So I'm planning on building a 100-200 Kp(220-440 lbF) Pulsejet for a project.
It's going to mounted on to an improvised Jr. Dragster frame and be practicing 1/4 mile runs
What design could be scaled up to this size and thrust capability?
I was also wondering what could be done to increase the longevity of the valve's, This will be my first pulsejet project hopefully not the last, so I also need to know any safety precautions to take with this engine.
Big engine, need a reliable design
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daltontechnogeek
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Rocket Man
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Re: Big engine, need a reliable design
I have a good friend that has a Jr. Dragster for his sisters Son. The guy use to race funny cars and real dragsters. If it were me I would put a pulse jet engine on each side of the Jr. Dragster frame. One engine will put all the thrust on the top of one side. I know the Jr. Dragster is suppost to go straight but sometimes it doesn't and having at engine on top could through it out of control much easier. If your not using the piston engine too on the Jr. Dragster and using only the pulse jet engine then it should be much more stable on take off so your probably ok with putting one pulse jet engine on top of the roll cage.
Questions. Do you want the engine to be easy to start? The engine design and size will determine how easy it will start. If the engine will idle at 20% throttle then it will be much easier to start compaired to and engine that will not idle less that 60% throttle.
Jr. Dragsters typically do about 85 mph I don't remember for sure but I think that is 1/8 mile not 1/4 mile. What are you hoping for with a pulse jet engine?
Which engine do you like best?
2 engines 220 lbF one on each side of the frame. Exhaust pipe will be about 8.8" diameter Total engine length about 16 ft long about 18" diameter. This will idle at 20% thrust. If you want it to idle at 60% or 70% thrust the engine length can be a few ft shorter maybe 2 or 3 ft.
1 engine 440 lbF engine will be about double the diameter of the 220 engine and several ft longer.
Questions. Do you want the engine to be easy to start? The engine design and size will determine how easy it will start. If the engine will idle at 20% throttle then it will be much easier to start compaired to and engine that will not idle less that 60% throttle.
Jr. Dragsters typically do about 85 mph I don't remember for sure but I think that is 1/8 mile not 1/4 mile. What are you hoping for with a pulse jet engine?
Which engine do you like best?
2 engines 220 lbF one on each side of the frame. Exhaust pipe will be about 8.8" diameter Total engine length about 16 ft long about 18" diameter. This will idle at 20% thrust. If you want it to idle at 60% or 70% thrust the engine length can be a few ft shorter maybe 2 or 3 ft.
1 engine 440 lbF engine will be about double the diameter of the 220 engine and several ft longer.
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daltontechnogeek
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Re: Big engine, need a reliable design
Well I'd like to have the greatest range for the engine possible and make it easy to start, so idling near 20% would be great, I'd like to build 2 engines, each at 220 lb thrust capability.
We are planning on bending our own frame and modifying the dragster designs to try and hit the big 100 or greater. Technically speaking at the moment with 440 lbs of thrust and the weight of the engine, frame and driver, this could hit ~200 mph I believe in a 1/4 mile, but that's in a perfect environment with no friction and engines operating at 100% capacity, so 100 mph seems to be a bit conservative.
But also the cost for this needs to be as low as possible, and the valves need to last ~ 5-6 hours minimum without needing to be replaced.
Depending on the safety of this thing, it might become unmanned and technically all engine.
We are planning on bending our own frame and modifying the dragster designs to try and hit the big 100 or greater. Technically speaking at the moment with 440 lbs of thrust and the weight of the engine, frame and driver, this could hit ~200 mph I believe in a 1/4 mile, but that's in a perfect environment with no friction and engines operating at 100% capacity, so 100 mph seems to be a bit conservative.
But also the cost for this needs to be as low as possible, and the valves need to last ~ 5-6 hours minimum without needing to be replaced.
Depending on the safety of this thing, it might become unmanned and technically all engine.
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Rocket Man
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Re: Big engine, need a reliable design
Exhaust tube = 8.800" diameter 97" long.
Combustion chamber = 12.5" diameter 24.250" long.
Cone = 33.1" long
Argus valves Air intake Area = 30.5 sq in.
Combustion chamber = 12.5" diameter 24.250" long.
Cone = 33.1" long
Argus valves Air intake Area = 30.5 sq in.
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daltontechnogeek
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Re: Big engine, need a reliable design
okay, So my advisor chickened out, so I scaled the engine down by 5/8 and we're building only one to go on a small cart frame and drive up and down our road
So considering this, how many argus type valves should I use and how do you make argus type valves?
So considering this, how many argus type valves should I use and how do you make argus type valves?
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daltontechnogeek
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Re: Big engine, need a reliable design
So I'm having an exceptionally hard time modeling the argus valves and figuring how many I need
For a engine 5/8 the size of the engine you described what would the intake area be and how would I find the # of valves to use and the size of each valves?
For a engine 5/8 the size of the engine you described what would the intake area be and how would I find the # of valves to use and the size of each valves?
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Rocket Man
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Re: Big engine, need a reliable design
EXAMPLE. Lets assume your argus valve air intake slots are all .375" wide and .187" tall. That means the cross sectional area of that size opening is .070125 sq in.
If you need enough valves to = 30.5 sq. in. then 30.5 divided by .070125 = 434.937 reed valve. Round that off to 435 reed valves.
Lets suppose you put 1 reed valve to cover 2 air intake slots then you only need 217 reed valves to cover 434 slots.
Lets suppose you decided to use 1 reed valve to cover 3 air intake slots then you need 145 reed valves to cover 435 air intake slots.
If you decide to make your reed valves large enough to cover 10 air intake slots then you need 43 reed valves.
Now you need to find an air intake design that will match your engine. This takes a while to get the correct design with the correct air flow for your engine. You need to play with the numbers for a while until you get it right. Look at the video a 20 lb thrust pulse jet engine with 32 argus reed valves. You have a certain area on the front of the engine so you need to try several designs until you find something that works. Do you need 10 rows of air intake slots with 6 slots per row or what? You can adjust the size of the slots to get the cross sectional area you need. Maybe your slots need to be .375"x.200 or maybe .400 x .200. This is mostly trial and error until you find something what will work on your engine design. Large engines are much easier than small engines.
http://www.youtube.com/watch?v=pwz7AvufWG4
If you need enough valves to = 30.5 sq. in. then 30.5 divided by .070125 = 434.937 reed valve. Round that off to 435 reed valves.
Lets suppose you put 1 reed valve to cover 2 air intake slots then you only need 217 reed valves to cover 434 slots.
Lets suppose you decided to use 1 reed valve to cover 3 air intake slots then you need 145 reed valves to cover 435 air intake slots.
If you decide to make your reed valves large enough to cover 10 air intake slots then you need 43 reed valves.
Now you need to find an air intake design that will match your engine. This takes a while to get the correct design with the correct air flow for your engine. You need to play with the numbers for a while until you get it right. Look at the video a 20 lb thrust pulse jet engine with 32 argus reed valves. You have a certain area on the front of the engine so you need to try several designs until you find something that works. Do you need 10 rows of air intake slots with 6 slots per row or what? You can adjust the size of the slots to get the cross sectional area you need. Maybe your slots need to be .375"x.200 or maybe .400 x .200. This is mostly trial and error until you find something what will work on your engine design. Large engines are much easier than small engines.
http://www.youtube.com/watch?v=pwz7AvufWG4