“The diesel is the great grandfather of the jet engine.
Explanation please.”
The idea of jet engine combustion originated in the diesel design. Both engines are unthrottled, and take in a full charge of air continuously. The air is compressed, and fuel is injected into the superheated (by compression) air resulting in combustion. Power is increased by injecting more fuel, intake air is unthrottled.
Turbocharged diesel design can lower the compression ratio as their turbo boost is increased. Taken to extream, the turbocharger becomes dominant, and the piston becomes immovable, resulting in a burner can instead of a compressiion cylinder containing a movable piston.
Keep upping the size of the turbocharger and size of the burner cans, and you increase the thrust of the engine exhaust. Shaft power can be tapped off the turbo shaft if need be.
Exactly so.
All engines run on some variant of the “suck-squeeze-bang-push” cycle. The differences are:
1. How is the ignition performed?
2. Are the fuel:air ratios constant (as in the Otto gasoline engine) or variable (diesel and turbojet/fan engines)?
3. Where are you extracting the heat & pressure from the combustion? In a diesel, you’re using the piston to extract the energy from the pressure/temperature of the burning air/fuel mixture. In a turbodiesel, you’re using the piston, but then you’re scavenging some more heat+pressure from the exhaust and pushing that back into the engine in the form of higher charge air temps and pressures.
In a jet engine, you’ve done as you’re indicating — you’ve reduced the size of the piston to zero, and you’re running nothing but a huge honkin’ turbo, where you’ve stuffed an intermediate burn can between the input spool and output spool of the turbo. Oh, and you’ve put a longer shaft on the turbines. ;-)
Your description of the diesel design properties reminds of a supposedly true story my neighbor told me about this blonde bartender who innocently asked how a four-stroke engine worked, saying that nobody had been able to explain it to her.
Four guys tried with the usual statements of intake, compression, ignition and exhaust all using colorful and descriptive terms like imagine a vacuum cleaner, think about about fluffling a pillow, light the fireplace, watch a window fan, etc.
An old dude, sittting at the end of the bar, known to be impatient, cranky and spare with words got up off his stool and walking towards the group of young suitors just stepped up between them and said:
” Look Missy, it’s like this - SUCK, SQUEEZE, BANG, BLOW!”
The blonde beamed and said, “Well, why didn’t y’all say so in the first place,” and went back to wiping glasses.
Riddle me this, Batman. How do you maintain the proper stoichiometric ratio? I know how it's done with gasoline engines with both carburetors (shudder) and fuel injection. I just don't understand how it's done with diesel.