Vacume and diesel engines

[Iplayfarmer]

No fair! You have to go to the "Will it Fly?" thread to post your opinion.






PS Yes it will.

You know, assuming it does fly (which it will) how does a non-turbo airplane engine deal with the drastic differences in altitude and pressures that it encounters through a routine flight? Does the carburetor somehow adjust itself?

 

[Hooked_on_HP]

Now we are really getting away from my original argument.
Bill

 

[jake98]

You know, assuming it does fly (which it will) how does a non-turbo airplane engine deal with the drastic differences in altitude and pressures that it encounters through a routine flight? Does the carburetor somehow adjust itself?

"Drastic differences" aside, there's a knob called 'mixture' next to the throttle. Drastic is covered in 'Emergency Procedures'. Get a grip, ...how's it go? ...aviate,navigate,...something else...

 

[jake98]

"Drastic differences" aside, there's a knob called 'mixture' next to the throttle. Drastic is covered in 'Emergency Procedures'. Get a grip, ...how's it go? ...aviate,navigate,...something else...

Now we are really getting away from my original argument.
Bill

Hey Hooked, What's with that Chevy? Looks like you got some illegals an a bunch of tools in the trunk...

Jake

 

[Redneck in training]

Gasoline aircraft engines have very simple carbs. Therefore it is at the pilot to adjust the mixture for correct fuel to air ratio. There are fuel injected (either mechanical or electronic) aircraft engines that are so called single lever where mixture is automatic. All diesel aircraft engines are single lever.
Car engines are much more advanced. The fuel injection system measures mass flow of air (set by the throttle) and calculates how much fuel should be injected. Since the mass flow measurement isn't completely precise the engines have other sensors such as oxygen sensor that is used to correct for mass flow measurement imperfection. The idea is to run the engine as lean as possible.
Speaking about tractor diesel engines. Most of new tractor diesels are turbocharged to comply with clean air act. I don't know why turbo engines have cleaner exhaust yet. The side effect is that they should be also more fuel efficient because the turbo recovers some of the energy in exhaust fumes and use it to run a compressor that charges the cylinder. Well the diesels have a throttle. It is called suction valve. Due to mechanical issues the lift and thus opening of the valve is limited. The valve causes the larges pressure drop in the suction tract of the engine. Also the valve is opened for very short time. Therefore the pressure in the cylinder of NA engines (gas or diesels) never reaches atmospheric pressure. Since compressor engines maintain much larger pressure in the suction tract they can fill the cylinders faster and to higher pressure. Since there is more oxygen you can add more fuel and get more power.
Some large low rpm engines such as diesels in boats have turbines in exhaust coupled with the crankshaft. Since the turbine recovers some energy from the exhaust such engines have very low specific fuel consumption.
Typical NA gasoline engine has SFC about 0.5 lb/HP/hour about 32% efficient
Typical NA tractor diesel engine has SFC about 0.4 lb/HP/hour.
Typical TC small diesel has SFC about 0.33 lb/HP/hour
Larger truck TC engines have SFC about 0.32 lb/HP/hour
Very large TC boat engines have SFC about 0.26 lb/HP/hour 54% efficient.

 

[Hooked_on_HP]

Hey Hooked, What's with that Chevy? Looks like you got some illegals an a bunch of tools in the trunk...

Jake

No illegals or ant other extra weight. Just a whole lot of playing with the chassis.509ci and 10.5 tires. BTW thats on the way down.
Bill

 

[john_bud]

Speaking about tractor diesel engines. Most of new tractor diesels are turbocharged to comply with clean air act. I don't know why turbo engines have cleaner exhaust yet. The side effect is that they should be also more fuel efficient because the turbo recovers some of the energy in exhaust fumes and use it to run a compressor that charges the cylinder.


Typical NA gasoline engine has SFC about 0.5 lb/HP/hour about 32% efficient
Typical NA tractor diesel engine has SFC about 0.4 lb/HP/hour.
Typical TC small diesel has SFC about 0.33 lb/HP/hour
Larger truck TC engines have SFC about 0.32 lb/HP/hour
Very large TC boat engines have SFC about 0.26 lb/HP/hour 54% efficient.

I don't "know", but assume that turbos gain some fuel economy by heating the intake air which better volatilizes the fuel so it can be fully combusted.

I didn't know the specific combustion figures for the larger trucks and turbocharged diesels. Thanks for posting. Do you have a link for further reading?

 

[Egon]

I don't "know", but assume that turbos gain some fuel economy by heating the intake air which better volatilizes the fuel so it can be fully combusted.

Intercoolers???

 

[SPYDERLK]

Intercoolers???

For gas, cooling= more power potential. not more efficiency. For diesel - both, as long as the intercooler is not restrictive and the combustion chamber surfaces stay hot.
larry

 

[Redneck in training]

Turbocompressor removes energy from the exhaust gases. The gas exiting the engine is hot and has high velocity. It expands trough the turbine and generates power that is used to run the compressor. The temperature and especially the velocity of the exhaust gases downstream of the turbine are significantly lower. The energy from the exhaust gases is then transferred to intake air that is forced in to engine instead using the engine piston to suck it in. That is your gain. Intercooler increases the efficiency of the whole process. The compressed air is hot therefore has larger volume than cooler gas of the same pressure. Removing some of the heat decreases its volume. Therefore the velocity of the air in the suction decreases. Since the resistance of the suction (sum of all resistances such as filter, suction duct, manifold, suction valve etc.) changes with square of velocity the intercooling heat loss is made up by gains achieved by lower air velocity. The end result is that you can stuff more air (oxygen molecules) in the combustion chamber, burn more fuel and get more power. This works up to the point of mechanical and material limits of the engine. Increasing power beyond such limit will destroy the engine. In example some racing engines last only several hours.

When I was a teenager I used to race quite successfully small boats (you know the big heart and little brain syndrome). Typical boat engine produced about 50 HP from 175 CC displacement burning pure methylalcohol. That is about 285 HP/liter. The trade off was that the engine lasted about 8 hours between overhauls.
Typical tractor diesel produces about 20 HP/liter. That is why they last forever.
For SFC and other interesting data google "Specific fuel consumption, piston engine".