What is a Diesel Engine ?

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Alyn Foundry said:
I personally think that both evolutionary processes are on a par with each other.
You might like to consider reading up on George B Brayton? He’s been an almost forgotten pioneer in the area of internal combustion. Accredited with the invention of the liquid fuel injector and his Cycle is now in extensive use around the world.
I have been very slowly building a replica of one of his engInes for over 20 years now. Hopefully I will get to finish it in the next couple of years.
Cheers Graham.View attachment 146995View attachment 146996
Click to expand...
George Brayton is hardly forgotten. His cycle lives in every gas turbine, either flying in every commercial passenger plane not having a propeller turned by a babbitt beater or in various stationary services. I believe George's largest engine currently produces over 500,000 horsepower. There's one operating 24/7 in an electric power station about ten miles from here.

I have a small Brayton Cycle reciprocating, vertical, single-cylinder engine which I believe was made by the same mechanic who made the three-cylinder Brayton engine in George Seldon's infamous automobile. It appears to be designed to burn either a gaseous fuel or benzine (gasoline). The gaseous fuel enters through a rubber hose directly into the compressor inlet. The liquid fuel is injected into a burner atomizer by a tiny "D valve" displacement pump. The engine is somewhat sooted up internally and slightly worn, so I believe it ran at one time. It has about a 2-1/2" bore and stroke and a cast-iron lyre-shaped hollow frame which doubles as the compressed air receiver. The tiny overhead camshaft, driven from the crankshaft by a vertical tower shaft, also drives a tiny vane-compressor, the purpose of which is not obvious. I believe the vane compressor is part of a "keep alive" system to sustain the combustor pilot flame during the exhaust stroke.
 
Last edited:
From my engineering perspective engine running on Otto cycle or similar ( combustion at constant volume) are petrol or gasoline engines while engine running on Diesel cycle (combustion at constant pressure) are Diesel engine. Modern slow speed marine diesel engine use dual cycle.

download.png

Otto cycle

download (1).png


Diesel cycle
download (2).png


Dual cycle

Regards
Nikhil
 
Nikhil Bhale said:
From my engineering perspective engine running on Otto cycle or similar ( combustion at constant volume) are petrol or gasoline engines while engine running on Diesel cycle (combustion at constant pressure) are Diesel engine. Modern slow speed marine diesel engine use dual cycle.

View attachment 147974
Otto cycle

View attachment 147975

Diesel cycle
View attachment 147976

Dual cycle

Regards
Nikhil
Click to expand...

Sorry - - - - I find these diagrams quite hard to read - - - is there any way that larger versions could be made available - - - even as a link - - - please?

TIA
 
in modern times Diesel means fuel directly injected near top-dead-center so that it ignites based on the heat of the compressed air, the actual fuel can be almost anything, the reason for "diesel fuel" is it is less costly to refine from crude than gasoline, but pumps and injectors won't last unless the fuel has lubricating properties

glow plugs, hot tubes, and air blast, are "semi-diesel", mostly just antiquated experiments along the way of perfecting the modern diesel, and are not really used any more (except as you know in some model airplane engines, which are really hybrid engines as they do have carburetors)

this is in contrast to an engine with a carburetor where air and fuel are mixed before being admitted into the cylinder, or with fuel injection where air and fuel are mixed along the way into the cylinder, and then compressed, and then ignited by spark. Again the type of fuel isn't the distinguishing factor, just about anything will work, but gasoline has high volatility and low viscosity which help with atomization and vaporization.

the difference between the Otto cycle and the Diesel cycle in Carnot analysis is largely theoretical, the notion that the pressure stays constant during combustion in the Diesel as the fuel is slowly injected is maybe applicable to super huge container cargo ship engines turning over at super slow propeller speeds, but auto and truck diesel engines are spinning too fast for combustion to be slow enough for it to take place at constant pressure.

HTH, IMHO, YMMV, yada, yada, yada...
 
rutzen said:
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.
Click to expand...
Diesel (sorta) has been used lots in aircraft, just not the excessively heavy diesel engines. The torque curve of a diesel is also not as favorable to a prop driven craft as a 4 stroke gas engine.

JET 1 is basically diesel. It's closer to kerosene but kerosene is basically diesel minus the good stuff.

So you could say they just found a better way to burn diesel (turbines)


My old flat head lawn mower loved kerosene. Once it was good and hot I would switch to a 75% kerosene blend. Ran the same except nothing could bog it down.


Fun fact, there have apparently been more successful steam powered planes then piston diesel engines. (Citation missing)
 
The Ignoble Troll said:
Diesel (sorta) has been used lots in aircraft, just not the excessively heavy diesel engines. The torque curve of a diesel is also not as favorable to a prop driven craft as a 4 stroke gas engine.

JET 1 is basically diesel. It's closer to kerosene but kerosene is basically diesel minus the good stuff.

So you could say they just found a better way to burn diesel (turbines)


My old flat head lawn mower loved kerosene. Once it was good and hot I would switch to a 75% kerosene blend. Ran the same except nothing could bog it down.


Fun fact, there have apparently been more successful steam powered planes then piston diesel engines. (Citation missing)
Click to expand...

I had the Aspera engine for lawn mover, the engine ran on pure kerosene without problem after the engine ran first on gasoline. 😊
 
GreenTwin said:
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.

.
Click to expand...
Diesel fuel and Kerosene are very different fuels. That engine will not idle on diesel because you are using the wrong fuel.
A Gasoline Engine and a Kerosene engine both require some type of ignition, most common is a spark plug.
Back in the day Kerosene was much less expensive so it's advantage was cost, as it has less power than does Gasoline. Kerosene also requires less compression.
Briggs&Stratton used to recommend adding a second head gasket to lower the compression on the old cast iron flat head engines running on kerosene.
A true diesel uses diesel fuel, and today, the US military uses jet fuel, and is a compression ignition engine. Diesels run with a compression ration of as low as 12:1 and 20:1 at the higher end.
There are model airplane engines, popular in England, that are called diesel, as they are true compression engines but they run on a mixture of kerosene, ether and castor oil. The ether lowers the ignition point to provide ignition under compression.
For a light use application a gasoline engine is great, low maintenance and light weight. For harder working applications where more torque is needed a diesel has the advantage. A diesel engine has to be built heavier to handle the higher compression and higher forces from ignition and is more complex because of the high pressure injection system into the cylinders at the peak of compression. A diesel can be finicky at lower temperatures because the cold engine takes away some of the heat of compression. A small amount of gasoline can be added to the diesel fuel and glow plugs can be used to add some heat to the engine to get it started.
 
kf2qd said:
Diesel fuel and Kerosene are very different fuels. That engine will not idle on diesel because you are using the wrong fuel.
A Gasoline Engine and a Kerosene engine both require some type of ignition, most common is a spark plug.
Back in the day Kerosene was much less expensive so it's advantage was cost, as it has less power than does Gasoline. Kerosene also requires less compression.
Briggs&Stratton used to recommend adding a second head gasket to lower the compression on the old cast iron flat head engines running on kerosene.
A true diesel uses diesel fuel, and today, the US military uses jet fuel, and is a compression ignition engine. Diesels run with a compression ration of as low as 12:1 and 20:1 at the higher end.
There are model airplane engines, popular in England, that are called diesel, as they are true compression engines but they run on a mixture of kerosene, ether and castor oil. The ether lowers the ignition point to provide ignition under compression.
For a light use application a gasoline engine is great, low maintenance and light weight. For harder working applications where more torque is needed a diesel has the advantage. A diesel engine has to be built heavier to handle the higher compression and higher forces from ignition and is more complex because of the high pressure injection system into the cylinders at the peak of compression. A diesel can be finicky at lower temperatures because the cold engine takes away some of the heat of compression. A small amount of gasoline can be added to the diesel fuel and glow plugs can be used to add some heat to the engine to get it started.
Click to expand...

"Kerosene" is also not a definitive substance. It's like saying "kleenex".


"Kerosene" is a brand name for a coal distillate that was used for lamps. Actual "Kerosene" is not the same everywhere. For example, many things refer to rocket engines running on Kerosene but it's actually RP1 a highly refined version of JP1 which is also referred to as "Kerosene" in some circles as well as heating oil which is also referred to as grade 2/3/4 heating oil but is basically just dirty (chemically and literally) dirty diesel which is why it is dyed, so in theory vehicle enforcement can check fuel tanks.

In theory kerosene comes across from sweeter crude first then "Diesel" which gives it a lower boiling point, but heavier kerosene is also used in things like smokeless lamp oil where it contains more paraffin... then you have drug store "mineral oil" which gets called "highly refined kerosene" or liquid paraffin... which is also used to refer to diesel, lamp oil and kerosene 🫠


In short... when someone refers to using kerosene for anything other then cleaning parts... you don't necessarily know just what the heck is going on or what they bought as "Kerosene" which makes it harder to generalize on the fuels behavior in an ICE.


As a former fire performer, different brands of kerosene tasted notably different. Different mouth feel too.
 
snip ........................
kf2qd said:
............................ A small amount of gasoline can be added to the diesel fuel and glow plugs can be used to add some heat to the engine to get it started.
Click to expand...

Many years ago when I was a kid on a construction site, I was told by the diesel mechanic trying to get a motor grader running, to pour some gas on a rag and hold it over the diesel air intake. I thought he was just looking for a good laugh at the "kid's" expense, BOOM, ha ha. But son of a gun if the engine didn't start right up. Afterwards he told me to never pour gas into the intake, just hold the wet rag over the intake. I learned a lot by being his gopher and just paying attention.
 
Lloyd-ss said:
Many years ago when I was a kid on a construction site, I was told by the diesel mechanic trying to get a motor grader running, to pour some gas on a rag and hold it over the diesel air intake.
Click to expand...
Best way to get one's hand taken off real quick....stupid advice.
 
bluejets said:
Best way to get one's hand taken off real quick....stupid advice.
Click to expand...
With the rag on the outside of the air intake cleaner? I have never witnessed a problem when this is done, although I guess something wrong could happen. Using gasoline and solvents always requires caution, and if you aren't sure, please don't do it.
 
peterl95124 said:
in modern times Diesel means fuel directly injected near top-dead-center so that it ignites based on the heat of the compressed air, the actual fuel can be almost anything, the reason for "diesel fuel" is it is less costly to refine from crude than gasoline, but pumps and injectors won't last unless the fuel has lubricating properties

glow plugs, hot tubes, and air blast, are "semi-diesel", mostly just antiquated experiments along the way of perfecting the modern diesel, and are not really used any more (except as you know in some model airplane engines, which are really hybrid engines as they do have carburetors)

this is in contrast to an engine with a carburetor where air and fuel are mixed before being admitted into the cylinder, or with fuel injection where air and fuel are mixed along the way into the cylinder, and then compressed, and then ignited by spark. Again the type of fuel isn't the distinguishing factor, just about anything will work, but gasoline has high volatility and low viscosity which help with atomization and vaporization.

the difference between the Otto cycle and the Diesel cycle in Carnot analysis is largely theoretical, the notion that the pressure stays constant during combustion in the Diesel as the fuel is slowly injected is maybe applicable to super huge container cargo ship engines turning over at super slow propeller speeds, but auto and truck diesel engines are spinning too fast for combustion to be slow enough for it to take place at constant pressure.

HTH, IMHO, YMMV, yada, yada, yada...
Click to expand...
There are a couple of other points to consider with modern electronic fuel injection systems.

Spark ignition engines often use various stratified charge systems to allow leaner mixtures and higher compression without pre ignition/knocking. Spark ignition engine fuels are still designed to have poor self-ignition qualities = high Octane rating.

High speed turbocharged automotive diesels now split the injection into several stages to limit the maximum cylinder pressure, moving closer to Diesel’s original concept. This allows for an initial pilot injection which reduces the need for good self-ignition properties = high Cetane number.

Things become even more interesting when you look at the Mahle Turbulent Jet Ignition (TJI) used in F1 cars:

https://www.motorsportmagazine.com/articles/single-seaters/f1/ferraris-formula-1-jet-ignition/

Or the Homogenous Charge Compression Ignition (HCCI) Engines which are neither spark ignition nor Diesel:

https://www.intechopen.com/chapters/43660
 
colby15642 said:
George Brayton is hardly forgotten. His cycle lives in every gas turbine, either flying in every commercial passenger plane not having a propeller turned by a babbitt beater or in various stationary services. I believe George's largest engine currently produces over 500,000 horsepower. There's one operating 24/7 in an electric power station about ten miles from here.

I have a small Brayton Cycle reciprocating, vertical, single-cylinder engine which I believe was made by the same mechanic who made the three-cylinder Brayton engine in George Seldon's infamous automobile. It appears to be designed to burn either a gaseous fuel or benzine (gasoline). The gaseous fuel enters through a rubber hose directly into the compressor inlet. The liquid fuel is injected into a burner atomizer by a tiny "D valve" displacement pump. The engine is somewhat sooted up internally and slightly worn, so I believe it ran at one time. It has about a 2-1/2" bore and stroke and a cast-iron lyre-shaped hollow frame which doubles as the compressed air receiver. The tiny overhead camshaft, driven from the crankshaft by a vertical tower shaft, also drives a tiny vane-compressor, the purpose of which is not obvious. I believe the vane compressor is part of a "keep alive" system to sustain the combustor pilot flame during the exhaust stroke.
Click to expand...
Would you mind making a thread on this engine? I'm very curious to see it's set up and I can't find any Google images of the set up you describe.
 
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