Formulas for calculating the bore and stroke of a diesel engine

[peterl95124]

Minh-Thanh, those "perfect conditions" are good enough for calculating loads required of a Diesel con-rod, required injection pressure, and anything else you can think about. "flash point" and "auto ignition" temperatures are both irrelevant for Diesel operation. so what's your point ? Pete.

 

[minh-thanh]

Same old saying: never reach 700 degrees C !!!!

"flash point" and "auto ignition" temperatures are both irrelevant for Diesel operation. so what's your point ? Pete.

Ook...Ook....Ok....I stop here !!!!

 

[GreenTwin]

I think it is safe to say that when using a 21:1 compression ratio, diesel fuel will combust when injected into the cylinder at TDC.
So does it really matter what that exact temperature is ?
Regardless of the temperature, diesel will combust under these conditions, and so that is what is critical for a diesel engine to operate.

.

 

[ruben]

Hello thanks for your help

 

[ruben]

I think it is safe to say that when using a 21:1 compression ratio, diesel fuel will combust when injected into the cylinder at TDC.
So does it really matter what that exact temperature is ?
Regardless of the temperature, diesel will combust under these conditions, and so that is what is critical for a diesel engine to operate.

.

I don't care about the exact temperature, as long as the diesel burns, that's enough for me.

 

[Steamchick]

It becomes more complex when you are trying to make a million engines a year, to meet stringent emissions criteria, so you want to combust at a high temperature for (thermodynamic) efficiency but not exceed 900deg.C to avoid making toxic NOx gases in the exhaust. Collects a Gov't fine if you get it wrong! And complete combustion before the gases expand and cool below about 300C when CO combustion stops. - otherwise you get High CO and a Government fine.

But HOBBY engines are just that. Usually replicas of a real old engine, or a simple engineering principle (Oil burns better at high pressure and temperature). So fortunately we can still run them on proper old recipe oil fuel.
(Unlike Steam engine guys who now have to use smokeless coal and non-coal, etc. in various countries! Wood pellets in a boiler designed for Steam Coal are not good! And my 45 year old Moto Guzzi doesn't do well on today's 95octane 10% Ethanol/Petrol compared to the 101octane leaded stuff it was designed for.).
Enough of my whinging.
WELL DONE for making proper engines that work!
What a gorgeous engine in that video Green Twin.
Here's an engine i saw on Sunday at a show.

K2

 

[Steamchick]

Here's an engine I saw in Sunday at a show.

 

[xander janssen]

I'm also looking into building a diesel engine like the one of mr. Find Hansen. If you carefully follow his youtube videos, he gives away some numbers. His green engine has a bore of 20 mm and a stroke of 40 mm which compresses into a head clearance (diameter 20 mm) of 1 mm and a combustion chamber of diameter 7 mm and 8 mm deep. This for sure helps in mixing the air and the fuel as there will be a lot of swirling air. This is where I put my money on for my first design.

Indeed, (almost) adiabatic compression gives much higher pressure (due to increased temperature) than compression ratio would tell you. The numbers regarding forces are enormous as Mr. Hansen also clearly points out. Hence the need for some good lubrication and a very sturdy design.

Once my engine is running, I will make a full set of drawings (with at least the critical dimensions) and make them available to any other interested person.