Pulse jets and ram jets as part of my course on jet propulsion

In summary, both types of engines use air to provide thrust. The difference between a pulse jet and a ramjet is that a pulse jet uses a valve box to prevent the exhaust from going that way, which opens for intake and closes for combustion. A ramjet carries out continuous combustion, but it needs to be moving at a very high speed to work.
  • #1
banerjeerupak
123
1
i was reading about pulse jets and ram jets as part of my course on jet propulsion. all i was told was that they are aero-thermo-dynamic-ducts.

couldn't understand what they mean. checked google, but the articles i got were vague.

could someone explain what aero-thermo-dynamic-ducts are?
 
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  • #2
I've never heard that term. Going by the words involved, it should simply mean that it's a tube of some sort in which work is extracted from hot air.
 
  • #3
then could you tell me if that is the way in which pulse jets and ram jets work?
 
  • #4
I'm not the expert here; Fred Garvin, Russ Watters, Rainman Aero, Astronuc, and a few others know far more than I could ever learn. I'm sure that one or more of them will weigh in before long.
That having been said, the basic answer is 'yes'.
Both types of engines ingest air without the aid of a compressor system, mix it with fuel, burn the mix, and expel the exhaust to provide thrust. The difference is that a pulse jet uses a valve box at the front, or a carefully tuned tube, to prevent the exhaust from going that way, which opens for intake and closes for combustion. That cyclic open/close/boom is why it pulses. A ramjet carries out continuous combustion, but it has to be moving at something on the order of 400mph to work.
By the way, if you're taking a course on this, shouldn't they be teaching you how they work?
 
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  • #5
I've never heard the term either, but what it implies to me is that both aerodynamic and thermodynamic principles are at work. Sounds reasonable, but yes, vague...
 
  • #6
I am assuming, by the description, that the original term was meant to mean that in both ramjets and pulse jets, there are no rotating components. Hence the "ducts" reference because they are really just tubes doing the work.

Aerothermodynamics is the general area of study for the components and systems in turbomachinery (usually high speeds).

According to this web site, aerothermodynamic duct was coined by the Brits for a ram jet.

http://www.onera.fr/conferences-en/ramjet-scramjet-pde/
 
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Related to Pulse jets and ram jets as part of my course on jet propulsion

1. What is the difference between a pulse jet and a ram jet?

A pulse jet is a type of jet engine that operates by periodically pulsating its combustion chamber to create thrust. On the other hand, a ram jet is a type of jet engine that relies on forward motion to compress incoming air and create thrust. The main difference between the two is that a pulse jet operates with a series of intermittent explosions, while a ram jet operates continuously.

2. How do pulse jets and ram jets work?

In a pulse jet, air is drawn into the combustion chamber through an intake valve. The valve then closes and the air is compressed by the rapid combustion of fuel. This creates a high-pressure pulse that exits the engine through a nozzle, producing thrust. In a ram jet, the forward motion of the aircraft compresses air in the intake, which is then mixed with fuel and ignited in the combustion chamber to produce thrust.

3. What are the advantages and disadvantages of using pulse jets and ram jets?

One advantage of pulse jets is their simplicity and low cost, making them suitable for use in small-scale applications such as model airplanes. However, they have a limited operating range and are not as efficient as other jet engines. Ram jets, on the other hand, have a higher operating range and are more efficient, but require high speeds to function effectively. They are also more complex and expensive to manufacture.

4. How are pulse jets and ram jets used in jet propulsion?

Pulse jets are commonly used in small-scale applications, such as model airplanes and missiles. They are also used in pulse detonation engines, which can provide a higher thrust-to-weight ratio and are used in military applications. Ram jets are used in supersonic and hypersonic flight, where they can operate efficiently at high speeds. They are also used in scramjet engines, which are being developed for future space vehicles.

5. What are some real-world examples of pulse jets and ram jets?

One famous example of a pulse jet is the V-1 flying bomb used by Nazi Germany in World War II. It was also used in the infamous "Buzz Bomb" attacks on London. Ram jets have been used in various missiles, including the BrahMos supersonic cruise missile developed by India and Russia. They are also used in the propulsion systems of some supersonic and hypersonic aircraft, such as the Lockheed Martin SR-71 Blackbird.

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