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Post by Johansson on Dec 17, 2010 5:51:26 GMT -5
Is there a way of estimating the N2O consumtion at 500N or roughly 100lbs thrust?
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Post by ernie wrenn on Dec 17, 2010 9:08:40 GMT -5
It takes 275 pounds of nitrous per hour to produce 100 h/p given a ratio of approx 2/1 then 275 lbs/per hour should yield approx 50 lbs thrust .
Methanol requires 100 lbs per hour
gas is 52 pounds per hour per 100 hp
These figures are based on a internal combustion engine.
ernie
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Post by racket on Dec 17, 2010 19:54:14 GMT -5
Hi Anders
If it was going to take 2.3 lbs/sec to make 500 lbs , lets work on half a pound per second total flow for your hundred pounder , probably better to work in flows per minute to save using small fractions , so 30 lbs of fuel and oxidiser per minute , Zucrow, p 468 , has a list of oxidiser/fuel ratios for a large number of different chemicals , but no N20/Ethanol unfortunately , might have to consult another text ...........
OK , N20 IS 36.35% Oxygen and 63.65% good ol' Nitrogen , or roughly 70% more oxygen than air .
Now ethanol can be run at air /fuel ratios of ~8.5 - 10 :1 in an IC engine , but with 70% more oxygen available in the nitros , those A/F ratios would drop to ~5 - 6 :1 when mixed with N2O.
So if you'll be needing say 30 lbs of fuel and oxidiser per minute , then maybe 5 lbs of ethanol and 25 lbs of N20 .
Lets work this backwards , Zacrow gives a O/F ratio of 1.5 :1 for LOX/ethanol , this would equate to 4.5:1 with an oxidiser that only has one third the amount of oxygen as LOX .
The LOX/ethanol example gives combustion pressure of 300 psia , temperature of combustion of 5,250 deg F , and a jet velocity of 7,810 ft/sec
Heh heh , they may be rough numbers , but close enough to get a fire going :-)
Cheers
John
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Post by Johansson on Dec 18, 2010 4:26:17 GMT -5
Great info, now I can estimate the tank sizing.  I sent a mail to AirLiquide to hear what it would cost me to rent a 50 litre N2O bottle and what a filling would cost, renting the bottle one year was 1200 euro and filling it was 10 euro per litre. 10 euro per litre is exactly what a car tuning company charge for filling a nitrous bottle, so there is no idea renting a bottle. Very strange that it wasn´t cheaper. |
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Post by racket on Dec 18, 2010 16:31:04 GMT -5
Hi Anders
50 litres is a BIG bottle and sorta explains the rather high rental cost , it might be cheaper to get 2 smaller bottles with the same 50 litre total capacity .
What capacity bottle are you intending to use on your "vehicle" ??
Been having a bit more of a think on those "numbers" in my last email and aren't "happy" about what your potential temperature of combustion will be and how it will influence efflux velocity .
The LOX/ethanol temp of 5,250F is will 2.5 "units " of mixture ( 1.5 units of LOX and 1 unit of ethanol), but with 4.5 units of N2O and only 1 unit of ethanol to heat the total 5.5 units. one would imagine that temperatures will be substantially lower than the 5,250 deg F of the LOX/ethanol engine
Lower initial temperatures will lower temperature drops across the nozzle for a given pressure ratio as it does with our GTs , its the temperature drop that determines the actual exhaust velocity attained .
You may find that the thrust per unit of N20/ethanol is lower than expected , but if you build for a 100 lbs thrust , any shortfall in thrust will be obvious and could be compensated for to some extent by an increase in combustor pressure but at an increased TSFC (thrust specific fuel consumption)
Interesting times ahead :-)
Cheers
John
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Post by Johansson on Dec 18, 2010 17:11:11 GMT -5
Hi John, The larger 50L bottle was cheaper to rent than several smaller bottles, filling small 10L bottles was much more expensive per litre than filling a 50L bottle but the cost never got cheaper than having a tuning company filling a bottle that I own myself. That way I won´t have to pay the rental, more money for beer to the developers!  What capacity bottle are you intending to use on your "vehicle" ?? We haven´t given that much thought yet, the development engine can use very large tanks since it is stationary and don´t have to empty its tanks after each run. The 2500N engine (if they allow us to race with it) will have to hold enough fuel and oxidizer to take the kick from 100km/h to slightly above 300km/h in one kilometer, total vehicle weight depends on how much Pringles the driver eats (that would be me, no one else says they are stupid enough to ride it...) and how much fuel it would have to carry. I weigh in at 80kg fully dressed in motorcycle wear, the frame and engine probably 30kg more and with the fuel the complete vehicle would perhaps weigh in at 150kg or so. I think that the first tests will be made with self-pressurizing N2O, it would be waaay easier to get a nitrous bottle filled and connected to the test engine than to fill a custom tank from the bottle and use nitrogen to force the nitrous into the engine. The fuel will be pressure fed but for the nitrous a heating blanket should be enough to keep it at a decent pressure, at 20°C the vapour pressure is 50bar and 75 bar seems to be a critical pressure that shouldn´t be exceeded so as long as the bottle is kept warm and cosy we should have all the pressure we need. As you say, very interesting times ahead! Unfortunately we have some higher priority jet projects ahead of us right now but as soon as we can we will start building the test engine. |
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Post by racket on Dec 18, 2010 18:11:10 GMT -5
Hi Anders
LOL...... with 500 lbs of thrust on a 150 kg-330 lb machine and rider , acceleration will be ~48 ft/sec2 - 1.5 G's , after 6 seconds ( neglecting drag) you'd be up to ~293ft/sec - 200mph -320kph , distance 878 feet ~267 metres , another 15 seconds to do the kilometre distance , lets round it off at a max of 30 seconds "fuel" onboard , at 2.3 lbs/sec -~70 lbs -32 kgs allup, maybe 60 lbs -27 kgs of N2O and 12 lbs- 5.5 kgs of ethanol
Cheers
John
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Post by Johansson on Dec 20, 2010 1:25:35 GMT -5
Hi Anders LOL...... with 500 lbs of thrust on a 150 kg-330 lb machine and rider , acceleration will be ~48 ft/sec2 - 1.5 G's , after 6 seconds ( neglecting drag) you'd be up to ~293ft/sec - 200mph -320kph , distance 878 feet ~267 metres , another 15 seconds to do the kilometre distance , lets round it off at a max of 30 seconds "fuel" onboard , at 2.3 lbs/sec -~70 lbs -32 kgs allup, maybe 60 lbs -27 kgs of N2O and 12 lbs- 5.5 kgs of ethanol Cheers John He he, 320km/h after 6 seconds. Sounds like an intresting ride. =) With drag it should still be good for speeds above 300km/h, perhaps a two step launch would be useful with lower thrust until the air resistance starts to slow the acceleration down? The main problem will be to hold on to the handlebars while controlling the engine, at least one button will be needed for engine on/off, one for the brake parachute and one brake lever for each hand connected to brake "pads" at the runners so the kick can be steered. Add 1.5G of acceleration and the result might be a backflip for the driver and a kick heading towards the sky. =) |
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Post by racket on Dec 20, 2010 17:26:40 GMT -5
Hi Anders
Yep , I'd certainly recommend a staged thrust , otherwise it'll be like winding your bike up to redline and dumping the clutch , the kick has a short "wheelbase" like a bike and with a high centre of gravity , not a good combination for fast acceleration rates , LOL, are you allowed under the regulations to fit a "wheelie bar" onto the kick ??
Cheers
John
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Post by Johansson on Dec 21, 2010 1:15:07 GMT -5
Exactly my thought, even with 80kg thrust the front end of our steam rocket kick lifted a little. Imagine what almost 200kg more will do...  There are no regulations for our class, they modify the rules to fit our vehicles so to speak. The downside with that is if the safety guy decides that we cannot race there is nothing to do, if there had been a rule book for the class we could build according to it and no one could complain. |
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Post by stoffe64 on Dec 22, 2010 18:19:27 GMT -5
hello Anders!
very interesting thing that water/steam rocket engine,do you have any drawings of it?, interested to build one myself.
best regards/stephan
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Post by Johansson on Dec 23, 2010 1:16:51 GMT -5
hello Anders! very interesting thing that water/steam rocket engine,do you have any drawings of it?, interested to build one myself. best regards/stephan I have some drawings of the steam nozzle somewhere, but please think twice before making a similar rocket. We did a static test run this summer and found afterwards that the entire side of the bottle had been about to collapse, a large bubble has formed in the thick steel bottle and we were very lucky that it didn´t burst since we were standing only 10-15 meters from it during the test. We learned that day that heating pressure vessles is not the smartest thing to do. |
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Post by stoffe64 on Dec 26, 2010 14:17:04 GMT -5
hello Anders!
hehehe,i have thought twice and third time about it and im still interested in those drawings if you have them ;D
i was really thinking about finding a pressure cylinder made of 316L or better material(thickwalled ofcourse)
thanks for your concern.appreciated and noted and the dangers i have understood about already.
best regards/stephan
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Post by Johansson on Dec 26, 2010 15:03:16 GMT -5
hello Anders! hehehe,i have thought twice and third time about it and im still interested in those drawings if you have them ;D i was really thinking about finding a pressure cylinder made of 316L or better material(thickwalled ofcourse) thanks for your concern.appreciated and noted and the dangers i have understood about already. best regards/stephan Will send you a PM once I get back home from the holiday vacation with the steam nozzle drawings. Cheers! /Anders |
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Post by Johansson on Dec 26, 2010 15:27:28 GMT -5
I am having a discussion with the security chief at the Speed Weekend on Ice crew, and at this point it is not really looking promising for our plans to race a 2500N rocket engine...  Nevertheless we will build the 500N test engine and possibly use it as a booster rocket for our gas turbine kick, all discussions at this point should therefore concern the smaller 500N engine and not the 2500N engine since we suddenly aren´t sure if we will build it. The guidelines at this point are: 1. 500N of thrust 2. Self-pressurizing nitrous oxide (limits the chamber pressure) 3. Aluminum chamber and nozzle (easy manifacturing, cheap) 4. Regeneratively cooled by the alcohol fuel 5. Conical divergent section of the nozzle (easier manifacturing than a bell shaped one) Our goal is to build an engine that can endure longer runs without overheating and eventually be used in a flight vehicle, therefore the need of regenerative cooling instead of water cooling. Turbopumps are out of the question at this point since it would make a relatively straightforward project very advanced, possibly at some later stage when we find that the nitrous vapour pressure is the only thing keeping us from achieving higher thrust but right now it would only add complexity to the project. |
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