Lets take a step from reality. Engine theory and efficiency
Lets take a step from reality. Engine theory and efficiency
(OP)
Hi Guys,
Im trying to come up with a concept by which we way be able to improve engine efficiency to facilitate early rollout of hydrogen fuel.
Ive conducted a load of work on SI Hydrogen/air engines, and would like to explore the potential of using the products of electrolysis (hydrogen and oxygen) in different ways in order to improve engine efficiency and BSFC.
i'm trying to get to the bottom of using pure oxygen with, at this stage, any fuel (gasoline, hydrogen or CNG) as oxidiser. Notwithstanding the increased adiabatic flame temperature (3000 degrees C +), and assuming the materials within the engine can cater for these elevated temperatures, i assume the effect on efficiency would be quite startling. Is this due to the increased temps, more instantaneous burn (constant volume pressure increase), or lack of latent Nitrogen/Co2 normally found in air?
Now given the improved efficiency, we have some limitations, mechanically, other than the temperature. Would the increased oxygen content lead to higher cylinder pressure and faster burn? Or is the flame speed more down to stoichiometry?
Apologise for these musings, but im just playing with the idea of building an engine which has significantly adjusted geometry (CR, Valve Timing, materials, etc) in order to counter the issues that may exist with oxy-fuelled engines. For instance, if using hydrogen, an oxy-hydrogen engine could be operated at ultra lean equivalence to counter the peak cylinder pressure and ignition energy issues.
Any thoughts?
Regards
Steve
Im trying to come up with a concept by which we way be able to improve engine efficiency to facilitate early rollout of hydrogen fuel.
Ive conducted a load of work on SI Hydrogen/air engines, and would like to explore the potential of using the products of electrolysis (hydrogen and oxygen) in different ways in order to improve engine efficiency and BSFC.
i'm trying to get to the bottom of using pure oxygen with, at this stage, any fuel (gasoline, hydrogen or CNG) as oxidiser. Notwithstanding the increased adiabatic flame temperature (3000 degrees C +), and assuming the materials within the engine can cater for these elevated temperatures, i assume the effect on efficiency would be quite startling. Is this due to the increased temps, more instantaneous burn (constant volume pressure increase), or lack of latent Nitrogen/Co2 normally found in air?
Now given the improved efficiency, we have some limitations, mechanically, other than the temperature. Would the increased oxygen content lead to higher cylinder pressure and faster burn? Or is the flame speed more down to stoichiometry?
Apologise for these musings, but im just playing with the idea of building an engine which has significantly adjusted geometry (CR, Valve Timing, materials, etc) in order to counter the issues that may exist with oxy-fuelled engines. For instance, if using hydrogen, an oxy-hydrogen engine could be operated at ultra lean equivalence to counter the peak cylinder pressure and ignition energy issues.
Any thoughts?
Regards
Steve





RE: Lets take a step from reality. Engine theory and efficiency
Let's ignore that for a moment. How would you propose to distribute and store the fuel and oxidizer for your oxy-hydrogen engine? How much of the available space would the storage consume, for a vehicle with practical range?
Mike Halloran
Pembroke Pines, FL, USA
RE: Lets take a step from reality. Engine theory and efficiency
In the late 50's with a Triumph 650 set up for drag racing.
Small O2 bottle and direct injected fuel, various things tried as memory serves...methanol, gasoline, etc. We did not blow ourselves up, but I surely do not know why!!! I guess the fools and motorcycle racers are truly blessed by a higher power...
Rod
RE: Lets take a step from reality. Engine theory and efficiency
Well, you are the one making the claim, you must know the basis for that claim, otherwise it is just wishful thinking.
The most efficient real IC engines on the planet use excess Nitrogen, so it probably ain't that.
CO2 is a trace gas so it ain't that.
There, I've done almost half your research for you.
Are you including the energy required to get the O2 in your efficiency calcs? if not, why not?
Cheers
Greg Locock
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RE: Lets take a step from reality. Engine theory and efficiency
Why would we want to pay for both fuel and oxidiser when we have a very large supply of free oxidiser, or are they now taxing the air we breathe?
Why would we want to carry two tanks full of very dangerous substances?
How do you wish to measure this efficiency? As power density? As distance travelled per unit mass or volume of fuel? As power per unit of displacement? As distance travelled per unit of emissions? At the engine only or as cradle to grave?
If it is HP hours per kg of fuel consumed, then a nuclear submarine might do very well.
Regards
Pat
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RE: Lets take a step from reality. Engine theory and efficiency
EFI system to use it on. As it would counter any combustion improvement.
RE: Lets take a step from reality. Engine theory and efficiency
My point is that the OEMs at this stage all beleive Hydrogen is the fuel of the future. Have done for some time. Yes, they regard FC's as the best means of converting hydrogen to kinetic energy at the wheels, but in the interim, surely the ICE shows some merit as a catalyst for the formation of supporting infrastructure. Germans, americans and Japanese are all avidly following Hydrogen technologies.
Now in a global infrastructure of hydrogen fuel, the primary means of production of hydrogen will be electrolysis. This produces a stoichiometric mixture of hydrogen and oxygen.
I think i know the following - perhaps you can confirm
By increasing the adiabatic flame temperature, the peak thermodynamic efficiency is much higher than that of gasoline/air engines.correct?
By moving from a partially constant volume, partially constant pressure cycle (as is realistic for conventional SI engines) to a purely constant volume process (instantaneous burn) in the combustion phase, thermodynamic efficiency is increased. correct?
Turbocharging improves engine efficiency due to 'recycling' of waste exhaust work - The fact that turbocharged gasoline engines are less efficient is due to the richening of fuel (latent heat capacity benefits of running rich) and retardation of spark to prevent knock. lean burning fuels or high octane fuels are capable of taking better advantage of turbocharging as no additional fuel is required for cooling/knock prevention, and start of combustion/combustion timing is not affected. Correct?
Adding nitrious oxide into an engine works by increasing the oxygen content of air, allowing for the burning of more fuel, thus producing more power. Now i accept the latent heat capacity in vaporisation of N2O has a fair effect on combustion as well, but lets just consider adding oxygen into the air stream or alongside the fuel for stratified charge burning. Surely the net benefit would be increased cylinder pressures which(assuming they stay within the capabilities of the engine)would result in increase efficiency. Correct?
Look forward to your answers.
Steve
RE: Lets take a step from reality. Engine theory and efficiency
Steve
RE: Lets take a step from reality. Engine theory and efficiency
Hydrogen is not a "fuel", it's an energy carrier produced very inefficiently.
Benta.
RE: Lets take a step from reality. Engine theory and efficiency
I am not up on Hydrogen calls but have experimented with electrolysis and I found it requires a lot of energy and is slow.
When we run out of oil we will all be driving cars with nuke reactors on board and a steam engine up front borrowed from designs used in the early 1900s. Since we have not improved much of the design of the engine itself from Otto's design in the 1800s.
Since the engine runs on heat expansion and nothing else. If you raise combustion chamber temp to get more heat, and if you use air, you start burning the Nitrogen which then is a bad for you and requires more junk to clean that up.
Burning the Hydrogen with just the Oxygen produced makes more sense like he is trying to do. Good luck.
RE: Lets take a step from reality. Engine theory and efficiency
Benta - Incorrect. Hydrogen may be called fuel once it is produced. All fuels are produced by some means. Dinosaurs arent fuel, but the hydrocarbons they are now, is. I appreciate the 'energy vector' arguement but in this context, we can focus upon the end use as a CLEAN FUEL.
Dictionary.com definition:
fu·el /ˈfyuəl/ Show Spelled [fyoo-uhl] Show IPA noun, verb, -eled, -el·ing or ( especially British ) -elled, -el·ling.
noun
1. combustible matter used to maintain fire, as coal, wood, oil, or gas, in order to create heat or power.
2. something that gives nourishment; food.
3. an energy source for engines, power plants, or reactors: Kerosene is used as jet engine fuel.
4. something that sustains or encourages; stimulant: Our discussion provided him with fuel for debate.
Hydrogen satisfies all of the above. Where it comes from is not of concern - Every peice of matter has at some point in its life existed as another form. No process is 100% efficient - just because it can be produced and consumed in a very short space of time does not mean it is any different to gasoline, diesel, or for that matter, wood from trees. Please try to focus on the question in hand.
RE: Lets take a step from reality. Engine theory and efficiency
Something to consider.
RE: Lets take a step from reality. Engine theory and efficiency
Let's see...The main topic of discussion in the late 19th Century, as it relates to 'energy', was the 'coal reserves' will be depleted in the next century---How did that work out?
Main petroleum/oil related topic of the 20th Century as I recall was "We will be out of oil by mid 21st Century---How's that look now?
I'm guessing that we will 'never' run out of oil but instead lose the ability to afford the petroleum based products we currently enjoy long before any actual 'oil reserves' are depleted.
Working on alternative fuel sources is admirable. At the present levels of 'oil reserves' and recovery costs...At the present level of engineering expertise in IC engine technology...Tough 'row to hoe', gentlemen. Hard to sell 'fuel' at $100/unit when a much more efficient fuel source can be had for $5/unit...It will surely change, of that I am certain......just not in my lifetime.
Aside: When I was in college and just after the first Sputnik was launched by the USSR, the discussion was about potential fuel for space craft...spaceships. We all thought, in 1959, that we would have 'flying' cars in our garage by 2012.........
Rod
RE: Lets take a step from reality. Engine theory and efficiency
No, not really. So far as I am aware only Honda and BMW are enthusiastic about hydrogen (other companies dabble). Honda use it in their fuel cell cars.
BMW burn hydrogen in an IC engine. It gets reasonable efficiency. Sadly if you leave the car fuelled up for three-ten days all of the hydrogen boils off. http://en.wikipedia.org/wiki/BMW_Hydrogen_7
Hydrogen, from production right through to intake valve, is a very silly fuel for an IC engine, it has so many problems at every stage up until you burn it (it is a very nice fuel chemically) that the only way it gets considered is when very silly politicians are giving money away to crackpot ideas.
Cheers
Greg Locock
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RE: Lets take a step from reality. Engine theory and efficiency
Greg - I disagree.
Gm - Chevy Equinox Fuel Cell SUV
GM - Chevy Volt
Toyota FCV - Fuel Cell SUV
BMW - Hydrogen 7 - V12 HICE
Mazda Premecy RE and RX8 RE - Hydrogen Wankel engines
Mercedes A and B Class FCVs - Fuel Cell
Honda - FCX Clarity, FCX - Fuel Cell Vehicles
VW/Audi - H2/A2 - FCV
Kia - Sportage FCV
Nissan X-Trail FCV
The List of Hydrogen prototypes far surpases this list. EVERY OEM IS LOOKING AT HYDROGEN.
'Hydrogen, from production right through to intake valve, is a very silly fuel for an IC engine, it has so many problems at every stage up until you burn it (it is a very nice fuel chemically) that the only way it gets considered is when very silly politicians are giving money away to crackpot ideas.
'
So are you calling the Germans 'crackpots'? They have invested 2.6billion euro into the rollout of hydrogen infrastructure in germany and are the world leaders in the technology. The one thing you cannot say about the germans is that they are illogical. Production efficiencies WHEN LINKED TO RENEWABLE TECHNOLOGIES has been shown to exceed 75%. Actually the weakest part of the arguement is the efficiency of reconversion - FCs typically operate at around 40% STACK efficiency (without inversion etc) and engines thermodynamically around 20-30% peak. improve reconversion efficiency and the whole arguement, being DEMAND DRIVEN, becomes more valid.
Lets get past the political arguements for a minute.
Assumptions:
Hydrogen fuel and oxygen freely available. and are refuelled onto separate tanks onboard the vehicle.
Are my suppositions correct?
Regards
Steve
RE: Lets take a step from reality. Engine theory and efficiency
Regards
Pat
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RE: Lets take a step from reality. Engine theory and efficiency
- Steve
RE: Lets take a step from reality. Engine theory and efficiency
Despite claims of high efficiency by using RE sources, it's simply not true. These claims always seem to forget about the oil and coal burned to produce the solar panels or build the wind tower? Even today, the only good renewable energy source is hydro-electric. Even then, I don't believe we could find enough rivers to dam.
By my understanding, my first though was that a much hotter fuel burn in an engine would be less efficient. You'd lose more of the combustion heat to the surrounding cooler engine and likely more out the tailpipe. Hopefully, others will tell me if I'm wrong.
RE: Lets take a step from reality. Engine theory and efficiency
Your list is just too easy to refute and your suppositions are so patently on the fringe. Since you appear deaf to some pretty good arguments as posted here...Why waste any further effort.
The bottom line? The IC engine fueled by petroleum based fuel is quite secure for well into the 21st Century (at least). We have NOT peaked on it's development, not even close. The viable alternate energy source has not been discovered.......yet!
Rod
RE: Lets take a step from reality. Engine theory and efficiency
Just two points on the political arguement that can we PLEASE LEAVE THESE BE AND FOCUS ON THE FUNDAMENTAL QUESTIONS????
Lets not be so short sighted as to beleive that the black stuff we dig out of the ground is going to last forever; we're past peak oil, and the stuff that consumes it produces a ridiculous amount of CO2 and noxious gas when burned. Enough solar energy hits the surface of the planet in one day to power the global economy for a year. its just a case of harnessing it.
I have never refuted battery technologies - in fact i am a big fan - but these need to be charged from RE too - and they dont cope as well as electrolyers when coupled to such a varying source.
Likewise i have not refuted the continuation of the engine - hence my questions. I genuinely beleive that there is further development to be had, hence these questions.
Political/feasibility arguement over, and accepting the statement regarding oxygen feeding on the engine components, is there anyone else with experience on this practically?
Looking at the Otto cycle, assuming the same conditions at point 2, surely a higher combustion temperature leads to a higher pressure increase by point 3, thereby greater area (work) even assuming the same rate of isentropic expansion to 4?
I assume an atkinson cycle engines improve efficiency by reducing heat rejection in the exhaust, and closing the pressure difference between points 4 and 1. This being the case, i understand atkinson engines typically sufer poor power density. Would using a fuel wth oxidant (oxygen) surely this may overcome some of these issues?
thanks
steve
RE: Lets take a step from reality. Engine theory and efficiency
Have you ever actually played around with oxygen in a welding shop? Give us a real, honest yes or no answer.
Experiment #1, hook up acetylene and oxygen to a cutting torch, use it to cut through a piece of steel. Yeah, I know we're talking about acetylene instead of hydrogen. Both are extremely energetic and it's not the fuel that does the cutting - it's the oxygen.
Experiment #2, take 3 ordinary balloons. Fill one with oxygen and touch a flame to it. Pop. Fill one with acetylene and touch a flame to it. Woof. Fill one with a roughly 2:1 mix of oxygen and acetylene. Put VERY GOOD earmuffs on and make sure they are tightly sealed against your ears and make sure anyone else in the immediate vicinity does the same. Touch the flame to the balloon.
You might not want to do that experiment in a room that has glass windows.
RE: Lets take a step from reality. Engine theory and efficiency
I predict the OP who has been a member for 3 days and only ever started one hypothetical non engineering work related thread will tell you balloons full of hydrogen are also off limits. If you notice his user ID, this will be the word of god.
I mean we have already been warned if we disagree we will be branded narrow minded (the catch cry of all whacko inventors with unworkable ideas) and that we cannot discuss political implication (like they don't exist?)
Oh and Greg who has worked as an engineer in at least 3 major car companies is wrong about what car companies are doing.
What an oxy acetylene cutting torch can do in a workshop, an oxy hydrogen torch can do underwater. I can't begin to imagine the bang it makes if ignited in a contained space or what materials you would need to hold it and not be consumed by the fire.
Oh and you think a balloon with oxy acetylene makes a good bang. Try a 5 gallon drum filled with a stoich mix ignited by a spark plug fitted in the lid and hooked to a magneto via a VERY long cable. At least 5 clear acres is required to get enough room to do this safely. Hmmmmm. I wonder how a leak and a spark would go with hydrogen and oxygen combined.
Regards
Pat
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RE: Lets take a step from reality. Engine theory and efficiency
a) are not already working on the ideas you propose, in their secret laboratories, with the goal of being first to market with a brilliant new technology and burying the competition mwahaha!... or,
b) have not already evaluated your along with countless other conceivable mechanizations of hydrogen propulsion and dismissed all but the FC and conventional air breathing ICE, due to insurmountable practical objections?
RE: Lets take a step from reality. Engine theory and efficiency
Rod
RE: Lets take a step from reality. Engine theory and efficiency
The infrastructure issue is far more significant than the car side. How do you make the H2, transport it and store it? When you've done all that why use your very expensive gas in a relatively inefficient process like an IC engine instead of in a Fuel Cell car, where you at least might get 80% or so efficiency, whereas your IC will probably struggle to hit 40% consistently, unless you run a hybrid, in which case why not get rid of the whole H2 thing and make it an EV.
Cheers
Greg Locock
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RE: Lets take a step from reality. Engine theory and efficiency
"by some means..............."
Devil's in the details. Unobtainium injection?
RE: Lets take a step from reality. Engine theory and efficiency
Some points to consider:
Brian:
All funding is 50% - Thereby any OEM chucking resource behind behind it still has a financial commitment to the outcome of the R&D
yes i Have around 8 years of welding experience - I am aware of oxy-acetylene but have mainly worked MIG and TIG. The reason for this is that it is a hugely outdated technology that has considerable H&S implications in industry today.
Is it permissible, given the R&D into new materials, ceramics and coatings, that a piston not be constructed that could sustain high temperatures and resist oxydation?
why is oxygen difficult to store? I'm intrigued! hydrogen can be stored at up to 3% (approx) by mass in compressed gas, non-hydride form. Tanks can be used as structural components. A fuel tank changes by around 80kg from ull to empty - whats the issue?
Pat:
What the hell has my username got to do with anything? what do you know about me and my experience in auto? if you cant answer the questions - hypothetical or not, get off the thread or maybe try and read up so you can help?
why is all that you suggest practical (and idiotic?)? Can you try and interact on the theory too?
I worked for an OEM for years and I was not aware of all that went on - Take a look at the publications from major OEMs and they are regular participants.
Why do you continue with the political arguements? lets say, for now, that i have an economical, reliable and safe way of producing hydrogen by electrolysis; and that the oxygen from the process is normally sent to vent. Why is it stupid to try to improve efficiency by utilising this oxygen to make the whole proposition more economical and feasible?
Hemi - Thanks - i am aware of the supposed 'coverups' but dont see them in reality. that theyve investigated it is great - who said i am asking these questions for financial gain? I've not mentioned the business side of things - If h2/o2 combustion is plausible, whats the problem with just simply trying to do some r&D to establish its feasibility and potential for applications elsewhere? H2/O2 flames may form a fantastic replacement for oxy-acetylene processes, for instance.
Greg: Hydrogen can be produced as efficient as 55kWh/kg H2. Take this energy from renewables from sector export (to avoid curtailment of wind) and you have a cheap, zero-carbon gas - gas that is equivalent to the price per litre of gasoline or diesel in the UK.
furthermore, generation at point of use means you only need to transport it once it is on the vehicle - type 3 carbon composite tanks are a proven technology.
Finally, any HICE can be used in a hybrid configuration - theres no need to make it plug in or totally electrified. HICE hybrids can have the fast fill times, exceeding low emission levels (if run at 2 x lambda or greater) and reasonable eficiency, albeit not as high as the battery technoogies. They will also last longer than the 5yr max life on battery vehicles (a life than can be considerably worsened if full range is driven each day). HICE hybrids will readily approach FC vehicle efficiency (most FC vehicles are hybrids anyway) and only fall short by a few percent in heavy start-stop duty cycles. Please remember there are places outside the US. Its called the 'rest of the world' and most of these places do not require high range, high towing capacity, and most pay considerably more for their fuel.
For those of you who have actually given some reasoned responses, instead of focusing upon political, aspirational or economic factors, thanks. But no one has answered core questions asked. Ill look for these somewhere else.
RE: Lets take a step from reality. Engine theory and efficiency
RE: Lets take a step from reality. Engine theory and efficiency
What's god got to do with it, I godam don't know. Maybe when someone comes on here and throws his weight around like he has a god given right to demand our obedience, and first trys to intimidate with innuendo then demands we give the answers he wants, and just also happens to have god incorporated into his user ID, well you figure it out.
Hydrogen fuel has been discussed on here many times before. Sure we get sick and tired of going of the same BS time and time again.
There are a few techniques people pushing BS tend to use. Your posts are full of them. Most here have seen the techniques used many times and recognise them instantly.
No I will not take orders from you about how to conduct myself on this forum. You don't own it and if you want to throw your weight around, I suggest you pony up the cash and buy your own forum. That is how you get to make the rules.
Oxy acetylene is obsolete and irrelevant because it's old. Should we also throw out Pythagoras Theorem because it's old.
Oxy acetylene still has many valid and effective uses and people being killed and maimed by not showing enough respect for it is well known and documented. Hydrogen oxygen has a potential to be even more dangerous for several reasons we should not need to explain if you have even a basic knowledge of the properties of the materials. This is not junior high school science.
Hydrogen oxygen welding also is an old but still useful technology and lessons have been learned and should not need to be relearned.
I wonder what god will have to say about this lot.
Regards
Pat
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RE: Lets take a step from reality. Engine theory and efficiency
RE: Lets take a step from reality. Engine theory and efficiency
The post above mentions that transporting, storing, and dispensing hydrogen would be at least on a level with CNG or LPG. Well, LPG will stay a liquid at normal ambient temperatures. CNG (mostly methane) is relatively manageable; most of us have the same material (natural gas) piped into our houses at low pressure. Hydrogen, on the other hand ...
It leaks out of every conceivable opening. It leaks THROUGH many materials. It chemically combines with certain metals and affects their strength. It is far more difficult to deal with than compressed methane, which is a relatively innocuous molecule (until you mix it with an oxidizer and raise its temperature). It is exceptionally difficult to contain.
If you want to transport it as a liquid, it takes approx 30% of the total chemical energy content to liquefy it, and with most practical methods of making use of the hydrogen, you don't get that back in a useful form in the process of vaporizing it (unless you have a substantial air-conditioning load at the same time).
I would suggest that the recent loss of interest in hydrogen is due to the recent availability of lithium-based battery materials, which at least place the practical electric car on the visible horizon ... without having to deal with all of hydrogen's headaches. Sure, we don't have a battery-charging infrastructure in place. But it's something for which the technical capability already exists. We know how to bring electricity to reasonably remote locations. We just need to DO it. The advent of at least foreseeably practical lithium batteries makes hydrogen technology obsolete, at least for a vehicle that a normal person can use every day and has a hope of being able to afford. That there are currently some obstacles that prevent them from being a practical solution for EVERYone is well recognized - but those obstacles are much, much smaller than the obstacles to the "hydrogen economy".
The thermodynamics of a battery-electric vehicle make more sense than those of a hydrogen vehicle. Both start off with electricity (where that electricity comes from is a different matter). The electric vehicle gets further down the road from each kWh of electricity that you start off with - and probably by an order of magnitude.
And we haven't even talked about oxygen yet.
I can't help it if the answers that I have are not those that you are looking for.
RE: Lets take a step from reality. Engine theory and efficiency
Since most here don't deal in the impossible, they have never built a hydrogen/oxygen fueled engine. Most have probably not even comtemplated building one.
As for your continuing "no political comments". How the hell is posting that a hydrogen/oxygen engine is a retarded idea political?
RE: Lets take a step from reality. Engine theory and efficiency
Anything he does not want to hear he labels political or practical and therefore not theoretical enough.
Maybe it's a PhD subject so it does not matter if it is pure naval gazing with no hope of actually ever being real. That pretty much also means it fails the site policy of posts being by working engineers on engineering work related subjects.
One of the most useful theories I ever learned is that theory should match real world observation. When there are discrepancies, first check your observations for accuracy, if accurate and relevant, then change the theory.
I'm pretty sure that's what Einstein did with the separate laws of conservation of energy and conservation of matter when he calculated the link between energy and matter. Up until recently all observations correlated with his calculations and dependent theory. The recent discovery of particles that appear to travel faster than light have to date resulted in remeasuring. If the scientific comunity is convinced the measurements are truely accurate enough the theory will change to match.
Hows this for theory re use of hydrogen as a fuel.
In theory, a hydrogen molecule is the smallest molecule we can have.
In theory it is so small it can permeate a great many materials and joints normally considered impermeable to all other fluids.
In practice hydrogen permeates through almost all flexible hoses and gaskets.
I could search out old text books re theoretical values for the reactivity of pure oxygen vs air and critical temperatures for spontaneous combustion of many materials, but why should I or why should anyone else here for that matter if the OP can't be bothered doing it himself when presented with experienced based or anecdotal evidence that suggests it might be a good idea to investigate it.
saxgod
If you have not purchased the site recently, you still do not make the rules and I still do not take orders from you.
Greg gave you a big hint re increased oxygen content. Its called nitrous oxide and nitro methane. Both release oxygen into the charge to increase power.
They are old technology and been used since WW11.
While they can both be used to generate enormous power density levels, they both have some severe limitations on their use, even after 60 years of development. If you wish to see the power density and examples of the limitations, go to a drag race meet and watch the Top Fuel cars. They make well over 5000hp from about 8 litres and have engine lives of a few seconds.
Even though they still have nowhere near the tendency to eat the engine internal components when compared to pure oxygen, they start eating holes in engine parts in about 5 or 6 seconds or about 350 engine full cycles.
Regards
Pat
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RE: Lets take a step from reality. Engine theory and efficiency
I'm pretty sure that's what Einstein did with the separate laws of conservation of energy and conservation of matter when he calculated the link between energy and matter. Up until recently all observations correlated with his calculations and dependent theory. The recent discovery of particles that appear to travel faster than light have to date resulted in remeasuring. If the scientific comunity is convinced the measurements are truely accurate enough the theory will change to match.
Sorry for off-topic remark, but, it's been quite a while that physicists have been aware of that fact (as a matter of fact Einstein's theory of relativity and quantum theory are practically be all and end all of modern physics, yet are in fact mutually exclusive*)... Great read on the subject is Steven Hawking's "Brief history of time".
* they're content using each one where it's most correct (i.e. where it's in accordance with observations) and some work on 'unified theory of everything', which may not emerge in quite a while
RE: Lets take a step from reality. Engine theory and efficiency
RE: Lets take a step from reality. Engine theory and efficiency
RE: Lets take a step from reality. Engine theory and efficiency
"because the powerful bread lobby keeps STOPPING MY REARCH "
http://www.youtube.com/watch?v=We3cvjBJSbs
RE: Lets take a step from reality. Engine theory and efficiency
Correct. And even that is somewhat hyperbole, yes with enough stages just about any fuel can be made to achieve just about any delta-V. The weight of the orbiter/space plane meant that several multiple-stage segments of LH2 boosters would've been required. The whole thing would have ended up looking a lot like the Soviet moon rocket, with something like 30 or 40 engines poking out the bottom of a big pyramid stack, and the orbiter perched atop it like a fly on a cow pat.
RE: Lets take a step from reality. Engine theory and efficiency
There are also mechanical problems - e.g. you will be generating the same power with about 1/5th the fluid volume. Your cylinders will be extremely high pressure and small, rendering most of our extensive experience with these things useless. Exotic design changes to piston rings, connecting rods, cooling various parts of the combustion chamber, and even managing temperature gradients will be required. The high temperatures will probably also cause thermal degradation of almost everything under the hood, and certainly will change the heat environment.
I imagine those reasons are among the reasons that you aren't seeing this, in addition to the fact that we can't actually hand wave the hand waved part at the beginning.