Hydrogen-based Rotary Engine? 349
Seabird99 writes: "I came across this article at one of my car related forums and thought that I'd pass it on here. I have always been intrigued by "alternative" technologies where they relate to artificial locomotion." For some reason Slashdot gets a lot of submissions of wacko energy concepts - power from nothing, power from sand, power from a black box, engines that get 500 miles to the gallon... Perhaps this is more of the same, but at least it's an interesting write-up.
Wacky? (Score:5, Informative)
Here's a little more info [monito.com] if you weant to do some research.
Tom.
Addressed in article (Score:3, Informative)
Re:Next Problem (Score:1, Informative)
You split water into H2 and O2, ignite them, and get water again. Hoorah! But as I said, energy can't be created, so the energy taken to split up the water would never be less than the energy given out by combustion.
As an aside, several prototype cars have been manufactured that do exactly this: they electrolyse the water, and then burn the H2. Presumably they found it gave greater power than electric motors (just my guess) but at the end of the day, the battery still had to be recharged every so often, just like lame electric cars.
Now a nuclear car, *that* would be fun
'Oh yeah, she does 7500 Miles to the plutonium rod...'
Transmission (Score:2, Informative)
Another interesting transmission system, loosely based on similar principles can be found here [torotrack.co.uk]
McMaster Motor site (Score:5, Informative)
Looking at it helps me understand the way it works. I don't know if this will ever come to fruition, but I sure hope it does. Even if it doesn't, he's a revolutionary thinker with a significant record of success, and deserves our praise and respect for that.
Re:Next Problem (Score:2, Informative)
I'm not a chemist, so I don't know how this compares to generating hydrogen and oxygen in terms of efficiency and environmental damage.
Quasi-Turbine (Score:2, Informative)
Hard to compress hydrogen (Score:4, Informative)
Hydrogen, on the other hand, has a boiling point of 20 K at atmospheric pressure (a bone chilling -423 degrees F)! So tanks would need some serious insulation in addition to handling high pressure. Due to its smaller molecules, it also leaks easier than LNG.
The best way to store hydrogen is probably in a hydrogen-rich compound like methanol, which is liquid at ambient conditions. My research group, among many others, is studying ways to efficiently convert methanol to hydrogen + carbon dioxide + water at the point of use. This would allow us to fuel our cars, RV's, or cell phones with convenient methanol and then run hydrogen fuel cells.
Don't worry about the carbon dioxide from that reaction. The methanol would presumably come from biomass or nuclear/solar-powered synthesis that consumes carbon dioxide. The carbon is just a carrier for the hydrogen, and there is no net CO2 pollution.
AlpineR
You can't store enough H2 That way (Score:2, Informative)
Re:Next Problem (Score:3, Informative)
Re:Next Problem (Score:2, Informative)
Re:Next Problem (Score:3, Informative)
A bottle of water doesn't have enough energy present to split it into hydrogen. You can say "yes, if it's at 30,000 feet or 99 degrees C" or whatever, but that bottle of water required EXTERNAL energy to raise it to that potential. And that external energy is the entire point. It had to come from somewhere, it's not free.
Until someone invents a way to "crack" water (with some off-the-wall fusion theory or whatever) there will always be a need for an external energy source to split it. Whether it comes from solar panels on your garage roof or a coal-fired plant in Montana over electric lines doesn't change the fact that EXTERNAL energy was required to make it useful.
John
Re:Several interrelated issues. (Score:2, Informative)
Let's take things one at a time
But it should be noted this isn't anything new. The internal combustion engine is innefficient by nature. It takes a spherical force (an explosion), redirects that into a vector force (up and down in a straight line), redirects that into a circular force, which is redirected into another circular force, finally driving the car. Each of those redirections wastes energy.
Close but not quite. The problem is not with INTERNAL combustion engines in particular. All the engines being discussed here (except for fuel cells) are internal combustion engines. They change chemical energy to mechanical energy by burning their fuel directly. This is as opposed to EXTERNAL combustion engines which burn their fuel and use it to heat a working fluid usually steam which then is converted to mechanical energy by a thermodynamic process usually expansion of the heated working fluid against a piston. Steam engines are the usual example.
What makes the rotary concept interesting to engineers is the fact that the piston never has to change the direction of acceleration as much as it does in reciprocating engines. All else being equal: displacement, fuel, materials, etc. the way to get more power out of an engine is to make it turn faster. Because the pistons in reciprocating engines have to change their direction by 180 degrees at the top and bottom of a stroke there are mechanical limits on how high they can rev. Using exotic materials and small displacements Formula 1 engines can rev to about 18000rpm. The limits to revving these engines are actually the valves, but this technology would make a poor engine for a street car because the small displacement which is necessary to reduce the piston mass as well as being a result of F1 rules makes for very little torque at low revs. Think Honda S2000 (9000rpm redline 2.4 liter) versus Corvette (6500rpm redline 5.3 liter).
Anyway that's whats troubling about McMaster's claims. He says he can get rid of the transmission which is what allows you to rev the engine to a useful point in the power band at low speeds. So his rotary must produce a lot of torque which is not usually a characteristic of automotive rotaries, again compare the high revving but relatively slow off the line RX-7 to the big Detroit iron Vettes, Vipers and Mustangs.
Moreover, the fact that you have carbon monoxide and other hydrocarbon emissions is a sign of innefficient combustion: complete combustion of a carbon molecule goes all the way to carbon dioxide.
No, because of entropy combustion processes will produce a wide spectrum of byproducts. The more complex the thing you burn the more complex your end results. You can tune the spectrum, which is what most ULEV engines do, by carefully controlling the amount of fuel and temperature of combustion but you can never eliminate all byproducts. Hydrogen and oxygen combine to water alone only because hydroxide is unstable at the temperatures and pressures engines operate at, unlike carbon monoxide, and therefore if you add extra hydorgen the hydroxide will favourably combine into water too. Hydrogen burning internal combustion engines will also necessarily produce NHx and NOx (Nitrogen Hydrogen and Nitrogen Oxygen) compounds if they are obtaining their oxidant from the atmosphere but again thanks to favourable conditions we can limit the production of these by carefully controlling the temperature of combustion. Maybe that's why McMaster wants to use an oxygen cannister, that way he doesn't have to worry about nitrogen in his reaction.
The other technology discussed here is photovoltaic (solar-electric) conversion of water to hydrogen for combustion. I think this is far more theoretical. Not that you can't very simply and reliably bang an electric current through water and get combustible hydrogen and oxygen. But from what I know (and I do have some knowledge on this subject) I seriously doubt whether existing photovoltaic cells are efficient enough to supply the power for even a very efficient automotive engine by splitting water. It should be noted that like anything else, this conversion of electrical power into chemical power represents a loss of efficiency, so the purpose for doing this is to get the benefit of a combustible fuel.
This may be inefficient but you can localize the inefficiency and optimise for it since electrolysis doesn't have to be done at the car. Although that raises the problems of hydrogen storage due to the low density of hydrogen. We already do this with refining plants for gasoline and other petroleum based products.
Re:Hard to compress hydrogen (Score:3, Informative)
A properly designed hydrogen=powered engine would be able to burn slightly "dirty" fuel - such as hydrogen containing a few percent methane.
Adding methane "gels" the hydrogen at low temperature, making it easier to liquefy, store and transport.
This mixture woud still have the advantage of having vapors that are lighter than air, and thus rise in the event of a spill, rather than pooling in low spots and creating an explosion hazard.
Most leaks in a tank come from the seals and joints of the tank, but hydrogen leaks mainly by diffuing throught the tank walls. At high temperatures, this is significant, but at low (~50K) temps, it's hardly a show-stopper.
I'm not bashing carbon-based fuels, just pointing out that there are many alternatives we should pursue in the quest for clean energy.
Re:Read the article before commenting... (Score:2, Informative)
Burning pure hydrogen/oxygen will allow much high combustion temperatures without NOx production and will produce more power (no N2 to dilute the combustion process), but it is not clear that carrying the oxygen along is worthwhile. The mass of the O2 would be eight times greater than that of the necessary H2.
Re:500mpg engines (Score:2, Informative)
The math for fuel economy is as follows: other than pure hydrogen, methane (CH4)(you know, natural gas -- most qty's derived from "dead dino dinner" aka antediluvian vegetation) at around 22,000 btu lb. LHV ["low heating value"], gasolines come in at about 20,500 btu/lb, diesel and jet fuels about 18,800 or so. [IIRC without the book in front of me.]
Using gasoline as the example fuel, you get about 6-1/2 lbs per gallon, or about 130K BTU. 1 HP = 2547 btu, so 135K/2547 equals about 50hp per gallon used per hour. Now then, my little subcompact gets about 35 mpg at that speed on the freeway, at around 12 hp in cruise gear. This particualr engine was rated about 25% thermally efficient under lab conditions. So even if my little car could get a 100% efficient engine (not possible in the real world), the max would be about 140 mpg.
Now then, pure hyrogen is pound for pound about three times more powerful as a fuel, but by the time you get the storage problems resolved, so far you've either added so much weight or drag, you've negated the fuel advantage.
Of course, if we were all flying around in low-drag H2 powered and lifted personal airships -- the weight component would go away. ;-)
Finally, as has been noted in comments posted to other threads, H2 isn't an easy commodity to come by -- don't forget that 2000 sq. ft of solar panels will cost about the same as a medium size new car, or enough to buy fuel for my little car and a 35 mile round trip for somewhere around the next 20 years...
animations (Score:1, Informative)
hydrogen much maligned and misunderstood (Score:3, Informative)
Indeed, your statement:
Hydrogen gas just doesn't pack as much punch, specatcular disasters caught on tape notwithstanding, as gasoline
catches a part of this truth, though more in passing, namely that a tank of hydrogen is less explosive than a tank of gasoline. Meaning, as you say, that there is less energy / volume in hydrogen gas than there is in petroleum liquid (gasoline). Two approaches to this problem are, as implied in this article and the designer's web page, a more effecient engine or, alternatively, an innovative use of chemistry to allow a hydrogen-rich compound to exist as a more dense liquid/solid at room temperature without binding the hydrogen so tightly as to make it useless as a source of energy.
Hydrogen is safer to store, transport, and use than gasoline, by virtue of the very fact that it packs less energy per unit than gasoline. Safety fears are really just that, fears, based on a widely debunked perception that dramatic explosions such as the hindenberg were a result of hydrogen, when in fact it was a result of painting the damn ship with a compound now used as rocket fuel, a compound much more combustible than hydrogen by orders of magnitude. That debunking aside, there remains the perception that hydrogen is this dangerously explosive gas, when in fact it burns too slowly to even explode with the same intensity that a 1972 Ford Pinto's gas tank would when rear-ended.
Not the same! (Score:1, Informative)
Explanation of engine... (Score:3, Informative)
I have to admit, the fascinating thing is the fact that it is so simple - so simple that it looks like it could almost be homebrewed in a garage, provided the builder has sufficient machining skills and tools (ie, a metal lathe and mill would be an absolute necessity, as well as a wire-feed welder, among other tools).
Anyway, here is my explanation:
1. The engine is composed primarily of 6 parts: A shaft (1) which is fitted through a sphere (2) and two opposing, on either sides of the sphere, conical ends (3,4), a metal vane (5) which is slotted between the cones, and thus doesn't move - parallel to the shaft/sphere assembly, and perpendicular to the metal vane. Finally, there is the wobbly plate (6), which is fitted around the sphere, and has flattened ends that are up against the metal vane. This plate bisects the sphere, forming two independent combustion chambers. However, it is not attached to the sphere, it does not rotate, and it is not attached to the vane. It merely "slides" against these parts.
2. Now, imagine the metal vane lying at an angle. At the point where one end is touching the cone, and the vane, there is a fuel inlet and a glow plug. Fuel is admitted, and the glow-plug ignites the fuel.
3. As the fuel combusts, it expands, pushing against the plate and the vane, as it races around the chamber, which looks like a expanding wrapped wedge around the sphere. This expansion causes the plate the nutate (wobble) - but not rotate - around ("around" is not a good word, as it implies that the plate is rotating - I must stress that it does not rotate) the sphere. This opens up the chamber, and as the plate slides around the sphere (*), it rotates the sphere 180 degrees, which is connected to the shaft, which turns the shaft 180 degrees.
4. Once the combustion is started, of course the fuel inlet is closed. When the combustion is completed, the plate is now lying at the opposite angle. An exhaust port is opened (I would imagine the opening and closing of exhaust and inlet ports to be accomplished by solenoid valves of some sort), and the inlet port on the other side is opened to cause the other side to fire, to rotate the shaft 180 degrees more, while simultaneously pushing the exhaust out (by action of the plate) on the opposite side.
5. The cycle repeats.
(*) - Notice how many parts are sliding against each other? I can't understand how this thing is supposed to run dry - ie, no lubricant - unless the fuel is to provide the lubrication of some sort. All that friction will get it damn hot if it isn't lubricated and cooled in some manner.
Furthermore, I am not certain how the plate, rubbing up and acting on the sphere (nutating "around") spins the sphere, unless is it by some strange vector motions being imparted by friction.
The interesting thing about this, though - is if that is the case, if the motor shaft is somehow stalled for whatever reason, the engine shouldn't die - it should only become hotter than normal, which may or may not be a good feature.
---
I hope this explanation helps - I hope it is right, I am pretty certain it is. Please discuss below, and comment on it - I would be pleased to know what others think...
From the Website ... (Score:2, Informative)
The McMaster Motor website [mcmastermotor.com], describes the engine running on nitrous oxide and ammonia (essentially hydrogen and oxygen, with a bit of nitrogen thrown in to make things easier and safer to handle = 3 N20 + 2 NH3 = 3 H20 + 4 N2 + kaboom ).
Added bonus: Nice little animations to show how the combustion system works.