Carbon fiber nanotubes.. Thoughts?

[ricecrispi]

http://www.mixedpower.com/modules.ph...rticle&sid=724
230mpg. Now that is a number to brag about. How many people can say they can get 230 mpg. Now that's 1337
BLitz modded a prius with a turbo setup that gets 200 hp.

$25K car, get govermnt rebate, spend it on the turbo, save money on gas and you have good commuter with enough power. Modify it for even more MPG for additional $3k and you would save enough money on gas ( lets consider the fact gas will go up i price) in 2-3 years to pay off that $3k investment

I don't even know why 250 hp or more is required for street driving? When does anyone need that type acceleration or even use it?

[bobo5195]

Plug in hybrids are good, they have advantages but they do reduce MPG on highways, if not precharged like you suggesting (y you even need to use the gasoline engine when you have a truck full of batteries is anyones guess, but its nice to have it there if needed). 250mpg is like 200 miles of pure elctirc then a IC on 50 miles or something.

You can get knock with diesels as well, and even special fuels if you have a full adiabatic cylinders by definition the walls are combustion temprature. Even for wankels. Plus you cant get metals to go that high a temprature so it doesnt matter.

Ultimately you have to move to something like hydrogen and the question then is if you use IC or electric/ fuel cells. Your standard IC engine can get very close to current fuel cells and probably allow high perfromance as well if wanted.

[maxSaleen]

IC engine? Could you elaborate bobo? Never heard of one before.

Sweet link, rice.

[ricecrispi]

full adiabatic cylinde doesn't exist in the real world. If it did the walls would not absorb any heat and heat would all go out with the expansion gas and out the exhaust and burn the bumper.

I understand what you are saying though as the walls would get too hot and detonation would occur if these walls weren't watercooled and that is why they failed.

Anyways, when in kindergarden they said electric cars would be around 2000 and they are still working on it because we got into the SUV craze.

[ricecrispi]

internal combustion?

[maxSaleen]

That's what I was thinking, but it doesn't make sense in his context. How could one use hydrogen with an internal combustion engine? I've seen the reverse process done. Hydrogen gas is superheated outside of an engine (usually by focusing sun light) outside of an engine and then allowed to flow through the engine producing energy (turning crankshaft through altenator). Saw that in PopSci about a year ago.

[maxSaleen]

However, thats in one plane only, and in the other plane I remember it was like sub 100.
Even with Cathar's focused cooling direction in the last couple of years, it is still the case we need to flow heat in both directions?

I had to respond to this. Hasn't Cathar been more focused with the flow of the heat in the water (recirculation) rather than through the heatsink. I think I recall someone saying that the reason only the area above the die is effective for cooling is that heat (like any form of energy) tries to travel in straight lines (directly "up" if you will to the coolant) rather then spread "out". Would this not make CFNs ideal?

[bobo5195]

You can use hydrogen instead of gasoline, same block design and a few keystrokes most modern engines will take it albiet no so efficently.

Only commerically available hydrogen powered car is a BMW V12 with two filling stations one at munich airport and one in munich.

[maxSaleen]

Yeah, I remember BMW bragging about that one. Based on a 7 series (e63) right? I thought they said the thing could do 150+ mph?

[bobo5195]

yes one of docs was involved in it. 7 seris v12. Probably as fast as the gasoline version.

Its a reason why hdrogen fuel cells might not be the way to go that bmw is 95% as efficant as fuel cell car. A fuel cell car would not get up to those kind of speeds. The only thing coming out of the back end is water as well. The one thing is use lose alot of boot space to the hydrogen fuel tank.

[bobkoure]

Hmmm... where to start...?
First, in a diesel engine (and to a lesser extent non diesel IC) the fuel/air mixture that's combusting is typically surrounded by just air. If you were going to go in the adiabatic direction, you'd have to design your combustion chamber to reduce turbulence so as to have essentially an "air jacket" around the combustion process. Have a look at the way ported 2 stroke engines control gas flow.

The reason to (at least attempt to) go with a fuel cell over a hydrogen-driven IC is to reduce NOX. I'd be surprised if the exhaust from that BMW was much if any cleaner than that of a comparable, fuel injected, catalytic cleaned, gas powered model - particularly if you include the pollution produced to produce the fuel to drive the two vehicles the same distance. Maybe we'll get to cheap clean hydrogen, but it doesn't seem to be either yet. The only places in the world where electrolysis looks to be a viable option are places with lots of excess hydropower - like New Zealand - and they currently export most of their excess hydropower as aluminum (primary component being electricity to smelt bauxite).

Finally, just slapping a turbo on a Prius doesn't seem like a good idea at all. That's a modified miller cycle engine in there. So you replace the pistons and cams (and maybe shim the deck) - you've still got an engine that's turned on and off a lot and the engine management is not expecting to have to deal with the additional gas inertia involved with a turbo.

Back to carbon nanotubes...

[superart]

From what I understand, most H2 is obtained from natural gas.

And a lot of natural gas is a byproduct of oil drilling, but most oil rigs just burn the shit off (that long tower on oil rigs that has a flame going all the time). Why dont they save it instead of burning it off?

[csimon]

Originally Posted by superart

From what I understand, most H2 is obtained from natural gas.

And a lot of natural gas is a byproduct of oil drilling, but most oil rigs just burn the shit off (that long tower on oil rigs that has a flame going all the time). Why dont they save it instead of burning it off?

they do ...gas is the last part of the well to be taken ...it produces pressure so that the oil flows from the well. Once the oil flow isn't worth the trouble anymore then they produce the gas usually.

I imagine the H2 you are referring to in drilling is the H2S? That is a very corrosive and extremely poisonous gas. Smells like rotten eggs.

[superart]

Originally Posted by csimon

they do ...gas is the last part of the well to be taken ...it produces pressure so that the oil flows from the well. Once the oil flow isn't worth the trouble anymore then they produce the gas usually.

I imagine the H2 you are referring to in drilling is the H2S? That is a very corrosive and extremely poisonous gas. Smells like rotten eggs.

I always thought they got H2 from ether propane or methane.


If they do take the gas from the well, then what is the stuff being burnt off at these towers?

[csimon]

Well H2S is burned off because it's useless and noxious and corrosive ...some small amounts natural gas are burned to test quality. The bluer the flame the cleaner the gas.

There are 1-4 carbons in gas and 5-60+ in crude ...both made up of hydrocarbons.

[superart]

ahh, ok, thanks for clearing tht up for me.

[bobo5195]

Originally Posted by bobkoure

Hmmm... where to start...?
First, in a diesel engine (and to a lesser extent non diesel IC) the fuel/air mixture that's combusting is typically surrounded by just air. If you were going to go in the adiabatic direction, you'd have to design your combustion chamber to reduce turbulence so as to have essentially an "air jacket" around the combustion process. Have a look at the way ported 2 stroke engines control gas flow.

The reason to (at least attempt to) go with a fuel cell over a hydrogen-driven IC is to reduce NOX. I'd be surprised if the exhaust from that BMW was much if any cleaner than that of a comparable, fuel injected, catalytic cleaned, gas powered model - particularly if you include the pollution produced to produce the fuel to drive the two vehicles the same distance. Maybe we'll get to cheap clean hydrogen, but it doesn't seem to be either yet. The only places in the world where electrolysis looks to be a viable option are places with lots of excess hydropower - like New Zealand - and they currently export most of their excess hydropower as aluminum (primary component being electricity to smelt bauxite).

Finally, just slapping a turbo on a Prius doesn't seem like a good idea at all. That's a modified miller cycle engine in there. So you replace the pistons and cams (and maybe shim the deck) - you've still got an engine that's turned on and off a lot and the engine management is not expecting to have to deal with the additional gas inertia involved with a turbo.

Back to carbon nanotubes...

I assume your talking about stratified (areas of fuel surrounded by air) engines (not commonly used as there are problems with NOx, most modern (SI - spark ignition) engines don’t work like this (although a lot of older ones claim too)

Increasing turbulence is an engine design goal. Engines contain some of the most turbulent flows that you will ever find. The reason is your typical flame has a combustion speed of 0.6m/s (ideal speed) however this is not fast enough to allow good combustion (7000rpm do the math on cylinder sizes). To increase this engine designers increase turbulence and use swirl (rotating air caused by opening one valve more than the other, which is why two inlet valves are common) and tumble (air falling over it self to get in to the engine). Creating an air jacket in a situation like this is near enough impossible, you’ve got a flame moving at 3m/s its going to fill a cylinder. Also by your reasoning your going to need a thick thermal boundary layer about the cylinder head which is not going to happen.

Your right about NOx but you have to consider that fuel cell bi products (the catalyst) are nasty stuff as well and that hydrogen powered IC is more efficient (if I’m reading things right twice as efficient, due to higher energy density of hydrogen and faster flame speed). Also replacing although electric motors and servicing them is a big hassle.

If your going to industrially make hydrogen you use a shift reactor, basically you burn (heat a lot more like) hydrocarbons in little air to produce carbon monoxide this can then be reacted with water to make carbon dioxide and hydrogen. This produces a little power as well so you can do it for power plants. This is a current plan with clean coal technologies which burn coal this way and then burn the hydrogen. The CO2 can then be disposed if you want by basically piping it underground (into old oil fields) meaning you’ve got zero emission oil.

Nanotubes arent commericalised yet, personally im still waiting for space stations i can visit that spin.

[maxSaleen]

Agree with the turbulance part. That's one of the greatest challenges in designing engines. As compression increases, laminar flow increases and the fuel mixutre gets pushed to the sides of the cylinder, reducing the effectiveness of the combustion (so one of my professors told me). The increase in laminar flow and the "de-centralization" of the liquid is an exponential function, meaning that at typical engine pressure (10 atm I believe) laminar flow is very high. The only way to overcome this is by inducing a turbulant air flow inside the cylinder.

Cool bit about the shift reactor. How much hydrogen can it pump out (per pound of coal perhaps)? Last time I checked, we have plenty of coal here in the U.S.

[bobkoure]

Originally Posted by bobo5195

I assume your talking about stratified (areas of fuel surrounded by air) engines (not commonly used as there are problems with NOx, most modern (SI - spark ignition) engines don’t work like this (although a lot of older ones claim too)

Actually I was talking about diesel engines as (AFAIK) SI becomes problematic when your cylinder head is hot enough to produce premature combustion. Yes, NOX is still a problem (I'd imagine it would be a bigger problem). And I was more thinking along the lines of turning poor scavenging into a "feature" - so really unscavenged exhaust with a pocket of air, into which a bit of fuel gets squirted.

Increasing turbulence is an engine design goal. Engines contain some of the most turbulent flows that you will ever find.

Yup. Actually know a bit about this (probably 'way outdated, though). However to move to something like adibiatic (or near adibiatic) IMHO all the "rules of thumb" (things like flow management, combustion area, head shape, rod length ratio) IMHO go out the window.

The reason is your typical flame has a combustion speed of 0.6m/s (ideal speed) however this is not fast enough to allow good combustion (7000rpm do the math on cylinder sizes).

We were at more than double that - the answer at the time was to introduce multiple flame fronts (very rapid series of sparks). Not sure why that didn't catch on...? At the time CDI was exotic, but certainly it isn't now.

To increase this engine designers increase turbulence and use swirl

Don't forget squish.
The point is that adibiatic shouldn't be approached as current technology with a few parameters tweaked.
IMHO a lot of IC technology has been developed through racing - but racing isn't just one technology - and it gets steered the racing rules in effect. For instance, at one point in IC evolution, there was a turn from slow revving, lightly built large displacement engines to more heavily built, faster revving ones. From my reading (not old enough to have been there) the race cars with that lighter-built design lost a major race through petcock failure - and there was a strong suspicion of sabotage. Anyway, at that early point, a simple lost race or two might be enough to turn development in a different direction. Now we have displacement rules, which tends to drive faster revving engines
Maybe it's time to try that "other branch in the tree". ...and maybe it's time to chase something other than the sterling cycle. Maybe fuel cells - and maybe something else. External combustion reciprocating has advantages in the air pollution area and has a useful-for-daily-driving torque curve. Then there's turbines, which other than a short drive in a GM prototype in '64 I have no experience with. The problem at the time was the transmission (manufacturing costs)... They probably sucked at fuel economy, threw lots of hydrocarbons out the tailpipe, and likely were bad in other ways that nobody knew/cared much about then

Shift reactors... hmmm... interesting - clearly I've been out of that loop for 'way too long (dropped ICs for PCs in the early '80s, combination of having lost a couple of good friends on the track and having fun cobbling together electronics for engine management systems - laughably crude in retrospect.) And ya have to wonder if this same reaction (as well as lower temps) might be a factor in water injection reducing NOX. Did a bit with it, until the rules changed and it was "cheating". At the time we were after the greater "push" from water vapor expanding - and we could run higher compression ratios without detonation - and without using "illegal" fuel (rules again). And we didn't care about NOX.

Space stations? I want to visit some other planets.

[bobo5195]

Diesels are going to have the same thing, just it has to be hotter at the end of the day pressure and temperature are independent. Modern engines may already recirculate exhaust into order to help catalytic converters which don’t like oxygen.

Probably its just easier to sate my rather limited knowledge, im a mech eng student undergrad (its different in the uk im master level in comparison to the USA) and one of my courses happens to be in SI (otto is the word I use not sterling, I take sterling to refer to sterling engines which are heat pumps in a way). This course is taken by a doc who designs engines or some part for Honda and what he does for an hour each week is tell us how to design engines well. I’ve also read John Lumneys book and introduction to engines twice (nice book). The course notes wer originally written by a guy called Prof Langford who is apparently a god of engine design., he may (if ive not got him confused with some one) invented modern superchargers. Next term I get a doc who runs probably the top turbocharging testing rig in the world teaching me about turbochargers (he apparently doesn’t like dumpvalves so we might make some funny noises).

Based on what my lecturer syas most of the stuff from the 80s in terms of fluid dynamics is completely wrong CFD analysis showed that other things were going wrong although the correlations are obviously still right as they are based on hard data.

I’m not convinced (and indeed the doc likes banging on about it, including how crap people are at designing a good water pump, which uses up some of his hard fought for hp) if you move to adiabatic that everything goes out the window if a spark or pressure (I use pressure to emphasize that compression and gas temperature are dependent). And even if It could theoretically be done practical issues still dominate i.e. you cant make it.

I think multiple flame fronts still exist in some engines Lumley has an example of one with a single top spark plugs and 3 around the edge. I think given current turbulence advances they are not needed in comparison to the problems that they create. I accept flame speed I think it is about 1.2m/s for your average engine but I think recently its going up.

Squish = tumble which I didn’t mention besides you cant have swirl without tumble Lumley says that tumble is 16 x more effective than swirl, this is one of the things CFD proved I believe.

A lot of old engine design was guesswork with no real science some old engine designs from the 1910s would not look out of place to some engines now (DOHC penta head, 4 valve) if they were tuned a bit. The old preference to longer strokes was ultimately a fallacy as shorter ones are better but I believe that some fiats one with a long stroke engine and everyone followed that for 20 years. IF it wasn’t for piston rign requirements we would all probably be running f1 or higher bore to stroke ratios as these are thermodynamically better.

The chain in increasing speed was probably a result of increasing power requirements a lot of countries brought taxes in based on engine volume and related characteristics. As I mentioned above high bore/stroke is better for thermodynamic reasons. The reasons for this were based on hard science I believe.

Other types are always on the go one of my docs has suggest a gas turbine I imagine it would be quite easy to do if we move to hydrogen or LPG. Gearing losses are still there but gas turbine tech is getting better. The problem is NOx is bad from a gas turbines (hippies who fly around are far worse than boy racers for air pollution). External combustion is one way as you point out but you have to accept big efficiency problems. Ultimately these days hitting the performance is easy, hitting the pollution controls is not. The doc who’s currently teaching us engines is really against fuel cells and hybrids from good arguments, one of the others teaching the course is actively working on developing them.

The new power plant designs is one of my other docs things. Basically for 25% more energy costs you can get CO2 free electrical power from fossil fuels the extra cost comes from the fact that the plant is less efficient (37-40% vs 55% for a modern coal plant vs 80% for ultra modern combined cycle gas plant) and they cost twice as much as a standard coal plant. There are already working plants and it is proven technology. If there was political will and it was implemented you could meet Kyoto fairly easily. The reason this tech is being developed part from lack of good renewables and public dislike of nuclear is china has a lot of coal and we need a source of hydrogen if we move to a hydrogen economy.

im guessing my speeling and grammer is going to be wrong in this so sorry in advance.

[Bevel]

Originally Posted by bobkoure

The only places in the world where electrolysis looks to be a viable option are places with lots of excess hydropower - like New Zealand - and they currently export most of their excess hydropower as aluminum (primary component being electricity to smelt bauxite).

As I live in New Zealand I just thought I would let you all know that we do NOT have an excess of hydropower, quite the opposite in fact. For the last few summers we have had power shortages as the hydro lakes got dangerously low.
We do have one aluminum smelter near bluff and this uses power from a hydro power station that was purpose built for the smelter and even they have had to cut production.
Wind power has become the new form of power generation here and power prices are rocketing .

[bobkoure]

Sounds like things have continued to be dry - I was in NZ some few years ago (don't remember the year, but I kept running into the lord of the rings crews in out of the way places as I was on a big trailie - which should date it, sort'a) and it wasvery dry. Pasturage had turned grey. Great weather for bike riding - except for a fairly amazing wind storm that had my footpeg actually touch pavement a couple of times - and me just trying to go in a straight line.

I'd gone on the milford sound tourist "bus ride underground" to the power station the first time I'd been in NZ. There seemed to be lots of hydro power available. Nice westerly wind to bring wet winds from over the ocean, southern alps to scoop the water out of the air. Didn't figure even a drought would interfere with that.

Speaking of bevels (as in bevel gear twins) do you happen to know Martin Cox? He and family currently live in Chch...

[Bevel]

Sorry I have not heard of Martin Cox as I live in Hamilton which is in the north island, but Im sure hes a top bloke.
Yeah I own a 78 900ss Bevel Drive Ducati, I love it to bits. It will never be sold.

The problem with the southern alps is that they cause the rain to fall on there western side and the hydro lakes are on the eastern side along with most of the farm land and they say it will be getting dryer in the future.

I am into solar power with a couple of panels myself and I would like to see alot more use of this technology.

[bobkoure]

I had thought that the lakes feeding the hydro for the alu smelters were on the western side of the alps. I'd also been pretty sure that there were no power transmission lines from there to the NZ "grid" - so using that power to create hydrogen sounded, well, useful.

I've been to/through Hamilton a couple of times, so, yeah, I know it's on N.I. Nice place.

Martin's got a bevel twin as well. I had a bevel single at one point (used it for ice racing), now have a couple of belt drives in the garage, but don't get out nearly as much as I'd like - especially now as the temp's -7C right now, and falling.

[Bevel]

I have been fortunate to ride most rubber band dukes as I worked for the Hamilton Motorcycle Centre for many years. The one I would still give my left nut for was the 888 SP4, I have never ridden such an "angry" bike. It refused to idol, was very loud and quite horrible around town but give it some space and it made sense, super fast. You really had to dominate it otherwise it did what it liked ie try to kill you. I think the devil himself must have built that thing. Completely mental - Damm I want one

Never liked riding in winter either.

My SS