What is a Diesel Engine ?

[GreenTwin]

My dad restored a John Deere model H tractor, with manual start via spinning the flywheel.

This was back in about 1976.

This tractor had two fuel tanks.
A small one of about 1 gallon, and a much larger one under the cowling, perhaps 20 gallons.

I asked my dad about the two tanks, and he said the small one was for gasoline, and the larger one was for kerosene.

I said "But this is a gasoline engine", and he said "yes, but kerosene was much cheaper than gasoline in the day" (not true today in these parts), and "this tractor will run on kerosene".

I did not believe him, and so I had to try it.
I filled the small tank on diesel, and started the engine on gasoline.
I got the engine hot, and then switched over to diesel, and sure enough with the throttle wide open it would run perfectly on diesel.

It would not idle on diesel.

I have heard all sorts of terms, such as "hot bulb diesel", and "semi-diesel", etc.

It would seem that any gasoline engine could run on diesel, or perhaps kerosene.
Kerosene is a bit lighter and combusts more easily than diesel, as I have learned from my foundry burner days.

It begs the question "Why use a diesel engine at all, if you could use a gasoline engine?".

I think much of that answer is due to the large amount of low-rpm torque that a diesel engine will produce, which is very useful for heavy equipment, tractors, etc.

The diesel seems to be able to withstand constant heavy loads better than a gasoline engine too, which I suppose is due to the larger bearings, and stronger components such as crankshaft, connecting rod, piston, crankcase, etc.

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[GreenTwin]

So what about building a "diesel" model engine that has a carburetor, and running it on kerosene?

It would look like a diesel engine, like the one below.

The benefits would be to build a lighter and simpler engine that did not need an injector and pump, but would still look and run like a diesel.

Just throwing out ideas, and not sure if they are practical ideas or not.

 

[GreenTwin]

And this is a cool video, I guess most of these are semi-diesel hot bulb engines?

 

[GreenTwin]

If for no other reason, it would be well worth building a model that looked exactly like the Ellwe, hiding the carburetor and spark plug, adding a fake injector and pump, and running it on kerosene at a show, and watch folks scratch their head.

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[Roger B]

It's been done

 

[GreenTwin]

Dang, I forgot about Muller Nick, and I did not realize he had built an Ellwe either, although I knew it was some sort of marine engine.

Nick was doing some impressive casting work there for a while, and then I think he had a bike accident and broke one or both wrists.

Apparently Nick is still working, but I have not seen any more casting work.
He is an extremely talented individual.

Here are some of Nicks casting videos:

 

[minh-thanh]

If for no other reason, it would be well worth building a model that looked exactly like the Ellwe, hiding the carburetor and spark plug, adding a fake injector and pump, and running it on kerosene at a show, and watch folks scratch their head.

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Personal opinion, I based on the engine that I like and designed it according to the engine with ignition, gasoline, design and make it beautiful and special, why not: " The engine is designed and built by ...." .
I'm proud to tell everyone that's the engine I designed and built,
I can cheat,.. when machining an engine part, but I hate making "people scratch their heads".
Personal opinion !

 

[GreenTwin]

There was a two cylinder inverted gas engine at an engine show up north, and it would start and stop itself at random times.

There was no starter on the engine, and it was as if someone were pushing an ignition button remotely.

My friend and I watched the engine for about 30 minutes, and the only person anywhere near the engine was a little boy, about 5 years old, about 20 feet away, playing with a toy truck.

We watched the little boy for for a while, and finally noticed a button hidden in his toy truck, and discovered a wire that had been hidden below ground, going over to the engine.

It was a great ruse, and we did not tell anyone what we discovered, but instead watched others scratching their head, while the little boy snickered.

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[danallen]

My step dad had a John Deere just as described in the first post. It had a conventional spark ignition engine that was started on gasoline by hand turning the flywheel. Once the engine was hot a selector valve switched the fuel to kerosene. In the winter it was hard to keep it hot enough to switch over.

 

[GreenTwin]

I am guessing that a semi-diesel uses an injector, but does not have sufficient compression to auto-ignite the fuel?, and thus the hot bulb to start.

And a John Deere running in kerosene would still use the spark plugs for ignition, since that compression would also be too low for auto-ignition.

I guess many different fuels could be used to run an internal combustion engine, as long as the fuel produced sufficient power, was relatively inexpensive, readily available, and as long as the fuel burned cleanly and did not soot up the cylinder.

Seems like I read about some eary IC engines that burned coal dust?

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[minh-thanh]

There was a two cylinder inverted gas engine at an engine show up north, and it would start and stop itself at random times.

There was no starter on the engine, and it was as if someone were pushing an ignition button remotely.

My friend and I watched the engine for about 30 minutes, and the only person anywhere near the engine was a little boy, about 5 years old, about 20 feet away, playing with a toy truck.

We watched the little boy for for a while, and finally noticed a button hidden in his toy truck, and discovered a wire that had been hidden below ground, going over to the engine.

It was a great ruse, and we did not tell anyone what we discovered, but instead watched others scratching their head, while the little boy snickered.

.

Yes, it's ok for you and some others but not for me.
I would say the plunger stroke in my diesel engine is 0.01 mm, I can also say the tolerance between the plunger and the pump cylinder is 0.001 mm, and that would leave people scratching their heads and arguing. ....
Can I fake a 4 stroke engine, stirling , flame eater, diesel...and use electricity to run it? Yes I can and it's easy for me to do, but sorry that's not my way at least in my hobby.
Of course, that's my personal opinion
You do it the way you want .

 

[Jeffro]

A petrol (gasolene) engine usually atomises the fuel in the intake air (fuel air fine mist) via the carburetor and the spark plug ignites this to run.

Kerosene needs to be vaporized for the spark to achieve similar fuel burn in the engine. Carburetor still supplies the fuel air mix and the inlet manifold has to have an intake air heat exchanger (commonly an exhaust hot box around the intake manifold to achieve this vaporisation).

With a cold engine you need to drain the carby of kerosene ( a float bowl wingnut drain valve is part of the carby ) change to petrol to fill the carby bowl. Start the engine and run it on petrol until normal operating temperature then close off petrol and open kerosene tank.
If you stop the engine it will only restart on kerosene while still hot if you quick enough.

In Australia "Power Kerosene" was used, not common lighting kerosene.

For many years now I have only bothered to run ( 3 International tractors ) on petrol. The hot boxes adjusted to reduce heating of the intake manifold for better efficiency.

Most hot box internals have corroded now to a stage of unable to heat sufficiently anyway.

Cheers
Peter

 

[GreenTwin]

Yes, it's ok for you and some others but not for me.
I would say the plunger stroke in my diesel engine is 0.01 mm, I can also say the tolerance between the plunger and the pump cylinder is 0.001 mm, and that would leave people scratching their heads and arguing. ....
Can I fake a 4 stroke engine, stirling , flame eater, diesel...and use electricity to run it? Yes I can and it's easy for me to do, but sorry that's not my way at least in my hobby.
Of course, that's my personal opinion
You do it the way you want .

I prefer to keep my scaled model designs as close to the original as possible/feasible, but to be honest, if someone like Muller Nick casts an engine as beautiful as his Ellwe naval engine, I don't really care how he does it, that is a magnificent engine and a very difficult set of home castings that he made.

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[rutzen]

Petrol/paraffin tractors were very common in the UK. Paraffin is heating oil or kerosene so does not attract the same tax as petrol or gasoline. It is still a lot cheaper here. Diesel is something quite different and you couldn't start a petrol/paraffin tractor on diesel, it ignites by compression and needs a compression ratio of about 16;1 which is why model diesels are so difficult to make. Diesel engined cars are common in the UK, again it is mainly because of cost of fuel, the diesel costs pretty much the same as petrol and they do a lot more mpg. Also the engines are heavily built to withstand the high compression ratio and so will go for a lot more miles, 250,000 is not uncommon whereas a petrol car is pretty much clapped out at 100,000 miles. Back in the sixties you did well if they lasted half that. Diesel engines have not been much used in aircraft which is a pity because the fuel is so much cheaper than AVGAS and does a lot more mpg. Although I do know someone who has a light aircraft with a car diesel engine in it. They were used in Zeppelins because there was no spark which could ignite the hydrogen. I guess this was why the Germans were so much ahead with diesel engine development. Petrol has always been silly cheap in the US which accounts for the gas guzzlers they have while fuel being extremely expensive in the UK has taken car development down a different route.

 

[GreenTwin]

I have the Diesel book, but have not had time to read it.

As I understand it, Diesel went through a lot of trial and error developing his engine, and it took many years to get it working correctly.

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[josodl1953]

Nowadays diesel engines for light aircraft are becoming more common with the declining availability of AVGAS in the Netherlands.
Since diesel engines run well on Jet A1 fuel this is a solution , apart from the better fuel economy, where re-fueling of petrol- driven aircraft is a problem. One of the companies manufacturing these engines is formerly known as TAE ( Thielert Aero Engines)

Jos

 

[GreenTwin]

Some diesel engines do not run well at all on Jet-A.

I was working for a company who had a large client that shall remain un-named.

The client got the bright idea that they could run their 22.5 MW of diesel generators on Jet-A, and then burned up 18 units at 1,250 KW each.

It was an extremely costly rebuild.

Jet-A does not lubricate like diesel.
Jet-A is considered a "very dry" fuel, as far as lubrication qualities.

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[Chris Rayner]

Petrol/paraffin tractors were very common in the UK. Paraffin is heating oil or kerosene so does not attract the same tax as petrol or gasoline. It is still a lot cheaper here. Diesel is something quite different and you couldn't start a petrol/paraffin tractor on diesel, it ignites by compression and needs a compression ratio of about 16;1 which is why model diesels are so difficult to make. Diesel engined cars are common in the UK, again it is mainly because of cost of fuel, the diesel costs pretty much the same as petrol and they do a lot more mpg. Also the engines are heavily built to withstand the high compression ratio and so will go for a lot more miles, 250,000 is not uncommon whereas a petrol car is pretty much clapped out at 100,000 miles. Back in the sixties you did well if they lasted half that. Diesel engines have not been much used in aircraft which is a pity because the fuel is so much cheaper than AVGAS and does a lot more mpg. Although I do know someone who has a light aircraft with a car diesel engine in it. They were used in Zeppelins because there was no spark which could ignite the hydrogen. I guess this was why the Germans were so much ahead with diesel engine development. Petrol has always been silly cheap in the US which accounts for the gas guzzlers they have while fuel being extremely expensive in the UK has taken car development down a different route.

This was a common means to fuel tractors in the fifties. The fuel was classified as Tractor Vapourising Oil, or TVO. It was similar to diesel fuel, but of course the tractors continued to use the same compression ratio and spark to burn the fuel. The only engine which can properly be called a Diesel is one where the fuel is injected into the engine close to the end of the compression stroke when the compressed air in the cylinder is hot enough to ignite the fuel. There are many small model engines which are called diesels, but in truth they are compression ignition engines, the fuel and air being mixed in a carburettor of some kind prior to induction.

 

[GreenTwin]

Great information.

So what is a semi-diesel?

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[ajoeiam]

snip

It begs the question "Why use a diesel engine at all, if you could use a gasoline engine?".

I think much of that answer is due to the large amount of low-rpm torque that a diesel engine will produce, which is very useful for heavy equipment, tractors, etc.

The diesel seems to be able to withstand constant heavy loads better than a gasoline engine too, which I suppose is due to the larger bearings, and stronger components such as crankshaft, connecting rod, piston, crankcase, etc.

.

There are some points that you haven't touched on as to why a diesel engine 'makes more sense'.

You started in your last sentence - - - but - - - - gasoline engines became to be designed for short term high power - - - - not for constant power.
You can get constant power gasoline engines - - - - think Waukesha (just checked and I think its now part of Jenbacher - - - not sure though!).
White and Superior also had such - - - but these were all beasts - - - - think not only straight 6s but straight 8s with a bore in the 8 to 10" range and stroke - - - - dunno (only saw the liners so dunno actual engine internal specs). We are highly impressed with the power in a drag car but that engine is run for what - - - maybe seconds - - - most definitely NOT for years at a time at those load levels.

Then there is another aspect - - - - in the refining - - - - well its much easier making diesel from crude oil than gasoline.
Even with the catalytic cracking (as I believe its called) its still easier to make diesel - - - - they are longer chain molecules.

I wonder why in the heck we have gasoline engines?