K@meleon

Hi there, As an engineering student I have to design an environmentally friendly aircraft with a few fellow students. We where fiddling around with the problems related to the use of pressurized/cryogenic hydrogen when we stumbled accross Hydrogen Peroxide. It seemed interesting being non toxic, stable, cheap, liquid at room temperature, and releasing only water and hydrogen when burnt. But the problem is that it's quite difficult to find accurate information about the use of [math]H_2O_2 [/math] as a propellant. I know it has been used in rocket engines, after being catalysed into hydrogen and oxygen, but we would like to use it as fuel in a gas turbine. We therefore had a few questions we would like to ask to the chemistry "pros": - Is it possible to burn Hydrogen Peroxide without catalysing it first? - If this is possible, what would be the energy content of Hydrogen Peroxide in KJ/kg? - If we have to catalyse it, what would be the best catalyst, and how expensive is it? - What would then be the energy content of [math] H_2O_2[/math]? In advance thanks for the help you guys can give us!

Yeah, high level waste needs heavy shielding and sometimes even remote handling when manipulated... And a 1000 MWe power plant produces around 30t of it a year.

For as far as I know the French keep it nice and safe on home ground. And the Brits, they dump it in the sea..

Well, all sounds good. I'll have to try. Thanx

Well, they treat their waste in La Hague, vitrify it, and store on site, or sometimes back at their plant sites. They are busy with pilot studies for deep geolgical burying, like in the states. But the process of finding a site, convincing the locals and then testing whether the site is really what they are looking for, is quite a long one. Don't know exactly how far they are, but I think they are up to site testing now.

Did someone actually read this link before making up a theory why it wouldn't work? It worked for petrol engines, why not for a diesel? Perhaps not really the way the original post suggested, but it does improve the combustion for petrol engines. If we manage to improve the combustion of diesel the same way, than we would increase fuel efficiency.. And water is cheap

If you're talking about a Wankel engine, then I don't really agree with that. They do have serious sealing issues with rotary engines. Although they do vibrate a lot less, I'm not sure the seals will keep their tightness on the long run...

How do you mean?

Well, thanks for the tip anyways. Will have to go with Potassium Nitrate then.. Will let you guys know when, and if it works out.

Crap. Just checked. You are absolutely right. The booster use Ammonium perchlorate.. Is ammonium perchlorate less hygroscopic then ammonium nitrate?

Yeah, I'm quite sure. I'm almost certain the boosters of the space shuttle use ammonium nitrate mixed with aluminium powder. Correct me if I'm wrong, but what you are saying is that AN is basically only good for explosives?

Hum.. I'm afraid your subaru (or any conventional car) won't get more efficient if you pull heat rapidly.. The heat you use for your heater comes from the coolant of your engine, mixed through an air exchanger with cool air from outside. The warm coolant just continues after the heat exchanger back to the radiator. So in fact, by pulling the heat out of the coolant going to the radiator, you don't really change much in the process, if you see what I mean. It just allows you to take a bit more heat out than with just the radiator, which only plays a role when the radiator is saturated. And this is hardly the case with normal engines and normal oustide temperatures. The engine coolant itself stays at around 80°C. (Engines do like to run a bit hot) But the trick I just described is sometimes used in rallying (WRC) where the engines are pushed really hard, and the radiators can get a hard time dumping all the heat away by outside temp of 40-50°C. So they sometimes have to put the heating on full blast.. ..with resulting inside car temperatures of 60-70°C.. Poor fellows. For the horse power needed for stable cruise, I'm not really sure anymore. I think you can start with: [math] D=\frac{1}{2} \rho V^2 C_d S [/math] And then, if I'm not mistaken: [math] P = D\cdot V [/math] This neglecting friction drag on the road. As you can see, the power needed is proportional to the velocity cubed.. If I'm very wrong, can somebody correct me? If I'm right, well, you can look up the drag coefficient of your car, and do the maths.

Hi there, Dunno if understood the questions correctly, but I heard that nowadays diesel engines are getting towards the 60% max efficiency a combustion engine can reach. The rest is lost in heat and friction. So yes, theoritically, it's a lot of heat.. I also know that an AC in the summer will "cost" you approximately 5 to 10 hp. So an electric car will just have to provide the extra energy from its batteries/power source. A hybrid is able to use its engine for this goal I guess. At least for the heat of the heating. And maybe plug the compressor of the AC in mixed mode. On the dynamo of the engine with a switch if the car is in "battery" mode. Dunno exactly. But it ougth to be a simple solution.

By desensitized I mean that they mixed it whith some products so that you can't use is as oxidizer or explosive. The oxidizer logo also disappeared from their bags. But they still sell it under the very same name. Is the use of calcium carbonate and magnesium carbonate enough to reach that goal, or is there more to it? How hygroscopic is very hygroscopic? Say if I make my mixture and keep it dry (in the garage) to use the same day, is it already too much? I once read that it is was possible to make some sort of rocket fuel with a mix of ammonium nitrate and alcohol if I remember correctly. (Never went further then reading the recipe as I never found the correct stuff ) But they said it would make some sort of paste which would harden afterwards. (Spares me from the danger of packing everything in a tube with the risks associated.. ) But you guys are saying I'm better off with something else. Anything as easy as what I described?

Hi there, I couldn't find anything about ammonium nitrate in the pyrotechnic thread, so decided to make a new thread. I'm trying to make a small rocket engine using ammonium nitrate as fuel (easy to use, stable but powerful), but the problem is that I can only find desensitized ammonium nitrate.. Does somebody know how I could resensitize it? Thanx

Well, the point is, to have cheap fuel cells, you need a lot of precision engineering. Currently the american fuel cells cost around 90$ per kilo, and require 99% pure hydrogen, expensive to make. The state of the art japanese fuel cells cost around 9$ per kilo (approximately the same as a combustion engine) and only need a 97% hydrogen which is much cheaper to produce too.. Using a gas turbine to produce electricity in a car would only be interesting if you could use it with hydrogen. But the turbines have some temperature issues related to hydrogen combustion that dont allow them to reach the fuel cell total efficiency yet. However size is not a problem since the power to weight ratio of a gas turbine is low. Complexity neither. In the Netherlands for instance, the next generation central heatings will have small gas turbines incorporated to make use of the wasted heat to produce electricity.

The canadians built a new "high speed" train recently using a P&W turbine that could deliver 10,000 BHP they said. Had it boxed in noise absorbing materials to keep it quiet. http://www.bombardier.com/index.jsp?id=1_0〈=en&file=/en/1_0/1_0.jsp

I think the explanation of Rocketman is quite right. I heard from many people working with the stuff that they didn't really consider hydrogen to be explosive, but more highly flamable. It is like the news reports during the Challenger accident with some reporters claming they heard a big explosion. But the truth is that there was no explosion. It consummed. The boosters were still intact for instance. To come back to the car problem, engineers are considering different alternatives to store hydrogen. I had a lecture by people believing that the most practical way of storage was pressurized hydrogen at 700 bar. They had interesting video footages comparing what would happen if the hydrogen tank and a petrol tank caught fire. The hydrogen tank had a fire plume reaching a few meters upwards, which last a few seconds, without damage to the car. In contrast, the conventional car exploded within two minutes.. It seemed quite convincing to me...

Well, I tried for a cylinder in a flow so far, and got the right answer. It's supposed to be a cylinder of length 1, and radius R. I had: [math] C_p = 2 sin^2(\alpha) [/math] [math] C_n=\frac{1}{c} \cdot \int_0^c C_p \: dr [/math] with c = 2R (the frontal surface of the cylinder, seen by the airflow) [math] C_d = C_n \cdot sin(\alpha) [/math] [math] \Rightarrow C_d=\frac{1}{2R} \cdot \int_0^{\pi} 2sin^2(\alpha)\cdot sin(\alpha)\cdot R \cdot d\alpha [/math] Which, after integration by parts etc etc yields: [math] C_d = \frac{4}{3} [/math] The point is: I'm not sure I did it the right way, I just got the right answer.. For the sphere I started the same way, but with [math] c = \pi R^2 [/math]. I put the theory in attachement for clarity, the example they use is for a flat plate.. Hope it will help.. Thanx again. Newton.zip Newton2.zip

Well, I'm supposed to compute the drag coefficient of a sphere in a hypersonic newtonian flow. In a newtonian flow the pressure coefficient is given by: [math]C_p = sin(\alpha)[/math], with alpha the angle of attack. The pressure coefficient on the lee side is 0. Now. My problem is that I have to compute the total drag coefficient, integrating a surface integral over half a sphere. The final drag coefficient is supposed to be 1, but I just can't get it right , and my calculus book is a good 1000km away... Could someone help me out? Thanx a lot!