46 replies to this topic

[mrman_3k]

Sorry for asking all so many questions these days, but I couldn't find them using the search.

I wanted to know how water does not get into the intake system of F1 cars with their open "ram-air" intake? If water does get in, how come it doesn't affect the engine? Again, thank you in advance.

[Pioneer]

It does get in. It does affect the engine. AFAIK, its actually aids in making more power. Spraying anything other than fuel into the intake is forbidden under the rules and they don't make rules like that unless theres an advantage to be gained.

[jondoe955]

AND - it gives them more power just when they don't need it.
They used to use water injection on WWII aircraft. I don't remember what it does - probably cools the pistons so they can lean the mixture out more.

[Wuzak]

Originally posted by jondoe955
AND - it gives them more power just when they don't need it.
They used to use water injection on WWII aircraft. I don't remember what it does - probably cools the pistons so they can lean the mixture out more.

Cools the air, making the air denser.

Denser air means they can stuff more of it in (same volume, more molecules).

More air in means they can add more fuel.

More fuel = more power.

[mrman_3k]

But doesn't the water mess up the filter? If it is so good to have some water get into the intake, why are roadcars designed so that water if it is raining gets into the intake tube and plenum?

[weasle]

Originally posted by jondoe955
AND - it gives them more power just when they don't need it.
They used to use water injection on WWII aircraft. I don't remember what it does - probably cools the pistons so they can lean the mixture out more.

they still do in the b52, just check a pic or vid of them taking off (more thrust = more liftoff weight).. the injected water makes for a very black looking exhaust..can see it coming from a long ways away.

[mrman_3k]

So why don't they inject water in road cars?

[random]

Originally posted by mrman_3k
So why don't they inject water in road cars?

They do. See the WRX Sti and Lancer Evo's.

[Pioneer]

Road cars don't need to make lots of power.

Not too many road cars are turbo/super charged either. Its not neccessary.

[mrman_3k]

Don't those cars have intercoolers? I wasn't under the impression they actually shoot water into the cylinder.

Also, doesn't water ruin the air filters?

[Chevy II Nova]

Originally posted by random

They do. See the WRX Sti and Lancer Evo's.

Intercooled does not=water injected..

[Daff]

WW2 aircraft engines used a mixture of water and methanol. (the methanol was there to stop the water from freezing).
It primarily works as an anti-detonant, enabling the engines to run at higher manifold pressure without the risk of detonation. The cooling effect was secondary and minor.
They actually consumed a significant amount of water as well and usually only carried water enough for 5-10mins worth of overboost. (Depending on planetype).

Jakob

[h4lf]

http://www.rallycars...rInjection.html has a good description of water injection.. and http://www.aquamist.co.uk/cp/cp.html aquamist make some systems for your car (perhaps) :-)

[perfectelise]

Originally posted by random

They do. See the WRX Sti and Lancer Evo's.

Water injection to the fuel/air mix,

water spray onto the intercooler,

two different things.

[Greg Locock]

"So why don't they inject water in road cars?"

A very sensible question. The only reasons we've come up with are based on Joe Blow's propensity for forgetting to put any non essential fluids into his car, and putting the wrong fluid in the wrong hole.

In this day and age it does seem to me that it would not be difficult to detect a low/no injection water available condition, and revert to a ******** ignition and richer mixture, before damaging the engine.

If I ever feel like getting my hands dirty again the long suffering Toyota is probably going to get a water injection system.

Oh and by the way the often told story that cars go faster on humid days may be true, but not necessarily because the engine is developing more power. Humid air is actually lower density than dry air, so the air resistance also drops.

[Wuzak]

Isn't a byproduct of water injection increased emmissions?

[McGuire]

Originally posted by Greg Locock
"So why don't they inject water in road cars?"

A very sensible question. The only reasons we've come up with are based on Joe Blow's propensity for forgetting to put any non essential fluids into his car, and putting the wrong fluid in the wrong hole.

In this day and age it does seem to me that it would not be difficult to detect a low/no injection water available condition, and revert to a ******** ignition and richer mixture, before damaging the engine.

If I ever feel like getting my hands dirty again the long suffering Toyota is probably going to get a water injection system.

The first volume-production turbo road car, the Olds Jetfire (a few months ahead of the Corvair) used water/alcohol injection with a 10:1 compression ratio. Sure enough, consumers neglected to refill the jar and the warranty costs killed it. Quite right, today it would be easy to put a fluid sensor in the jar and key it to the engine mapping.

[A3]

A reason why water injection isn't used that much anymore....

http://www.airliners....file/489691/L/
http://www.airliners....file/141726/L/
Thick, black smoke....

[panzani]

There is some interesting related stuff in this thread.

[mrman_3k]

But doesn't water ruin the air filters? The filters on an F1 car look similar to the ones on a road car and the air filter in my car appear to be made out of a paper/cloth type material. Isn't it better for it not to get wet. To me it seems if it were to get wet, it would act like a cover and allow less air into the intake tube and plenum. Am I right or do I not fully understand?

[McGuire]

Originally posted by Greg Locock
Oh and by the way the often told story that cars go faster on humid days may be true, but not necessarily because the engine is developing more power. Humid air is actually lower density than dry air, so the air resistance also drops.

Quite right: We can say that moist air has evaporative properties, which can benefit many engines depending upon their tune, but from there it gets considerably more complicated. Contrary to popular belief, air density does not increase with humidity. Air + water vapor may be regarded as an ideal gas. Water vapor is lighter than N or O2. However, water is heavier and folks naturally confuse the two. The total pressure of a gas is the sum of the partial pressures of its component gases, he belabored. Warm air can hold more water vapor than cool air and as the H20 molecules displace the air molecules there is a rise in vapor pressure. The pressure of the atmosphere remains relative to temperature and volume as per Charles' Law, subject to the properties of its component gases. Meanwhile, only around 21% of the air being displaced by the H20 is 02, which is the only portion of the atmosphere the engine cares about...or is it?

So.....the effect of relative humidity on both engine and vehicle performance is a fascinating subject, far more complex than it first appears. In engines, air moisture content affects 1) the properties of the ambient air taken in, obviously; 2) the air/fuel charge; 3) and combustion, all in different ways. Also, different fuels react quite differently to moisture content (for example gasoline vs. methanol) as do normally-aspirated and boosted engines.

Sometimes the extreme case offers an illustration. In Top Fuel drag racing the engines process a ridiculous amount of air, well over 50,000 liters per min. (And fuel as well: methanol requires A/F ratios of 6.5:1 or so; nitromethane 3:1.) Consequently these engines display a blatant sensitivity to atmospheric conditions including humidity, the latter not necessarily in linear fashion. Racers have found that the standard measures of relative humidity and dew point aren't adequate for their purposes. So they tune their engines by *absolute* moisture content as measured in "grains per pound," consulting some obscure tables they got from the commercial air-conditioning industry. I have no idea exactly what they are doing but I sure would like to know.

[dosco]

Originally posted by A3
A reason why water injection isn't used that much anymore....

http://www.airliners....file/489691/L/
http://www.airliners....file/141726/L/
Thick, black smoke....

The engines in the picture are J-57 turbojets....the "thick black smoke" in the pic has more to do with the fact that:

a. the "can-annular" combustors in those engines were notoriously inefficient/dirty. Remember, those engines were designed in like 1950. (modern annular combustors are way way more efficient and far less polluting than combustors of the 1950s/60s)

b. turbojets are notoriously inefficient at low altitude....requiring max thrust settings and having generally poor low-altitude performance.

With that said, I have witnessed takeoffs of J-57 engined KC-135s, with water injection.....LOUD!!

[BRIAN GLOVER]

Air expands 5 times more than water vapour. On Waine Rainey days, your gasoline engine makes less power. Water injection in WWII airplanes was for more power at full and over gross take offs. The water is added as droplets which raise the compression ratio and play no part in the combustion proccess. It ensures a stoechiometric mixture.
It have the added effect of keeping the cylinder heads cool and stopped holes appearing in the pistons.On aircraft of the 50 and 60 and 70s, when fuel was cheap, you used the fuel for the same reason on take off with mixture levers full forward.

Originally posted by McGuire




So.....the effect of relative humidity on both engine and vehicle performance is a fascinating subject, far more complex than it first appears. In engines, air moisture content affects 1) the properties of the ambient air taken in, obviously; 2) the air/fuel charge; 3) and combustion, all in different ways. Also, different fuels react quite differently to moisture content (for example gasoline vs. methanol) as do normally-aspirated and boosted engines.

I have no idea exactly what they are doing but I sure would like to know.

[A3]

Originally posted by dosco


The engines in the picture are J-57 turbojets....the "thick black smoke" in the pic has more to do with the fact that:

a. the "can-annular" combustors in those engines were notoriously inefficient/dirty. Remember, those engines were designed in like 1950. (modern annular combustors are way way more efficient and far less polluting than combustors of the 1950s/60s)

b. turbojets are notoriously inefficient at low altitude....requiring max thrust settings and having generally poor low-altitude performance.

With that said, I have witnessed takeoffs of J-57 engined KC-135s, with water injection.....LOUD!!

Ah, ok, thanks. I was going with the comments with those pictures.... So water injection doesn't do much with the coloutr of the exhaust smoke?

[McGuire]

Originally posted by BRIAN GLOVER
Air expands 5 times more than water vapour. On Waine Rainey days, your gasoline engine makes less power. Water injection in WWII airplanes was for more power at full and over gross take offs. The water is added as droplets which raise the compression ratio and play no part in the combustion proccess. It ensures a stoechiometric mixture.
It have the added effect of keeping the cylinder heads cool and stopped holes appearing in the pistons.On aircraft of the 50 and 60 and 70s, when fuel was cheap, you used the fuel for the same reason on take off with mixture levers full forward.

Depending upon their state of tune, some piston engines really will make more power in a light rain/heavy mist. This was true of many of the 1960's muscle cars equipped with forced air packages...and IMO went quite a ways in prepetuating the myth that humid air is denser than dry air. In fact, cool air is denser than warm air, and moisture can have an evaporative cooling effect on the intake charge. Also, to some degree air charge moisture content ******* detonation, just as with water or water/alcohol injection. Its role in the combustion process: it kills off knock cells, which the Allies and Axis all used to great effect in WWII. The R2800 Double Wasp was limited to 52" of manifold pressure without it, and 72" with it. "Stoichiometry" refers to the precise air/fuel ratio in which ideal total chemical combustion is realized. For gasoline blends that ratio is about 14.7:1. Meanwhile maximum power is typically achieved in the range of 12.5:1 to 13:1.

[JwS]

I have heard the explaination that the liquid water entering the combustion chamber and flashing to vapor during combustion adds to the expansion of the charge (like a steam engine) and can contribute to power output.
I don't know if this is complete hogwash or not, but it doesn't sound totally off the wall. Of course the volume of liquid water that you could get in would be small, but every little bit of expansion helps.
JwS

[dosco]

Originally posted by A3


Ah, ok, thanks. I was going with the comments with those pictures.... So water injection doesn't do much with the coloutr of the exhaust smoke?

I poked around the links you posted, and a few others. The jist of what the posters were saying was "oh, all that black smoke is from water injection on takeoff." Nonsense.

I think you could say a little of the smoke was caused by the water injection, but 99% of the reason for the smoke is the combustor design, and the fact that the engine is a turbojet.

You can still see some smoke from modern turbofans, but you really have to look hard for it.

[Schummy]

Usually, in typical race track conditions, relative humidity is high or even 100% (starting visible moisture/fog) when temperature is relatively low, elevating relative humidity even if there is the same absolute humidity. Putting it in other way: foggy/moisture days are usually colder. Well, it is well known, but my question is now, we can usually think that when a F1 session is foggy the air is denser (by low temperature effect) or lighter (by humidity effect) than in a next day dry session?

Also, when raining, I suppose water drops will have some "small" effects on drag and aero in general. I don't know if they care to consider it or it's just lost in the greater effects of rain in grip, tyre composition, engine, etc.

[mrman_3k]

Okay, so it seems water is good for engines, but doesn't water mess up the air filters? To me it seems like the air filter would get "clogged" with water.

[Pioneer]

Do they even have air filters?

[McGuire]

Automotive air filter media is designed to intercept (not "trap" necesssarily) particles down to the 10 to 20 micron neighborhood. (Human hairs run bout 60-100 microns in diameter.) Unless the media is not waterproof (unlikely) and collapses and/or disintegrates, water will pass right on through.

I could be wrong but I don't think F1 cars currently use air filters. However, CART and IRL engines use them. Side note: when CART went to its spec engine rule last season, Cosworth found that the addition of an air filter tripled valve seat life. In light of the current F1 rules, that could be useful.

[mrman_3k]

I though on a picture of the F2004's engine I saw air filters on the airbox?

[desmo]

F1 cars use a thin, flat "gauze" filter at the base of the airbox.

[fester82]

Most air intakes for propeller aircraft separate the rain downstream of the inlet as they are not directly inline with the engine intakes. Water in liquid form does not follow the airstream and collects on the backside of the duct. Most rain entering the intake of an F1 would stream directly to the rear of the duct, slide down, and never enter the engine itself. On turbofan aircraft (all airliners these days) the moisture is flung the to the outside and never enters the combustion chambers as only a small portion of the air enters (bypass ratio). To gain any benefit of water injection, the water has to be atomized in order to be part of the combustion process. Water drops down the intake won't cut it.

[mrman_3k]

fester82 - thank you for your response, it was most helpful.

[Yelnats]

Originally posted by desmo
F1 cars use a thin, flat "gauze" filter at the base of the airbox.

Right Desmo and as I understand it this acts more like a strainer than a filter as the short duty cycles of an F1 engine mean they always have a fresh supply of oil and contamination is not a problem as it is on road cars. I wonder if this year they are using smaller FOS (Filter Opening Size) due to the longer duty cycle under the new regs?

[246]

I was told 40 years ago that under the extremes of pressure and temp. in the the combustion cycle water could split its bond to revert to hydrogen and oxygen and that the extra power came from the burning of H2 and O2 is great for burning to.... any truth to this

[Bill Sherwood]

Fester - in reality quite a lot of water goes into the core of a jet engine, but not a lot bad happens from that.
In the Citation I used to fly, without changing the power the exhaust gas temps would just around from 500 to 600degC in heavy rain.
The 747 is better, due to the effect you talk about, but it still jumps around.
In very heavy rain and turbulence it's possible for the engine to flame out from water injestion, so the trick is to not go into those areas of heavy rain or just a lot more power to keep the temps up.
Usually any water that does go down the core just turns to steam vapour well before it hit the combustor section so it's not a problem at all.

[Greg Locock]

"I was told 40 years ago that under the extremes of pressure and temp. in the the combustion cycle water could split its bond to revert to hydrogen and oxygen and that the extra power came from the burning of H2 and O2 is great for burning to.... any truth to this"

No.

The energy required to break the bond is equal to that gained from re-oxidising the hydrogen.

However, there are efficiency gains to be had from injecting water, but not for the reason you give.

[McGuire]

Originally posted by Greg Locock
"I was told 40 years ago that under the extremes of pressure and temp. in the the combustion cycle water could split its bond to revert to hydrogen and oxygen and that the extra power came from the burning of H2 and O2 is great for burning to.... any truth to this"

No.

The energy required to break the bond is equal to that gained from re-oxidising the hydrogen.

However, there are efficiency gains to be had from injecting water, but not for the reason you give.

...and has also featured in an unlimited number of backyard inventor's pipe dreams and some very amusing investor-bilking schemes.

[Formulaben]

Originally posted by Bill Sherwood
In the Citation I used to fly, without changing the power the exhaust gas temps would just around from 500 to 600degC in heavy rain.

Was that with the engine anti-ice on? I fail to see how rain entering the engine core would INCREASE the ITT. See: Latent Heat of Evaporation...

[dosco]

Originally posted by Formulaben


Was that with the engine anti-ice on? I fail to see how rain entering the engine core would INCREASE the ITT. See: Latent Heat of Evaporation...

If the engine ingested enough water, the water vapor would displace the oxygen, thus reducing the density of the air charge.....if you change the density of the air entering the combustor, the film cooling would be reduced, the blow-by cooling (that surrounds the flame) would be reduced, and the fuel/air ratio would be changed (from 'ideal' or 'stochiometric' )....thus changing both the flame temperature and the overall cooling of the combustor.....and everything would get hotter.

Seems pretty straightforward to me.

[Ben]

Never mind water, it looks like sand will be the issue in Bahrain. Mario Theissen has already been quoted in various places that the air filter will be crucial this weekend.

Ben

[dosco]

Originally posted by Ben
Never mind water, it looks like sand will be the issue in Bahrain. Mario Theissen has already been quoted in various places that the air filter will be crucial this weekend.

Ben

Damn staright. The sand in the middle east is supposed to be like confectioner's sugar.....extremely fine, gets into all the nooks and crannies, etc.

Should be interesting to see how the whole Bahrain race pans out.

[Ben]

Originally posted by dosco


Damn staright. The sand in the middle east is supposed to be like confectioner's sugar.....extremely fine, gets into all the nooks and crannies, etc.

Should be interesting to see how the whole Bahrain race pans out.

Very true. When I was working with helicopters it was always commented on that blade life (engine and rotors) used to dramatically reduce in the desert.

Ben

[Bill Sherwood]

Originally posted by Formulaben


Was that with the engine anti-ice on? I fail to see how rain entering the engine core would INCREASE the ITT. See: Latent Heat of Evaporation...

I'm usually tired when I post and so I should have written that a bit more clearly.
I meant to write like this "the EGT fluctuates between 500 - 600degC in heavy rain"


I'm tired now, but have checked it more carfeully this time.

[mrman_3k]

Well now changing the topic a bit, how will the F1 teams not get sand into the engine? Will they be using a filter for the intake air?