water injection to gas engines 7

[PISTO]

ErickFahlgreen.- Very good work, I will study the charts.

SBBlue.- That is a good point and one more reason to consider water as an option to increase power and efficiency.

Patprimer.- I think the clue is that what you are modifying is the relative humidity of the air while entering the manifold that produces an adhiabatic cooling (temperature reduction without heat transfer) same as those new room humidifiers, with the subsecuent reduction in volume and increase in O2 concentration. There is no point in adding so much water that water vapor (in case temaperature makes it boil)will displace O2.

I think the point is to relate the benefit at diferent relative humidity of the intake air, then evaluate other forms of using water injection DIRECTLY into the chamber to take advantage of the expansion factor.

So one thing is to air moisture to the air before entering the chamber to increase O2 and another system is water expansion inside the chamber. If both are used then add up the benefits.

Looks to me this is something worthwhile taking by someone that has a laboratory and could run lots of tests under diferent conditions to evaluate the practical and economic impact before a serius application is considered.

PISTO

 

[Andybee]

Re Patprimmers comment about slowing down in the rain casusing apparent fuel consumption improvement and BHP gains has a hole in it - many drivers have said that cars pull noticeably better on damp days i.e. those where the there is high humidity but no standing water on the road. Why would you drive slower because there are low lying clouds, and why would 'the car is slideing about and spinning wheels'under these conditions?

Sorry, but damp days REALLY DO improve performance.

I managed to mimic this with a latex microbore hose fed into the carb intake. The other end of the hose was sitting in a jar of water. The engine vacuum drew water through the hose in proportion to the rpm it was turning.
Result? A small but noticeable increase in response.

Surely someone with more time and the appropriate measuring equipment could rig up something to reproduce that in a professional capacity.

 

[PISTO]

Andybee:

I agree with you about better performance on wet days, I happened to notice that a lot when I had a small VESPA scooter with a 150cc two stroke engine.

Of course someone living in Vancouver may not notice a diference year round, while someone in Las Vegas might.

Just one coment about the way you injected water. If you injected water directly into the carb you probably benefited only from the expansion of water in the combustion chamber, but I doubt you got the effect of cooling the air before entering the chamber with its corresponding volume reduction increase of O2 concentration, I think, for that you would need a device that produces a light mist to rise humidity and probably some time before it enters the chamber.

Yes, I wish someone with the means could go into this and come up with a simple device that controls this.

PISTO

 

[Andybee]

I have an Autogas system on my Rover V8 (3500cc) which runs twin SU carbs. The gas is fed from an aspirator / vaporiser unit (several names for it) as the vacuum demands it. There is a diaphragm system acting here, as the intake vacuum increases, more gas is delivered. So couldn't the same method be used to deliver a mist?

Patprimmer (above) said Spearco make an electronic and vacuume controlled unit - is this the solution?

Yes, my latex pipe was primitive, but it proved the point, and improved the performance.

 

[turboice]

I think the Aquamist 2s would do what you are suggesting. It would take a bit of of a different approach to do it with an N/A motor since one of the matrix loads is MAP and meant for forced induction. If you could provide another signal indicating load such as vacuum or throttle position the 2s will meter the amount of atomized water you desire at any location that you place the jet based on RPM and your chosen load reference.

Ed.

 

[glueontop]

I don't think that adding water to a stock engine is a good idea. The high temperature steam will probably cause more corrosion problems in the cylinders and the exhaust system than you will save on gas. If you have ceramic cylinder and stainless steel exhaust, maybe

 

[CanadaTech]

Glueontop... are you aware of the by products of combustion?

 

[CanadaTech]

Andybee, your simple system is not at all primitive, but very practical. Small engine manufacturers are still using vacuum/syphon venturi carburators and although simple, they do work well with little trouble. I had been thinking of trying to incorporate a sonic humidifier, this may be easier.

I'm not so sure the injection of water causing a COOLING effect to the charge has much merit in the investigation of why water injection works.

If COOLING the charge results in an increase in power/efficiency, then operating an engine in severe cold should be optimum. Anyone who lives in a cold climate can verify that as false. We also know colder air is drier.

Also, it would make false the fact humidity plays a very real effect on efficiency and power. Humidity provides NO COOLING effect at the intake of an engine.

However, we do know intercoolers do work.

I also looked back into a text I have and elementary Otto cycle theory does state mass flow is important in regards to power and efficiency. (think... if a lean A/F mixture provides optimum power and efficiency-->burns hotter, why does adding more fuel also work?-->burns cooler)

The conclusion I draw from these few statements (without attempting the math behind them - I'd like to see it verified for disproved)

Water injection into the intake of an engine should do two things. It should provide evaporative cooling (same effect as intercooling) and it should raise the water vapor content of the charge (same effect as humid air).

That's my 2 bits.

 

[turboice]

Injection of water definitely will cool the charge if the relative humidity of the charge is less than 100% relative humidity. The evaporation of liquid water up to 100% relative humidity will reduce the charge temperature. The ability of the water to do that is very dependent on the charger temperature and the induction length after the injection. Clearly on most NA systems the induction is short and there may not be enough time to reach 100% RH before the valve. The cooling effect to the extent it exists is much more noticeable in dry climates than humid climates. See this link:

http://not2fast.wryday.com/thermo/water_injection/opt_mass.shtml

Humidity provides no cooling effect because water vapor has much less latent heat than liquid water.

Cold air is denser and will be more efficient and powerful. The difficulty in extreme cold climates is getting the motor to operating temperature not that the induction charge is too cold.

Efficiency AFR and Power AFR are on opposite sides of stoich. Otto motors max efficiency is slightly leaner than stoich and max power is slightly richer than stoich -

http://www.turboice.net/?documents/turbowhitepaper/tuningopportunity2.htm

Ed.

http://www.turboice.net

 

[patprimmer]

OK
I will comment further as a few guys who have some understanding, and thinking capacity have contributed.

Thank you Canadatech, SBBlue, EricFahlgren, Greg Locock, Redmane, and turboice

Eric, thanks, I never actually did the math. Bottom line is, that's not where the real improvement comes from, it comes from supression of detonation, and the expansion characteristics of water to water vapour IN THE COMBUSTION CHAMBER.

792003, As I understand it, WW11 aircraft had a throttle stop with seals. The pilot was allowed to push the throttle past the stop and break the seals for EMERGENCY WAR POWER. It is extra boost that gave the supercharged engines in the WW11 planes their extra power, and the water injection was used to avoid detonation when useing this extra boost. Once thre throttle stop seals were broken, the engine had to be dissaembled, checked for damage and rebuilt. It is a good way to remove carbon deposites in anything from a Mack truck to a Vespa.

PISTO, Adhiabatic cooling is not all that new, it was used prehistory by man, as they sat by the river, pond or whatever because it was cooler, or wet themselves down to cool off. It was first deliberate controlled by the ancient Romans when the built fountains in their courtyards over 2000 years ago. There is a point to adding more than enough water than required to reach 100% RH in the manifold, as RH changes with temp and pressure, therefore more water evaporates as the temp increases on the compression stroke and dureing combustion. Normally the easiest place to add all the water is near the carby or inlet to the plenum. A lot of work has already been done in some really serious laboratories like Rolls Royce, Packhard and Allison aero engine departments, the SAE, and NACA (who just happen to be the precursor to NASA, but what would they know)

SBBlue, A very interesting insight, but you only looked at halfthe reaction. As the water evaporates, it absorbs latent of vaporisation and thus cools the charge, thereby reducing it's volume, and concequently it's pressure, but it also adds water vapour to the charge, increasing its volume and pressure, I have not done the sums for the net result. Maybe Eric still has his calculator out.

Andybee, Yes the Spearco system does work, so long as you use some alcohol in the water to kill algee, and preferably filter the water between the pump and the jets, to remove potential blockages.

Andybee, I don't care what some drivers say, DYNO'S say engines make more power on cold days, but less power on humid days. This is because cold air is more dense, but a molecule of water vapour will displace oxygen in the air. Dyno's provide objective data, drivers only provide subjective data.

I have used this "theory" to tune my race car. It has a supercharged 350 Chev, with constant flow mechanical injection and runs alcohol. It has 11:1 compression and 30 pounds boost. As this type of injection has no means to correct itself for air density changes, I need to tune it to the weather by changing jets before every run. I calculate air density from pressure and temperature figures, and the higher the density, the more fuel I give the motor, BUT, THE HIGHER THE HUMIDITY, THE LESS FUEL I GIVE THE MOTOR.

We recently ran the 1/4 mile in 8.33 sec at 161 mph in a 2600 pound street registered car, and won our class at a national meet. I have never had a problem caused by incorrect mixture when useing this methodology.

READ THE PREVIOUS THREADS AND THE LINKED SITES AND PAPERS


Regards
pat

 

[glueontop]

CANADATECH...

I am well aware of the combustion process. But the reaction is not instantaneous. in fact, at the speed most recent engine revs, the water will not have the time to vaporise and react before it is pushed out of the cylinder. So there will be steam for a significant amount of time in the cylinder.

Some petroleum companies are starting to sell water/diesel emulsion to solve the problem. the water is emulsified with the fuel and not injected as two components. and this is for slow reving large diesel engine.

 

[turboice]

The point he was making is that steam is a substantial byproduct of carbon combustion - the steam is in the exhaust anyway. The amount contributed by water injection is small by comparison to the already existing steam byproducts. The idea that injecting 2% and less water into the induction charge is going to contribute to corrosion is flawed at best - motors in high humidity climates would corrode just as fast in that case.

Glassman's work shows that water is very active in the combustion process - the reactions it plays a part in are plenty fast enough. Evaporation and combustion are not instantaneous but under compression it is much faster than you are giving it consideration for.

 

[glueontop]

the thing is that the humidity present in the air at the intake is already in the gaseous phase, so it doesn't have to vaporise.

the second point is that the gasoline that you take at the pump contains a certain amount of rust inhibitor additive that is based on the average climate where it will be used. So it already takes into account a certain amount of water present in the mixture.

I think that adding water to the intake mixture is a good idea, but not in a conventional engine. Keep in mind that most people want an engine that last for at least 200K Km, without any major problem.

finaly, a large portion of those who own a car live in a place where there is a risk of freezing. So good luck with your water tank in the trunk, and your first starting in the morning when the valves and the pistons are frozen! If you realy want to save on gas, buy a smaller car.

 

[Andy330hp]

As for the testimonies, the obvious flaw with the "more power on rainy days" anectdote is they are missing the fact that most rainy days are also COLD days. That's where any power increase came from

 

[patprimmer]

If you add some ethyl alcohol to the water, it will substantially lower it's freezing point.

There is often free condensed water laying in the exhaust system of cars that are only used for short, low speed trips.

This water is a major byproduct of the combustion of hydrocarbons. The extra added by a water injection system, that is designed to only activate at low manifold pressures, will be insignificant, and will mostly only be added in circumstances where enough heat is being generated to clear out the water in the exhaust.

The ways to stop exhaust corrosion in cars with water retention problems are:-
use the car harder and longer. This might not be acceptable to the owner.
Drill a small hole at the lowest point of any puddles of water. This might generate a small but anoying noise, but the muffler will last a lot longer.
Locate the muffler closer to the engine.
Use stainless steel in problem areas.


Regards
pat

 

[turboice]

Methyl alcohol is a bit easier to obtain for water injection since it is a primary component of windshield antifreeze solutions and gas anti-freeze like the yellow bottles of heet.

Additionally at least one study has shown that methyl alcohol mixed with water provides more knock suppression than water alone. Good mixture testing reference:

http://naca.larc.nasa.gov/reports/1945/naca-report-812/

Also methyl alcohol is a fuel.

I use 50/50 mixtures year around.

Lastly some pumps and other components are negatively affected by ethyl but not methyl.

And you are dead on about the true source of exhaust rust (retention of liquid condensation rather than the passage of steam) and the solutions.

Ed.

 

[patprimmer]

Methyl and ethyl alcohols have VERY similar properties, as they both have the same functional groups, and basic structure. Methanol being the smaller molecule tends to react in the same way as ethanol, but a little more aggresivly

Over here (Australia) ethyl alcohol is easier to buy. We don't normaly encounter freezing conditions, so antifreeze is not always avaliable, other than glycol based coolant that is.

Ethanol is avaliable from supermarkets, garages, corner stores etc as Methylated Spirits, or in some countries I think it is called denatured alcohol.

Both work fine, both are fuels, both increase octane, but methanol does it a little more, both mix well with water, both can cause corrosion problems with aluminium fittings, but methanol is substantially more reactive in this regard. Ethanol requires a weaker A/F ratio than methanol, so it will nor enrich your mixture quite so much. Both burn very clean.

Also, ethanol is somewhat less toxic, in fact many people deliberately drink it regularly. It is actually more toxic than many realise.

It really comes down to whats easiest and cheapest to get.

I hope I havn't rambled on to much.

Regards
pat

 

[turboice]

Nope you are right that we (or at least I) need to appreciate the availability of alcohol types in other regions.

The pumps I use can take 50% methanol but no more than a few percent of enthanol or isopropyl. Other pumps can take much more concentrations of alcohols. The issue is the seal material and how it reacts to the particular alcohol. While ethanol and methanol have many similarities just like heptane and octane have very different characteristics from a couple molecules so do ethanol and methanol.

And yes methanol is highly toxic if ingested - but is safe to handle in the manners being discussed here. Ethanol is highly controlled in the States exactly because it can be ingested - toxins are freely available though.

 

[glueontop]

If you surf the net you will find at least a hundred pages of people who claim they have built a thousand HP engine running on water, or the story of a guy who was killed by petroleum companies because he invented a water running engine. In fact water contains no energy and cannot be burned. This is a dream!

What is one of the first thing they do with crude oil at a rafinery? they remove water. What is one of the last thing they do with gas before it leaves the rafinery? They put corrosion inhibitor and anti-coalescer addithives. These steps cost hundreds of millions of dollar a year to the petroleum industry. If water in an engine was not an issue, they would keep there money.

There is two laws of thermodynamic that explain what appends in a combustion engine. The first is the ideal-gas law PV=nrT. It says that in order to increase the pressure in a vessel, you have to increase the temperature. So at any point in time after the explosion, you want to have the highest temperature in the cylinder to get the maximum power. If you add water, a part of the explosion energy will be used to heat the water, this will reduce the temperature of the reaction and thus, the pressure in the cylinder.

The second law is the Otto cycle. It says that in order to increase the efficiency of an engine, you must increase the temperature difference between the time before and after the explosion and/or increase the compression ratio. Both are limited by the gas quality available. Water doesn't contribute in any way to the achievement of these goals.

These laws have been proven time after time for at least a hundred year. No one has ever prove them wrong, and no one ever will.

 

[funnelguy]

Andy330hp,
You must have missed my earlier post. We were on a Stuska water brake dyno. An aberration caused a unexpected increase in torue. Same day, same air temp, same everything except we found a leak in an intake runner. The builder was sharp enough to shut down and was not really surprised when we reported the leak to him. Water temp was probably right around 195F. Maybe 10% antifreeze with a little water pump lube added.

The caveats here are that we were dealing with an engine on the edge of detonation and that a 2% gain would have been big news. Fuel was 114 octane gas and air temp was above 90F. The leak only would have affected one cylinder, and yet the torque increase was noticed and reacted to by the builder.

Isn’t humidity one of the correction factors for normalizing dyno figures?