A Short History of Turbine Engines

150 BC - An Egypian philosopher and mathematician, Hero, invented a toy (Aeolipile) that rotated on top of a boiling pot of water. This caused a reaction effect of hot air or steam that moved several nozzles arranged on a wheel. This works when one understands the Third Law of Motion - Every action produces a reaction ... equal in force and opposite in direction.

1232 - Chinese began to use rockets as weapons. The invention of gun powder uses the reaction principle to move rockets foward.

1500 - Leonardo da Vinci drew a sketch of a device, the chimney jack, that rotated due to the effect of hot gases flowing up a chimney. It looked like a device that used hot air to rotate a spit. The hot air came from the fire and rose upward to pass through a series of fanlike blades that turned the roasting spit.

1629 - Giovanni Branca developed a stamping mill, that used jets of steam to rotate a turbine that then, rotated to operate machinery.

1678 - Ferdinand Verbiest built a model carriage that used a steam jet for power.
1687 - Sir Issac Newton announces the three laws of motion. These form the basis for modern propulsion theory.

1. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
2. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors in this law the direction of the force vector is the same as the direction of the acceleration vector.
3. For every action there is an equal and opposite reaction.

1791 - John Barber received the first patent for a basic turbine engine. His design was planned to use as a method of propelling the 'horseless carriage'. The turbine was designed with a chain-driven, reciporcating ype of compressor. It has a compressor, a combustion chamber, and a turbine.

1872 - Dr. F. Stolze designed the first true gas turbine engine. His engine used a multistage turbine section and a flow compressor. This engine never ran under its own power.

1897 - Sir Charles Parson patented a steam turbine was used to power a ship.

1914 - Charles Curtis filed the first application for a gas turbine engine.

1918 - General Electric company started a gas turbine division. Dr. Stanford A. Moss developed the GE turbosupercharger engine during W.W.I. It used hot exhaust gasses from a reciprocating engine to drive a turbine wheel that in turn drove a centrifugal compressor used for supercharging.

1920 - Dr. A. A. Griffith developed a theory of turbine design based on gas flow past airfoils rather than through passages.

1930 - Sir Frank Whittle in England patented a design for a gas turbine for jet propoulsion. The first successful use of this engine was in April, 1937. His early work on the theory of gas propulsion was based on the contributions of most of the earlier pioneers of this field.

The specifications of the first jet engine were:

* Airflow = 25 pounds/sec
* Fuel Consumption = 200/gal/h or 1300 lb/h
* Thrust = 1000 lb
* Specific Fule consumption = 1300/1000 = 1.3 lb/lb/h

1936 - At the same time as Frank Whittle was working in Great Britain, Hans von Ohian and Max Hahn, students in Germany developed and patented their own engine design.

1939 (August) - The aircraft company Ernst Heinkel Aircraft flew the first flight of a gas turbine jet, the HE178.

1941 - Sir Frank Whittle designed the first successful turbojet airplane, the Gloster Meteor, flown over Great Britain. Whittle improved his jet engine during the war, and in 1942 he shipped an engine prototype to General Electric in the United States. America's first jet plane was built the following year.

1942 - Dr. Franz Anslem developed the axial-flow turbojet, Junkers Jumo 004, used in the Messerschmitt Me 262, the world's first operational jet fighter.

After W.W.II the development of jet engines was directed by a number of commercial companies. Jet engines soon became the most popular method of powering the airplanes.

Without the modern jet engine planes would still be plugging along under the speed of sound. I don't know the exact speed the fastest prop plane ever went but it was somewhere around 500 and 550 mph. Some say that the Russian Bear, the TU144, is the fastest prop plane ever built since it was said to average 540 mph on one of its long distance trips and has a top speed of 570 mph with extreme acceleration. But all is not what it seems, this plane is prop powered but the engines are turbo props. Still this plane is quite an accomplishment.

Types of Jet Engines

Turbojets

The basic idea of the turbojet engine is simple. Air taken in from an opening in the front of the engine is compressed to 3 to 12 times its original pressure in a centrifugal or axial compressor. Fuel is added to the air and burned in a combustion chamber to raise the temperature of the fluid mixture to about 1,100°F to 1,300° F. The resulting hot air is passed through a turbine, which drives the compressor. If the turbine and compressor are efficient, the pressure at the turbine discharge will be nearly twice the atmospheric pressure, and this excess pressure is sent to the nozzle to produce a high-velocity stream of gas which produces a thrust. Substantial increases in thrust can be obtained by employing an afterburner. It is a second combustion chamber positioned after the turbine and before the nozzle.The afterburner increases the temperature of the gas ahead of the nozzle. The result of this increase in temperature is an increase of about 40 percent in thrust at takeoff and a much larger percentage at high speeds once the plane is in the air.

The turbojet engine is called a reaction engine. In a reaction engine, expanding gases push hard against the front of the engine. The turbojet sucks in air and compresses or squeezes it. The gases flow through the turbine and make it spin. These gases bounce back and shoot our of the rear of the exhaust, pushing the plane forward.

Picture of Turbojet Engine

Turboprops

A turboprop engine is a jet engine attached to a propeller. The turbine at the back is turned by the hot gases, and this turns a shaft that drives the propeller. Some small airliners and transport aircraft are powered by turboprops.

Like the turbojet, the turboprop engine consists of a compressor, combustion chamber, and turbine, the air and gas pressure is used to run the turbine, which then creates power to drive the compressor. Compared with a turbojet engine, the turboprop has better propulsion efficiency at flight speeds below about 500 miles per hour. Modern turboprop engines are equipped with propellers that have a smaller diameter but a larger number of blades for efficient operation at much higher flight speeds. To accommodate the higher rotative and flight speeds, the blades are scimitar-shaped with swept-back leading edges at the blade tips. Engines featuring such propellers are called propfans.

Picture of Turboprop Engine

Turbofans

A turbofan engine has a large fan at the front, which sucks in air. Most of the air flows around the outside of the engine, making it quieter and giving more thrust at low speeds. Most of today's airliners are powered by turbofans. In a turbojet all the air entering the intake passes through the gas generator, which is composed of the compressor, combustion chamber, and turbine. In a turbofan engine only a portion of the incoming air goes into the combustion chamber. The remainder passes through a fan, or low-pressure compressor, and is ejected directly as a "cold" jet or mixed with the gas-generator exhaust to produce a "hot" jet. The objective of this sort of bypass system is to increase thrust without increasing fuel consumption. It achieves this by increasing the total air-mass flow and reducing the velocity within the same total energy supply.

Turboshafts

This is another form of gas-turbine engine that operates much like a turboprop system. It does not drive a propeller. Instead, it provides power for a helicopter rotor. The turboshaft engine is designed so that the speed of the helicopter rotor is independent of the rotating speed of the gas generator. This permits the rotor speed to be kept constant even when the speed of the generator is varied to modulate the amount of power produced.

Ramjets

The most simple jet engine has no moving parts. The speed of the jet "rams" or forces air into the engine. It is essentially a turbojet in which rotating machinery has been omitted. Its application is restricted by the fact that its compression ratio depends wholly on forward speed. The ramjet develops no static thrust and very little thrust in general below the speed of sound. As a consequence, a ramjet vehicle requires some form of assisted takeoff, such as another aircraft. It has been used primarily in guided-missile systems. Space vehicles use this type of jet.

Picture of Ramjet Engine

The ram jet engine was used by the Germans in World War II to power their V1 or Buzz Bomb rockets.