ramjet


Also found in: Dictionary, Thesaurus, Wikipedia.
Related to ramjet: ramjet engine, scramjet

ramjet:

see jet propulsionjet propulsion,
propulsion of a body by a force developed in reaction to the ejection of a high-speed jet of gas. Jet Propulsion Engines

The four basic parts of a jet engine are the compressor, turbine, combustion chamber, and propelling nozzles.
..... Click the link for more information.
.

Ramjet

A member of a class of high-speed air-breathing propulsion systems. These include subsonic combustion ramjets (RAM), supersonic combustion ramjets (SCRAM), dual-mode ram-scramjets (RAM-SCRAM), dual-combustor ramjets (DCR or DCRJ), and air-ducted rockets (ADR). In each case, air collected from the atmosphere is ducted into the engine to serve as the oxidizer for the burning of fuel that is stored on board. All the engines operate on a modified form of the basic Joule or Brayton cycle; that is, the air is compressed in the inlet, burned at near-constant pressure, and accelerated in an expansion nozzle. In accordance with Newton's second law, thrust is produced by the increase in momentum as the gas passes from the inlet to the nozzle exit. Compression is produced by one or a multiplicity of compression waves generated on the inlet surfaces. The level of pressure that can be reached in these waves is insufficient to produce net thrust unless the air speed is greater than about Mach 0.9 (that is, the velocity is 0.9 times the local speed of sound). Thus the ramjet must be launched from a high-speed aircraft or brought up to speed by a booster rocket or another adjunct engine. The latter type are known as combined-cycle engines. A classic example is the combination of a turbojet and a ramjet, which is called a turboramjet. See Brayton cycle, Rocket propulsion, Turbojet, Turboramjet

A subsonic combustion ramjet may be boosted to its operating speed by a solid-fueled rocket (see illustration). After the booster separates, the air entering the inlet is compressed through oblique shocks and a terminal normal shock. The flow aft of the normal shock and in the combustor is subsonic, but the velocity is high and flameholders are needed to anchor the flame and thereby produce high combustion efficiency. Passing from the combustor, the exhaust gases are reaccelerated in a converging-diverging nozzle to supersonic speed at the engine exit. See Nozzle

There are several characteristics that lead to the choice of one of the ramjet cycles for a variety of missions. Foremost are the engine performance as measured by specific impulse, light weight, and low cost. For applications up to about Mach 3, the turbojet has the highest specific impulse among hydrocarbon-fueled engines, which leads to its choice as the power plant for subsonic and supersonic aircraft. Most missile applications demand higher thrust which requires afterburning. For flight speeds between Mach 3 and 5, the subsonic combustion ramjet is optimal, and above Mach 5 the choice is among the supersonic combustion ramjet, the dual-mode ram-scramjet, and the dual-combustor ramjet. The solid rocket has much lower engine performance and is used only when high specific impulse is not the governing factor. Rocket-powered vehicles are used for relatively short-range missions or for near-to-vertical flight.

ramjet

A simple duct or tube of a special shape that collects the air caused by forward speed, or the ram effect; compresses it; makes it flow over some heat source; and then ejects the air at a higher speed than the entry speed. In this arrangement, there is no moving part and the system can work only at a forward speed. Originally called an aerothermodynamic duct

ramjet

, ramjet engine
a. a type of jet engine in which fuel is burned in a duct using air compressed by the forward speed of the aircraft
b. an aircraft powered by such an engine
References in periodicals archive ?
RAMJET is available on-line in paperback through Amazon and Barnes and Noble and at www.
High speed, air-breathing engines are known as ramjets or scramjets because they ram oxygen into the front of the engines.
The supersonic Coyote target vehicle is based on a solid fuel ramjet propulsion system that is integrated into a compact missile airframe.
Lockheed Martin along with Aerojet Rocketdyne are said to be jointly developing the plane and would require creating a new type of hybrid engine to reach mach six, one that uses a turbine when it is not going too fast, and a supersonic combustion ramjet when it is ready to move.
The two-stage missile, the first one being solid and the second ramjet liquid propellant, has already been inducted into the country's Army and Navy.
The internal operations or ramjet and scramjet engines are also analyzed.
Like former principal procurator fiscal Stuart MacFarlane - Roger Ramjet to his pals - who feels a shred of pity for his predicament?
Nasianceno is also responsible for developing sales for the NexGen baler line and the Marathon Ramjet compactor line in Mexico, Central America, the Caribbean and South America.
The goal of the $230 million program is to advance technologies for a scramjet - or supersonic combustion ramjet - engine, an ultra-high-speed engine that draws oxygen for combustion from the atmosphere rather than carrying it as a rocket ship does.
Nasa built the X-43A under a $250 million (pounds 140 million) programme to develop and test an exotic type of engine called a supersonic-combustion ramjet, or scramjet.
The supersonic combustion ramjet engine was launched from a site in the Australian outback by HyShot project members.