2-stroke diesel is the (near) future?

Sport Pilot wrote:

The model
diesel engines will not turn as fast as the gas or methanol/nitro
engines because the fuel (ether and kerosene) will not burn as fast.


I say again: there is no magic rule that says "diesel burns slower" than
gasoline. Increasing the boost pressure can increase the burn rate AS
MUCH AS YOU WANT. Its just not done most of the time, because no one
WANTS a 7000 RPM engine when a 4000 RPM engine is available to do the
same job. People only build 7000 RPM engines when there's no other way
to get the power.

This is because the fuel burns slower,
not because of the cycle, because all, the spark ignition gas engine,
the glow plug methanol/nitro engine, and the compression ignition
engine, are actually otto cycle engines.

No, that's already been covered. Diesel (true diesel with either direct
or pre-chamber injection) is a subtly different cycle than the Otto
cycle. Its constant-pressure combustion instead of constant-volume
combustion.

Steve writes:

Sport Pilot wrote:

Why the obvious apple and orange comparision?


To refute the statement that "more speed is more power."

You need to compare engines of equal size.


OK, Lets do it!

Dodge 5.9 Liter v8 gasoline engine: 230 horsepower at ~5000 RPM

Compared to:

Dodge/Cummins 5.9 Liter turbo-diesel engine: 325 horsepower at 2900 RPM


More speed is NOT more power any more than more torque at the same
speed is more power.

uh?

More torque at the same speed *is* more power.

power = torque * speed

Had the gas engine produced the same torque at 5000 rpms as the diesel
do at 2900, then it would have had about 560 hp at 5000.

Thomas

"Thomas Tornblom" -to-reply wrote in message
...
Steve writes:

Sport Pilot wrote:


More speed is NOT more power any more than more torque at the same
speed is more power.

uh?


Yeah, that was my reaction! (?) ;-)


More torque at the same speed *is* more power.

power = torque * speed

Had the gas engine produced the same torque at 5000 rpms as the diesel
do at 2900, then it would have had about 560 hp at 5000.

Thomas

Actually, the equation to calculate power (or horsepower (HP) in this case)
is HP = Torque X rpm / 5252.

Torque being a measurable force that turns the crankshaft and ultimately the
wheels, main rotor, or propeller (I just noticed that this is going to two
aviation and one automotive newsgroups). Horsepower is defined as a
"measurement" of work performed. By the equation, at least as it applies to
internal combustion reciprocating engines, you can't have HP without torque!
So, if you can increase the torque value at a given rpm, you'll increase the
power output at that rpm. Likewise, if you can maintain a given torque
value at a higher rpm, you'll produce more power in that case too. It
doesn't matter what kind of engine you're talking about or the fuel burned.
Gasoline, diesel, methanol, it makes no difference. The equation still
applies.

FWIW!
Fly/Drive Safe,
Steve R.

Steve wrote:
Sport Pilot wrote:

Why the obvious apple and orange comparision?

To refute the statement that "more speed is more power."

You need to compare engines of equal size.

OK, Lets do it!

Dodge 5.9 Liter v8 gasoline engine: 230 horsepower at ~5000 RPM

Compared to:

Dodge/Cummins 5.9 Liter turbo-diesel engine: 325 horsepower at 2900 RPM


More speed is NOT more power any more than more torque at the same speed
is more power.

Steve,
As you said power is torque * RPM, so for the same torque more speed
is power. In fact with 0 RPM you have no power only a force. No I
have not argued that desiels cannot deliver power by increasing torque.
Only that their inherent design and fuel limits their maximum speed.
Your example is a poor one most diesels of equivelant size will deliver
more torque at less RPM and have less total horsepower. I don't know
where you found that pitiful Dodge 5.9 liter engine. I have a 4.7 V8
in my Grand Cherokee and it puts out 260+ HP. I know that the 5.7
Liter hemi V8 puts out about 320 or so HP and it is not turbocharged.
So that is a more equal comparison. Unlike the apple orange examples
you put up.

Steve wrote:
Sport Pilot wrote:

The model
diesel engines will not turn as fast as the gas or methanol/nitro
engines because the fuel (ether and kerosene) will not burn as fast.


I say again: there is no magic rule that says "diesel burns slower" than
gasoline. Increasing the boost pressure can increase the burn rate AS
MUCH AS YOU WANT. Its just not done most of the time, because no one
WANTS a 7000 RPM engine when a 4000 RPM engine is available to do the
same job. People only build 7000 RPM engines when there's no other way
to get the power.

This is because the fuel burns slower,
not because of the cycle, because all, the spark ignition gas engine,
the glow plug methanol/nitro engine, and the compression ignition
engine, are actually otto cycle engines.

No, that's already been covered. Diesel (true diesel with either direct
or pre-chamber injection) is a subtly different cycle than the Otto
cycle. Its constant-pressure combustion instead of constant-volume
combustion.

I was not quite correct if I said desiel fuel burns slower, it is
however made to ignite better with desiel engines so that the fuel
ignites spontanously when injected. The fuel burns slower because it
is injected over a period of time. However, I may have been correct
about the model fuel. There are diesel conversion heads for model glow
engines. This replaces the head and glow plug with a head with a
varible compression. You adjust the timing by adjusting the
compression. The fuel is a mix of kerosene, ether, amyl nitrate, and
oil. This fuel will ignite at a much lower temperature than true
desiel fuel. The ether and amyl nitrate are the componets which ignite
at a low temp. Though ether is extremely volatile it is not a very
high energy fuel and I think it burns slowly. These converted engines
will turn large propellers at slower speeds than the glow engines they
were converted from.

Another example of a high energy fuel that limits speed is
nitromethane. Because it is a monopropellent the racers can pretty
much inject as much as their ignition can ignite, except for
hydrolocking. That is if more fuel is injected than the combustion
chamber volume the engine will blow up. But nitro burns slowly so RPM
is more or less limited to just over 10,000 RPM loaded. The slow
burning is why you see huge flames coming out the exhaust.

On Tue, 24 May 2005 21:54:29 GMT, Thomas Tornblom
-to-reply wrote:

Steve writes:

Sport Pilot wrote:

Why the obvious apple and orange comparision?


To refute the statement that "more speed is more power."

You need to compare engines of equal size.


OK, Lets do it!

Dodge 5.9 Liter v8 gasoline engine: 230 horsepower at ~5000 RPM

Compared to:

Dodge/Cummins 5.9 Liter turbo-diesel engine: 325 horsepower at 2900 RPM


More speed is NOT more power any more than more torque at the same
speed is more power.


One BIG factor is being forgotten here. The diesel is turboed. This
makes it roughly equivalent to an 8 liter engine at about 6psi boost.
Any combustion engine produces power in proportion to the amount of
air consumed. On a diesel it does not necessarily "consume" all the
air that goes through it - but the maximum power output is definitely
limitted by how much air can be put through it. A turbo can eisily
double the amount of air an engine pumps through it at a given speed.

Running an engine at double the speed also increases the amount of air
going through the engine - not quite double due to reduced volumetric
efficiency at speed.

Double the CFM gives double the horsepower, before factoring in
frictional losses and / or pumping losses.

A naturally aspirated diesel engine generally produces less HP per
unit of displacement, but more torque at low RPMs due in part to less
pumping loss (no air throttle)
uh?

More torque at the same speed *is* more power.

power = torque * speed

Had the gas engine produced the same torque at 5000 rpms as the diesel
do at 2900, then it would have had about 560 hp at 5000.

Thomas

Steve wrote:
Sport Pilot wrote:

The model

diesel engines will not turn as fast as the gas or methanol/nitro
engines because the fuel (ether and kerosene) will not burn as fast.



I say again: there is no magic rule that says "diesel burns slower" than
gasoline. Increasing the boost pressure can increase the burn rate AS
MUCH AS YOU WANT. Its just not done most of the time, because no one
WANTS a 7000 RPM engine when a 4000 RPM engine is available to do the
same job. People only build 7000 RPM engines when there's no other way
to get the power.

Hydrogen, for example, is a very rapid burning fuel. Hydrogen can and
has been used in Diesels. I also suspect that natural gas, another
common diesel fuel, burns at a high rate. The slow burn rate with many
liquid diesel fuels is due to the time it takes the surface area of the
droplets to vaporize.

wrote:


One BIG factor is being forgotten here. The diesel is turboed. This
makes it roughly equivalent to an 8 liter engine at about 6psi boost.
Any combustion engine produces power in proportion to the amount of
air consumed. On a diesel it does not necessarily "consume" all the
air that goes through it - but the maximum power output is definitely
limitted by how much air can be put through it. A turbo can eisily
double the amount of air an engine pumps through it at a given speed.

Running an engine at double the speed also increases the amount of air
going through the engine - not quite double due to reduced volumetric
efficiency at speed.

Double the CFM gives double the horsepower, before factoring in
frictional losses and / or pumping losses.

A naturally aspirated diesel engine generally produces less HP per
unit of displacement, but more torque at low RPMs due in part to less
pumping loss (no air throttle)

SOME diesels are turboed. Many are not. Some Diesels are normally
aspirated. Some are supercharged with geared chargers. Some are
turboed. It is by far an overgeneralization to claim that all Diesels
are supercharged, even more so to say they are all turbo-supercharged.

Don Stauffer wrote:




SOME diesels are turboed. Many are not. Some Diesels are normally
aspirated. Some are supercharged with geared chargers. Some are
turboed. It is by far an overgeneralization to claim that all Diesels
are supercharged, even more so to say they are all turbo-supercharged.

You forgot supercharged plus turbocharged
http://www.wilksch.com/


--
Pub: http://www.slowfood.fr/france
Philippe Vessaire Ò¿Ó¬

Thomas Tornblom wrote:

Steve writes:


Sport Pilot wrote:


Why the obvious apple and orange comparision?


To refute the statement that "more speed is more power."


You need to compare engines of equal size.


OK, Lets do it!

Dodge 5.9 Liter v8 gasoline engine: 230 horsepower at ~5000 RPM

Compared to:

Dodge/Cummins 5.9 Liter turbo-diesel engine: 325 horsepower at 2900 RPM


More speed is NOT more power any more than more torque at the same
speed is more power.


uh?

huh. Read it again.


More torque at the same speed *is* more power.

That's exactly what I've been saying. You can get more power by
increasing torque OR rpm or both.