What is a Diesel Engine ?

[Chris Rayner]

Great information.

So what is a semi-diesel?

.

Search me, it’s not a term I’d use. You need to ask those who do.

 

[Chiptosser]

Check out the German made Lohmann Diesel bike engine.
It has variable compression.

 

[GreenTwin]

How about hot bulb diesel?

.

 

[GreenTwin]

I wonder why in the heck we have gasoline engines?

I started tinkering with lawnmower engines at an early age, and took enough of them apart to become familiar with the various parts.

After that, I could pretty much get any gasoline engine to run, just by verifying fuel flow and spark.

Even with low compression, leaking valves, etc. I could get gasoline engines to generally run, perhaps not running perfectly, but running.

My limited experience with diesels has not been the same.
There seems to be a lot more variation with how diesel injection systems are made, and you have to be familiar with the particular one you want to work on.

If the compression is a bit low, you can forget about getting a diesel started, except perhaps with a bit of starting fluid.

The pump and/or injectors on a diesel don't seem to be nearly as simple or forgiving as a gasoline engine carburetor.

If you let a diesel run out of fuel, you generally will have to purge all the fuel lines.

Diesels don't seem to be very tolerant with poor quality fuel, or water in the fuel.
Gasoline engines are not very picky about fuel, although they don't work well with water in the fuel either.

Compared to a diesel engine, gasoline engines are light, simple and relatively inexpensive.

If you need a diesel, such as for a high torque load, or very rugged service, then they will be the most cost effective solution.

My dad was using a 4-cylinder Continental on a transfer car, and they had a lot of problems with the engines wearing out, and not having sufficient torque.
He replaced that engine with a 2-cylinder air-cooled Lister, and he had plenty of torque, and never had to replace the engine.

Automobiles tend to be somewhat lightweight, and a lightweight gasoline engine suits an automobile well, since you generally don't need a lot of torque in a car.

For folks who pull heavy trailers, they generally use a pickup truck with a Cummins diesel in it, since that engine will pull a very heavy load up a mountain without much trouble.

So gasoline engines are relatively simple and lightweight, and many folks know how to repair and maintain them.
Gasoline engines also work well on motorcycles, especially when you want to keep weight to a minimum, such as a motocross bike.

There are good applications for gasoline engines, and good applications for diesel engines, but sometimes I see diesel engines used in an application where a gasoline engine would be more cost effective.

I generally don't see heavy gasoline engines, other than perhaps in ocean tankers and such, but no doubt they exist.
Generally for heavy applications, they just use a diesel, since I think the diesel is more efficient than a gasoline engine.

.

 

[Chris Rayner]

Check out the German made Lohmann Diesel bike engine.
It has variable compression.

Compression ignition, two stroke, not a Diesel. They called it a Diesel, but it isn’t/wasn’t.

 

[Chris Rayner]

How about hot bulb diesel?

.

That again is a compression ignition engine, with a hotspot to initiate combustion, bit like A glow plug engine. Not a Diesel.

See here: Hot-bulb engine - Wikipedia

 

[GreenTwin]

It would seem that the Lohmann diesel would suffer from early ignition.

.

 

[GreenTwin]

That again is a compression ignition engine, with a hotspot to initiate combustion, bit like A glow plug engine. Not a Diesel.

See here: Hot-bulb engine - Wikipedia

That is a good article, and explains a lot of differences between the hot bulb diesel and the high compression injected diesel.

I have generally studied all types of gasoline engines, ie: aircraft, motorcycle, auto, racing, etc.

I have yet to study diesel engines in any great detail, although in generally I understand them.

Diesels can get confusing since you can have one like a Detroit Diesel 671 with valves in the head like a 4-stroke engine, and yet it is a 2-stroke.

I will continue studying diesels.

I hope to build a diesel model one day, such as Find's true diesel.
Find's diesel seems significantly more complex than an analogous gasoline engine.

The thing I like about diesel engines is the sound they make, which I guess is the ignition of the fuel, with a distinct detonation sound.

 

[Chris Rayner]

That is a good article, and explains a lot of differences between the hot bulb diesel and the high compression injected diesel.

I have generally studied all types of gasoline engines, ie: aircraft, motorcycle, auto, racing, etc.

I have yet to study diesel engines in any great detail, although in generally I understand them.

Diesels can get confusing since you can have one like a Detroit Diesel 671 with valves in the head like a 4-stroke engine, and yet it is a 2-stroke.

I will continue studying diesels.

I hope to build a diesel model one day, such as Find's true diesel.
Find's diesel seems significantly more complex than an analogous gasoline engine.

The thing I like about diesel engines is the sound they make, which I guess is the ignition of the fuel, with a distinct detonation sound.

Are you acquainted with this: Commer TS3 - Wikipedia ?

 

[GreenTwin]

Are you acquainted with this: Commer TS3 - Wikipedia ?

I will have to study that one.

I have seen some pretty bizzare submarine diesels.

.

 

[Steamchick]

One thing that affects national markets for fuel supply and cost.... the natural fraction of the crude you can get for diesel and petrol bases. This fraction is pretty much a constant for most heavy crude oils. So because thee is a limit to the fuel y can get because of the fraction, the government's fiddle the tax between the fuels to drive consumers towards use of petrol or diesel cars to utilise the balance of production of the fuels versus consumption. Crazy? Actually it is the reason in the UK that we used to have cheap diesel, but few diesel cars, then the market was driven towards diesel cars because of tightening emissions regs on petrol cars (e.g. BMW et al started making their highest performance cars as diesels!) But that screwed the balance of fuel production according to the fractions against the consumption by more diesel cars... so now diesel costs 10% more than petrol!

Comparing high mileage freight trucks'consumption country on country, and small countries (Uk, Holland) have a different solution to large countries (France, USA, Etc.). Hence "not one solution suits all". Emissions strategies in Europe for a time went year zero, petrol rules tightened, year 5, diesel emissions tightened, year 10, petrol, etc. This was partly to ease manufacturers' workload developing better engines. WW1, WW2, and the 1970s oil crises have also had major impacts on engine development. UK had Tetra-Ethyl lead so could get more power from the fuel fraction with higher compression available with higher octane fuels. Germany didn't have huge supplies of Tetra-Ethyl lead so used much more diesel engine power.

In the USA, to balance the fraction of diesel consumed by long-haul (8 wheeler) trucks, small (domestic?) trucks and city delivery vans use petrol engines. All driven by government taxation to balance consumption to the fractions.
One big game...
K2

 

[rutzen]

A great book on how piston engines were developed and the science behind them is Bill Gunston's 'Piston Aero Engines'.

 

[josodl1953]

My favorite book on IC engines is Internal Fire, written by Lyle Cummins, the son of the founder of the Cummins diesel engine manufacturer.
Published by the Society of Automotive Engineers SAE ( yes, the same who established the viscosity standards).
In this book, the development of, and the difference between petrol and diesel engines is explained crystal clear.

Jos

 

[Alyn Foundry]

Some 25 years ago I embarked upon the scaling of a friend’s Hornsby Akroyd oil engine. These engines were the first successful compression ignition oil engines available in the early 1890’s. Hot Bulb is another term used to describe the ignition process. They were designed to run on the cheap, safe and readily available lamp oil of the time. We know this fuel as Paraffin or Kerosene today.
The engine has a small, hollow extension to the cylinder that was heated by a blowlamp. After several minutes of heating the fuel would be spayed into the bulb via a low pressure piston pump that had a spring loaded injector on the other end. By turning the flywheel the piston would compress the air from the cylinder into the hot space now filled with oil fuel vapour and promptly ignite. A governor was fitted that opened a valve on the injector so that on over speed no fuel would be injected.
Despite the project taking nearly a year to complete the engine never quite ran properly. Disappointed with the outcome I decided not to market it as a casting kit. The photos are of the only two 1/4 scale Hornsby Akryod models built.

 

[ajoeiam]

I started tinkering with lawnmower engines at an early age, and took enough of them apart to become familiar with the various parts.

After that, I could pretty much get any gasoline engine to run, just by verifying fuel flow and spark.

Even with low compression, leaking valves, etc. I could get gasoline engines to generally run, perhaps not running perfectly, but running.

My limited experience with diesels has not been the same.
There seems to be a lot more variation with how diesel injection systems are made, and you have to be familiar with the particular one you want to work on.

If the compression is a bit low, you can forget about getting a diesel started, except perhaps with a bit of starting fluid.

The pump and/or injectors on a diesel don't seem to be nearly as simple or forgiving as a gasoline engine carburetor.

If you let a diesel run out of fuel, you generally will have to purge all the fuel lines.

Diesels don't seem to be very tolerant with poor quality fuel, or water in the fuel.
Gasoline engines are not very picky about fuel, although they don't work well with water in the fuel either.

Compared to a diesel engine, gasoline engines are light, simple and relatively inexpensive.

If you need a diesel, such as for a high torque load, or very rugged service, then they will be the most cost effective solution.

My dad was using a 4-cylinder Continental on a transfer car, and they had a lot of problems with the engines wearing out, and not having sufficient torque.
He replaced that engine with a 2-cylinder air-cooled Lister, and he had plenty of torque, and never had to replace the engine.

Automobiles tend to be somewhat lightweight, and a lightweight gasoline engine suits an automobile well, since you generally don't need a lot of torque in a car.

For folks who pull heavy trailers, they generally use a pickup truck with a Cummins diesel in it, since that engine will pull a very heavy load up a mountain without much trouble.

So gasoline engines are relatively simple and lightweight, and many folks know how to repair and maintain them.
Gasoline engines also work well on motorcycles, especially when you want to keep weight to a minimum, such as a motocross bike.

There are good applications for gasoline engines, and good applications for diesel engines, but sometimes I see diesel engines used in an application where a gasoline engine would be more cost effective.

I generally don't see heavy gasoline engines, other than perhaps in ocean tankers and such, but no doubt they exist.
Generally for heavy applications, they just use a diesel, since I think the diesel is more efficient than a gasoline engine.

.

Interesting - - - - my experience was just about diametrically opposite.

I dissassembled a working gas engine early (it never did run again - - - - argh!).
Found that diesels were just so much more straight forward.
If you have fuel flow and air and its turning over like it should (not weak batteries or similar) well you have running!
Gas - - - - spark, enough, and the timing liking to wobble around - - - small engines (thinking Kohler and the like) just added another level of complexity.
Came to despise the huge bore short stroke systems that make a gas engine show lots of power without any real serious torque.
Enough diesels did that (the earlier Detroit Diesels) too.
Motorcycles were quite rare even in the area - - - - newish gravel roads are tough on riders I understand.
Saw heavy vapor engines (actually natural gas) as I grew up in serious oilfield country.
They still use them for pressurizing natural gas lines. (3 or 4 of these take enough space for a smallish house - - - grin.)
I've often enough even driven diesel vehicles.
Many peoples attitudes about diesel vehicles are actually quite amusing - - - they're so 'out to lunch'.

Interesting differences - - - - for sure.

 

[ajoeiam]

One thing that affects national markets for fuel supply and cost.... the natural fraction of the crude you can get for diesel and petrol bases. This fraction is pretty much a constant for most heavy crude oils. So because thee is a limit to the fuel y can get because of the fraction, the government's fiddle the tax between the fuels to drive consumers towards use of petrol or diesel cars to utilise the balance of production of the fuels versus consumption. Crazy? Actually it is the reason in the UK that we used to have cheap diesel, but few diesel cars, then the market was driven towards diesel cars because of tightening emissions regs on petrol cars (e.g. BMW et al started making their highest performance cars as diesels!) But that screwed the balance of fuel production according to the fractions against the consumption by more diesel cars... so now diesel costs 10% more than petrol!

Comparing high mileage freight trucks'consumption country on country, and small countries (Uk, Holland) have a different solution to large countries (France, USA, Etc.). Hence "not one solution suits all". Emissions strategies in Europe for a time went year zero, petrol rules tightened, year 5, diesel emissions tightened, year 10, petrol, etc. This was partly to ease manufacturers' workload developing better engines. WW1, WW2, and the 1970s oil crises have also had major impacts on engine development. UK had Tetra-Ethyl lead so could get more power from the fuel fraction with higher compression available with higher octane fuels. Germany didn't have huge supplies of Tetra-Ethyl lead so used much more diesel engine power.

In the USA, to balance the fraction of diesel consumed by long-haul (8 wheeler) trucks, small (domestic?) trucks and city delivery vans use petrol engines. All driven by government taxation to balance consumption to the fractions.
One big game...
K2

The 'natural' fraction is something that really hasn't been very relevant for quite some time.

Can't remember exactly when - - - think it was in the 80's, that the refineries went to catalytic cracking.
There are even refineries that only make diesel now.

Most of the refineries in at least North America are seriously 'old' - - - - getting permissions to build a new one - - - - very very difficult.
Yet everyone wants the stuff!

(We are getting taxed to death on the 'stuffs too!!!)

 

[ajoeiam]

View attachment 146972
View attachment 146973
View attachment 146971
Some 25 years ago I embarked upon the scaling of a friend’s Hornsby Akroyd oil engine. These engines were the first successful compression ignition oil engines available in the early 1890’s. Hot Bulb is another term used to describe the ignition process. They were designed to run on the cheap, safe and readily available lamp oil of the time. We know this fuel as Paraffin or Kerosene today.
The engine has a small, hollow extension to the cylinder that was heated by a blowlamp. After several minutes of heating the fuel would be spayed into the bulb via a low pressure piston pump that had a spring loaded injector on the other end. By turning the flywheel the piston would compress the air from the cylinder into the hot space now filled with oil fuel vapour and promptly ignite. A governor was fitted that opened a valve on the injector so that on over speed no fuel would be injected.
Despite the project taking nearly a year to complete the engine never quite ran properly. Disappointed with the outcome I decided not to market it as a casting kit. The photos are of the only two 1/4 scale Hornsby Akryod models built.
View attachment 146971

Nice looking engine!

 

[Alyn Foundry]

Just to follow up on my last post. Here’s my 1/3rd scale model of the Robinson HA Oil engine of 1894. The model was completed last year. Still using compression ignition but via a hot tube with permanent lamp. The fuel oil is atomised by a patented “ rattling “ atmospheric valve which then vaporises in the heated cylinder head. The exhaust valve is mechanically operated by another of Horace’s ingenious designs, the epicyclic gearbox.

 

[GreenTwin]

@Alyn Foundry

I have long admired the 1/4 scale Hornsby Akryod, and that is on my list of attempting to build one day.

The Robinson is also a beautiful engine, and I like the style of these two engines very much.

Great work for sure !
Most impressive.

.

 

[Steamchick]

Lots of stuff from everyone. But back to the original question - "What is a diesel engine?". Well, based on Rudolf Diesel's thermodynamic cycle the answer is simple:: a
"Diesel cycle engine follows the thermodynamic cycle as follows- 1. An air intake phase, 2, a closed chamber compression phase (that heats the air adiabatically to a temperature higher than the fuel combustion temperature, and the air is also then at high compression), 3, a combustion phase when fuel is injected into the hot high compression air, during which time the chamber is expanded rapidly to extract the energy from the hot combustion gases thus creating a motive force, finally 4, the exhaust phase when the burnt fuel exhaust is ejected from the engine, so the cycle can start again with a fresh air intake cycle."
Necessary parts of the cycle:
2 compress air rapidly to achieve combustion temperature.
3 inject fuel which immediately burns as it mixes with the hot air, to produce the power extracted by the expanding combustion chamber.
The air intake and exhaust phases can be on many types of engine, but hot air causing the injected fuel to burn is Diesel's unique feature.
Other engines, spark, glow plug or hot bulb ignition are not Herr Diesel's principle.
Research Carno cycle, Atkinson cycle, Ricardo engines, etc. For others.
K2