Can IC engine efficiency can be increased beyond 60% ?

[sr241]

I found following claim from an inventor:
“The limit of IC engine efficiency cannot be normally exceeded due to facts entropy cannot be decreased and 2nd law of thermodynamics (heat cannot flow from cold to hot body). Injecting water in the beginning of expansion stroke can overcome these problems since entropy of working fluid (hot gas) will be decreased when water’s entropy is increased while converting it to steam but as a whole (water and gas) the entropy will be slightly increased or remain same. The temperature of exhaust gases too will be lowered since water too has to be heated, this heating of water to steam will result in higher pressure thereby resulting in more work.”

Is this claim a valid one? If not; why?

For more detail on this inventors work “ http://sites.google.com/site/anyoonrotaryengine/ “

 

[Ranger Mike]

every decade or so when the greenie weenies are crying for the end of " man made pollution"
this water injection pops up. next look for 100 MPG by placing cow magnets on the fuel line!
not worth responding to this assertion. if you think about it, the purpose of the " expansion cycle??" is to create maximum POWER from the fuel / air mixture packed into the cylinder. after you light the candle why would you piss on it?
or am i missing something?
I can see water being used to cool the fuel air mix to help cram more into the cylinder but two big things are a problem here.
1. water ( unlike burnable gasoline) can not be compressed
2. introducing water into the ignited mix will dilute the " expansion"
Is the think that introducing water during the " expansion cycle" will make more power by having the water turn to steam ? I mean you got 1200 degree plus temperature going on and you add water that flashes to 212 degrees and does what?
thing two ..why has this not been done by Detroit ifin it worked?

 

[sr241]

Actually water is injected after constant volume heat addition in his engine that means water is injected after complete combustion of fuel at constant volume. one of the other main feature of his engine is simple implementation of constant volume heat addition.

There are 6 stroke engines and turbo-steamer from BMW that use water to recover waste energy.

 

[Ranger Mike]

i do not understand what you have stated?
water is injected after combustion?
why? to cool the exhaust gases?
is water injected in combustion cycle or on exhaust stroke?

 

[sr241]

you have to think in terms of Otto cycle where heat addition and expansion are separate. in normal engines combustion continues 60-120 after TDC in expansion stroke. But in Anyoon engine which obeys Otto cycle perfectly; there is a 30 degree of constant volume heat addition during which all fuel is combusted and after that there is 180 degree of expansion stroke (power stroke). water is injected in the beginning of expansion stroke. so as water is converted to steam from heat of hot gases the pressure of whole system increases resulting in more power and work.

 

[russ_watters]

I've never seen compelling evidence for water injection being a major benefit. Water for waste heat recovery (adding a small steam engine) seems like the better deal to me.

 

[Ranger Mike]

Excellent insight Russ...any pre heat to closed loop steam engine to drive accessories ( charging system) would help.
I need to see empirical data of water injection before going further.

Question - how does introduction of H2O effect exhaust gas temperature?

I suspect , strictly opinion and anecdotal is the exhaust temperature would be lowered thus reducing velocity and hurting performance.

 

[sr241]

water injection is like steam engine is integrated to expansion stroke.

what is lost in hot gas in expansion stroke is gained by water. even though latent heat is required to convert water to steam there is huge gain in pressure during this phase change. exhaust temperature will be lower but that's the idea! maximum conversion of heat to mechanical energy in expansion stroke itself.

 

[Ranger Mike]

You stated "there is huge gain in pressure during this phase change. "
just how much?

 

[xxChrisxx]

Oh god not this one again. I can't remember is this rubbish was posted on here or on F1 forums.

I've never seen compelling evidence for water injection being a major benefit. Water for waste heat recovery (adding a small steam engine) seems like the better deal to me.

Normally water injection systems are used as charge cooling (in the same way running a racing/turbo car does when you have AFR < 12.5:1)allowing higher compression ratios and more aggressive cam and spark timing. Combined with EGR you can get on the order of a few % efficiency increase. That's all though, anyone that claims that they can produce a zillion horsepower with a thimble full of fuel merely by adding water is clearly talking cobblers.

EDIT: I've just realized that OP is talkign about a different typre of water injection system from the above.

There are also six stroke engines, that use waste heat as a steam cycle. The extra complexity and uneven power strokes totally outwieghts the benefits though. The water is used in an entirely separate stroke process much closer to what Russ was talkign about.

However let's take a look at this 'water injection'. Typically combustion pressures in a normal 4 stroke will peak at about 600ish bar (off the top of my head). I don't have my steam tables available, but I seriously doubt that even at the hottest point in the cycle you'd get steam above 10-20 bar pressure (you can't inject that much water beucase of the short amount of time available).

So AT BEST: You'd have about a 3% increase in gross power output. However, you then need to run the pump and injectors for the water injection system reducing this number. Also there are no real figures for the amount of water needing to be pumped and injected, so it's impossible to extimate feasibility.

 

[sr241]

Air standard cycle has peak pressure (P3) of 140bar, but in actual cycle it is around 60bar

 

[Ranger Mike]

thanks Chrisxxx
i will look up old post and study up on it..did not know this came up before..as always your opinion is most valued
rm

 

[mender]

It's about using rejected heat to do additional work on a piston or turbine to increase the energy used. The theory is valid but hard to accomplish in practice. There are some very real benefits if the issues can be resolved.

I've played with this before (grant money available for the right project!) and from what I recall the potential for a 30% increase in efficiency was indicated. I don't have the numbers at hand though.

 

[xxChrisxx]

Air standard cycle has peak pressure (P3) of 140bar, but in actual cycle it is around 60bar

Well it's something highish, 140 sounds a little low but does is closer than 600. It's been a while sinse I've done this.

Still the point stands, there is a reason why no one really does this. Yes there are gains to be had, but gains can be more easily found elsewhere. It's not really econimical to use water injection in this manner as they gains are so small.

 

[sr241]

There are some very real benefits if the issues can be resolved.

I am curious to know about the issues you faced. as you have hands on experience in it

 

[mender]

Well it's something highish, 140 sounds a little low but does is closer than 600. It's been a while sinse I've done this.

Still the point stands, there is a reason why no one really does this. Yes there are gains to be had, but gains can be more easily found elsewhere. It's not really econimical to use water injection in this manner as they gains are so small.

Peak cylinder pressure rarely goes above 60 bar (800 psi) for pump gas engines.

 

[mender]

I am curious to know about the issues you faced. as you have hands on experience in it

Did a study on it but didn't get to the prototype stage; other things managed to push it down the to-do list.

 

[russ_watters]

Well don't make us beg: what were the results of the study? If you have evidence to support your initial claim, provide it!

 

[mender]

I'm not trying to tease, it was about 15 years ago and my notes are buried.

From memory:
Design: Double acting piston with IC on one side and water cooling/expansion stroke on "crankcase" side. Water cooling underside of piston provides more even piston temps, allowing higher compression ratio and higher engine temp with same octane fuel, lighter pistons, thinner rings, etc.

Effect: up to 15% more combustion efficiency plus about 15% waste heat recovery. Reduction in cooling system size for same power output, better space efficiency and aero, etc.

Issues: lubrication, cold weather running.

I was putting together a proposal for an advanced vehicle drive train that included an integrated high efficiency regen braking and energy storage system, plus a few other odds and ends. Got a good reply from the DOE but other things got moved up instead.

 

[sr241]

the problem with 6stroke engine and turbo steamer is that if water injection is separate there will be scenario that piston or turbo vane is moving faster than the rate at which water is expanding. thus reducing the benefit of water injection. so complex mechanism is used in six stroke engines. however if separate and specially designed steam engine is used for water injection that drives auxiliaries and not connected to crank shaft then such problem will not be there. But in 'Anyoon engine' there will be increases in Both efficiency and MEP (There by power) due to water injection

 

[russ_watters]

I'm not trying to tease, it was about 15 years ago and my notes are buried.

Sorry, the wording of that was because I was posting from a Blackberry and when I'm reading a post, by the time I scroll to the bottom I can no longer see the top and I forgot who posted it...I though it was the OP.

Thanks for the info.