science. 2008-09-30.
  10. Engine History. 2008-09-30.
  11. Steam Engine History. Science. 2008-09-30.
  12. Inventors. 2008-09-30.
  13. Steam Engine History. Science. 2008-09-30.
  14. Steam. 2008-09-30.
  15. Steam. 2008-09-30.