Pulse Jet engine - A new design concept

[telepresence]

The front valve is a ram--so needs additional thought. The shaft should be larger diameter and hollow for air cooling.

Shouldn't be to much worse than a petal valve, and doesn't have to bend, but thickness would need to be a consideration to balance weight and durability. Air cooling sounds interesting... Would help with the weight factor, too, I guess.

 

[telepresence]

There we go, that's basically what I was going to describe, but I was going to try and explain the 'why' as well - hence waiting for tomorrow.

I'll be looking forward to that.

 

[telepresence]

It may need a retention spring somewhere.

There we go, that's basically what I was going to describe...

Just a guess, but is this basically what you are referring to?

The question is, will a sufficiently strong vacuum be able to form before the valves switch to intake position...

 

[telepresence]

However I am unclear abt the working.

basically something like this:

 

[Phrak]

Very cool. What might happen with an 'S' shaped orifice?

 

[aryanscarlet]

Got it guys! Sorry, mistook the ball mechanism! Now its clear. Glad people have pitched in ideas. Will keep posted on my work too.

 

[aryanscarlet]

I made a small change to telepresence's idea. In this valving, the flow right after after combustion is straight thru the valve instead of a sudden reduction in area which causes fluid dynamic losses. Also with the smaller valve, when closed, due to smaller area of cross section of the ball, the pressure on the valve and also the hoops stress on the walls of the combustion chamber will be greater. Also when the valve is closed and combustion takes place, the convergent section will also be a part of the chamber and the hoops stress would be pronounced on the walls and the sharp area changes will produce turbulence during combustion and problems in flame stabilization.

The inlet could also be of the size of the second valve or even a normal v- shutter inlet would do.

Any contradictions or improvements guys?

 

[telepresence]

it seems like that would reduce the power of the engine if you use the valve as part of the combustion chamber. I was seeing the combustion happening while both valves were closed to boost the pressure and ensure that the fuel burns while still inside the engine and not after it leaves. I could be wrong, though.
Also, remember that these valves are constantly spinning. the snapshot you have in that image would only be the case for an instant, certainly not long enough for the entire combustion and exhaust processes to take place.

 

[JaredJames]

it seems like that would reduce the power of the engine if you use the valve as part of the combustion chamber. I was seeing the combustion happening while both valves were closed to boost the pressure and ensure that the fuel burns while still inside the engine and not after it leaves. I could be wrong, though.

aryanscarlet's single valve design is along the lines of what I was thinking of. The dual ball valve system is just over complicating things and I don't see any real gain to be had by doing it. Not to mention increasing the chance of backfire / complete detonation.

Also, remember that these valves are constantly spinning. the snapshot you have in that image would only be the case for an instant, certainly not long enough for the entire combustion and exhaust processes to take place.

The 'snapshot' would be the midpoint of combustion - hopefully the point when the exhaust is being expelled to greatest advantage.

It wouldn't have to be there for the whole process, just enough to gain an advantage.

 

[aryanscarlet]

No you guys have misunderstood me. I did not mean that the combustion will happen with one valve open. That is totally against the entire idea itself. I meant, when the valve is fully open, it must be coincident with the combustion chamber and not like telepresence's first diag. The combustion will happen when both valves are closed only. In the initial idea, the nozzle section that led to the ball valve would cause flame instabilities which can be avoided in the changed diag. Also the opening and closing is up to us to decide based on preliminary tests and optimization can be done. The valve can be left closed for a prolonged time also or reduced time also based on the size, thrust req etc. This can be done by a simple cam.

 

[telepresence]

Also when the valve is closed and combustion takes place...

Okay, my bad. Missed that little "and" connection there.

 

[telepresence]

There we go, that's basically what I was going to describe, but I was going to try and explain the 'why' as well - hence waiting for tomorrow.

I really would like to hear this.

 

[JaredJames]

I really would like to hear this.

Sorry, really busy.

During combustion, there is a force applied to the front "sail". This forces it closed, ensuring all exhaust is directed backwards.

Your biggest problem is that you are assuming the thrust acting on the "pyramid" section + suction created will be enough to force the "sail" to open. Remember, there will be air drawn in through the rear during this time which will act against the rear "pyramid" creating a force that will try to counteract the suction acting on the "sail". The net effect is likely to be that the front "sail" section will remain at least partially, if not fully closed. Efficiency will be lost.

RE Bolded: the force acting on the forward "sail" will be far in excess of the force on the rear "pyramid" so it will easily counteract any effects.

So you need a spring to force the rear "pyramid" valve closed and the forward "sail" valve open. That way, the combustion will act against the forward "sail" to close it and direct all exhaust out of the back. Once complete the spring will force the valve to switch and suction to occur from the front.

 

[telepresence]

Sorry, really busy.

Aren't we all...

Thanks for your response. I do see the need for a spring there.