| User | Post |
|
10:38 pm
December 12, 2010
|
Nick
| | Florida | |
| Member | posts 34 |  
|
|
|
Post edited 10:44 pm – December 12, 2010 by Nick
Hey guys, Sorry i've been absent. been a busy month.
I've seen some ideas tossed around for an ignition system, and I thought I would share my experiences.
The system I am going to show you is based off of a commercial solution, not sure which, but adapted to the specific engine we tested.
The basic theory is to flood the Chamber with GOX and ignite it. Combustion starts, and when the engine is hot enough, N2O is released from the tank and the engine ignites fully.
Here is a Drawing i did in MS paint (Sorry i don't have any Modeling software installed on this PC)
 
The Filler Assembly Is attached to the back of the motor using a zip-tie or something similar. When it melts through, It is released and shot away from the back of the motor.
Here is a picture of one being installed. You can see the zip-ties beign installed, and the 2 Fuel lines.
And then a picture of the Assembly after ignition.
Closeup of it installed
Moments before ignition.
and finally, ignition!
|
|
|
|
|
6:13 am
December 13, 2010
|
rpulkrabek
| | |
| Member | posts 349 | |
|
|
Ok, I see what you are trying to do here. For the actual ignition, is it some speaker wire where a current jumps between wires? Are the wire and power supply not physically connected to the rocket, as in, it will be on the ground at all times?
Are you suggesting GOX because it has a lower ignition temp than N2O? Do you happen to know what these temperatures are?
Before I saw you proposal, I was thinking that we would use NiChrome wire with something like gun powder wrapped around the wire. Putting a current to the wire would heat up the powder for this to ignite, and then for the N20 to be injected and then ignited.
In your diagram, is the N2O supplied through the combustion chamber and through the injector plate? If this is the route we take, we somehow need to design the injector plate so that the fuel line can pass through. How have you accomplished this before?
|
|
|
5:00 pm
December 13, 2010
|
Nick
| | Florida | |
| Member | posts 34 |
|
|
|
Check out http://www.hypertekhybrids.com…..manual.pdf This is what we based our system on. Yes, the oxidizer is filled through the tail end of the rocket, which in my opinion makes the construction simpler. (no need to have ports on the side of the body to fill, would require no access to the tank to fill, You fill moments before ignition- no need to have a live rocket when setting it up on the pad. ect…)
This system uses a simple injector port, that the fillertube seals into. Using an injector plate would complicate this, but it may be able to be adapted. I don't have the numbers right now, but i remember from our research that the GOx would ignite easier using speaker wire hooked up to a transformer which took a car battery and pumped 2300 volts through 24 gauge speaker wire "cut into a V" which arced and burned the insulation of the wire. The wires are taped up the filler tube of the rocket and are left behind at launch. We had 100% success with ignition on all of our test fires.This was used with HTPB, I haven't been able to find any Technical HDPE hybrid rocket data, mostly just homemade systems.
|
|
|
|
|
9:26 am
March 9, 2011
|
psandee
| | |
| New Member | posts 2 | |
|
|
can any one help me with the IGNITER for NOX/ PARAFFIN WAX system ……….. as the combustion temperature is high for NOX it takes time to get combusted upon injecting through the injector at high pressures but the igniter has to withstand the pressure of the flow without blowing out therough the nozzle. if we use nicrome wire and some combustible material we have to arrest them in the precombustion chamber without letting them blowing them out and one more thing we have to consider is that the if the combustible material should be wrapped in a material which should be completely consumable upon igniting the combustible material……..
|
|
|
4:49 am
March 13, 2011
|
rpulkrabek
| | |
| Member | posts 349 | |
|
|
psandee said:
can any one help me with the IGNITER for NOX/ PARAFFIN WAX system ……….. as the combustion temperature is high for NOX it takes time to get combusted upon injecting through the injector at high pressures but the igniter has to withstand the pressure of the flow without blowing out therough the nozzle. if we use nicrome wire and some combustible material we have to arrest them in the precombustion chamber without letting them blowing them out and one more thing we have to consider is that the if the combustible material should be wrapped in a material which should be completely consumable upon igniting the combustible material……..
Hi, sorry to not have replied to you earlier. The problems you are having with ignition are the same that we are also trying to overcome. I don't have any experience, but I am thinking to flood the combustion chamber with GOx and then use nichrome with some sort of combustable material. The nichrome with the combustable material should then ignite the oxygen, which I hope would ignite the N2O. It needs to be tested, though.
What project are you working on? Do you care to explain what works for you and what doesn't?
|
|
|
5:03 am
March 13, 2011
|
psandee
| | |
| New Member | posts 2 | |
|
|
am curently working on Study Of Hybrid Combustion using Paraffin wax as fuel and Nitrous Oxide (N2O) as oxidizer and my main objective is to find the regression rate at different injection pressures and even the mass consumption rate and the pressure time history and also the thrust and specific impusle .
for doing this i have designed my rocket motor and made paraffin wax fuel grains and designed the nozzle and am using a swirl injector which was already made by my friend and now the left out things are laying up of the feed line and setting up igniter inside the chamber and even finding out the type of igniter ..
what about u ? can u explain on what are you are working ?
|
|
|
7:08 am
March 13, 2011
|
rpulkrabek
| | |
| Member | posts 349 | |
|
|
I/We are working on a N2O and HDPE hybrid rocket. It seems that at the moment I am the only one contributing to this rocket, though. I suspect this to change once more progress comes. I am designing this little by little and plan to refine everything at a later stage. The goal is to just make it to space before we expand and have more difficult tasks. An overall design is shaping up, but there is a lot to do, still. Right now I am trying to determine the injector plate to use. I have done quite many CFD analysis for this. I would also like this to have a swirl flow. I'll reply later with what design I am currently thinking about using. Do you have any pictures of the injector you are using?
Later on, I am going to try and figure out the ignition, the valves to be used (which include how to fill up the oxidizer tank), final dimensions of the rocket needed (heights and diameters of everything), parachutes, nose cone.
We have another team which is working on high altitude weather balloons. They will then perform tests for certain components that will be put in place for this rocket.
This is roughly where the design is at:
|
|
|
8:30 am
March 15, 2011
|
SeanMaguire
| | |
| Member | posts 3 | |
|
|
rpulkrabek said:
We have another team which is working on high altitude weather balloons. They will then perform tests for certain components that will be put in place for this rocket.
Do you have any details on this team? And if they have made any progress?
I'm assuming this is the "CloudLab" project?
I can't find anything on the wiki regarding progress on this.
|
|
|
7:48 am
March 16, 2011
|
rpulkrabek
| | |
| Member | posts 349 | |
|
|
SeanMaguire said:
Do you have any details on this team? And if they have made any progress?
I'm assuming this is the "CloudLab" project?
I can't find anything on the wiki regarding progress on this.
Hi, yes this is the Cloudlab Program. I had assumed you were already involved. I have seen that you have updated the wiki a bit. At the moment, brmj is leading the Cloudlab team. The last I heard is that he has a few people he is working with and they have been mostly meeting in IRC. I believe they meet at 5am GMT on Tuesdays. Brmj said he was going to keep us updated on the forum, but I haven't heard of any progress lately. Our wiki and website are a bit outdated. This is something that needs to be fixed.
|
|
|
7:02 am
April 2, 2011
|
spacelaunch
| | |
| Member | posts 6 | |
|
|
Hello guys,
Options for ignition of the hybrids your discussing are.
1/ GOX/ fuel + HV spark as per Hypertek
2/ GOX/ Steel Wool + HV spark
3/ ematch & composite heater grain
4/ HV resistor/ pyrodex ignition
I just want to comment that the NOX/ HDPE direction is
probably the least optimum direction to go if you are attempting to develop a
100km capable rocket. The poor bulk density of Nitrous (around 750kg/m3)
combined with HDPE (around 940kg/m3), and the excessively low regression rate
of the fuel (well under 1mm/sec at useable mass flux levels). Will produce a
very long and thin rocket & require the use of composites to achieve a useable
mass ratio. The low regression rate of the HDPE will lead to a fuel grain of
around 10 to 1 length diameter ratio, or complicated & inefficient
multi-port fuel grains.
I would strongly suggest you stay on the liquefying fuel
path (i.e waxes), in fact check out Polyethylene Waxes. These offer more
consistent melt point specifications at higher temperature than Paraffin wax.
Regression rate data has been published for Marcus 200 wax & Polyflo 200,
and they sit well between HTPB & Paraffin. For the current motor I am
developing I have chosen NOX/Sorbitol, the regression rate is not great but the
bulk density is greatly improved by the fuel (1200kg/m3). Also the mixture
ratio is around 3 to 1, thus reducing the NOX tank size. Adding powdered Al to
the Sorbitol @ 40% brings that ratio down to 2 to 1, plus you can simply heat
and pour your fuel grain into any shape desired.
NOX propulsion is not mass efficient though, case in point I
have designed a version of my rocket running on Hydrogen Peroxide & PE Wax
& it can achieve over 70km, whilst the NOX/ Wax version can only achieve
32km at the same size. Worth considering this if you’re aiming for space.
As for filling your big NOX rocket.
I have looked at this issue and the best way to go is to
chill your fill supply, then allow the NOX to warm up in the flight tank. The
big issue here is that the current systems of filling a tank with a vent hole
leads to massive wastage, which on a large rocket will be costly. It doesn’t
need to be more complicated than higher a mobile (trailer) cold store for the
day & standing your fill tanks in it. Then developing a open loop temp/pressure
system which cycles you fill & vent vales to achieve the desired firing
conditions. I have already sourced the Type – T thermocouples require to
prototype such a system, and would be happy to share results.
|
|
|
3:39 am
April 6, 2011
|
rpulkrabek
| | |
| Member | posts 349 | |
|
|
Hi spacelaunch,
Thanks for your post. It's greatly appreciated. I have to admit, I don't have much experience with rockets. I am working little by little, submitting the design as I go along, gathering feedback and learning a lot along the way. It's been a great exercise, and I truly hope that we can make it to space.
You are not the first person to stress the concerns about HDPE as a fuel. Since you bring it up, though, I think that we should really reconsider our choice. The decision came from a poll on the blog. The reason HDPE was chosen was due to it's ease to obtain. Now I am not sure. You mentioned elsewhere that HTPB was on the ITAR list. This then seems like it's not a good choice for us, as we want to be open and global. What can you say about paraffin? Also, this PE wax you mentioned is intriguing. How easy is it to acquire? Does it need to be casted?
I feel that we should still stay with N2O as opposed to something like LOX. It just seems safer and easier. One of our key design criteria is that we make things as easy as possible, off the shelf components.
|
|
Login 
Register 
Search 
Home
Topic RSS 
