Lets take a step from reality. Engine theory and efficiency

[saxgod91]

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

 

[BrianPetersen]

The ONLY reason any of the auto manufacturers have put ANY effort into hydrogen - whether through ICE or fuel cells doesn't matter - is that huge R&D incentives were provided from the government and as a side benefit, if a successful method were found to do it, it would get government emission regulators off the auto industry's back. Note that a hydrogen-fueled ICE can still produce NOx, and there will still be traces of other emissions from the lubricating oil. Using pure oxygen and hydrogen would solve NOx, but oxygen + high energy fuel being burned = cutting torch that will eat pistons and lubricating oil. Also, both hydrogen and oxygen are difficult to store. The oxygen part of H20 weighs eight times more than the hydrogen part, too. It's difficult enough to cart around the hydrogen; why cart around the oxygen when all it's going to do is add more weight and complication and burn the engine itself from the inside out?

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.

 

[patprimmer]

Brian

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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[Lou Scannon]

Steve, what makes you think that the large, well-funded, and arguably, clever organizations like BMW that are investigating hydrogen propulsion:

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?

 

[evelrod]

My money is on that secret "100 mpg" carburetor that GM has been hiding from us for the most part of a century!!!

Rod

 

[GregLocock]

Shrugs, you listed dabbles and FCVs, not serious ongoing as of 2012 research efforts into H2 ICE, and certainly no pure O2+H2 ICE.

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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[thruthefence]

"dispensing hydrogen and oxygen by some means, to an engine"

"by some means..............."

Devil's in the details. Unobtainium injection?

 

[saxgod91]

why cant you guys just answer the questions? Can i just ask are you all american on here?

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.

 

[Lou Scannon]

Steve, you didn't answer my question. Assuming your concept truly has merit, what makes you think that the big players are not either way ahead of you developing it, in secret, or, alternatively, that they have not investigated it sufficiently to have determined it is impractical and dismissed it accordingly?

 

[patprimmer]

What's being American got to do with it, but no, quite a few of us are not American.

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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[saxgod91]

Thank you all for your input.

 

[BrianPetersen]

One thing that the vehicle manufacturers NEVER mention in anywhere sufficient detail when they talk about their latest hydrogen powered creation, is where the hydrogen is going to come from and how it's going to be stored.

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.

 

[LionelHutz]

Your basic question seems to be that you know the engine will be more efficient but you want to know why it would be. So, you first need to know if it would be more efficient.

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?

 

[patprimmer]

Lionel

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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[WolfHR]

Pat, you said:

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

 

[btrueblood]

Rocket scientists have acknowledged since day zero (Tsiolkovsky's papers, c 1900) that H2/O2 combustion is one of the "perfect" fuel/oxidizer combinations. But for terrestrial launch vehicles, it has proven to be a worse choice than denser fuels, such as kerosene or hydrazine, due primarily to the penalty in structural weight to carry the less dense liquid H2 fuel. During the development of the Space Shuttle, hydrogen fueled main engines were "mandated" by the requirement for re-usability (if you've ever looked at a kerosene fueled liquid rocket after firing, you'd know why). But it was quickly realized that liquid H2 fueled engines would never get off the ground (due to the structural penalty already mentioned), and the requirement for solid rocket engines (strap on boosters) was added. We all know how well that choice worked out.

 

[Lou Scannon]

But it was quickly realized that liquid H2 fueled engines would never get off the ground (due to the structural penalty already mentioned)

bt, can you clarify, the space shuttle in particular could not get off the ground [with LH2 fuel only], not LH2 rockets in general, correct?

 

[Tmoose]

"what makes you think that the large, well-funded, and arguably, clever organizations like BMW that are investigating hydrogen propulsion..."

"because the powerful bread lobby keeps STOPPING MY REARCH "

http://www.youtube.com/watch?v=We3cvjBJSbs

 

[btrueblood]

Hemi,

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.

 

[JSteve2]

You can only achieve the efficiencies you seem to be suggesting at extremely high combustion temperatures - truly extreme to take the 42% or so theoretical maximum on current combustion engines up to 80%+. Because of the very efficient fuel cell competitor for your technology, you will have to go to prohibitive temperatures to make an H2 engine remotely competitive (even if we hand wave off H2 generation, distribution, on-vehicle storage). By the time you do all the exotic things to make your engine survive (ceramics, barrier coatings, cooling devices, etc.) you have a massively expensive project just to approach the efficiency a fuel cell can make out of the back of someone's garage.

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.