Diesel

[a41capt]

Look at this clip . He is a amazing engine builder.

Bengt

Holy crap! That is simply amazing!!! What a skill set this guy's got. Certainly sets the bar high for a guy like me!!!

John W

 

[a41capt]

I know it wouldn’t be a true injected diesel, but I wonder if a variation on the Pogue carburetor with natural aspiration during an intake stroke wouldn’t produce adequate vaporization of kerosene or like fuel to enable adequate mixture and compression ignition.

Preheating of the fuel to above its flash point (I believe Kerosene has a flash point between 100 and 150 degrees F) should generate adequate vaporization for the start, and the use of exhaust gases to continuously warm the mixture during running...

I had an engineer friend that sadly passed away many years ago that called this principle a “perfume” engine.

 

[joco-nz]

In Model Engineer issue 4448, back in 2004, George Punter started a 17 series installment with plans of his model Lister 6/1 disel engine.

I’m still looking to see if anyone has done something more recent in ME.

Cheers,
James.

 

[dkwflight]

Look up
Find Hansen on Youtube.
He does a true diesel injecting Kero I think. He also did som semi diesels too. Fine very small work.
Dennis

 

[lohring]

Model "diesels" have been around a long time. They are compression ignition engines that mix the fuel outside the combustion chamber. The plan book mentioned in recent posts has many examples. Davis Diesel still makes conversions.

Lohring Miller

 

[Iconoscope]

Many years ago, back in the 1950s, diesel model airplane engines were common. These were single cylinder and used the same carburetion setup as the methanol glow plug engines. The cylinder head had a compression adjustment knob. They were notoriously hard to start running, but a lot of modelers liked them!

 

[Geoffrey_Thorpe]

Compression ignition engines used to be somewhat common on model aircraft in the 40's 50's. They had variable compression/mixture to control ignition timing and used a carburetor instead of injection pumps.
Example:

 

[joco-nz]

Just be wary of these model “disels” and the Davis conversions as they rely on a fuel mix containing Ether. If you live in a country where Ether has become a controlled susbstance due to its use in the illegal drug trade Good luck in getting your newly built model running.

I understand the disel models made by Find Hansen http://www.findsminimodelhotbulbengines.dk/ do not rely on Ether in the fuel to operate. It would be awesome if Find was offering plans or even a plan for one of his disel engines however that does not seem to be an interest of his. Pity, but his work, his choice. There are photos and disxussions on his site that may give some insight.

Cheers,
J.

 

[John Lovegrove]

I have made several spark ignition engines and when my current project is done (a 4 cylinder Westbury Sealion) I want to start on a diesel or semi diesel engine. I have studied diesel engine technology and more recently hot bulb and semi-diesel engine technology to try to understand the issues are involved.

From what I can see by using a high enough compression ratio in a model engine, getting a high enough temperature to ignite the fuel is quite possible. The real issue is injecting the tiny quantity of fuel needed and atomizing it to produce droplets that are small enough to mix with the air and burn in the very short time available.

In the early engines they resorted to using high pressure air, somewhat like one does in a paint sprayer, to create small enough droplets to get adequate combustion. The compressor required needed significant power and was a source of unreliability, so there was a huge incentive to make airless or "solid" injection work. By the end of the 1920s this had been achieved for large, low speed diesel engines where there was adequate time for the combustion to take place.

When people started working on high speed diesel engines for vehicles, they had to use high turbulence pre-combustion chambers to get adequate mixing of the air and fuel droplets in the time available. Injection pressures were a few thousand psi. Nowadays, diesel engines in vehicles use direct injection, nozzles with extremely fine holes and pressures of over 30,000 psi.

I really admire Bengt Olausson for the model he has made and his workmanship in making the pump and injector for the engine. The engine obviously runs well without any obvious exhaust smoke under idling conditions. I wonder what happens when more fuel is injected to produce some power and there is less excess oxygen to complete the combustion? It seems to me that it is possible to get an engine run with relatively coarse injection but that combustion will be incomplete and there will be smoke in the exhaust.

I am thinking of starting with a hot bulb/semi-diesel where finely atomized injection is less critical and the heated surface helps turn the fuel into vapour as well as bring about ignition.

John Lovegrove





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