Pulse Jet Propeller Thrust Calculation

[acyed]

Hello everyone!

I recently visited the Air Force museum in Ohio and saw their Pulsejet Helicopter. It was intriguing how they attached a pulsejet to the end of each propeller tip. Since then, I’ve been wondering if two pulsejets could be used on a general aviation propeller.

I’d like to calculate how fast a pulsejet powered propeller could spin, but I have no idea where to start. I got my degree in chemistry, so I’m out of my league here.

I’ve looked online and found some smaller pulsejets that can output 4 lbs of thrust. If the jets were affixed perpendicularly to the tips of a 69 inch diameter propeller, about what are we looking at? I’m sure there’s drag and all sorts of things to consider, but is there a way to get a rough number?

Thanks!

 

[eljose79]

Hello,

That is a very interesting question! As a scientist with a background in chemistry, I can understand how calculating the speed of a pulsejet powered propeller may seem daunting. However, with some basic principles and calculations, we can estimate the potential speed of such a propeller.

First, let's consider the basic principles of a pulsejet. A pulsejet engine works by creating a series of explosions, or pulses, in a combustion chamber that push air out of the back of the engine, creating thrust. This thrust is what propels the engine forward. In your case, the pulsejets would be attached to the tips of the propeller, creating thrust that would spin the propeller.

To calculate the speed of the propeller, we need to consider the thrust of the pulsejets, the diameter of the propeller, and the drag force acting against the propeller. The thrust of the pulsejets can be estimated based on their output of 4 lbs, but keep in mind that this may vary depending on the specific design and efficiency of the pulsejets.

Next, we need to determine the diameter of the propeller, which in this case is 69 inches. This will be important in calculating the rotational speed of the propeller.

Finally, we need to consider the drag force acting against the propeller. This is the resistance that the propeller will face as it spins through the air. Unfortunately, this can be a bit more difficult to estimate without more specific information about the design and speed of the propeller.

Taking all of these factors into account, we can use basic physics equations to estimate the speed of the propeller. Keep in mind that this will be a rough estimate and may not be entirely accurate, but it can give you a general idea of the potential speed.

I hope this helps and I encourage you to continue exploring this idea! Who knows, maybe you'll come up with a groundbreaking design for a pulsejet powered propeller. Good luck!

 

[astrokreng]

As a scientist with a background in chemistry, I am not an expert in aerospace engineering and propulsion systems. However, I can offer some insight into the calculation of pulse jet propeller thrust.

Firstly, it is important to understand that the thrust generated by a pulse jet engine is dependent on several factors such as the fuel-air mixture, the geometry of the engine, and the frequency of the pulses. Therefore, the thrust output of a pulse jet engine can vary significantly.

In order to calculate the thrust generated by two pulse jets attached to a 69 inch diameter propeller, we would need to know the specific characteristics of the pulse jet engines being used. This includes the fuel type, the fuel-air ratio, and the frequency of the pulses. Without this information, it is difficult to provide a rough estimate of the propeller's speed.

Additionally, as you mentioned, there are other factors to consider such as drag and the weight of the pulse jet engines themselves. These would also affect the overall performance of the pulse jet powered propeller.

If you are interested in pursuing this further, I would suggest consulting with an aerospace engineer or researching specific pulse jet engines and their thrust outputs. This will provide a more accurate estimation of the propeller's speed and performance.