Another try to build an engine running with diesel fuel

[Mechanicboy]

In semidieselengine the fuel is hitting the hot part of hot bulb and there will evaporate and ignite fuel, in fact the semidieselengine is less sensitive for bad atomized fuel and will run. If the exhaust smoke is white, it means too much fuel or not enough compression of ratio. Is the hot bulb glowing before you tried to start the engine?

1: Adjust smaller amount of fuel
2: Increase compression of ratio
3: Reduce loss of heat from hot bulb to cylinder head

 

[Mechanicboy]

One more thought!
The differential pressure between the combustion chamber and the fuel pressure must be very high. Otherwise you won't get any spray inside the combustion chamber. I. E. If your compression pressure inside the engine is let's say 20 bar and your fuel pressure is 25 bar, the difference is only 5 bar. That's not enough to form any spray inside the engine. The fuel will just form drops inside. You must at least have the same difference in pressure that you have when you test your injector at normal room pressure. You can achieve this by adjusting the spring pressure of the injector needle. The bigger the difference the better it is.
Hope I could explain what I mean.

Stefan

Stefan..

This is wrote for the real diesel engine.
In the semidiesel engine do not have adjusted fuelpressure for atomizing the fuel as we find in the diesel engine.

The semidiesel engine has a pump who has a big diameter and short stoke to inject the fuel in short time, the fuel injector does not have the pop of valve to atomize fuel. The fuel under full load is not atomized and goes direct into cylinder, ignited by heat of compression. The fuel under idling is atomized or directed to hot part of hot bulb to evaporate and ignite the fuel. (Injector has 2 ways to select to inject into cylinder or hot bulb selected by operator depending on load of engine)

 

[Chicken]

Hi!

Now this is so frustrating, I reduced the compression to 6:1, attached a carb and coil with spark plug, and it fired right away and runs perfectly smooth. Although my left flywheel wobbles quite a bit

Anyway, here it is running on gasoline:

[ame]https://www.youtube.com/watch?v=7h2mRWFsjmY[/ame]

I will rework my whole hotbulb design. I think my heat isolation was too bad so I never reached the correct temperature to ignite the diesel.

best regards,
Alex

 

[ShopShoe]

Your engine running as a hotbulb would definitely be interesting.

However, I think what you have achieved is a very nice looking and running engine even when running the way it is now.

I especially like the way it sounds as it runs steadily on. It reminds me of the Oilfield engines.

Thank you for posting and I hope you keep pursuing the hotbulb idea.

Regards,

--ShopShoe

 

[Niels Abildgaard]

At what crankangle did You inject the fuel?
As I remember it was done sligthly after bottom dead center in hotbulb engines.
Try Youtube for Hundested motor

 

[Mechanicboy]

At what crankangle did You inject the fuel?
As I remember it was done sligthly after bottom dead center in hotbulb engines.
Try Youtube for Hundested motor

Niels..

We has still Hundested hot bulb engine in some fishing boats in Norway, these Hundested semidiesel engine has hot bulb or glow plug (to start engine without heat up the hot bulb only) to ignite fuel. Also the engine has high ratio of compression and do not need earlier begins of injection before TDC as you said after TDC who is common in low compression hot bulb engine.

In my earlier Sabb Semidiesel had a fuel injection begins at 5 degree before top dead center. Compression was high, impossible to turn the engine over TDC.

Some hot bulb engine can have injection begins at 25-30 degree or more degree before TDC and some 10-15 degree or lower degree before TDC depending on how heat is the heat generated by compression depending on size of ratio of compression.
In older hot bulb engine who has low compression then injection begins long before TDC and hot bulb engine to example after 1950 has high compression need injection begins not far away from TDC.

Hot bulb engine ---> low compression, ratio of compression 5:1-7:1
Semidiesel---> High compression, ratio of compression 7:1-10:1

In model engine is much difficult to keep enough heat to ignite the atomized fuel by hot bulb due loss of heat via cylinder head and difficult to make the finest atomized fuel. Ratio of compression must be high than in the big engines.

 

[Stefan-K]

Alex
Too sad that you gave up.
I am convinced that you were very close to a running engine

 

[ChrisLister]

Is there a way of using an oil nozzle from a central heating system to evaporate the fuel?
Greetings,
Chris

 

[gus]

Runs like the old fashion single cylinder Ruston Engine very popular in the Malaysian Rubber Estates and Factories in the 50s and 60s. Made to last forever. No worry about spare parts,the machineshops can make the piston rings, remetal the main bearings and con-rod bearings. The gasket shops can custom make the copper clad outerhead gaskets but they don't come cheap.

 

[Chicken]

Stefan, I did not give up. I will keep on trying. But I have to rework the whole hot bulb design, as I just loose too much heat to the cylinder head. Maybe some glass ceramic isolation will do the trick, or as with the engines of Find Hansen, a long, very thin walled stainless steel tube.

The test with gasoline was just to see if it runs in principle. And it does...