# 5 stroke engine



## gg89220 (Jun 5, 2020)

hello
new project with this original engine


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## gg89220 (Jun 7, 2020)

hello
cylinders and outer liners


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## gg89220 (Jun 12, 2020)

hello
the rest of the parts with the casing, the crankshaft and the timing gears


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## RonW (Jun 13, 2020)

Ok. I give up. What makes this a FIVE cycle engine. In the mockup I only see four cycles. What am I missing? 
Ron W


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## awake (Jun 13, 2020)

I wondered the same thing. The two outermost cylinders appear to be a standard 4-cycle, but if I'm seeing the video correctly, each of them exhausts not to the air but into the central cylinder, pushing it down; I'm not sure but I think maybe the idea is that the mixture is still burning at this point ... ??


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## gg89220 (Jun 13, 2020)

the central piston receives the pressure of the exhaust gases from the external cylinders, going up it evacuates it is the 5th time


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## Peter Twissell (Jun 14, 2020)

This is a technology currently being explored for automotive engines. Using exhaust gas pressure to drive the crankshaft directly.
I have seen a configuration in which a 4 cylinder engine can run in the conventional way, but also has the ability, via variable valve timing and additional valves between cylinders, to become a 2 cylinder engine with the other 2 used to scavenge residual exhasut gas pressure.


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## Steamchick (Jun 14, 2020)

Hi, I think the technical analysis is that there are a total of 10 strokes per 1 complete cycle (2 crank revolutions) on a real 5-stroke engine. But if you count this engine, I think there are 4-strokes in a primary cylinder, with an extra 2-strokes of the secondary cylinder appropriate to the primary cylinder, associated with each combustion charge. Therefore I would call this a 6 stroke engine. I have seen this engine schematic on u-TUBE, but can't  recall how I searched and found it. I think Peter is correct in that some manufacturers have investigated this configuration historically. 
But one of the things I learned working for a car maker, was that if it would make money we would do it, otherwise we wouldn't invest in developing it. This engine may appear thermodynamicallying efficient. But as we live in a world of regulation, where we practice making muck then cleaning it up afterwards, the exhaust on today's  vehicles is required to be hot, so to set the catalysts working that clean-up exhaust emissions. In this engine, I understand the second expansion will cool the exhaust so the CO will cease to burn, so it will need an external heat source to re-heat the gas to above 350 degrees C so the CO will burn to CO2. This in turn needs the catalyst to be heated over 650 C to get it to ignite the CO. The same argument applies to Hydro-carbons. If the primary cylinders  run over 90 then the Nitrous oxides will be formed in nasty quantities, thus requiring NOx after-treatment. But I guess as a model none of that will be needed so this is purely academic.
I interesting thread!
Enjoy.


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## Steamchick (Jun 14, 2020)

My mistake, should read 5-strokes,  not 10! Bet you spotted that one!


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## gg89220 (Jun 21, 2020)

hello
machining of the central cylinder and its liner, valves, guides and cylinder heads


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## Steamchick (Jun 22, 2020)

Beautiful work!
I hope it runs as planned! 
Well done!


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## Peter Twissell (Jun 22, 2020)

Are the valves made from CSK screws, or did you cut the form into the heads?


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## gg89220 (Jun 22, 2020)

from csk screws


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## Peter Twissell (Jun 22, 2020)

I know there are some very hard steel screws available for driving directly into masonry.
What screws did you use?


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## gg89220 (Jun 22, 2020)

to machine the throat of the clip I heat red and let cool slowly


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## Kevork BOYACIYAN (Jun 29, 2020)

Are you trust the radius of that screws? Although it is a practical solution I know that the heads of the screws are made by pressing, not on turning machine. There is a possibility that each of them is of different diameters or eccantric. Still it will probably works.


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## gg89220 (Jun 29, 2020)

hello
I rotate the rod round and I give a small pass with the grinding wheel


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## gg89220 (Jul 5, 2020)

hello
provisional assembly


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## Peter Twissell (Jul 6, 2020)

Looks nice and I've no doubt it will run.
It may be interesting to measure the engines output with and without the '5th stroke' cyclinder active. Maybe first run with the middle piston and rod removed and exhausts from 1 and 3 open to atmosphere?


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## Steamchick (Jul 7, 2020)

I have never seen a valve ground like that - but well done if it works for you. I have only used a Delapena Valve grinder, where the stone traverses along the tapered angle required.  Typically, 45 degrees for half the face and 46degrees for the other half, so the line between the 2 tapers forms the specific sealing line which is lapped against the seat until the appropriate seat width is made. (Too narrow and it may indent the seat before it laps properly, too wide - e.g all one angle - and the lapped ring may be on the inner or outer edge of valve or seat, depending on how the valve taper matches the seat taper). Perhaps your model is small enough to be insensitive to seat accuracy? - But I guess it may be more sensitive? You'll see when it runs.


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## gg89220 (Jul 17, 2020)

hello
distributor interrupter ignition and valve cams


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## gg89220 (Jul 31, 2020)

hello
here is the finished engine


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## awake (Jul 31, 2020)

Very nice! Do you have a video of it running?


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## LSEW (Jul 31, 2020)

In the years leading up tp 1888, a French engine builder, Fernand Forest, resarched and
built a similar engine. It was a standard 4 cylinder, but with a 5'th larger cylinder 
for exhaust expansion.It was ported so the exhaust from one of each of the cylinders 
would enter the expansion cylinder, either on top or bottom of the piston, for each 180 
deg. stroke.Porting  also allowed exhaust to exit from the other side of the piston from 
the expansion cylinder on the same stroke.Thus each stroke had an expansion cycle and 
an exhaust cycle from the expansion cylinder.

It is speculated that the idea was borrowed from the triple expansion steam engine. 
Unfortunately the expansion of steam and gas from combustion are very different. So it seems from the disappearance of this type IC engine cycle, it was a bad idea. The engine was built by Fernand Forest and his partner George Gallice in 1888 according to an entry in book 2  of the C.H. Wendle series. There is also a wonderful picture of an etching of this engine There.

Very nice work on the model, I hope it runs well, waiting for the video

maury


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## gg89220 (Aug 1, 2020)

hello
here is the video


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## Steamchick (Aug 1, 2020)

JUST MAGIC! Well done Sir!
It idles better than my V50 Moto Guzzi.... You have made a smashing model. 
Just one small detail, before it wears out, how is the lubrication managed? No sign of oil splash anywhere. How so?
Do the bearings stay cool enough because it is all in the open air?
Also, I know that air cooled motorcycles with in-line twins could overheat the rear cylinder... furthest from the draught of fresh cool air. (Longitudinal crankshaft for convenience for shaft drive as with the Sunbeam twins).
Do you have any way of knowing if the expansion cylinder is able to do any work? E.g. by pressure and temperature measurements of the gases into and out of the centre cylinder? Or pressure measurements within the cylinder? It would probably need a high speed pressure transducer and data capture to gather that info to really understand if it is useful.
Again - well done! 
K


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## Peter Twissell (Aug 1, 2020)

An easier way to assess the value of the middle cylinder would be to run the engine with the two short link manifolds removed.
If it can drive a moderate load (e.g. a prop) at a measured RPM and a known throttle setting, then compare RPM with the manifolds replaced.
If a suitable RPM meter (e.g. optical type) is not available, just record the sound for comparison.


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## Cogsy (Aug 2, 2020)

Peter Twissell said:


> An easier way to assess the value of the middle cylinder would be to run the engine with the two short link manifolds removed.
> If it can drive a moderate load (e.g. a prop) at a measured RPM and a known throttle setting, then compare RPM with the manifolds replaced.
> If a suitable RPM meter (e.g. optical type) is not available, just record the sound for comparison.



I'm not sure about this method. Exhaust tuning can have a lot of impact on power production so changing the exhaust so much by removing the manifolds might make a lot of difference to power output and might not show the true effect of the middle cylinder. I'm certainly curious about how much power it's salvaging also.


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## Peter Twissell (Aug 2, 2020)

I agree that changing the exhaust will change the engines performance. In this case, the middle cylinder is the exhaust tuning and that is exactly what we are interested in.


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## coulsea (Aug 2, 2020)

If an engine design was economically efficient you would be able to go out and buy one. This one is a huge success because you found a design that interested you and built one that runs, with a great background story for interested viewers. I am always amazed at the endless possibilities of this hobby. keep up the good work.


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## Steamchick (Aug 2, 2020)

Stupid me. A simple comparison using a propeller - must get a propeller! I estimate relative performance of different steam engines by comparing speed against a constant load. (Bicycle Dynamo). But I like the theory as well as the top models and simple toys. I am interested to know how much difference the extra cylinder makes, however that is determined. The Institute of Model Engineering does conduct engine testing on dynos, and temperature and pressure recording , from what I have read, but few individual model makers do that. Yet, to me at least , it seems a natural development of the hobby. And while this thread is meant to be about "model engine machining" I have been an engineer for too long just to focus on machining the bits. One of my "round-tuit" notions is to make a dyno... does anyone have plans? (2 spring balances and a leather belt on a pulley?).


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## awake (Aug 2, 2020)

Beautiful! Sounds great!


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## coulsea (Aug 2, 2020)

Steamchick said:


> One of my "round-tuit" notions is to make a dyno... does anyone have plans? (2 spring balances and a leather belt on a pulley?).


google Prony brake, it would seem to be a fairly easy way to measure horsepower, I think that there may be posts on this forum somewhere.


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## Canyonman (Aug 2, 2020)

Hello    Maybe I missed it but are there plans available?   Thanks    Ken


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## gg89220 (Aug 3, 2020)

hello
I made the engine without a plan


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## NapierDeltic (Dec 17, 2020)

Hi gg89220.
I very much appreciate your project. I think you are only at the middle of it. There's no doubt that an IC linked with a compressor will work, especially if mechanical chain is reduced to a minimum. Please go further!
I know you want to prove yourself something and I'm preety sure we are some who would like to see this proof (I mean we are interested in technical aspect and we also appreciate your personal /emotional involvement in it).
In my honest (and modest) opinion you should increase valves diameter. As small as they are now they are strangling the IC side and maybe also the central cylinder. I think the power recovered by third piston has to be quite less compared to the others and gas flow efficiency affects this smaller percentage. Every effort to use otherwise wasted energy is worthed. If efficency testing you intend -and we wait -will show 1.00 per cent gain you'll hear a lot of "told you it's meaningless"! I think modifications are not that substantial and I have seen a lot of skill in your already built parts.


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## Steamchick (Dec 18, 2020)

gg89220 said:


> hello
> here is the video



Just watched it again... Made me smile - again! I had a thought about checking to see what effect the middle cylinder has....? Maybe if you removed the exhaust valve push-rods from the middle cylinder, then wedged the exhaust valves of the middle cylinder so they are fixed open, and then checked the speed at the throttle setting for a known speed when "as designed". If using something like an aero-prop as engine load while doing this, especially if you record the comparison on video and analyse the enginer speed, then you should be able to get a reasonable estimate of the increase of efficiency when the centre cylinder has exhaust valves operating. Speed versus aero-prop is a simple square function. (Air-drag is proportional to the square of the speed).  The musical "note" from a 2-bladed prop in hertz relates to twice the rpm. I'm sure between us we can help if you need it.
Keep on experimenting - maybe even publish results on Wiki - is some success? Having worked on Engine design in Nissan, the big engine makers are all working flat-out to improve efficiency, low emissions and cost of engines, and their relatively vast resources will always win (just look at Toyota, Daimler or GM!!). But nothing to stop you doing a study on your engine and publishing - if you choose!
Well done!
K2


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## vederstein (Dec 18, 2020)

The five stroke engine is an old idea made new again.

In the steam era, it was called compounding with high and low pressure cylinders.

Also in the steam era, it was done with a single cylinder and called early cut off.  Corliss engines did this.

Early cut off was also used in the internal combustion era.  The atkinsons cycle which has a short intake stoke, but a long power stroke.

The whole reason is to extract as much energy from the expanding gasses before dumping them out of the engine.

Thermodynamics doesn't change.

...Ved.


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## Steamchick (Dec 18, 2020)

vederstein said:


> The five stroke engine is an old idea made new again.
> 
> In the steam era, it was called compounding with high and low pressure cylinders.
> 
> ...


And Toyota et al are trying to utilise this effect in today's designs of engines.... 
But turbo-chargers utilise some of the "spare energy" in the exhaust gases to improve the intake (by boosting) - and Turbo-manufacturers have exploited exhaust gas "energy" with alternators as well.... 
I had a discussion with a Doctor of Mech. Eng. from Sunderland Uni who was investigating fitting a steam boiler just downstream of the catalytic converter of a car engine to see how much power he could derive from hot low-pressure exhaust to power a steam engine driving an alternator - as a project for a post-graduate. This system could also be used to extract energy from the hot, low pressure exhaust from Fuel cells. I think the post-grad was expected to produce a numerical model for computing all of this, and then compare his model to a real set-up.
But it is a distraction from the real "5-stroke' engine here.
K2


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## NapierDeltic (Dec 18, 2020)

There are various methods to extract wasted energy from an engine both from gas pressure and thermal gradient. The recovered energy is quite low compared to already existing output.
Of course I don't expect big engine manufacturers to go in all directions, considering price increase and engine complexity, but engine lovers are allowed to release the dogs of their imagination.
For instance new Peltier semiconductor elements become cheaper,  widespread available and more effective and they can recover a lot of waisted heat. Well, Peltier cells are not something to atract machining lovers... , but their output is certain.


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## vederstein (Dec 19, 2020)

I was continuing to think about this engine that GG created.

First of all sir, congrats on such a cool design and without any plans!  So what I say isn't any type if criticism on your work, I'm just pondering ways of making engines more thermally efficient.

There's a company that's working on a crazy efficient opposed piston two stroke diesel engine.  Per the video below, properly outfitted, they're approaching thermal efficiencies of around 50%.  This is phenomenal!!  (For example a gasoline engine in a car is about thermally 25% efficient.  A nuclear power plant about 35% efficient.  A steam locomotive about 5% efficient.)

I was thinking of an addition to this engine and again it's not a new idea.  In fact, this idea was used in WWII aircraft engines:  Water Injection.  Just after ignition, inject a small amount of water into the engine.  The heat of combustion will then not only push the pistons apart, but will create steam to push on the pistons as well.

The balance would be to inejct only enough water to counteract the amount of heat removed via a traditional water jacketed cooling system.  What I'm envisioning would have no cooling system.  What is currently waste heat would be converted to steam to push on the cylinder creating power.

Also, If the engine could run about 150 celsius with the exhaust the same temperature, opportunities abound for weight reduction.  There are industrial plastics that can easily withstand these temperatures which would replace what are now metal components.

Comments?

...Ved.


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## Anatol (Dec 19, 2020)

Ved

when I was a college - in Australia - there was talk of hottrodders using water injection to increase compression, so its a known technology. Seems obvious, I've always wondered why I've never seen it used commercially. Wikipedia - of course - has page on it (this is why I give money to Wikipedia). Turns out it was used in aviation and is in currently active development "In 2015 BMW has introduced a version of their high performance M4 coupe, the M4 GTS, that combines water injection with intercooling."

Another post noted the similarity to the steam compound engine, as a method of energy scavenging. I've been thinking about compounds again recently - has anyone here built one? They went out of fashion as faster uniflows took over, but stayed relevant for big stationary and marine applications - a couple of Great Lakes ferries (still?) use them. 

Love the opposed piston engine! Clever use of ports for both inlet and exhaust! But again, (afaik) the two-stroke exhaust port was an adaption of the prior and well developed steam uniflow design. 

hmmm, just noticed this is a very old thread.


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## Steamchick (Dec 20, 2020)

I would like to counter your hypothesis of water injection using thermodynamic  theory... .but I don't  know enough to even try. And if BMW are doing something they have the expertise (and money!) that would support your ideas. But I do think Otto (a very clever lad!) got it right with high compression - synonymous  with high temperature  - for efficiency. So I am strugging to understand how water-injection to combustion chambers can increase effecency? It doesn't add energy so how can it increase power?
But late water injection (perhaps after the catalyst?) to cool exhaust could extract more heat.. or rather cool the gas flow by making low pressure steam from added water, but at the expense of water handling equipment.. and I can't figure how to extract the power from low temperature, low pressure steam and gas at very high volumes...? But BMW have some reason... "better men than I"...
K2


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## Richard Hed (Dec 20, 2020)

Anatol said:


> Ved
> 
> when I was a college - in Australia - there was talk of hottrodders using water injection to increase compression, so its a known technology. Seems obvious, I've always wondered why I've never seen it used commercially. Wikipedia - of course - has page on it (this is why I give money to Wikipedia). Turns out it was used in aviation and is in currently active development "In 2015 BMW has introduced a version of their high performance M4 coupe, the M4 GTS, that combines water injection with intercooling."
> 
> ...


There was a man who developed a 6 stroke engine that had four conventional strokes for gasoline and two strokes for water injection which cooled the engine and of course created steam pressure.  The engine did not need a radiator system, nor was it air cooled.  I don't know what happened, I suspect the felllow died.  I'll see if I can find the stuff to show you.


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## Anatol (Dec 20, 2020)

Steamchick said:


> Today at 8:56 AMI would like to counter your hypothesis of water injection using thermodynamic theory... .but I don't know enough to even try.
> 
> I am strugging to understand how water-injection to combustion chambers can increase effecency? It doesn't add energy so how can it increase power?



I'm not an applied physics PhD or engineer either, but my intuition (which can often be wrong) is that hot exhaust gas is wasted energy. Using that heat to turn expand atomised water into steam, thus creating extra compression in the cylinder.


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## Steamchick (Dec 20, 2020)

OK... I hear you but I don't understand. Does it mean that the "exhausted heat energy" is actually less if you add the water during the power stroke? - Or just more molecules at a lower temperature? Because (with my limited brain and education) - the heat "energy" is the compound of mass and temperature... not temperature alone. (Anyone understand thermodynamics to help us understand this one?). I would have GUESSED that injecting water into the combustion chamber part way through the power stroke would lower the pressure by cooling the combustion gas. Below 350 deg C it stops burning (and releasing chemical energy as heat). So I suspect it may work on an engine at very high output (full throttle)  but not at lower powered conditions - which is possibly why it has been used as you suggest. Also, modern engines for road use (maybe not large marine plant etc.) need catalyst exhaust after-treatment - which needs to be up around 600 deg. C to ignite and function as a 3-way or 2-way catalyst. So cooling the exhaust means dirtier exhaust.... contrary to many National laws since the mid-1970s. As a lad... - before catalysts in exhausts were thought of... - I was taught that cars and motor-bikes run better in damp air - but this was explained as the cooler intake air, being cooler at point of ignition, so less susceptible to pre-ignition, as well as the combustion being slower as it was heating a tiny amount of water as well as the fuel and air, which again reduces the chance of pre-ignition.
Teach me more please, I'm curious to improve my understanding!
K2


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## Anatol (Dec 20, 2020)

>  (Anyone understand thermodynamics to help us understand this one?).

Don't take my notes as anything but idle speculation over a beer... 

> I would have GUESSED that injecting water into the combustion chamber part way through the power stroke would lower the pressure by cooling the combustion gas.

so - any conversion of water vapor to steam will increase pressure, and ... I don't know if the pressure generated by combustion is due to thermal expansion of combustion products or if combustion produces bigger molecules (that sounds about as juvenile as my understanding of combustion chemistry/physics is). 

> Also, modern engines for road use (maybe not large marine plant etc.) need catalyst exhaust after-treatment - which needs to be up around 600 deg. C to ignite and function as a 3-way or 2-way catalyst.

> I was taught that cars and motor-bikes run better in damp air 

I heard this too. But the explanation I heard was that excess heat turned water vapor into steam, creating more pressure in the cylinder and cooling it at the same time - but I'm repeating myself and repeating stuff I heard 30+ year ago.

Actual thermodynamics engineers, please chime in


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## Richard Hed (Dec 20, 2020)

Steamchick said:


> OK... I hear you but I don't understand. Does it mean that the "exhausted heat energy" is actually less if you add the water during the power stroke? - Or just more molecules at a lower temperature? Because (with my limited brain and education) - the heat "energy" is the compound of mass and temperature... not temperature alone. (Anyone understand thermodynamics to help us understand this one?). I would have GUESSED that injecting water into the combustion chamber part way through the power stroke would lower the pressure by cooling the combustion gas. Below 350 deg C it stops burning (and releasing chemical energy as heat). So I suspect it may work on an engine at very high output (full throttle)  but not at lower powered conditions - which is possibly why it has been used as you suggest. Also, modern engines for road use (maybe not large marine plant etc.) need catalyst exhaust after-treatment - which needs to be up around 600 deg. C to ignite and function as a 3-way or 2-way catalyst. So cooling the exhaust means dirtier exhaust.... contrary to many National laws since the mid-1970s. As a lad... - before catalysts in exhausts were thought of... - I was taught that cars and motor-bikes run better in damp air - but this was explained as the cooler intake air, being cooler at point of ignition, so less susceptible to pre-ignition, as well as the combustion being slower as it was heating a tiny amount of water as well as the fuel and air, which again reduces the chance of pre-ignition.
> Teach me more please, I'm curious to improve my understanding!
> K2


Most materials have a "latent energy" which is an amount of energy that it needs to either melt or solidify  or boil or condense.  What this is is say for ice, ice melts at 0deg (or 32) but once the ice warms up from say -10 deg, to 0, it still takes MORE energy to actually melt still at 0deg.  Same for boiling.  For different materials, this energy is more or less than other materials.  Water is very high.  So for this reason when liquid water is atomized into a hot situation, it will cool the thing just in taking up the necessary energy to vaporize.  However this has a good point to it in that it acts the same way alcohol in the gasoline acts, that is, it acts like octane which slows the burning of the fuel down to a point where it does not "explode" or knock the engine and thus adds engine life.  Once the water passes the point where the necessary energy has overcome the latent energy needs, the water vaporizes and acts exactly as steam pressure does in a steam engine.  Of course the exhaust is cooler, but I don't know how much cooler.  I don't belileve you would want to put your hand in it for very long.   Once the water is vaporized, it expands rapidly and easily with much less energy, as it is the Van der Waals forces which cause the high latent energy needs to vaporize.
There are other factors involved which I doesn't know much about.  This is probably onlhy a partial explaination.


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## Steamchick (Dec 21, 2020)

I'm a "simple physics" student (alias engineer) - and not too "hot" on chemistry and thermodynamics. But recognising it takes a lot of the heat (i.e. energy in the kinetic oscillations of the molecules) released from the chemical interaction of the fuel gases (combustion) to even vaporise the injected water, that will cause a significant pressure drop in the combustion gases. The water droplets will boil to steam at the elevated temperature matching the pressure in the combustion chamber, but as this pressure is dropping as it expands with the piston the newly created steam will condense back to water, so will only give back some of the energy that it took from the combustion gases. I can't see anything to "increase pressure" as you suggest... and it is pressure that transfers energy from gases to pistons. The net effect I can see is that injected water will capture some heat (= energy) and carry it out with the exhaust. I.E. less efficient than no water injection. So I still don't understand the reason for it. But I am not as clever as BMW and others... ?
Sorry, I can't  say more than that.
K2


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## vederstein (Dec 21, 2020)

As I wrote earlier, some WWII aircraft engines used water injection to get a power boost when needed (e.g. take off, dog chasing, etc).

Some of the points here are valid and injecting too much water can have detrimental effects on power by absorbing too much heat.  As far as my feeble mind takes me (I had Thermodynamics courses some 27 years ago), the maximum water you'd want to inject and be vaporized would equal the heat that would otherwise be removed via the coolant.

I didn't attempt to calculated it, but my gut tells me for each power stroke, you're not really talking about large amounts of water.

For the most _efficient_ (not necessarily powerful) engine, you want the pressure in the piston at the bottom dead center to be at or nearly atmospheric pressure.  This would indicate that all available energy was extracted from the fluid and transferred the crankshaft.  Ergo, the lowest exhaust temperature would be no less than the boiling temperature of water at that altitude.  (about 100C)

...Ved.


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## Steamchick (Dec 21, 2020)

vederstein said:


> As I wrote earlier, some WWII aircraft engines used water injection to get a power boost when needed (e.g. take off, dog chasing, etc).
> 
> Some of the points here are valid and injecting too much water can have detrimental effects on power by absorbing too much heat.  As far as my feeble mind takes me (I had Thermodynamics courses some 27 years ago), the maximum water you'd want to inject and be vaporized would equal the heat that would otherwise be removed via the coolant.
> 
> ...


As I said, I hear what you say, but I don't fully appreciate the maths or whatever, so (like a lot of clever ideas?) I hold my hands up and say "don't  understand". An alternative idea may be that with supercharged engines in WW2 aircraft (to avoid loss of power at altitude, as well as improve max power when needed) the fuel would detonate (pinking or pre-ignition) at high boost, but water injection would delay the pre- ignition point so they could run a higher boost and revs with water injection. I.E. A combustion versus boost issue, not efficiency related? If water injection was for fuel efficiency, I can't  understand "why" they used it at times of needing max power, as you describe? Dog-fighting and take-off. However if it was for fuel efficency, I would guess they would use it in cruising-mode to increase the range of aircraft...?
But I a guessing!
Any more ideas?
K2


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## Steamchick (Dec 21, 2020)

Hi Ved, just re-reading your earlier message, and it confused me by "increasing pressure while reducing temperature" ??
I thought pressure and temperature were intimately related (PV=RT ?)?Except at the triple point, or when changing state.... but the boiling point of water changes with pressure.... so surely the only condition for water and steam to exist is with temperature increasing with increasing pressure? You've got me really confused here... Hence " I don't  understand" message...
K2


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## ShopShoe (Dec 21, 2020)

RE: Post #51, above:

That is what I have understood about water injection.

Many years ago, the U.S. TV network CBS featured an episode of their "60 minutes" magazine show (I think) in which they attempted to "one-up" a factory car to provide both reduced emissions and improved performance (of the day). The race-car builders they employed to do that added water injection to a stock Ford Fiesta (or was it a Festiva?) and possibly demonstrated it to work, but with the problems of inconvenience for the driver and reduced life of the engine.

My late father, who was a Navy carrier pilot in WWII, watched that program with me and commented that some of the planes he flew had water injection, but the pilots were instructed to use it very sparingly as it would cause other problems in the engines. 

FWIW,

--ShopShoe


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## Steamchick (Dec 21, 2020)

Thanks Shop Shoe. That information is worth more than you may appreciate. As US and UK had higher Octane fuel than Germany, and Japan, I had guessed it was a German thing born of an anti-knocking additive when boosting higher than normal for the engine. But if the USAF used it then probably I am wrong? - I think the UK were supplying Lead additive back across the pond to the US as the UK were big users and manufacturers of lead additive. And it was needed for the higher powered engines with supercharging. (e.g. Merlins made by Pratt and Whitney for USAF). I believe all of these tales - I just don't understand (Technically) "why inject water?" and "how it works?".
But I'll find out someday, when it becomes more important to know. 
Just now I have "steam boilers" on the brain, as I have a old built boiler - that refuses to seal... - My problem - just the technique of trying to get it warmed reasonably uniformly when 3/4 buried in sand.... and using a few blowlamps. I seem to stress the boiler upon cooling - so any tiny flaws in the silver solder cause a crack - or where I repair on odd spot a pin-hole appears nearby - probably from some new dirt migrating into the joint....?  Always seems to be right about the edge of the flame that made the repair.... And I can't see the pin-holes with the naked eye, but they do show tiny bubbles under soap with air pressure. I suspect a "cold-lap" condition where the liquidus meets solidus in the repaired joint.
Thanks again for tales of water injection.
K2


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## Richard Hed (Dec 21, 2020)

Steamchick said:


> Thanks Shop Shoe. That information is worth more than you may appreciate. As US and UK had higher Octane fuel than Germany, and Japan, I had guessed it was a German thing born of an anti-knocking additive when boosting higher than normal for the engine. But if the USAF used it then probably I am wrong? - I think the UK were supplying Lead additive back across the pond to the US as the UK were big users and manufacturers of lead additive. And it was needed for the higher powered engines with supercharging. (e.g. Merlins made by Pratt and Whitney for USAF). I believe all of these tales - I just don't understand (Technically) "why inject water?" and "how it works?".
> But I'll find out someday, when it becomes more important to know.
> Just now I have "steam boilers" on the brain, as I have a old built boiler - that refuses to seal... - My problem - just the technique of trying to get it warmed reasonably uniformly when 3/4 buried in sand.... and using a few blowlamps. I seem to stress the boiler upon cooling - so any tiny flaws in the silver solder cause a crack - or where I repair on odd spot a pin-hole appears nearby - probably from some new dirt migrating into the joint....?  Always seems to be right about the edge of the flame that made the repair.... And I can't see the pin-holes with the naked eye, but they do show tiny bubbles under soap with air pressure. I suspect a "cold-lap" condition where the liquidus meets solidus in the repaired joint.
> Thanks again for tales of water injection.
> K2


The point abougt a "small" amount of water is that it is a "tiny" amount which doesn't take as much heat out as you seem to be thimking.


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## Larry G. (Dec 21, 2020)

Steamchick said:


> Thanks Shop Shoe. That information is worth more than you may appreciate. As US and UK had higher Octane fuel than Germany, and Japan, I had guessed it was a German thing born of an anti-knocking additive when boosting higher than normal for the engine. But if the USAF used it then probably I am wrong? - I think the UK were supplying Lead additive back across the pond to the US as the UK were big users and manufacturers of lead additive. And it was needed for the higher powered engines with supercharging. (e.g. Merlins made by Pratt and Whitney for USAF). I believe all of these tales - I just don't understand (Technically) "why inject water?" and "how it works?".
> But I'll find out someday, when it becomes more important to know.



General Motors marketed production vehicles with water injection, solely for the purpose of knock prevention. The idea and application of higher compression engines was successful but the program was abandoned because of... USER FAILURE.  Owners failed to add the required alcohol antifreeze to the injection water tank, allowing it to freeze, allowing the engine to knock itself to death in cold-weather climates.  I had ordered research papers from SAE, before internet service.


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## Steamchick (Dec 21, 2020)

Thanks Larry,
That explains a lot.
Thanks Richard. I think that your "small amount of water" makes sense with Larry's comment. I think this is a more reasonable  explanation for hot-rodders et al using it, as Anatol mentions. The idea of cooling engines and steam generation transferring more power to the piston - as the 6 stroke engine - sounds intriguing... this one is on Science direct so I'll read and learn.
Thanks all.
K2


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## NapierDeltic (Dec 21, 2020)

Hi,
Kerosene flame temperature is about 2400C , steam cycle high temp is slightly above 500C. There were some industrial applications of topping cycles (many retrofit in stationary plants) based on liquid metal (mercury or other) to intermediate the difference between the 2 temperatures. there were some (succesfull) trials with organic fluids to use wasted heat in steam cycles. Both were based on  Rankine cycle and the overlap is named cascade cycle. So there is no real, completely "waste heat"
I have spoken about Peltier elements not because I am necessary a fan of them, but because having a theoretical efficiency much lower then Carnot cycle they still proof a real positive, tangible, output. And thermal cycles can do more! It is not Fata Morgana.

About WWII engines , as I know, the water injection was done in admision and, especially for turbocharged motors, it was the simplest version of intercooling. Vapourising water induced low temperature of air, higher density, higher power. That's why is mentioned at takeoff, where air temperature is elevated and power need is high. Anti-knock effect could be a bonus. It does not improve thermal efficiency so no extra-range for the plane.

On another hand, in normal piston engine, after exhaust phase, if piston goes to TDC and you inject water (small amount and no admission) if cylinder wall temperature is elevated (600C is required by catalytic converter, but average - admit-is lower), what will happen with water? I would say it expands 1600 times to vapour state, generate some pressure and pushes the piston down generating output. This is the 6 stroke cycle. For 5 stroke cycle the things are a bit more complex-mixing 2 strokes in one-, and harder to model in someone's mind. But at least we can figure which are the pros and cons factors and how to block or favour ones or the others. And the main processes considered are quite the same as for the  6 stroke, where there is a gain, as I have mentioned.

Anatol is right in that point and I ask myself how much power comes in IC from thermodynamics and how much from phase change - chemical reaction from liquid fuel IN to gaseous exhaust OUT.
Equal to how much expansion in explosives comes from exothermic reaction and how much from phase change of reactants? So how much IC engine is a pure thermodynamic engine.


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## vederstein (Dec 21, 2020)

Steamchick said:


> it confused me by "increasing pressure while reducing temperature" ??
> I thought pressure and temperature were intimately related (PV=RT ?)



Gas laws and steam tables are still in effect here, but I doubt the ideal gas law works.  Maybe I'm underthinking it, but an engine's cooling system is there to remove excess heat that would otherwise damage components.  If that heat went into vaporizing water, then the water vapor (steam) could be used to help push down a piston.

What's to remember here is assume the energy input (gasoline flow) is constant.  So we have a constant energy input (Q).  Per the first law of thermodynamics, that energy must go somewhere but it cannot be created or destroyed, just changed forms.  So an engine would be Q=E1 + E2 +E3 where E1=useful power generated, E2 = waste heat to the low temperature mass, and E3 = heat removed via other means (radiator).

I'm discussing taking some of E3, which goes through the radiator and use it to create a bit of steam instead.

From a thermodynamic perspective, you would never want to have a heat removed from the system except to the low temperature mass.  In the case of a gas engine, the low temperature mass is the exhaust.  The high temperature mass is the combustion.  The ratio between the two is the Carnot efficiency.  No heat engine can be more efficient at those temperatures.

Obviously there's more practical limitations to this.  The whole discussion here, though interesting, is a bit academic.

Speaking of the laws of thermodynamics, here they are in layman's terms:

1st law:  You can only get out what you put into it.
2nd Law:  You can't even get that.
3rd Law: Things always get messier unless you work to keep them organized.

...Ved.


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## Tim Wescott (Dec 21, 2020)

Steamchick said:


> ... I just don't understand (Technically) "why inject water?" and "how it works?".  ...



Particularly after reading the relevant Wikipedia article I'm pretty sure that 90% of the answer is "because it cools the incoming charge and prevents detonation", with a teeny bit of "oh, and it cools it (like an intercooler) so you can stuff more charge in there".

It's one of the cited advantages of using alcohol fuel over gasoline -- alcohol vaporizes readily, but has a high heat of vaporization.  So the charge filling the cylinder is cooler, and thus contains more molecules at the same pressure than it would be otherwise.


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## Steamchick (Dec 22, 2020)

Good stuff! Thanks all - as I find this very interesting. But my mind boggles when I read such things as the "Water gas shift reaction" - Water-gas shift reaction - Wikipedia - it is beyond my brain processing ability! 
I am aware (from working alongside the engineers that explained how the various components of "modern" car engine design contribute to efficiency and emissions improvements - some of only less than 1% taken individually). 

To reduce detonation, a key was the re-design of combustion chambers to reduce squish... 2 inlet valves, plus the intake tract to valve shape causes adequate swirl without complex squish zones, that would generate cold zones where  incomplete combustion could occur, and hotter zones more prone to detonation. Thus "unleaded" fuel - with different additives to reduce detonation - that are generally lower octane than the higher octanes used in the 1970s with lead additives - can be run at relatively high compression compared to engines from the 70s with the same octane fuel. Also electronic ignition delay with direct feedback sensor-triggered retardation eliminates any odd knock that may occur, thus allowing the ignition to be relatively "more advanced" than traditionally. In other words, the "anti-knock" retardation safety margin of pre-1980s engines was much greater than the margin applied today. Wikipedia explains this quite well, but on "modern" engines this would be much less useful as we have electronics and computer aided design that means manufacturers have countered problems that water injection was doing 70 years ago.
Reduction of the space above the top piston ring, and corners of combustion chambers (e.g. around valves) where un-burned fuel can occur, has been applied to reduce hydrocarbon emissions.
Introduction of Exhaust gas (EGR) to slow combustion rates and reduce high peak temperatures also reduces knock at the higher compression with lower octane fuels, and reduces NOx formation (keeping peak temperatures below 900 deg. C). I guess that as the Exhaust gas introduced by the EGR system has a percentage of water, mixed with CO2 and NOx, then it is in fact a form of "gaseous" water injection? - Which will aid the "water-gas shift reaction"? - Although I am aware that excessive EGR will generate excessive Hyrocarbons and CO in the exhaust that cannot be catalysed so cause emissions test failures - so MUST be avoided.
Efficiency improvements in where to cool the engine - and where to not cool it - so minimising cooling water heat losses. I think this energy "saving" - by not throwing away too much excess heat - is the industry's way of trying to redress some of Ved's Q=E1+E2+E3 balance? - Combined with the reduction of friction losses, etc.
Use of minimal contact pistons to reduce oil-shear drag losses...
Minimal crank bearing size to reduce oil-shear drag losses.
Finite element and fatigue analysis studies to minimise the materials everywhere. - Thus reducing dynamic loads and losses due to friction. (e.g. Reducing valve stem diameter reduces heat losses up the valve stem, and friction in the valve guide).
Many of these ideas Model Makers adopt "almost without thinking" when designing their own models... and some are very appropriate on models due to the scale problem - and the low power of model engines being more prone to "High" friction problems.
I hope some of my musings are helpful?
K2


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