Prototyping (Tiny) Rocket Injectors
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- Опубликовано: 22 май 2024
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Today we're prototyping some rocket injectors for a monopropellant thruster that I'm building! The two types of injectors we are looking at are Showerhead and Impinging injectors, and analyze them under various pressures with the high speed camera.
Videos mentioned in the intro:
- BPS.space: • Building A 1000lbf Roc...
- Xyla Foxlin: • ALL Carbon Fiber: My F...
- Charlie Garcia: • Making a Rocket Motor ...
- Project KegRocket: • Can you build a Liquid...
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Timeline
0:00 Intro
1:30 The Plan
1:55 The Background
3:09 Thruster Details
6:57 Injector test stand
8:44 1mm Showerhead, Single
9:13 1mm Impinging, Single
11:10 0.2mm Showerhead, Single
11:30 0.2mm Impinging, Single
12:30 0.2mm Showerhead, Full
13:16 0.2mm Impinging, Full
14:40 Best injector?
Select imagery/video supplied by Getty Images 
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Hi! I've worked on both monoprop peroxide engines and biprop combustion engines. For monoprop, you do not need atomization, and an atomization optimized injector will give you bad performance. Atomization is only needed when you need to vaporize your propellant (to ensure efficient combustion but irrelevant in a monoprop). All you need to do with your monoprop injector is make sure it's distributing the flow over the entire catalyst bed evenly (like a showerhead) and it has a large enough pressure drop to avoid feed system coupling (chugging).
Just what I was thinking. Impinging two reacting propellants makes sense whereas peroxide just needs good exposure to the catalyst.
Also, for a monoprop, are impinging flows needed, or could the flow from one hole just impact on a baffle to achieve the same effect?
No impinging flows at all. The best monoprop thrusters use just a showerhead with axial flow
0:34 "I am not an engineer", But I just happen to have access to high precision 5-axis CNC machines and Metrology equipment.
This alone kind of gives him such a huge advantage over all the others he has listed.
Yes friends, I feel blessed to find this channel
Same
This this is basically what I just commented on the last video of his I watched. This is now my third video in quick succession. The first one was the micro spheres on micro electronics and tape, and the second one was the ion blaster. If you haven't seen those, go check them out. They're absolutely fascinating.
I have been making a peroxide rocket at home. I made my own 90% peroxide. I used a vacuum distilation set from Ali Express and a refrigeration vacum pump. Ended up being alot easier then people said and was a fun project. I'm using stainless steel nozels from a misting fan. They attomise great and come in heaps of sizes.
I could not possibly be more excited for a project! Great work on this so far, and man that high speed footage is beautiful. Also LMAO 0:35 if you don't qualify as an engineer, I'm not sure who does
You
🥰🥰🥰
Im still sad you view hybrids that bad :( especially for European student groups it’s the best option - did you see e.g. the North rocket build by HyEnD. It set a new record earlier this year.
Hybrids have their flaws but also some really good points in favour especially in terms of safety.
We at Vaya Space will show to the world very soon how amazing hybrid rockets can be!
Aerospace engineer here. Love this channel. Always a cool topic.
I was terrified at the beginning of the video when you said that you were going to build a monopropellant rocket. I though that meant using high percentage hydrogen peroxide and it’s pretty nasty. The lower percentage stuff is lot safer so I’m glad you went that route.
That said, make sure you read up on proper storage. I remember reading a story in my textbook about a lab technician at Purdue not properly venting a container of hydrogen peroxide. Since it’s constantly decomposing it can build pressure before “violently decomposing” which will destroy the pressure vessel and shoot shrapnel everywhere.
I’m sure you already know this. But the only other thing I’ll say is make sure you build your combustion chamber out of a ductile material like aluminum. That way if it explodes for whatever reason you also don’t send dangerous shrapnel everywhere 😂.
Yeah, I've seen what it looks like when forces are enough to literally shatter steel. Don't want to be anywhere nearby if that ever happens.
Been storing it in a mini fridge, and burping it occasionally to relieve pressure (if any) 🙂 I did see some pretty wild containers for the high test stuff, which have built in expanding bellows to accommodate the decomposition. Pretty scary stuff tbh! Even if I could find a vendor for higher percentages, not really sure I'd want to. Reading through Armadillo Space's archived dev blog is equal parts fascinating and terrifying 😅
Interesting point about using a ductile material. I was actually planning the opposite, building it all out of stainless. But using a weaker material does make a lot of sense. Will think about that, and also see what kinds of pressures the electric pump feed generates.
I do plan to "fire" it only inside a safe enclosure. Will probably weld up a steel box and surround it with bricks and such. I dont have a lot of background in energetic stuff, so planning to be suuuuper cautious and extra safe :)
It’s not about strength! Use a good strong material!
What I’m talking about is the how the material fails. Ductile materials like aluminum will pop open and vent an explosion. On the other hand more rigid materials like a hardened steel will fracture causing shrapnel (pipe bomb). The shrapnel would be the real thing to worry about.
Hope that helps!
@@mmmmm49513 another good approach is to have bolts designed to fail at X times MDC so that the nozzle blows off in the event of a chamber overpressure. Great place to use materials like brass (or even plastics) for the bolts
Aero here too. I have a liquid 50lb biprop on my channel. I had that same feeling about the real deal High Test H2O2. Treat it like LOX. Get it and use it on the same day.
Also, I forewarn that the pump will be the most difficult part of this adventure. Materials, seals, bearings, heat,... All of it. Rockets fundamentally don't have any moving parts.
For your injectors the L/D ratio of your injector holes is more important than the diameter.
While testing, check valves will help with consistency at startup due to their crack pressure.
Welcome to boiling the ocean for troubleshooting and good luck!
When filming stuff like droplets and jets, you could try putting some white acrylic (or something similar) behind your experiment as a diffuser and illuminating it from the back, in my experience that gives better contrast and introduces less heat. Very cool project :)
Will give that a shot next time! Getting good high speed footage with enough contrast was _super hard_
@@BreakingTapsCan We Just Put A Metal Net Of Some Durable Material 😅???
Or
Can We Put Spraying System And Catalysing System In One Unit In Which The Sprayer Is A Cylindrical Structure Inside The Catalyser ???
And Then We Angle The Nozzles Of Sprayer So That Tiny Water Droplets Are Formed ???
This is a good idea. I've also seen really cool water-droplet photography using 2 colored lights at 90 degrees from each other.
No black background and light from above or below
Can use a reflector sheet to diffuse it, or diffuser cotton cloth
Nice work and amazing footage! 🚀 Great example of the intricacies of injector geometry and associated effects.
Love what y'all are doing! Should have mentioned you in the intro and totally overlooked it. Been following your project for a long time now, what you're doing is amazing. And you have some very cool videos on injectors 😎
@@BreakingTaps Wow, thanks, the admiration goes both ways! 😊
It looks like the next step in testing will be to build a better supply for your pressurized liquid. You’re getting a lot of air in your “propellant”. I think a piston pressurized with air on one side would work better. That way you can bleed it.
Great video. I’ve been thinking about doing something like this for a while. I look forward to seeing what you come up with.
He also said he plans on using an electric pump, not pressurized air, so they should yield better results
Or a balloon sac. Keeps liquids and gasses separate. Very low friction
Well now. Using a "piston" driven by air, instead of redesigning the airstream, is one of those "quietly brilliant" solutions.
It has all the best qualities:
1) Simple to manufacture using tools you already possess.
2) Does not REQUIRE (and I stress the word "require") redesign of any of existing components.
3) does not REQUIRE changing the design or principles of any other part of the system.
At this stage, all you are trying to do is drive the propellant through the atomizer at the required rate.
I have seen teams disappear down rabbit holes of ever more "brilliant" designs requiring ever more complicated and time consuming machining which, for this purpose, was completely unnecessary. (Ask me how I know.😢)
This is design and trial. The ONLY part that has to look like the final product is the part under test.
I love how everything seems to "change" when you start to deal with the "very"... The very fast, the very small, the very high power, even the very low power, the very high vacuum...
Suddenly, issues that previously could just be ignored suddenly become relevant or even dominating!
This series is going to be very, very, interesting! 😃
Thanks for sharing!
What a great observation! 👍
This is going to be an incredibly interesting build!!
I cannot wait for the rest of the development.
The visually striking difference between 0.2mm and 1mm holes is due to the squared growth of the area of a hole; the holes are 25 times smaller, which is more aligned with your perception of size than thinking of it as having a radius 5 times smaller.
This might be some of the best injector plate footage out there. I've seen animations for the doublet impinging injectors, but to see them really happening is very cool.
If you have the free time I'd love to see some exploration of some of the other injector designs
You can use an Agricultural sprayer nozzle for that, it atomizes very well, and you can choose the shape of the sprayer, from a triangle to a hollow cone, and the materials too, up to ceramic nozzles 😊
Sprayer nozzles are used in may sizes and mist/spray patterns in the industrial food market. I uesd them in systems that sprayed baking pans mostly.
8:00 you may want to consider using a mirror to film with the high speed camera, so that you don’t have to worry about damaging it, only the mirror
This is insanely cool and I am all for it. Absolutely love learning about anything aerospace related.
I gotta give mad props to you because in your opening you point out basically, specifically & exactly what your gaps in your knowlage of this subject are!
That said, to expand upon your opening "Why?" question...
In other words... "Being too stupid to know it can't be done!"
This was why I was hated in my chosen career, Jeweler! When asked how I did it when others said "Couldn't be done!", this was my response;
"I dont know I guess I'm just too stupid to know it can't be done!"
What is crazy to think about, is how much propellant flows through the injectors on a full scale rocket engine. For example, each Merlin engine on a Falcon 9 burns 350 pounds of propellent a second. 350 pounds of fuel and oxidizer, being forced through an injector array a the size of a dinner plate, every second.
It's totally nuts! And they are cryogenic too!
Fantastic video! This was amazing!
It's great to see your channel getting more into rocketry stuff. We do, of course, have a lot of very high quality DIY rocketry content on RUclips, but your machinery experience and tools shows this from a completely different view. Would love to see more of this!
0:34 "I am not an engineer" then why do I hear Team Fortress 2 music every time you're in frame?🧐
Amazing footage!
Great stuff! Facinating
You should look at diesel injectors in this case for inspiration. These are designed to aromize fluid to a very fine degree and their tip design is very well studied and researched.
Will take a look!
@@BreakingTaps from my experience, two things might be worth trying from the diesel world: pintle-style injectors (which can be turned on a lathe-no microdrilling) and voice-coil based injection (where a vibrating membrane is used as a pump and to break up jets into a steady stream of droplets).
I’d also take a look at using automotive fuel injectors and components. If you want a full system it’s going to be easier as well since it lower pressure and components are easier to get.
that's some great highspeed footage. rockets are fun, I'm here for it.
The low fps camera footage is so great. With those small holes you might need to change the name of the channel to breaking end mills.
As always, great work, magnificent content and big effort to deliver it. We appretiate it a lot.
This is some of the best injector footage I've seen! Super cool video and I'm excited to see how this turns out!
Thanks Charlie! And appreciate all the help you've given so far! 🥰🥰🥰
Wow! Metal in and part out! Nice!
YESS! I'm very excited to see you doing rocketry!
Now, I'm also not a rocket scientist, but if I wanted to do a monopropellant rocket I'd probably not worry that much about injection, and just have series of fine silver(ed) meshes to pump peroxide through. Possibly by using the pressure increasing due to boiling to push peroxide through finer and finer catalyst meshes/sieves it can create sort of feedback loop...
This was a fascinating video for me. I have heard of impingement injection nozzles in relation to rocketry for decades but have never had a clear understanding of their function. Well, until now. Thanks.
my gut tells me, that attaching a ultrasonic transducer to the nozzle plate could help disperse the liquid even better. Also it could help in cases where individual nozzles plug.
Thats just my instinct, never seen it, never tried it.
Awesome! Thanks!
Cool project my friend One suggestion I would highly recommend it play more with pressures. Think about fuel injection. Old stuff like the early 70s used 30psi stuff. My 6.4 diesel uses 28,000 psi. The more pressure the better the spray. Really below 100psi I don't think you will ever get reliable atomization. And I do think you will find better atomized peroxide will relase more energy. Each droplet will have a surface tension and will be spinning. Theoretically it will give better contact to the catalyst. And for nozzle testing try a bigger tank to give you more time to study the spray. Anyway will be really cool to see how it progresses.
Not to be a snob
But according to This Old Tony...
When a machinist is pointing at something you need to point with something technical.
In other words when you were pointing at your 3D printed model of the rocket. You should have used the back end of a Mitutoyo digital calipers, or a ruler that measures down to tenths...
All joking aside, I'm very excited to see where this is going.
Rockets are cool!
Or a sharpie marker that teleports through time throughout the video 😁
@@BreakingTaps Touché`!!
Score is one nothing your favor :)
Well done making a shower head
🚿
This may be my favorite channel on the entirety of RUclips. I love this.
Awesome series. You've finally convinced me to buy Nebula on payday. I love watching your channel, but it makes me feel very unaccomplished, lol.
I used to make candy motors a long time ago before i had kids, i really must get back into it. Time to find a lathe.
Hah, I feel the same way when I watch other creators on YT like Shane at StuffMadeHere or Joe at BPS 😅 Like how tf do those guys get so much awesome work done?! The struggle is real🙂
A little late to the party, but you can (somewhat safely) distill 35% H₂O₂ up well over 90% using a vacuum still and a heat source. Even a 100W light bulb is enough heat to distill with a decent vacuum, although I found that IR heat lamps for reptile cages worked perfectly and didn't also blind me while distilling. Just make sure you have a very clean vented stainless or aluminum container to store the HTP in after distillation and keep it cool and out of the sun. 90% H2O2 and most plastics are a bad day. You don't have to distill very much to have fun, I used to get 55 gallon drums of 50% and distill a gallon or two at a time and I always tried to use it all the same day.
Watching your video I was reminded of two names - Richard P. Speck of Micro-Space and Dr. Adam London of Astra. Both are/were professional aerospace providers (We sadly lost Speck around 2010) with maverick outlooks.
Speck ran a successful(!) aerospace company with some of the most gonzo engineering I've ever seen. His low pressure liquid-fueled motors used unconventional materials like fiberglass and resin, and his design for a minimalist lunar launch platform used angle aluminium framing and medical rubber tubing in the shock-absorption system. It was terrifying when compared to more conventional design, but when I met him he also had more than a few of his commercial launches (sounding rockets for the weather service) at hand to show that the principles were not nearly as insane as they looked. He was the kind of guy would makes world-record smallest/lightest orbiters in Kerbal Space Program, but did it in real life.
Dr. London is an MIT grad who founded Asta. His post-grad work isn't nothing, but it's what he did at MIT that really made his name. The interest at the time was in micro-rocketry systems. Some principles of semiconductor MEMS design could be adapted to handling combustibles and could theoretically be used for ultra-small probes or station keeping for satellites.
The top of the line at the time was a solid-fuel array on a chip. Essentially, it was a bunch of explosive wells piercing a conductive sandwich with traces to allow specific wells to be detonated at will. The wells were separated enough to prevent chain firing. It was a good way to store a small amount of delta-v for long periods of time without worrying about the vagaries of pumps and the behavior of liquid fuels in microgravity. The downside was that it was a chip die with tiny firecrackers in it. The delta-v budget sucked, especially compared to its mass.
When Dr. London did his work, a MEMS pressure pump had recently become availble. So, he decided to see if he could use semiconductor tech to make a MEMS-scale rocket nozzle. It was cool AF. It looked like a little almost-2D bell nozzle made of layered metal and was _tiny_. I have to assume it didn't work because Astra doesn't mention it, and there are a tremendous number of applications for a chip-scale turbopumped liquid-fueled engine. There were discussions of building orbiters with the mass of a small car that could deliver 13-oz payloads to LEO and the linke, it was wild.
Even though Speck is presumably designing sounding rockets in heaven (one of his non-commercial sponsors was a Baptist church!), we still have Dr. London. You might consider reaching out, or not. Either way, you're doing something cool and have cool peers.
Great project! We'll be following along too! The kids are loving this! No, Pluto, let go, that's not a new toy, that's a bottle of hydrazine...
Hey, enjoyed the vid. I have worked with HTP and here are some advices. I recommend to use showerhead injector for the catalyst bed and design the orifices so that you would have a pressure drop across the injector about 20% of your cat bed pressure. Use transverse injector for the fuel injection. You would need enough chamber length and pressure for the autoignition of the fuel.
Love the footage 😮😊
I have been working on a similar project only with goal being parallel extremely laminar streams. I built a much larger fuel tank I could pressurize that prevented air from mixing with the fuel. I used cam lock fittings so it’s easy to refuel.
I also found smaller holes are way way better for getting good streams. I started with .003” sapphire orifices but found that the .1mm PCB drills on Amazon also work quite well. They are also super cheap and more resilient than i expected. Adding a super fine SS mesh filter screen is also a must since any small particles will clog the nozzles. I tried polypropylene filter fabric but the tiny fibers can come loose and cause clogs themselves.
In what material(s) have you drilled these 0.1mm holes, and how deep? Thank you.
You should look at the nozzle on standard garden hose sprayer. One of the settings in those little 6 position ones is usually a mister that atomizes the water quite well. I wonder how that one functions.
How about an angled deflector baffle right after the nozzle holes? The streams would hit the baffle and scatter in different directions like water hitting a flat surface at different angles.
Nice work! Keep this up and we're going to need you to build an impinger for the KegRocket!
I will absolutely and happily make any parts you need for the KegRocket! 🤩
Very well done.
Always impressed with your effort level & build quality. Couple things. 1. BI-Prop injectors use different sized holes AND impingement angles from inner-outer rows. 2. There is no benefit of impingement for a mono-prop. Impingement is for mixing fuel and oxidizer for more efficient combustion. With a monoprop, the catalyst releases the oxidizer stored in the fuel.
3. Hybrids have thier place in propulsion, there is not a one tech solution in the rocket-world. There are always trade-offs.
Hah this is going to be an exciting series. I haven't dabbled in rocket making after I got grounded in high school due to a candy accident You fellas are making me interested again 🤣
Another aerospace guy here working on a pretty cool engine at work (albeit the electronics) and this is almost cooler than that. Awesome stuff dude, can’t wait to see where it goes just always remember to take safety 1st!
0.2mm thats about the smallest mechanical via size before laser vias take over. Repairing my oil boiler , the nozel was amazing, 60 deg cone , three spiral jets. Beautifully made. You can dismantle them easily. £9 Danfoss. maybe some bits you could use. Fascinating as always. Nebula sounds worth a look.
love your videos
I like the channel, but this video is the best thing I've seen you do. Love love love this footage.
Dude, this is a full-on research data video. Good on you mate! Looking forward to the rest =)
Patently late to the party and probably way past useful at this stage, but I'm going to post it for legacy use. Some years ago, I was rebuilding a jet engine from NOS parts and got held up by the fuel nozzle. Operating principle vs rockets is a bit different, but I had an absolute ball once I figured out the geometry of the nozzle ports. With jet fuel/air-breathing combustibles, having a hollow cone nozzle that converts mass high pressure fuel flow it truly atomised spray is highly desirable, so I spent a few months trying alternatives. In concert with 2400psi repurposed pump and hardened steel nozzles, I found great success a converging .375" input to .00393" singular exit with either a taper cut in the input flow to 0 or 15* flare cut around the nozzle exit produced Beautiful hollow conical spray patterns.
If one were so inclined, adding a secondary channel directly into the conical spray pattern would be an ideal route to introducing an oxidiser component. Now with a relatively small rocket, you probably wouldn't need the full 2400psi fuel pump, as for my use case, I was injecting into a 300psi airstream and had use for the spray pattern to overcome some of the restricted pattern that would result. In testing at atmospheric pressure, the nozzle would produce a roughly 240cm wide cone at the max cross section, but with added air pressure, about 215mm to perfectly flow inside a combustion liner.
i love nebula it supports all my favourite channels
The size difference between 1mm and .2mm is only about 5x smaller in diameter, but its about 24x smaller in area, that's why it looks SO much smaller.
I love this sort of content. I live for the puzzle.
I'm not sure about which is better, the shower or the doublet but I wonder about three points. I bet the ports have a bit of swarf stuck that would break out if you lightly chamfered the holes. I also suspect that 200um is still a bit big. You might consider either electroplating some material on or building an anvil with corresponding points to bulge the center of each port into a venturi geometry. Finally, I think that you need to make your water 'wetter'. The smallest amount of detergent with no flocculant would do that job. I have no idea what the surface tension of H2O2 or what it would do to the H2O2. Might be worth a try.
For injector geometry, and ease of milling, could it perhaps be worth it to use a conical bit to make a shower head style injector? I could think of 3 solutions with this:
1) the big end of the cone is on the inlet side, and small end on the outlet side.
This could perhaps help create a lateral force for the liquid as it exits the orifice, which should break of the laminar flow.
2) reversed, so small end on inlet and big end on outlet side. The more gradient pressure drop as opposed to a regular shower head hole, could perhaps help the stream to separate instead of starting laminar - a bit akin to a waveguide for a speaker. I’d assume a 60degree bit would be better for this case than a 110, as we’d most likely need a slow expansion for the liquid to actually expand.
3) a combination, so drilled from both sides. This could combine both of the above mentioned potential effects.
Looking forward to any feedback :)
10:05 yeah it's always hard to appreciate, especially with area, as a 1/5th radius/diameter hole has 1/25th the surface area/volume (assuming the same depth).
Wow. Just the best channel on RUclips
I wish I had the time and the money and the smarts to do stuff like this. Unfortunately I have none of these but I do enjoy living vicariously. Really fascinating stuff that I mostly understand. People like you enrich my life. I have pet cats, I try to enrich their lives by doing things they don't really understand but captures their attention. Same thing.
So I wanted to try building a monopropellant engine using a modified Ranque-Hilsch vortex tube. The design was to run the injector partially reacted into the offset intake side port, and use a catalyst mesh wrapped around an adjustable, perforated, "cold return" tube through the center of the body. The "cold" air is redirected 180 degrees back over the body, and both hot and cool air are used as thrust.
Looking forward to part 2
Would you want a cone shape going from the pump outlet to the backside of the injectors? In all the diagrams there are manifolds to guide the fuel to the injectors.
Great liked and subscribed. Next stop nebula 😊
Interesting you decided to go for an injector plate for the mesh bed version. The papers I was digging through on the topic usually just started blasting it in liquid with the occasional distributor plate to prevent hotspots.
I'm really curious to see how misted peroxide will interact with catalyst bed now haha.
Thanks for sharing!
Awesome video, can't wait to see the full project while it develops.
Even cooler t-shirt! Are you using it for your projects? I'm interested to talk about Rust and space technologies 🦀🚀
I don't do much programming anymore tbh, but I try to use Rust for fun projects when I can! Sometimes python is easier for quick prototypes because there's a scientific library for everything, but Rust is just fun to work with (for some definition of the word "fun" when fighting the borrow checker 😅)
If you increase the pressure drop across the injector, it will even out the flow rate through your injector elements. In your case this will probably mean you will need a larger diameter feed line for your injector feed or reduce your hole size.
This pressure drop through the injector will also help you significantly when you actually go to run your engine. Your pressure drop is essentially your safety margin. If you have a combustion pressure excursion and your pressure drop is too low it will cause your combustion pressure to exceed your injection pressure which will stop or even reverse your propellant flow. In practice this will result in whats called pogo or chugging instability because it causes a low frequency oscillation of combustion. As the flow slows down from the high pressure, then speeds up again as combustion slows and the pressure drops back down and keeps repeating this cycle.
I've done some work with 90% peroxide, and it is indeed its own special animal.
Great footage! What high speed camera is that? Chronos?
Thank you
It always amazes me how well a simple plant spray bottle atomizes the water. I don't really know how the atomizer works, but it looks like a good place to start(?)
Wait that nebula video sounds so good
I don't know if old CNC machine, I notice some new precision CNC machine can drill holes at micro degree angles cause the injection of fuel to spiral. This cause the flame to spiral. Another ideal was to divide the manifold into four section.and allow for time injection to cause a spiral burn.
I'm wondering how convergent nozzle holes would affect the atomization. Also, maybe you could make a backplate that functions as a manifold for each ring of holes. It would take some tweaking, but I bet you could get close to even pressure between each ring.
This is very cool, I love it. I don't know why you say you're not an engineer. I recommend you check out photo etching. A sheet of pretty much any metal eg. 0.2mm Inconel is chemically etched from a precise mask. You can get holes and cut-outs and partial etched areas too. No angled holes though.
I bought a 1m x 0.5m sheet for £200 and on to that sheet you could fit hundreds of test pieces or finalised parts.
Great project.
You will probably run into pump cavitation at some point.
You may get better results if you ignore the nozzle plate and simply fill all your sections with catalyst bed.
Round disks of silver (plated) mesh filling the whole cavity probably easiest.
Look at what the H2O2 tip jet helicopters and jet packs have done, a lot of the hard work has been done for you.
Your impinging jets were beautiful but somewhat overkill for a mono-propelat that has to pass through a catalyst bed afterwards.
You might try to look at swirl injector, you put a swirler (just angled surfaces) followed by a convergent section, the fluid will keep the rotation velocity on a much smaller diameter generating a nice attomization when exiting the hole.
This is a really cool project you're working on!! I was wondering how much theory was used in your design as I have a few point but I'm not sure what you've considered already.
Excellent.
I can’t wait for the next instalment
"I am not an engineer"
knows more than most engineers I work with.
One option might be to mill channels into the rear of the injector plate to help increase the localised pressure around the holes, which should equalise the flow a bit better.
Yeah I think you are right. Looking over the footage more while editing and it was really clear the "order" that the holes were pressurized. Making some features on the backside to distribute it better makes a lot of sense.
@@BreakingTaps I wonder if length-matching the paths to the hole, almost like matching impedance on a PCB, might be a good option here. You'd probably also need symmetric angles on any forks to avoid uneven distribution. Something like pumping all the fluid into the center, hitting a conical detent to correct for flow nonuniformity caused by any burrs or geometry variations the fitting, then uniformly separated outward channels with some snaking to avoid length mismatch... seems like that would probably give you even flow to all your target nozzles.
I read and watch long time ago some succesful tests and designs using tiny 3-4 layers of platinium, gold and paladium wire mesh. only one tiny hole in the piece. 3 pieces per rocket + the grills. it was a big university study published in the MIT from Mexico, not the other MIT
i got my first model rocket when i was 8, by the time i was 10 i was building multi stage giant rockets with D cell solid fuel engines, when i was 14 i started tinkering with my own solid fuel engines and within a couple of weeks the FAA, ATF, the cops and my parents were sitting at the dining room table discussing how i'll never be playing with rockets again and some of the things that will happen if i do and they took all my stuff
*Overview*
- The video focuses on prototyping rocket injectors for a monopropellant thruster using hydrogen peroxide.
*Background*
- Monopropellants decompose and provide thrust, typically with the help of a catalyst.
- Hydrogen peroxide is used as the monopropellant, which decomposes into oxygen gas and water vapor when it contacts a catalyst.
*Design*
- The thruster consists of an injection chamber, a catalyst chamber, and a rocket nozzle.
- The injection chamber will have nozzles of different sizes and geometries to spread the peroxide into a fine atomized spray.
- The catalyst chamber will be packed with a silver catalyst to decompose the hydrogen peroxide.
*Injector Test Stand*
- A CNC-made test rig was used to try out different injector geometries.
*Types of Injectors Tested*
1. *Showerhead Injector*
- Array of holes to spread the liquid.
- Tested with 1mm and 0.2mm holes.
- Atomization increases with pressure.
2. *Impinging Injector*
- Angles two holes towards each other so the streams collide.
- Tested with 1mm and 0.2mm holes.
- Atomization is much better with smaller holes and correct angles.
*Observations*
- Full showerhead behaves differently than a single row, merging streams at low pressures.
- Impinging injectors need to be in perfect order for effective atomization.
*Conclusion*
- Both types of injectors have pros and cons.
- It's unclear which will work best in the final thruster design.
*Additional Content*
- A companion video with more technical details is available on N_b_la.
*Positive Learnings*
1. *Effective Atomization with Impinging Injectors:* Using smaller holes and correct angles resulted in much better atomization, which is crucial for efficient fuel mixing.
2. *Showerhead Simplicity:* The showerhead injector's design is straightforward and could be more robust for consistent performance.
3. *High-Speed Camera Insights:* The use of a high-speed camera provided valuable real-time data on how the injectors behave under different pressures.
4. *Modular Design:* The thruster's design is modular, allowing for easy swapping of injector plates for testing different geometries.
5. *CNC Test Rig:* The CNC-made test rig proved to be a useful tool for trying out different injector geometries.
*Negative Learnings*
1. *Impinging Injector Sensitivity:* These injectors are sensitive to alignment and hole size, and any imperfection can lead to ineffective atomization.
2. *Flow Rate Issues:* The full showerhead emptied the tank quickly at high pressure, introducing air and complicating the results.
3. *Unclear Optimal Injector:* Despite the tests, it's still not clear which injector type will work best in the final thruster design.
4. *Material Sensitivity:* The video mentioned that high-test peroxide can be sensitive and potentially dangerous, limiting its usability.
5. *Complexity of Variables:* The number of variables like hole size, pressure, and angle make it challenging to pinpoint the optimal injector design.
Enjoyed the intro, but not nessacary. I appreciate your interest in the sciences and your ability to share your experiences on this platform.
Try using a rowed injector assembley with a conical deflection plate at .2mm under high pressure the laminer flow and stream will hit the deflector and atomise
Imagine the life of this man. "Oh boy, I'm so bored. Let's make a rocket engine to liven my day up a little". It's awsome.
Dude I'd watch hours long videos.. great stuff!
In a past life i worked with some very very fancy showerhead spray nozzles. They used triangular holes to increase atomization.
The juice probably isnt worth the squeeze for this project, but it might be interesting to investigate hole geometry.
Interesting. Think spraying into high pressure would perform differently.
You may want to try nozzle geometries like the ones used in weed sprayers, that work just like your impinging design but are also a little simpler to make IMO. (i think they're called fan nozzles)
I played around with those spray nozzles with my 3d printer and there's alot of configurability, where you can configure your flow, your angle of spread (width and height of the spray pattern).
And the geometry is very simple, even my FDM printer was able to make these spray nozzles work well.
have you considered using manganese dioxide if you formed it into a pattern like a rod and tube from solid rocket boosters and arranged a set of impinging injectors with the vaporization point in the middle of the empty space you might get a pretty great result?
Keep it up!
Very cool
Maybe you should try coating steel wool in the silver! That might give more surface area, and produce a better result if the wire mesh doesn't work well enough
I think it wold be interesting to see an inpinging system with 5 or 7 streams pointing to a single pount,
Then having the outer portion of the injector have the regular showerhead style holes.
Also I believe that having the thruster virtical rather then horizontal would give a more even flow through the injector.