Turbojet, Scramjet, Ramjet, and Cryogenic - Concept Explained

Summary

Today's session explores the differences between various engines like turbojet, scramjet, ramjet, and cryogenic, which are often in the news. The presenter uses the examples of a burning candle and a balloon to explain the principles of combustion and thrust. The engines are categorized based on whether they carry oxygen or extract it from the air. Turbojet engines use turbines for air compression, while ramjet and scramjet engines rely on shock waves for compression without turbines. Scramjets function with supersonic air intake. Cryogenic engines are used for space travel as they carry liquefied oxygen or fuel, unlike air-breathing engines that can't operate in the vacuum of space.

Takeaways

• 🔥 Combustion requires two basic elements: fuel and oxygen.
• 🌬️ Air breathing engines like turbojet, ramjet, and scramjet take oxygen from the atmosphere, whereas cryogenic engines carry oxygen with them.
• 🚀 Turbojet engines use turbines to compress incoming air for combustion, adding weight to the aircraft or missile.
• 💨 Ramjet engines compress air using shock waves without the need for heavy turbines, improving efficiency.
• 💥 Scramjet engines operate with supersonic incoming air, making them a type of ramjet designed for high-speed flight.
• 🎈 The principle of thrust and propulsion, demonstrated by a balloon, is fundamental to the operation of aircraft, missiles, and satellites.
• 🌐 Air breathing engines are more efficient as they do not carry the extra weight of oxygen containers.
• 🔧 The choice of engine type depends on the speed and altitude requirements of the aircraft or missile.
• 🌌 Cryogenic engines are necessary for space travel where atmospheric oxygen is not available.
• 🛫 At launch, when air movement is minimal, air breathing engines cannot be used, requiring the use of engines with carried oxygen for liftoff.

Q & A

What are the two basic requirements for combustion as illustrated by the candle example?

The two basic requirements for combustion, as shown by the candle example, are fuel and oxygen. The wax serves as the fuel, and the oxygen from the atmosphere acts as the oxidizer.

Why does a candle go out when placed in a closed container?

A candle goes out in a closed container due to the depletion of oxygen. Once the oxygen is used up, the combustion process cannot continue, causing the candle to extinguish.

How does the principle of thrust demonstrated by the balloon relate to aircraft propulsion?

The principle of thrust demonstrated by the balloon is related to aircraft propulsion because when air is expelled from the balloon in one direction, it creates a force that propels the balloon in the opposite direction. Similarly, aircraft engines generate thrust by expelling gases at high speeds, propelling the aircraft forward.

What are the two methods of obtaining oxygen for combustion in engines as described in the script?

The two methods of obtaining oxygen for combustion in engines are carrying an oxygen container with the flight, which increases the weight and affects efficiency, or extracting oxygen directly from the air, which is used in air-breathing engines like turbojet, ramjet, and scramjet.

Why are turbojet engines more efficient than engines that carry oxygen containers?

Turbojet engines are more efficient because they do not need to carry an oxygen container, which reduces the overall weight of the aircraft. This weight reduction can enhance the efficiency of the flight compared to engines that carry oxygen containers.

What is the function of turbines in turbojet engines?

In turbojet engines, turbines are used to compress the incoming air, which is necessary for the combustion process. The compressed air mixes with the fuel to facilitate combustion, which then generates thrust.

How do ramjet and scramjet engines differ from turbojet engines in terms of air compression?

Ramjet and scramjet engines differ from turbojet engines in that they do not use turbines for air compression. Instead, they utilize shock waves and other technologies to compress the air. This can increase efficiency as it eliminates the weight of the turbines.

What is the minimum speed requirement for the incoming air in a scramjet engine?

The incoming air in a scramjet engine must be at supersonic speeds, which is more than one Mach (greater than the speed of sound), to function effectively.

Why can't air-breathing engines like turbojet, ramjet, and scramjet be used at the beginning of a satellite launch?

Air-breathing engines cannot be used at the beginning of a satellite launch because they require fast-moving air to function, and at launch, there is no movement of air to provide the necessary airflow for combustion.

What type of engines are used for satellite launches when air-breathing engines are not suitable?

For satellite launches, when air-breathing engines are not suitable, cryogenic engines are used. These engines carry liquefied oxygen or fuel, allowing them to function in the vacuum of space where there is no atmospheric oxygen.

Why are cryogenic engines necessary for space travel beyond 100 kilometers above the atmosphere?

Cryogenic engines are necessary for space travel beyond 100 kilometers because, at such altitudes, there is no atmospheric oxygen available for combustion. Cryogenic engines carry their own oxidizer and fuel in liquefied form, enabling them to operate in the absence of atmospheric oxygen.