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

 

[MikeHalloran]

My very limited experience says that nearly pure oxygen is dangerous, and is treated that way, because anything, including an engine's structure, will serve as fuel. That presents some technical problems and some PR problems.

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

 

[evelrod]

Strictly anectdotal:

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

 

[GregLocock]

" 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?"

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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[patprimmer]

Why would we want to step from reality?

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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[dicer]

If using the products from electrolysis, you do not want a modern
EFI system to use it on. As it would counter any combustion improvement.

 

[saxgod91]

Firstly - I warned you all. Try and open your minds a little.

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

 

[saxgod91]

Regarding cradle to grave efficiency - Do you include cradle to grave efficiency in your calculations of gasoline engine efficiency? Last time i checked refining efficiency peaks at around 73% to the pumps. Then take into account the efficiency of growing dynasoars, letting them die out, then compressing them, waiting a few billion years, then digging it up, and i'm sure a nucleur submarine would look fairly attractive. Lets keep on subject here people.

Steve

 

[benta]

Steve, you need to change your vocabulary a bit.
Hydrogen is not a "fuel", it's an energy carrier produced very inefficiently.

Benta.

 

[Slim3]

I am not well educated, but it seems that the problem is how to produce electrolysis at a sufficient rate on board to supply enough Hydrogen to power a car by the use of oxygen from the electrolysis.

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.

 

[saxgod91]

Thanks Slim. I was not refereing to on-board electrolysis but by dispensing hydrogen and oxygen by some means, to an engine. Lets assume for now sufficient space for oxygen and hydrogen tanks on board a vehicle. hydrogen produced from demand side managed grid, highly dependent upon wind turbines. The electrolysis process i have worked with can be in excess of 80% efficient.

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.

 

[moon161]

My father told me about the beginning of his welding class once. The instructor opened the O2 valve and passed the weld nozzle over some room temperature oil, and it lit w/o an ignition source.

Something to consider.

 

[evelrod]

Hmmmm. "When we run out of oil..."

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

 

[GregLocock]

"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."

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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[saxgod91]

Thanks guys - Anything else?

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

 

[patprimmer]

No

Regards
Pat
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[SomptingGuy]

My employer tends to sail a few yards ahead of the auto industry and the various teams publish their research and contract stuff on our intranet. haven't seen IC hydrogen in a long time. Or even Fuel cells for that matter.


- Steve

 

[LionelHutz]

Despite being able to call hydrogen a fuel, at the end of the day it's still just a way to store energy, the same as charging a battery or moving a big rock up a hill. You will always need to convert some other fuel into the hydrogen. Today, I believe the newer battery technologies are winning the storage race.

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.

 

[evelrod]

I must go with the simple answer---NO.

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

 

[saxgod91]

Great - we are starting to get somewhere.

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