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KSP inspired me to design a liquid-fueled rocket engine

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I give a second chance to this engine. I changed oxygen valve servo to better one, should be easier to start the engine.

It was a flame thrower (a good one!) but I didn't design it to that purpose.

Second test run is coming soon. Probably cooling is not sufficient and engine will melt. But before that I try to learn ignition procedure well.

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My feeling is that it might be hard to ignite that before fuel and oxidizer build up in the chamber. Are the injector plate hole(s) drilled at any kind of angle? I'm not sure, I say give it a try and see what happens.

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Today I tried to fire another time RUD-7 engine but gasoline did not flow inside engine. I can't open that becouse all is brazed so farewell RUD-7 "flamethrower".  But I had made another engine so I tested RUD-8. I tried to think how I could minimize cooling volume inside engine so I filled 1 mm cooling gap with 1 mm diameter brass rods. Cooling volume is now much smaller and flow is faster. Engine is heavier, now it weights 210 g. I really can't braze bigger than this with my equipment.

Here are pictures how I made that:

https://imgur.com/a/3LZNOEf

So I fired engine. Look and analyze please.

 

 

Edited by totalitor

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More testing today, confusing results.

Second test run, 15 bar pressure fuel feeding, 10 bar oxygen.

Third test run, 12 bar pressure fuel feeding, 10 bar oxygen. Watch the apple I left on plate.

 

So I tried to increase fuel feed by adding more pressure, result is engine runs longer with same amount of fuel. I don't get it.

But on third test there was good amount of thrust, it worked 1 second as planned.

And cooling works great, after test engine was warm but not too warm.

Now I need some advice. What's wrong with this engine? What I should do different?

I

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Is a wooded area really a good place to be playing with possibly explosive flammables? 

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On 9/5/2018 at 8:46 AM, totalitor said:

What's wrong with this engine? What I should do different?

I have not read through all of this thread and I am not a rocket mechanic but I am a fully qualified automotive master technician. I know, doesn't really seem to apply here but, my first impression of the second and third ignitions is flame front propagation time being off. In a reciprocating piston engine (whether diesel or gasoline or whatever) you can have the right (by math) amount of fuel and air but the flame speed can be too slow and unburnt fuel can end up exiting into the exhaust. In the car world we ramp up fuel pressure (or change the aeration tube if you're a carburetor guy) to ensure full atomization which speeds up the burn(sort of, more like ensures max speed). Many other things affect flame speed like combustion chamber design, dynamic compression, and engine temperature(gas is a 14.7:1 mixture ideally but can be 10:1 on a cold engine). On GDI(gasoline direct injection) and diesel engines the fuel pressure is extremely high for injecting fuel exactly at the heat source(spark plug for gas, much more complex for diesel) just before ignition under nearly max compression. GDI engines run nearly 3000psi fuel pressure and modern diesels run 30,000psi. I would, if possible, use the least amount of fuel and ox I could get away with and the maximum pressure of both that I could in an attempt to burn them where and when I wanted.

Maybe all that has nothing to do with it. It's just a mechanics take on what could be wrong or what could improve performance.

Edited by AngrybobH

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10 hours ago, Vanamonde said:

Is a wooded area really a good place to be playing with possibly explosive flammables? 

No it is not. But I do test only when it is calm and there is moisture on the ground. And I use gasoline only 0,15 l at each time. Oxygen tank is far away from the engine.

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2 hours ago, totalitor said:

No it is not. But I do test only when it is calm and there is moisture on the ground. And I use gasoline only 0,15 l at each time. Oxygen tank is far away from the engine.

It's not that easy to set up a fire on a forest. You need to have a decent amount of dry combustible material to catch fire strong enough to dry up the surrounding living woods so the fire can propagate

Living trees doesn't catch fire, you need it to dry first. There're thunderstorms on the Rain Forest as much as in the North Hemisphere forests, but we don't have florestal fires here (unless man made, but these guys uses gas or some other combustible to start the fire!). The reason is that the Rain Forest has so much moisture around that a fire does't evolve enough in order to dry the surrounds and propagate.

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Hmmm. Do you know how hot those coolant channels get? I'm wondering if you could just epoxy the rods in place, or if you'd need something more resilient.

Edited by IncongruousGoat

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Wow, there's some really cool stuff going on in this thread! I'm impressed :o

I've been thinking about building a paraffin / oxygen fuelled hybrid rocket engine for a while now, ever since I picked up a copy of "how to design build and test small liquid-fuel rocket engines". Paraffin wax and gaseous oxygen are very easy to obtain and safe to work with, so it seemed like they would make the best propellants. I'll need to do some experiments to measure things like combustion temperature etc before I can begin the design process though. Hopefully I'll get round to it at some point.

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That book is the same I used to design these engines. But I don't know how useful is that when you use paraffin wax. Go for it!

 

No more testing this year, winter is coming and I have to stop. Next summer I will continue building and testing.

The hardest part is cooling. I don't know if fuel flow is enough for regenetive cooling. I have to increse fuel flow velocity but becouse I want to keep things small there is not much fuel flowing. But I will try.

I have had 8 seconds combustion (some kind of)  in this year with three engines and one second was really good. Looking forward next year. 

Thanks for encouraging comments.

New video:

 

Edited by totalitor

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Very cool project. I always wanted to take a turbocharger and convert it into a turbine, I kinda lack the time or skill though. XD

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7 hours ago, totalitor said:

That book is the same I used to design these engines. But I don't know how useful is that when you use paraffin wax. Go for it!

 

No more testing this year, winter is coming and I have to stop. Next summer I will continue building and testing.

The hardest part is cooling. I don't know if fuel flow is enough for regenetive cooling. I have to increse fuel flow velocity but becouse I want to keep things small there is not much fuel flowing. But I will try.

I have had 8 seconds combustion (some kind of)  in this year with three engines and one second was really good. Looking forward next year. 

Thanks for encouraging comments.

New video:

 

Nice work as always :). I don't think regenerative cooling should be necessary unless you're planning on actually flying this engine, I'd stick with water cooling for the time being. On the subject of fuel flow - perhaps increasing the flow rate might solve some of the problems you've been having with combustion instability? It looks as if the pressure in the chamber is higher than the pressure of the fuel coming in, which prevents the fuel from flowing in at a constant rate, resulting in the inconsistent burn. Or at least, that's what it looks like to an un-qualified rocket enthusiast like me, I could be wrong.

You're also right that a lot of the design calculations in the book aren't directly applicable to a hybrid engine, but I've found that this book makes quite a good additional reference, and covers a lot more areas than the former.

As for my hybrid rocket, I've decided on a slightly different approach using these small canisters containing nitrous oxide (both a good oxidiser and a monopropellant) that are usually used to make whipped cream. This isn't a unique approach, and a quick google revealed that this has been successfully tried before by many in the model rocket community. I'm currently ordering parts to begin the design process, I will update when I've progressed further.

(As an interesting side note, it is actually illegal to build solid rocket motors of any size here in the UK, so if I want to see something fly then hybrids are basically the only option. )

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9 hours ago, totalitor said:

*snip*

Lookin good, and getting even closer, its looking like the flame regresses into the chamber once good combustion starts

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Thanks for the link, I have heard about that book. Have to read it.

In the last rocket engine there was material blocking fuel flow. Material move and caused that phenomenon. I know how to fix that but that has to wait until next year.

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This is proof scientifically accurate space battles aren't boring.

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On 9/20/2018 at 9:22 PM, IncongruousGoat said:

 

IncongruousGoat

Hmmm. Do you know how hot those coolant channels get? I'm wondering if you could just epoxy the rods in place, or if you'd need something more resilient.

Epoxy - at first I was thinking no .....

But that is a good idea. I continued thinking. What if I replace outer copper shell with epoxy layer? Rods are glued into it.

Sounds weird, this is a rocket engine and inside is 3000 C and I think epoxy. But if temperature raise above coolant boiling point the engine is lost anyway.

So now I am thinking mixing copper and epoxy. Crazy but true.

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1 hour ago, totalitor said:

Epoxy - at first I was thinking no .....

But that is a good idea. I continued thinking. What if I replace outer copper shell with epoxy layer? Rods are glued into it.

Sounds weird, this is a rocket engine and inside is 3000 C and I think epoxy. But if temperature raise above coolant boiling point the engine is lost anyway.

So now I am thinking mixing copper and epoxy. Crazy but true.

thats funny, im using epoxy for my pulsejet, which isnt quite as extreme, but its just interesting 

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21 hours ago, RoadRunnerAerospace said:

thats funny, im using epoxy for my pulsejet, which isnt quite as extreme, but its just interesting 

Cool! Valved or valveless?

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