Means to Create A Jet

P M V SubbaraoProfessor

Mechanical Engineering Department

Viable ways of Creating Strong and Reliable Muscles for the Aircraft……

Jet Characteristics

• Quantities defining a jet are:

– cross-sectional area;

– composition;

– velocity.

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Of these, only the velocity is a truly characteristic feature and is of considerable quantitative significance.

Jet Characteristics of Practical Propulsion Systems

System Jet Velocity (m/s)

Turbofan 200 - 600

Turbojet (sea-level, static) 350 - 600

Turbojet (Mach 2 at 36000 ft) 900 - 1200

Ramjet (Mach 2 at 36000 ft) 900 - 1200

Ramjet (Mach 4 at 36000 ft) 1800 - 2400

Solid Rocket 1500 – 2600

Liquid Rocket 2000 – 3500

Nozzle : Steady State Steady Flow

First Law :

No heat transfer and no work transfer & No Change in potential energy.

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Combined analysis of conservation of mass and first law

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A SSSF of gas through variable area duct can interchange the enthalpy and kinetic energy as per above equation.

Consider gas as an ideal and calorically perfect.

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Isentropic expansion of an ideal and calorically perfect gas.

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How to Create A Jet?

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How and What to do?

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At Design Conditions:

Engines to Create a Jet ???

UFO Logistics

• Is It Really Possible That The Ancient Indians Had The Capacity To Deploy Devastating Nuclear Weapons Against Their Enemies?

• Moreover, Is It Really Possible, As Many Ufologists Claim, That Awesomely Powerful Nuclear Weapons Were Actually Given To The Ancient Indian Warriors By Extra-tererstrials, Highly Advanced Spacemen From Other Planets?

• Well, Passages From Ancient Indian National Epics Certainly Appear To Be Evidence Of Such Astonishing Claims….

• Http://Www.Ufoevidence.Org/Documents/Doc1937.Htm

“The heavens cried out, the earth bellowed an answer, lightening

flashed forth, fire flamed upwards, it rained down death. The brightness

vanished, the fire was extinguished. Everyone who was struck by the

lightening was turned to ashes”. And again from the same source: “It was a ghastly sight to see. The corpses of the fallen were so mutilated they no longer looked like human beings. Never before have we seen such an

awful weapon, and never before have we heard of such a weapon”.

According To The Evidence

The Ancient Technique : Ramjets

• Only three operating components:– intake (diffuser);– burner (combustion chamber);– nozzle.

Typical Ramjet

Schematic

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Ramjets - Basic Operating Features

• Air decelerated in intake (diffuser) and pressure rises due to ram effect.

• Known as ram pressure and significant at supersonic speeds.

• A ramjet therefore needs neither a compressor nor a turbine, simplifying the design and reducing the cost.

• Greatest disadvantage is that it has to be accelerated up to very high speed before it produces any useful thrust.

• Also complicated supersonic intake required to avoid shock losses - could be nose, side or ventral mounted.

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Ramjets (Front Intake) for GW

• Jet velocity: 900-2400m/s

• Complex intake

• No static thrust (has to be boosted up to speed)

• Mechanically simple, reliable cheap & tolerant of high temperatures.

Sea Dart

Introduction to Rockets

Solid Propellant Rocket - Basic Operating Features

• Four basic components:

– motor case, nozzle, solid propellant charge, igniter.

• Propellant charge comprises combined fuel & oxidizer.

• Gaseous combustion products fill void at high pressure (70 bar typically) and sustains combustion.

• Hot gases vent through convergent-divergent nozzle to provide high-speed (supersonic) propulsion jet.

• Gases generated and escape at fixed rate for steady operation by maintaining constant burning surface area.

Solid Propellant Rocket for GW

• Jet velocity: 1500-2600m/s

• Most widely used in GW

• Short, medium range (< 50 km)

• Simple, reliable, easy storage, high T/W

Rapier

Solid Rocket Features

• High propellant density (volume-limited designs).

• Long-lasting chemical stability.

• Readily available, tried and trusted, proven in service.

• No field servicing equipment & straightforward handling.

• Cheap, reliable, easy firing and simple electrical circuits.

But

• Lower specific impulses (compared with liquid rockets).

• Difficult to vary thrust on demand.

• Smokey exhausts (especially with composite propellants).

• Performance affected by ambient temperature.

Liquid Propellant Rocket - Basic Operating Features

• Fuel and oxidant tanked separately and delivered to combustion chamber at specific rates and pressures.

• Propellant flowrates (and hence thrust) variable upon demand.• Disadvantages compared with solid propellant rockets:

– increased complication;– Storage problems (usually LOX & LH2 which must be

maintained at very low temperatures);– more costly;– reduced reliability.

Liquid Propellant Rocket - Space

• Jet velocity: 2000 - 3500m/s.

• Highest thrust, can be throttled.

• Long sustained flight (5mins+). Ariane 5

Space Transportation System (STS)

Closure • Ramjet Advantages:

• -Low Weight

• -High Thrust to Weight Ratio.

• -No moving parts keep initial and maintenance costs down.

• -Large Thrust to Unit Frontal Area.

• -Provides best specific fuel consumption of all air breathing engines at supersonic speeds. Ramjet

• Disadvantages:

• -Does not work well at off design Mach numbers without a variable geometry diffuser and supersonic spike.

• -By the nature of air compression, does not provide static thrust.

• -Fuel consumption at subsonic speeds is very high compared to other air breathing engines.