Nitrosoxide

[Squealing Pig]

Flicking thru a US hot rod magazine today and seeing a few nitrosoxide kit adverts made me think why has it never been used on piston engined aircraft to enhance take-off or engine out performance? Or has it? I’m guessing that its use cannot be prolonged long enough (cylinder head temp issues and all that)

Anyone in the know ?

[cessna l plate]

Use for too long, and there will be large pile of molten metal where the engine used to be. I imagine on the basis that it is used in cars for short bursts, it wouldn't really suit an aircraft engine for a few reasons.

Head temp as mentioned

aircraft piston engines are low revving, so banging that stuff in will exceed the red line in a jiffy.

At full power, the propellor tips are not a million miles away from the speed of sound anyway, adding that might take them over, and aerodynmically, that is a bad thing.

Hope my humble opinion helps, now those with a more presice knowledge will blow me out of the water no doubt!


Crash helmet on and waiting

[BOAC]

I have a feeling it was used in the Second WW on something or other (Me109??) to produce more power. You may be able to follow up this Google link (http://www.idavette.net/hib/nitrous.htm)?

[G-CPTN]

>At full power, the propellor tips are not a million miles away from the speed of sound anyway, adding that might take them over, and aerodynmically, that is a bad thing.

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Surely there ARE some 'planes (current and legacy) where the prop-tips do exceed the speed of sound. How does that relate to the comment that it is a bad thing?

I agree that the use of nitrous oxide in a/c would not be a sensible idea. Many of the car engines go bang anyway. Russian Roulette springs to mind . . .

Spitfires (and many others) had an 'emergency' setting with extra supercharger boost (though not for take-off).

[cessna l plate]

As but a humble student ppl I am not too sure of the physics involved, but I would from a common sense position think that if the prop exceeds the speed of sound, then rather than pushing the air backwards to gain forward thrust, the supersonic prop would actually move the air in a different direction or not move it at all.

I have read that a supersonic prop can result in a loss of thrust. 30% springs to mind for some reason.

At the end of the day, the original post was about NOx, and although a nice idea, in practice silly if not downright dangerous.

[head_girl]

Nitrous Oxide not a good idea in general. What you can do with it is liquefy it and inject it into the cylinder along with fuel. Whereupon it becomes gaseous and absorbs massive amounts of heat in doing so thus cooling the combustion chamber. Heat engines like a cold input and a hot output because the maximum of work can be got out of it. Work = Heat. Now if you can set fire to it in a petrol/gas mixture (or methanol/gas) it separates into nitrogen and oxygen exothermically i.e. it gives off massive heat and lots of oxygen to sustain and enhance the burning of more fuel. So it helps get a colder input and a hotter output. Lots more work the engine can do. The nitrogen is supposed to guard against pre-ignition but this is a common misunderstanding. However, so good is it at boosting engine performance you need a new engine which does not trouble hot-rodders but does trouble LAMES. It also is not as good at chemistry as it should be and has a habit of forming corrosive by-products. But then the engines don't last long enough for this to be a problem. Lordy another day starts in Paradise... so my advice is, Nitrous Oxide? You must be having a laugh....

[Piltdown Man]

However, water/methanol was/is used on the F27. When doing it's job, the engine made a slightly different noise, but you couldn't really feel the difference. It gave a few hundred kilos more on your RTOW from a short runway. However, it is expensive and most of the time just ballast because you don't use it on every departure. It was also a pain for the refuellers to stock and replenish. However, the chaps at SOU were more than helpful.

[Brian Abraham]

the germans used it in a number of their aircraft during WWII. Would have to get the books out to verify which ones

[westhawk]

NOx provides a big power boost to piston engines when used properly. But there is no "free lunch". Racers have used it successfully for a long time. Most major racing organizations have banned it's use in order to help teams control costs and equalize competition. It is costly for all of the above cited reasons. I seem to recall that car racers got the idea to use NOx from some WWII aviation applications. Don't know what types. The only current aircraft use of NOx I am aware of is in unlimited air racing. I don't know how many air racers use it other than "Rare Bear". Race 77 is a highly modified clipped-wing F8F Bearcat sporting a nitrous guzzling R-3350 radial making 4,000+HP. Like all the top racers, It has had it's share of "maydays" after suffering engine trouble during races over the years. A sight, sound and feel to behold! Here is a link to the bear.

http://www.rarebear.com/

Best,

Westhawk

[Brian Abraham]

Got the books out and here you go.

The only Allied use of nitrous oxide was one squadron of night fighter Mosqitos Mk XIII’s (50 aircraft in all) had the system fitted to their RR Merlins in order to improve speed and climb rate above 20,000 feet for short periods of time.

Janes “All The Worlds Aero Engine” has the following,

Nitrous Oxide Injection – This power boosting system was first referred to by the Germans by the code name “ha-ha”, nitrous oxide or “laughing gas” being injected into the supercharger. The nitrous oxide was retained under pressure in liquid form. The system was designated as GM 1.

Installation – In a twin engined aircraft (Ju 88 S) the liquid is carried in three cylindrical containers arranged pyramid fashion, located in the fuselage. Later aircraft had a single 75 gallon cylindrical container. Compressed air cylinders contained the air for forcing the liquid along the pipe lines to the engines. The complete installation weighed 400 pounds dry and the weight of the nitrous oxide was 900 pounds assuming full tanks. The tanks were heavily lagged with glass wool and enclosed in a shell of light alloy to prevent evaporation.

In the Ju 88 S-1 (BMW 801 G-2 engines) injection was arranged at two rates, “normal” 7.95 lb. per engine per minute and “emergency” 13.2 lb. per engine per minute. The endurance of the systems at the two rates was 27 mins. and 45 mins. respectively.

Performance – This power boosting system was used above the rated altitude of the engine. The nitrous oxide provided additional oxygen for the engine, and also acted as an anti detonant. Part of the increased power obtained was due to its charge cooling qualities.

The Ta 152 B aircraft with a DB 603E engine had a maximum speed of 417 mph at 27,000 feet. When the GM 1 system was used at an injection rate of 13.2 lb/min the maximum speed was increased to 348mph (that’s what the book says – think they may mean 448mph which coincides with other sources) at 32,800 feet. The increase in horsepower was 350 HP at 32,800 feet.

With the Jumo 213E engine installed in the Ta 152 B the maximum speed with out GM 1 was 439 mph at 35,000 feet and this was increased to 443 mph at 44,300 feet with the maximum rate of injection of 19.8 lb/min. This represents an increase of 418 HP.

Other systems the Germans used
Methanol water injection MW 50 49.5% by volume water, .5% anti corrosion, 50% methanol
MW 30 69.5% water, .5% anti corrosion, 30% methanol
Me 109 carried 25 gallons, also used on Ta 152 B , Fw 190 (DB 605, BMW 801 and Jumo 213A engines). Ta 152 H high altitude reconnaissance carried 18.6 gallons of GM 1 and 15.4 gallons of MW 50

Ethanol water - used in place of MW 50 49.5% water, .5% anti corrosion, 50% ethyl alcohol

Pure water injection (BMW 323R and Jumo 213A engines) the Jumo could develop 1,650 HP with pure water and 1,670 with MW 50 against a basic power of 1,610HP (high supercharger, +8 lbs. boost)

Petrol injection into the air intake – used on Fw 190 with BMW 801 D engine (1,730 hp at take off increased to 1,870 hp with petrol injection. The injection allowed the normal take off boost limit of +5.5 lbs to be increased to +8.8 lbs)

[head_girl]

Water methanol is used but for a slightly different reason. I cubic centimetre of water in its liquid phase becomes 22.4 litres of gas (steam)! Ouch! That adds to the thrust in any engine be it the last models produced of R-R Merlin, DC-8's on a roll (That you Old Smokey?), the Harrier in a Hover (ladies and gentlemen, a steam powered hovercraft!) etc. The methanol acts as an antifreeze should you carry it around and of course has its own calorific value. But unlike NO2 it has no really dramatic exothermic whizz and is there to cool the hot parts but also 1cc to 22400cc is quite a volumetric expansion. Another day in paradise ends, Tallulah, peel me a grape!

[rigpiggy]

AWI on the Dart and garrett is meant to cool the incoming air charge, and by doing so improve the density/mass airflow this allows more fuel to be burned without exceeding temp limitations. Nox cools the incoming charge, but the largest reason for increased performance is that it has a higher percentage of oxygen allowing , once again more fuel to be burned. This makes more sense in a piston engine as to make the most power a stoichiometric mixture must be burned around 14.7:1 air/fuel. most Nox systems actually have a dual system with both fuel and Nox injectors. injecting Nox on its own without a commensurate increase in fuel will increase temperatures and cause detonation. In other words eat your engine