Pure oxygen, nitrous substitute, and/or turbo spooling 1

[obanion]

#1 Using O2 gas like nitrous.

This I discussed a few months back, and it was concluded that the reason why oxygen isn't used like nitrous is on a spark ignited engine is that the additional oxygen concentration would greatly increase the tendency for pre-ignition. Basically, it would knock like crazy and probably go ka-boom in short order. Let's not also forget the temperatures would be much higher with pure oxygen enrichment, even if for some reason you could cure the knock problem.

Then a solution occured to me. Inject oxygen ONLY when combined with a spray of water. Water has a tremendous anti-knock effect, which I hope could be enough to offset the effect of oxygen on knock. Water would also absorb all the extra heat and turn it into steam, providing that much extra expansion.

Of course, you also need more fuel to go with the oxygen. So I'd probably try using a water/methanol blend, and spray that wil the oxygen. I'll have to figure out the correct ratio to balance the fuel, oxygen, and have enough water to absorb all the resulting heat release and turn to 1400F steam.

The only wild card here is if the water is enough to counter-act the knock inducing effect of the oxygen? Anybody know? Recommend a ratio?

_____________________________________

Second idea: oxygen for turbo spool

Inject oxygen gas into the exhaust prior to the turbo, while running a 20-30% richer than stoich AFR through the motor. The excess fuel will instantly react with the oxygen, and the combustion will increase exhaust temperature, and velocity, thereby spooling the turbo. The upper limit, is the tolerance of the turbo. You have to limit the oxygen delivery such that the turbo inlet temps do that exceed ~1600F. On a gasoline motor, there isn't very much room to heat the exhaust more. Before you are spooled, the temps are in the 1200-1300F range, so you could boost the temps to 1600F, and taper down the oxygen as you spool up, keeping the final temp around 1600F. Still, it's a limited window.

On a methanol motor, like I plan to run, with much lower EGTs (1000F spool up, 1200F fully spooled), I have a much larger margin. I can effectively have 200-300% as much of a improvement in expansion as I would on a gasoline motor.

 

[SBBlue]

Speaking of exhaust gas temperature, Obanion wrote:

"Before you are spooled, the temps are in the 1200-1300F range, so you could boost the temps to 1600F"

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Uh, I'm assuming you are talking about gas engines and not diesels, but I think you might find that the exhaust temperature is considerably higher -- perhaps 1600-1800 deg F.

On other thing to consider is that by adding mass and increasing temperature, you will increase exhaust back pressure (assuming that the exhaust is going into a load such as an exhaust turbine).

 

[patprimmer]

Obanion

There have been a few threads on the subject of O2 injection, the consensus mainly being that it was dangerous to both operator and equipment.

I can't remember all the details, but a site search should turn up some interesting info

Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[obanion]

True, EGTs in gas engines can hit 1800F before the turbo, but IMO you are pushing it if your setup goes much past 1650F at the inlet to the turbine. Any hotter than that, and I'm looking to change the setup (richer, less timing, water injection, etc).

I'm counting on oxygen into the turbo header to create backpressure. That's the point. A turbine won't start creating any work without backpressure. You need enough exhaust volume to cause backpressure, which then accelerates the turbine. By adding oxygen, and heat, and therefore volume to the exhaust, spool should be greatly accelerated.

patprimer, do you recall if any of those dicussions included a discussion of using oxygen only when strictly combined with a generous amount of water?

The more I think about it, all the hazards of oxygen enrichment seem counteracted by the natural effects of water on combustion and compression. I think there is a good chance a balance can be struck.

 

[SBBlue]

If you increase the exhaust backpressure, you increase engine work. Period.

Will the increase in the amount of power recovered from the turbine offset the increased amount of work the engine has to do because of the increased backpressure?

I can run some calculations if you can provide me with your desired design data. . . .normal exhaust back pressure, increased exhaust backpressure, exhaust gas temperature, and intake manifold pressure.

In addition -- under what conditions do you plan on using oxygen enrichment? Drag Racing? Formula 1 racing?

 

[patprimmer]

At least one problem I envisage is that a bottle of compressed oxygen is a very dangerous article to transport

Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[obanion]

Most oxygen cylinders are DOT approved. That's good enough for me. I'll store the cylinder towards the center of the car so it won't get hit in anything less than a 100MPH collision, where I'd be dead anyway.

From now on I'll refer to the oxygen into the engine combined with water as: OWI (oxygen/water injection)

The turbo spool with oxygen idea is: OITC, (oxygen injected turbine combustion)

OITC: I do understand that the backpressure created by burning oxygen prior to the turbine will increase engine work. Naturally. But it's short and transitory. The oxygen should only be injected for a brief moment to give the turbo a "kick in the ass" then I let off the oxygen and let the turbo do the rest. It's hard to get that first 5psi of boost, after that it tends to take off.

OWI: Would be used primarily for 1/4mile racing, and for an occasional dyno pull.

It occured to me the oxygen enriched/water injected cycle will have higher thermal efficiency. If you double power by running 2bars of atmosphere into a motor with a turbo, you double the compressive work, double the exhaust work, and greatly increase the frictional loading. If you double enriched the air with oxygen (~40% oxygen content), you have twice as much fuel to burn, with the SAME compressive,exhaust, and frictional work. Also, the large excess quantity of water is gonna stay mostly liquid until combustion, then expand to steam. This is "free" expansion work, the engine doesn't need to expend work to compress it, like it does with air (the OTHER expansion media). Also, steam is more efficient media of expansion compared to air, it expands more with a given amount of heat delivered to it.

 

[franzh]

Just because DOT certifies a cylinder for a particular use doesn’t mean that it can be used across the board. As an example: LPG backyard grill cylinders are DOT certified, but CANNOT be used for motorfuel by law since they are not equipped for the proper restraints and other technical issues. Even forklift cylinders which are DOT certified cannot be used for motorfuel on public roadways. DOT only recognizes that the cylinder be transported by the consumer on public roadways without placarding; which is different for an LP gas distributor in commerce and must comply with any state and national DOT rules.

Since you quoted DOT, you must also consider NFPA. Pamphlet 50 covers O2 usage at a consumer site: (

http://www.nfpa.org/Codes/NFPA_Codes_and_Standards/List_of_NFPA_documents/list_of_folders.asp#50)

Lastly, I think it would be very difficult, on the verge of next to impossible, to transport enough compressed or liquefied O2 in a vehicle in sufficient quantity to be of any benefit. The weight of the O2 cylinders would offset any performance gains. That’s why non pressurized liquid fuels rich in oxygen have been used.

Now, as to the technical merits of using O2, it would work. Remember that only 21% of the atmosphere is O2. If you would add 5% O2 to that, you would only raise the level of O2 to 26% total, a small fraction of the total amount. Most computer controlled vehicles today use an oxygen sensor in the exhaust which measures residual O2 in the combustion. Any excess O2 would result in a reduction in injector pulsewidth. As for your second idea, you would be dumping large quantities of O2, and you are back to my original statement about carrying enough O2 onboard to be of any benefit.
Great concept actually, but would be difficult to execute.
Franz


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[harrisj]

How about using Hydrogen Peroxide?

It's got similar latent heat properties to water, and contains a fair amount of oxygen which I believe would dissociate at combustion temperatures.

I'm not a chemist, so I don't know if free oxygen is produced quickly enough. Works for rockets, I believe.

It's also relatively safe - but still needs caution - if you spill high-vol H2O2 onto organic materials, they can spontaneously ignite.

If someone wants to try it, you're on your own! Please don't come whining to me when your engine is transformed into a pile of metal oxides on the garage floor - should be a good firework display though.

Cheers - John

 

[obanion]

I have pondered H2O2 as well. Even discussed it here ahwile back. My conclusions is that it MAY work, it really comes down to the disassociation rate and temperature behavior. My very rough math, based upon limited information on the H2O2 decay vs temperature, suggests it should stay mostly H2O2 during compressionm, and break into (2)H20 + O2 upon combustion, freeing the oxygen just like nitrous.

 

[harrisj]

I believe that there are catalysts which stimulate H2O2 dissociation (Manganese Dioxide? - I'm trawling back nearly 40 years to 'O' level chemistry).

Again, how this could be safely achieved at the right rate is something for the chemists.

I don't like the idea of free oxygen anywhere on a vehicle - I agree it's safe in a sealed, tested and certified cylinder, but so many organic substances will burst into flame if they're hot and there's oxygen about. Introducing O2 at the point of combustion is the way to go.

A quick search of some of my old reference books indicates that the normal maximum concentration of H2O2 in an aqueous solution is 30%. Above this concentration it becomes unstable when warm. 30% is a '100 volume' solution - ie it produces 100 volumes of oxygen from 1 volume of solution. So a 10 litre tank of 30% H2O2 gives you 1000 litres of O2 at STP - not much really but maybe enough for a few seconds running.

John

 

[obanion]

In my math, I found 30% to be the ideal solution actually. Two reasons, cheapest and most available in this concentration. Most important reason, the heat produced from H2O2 decomposition, combined with the heat from combusting the free oxygen with available fuel, is just about right to turn all the 70% water into super hot steam (~1500F).

A catalyst just isn't practical. They only work with 70%+ concentration, and I have no idea how I could encorporate a cataylst pack into the engine, and not be freeing O2 well before combustion.

H2O2 should decompose quickly during combustion. No catalyst needed, the heat of the existing air/fuel charge combusting should be enough to crack the H2O2 wide open, burn the O2, and superheat the additional water.

1000L of O2? If I was flowing say 600CFM@1BAR into the motor, about 600HP or so, that would be about 3560 liter/min of O2. If I set it up to flow the H2O2 at a rate to empty that tank in 1 minute (1000 liter/min), that would be a 28% increase in free oxygen. Should be 28% power, or a 168HP shot. Seems like plenty of use time to me. A 20lb nitrous tank won't last nearly as long at that HP flow level.

 

[obanion]

Correcting, the 1000 liter/min flow rate was the resultant O2, the actual 30% solution H2O2 flow rate in this case would be 10 liter/min.

 

[JayMaechtlen]

how about Nitrous Oxide?
At least it is commercially available, along with valves and related which are more-or-less suitable for automotive use.
Of course, you could kick the inlet and exhaust manifold at the same time- make HP in the motor while you are spooling the turbo up!

Jay Maechtlen

 

[obanion]

Nitrous is too expensive. The cost of a 100HP shot is like $30-$40/min or something. Makes it too expensive for anything for me.

 

[Majik]

OK first of.. lets get some knowledge of nitrous in here.. Nitrous is commonly $3 a pound... so a 10lb bottle is only $30 a fill.. nitrous flow of 4lbs per minute is a 100 shot roughly.. so a 100shot of nitrous would cost you $6 a minute (far from $30-$40) with a 2 minute time window on a 10lb bottle because you can't run them dry... so whoever said a 160HP shot would drain a 20lb bottle quickly has never played with nitrous.. there are guys who run a 20lb bottle all weekend at the drag strip with a 200shot.. and that includes purging.. I've never seen a longer than 1 minute dyno pull or a 1 minute ET.. this isn't salt flats stuff this is local drag stuff.. if you still think you need more than a minute.. hold your breath and start a timmer.. then picture your dyno pull in your mind.. look back at the timmer.. you've still got 50 secs left.. if you've got a ET longer than a minute.. forget about oxygen injection and get a car that runs faster than people can run...

NOTE.. nitrous is not flamable or a dangerous oxidizer... liquid oxygen is.. so unless you get a DOT certification for this ride and have stickers showing your transporting it.. it's not legal.. second if you get in a wreck.. best hope to you..

Second.. liquid 02 comes out COLD! so does nitrous but remember that when you go injecting it into your 1600f enviroment.. people used to inject CO2 onto the exhaust turbine for instant spool.. it was great untill the turbine showed signs of temp shock.. all sorts of flame arresters will have to be worked into the exhaust injection application.. or you'll end up with a cutting torch inside your exhaust manifold.. if you want to spool it faster just put a nitrous nozzle shooting straight at the impeller of the turbine.. no need to shoot cold into the hot side when you can shoot cold onto the cool side... plus the engine will then injest the nitrous and you'll get more HP and faster spool of that turbo since more combustion power is taking place.. hotter exhaust gasses.. the like..

so why don't you try nitrous which is legal.. cheaper than liquid 02.. and won't set your car into a ball of flames in an accident..

if you want to inject water.. instead of that.. goto wallmart or your local gas station.. pick up a gallon jug of windshield washer fluid.. read the ingrediants.. notice it's cheaper than a gallon of bottled water.. and enjoy it's anti knock, cooler runing, and more power properties...


note.. don't try hydrogen peroxide.. that's just wrong.. first get some hoses that will live in an engine bay to transport it... then hose down some aluminum.. rubber.. bronze.. and stainless steel with it.. notice what it does to them all and then think of injecting that into your engine..

 

[timordog]

I don’t think I understand the purpose of pure o2 injection here? I guess I understand the concept of removing the loading of running some type of compressor, mechanical or exhaust driven to increase relative o2 into the engine. My first thought then would be nitrous. But even then I suppose I could understand the desire for a cheaper medium. But then I have to think well you still need to buy the o2 so why not use a separate stand alone compressor and prefill at tank in the car using ambient air the same a turbo or supercharger would. Compressed air injection is proven, although outlawed in drag racing, which I don’t really understand given it serves the same function as nitrous but it is free.

And even nitrous and compressed air seem like a hassle to me when you can make more output with a decent turbo setup than most stock engine designs can withstand, and more than a few stock drivelines. And even if you upgrade the engine and driveline for additional output compounded turbocharging will still make more boost than even these designs can withstand. The major limitation seems to be the ability to reliably use the amount of power you can easily make with turbocharging and the cost involved in that, not so much making the power with exotic techniques.

And even if you don’t want to go to the trouble of developing a method for compressing the air going into the engine there is another simple chemical way other than introducing a 3rd ingredient, (o2, nitrous, or hydrogen peroxide) with the existing air to use larger quantities of fuel to make power, why wouldn’t you just put the o2 in the fuel itself. Then you would have something like nitromethane, and you can scale this method easily by just adding more and more to tailor your output level to the strength of your engine design. I don’t think many will argue the small quantities of nitro necessary to make more power than a stock engine can handle.

 

[patprimmer]

Air is only about 20% oxygen.

Therefore you need 5 times as big a tank, or 5 times the pressure to get the same effect.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[NickE]

just as a side note----

Turbo spooling has already been solved. The answer is called Anti-Lag or BangBang. It is used on all open class SCCA (Well they used to be SCCA) Performance rally cars. It is also used on FIA WRC cars. This is accomplished by using a solenoid to kick the throttle plate open, then retarding the timing by a significant amount. Or by skipping one ignition event per 4revolutions. (I believe this is called rotational idle since on a 4 cyl motor the "misfire" rotates through the cylinders.)

There are several things that need to be done to the exaust system to survive this. First the exaust manifold will need to withstand the incredible temperatures and pressures that it sees once it becomes a turbine jet cumbustion chamber. Second the turbo will have to be able to withstand being at full spin and max temp for much longer than in a normal vehicle. Thirdly the rest of the exaust will need to withstand constant temps >1500F. I believe that the FIA WRC cars use an inconel alloy that is lagged so as to not heat surrounding components.

link:

http://www.rallycars.com/Cars/bangbang.html

nick