Propane injection for diesel.

[kistinie]

I've just run my yanmar 1gm diesel with propane added as direct mix in the air inlet
Just a few is needed

Guess what happens ??? :

It start better without smokes
Run with an incredible torque, i would think increase much over 2x at low rev
Runs very low speed.
Exhaust cooled by water of the combustion
Much less smokes
:p

Drawback

:P ...it is a poison gas heavier than air, need to be careful :P
the fitting of a thermocouple on exhaust closing gas feed should be compulsory
Hydrogen injection is a serious competitor as energy for electrolyse can be sun or wind power
Works green till no sun and no wind.


kits can be found for hydrogen injection.
One example:
http://www.water4fuel4boats.com/5.html

Is there butane, propane...possible add-on ?

Diesel should be equipped for poly combustion of butane or propane, hydrogen, and of course oil.
Then they become true universal motors with a rise in total efficiency measured over 50%
The multi gas injector is the missing part of the puzzle.

[Landlubber]

Propane injection for diesels is certainly quite old technology, many shops in Australia have deen doing it for years, particularlly on small commercial trucks and 4WD.

[Frosty]

So if I fit an LPG tank and a small tap to feed gas into the intake I can feed in gas at a controlable rate and back off on the diesel. It would work like a cruise control.

I could use this on long distance travel.

[Landlubber]

Frosty,

I have a mate in Brisbane that used to do it full time for a living, I doubt that you simply stick a hose into the air intake..........PM me if you seriously would like to do something and I will give you his details.

[Frosty]

Lubber,thats all you do with hydrogen although they dont use the word "stick' they say tap it into the intake --infact anywhere.


Anyway Im needing a new truck that will have a warranty.

[apex1]

Propane injection for diesels is certainly quite old technology, many shops in Australia have deen doing it for years, particularlly on small commercial trucks and 4WD.

I was missing your comment on the 100% increased torque that was claimed!?;)

[Landlubber]

apex1,........somethings are best left unsaid.

The truth is though, the engines do have more user feely friendly touchy power.

[pistnbroke]

Frostys grasp of technology again amazes me ..when you feed hydrogen/oxygen into the inlet you are modifiying the combustion and all you produce is a cleaner burn not great wodges of power ...when you feed in butane or propane you are using this as a fuel in partnership with the diesel being injected .. Yes old technology used for years on combined harvesters ....

[Frosty]

Pistonbrokes inability to seperate one post from another amazes me.

Please indicate where I said feeding hydrogen/ oxygen into the inlet manifold produces wodges of power?

[pistnbroke]

frosty read your posts ...you imply or state that feeding relatively small unregulated quantities of hydrogen/oxygen from a generator into the inlet is as easy or equates with feeding in propane .....if you put too much propane in you end up with a gas(petrol) engine with a compression ratio of 22:1 and such hot exhaust gas that you burn the valves......

you also talk of cutting down the diesel ...err whats the fuel injection pump regulator do .....errr

[hartley]

If i recall correctly Benders bus lines in Geelong Vic were one of the first to use propane injection in their diesel buses ,the published accounts of this were all very positive ,this was at least 25 years ago ,so nothing new...
cheers hartley

[Frosty]

Pistonbroke --you read my post, it says " So If i" that is a question where I come from.

And where did I say it gives wodges of power or that I feed hydrogen from a generator? what fking generator?
Injection pump regulator? do you mean governor Duh!!!

[Jimbo1490]

Diesel engines are 'fuel throttled' rather than 'air throttled' the way spark ignited engines are. That's why most diesels do not even have a throttle butterfly valve at all, and even those few that do simply use it to generate a small constant intake manifold vacuum.

In order to 'throttle' the diesel engine down, the fuel control reduces the fuel flow, while monitoring RPM with a mechanical governor. So even at low speeds, a full air charge is entering the engine, unlike a spark ignited engine that intakes a rarefied air charge at low speeds due to the throttle plate being partly closed.

So in the diesel engine, there is plenty of available air charge to burn an additional fuel charge, if one is made available. The diesel rarely burns a 'stoichiometric' charge except a full throttle. Most of the time the diesel is running 'lean'. So there may be gains in torque to be had by introducing additional fuel. But keep in mind that additional torque means RPM will increase, too. The fuel control will then respond by reducing the flow of (diesel) fuel to keep the RPM at the designed 'set point', which just gets you back to square one, except burning a different fuel.

On the idea of burning hydrogen:

If you think propane might be dangerous, then you'll need to steer well clear of hydrogen. It is explosive at the widest variety of mixtures with air of any known substance, all the way from ~1% to ~95%. The engine, fuel lines and hydrogen storage areas will have to be ventilated at all times when the gas is present, engine running or not. From a safety perspective, it's really not a practical fuel.

Jimbo

[Jim_Hbar]

Copied from mrsharkey.com

LPG Fumigation
Page One



Lately, I've been getting quite a lot of e-mail from folks who are interested in the LPG Fumigation system that I have installed on the Pusher, so it makes some sense to have a page dedicated to that subject, with at least as much as I know about it, and some links to other resources.

What it is...and why:

Simply stated, Propane (LPG) Fumigation is the introduction of gaseous propane into the air intake of a diesel engine for the purposes of attaining more power, economy, or both. The parallel is often made between fumigation and using Nitrous Oxide on gasoline vehicles to achieve a power increase. This analogy is similar, although the properly implemented use of LPG on a diesel engine will actually result in a better-running engine without the possible damaging effects that N2O has on gas motors.

Exhaust emissions are reduced as a result, with lower quantities of unburned hydrocarbons and fewer particulates (smoke). LPG fumigation will even clean up the odor of diesel fuel in the exhaust, making the smell from the tailpipe of an engine utilizing it much less objectionable.

How it works:

Introducing LPG gas into the combustion air intake of a diesel engine acts as an accelerant, promoting the even burning of the diesel fuel, and more complete combustion, resulting in more power being produced. Many web pages and forum posts will call LPG a "catalyst" but this is not correct, as LPG creates no change in the molecular makeup of either the air or the diesel fuel.

Propane by itself resists self-ignition inside a diesel-fuel compression-ignition engine due to it's high flash point and narrow fuel-to-air ratio. During the compression stroke, the air/LPG mixture is compressed and the temperature is raised to about 400°C, not enough to ignite the LPG, which has an ignition temperature of about 500°C. In the small concentrations that LPG fumigation uses, the LPG mixture is not rich enough to be overly flammable and is more difficult to ignite. When the diesel fuel is atomized into the cylinder under high pressure, it immediately self-ignites (diesel ignites at about 385°C.), and causes the LPG to burn as well. Since the LPG is in mixture with the air, the flame front from the diesel spreads more quickly, and more completely, including igniting the air/fuel mixture which is in contact with the cylinder walls, which are cool in comparison to the super-heated air inside the combustion chamber. Much of the cleaner burning of the fuel is attributed to this ignition against the "cooler" components of the engine, and accounts for raising the percentage of combustion from a typical 75% for a well-tuned diesel engine running on pure diesel fuel alone, to 85-90% with the addition of LPG. Obviously, this more complete combustion also gives a nice boost in power, with an accompanying increase in fuel economy and reduction of pollutants.

What to Expect:

OK, here's where we have to draw a distinction between engine types. Normally-aspirated engines require different systems to introduce the gas than do turbocharged engines. The results are different as well.

Normally-aspirated (N/A) engines will realize only a modest gain in power by the use of LPG gas. Displacing 0.5% of the intake air with LPG will result in a small power increase, perhaps 5-8%. Nearly no increase in power will be noted at full throttle, assuming that your injection pump is correctly adjusted already. Attempting to provide more gas to the engine will not increase performance, and will in fact lead to a condition not unlike pre-ignition in a gasoline engine. This has been attributed to excessive peak pressure inside the combustion chamber, and may have a lot to do with the fact that most N/A engines are also IDI (Indirect Injection), which means that the diesel fuel is not injected directly into the combustion cylinder, but instead enters a "swirl chamber" where ignition takes place. The flame front then shoots out of the swirl chamber into the combustion chamber, where it combines with the air (and LPG) to force the piston down in a power stroke. Apparently, these engines have a problem in that the flame front exiting the swirl chamber ignites the LPG/air mixture, all of which burns instantly instead of in a metered, controlled manner as it would during the normal diesel injection window.

I have had satisfactory results on my VW 1.6 N/A engine when adding LPG at a rate of 8-10% of the BTU rating of the diesel the engine is using. It may be possible to turn the fuel up, but I do know for sure that too much fuel does not increase power, and causes the engine to make very unhappy noises.
It's worth noting that if you experience a big increase in power on a naturally-aspirated diesel engine after installing an LPG fumigation system, then you should go back and check to see that your injection pump was adjusted to provide a nearly stoicheometric air-to-fuel ratio at maximum throttle without the LPG turned on. It's possible that the significant power boost you are seeing is due to the engine now being adequately fueled for the first time. The additional BTU content of the LPG is simply being substituted for the diesel fuel that you haven't been injecting all along.

Turbocharged diesel engines are able to realize a significant increase in power by using LPG fumigation. While the usual suggested increase is considered to be approximately 20%, by careful management of the gas introduction, power gains of up to 40% are possible. My understanding is that it is a very fine line between lots of extra power and a dose of LPG that will render an engine scrap metal in a hurry, so consider carefully before you decide to "turn it up".

Turbo engines are by design blessed with a lean air-to-fuel ratio, and can be fed concentrations of LPG up to about 6-8% of the intake air volume. TDI (Turbo Direct Injection) engines have shown dramatic power increases when properly fumigated with LPG, combined with an "Upsolute" chip, or computer engine management upgrade. (Of course, these modifications will void any manufacturers warranties...)

continued on that site......

[CDK]

Instead of propane you could inject anything combustible, also gasoline.
The idea is that the ignition caused by compressing an air-diesel mixture will also ignite whatever else is present. It could be useful for an underpowered craft to get it over the hump and achieve planing speed. A prolonged use will probably ruin the engine.

[kistinie]

My idea behind propane was to have lower revering for the same torque as well as lower noise, cleaner burning.
Propane/butane is often already aboard for cooking.
A smaller engine can give more power when needed, or just be lighter for same torque
G/H is also lowered a little
Here is an interesting test:
http://www.exploroz.com/Forum/Topic/18664/gas_systems_for_diesel_engines.aspx

My test show very high torque improvement at iddle and low rev
The home made dymo i made couldn't stand more for the moment.

Why do you think a prolonged use would ruin the engine if cooling ok and only used to lower rev ?
Canadian tests show that temp goes down 15°C at low speeds

Butane/propane(LPG) injection seems to attract many designers:
The more radical solution was to run diesel 100% with butane/propane
http://journals.pepublishing.com/content/7l78771k12j4tg40/
http://cat.inist.fr/?aModele=afficheN&cpsidt=16076353


Now with a little deeper search, i found that ...

This idea IS already marketed !

http://www.dieselperformanceproducts.com/
http://www.wjsperformance.com/powershot/powershot.htm

I'm sure that the power and torque increase will give :idea: to a lot of diesel owners

Please also keep in mind that here in europe,
LPG is 0.6€/L
diesel is 1€/L,
unleaded 1.2€/L....

[mydauphin]

Chances are too much fuel/air of any kind and something is going to go flying.

[kistinie]

Yes, but only if you do not respect some limits, just like in life, poison is the quantity.

[Jimbo1490]

Dual fuel diesel engines make sense if you are going to lower the compression ratio down to near the optimum efficiency/power ratio, which is about 13-15:1. Normally a diesel (especially a small one) will not be able to start at this comp ratio, which is the sole reason why they have set it so high in many engines. But once running on another fuel, like propane, they can then run on diesel just fine at the lower ratio and make more power and burn less fuel because you are not needlessly over compressing the air charge.

Jimbo

[kistinie]

Very interesting Jimbo !
15:1 is what i put on a race engine with hot cam
Where did you get this ideas ?
Is there any experience, example, test telling more about it ?

[Jimbo1490]

There's a lot of text on this out there; even this diesel tech school book has a chapter on it:


Diesel: Fundamentals, Service, Repair
by William K. Toboldt


Hardcover: 352 pages
Publisher: Goodheart-Willcox Pub; 4 edition (April 1983)
Language: English
ISBN-10: 087006424X
ISBN-13: 978-0870064241


Jimbo

[kistinie]

And about commercial application ?
Do you know if any manufacturer dared doing such a "difficult to use engine" or did this dual fuel medium compression remain a principle ?

[Jimbo1490]

Many large marine engines use this strategy. Large means 1000 HP/Cylinder and larger. Fairbanks-Morse and Sulzer both had dual fuel marine engines.

Jimbo

[plebusmaximus]

Drawback

...it is a poison gas heavier than air, need to be careful
the fitting of a thermocouple on exhaust closing gas feed should be compulsory

Your system is Browns gas

You are inadvertently injecting some moisture into the cylinders.
Moisture of this type doesn't compress increasing compression.
I would be concerned for the overall lifespan of the engine.
Do you have a larger alternator for the extra required amperage needed to generate the hydrogen gas?
How does this effect fuel economy?

Why does Yanmar not implement this technology as standard, well, even as an optional extra?

[plebusmaximus]

My idea behind propane was to have lower revering for the same torque as well as lower noise, cleaner burning.
Propane/butane is often already aboard for cooking.

It depends very much on the make of the diesel engine.

Some are at more risk than others but essentially its adding a dry non-lubricating fuel to the top end of a diesel.

[pistnbroke]

Oh **** not the discredited Browns Gas again ....higher comp ratio gives more efficiency which is why Diesel is more efficient than petrol...oh god help us all .....

[plebusmaximus]

Give me Turbo Intercooled any day. :)

Oh **** not the discredited Browns Gas again ....higher comp ratio gives more efficiency which is why Diesel is more efficient than petrol...oh god help us all

Yanmar will be onto that one, but don't tell them. :rolleyes:

[FAST FRED]

higher comp ratio gives more efficiency which is why Diesel is more efficient than petrol..

AND diesel is heavier than gasoline , so there is more to burn in every gallon.

FF

[Jimbo1490]

higher comp ratio gives more efficiency which is why Diesel is more efficient than petrol..

AND diesel is heavier than gasoline , so there is more to burn in every gallon.

FF

The first statement above is just wrong; Diesels are more efficient despite their higher (too high, really) compression ratio.

The second statement is the true one as diesel fuel is the secret to diesel efficiency. But heavy fuels can only be properly ignited (in a piston engine, anyway) by compression ignition. Just how much heat, and therefore compression, you need to get the job done varies with things like ambient air temp and engine temperature. Unfortunately, the mechanical compression ratio is not variable, but rather fixed. It follows that the engineers that design these engines must allow for the worst case scenario of starting conditions, which is cold engine on a cold day. Thus they choose a compression ratio that really is too high for all other times, except for this worst case. This cuts efficiency as the engine is uselessly over compressing the air charge once it is warmed up. Oh if only someone could invent a variable compression ratio diesel engine! (http://www.greencarcongress.com/2006/10/caterpillars_va.html)

Jimbo

[apex1]

The first statement above is just wrong; Diesels are more efficient despite their higher (too high, really) compression ratio.

Jimbo

Correct Jimbo.
But the worst case scenario is the everyday scenario, so, every propulsion system has to stand that test of worst cases. Especially when there is no "garage" to warm up the metal crap and enjoy a coffe whilst that may happen. If we go to sea, the WCS is the minimum we have to be prepared for.
For that reason:
Kistinies ideas, and phantasies remain unmature if they are related with a seagoing vessel, and show very clearly he never was at sea in a serious manner, nor severe situation. (and he has proven that by one of his former statements, going from GB to the Med. Sea and crossing the bay of Biscayne in Winter time is " just a short trip in a fast multihull"
Do´nt waste your time, he will not understand your valid input.
look here for example:
http://www.boatdesign.net/forums/hybrid/diesel-hydrogen-hybrid-trawler-27028-5.html#post273595

give this a valuable input:
No ...My insurer ask me too much money for this and girl friend vote against the project. But it may change ...

Just some work in London and then in Southampton before going to "la cote d'Azur", not a long trip with a fast racing multihull.
Uncomfortable, yes, as we have nothing aboard even toilets, but efficiency is here with a 18m mast 2 tons/40 feet boat... till weather decides you stay where you are. That is sailing,
I happily accept the idea to have a master, a weather master.

And by the end, 2 or 10 litres of fuel burnt to do the trip for 3 friends

With the 5 Kw motor and 48V batteries it will be zero litre

In 15 century, Italians to say zero, used to say ZEFIRO (coming from arab word "as-sifr" meaning empty)

Isn't it fun ?

Have a Good day Richard !

Cheers

François

or enjoy:
I used to have a yanmar 1gm+sd20 inside
Don't want it any more
same for outbord

Electric choice is done.
Price is low, in my budget.
No problemo.
Do not worry, i really beleive in my study.

Now i miss the 3 kw dc electric generator, air cooled, very efficient, light ...

50kg is the max, also a question of available space, that i do not have
Cheers !

this?

Until i find a light air cooled 48V DC genny, 2/3 Kw, weighting less than 40 kg
i still have this inexpensive and very very reliable solution
Direct drive, belt reduction
i think i can direct drive the electric motor propeller shaft with a folding honda 6cv motor.
Only forward will be available on honda motor propulsion
Reverse with electricity only.
exhaust will be water injected, with full hastelloy tubing

Cannot do a simpler and safer solution ?
Yes !

This one of course, that will be aboard too
it was my first engine when a started sailing on "mousquetaire" in the 80's
quite powerful on a boat like mine and my 300 or 400 watts i guess
Human power !
http://www.boatdesign.net/forums/attachments/diy-marinizing/29903d1236579532t-making-high-efficency-3-kw-dc-generator-plan-godille-sangria_m.jpg


RAINBOWDUST................................

Regards
Richard

[FAST FRED]

"Thus they choose a compression ratio that really is too high for all other times, except for this worst case. This cuts efficiency as the engine is uselessly over compressing the air charge once it is warmed up. Oh if only someone could invent a variable compression ratio diesel engine!"

NONSENSE

The higher efficiency of ANY compression engine is why even cheap auto engines use high compression and a computer to time the spark for minimum pre ignition.The expansion of and use the burned fuel charge is what creates power, the more expansion the more Efficiency.

Variable compression ratio diesel engines have existed since at least the 1930's when diesel was used as aircraft engines to extend range and duration.

Either supercharging or turbocharging can vary the operating CR with ease.

A diesel with a very low compression ratio can be started by using an ALTERNATE fuel , to start.

This is done today with Ether injection to start large engines below -20F ,synthetic oil is required.

I met a fellow that was attempting to get diesel engines into the power range that small aircraft turbines now operate, 1 lb per hp at 300 to 500HP.

His concept was that the fuel was wasted by heating air after ignition , and his test engine has both supercharger (to be able to start easily) and turbo charger in operation.

Inlet pressure at the piston was over 1500lbs!!! And he was trying to go higher!!

Hope he finds US funding.

FF

[kistinie]

In case of these diesel with "low compression" starting with ether or another light fuel before going to heavy oil, is there a spark or is it auto-ignition with a conventional diesel cycle ?

[Jimbo1490]

Fred,
You have not presented any evidence that shows what I said to be nonsense at all. Your original assertion about the diesel engine's efficiency stemming from its high compression is not supported with any objective facts or data. Show us how and why a compression ignited engine can benefit from a compression ratio that is far and above over what is needed to induce combustion at any given moment. You can't show that, because it's not the reality of the situation. The fact that so many others have worked to overcome this very engineering puzzle is of itself evidence that the puzzle exists.

You seem to pretend that there is no engineering 'problem' at all, and that more and more compression is all good. So why not go with 25:1, or 32:1 or 40:1? Do you think there are power and efficiency gains up there, if only the engine could be made sturdy enough?

This is all known, mature science, Fred. The ideal compression ratio for power and efficiency in a diesel engine is only 13.5-15:1, no higher. But such an engine will not start cold, thus the higher compression ratios.

All the schemes of variable compression tried so far are too costly or too complex for mainstream use, or reduce reliability to an unacceptable level. But none of these secondary factors is evidence that diesels would not benefit from a variable compression ratio scheme without these shortcomings.

Jimbo

[mydauphin]

Higher Compression does produce more torque with more fuel too. The reason for lower compression on many diesels is as an aid to starting. It is not that same to start a 10,000 hp diesel or fuel oil engine at 20 to 1 compression than 10 to 1. You open valve to lower compression to get rpms up, inject ether or some other fuel then close valves switch back regular fuel. As far as higher compression most new diesel forgo higher compression by using turbos. Same effect.

[Frosty]

Diesels dont need high compression!!! funny how they love their turbos.

Ive never heard of 1500lbs intake pressures but tripe turbos can getup to 150, if the bottom end lasts.

I would have thought it a simple afair to make a cylinder with a piston arrangement in the top facing down that could be moved, like a small glo plug engine I had on a model airplane, it would screem hight RPm when the thumb screw on the top of the head was turned to increase compression ratio.

Maybe a deisel will run on low Ci once warmed up because of the energy to compress,--but the hight Ci increases efficiency and overcomes the extra load.

A turbo in the exhaust flow actually takes power from the engine inhibiting free flow of gases. But when the benefits of the compressor side of the turbo is taken into consideration it works out as a benefit as we all know.

[Jimbo1490]

Higher Compression does produce more torque with more fuel too.

Only up to a certain optimum point. Increasing the compression above this optimum point, whether you add more fuel or not, will not result in a further increase in torque at all. That point turns out to be ~13.5-15:1.



The reason for lower compression on many diesels is as an aid to starting.

Sort of, kind of true, but the complete picture is more complex. Valve overlap causes every engine (except some really big ones) to spill some of its compression at very low engine speeds, like cranking speed. This can drop the effective compression ratio to below the minimum for a cold start. So reducing the mechanical ratio can reduce the 'breakdown' torque required to get the engine spinning initially, increasing cranking speed and the heat generated by a quicker succession of compression strokes.



You open valve to lower compression to get rpms up, inject ether or some other fuel then close valves switch back regular fuel.

Dual fuel engines are one way of addressing the 'too high' compression ratio of most diesel engines. It works well but is considered too costly and complex for most smaller engines like in the automotive field.



As far as higher compression most new diesel forgo higher compression by using turbos. Same effect.

Turbochargers do nothing to help the engine start cold; all these compromises between mechanical compression ratio, camshaft profile (valve overlap) and cranking speed must sill be negotiated to retain cold starting capability.

Jimbo

[TollyWally]

Jimbo,
This is all so very interesting. The more I learn about internal combustion the more fascinating it becomes. Thank you.

[kerosene]

the fact that diesels wouldn't' like high compression ratios is news to me too. (for performance that is) - and as stated high pressure super/turbo charged engines have very high comparable cylinder pressures. And generally raising compression ratio directly helps efficiency - on gas you are limited by pre-ignition and detonation.

It really is news to me if 15:1 would be ideal from efficiency stand point.

another big reason for diesel efficiency is the fact that it can run with lean ratios - in a gasoline engine on partial throttle positions the intake air is restricted and engine is pumping against choked intake.

Gasloine starts to ping and knock on high compression and lean situations - diesel is fine for both.

edit:
This study suggest that 15 indeed is close to being the best number

http://www.arpnjournals.com/jeas/research_papers/rp_2008/jeas_0408_88.pdf


however still supercharging isn't in line with that chart - I wonder if practical dimensions have to do with that - ie. with very high compression ratio your cylinder head and combustion chamber designs are forced to be far from ideal.

[FAST FRED]

It is very possible that the shape and dimensions of an engine with variable compression ratios is quite poor.

Perhaps a side valve with poor volumetric efficiency?

The question is what relationship does the test engine have with any other current engine?

Varying the injection pressure ,a pre-combustion chamber , or an engine with more or less combustion chamber area , as well as better breathing might change all this dramatically.

After all IF any of these results are usefull to real engines,the engine test labs of EVERY engine builder worldwide are incompetant fools?

And have been blowing the bosses cash for decades?

FF

[mydauphin]

I know a little about diesels, I know Detroit Diesels fairly well so I will speak from that point of view. A non-aspirate 6-71 puts out 200 some hp, very easily and it can be boost with a turbo and aftercooler to about 430 hp. that is 1hp per Cu in. Not to bad. The bad news is the engines lifespan is cut tremendously when you double horsepower. The turbo unit has a lower compression. Going back to Non-turbo version, there is a high-compression 20:1 and low-compression 17:1. and many version in between. I don't know where 15:1 idea can from. But seems to me that is relate to using oversize turbo to putout more power, and lower emissions in idle, than an issue with diesel putting out more power at idle.

As far as propane injection, one of these days I am going to try it. Because I like longevity and fuel economy of my 200hp diesels, but on occasions I would like a short burst of power and perhaps propane is way to go for that. I know my engines can take 400hp for a little bit...

[Jimbo1490]

Remember that Detroit diesels and some others like EMD use a two-stroke cycle so the HP/Cu In numbers are a little skewed; these engines have twice the 'swept displacement' of a four stroke engine the same size.


The 15:1 number came from many years of research and published papers from the SAE and other engineering sources. Quite a few diesel tech books have referenced this number too, including the one I posted earlier.
Jimbo

[FAST FRED]

The bad news is the engines lifespan is cut tremendously when you double horsepower.


The most realistic way to contemplate engine life is not with hours, but with fuel burned.

While it is true an engine burning 3X the fuel will probably have less than 1/3 the life of a more modest power requirement

A 6-71 at 1200rpm (Prime generator) has 20x the service life in hours from the sport fish 430 hp defuller, but is far closer when the actual total gallons consumed to rebuild is counted.

FF

[mydauphin]

The bad news is the engines lifespan is cut tremendously when you double horsepower.


The most realistic way to contemplate engine life is not with hours, but with fuel burned.

While it is true an engine burning 3X the fuel will probably have less than 1/3 the life of a more modest power requirement

A 6-71 at 1200rpm (Prime generator) has 20x the service life in hours from the sport fish 430 hp defuller, but is far closer when the actual total gallons consumed to rebuild is counted.

FF

True, that is why it is better to have 200hp engine, 1000 hours a year, and a 400hp 10 hours a years. Propane might do that.

[Petros]

Also notice that you could never run a diesel on 100 percent propane, the fuel properties are too different, it only add the extra power from the propane fuel burning in the excess O2 in the mix. I think it is questionable if there would be much of a actual efficiency increase, perhaps a bit. But you have to compare your total operating cost at the same power output, not just measuring diesel fuel use.

Also both gasoline and diesel fuels have much more energy per pound than propane, so you would have to carry much more fuel to get the same amount of power output over the same time interval. Plus hazard of a carrying around a high pressure tank of a very flammable gaseous fuel on a boat.

[mydauphin]

Also notice that you could never run a diesel on 100 percent propane, the fuel properties are too different, it only add the extra power from the propane fuel burning in the excess O2 in the mix. I think it is questionable if there would be much of a actual efficiency increase, perhaps a bit. But you have to compare your total operating cost at the same power output, not just measuring diesel fuel use.

Also both gasoline and diesel fuels have much more energy per pound than propane, so you would have to carry much more fuel to get the same amount of power output over the same time interval. Plus hazard of a carrying around a high pressure tank of a very flammable gaseous fuel on a boat.

Absolutely right, I would only think of using as an emergency, like being chased by pirates or a hurricane. The propane would be stored outside for this use. I don't even use propane in kitchen on my boat. No cost efficient anyway just like nitrous on car.

[marshmat]

It would be interesting to see more on this optimum compression ratio issue. If anyone has any good papers on the subject lying around, feel free to post them.

From basic thermodynamics, the overall cycle efficiency of the air-standard Diesel cycle is easily derived. It is:
eta = 1 - 1/(r^(k-1)) * [ 1/k * (rc^k - 1) / (rc - 1) ]
= eta_Otto_cycle * [ 1/k * (rc^k - 1) / (rc - 1) ]
with
eta = efficiency (of air-standard Diesel cycle with constant-volume heat addition)
eta_Otto_cycle = efficiency (of air-standard Otto cycle with constant-pressure heat addition)
r = compression ratio
k = specific heat ratio
rc = cutoff ratio

From which we see that the theoretical Diesel cycle increases in overall efficiency (indicated, not brake, since we're talking only about the cycle) as the compression ratio increases. We also see that the Diesel cycle is inherently less efficient than an Otto cycle of the same compression ratio. (The efficiency advantage of the modern diesel engine over the modern gas engine is due to its much higher compression ratio- the composition or energy density of the fuel is not a factor in the calculation of thermal efficiency.)

Of course, the actual modern CI engine is better approximated by a dual-cycle model. But these are just models- they're a good starting point for comparison, and they give us a good idea what to expect, but they don't tell us everything that's happening.

The paper by Ratnakara et al. that 'kerosene' posted earlier found that, with their particular variable-compression test engine, fuel consumption and smoke production were minimized, and brake thermal efficiency maximized, for r=14.8. Note the reason they found for the declining performance at higher compression ratios:
The high fuel consumption at higher compression ratios can be attributed to the effect of charge dilution.
Most research I've seen that suggests problems with high-compression diesel engines explains poor behaviour at high compression in a similar way. Although the cycle is inherently more efficient at high compression ratios, other factors- such as charge dilution, charge velocity, valve timing and overlap, residual gas, etc. can cause problems at higher cylinder pressures, increasing fuel demand and compromising efficiency. Take the derivative of the equation above and it's easy to see that, as you crank up the compression ratio, you quickly run into the 'law of diminishing returns'- each successive increase in r produces ever-smaller increases in eta, increases that can easily be overwhelmed by other factors.

The optimum compression ratio will not necessarily be the same for all engine architectures or operating profiles. Open chamber designs, for instance, tend to run better at lower compression ratios than pre-chamber designs. There will of course be lower peak pressures in a lower-compression engine, thus reducing stress on the parts as well as reducing the tendency to sound like there's a leprechaun with a hammer in each cylinder.



Those nitrous oxide systems for street-race cars have been effectively banned around here. (You can transport them, but the system and bottles must be disconnected.) It seems the fire departments were getting tired of having the things explode (and when they go, they pack one hell of a whallop) in collisions or as the firefighters were trying to extract the drivers from crashed street-race cars.

[mydauphin]

Marsh,
I think the big problem with diesels is that the engine companies, because of the bureaucrats, have been focusing on emissions and not efficiency. The interesting thing is that a ultra-efficient diesel will burn less fuel than a gas engine or even a low-emission diesel, but all the development goes into low-emission. A case in point is two-stroke diesels, they were starting to computerize and really make these puppies sing. Then the whole thing was canned because of emissions.

As a young hot rodder, I learned quickly how to get a motor to put out more power, but at the cost of emissions. I had 200hp four cylinder pontiac firebird that flew, and got really good gas mileage. Now we are asking engines to produce power, be fuel mizers, and have low emissions.

More power can mean less fuel if you run motor slower.

On nitrous, I saw a intake manifold on a v8 break off an engine, go through a hood, and twenty feet away. Now a days with correct setup that wont happen, but care is necessary, especially when you start engine. Nitrous would freeze valves and then leak slow into engine when off, then when you turn on engine... Well Boom...

[marshmat]

Ontario loses about 6000 to 9000 people a year to smog and air pollution. 2100 of those deaths are in Toronto alone, most of the rest in the surrounding cities. We have about 16,000 to 20,000 patients a year treated in hospital for smog-related illnesses. So when our bureaucrats clamp down on engine manufacturers, factories, cement plants, and everything else, saying "you must cut your emissions by xxx"..... that's why. There are just too many engines, too many factories, too many power plants in too small a space. (And we don't really set our own emissions regulations- we just copy California's from a few years earlier.)

Back to the topic....
It's interesting to look at long-term trends in engine design. The Ford Model T had a whopping 20.2 hp and consumed 11 to 19 L/100km (13 to 21 mpg). My ten-year-old Hyundai Elantra has about 130 hp and uses 7 to 9 L/100km. 6.5 times the power with half the fuel. Yet, fleet-wide, we're not using any less fuel per car than we were back then. Most of the engine performance and efficiency gains we've made in the last century have been used for increased power (>200 hp in a compact sedan? WTF?) and to make cars bigger, faster and heavier for the same amount of usable space (Lexus RX, I'm talking about you). Serious work on emission control is a relatively new phenomenon- EGR and PCV systems date back a few decades, but most of the emission controls we take for granted today have only been around for 10 to 25 years. Had we devoted the same effort to efficiency and emissions over the last 70 years as we have devoted to cramming more power into a given size of engine bay, who knows where we could be.

But I'm getting away from the real topic, which, IIRC, was about spraying combustible liquids into the intake of a diesel....

[mydauphin]

Had we devoted the same effort to efficiency and emissions over the last 70 years as we have devoted to cramming more power into a given size of engine bay, who knows where we could be.

But I'm getting away from the real topic, which, IIRC, was about spraying combustible liquids into the intake of a diesel....

My point exactly, so if you build your diesel like a hot rod. More flow, compression, more air, ported heads, more fuel, less restrictive exhaust, blueprint it. Make it faster, more rpms, then you have what BMW and MB have done. More HP per CC, more reliability and greater performance and fuel economy.

Anyway, Propane is to diesel like Nitrous is to Gas engines. It can enhance the power, but the better built the engine the better it will make it.
Oh one thing about Nitrous, we also had to inject raw gasoline(fuel) into intake to compensated for extra oxidizer.
Interesting will be to inject Nitrous(oxidizer) and Propane (fuel) into diesel.
Otherwise injecting propane only will be limited by amount of oxygen already in engine in air.

[M-Sasha]

[QUOTE] Serious work on emission control is a relatively new phenomenon- EGR and PCV systems date back a few decades, but most of the emission controls we take for granted today have only been around for 10 to 25 years.


Only for you, only for you in the US!
The Germans have been "Green" 40 years ago! But nobody would hear them praying. Fuel was so cheap in the US (and still is far too cheap).

But back to topic:

Propane injection (like any and every other faster combusting stuff than (med destillate at 50 ct.) kills your engine sooner or later! period

If you need a proven way to gain more HP, chip the iron! And again, it kills.

There is a relation between max power and durability which has to be accepted > even by complete ****** like Kistinie <.
Like it or invent a new wheel! One that is proven to run round, I mean!!!!

These idiotic claims and "proofs" above are worth nothing.
Did not mean Matt and Myd.

Sasha

[mydauphin]

[QUOTE=marshmat;274913]


If you need a proven way to gain more HP, chip the iron! And again, it kills.



These idiotic claims and "proofs" above are worth nothing.
Did not mean Matt and Myd.

Sasha

Thanks Matt, help us send the snakeoil salespersons away...
What do you mean by chip the iron, I don't no that phrase.

[apex1]

Think he (Sasha) meant modern "chip controlled" Diesels (Iron).

He was able to get a completely unwilling "Skoda" engine of about ?70? ltr. displ. 1550 hp, back into service, using soap, wire, and a hammer! USSR!

Regards
Richard

[marshmat]

Chip the iron -> sounds to me like bore and/or stroke it for more displacement.... with the obvious loss of durability that may come from the resulting thinner, more highly stressed block.
Computer controls ought not to diminish the life of the block... if anything, they ought to improve it (less carbon deposits, better temperature control, etc.).... but the computer itself, and the 100-odd sensors and actuators it's connected to, well, we all know what happens to the VISA card when they go bad.

[apex1]

Computer controls ought not to diminish the life of the block...

They do, be shure.
I cannot recall the figures of a very impressive study i´ve seen in the 80 ies, showing that the lifespan of a (hughe) ships diesel is narrow connected to the mass involved! As I remember B&W MAN had the longest lifespan followed by "Wärtsiläa", "Sulzer" and all the conglomerates, simply due to the fact: they had more "combustion related" mass (not housing and basement) than for example "Pielsticks" and "Mitsubishi".

Just a thought.
But one of the commercial side (I guess)

Regards
Richard

[Jimbo1490]

The optimum compression ratio will not necessarily be the same for all engine architectures or operating profiles. Open chamber designs, for instance, tend to run better at lower compression ratios than pre-chamber designs. There will of course be lower peak pressures in a lower-compression engine, thus reducing stress on the parts as well as reducing the tendency to sound like there's a leprechaun with a hammer in each cylinder.



You've said a mouthful here, given that the architectural details turn out to be much more important than the simple mechanical compression ratio, or even the effective ratio.

There are a plethora of pre-chamber designs, many that use lower compression ratios. And the presence or absence of diesel knock is difficult to even relate in a casual way with such broad design families as 'pre-chamber' and 'open chamber'. After all, knock is simply the result of the delay of the onset of combustion, such that all or nearly all of the fuel charge has entered the chamber before the combustion event begins. A low compression engine may knock terribly at low speeds and light loads, if the onset of combustion is delayed.

Among the characteristics of any pre-chamber design is the conservation of combustion heat in a specific area within the cylinder (the pre-combustion chamber) in order (among other things) to ensure that there is no delay in the onset of combustion, the major cause of diesel knock.

Many use a 'glow bar', which retains a low 'red hot' state during operation. Such designs often depend on glow plugs to start since the glow bar won't be hot when the engine starts cold.

These measures are designed to get the charge burning with a lower effective compression ratio by causing super-atomization and turbulence. The goal is to mitigate the differences in combustion onset that normally occur under differing conditions of load and engine temperature.

Have a look at the Maybach 'M' pre-chamber desgn. Also look at the Lanova energy cell.


Jimbo