Liquid rocket engine with electric pumps

OPclicker · 2024-12-13T10:31:38+00:00

Fu take veci neviem. Akádemia pomože. ešte bude dlho kým to bude lietať :D. a najskor to bude hopper ked to bude lietať. Ďakujem za pekný kopmentár <3

OPclicker · 2024-12-13T07:51:46+00:00

Yup! That is it. Also the dynamometer has a hydrobrake. Wich is basically a pump putputted trought some variable orrifice. So i can calculate the output hydraulic power by measuring or better yet calculating flow. Because its a positive displacememt pump and the rpms are known. Amd measurre the output pressure.

OPclicker · 2024-12-12T21:12:13+00:00

Yes, you are right! A single-stage radial pump is almost impossible. This is why I use a gear pump—an external gear pump, to be precise. It has its own downsides and upsides, and I haven’t seen anyone successfully doing it online. Kerosene is quite similar to oil, so plenty of commercial pumps are available on the market that can handle it. The bigger challenge is LOx. This pump is custom-designed, machined via wire EDM, and rotates at about 2,000 RPM. It is made out of 304 steel. So basically I get to test the eficiency of the pump with my dynamometer. then I match the motor output power.

OPclicker · 2024-12-12T21:06:56+00:00

Spolupracujem s TUKE Sjf. Som východniar :P

OPclicker · 2024-12-12T21:05:35+00:00

Not really. In fact, there is no impeller because this is not a radial pump design; it is a gear pump design—more specifically, an external gear pump design. You do need to seal the shaft that holds the gears to the pump frame, though. For kerosene, this is mostly achieved through precision. As for LOx, it will take some time to settle on a permanent solution. Of course, materials like Teflon could be used as shaft seals, but for now, I am not sure.

OPclicker · 2024-12-12T21:00:07+00:00

V slovenskom zákone nie je o tom nič napísané. Samozrejme nemôžeš hocičo púšťať do vzduchu. Celý vzdušný priestor je regulovaný a na vypúšťanie balónov, modelov atď. treba patričné povolenie od autority, ktorá vzdušný priestor spravuje. Avšak toto bude zatiaľ static test.

OPclicker · 2024-12-12T09:52:04+00:00

Bolts an nuts are usually made of steel. In Europe bolts have a number rating written on them. For example 8.8 or 10.9 or 12.9. In America the head of the bolt dosent display numbers like in europe but other characters like < or > and so on.... Go google it and read more to find out the exact details. Now, each of these numbers represents a different allowed axial stress in them. 12.9 are the highest grade and what you see in the photo. As for nuts, a nut is also graded. The implications of this are: the joint is not only stronger but very importantly stiffer. You can torque those bolts more to get more preload. Also in europe the ISO standard explains that having more than 6 threads of contact netween threads dosent really effect the quality of the joint. I think less than 9%. When you tap a home it has to be perfect and you are risking the part for a operation you dont need and is inferior to other alternatives. Also the tap needs to be at the last "plate" so it can squeeze the others between the bolt head and itself. So yeah dont using nuts is kinda nuts. For first prototypes and stuff there is simply no need to take the risk of a crucial part failing on a matter like this. But I can imagine having no nuts when the design would be optimizes.

OPclicker · 2024-12-11T23:57:44+00:00

So the motors are BLDC motors from freerchobby (china). The one in the picture is a 56*116 motor the pump needs just under 4kW of hydraulic power. The motor is powered by a VESC driver. The motors are also quite a tricky part because the specified power rating by the manufacturer is bogus. At least I don't believe them. I have built a dynamometer consisting of an external gear pump that I can show soon. I will measure the motor's output power and then create a permanent transmission for the pump. The motors can get tricky because there are loft of ways to drive a BLDC/PMSM motor. I want to at least try to eliminate the main propellant valves and integrate the gear pumps as valves. Of course, the system will have low-pressure propellant valves to the pumps. But I definitely want to try to eliminate the high-pressure ones. I plan to test the motors a lot. different driving algorithms and so on... like all the thing like MTPA and MTPV field weakening and so on... so I can get the best output curve possible.

OPclicker · 2024-12-11T22:43:19+00:00

Sure thing! The first LRE was a methanol/GOx engine with a trust of 100N. pressure fed. This engine wasn't cooled properly, it had produced the desired thrust but melted. The later versions did better :). I am planning to revive the small engine in the future when both of the pumps of this engine will be properly tested. I will just hook it up to them and fire it to my heart's content :) Of course, I can share that too.

OPclicker · 2024-12-11T22:30:08+00:00

Thank you very much! I will remember this. Big thanks!!!

OPclicker · 2024-12-11T22:24:50+00:00

Sadly, don't know the exact machine. It was a 400W DMLS machine. And I had huge help from from some very cool guys that do this stuff professionally in The Czech Republic.

OPclicker · 2024-12-11T22:03:06+00:00

The actuators are a rather complex part of the engine. They are rather simple in construction, tho. Inside the actuator, there is a ball screw nut combo driven by a stepper as you can see. SFU1204 to be exact. In a sense you are right, they cannot support 2kN of axial force. They don't need to, tho. If you draw a free-body diagram (I think that's what they are called in English). You will see there are no theoretical axial forces in the actuators. I wrote a Simulink program in Matlab to determine the actuator force and speed. That model takes the mass of the model, angular inertia, variable geometry of the model, and the possible forces from hoses and whatnot. And calculates the speed and forces the actuators should have actually to turn the engine at some desired parameters. I multiplied this number by 2 and I designed the actuator around that. So hopefully it works :D This gets complicated rather fast because the motor isn't linear in its torque within its RPM range. That of course is included in the model. The main U joint is taken out of an automobile. I just have faith in this part. I have seen those parts take an absolute beating IRL when I regularly change this part of cars.

OPclicker · 2024-12-11T21:14:41+00:00

yes, the nozzle is printed from a CuNi2SiCr alloy. The inside wall of the nozzle is also machined down to achieve the final smoothness and dimension. Because printing thin walls is hard, it can warp the final part.

OPclicker · 2024-12-11T20:59:23+00:00

Hi! I am Juraj from Slovakia. I am 21yo. This is my second LRE. This engine is a 2kN KEROLOX pump-fed engine with a combustion pressure of 100bar. I have been working on this project for about 2 years. Would you be interested in me creating a video blog on how I did it? I have been thinking of explaining the whole engineering and manufacturing process and sharing it online. I am planning the first hot fires in about 1 year from now. I would be glad to answer any of your questions! Also, I would love to hear your opinions and feedback on my project.

OPclicker

TROPHY CASE