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Gasoline Engine

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Mechanical Features and Designs

See also: Internal Combustion Engine

A gasoline engine is a type of internal combustion engine that burns gasoline for fuel. It uses a spark ignition system to generate an electrical charge with spark plugs that ignites the fuel and air inside a cylinder resulting in fuel combustion. The fuel is then heated and expands inside the cylinder, generating mechanical energy. Almost all vehicles on the road today run on a gasoline engine. A gasoline engine is also referred to as a petrol engine as petrol is another, primarily British term for gasoline.

In a gasoline engine, the fuel and air are premixed before compression occurs. This is how gasoline engines differ from diesel engines, another type of internal combustion engine, in which the air is first compressed and then the fuel added at the end of compression stroke.

All gasoline engines like diesel engines work based upon what is known as the four-stroke cycle approach, involving the intake of fuel and air, the compression of air and fuel, the generation of power through combustion, and finally, the expulsion of burned gas through an exhaust pipe.[1] Other types of gasoline engines include two-stroke engines and rotary engines.


[edit] History

The first type of engine used to power anything was the steam engine. Steam engines were heavy and cumbersome and not well suited for many types of applications, particularly vehicles. This led to the development of a type of internal combustion engine in the mid-1800s. Many crude attempts were made to fabricate an internal combustion engine that was fueled by city gas, illuminating gas, or producer gas.[2] These early engines were not ideal but they proved to be more usable than steam engines.

[edit] Nicolaus Otto

There were three significant historical developments that shaped the modern gasoline engine. The first contribution, made by Nikolaus Otto in 1876, was a workable piston four-stroke internal combustion gasoline engine called the “Otto cycle engine” which he later adapted for use in a motorcycle. His four-stroke gasoline engine would become the model for which all future liquid-based automobile engines would be based on.[3]

[edit] Karl Benz

The evolution of the gasoline engine is synonymous with that of the modern automobile. In 1885, Karl Benz, a German mechanical engineer, invented the first automobile powered by an internal combustion engine, integrating the concept of chassis or undercarriage with an internal combustion engine. In 1886, he received a patent for his gas-fueled automobile that began as a simple, three-wheeled carriage type vehicle and later evolved into a four-wheeled car by 1891. The invention of his gasoline operated vehicle propelled Benz to become one the world’s largest car manufacturers by 1900.[4]

[edit] Gottlieb Daimler

In 1885, Gottlieb Daimler devised what is today regarded as the prototype of the modern gas engine.[5] Daimler simply expounded upon Otto’s internal combustion engine design. In fact, Daimler had worked, as a technical director for a company Otto was a co-owner of in 1872.

His first engine was small, lightweight, and fast, featuring a gasoline-injected carburetor and a vertical cylinder. In 1886, Daimler modified a stagecoach to contain his engine thereby actually designing the world’s first four-wheeled operational vehicle. He has also been credited with producing the world’s first practical internal combustion engine.[6]

Daimler made another significant contribution in 1889 when he invented a v-slanted, four-stroke gas engine with mushroom shaped valves. The unique design of this engine set the precedence for all car engines moving forward. He also built and manufactured his first automobile from the ground up in the same year.[7]

[edit] Features/How it Works/Types

Gasoline engines can be grouped according to application, method of fuel management, ignition, piston or cylinder arrangement, rotor arrangement, strokes per combustion cycle (two or four), cooling system, and valve type and location. Gasoline engines typically fall into one of two types, a piston-and-cylinder engine or a rotary engine.

Piston-and-cylinder engines rely on pressure created from combustion to force a piston to move the cylinder in to a back-and-forth or reciprocating motion. In fact, piston-and-cylinder engines are also referred to as reciprocating engines as a result of the motion generated by the piston against the cylinder. The piston is driven away from the cylinder’s head and mechanical energy is produced.[8] In a rotary engine, also known as a Wankel engine, the pressure from gas is applied to rotor surfaces that propel the rotor into motion and produce mechanical energy.[9]

[edit] Piston-and-cylinder Four-stroke Engine

Most vehicles on the road today are built with piston-and-cylinder four-stroke gasoline engines. Nikolas Otto, as mentioned above, first developed the piston-and-cylinder four-stroke engine in 1876. In the four-stroke cycle, an ignitable mixture of gas and air are drawn through an intake valve inside the cylinder. This is known as the intake stroke. This mixture is then compressed as the piston inside the cylinder is driven upwards near the end of a second stroke, the compression stroke, with the intake valves being closed off. At the end of the compression stroke, a charge is ignited by an electric spark generated from spark plugs. What follows is a third stroke, known as a power stroke. Both intake valves remain closed and as a result of ignition, the gas and air mixture inside the cylinder burn off and expand, applying pressure on the piston in a downward movement. As the piston ascends in a fourth and final stroke, it opens an exhaust valve where the gas byproducts from combustion are released through. This entire cycle is repeated again and again and is contingent on four-strokes of the piston and two revolutions of the crankshaft.[10]

[edit] Piston-and-cylinder Two-stroke Engine

Sir Dougald Clerk first developed the two-stroke piston-and-cylinder engine in 1878.[11] Since then, the engine’s design has essentially stayed the same as the original, though some simplifications to its mechanics have been made. In Clerk’s design, both the compression and power stroke of the four-stroke cycle were implemented into the intake and exhaust strokes, resulting in only one revolution of the crankshaft. The two-stroke engine therefore accomplishes in two piston strokes what the four-stroke engine does in four.[12] This produces is a relatively high-powered engine that is used to operate everything from portable, lightweight equipment and devices such as lawnmowers and motorcycles to larger applications like locomotives. One of the disadvantages of this type of gas engine is that it tends not to be as fuel efficient as a four-stroke gas engine. 

[edit] Uniflow-scavenged Two-stroke Engine

Another type of two-stroke gas engine is the uniflow-scavenged engine. Scavenging refers to a process where air at a pressure greater than that of atmospheric pressure pushes the exhaust out of the cylinder. A two-stroke engine that has an exhaust valve mounted in the cylinder head instead of using the piston to drive the exhaust out the cylinder is known as a uniflow-scavenged engine.[13]

[edit] Rotary (Wankel) engine

The Wankel engine, conceived by German engineer Felix Wankel, is radically different in design and mechanics than the conventional piston-and-cylinder four-stroke gasoline engine. The engine can be described as an equilateral triangular orbiting rotor.[14]

In a rotary motor, the pressure of combustion is held in a chamber formed by part of the housing and sealed in by one face of the rotor that is used instead of pistons. The rotor travels along a spirographic path that keeps the three parts of the triangular rotor in direct contact with the housing, generating three separate volumes of gas. As the rotor moves around inside the chamber, each of these three volumes of gas expands and contracts, drawing air and fuel into the engine, compressing it, and then generating enough power to cause the gas to expand before it is expelled as exhaust.[15]

[edit] Hydrogen-boosted Gasoline Engine

Hydrogen-boosted gasoline engines are a new technology still in development, one that might very well bridge the gap between conventional gas engines and the development of fuel cells powered vehicles in the future.

Fuel cells are a viable alternative for powering vehicles but are very expensive and still years away from mass production. With fuel costs escalating, hydrogen-boosted gasoline engines offer many clear advantages; namely fuel economy, lower emissions, and greater cost-efficiency in terms of production.[16]

With a hydrogen-boosted gasoline engine, a small amount of hydrogen is produced with an on-board reformer and then added to the initial intake of gas and air mixture drawn in to the engine. This provides nearly twice the amount of air for a given amount of fuel taken into the combustion chamber. This process is much more energy efficient because the pumping of the engine is minimized with the intake of hydrogen. In fact, the combination of hydrogen and gasoline can net fuel-economy gains as much as 20 to 30 percent.[17] The use of hydrogen also eliminates a need for external mono-nitrogen oxides emissions control. The hydrogen-boost is also easily integrated with a conventional gasoline engine as a bolt-on technology. Prototypes are currently being installed and tested on sports utility vehicles (SUVs) with the technology to be marketed and produced by 2010.[18]

[edit] Common Manufacturers

[edit] References

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  3. Inventors. 2008-09-09.
  4. Inventors. 2008-09-09.
  5. Inventors. 2008-09-09.
  6. Inventors. 2008-09-09.
  7. Inventors. 2008-09-09.
  8. Inventors. 2008-09-09.
  9. Gasoline Engine. Britannica. 2008-09-09.
  10. Gasoline Engine. Britannica. 2008-09-09.
  11. Evolution of Internal Combustion Engine. Infoplease. 2008-09-09.
  12. Encyclopedia Gasoline Engine. Britannica. 2008-09-09.
  13. The Basics. Marine Diesels. 2008-09-09.
  14. Gasoline Engines. Britannica. 2008-09-09.
  15. Engine. 2008-09-09.
  16. How a Hydrogen Boosted Gasoline Engine Works. 2008-09-09.
  17. How a Hydrogen Boosted Gasoline Engine Works. 2008-09-09.
  18. How a Hydrogen Boosted Gasoline Engine Works. 2008-09-09.