Liquid Cooled Whoosh Rocket

now i know i say that the things that i make will probably blow up pretty often and they almost never do but this time i can guarantee you that this one probably will this is a two liter bottle that i use for woosh rockets to test things like whether or not i can make shock diamonds and testing different kinds of rocket nozzles but this time instead of the nozzle would be focusing on the combustion chamber or the bottle and seeing whether or not we can extend the burn time without totally destroying the bottle which we're going to destroy a couple bottles i'm pretty sure maybe [Music] the wish rockets that i've made before have two main problems first of all they tend to melt from the heat from combustion and they also burn very quickly now you could inject more fuel and oxidizer in but that just means the bottle would probably melt that much faster both integza and sam rogers have demonstrated the idea of using oxidizer to protect the combustion chamber walls from the heat of combustion and then using that oxidizer to also fuel the combustion now i think i can improve on this at least if not an outcome then maybe in theory by using my fuel which is liquid isopropyl alcohol to cool the combustion chamber walls instead of my oxidizer which is air and that's mostly because per volume it takes a lot more heat to heat up and vaporize this liquid fuel than it would to heat up air so the plan is to protect the bottle with a thin layer of alcohol which i'll probably spin down from the neck which shouldn't be too much of a surprise given that half this channel is just me saying i'll try spinning that's a good trick and then trying to blow something up but from there the heat from combustion that would have went into the walls of the bottle is now vaporizing some of that fuel so if we pump some air in we should be able to maintain combustion and if we recirculate that fuel we can ensure that the bottle is always covered so if something goes wrong with the pump or the flow of fuel at the neck then the rocket will basically become a hybrid rocket with an oxidizer in this case air being blown past a fixed amount of fuel in the combustion chamber which is usually solid but in this case is liquid isopropyl alcohol and as soon as that alcohol is gone there is nothing protecting that bottle from the heat of combustion so it's probably going to fail fantastically and in a hurry which i want to see that so it's time to throw some parts together [Music] this wasn't actually too hard to make with most of the complicated plumbing happening in the brass fittings air comes through a port in the side leading to a little tube that goes into the combustion chamber leaving enough room for fuel to trickle down into the aquarium pump that i salvaged from the dog that i made to pee on poison ivy from there the fuel is pumped up to the nozzle which i designed to spin the fuel along the inside of the bottle which for obvious reasons i also named bold and brash more like belongs in the trash and i made two variants one with a inbuilt nozzle and one with threads to accept exterior nozzles like the fan favorite squarow spike i i get it these external nozzles will be secured with o-rings and some super glue because i was feeling paranoid and it'll all be printed out of either clear petg or some wood pla filament that i thought would do a good job of charring before it melted with everything thrown together we can test this now with water so yeah there's some issues luckily the properties of water and my fuel alcohol are very different with alcohol having much less surface tension than water so resetting and retrying with my isopropyl alcohol fuel made for a lot better results so that's the film cooling more or less sorted out the ignition will come from a barbecue igniter which i'll clip onto some frankenstein bolts on the nozzle and the compressed air will be controlled by a solenoid which will in turn be controlled by a control panel that i made for an earlier video speaking of made in another video it's not lazy it's just a callback to the shameless plug reminding you to like share and subscribe to make the algorithm happy if you are enjoying the video the first test is just going to see how the whole system handles the pressure of combustion without injecting any air so just really the film cooling aspect and before this whole thing gets covered in flames i've got to say i find this just beautiful so the answer is no the plumbing can't handle all that pressure which i kind of knew that the pump couldn't i mean it's just an aquarium pump which is why i put it in a bucket but i wanted to try it anyway so clearly the issue is whenever combustion starts in the chamber the pressure travels down the tubes to the pump where the pressure differential between the combustion pressure and the atmospheric pressure is so great that the pump just explodes an easy solution to this is to build a container around the pump so that whenever it fills with fuel and is pressurized the pressure differential across the pump is almost nothing and all of the pressure differential between the combustion pressure and atmospheric pressure is held by that container so i went to the store and grabbed some pvc parts just big enough to fit our pump [Music] all right round two same thing i'm not going to inject any air i'm just going to see how well the film cooling system can handle the pressure of combustion so that went a lot better obviously than a pump exploding but there's still an issue watch right here [Music] so whenever the combustion first started it looked like a lot of that exhaust was being pushed down the tube that the fuel was supposed to be coming up now this seemed odd to me because gases in the main part of the combustion chamber should be moving relatively slow have a high temperature and a high pressure near the neck they should be faster moving having traded some of that temperature and pressure for velocity so if anything i'd expect a little bit of a siphoning effect kind of like a venturi and a carburetor which if you haven't seen that smarter everyday video you should it's it's good anyway what i think is happening is the fast moving exhaust is hitting the nozzle and creating what's called a stagnation point that basically means that our fast flowing exhaust is brought to a near stop and the pressure and temperature that was used to gain that velocity is brought back out and since this stagnation point is right next to the inlet of the fuel it ends up pushing exhausts down that tube if you want to see an example of a stagnation point you can look at one of my older videos where to demonstrate the danger of these wish rockets i just fired one at a hot dog and there you have it a stagnation point on a hot dog where the abrupt stop makes the pressure and temperature much higher making the gases easier to see as a side note stagnation points aren't a great thing to have on your skin all of that being said i think eventually the flow will stabilize and the stagnation point will go away which would be easy enough to test just by pumping a bunch of air into it but before i do i'll have to make a diffuser because i learned early on that without one the incoming air can just blow the film cooling off of the walls which isn't great so i need something to spread it out in this case i just printed out a little nozzle and wrapped some steel wool around it i've almost kind of forgotten about the stagnation point now because the dry out condition seems like it's going to be a real problem because if a dry spot forms by the film being blown away then that means the bottle is going to be exposed directly to combustion temperatures which won't end well for it but like i said in the beginning i went into this knowing that these were all going to fail but i'm trying to learn a few lessons on how i could extend the lives of these rockets and to do that the best way is just to test them so let's start with a sort of control with no film cooling just a little bit of alcohol on the bottom that will hopefully evaporate and mix with the air we're pumping in to make the combustion last longer [Laughter] [Laughter] so the mixture of air and fuel didn't go very well but you could also see the bottle start to fail almost immediately so now let's try it with some film cooling [Laughter] now aside from the fact that the bottle looked like it was searching for a couple of hobbits there was a couple cool things i wanted to point out first of all being that the exhaust did go down the tube at least a little bit but i think once the flow kind of stabilized it stopped and you can tell the pump is still working because it's blowing a ton of fuel out of the nozzle which means that we're also not getting a ton of cooling here and you can see that the bottle fails right where the exhaust splits on the wall of the bottle and lastly i was admittedly a little more focused on giggling that this actually worked than putting out the fire so by the time i finally put it out the fighter had done an astonishing three dollars worth of damage so after taking out a couple of loans i was finally ready to test this again at 80 psi instead of 60 psi on the air inlet [Laughter] some interesting things about this one besides the fact that the square spike didn't just instantly fail would be one the pinhole leak that was just spraying fuel out of it and then to the glow right at the throat of the squaro spike which tells me that the fuel mixed in with the exhaust might be the only thing saving the nozzle right now and then finally after the whole thing had been on fire for quite a while the air tube caught on fire and burst and with that smoldering mess i think it's time to bump up the air coming in to a hundred psi now with this one what to watch might be kind of obvious but if you watch closely at the neck of the bottle you can see it starts to deform before it explodes [Laughter] now i don't get my strongest prints out of this wood pla but that rupture was enough to shear off part of this bracket but besides using stronger materials for my prints i have at least one major idea on how to improve this which would be turning the whole thing upside down that way the exhaust and the film cooling are moving in the same direction and there's a lot less chance of a dry out condition now this obviously causes a lot of other issues which i have ideas on how to solve some of them but not all of them and if you have some ideas on other things that could be improved just let me know in the comments oh an update on bonnie and clyde the red sheltered hawks that live in my backyard they're two chicks i decided to name them luke and leia since their dad definitely killed a bunch of youngling birds and not only did they do that they also chased off a red-tailed hawk which was kind of cool but aside from that they had a pretty quiet little childhood and they grew up very very quickly and i hope they go on to terrorize other small birds and mammals and i also would love if like a barred owl use this nest next year but we'll have to wait and see i hope you guys enjoyed watching that as much as i enjoyed making it and if you did just do all the stuff that makes the algorithm happy i'm thinking about doing something mechanical for my next video but i also want to tinker with this a little more so let me know what you think in the comments and thanks for watching

Channel: Sciencish

Views: 117,303

Keywords: Sciencish, Scienceish, Science-ish, Whoosh Rocket, Alcohol rocket, liquid cooled rocket, 3d printed rocket, vortex rocket

Id: _LUGYZPiQFU

Length: 14min 47sec (887 seconds)

Published: Sun Sep 05 2021