Are LH/RH Lim lit up with overtorque or reaching the point right before?

[BitMaster]

Um, Bit, what part of Newtons Laws of Motion have anything to do with efficiency of a heat engine?

 

 

3rd Newtons Law, Lex Tertia:

 

F a -> b = -F b -> a

 

Lemme recall, that when you push one masse into direction A you also push yourself with the same force into the opposite direction. Now look at a cylinder --> Up-down-up-down...

It is not that bad with a rotating mass like Wankel or Turbine blades BUT the thrust going out the back is lost, you only use that thrust that is produced by the expanding gases that push FORWARD

and thus push the plane forward. Its a 50/50 game, any way you look at it, YingYang et al.

 

Half of the energy is lost by default with all "burning" engines like rocket motors, car engines etc.. also any heat produced is lost energy, anything in motion inside is lost energy.

 

In comparison, E-Motors can achieve 80+%efficiency out of the box, easily but if you propel a propeller or turbine-blade with it, you directly loose 50% thrust by definition, just your engine runs more efficient but the actual propellant drive stays were it was, 50ish.

 

I have some books and articles about Propeller efficiency.... when they refer to 60% eff. with this blade and shape or 45% with that one...they all refer to the 50%.

It's then 60 or 45% out of those 50% they can tab.

 

Basically, it's like going to the Bank to save money these days, put in 10k...come back 6months later and only have 4k left....ooops NEWTON !!!!!!

 

 

Bit

Edited August 24, 2014 by BitMaster

[BitMaster]

Make this test:

 

Pour some water of a some icy cold tarmac, then place a walmart trolly in front of you and try to push it, the heavier it is ( mass/mass ) the more likely you will only push yourself BACKWARD.

 

Might be an overdose on how this works but basically this is it.

 

It's one of the fundamental laws of motion and force, heck, this is why I sweat so much.

Inefficiency by nature ;)

 

 

Bit

[Flagrum]

Make this test:

 

Pour some water of a some icy cold tarmac, then place a walmart trolly in front of you and try to push it, the heavier it is ( mass/mass ) the more likely you will only push yourself BACKWARD.

 

Might be an overdose on how this works but basically this is it.

 

It's one of the fundamental laws of motion and force, heck, this is why I sweat so much.

Inefficiency by nature ;)

 

 

Bit

Caution: layman alarm!

 

I understand the principle of force and the countering force.

 

But ... if the trolly has the same mass as me and I push it away so it results in a motion of, lets say 5 feet per minute - then I will be moving with the same speed into the opposite direction. Fine. But now I stand with the back against a wall. I apply the same force at the trolly again, but now the trolly moves with 10 fps, right?

 

Would that not also apply to a piston engine where the mass of the piston is about negligible compared to the mass of the engine as whole (+ attached aircraft)?

 

I have a gut feeling that I am mixing up terms like mass and force and energy ... I guess that is why my example is wrong? :o)

[BitMaster]

Caution: layman alarm!

 

I understand the principle of force and the countering force.

 

But ... if the trolly has the same mass as me and I push it away so it results in a motion of, lets say 5 feet per minute - then I will be moving with the same speed into the opposite direction. Fine. But now I stand with the back against a wall. I apply the same force at the trolly again, but now the trolly moves with 10 fps, right?

 

Would that not also apply to a piston engine where the mass of the piston is about negligible compared to the mass of the engine as whole (+ attached aircraft)?

 

I have a gut feeling that I am mixing up terms like mass and force and energy ... I guess that is why my example is wrong? :o)

 

Flagrum, close.. :)

 

You almost got it, the amount of energy put into both systems ( trolly and you ) is equal

but the trolly gets in it a form called velocity and you just heat up, bend and sweat, maybe even turn some gravel over while you try to overcome inertia first place. All that energy summed up is equal to the force the trolly receives.

 

In a piston engine, most of the energy set loose from breaking up molecules and releasing the binding energy in form of heat will cause two things: it will move your piston and it will also, to a greater part, heat up your engine and twist your frame and thus also heating it up. With a F1 car, you may get 30% into velocity, 70% puffs up in lost energy that you then need to shovel away with fans, consuming some of the 30% useable energy for fans and radiator pumps.

 

Whatever you move, lift or apply ANY kind of force to, remember Newton's 3rd law :)

 

Some say, Ying & Yang principle. Cant have one without inducing the other.

 

 

Bit

[Flagrum]

@BitMaster:

I am unsure if that answers my question ... maybe I did not really understand your answer or I my question was based on wrong assumptions ...

 

In your previous posting you said, a piston engine can at best utilize 50% of the energy to put something into motion. That a largish amount of energy just gets wasted by heating up the engine and the air aside - let us talk only about the part that is converted into some sort of motion.

 

Now again, the trolly example. The trolly and I have the same mass. Also let's assume that there is no friction - the trolly has frictionless wheels and I am also standing on a frictionless skateboard. Now I push the trolly away from me with a force X. The trolly moves from it's initial position with a speed that is equivalent to X/2 and I do the same. Recoil principle (is that the correct english term?). Piston vs. cylinder -> the part that is used to make stuff move is the piston and it can only utilize half of the total energy put into the engine.

 

Next experiment: now I have infinite mass (or I fake it by standing with my back at a wall). I push the trolly again with a force of X. But now I keep standing at my initial position while the trolly moves with a speed equivalent to X.

 

For our piston engine: the engine itself and the aircraft that is connected to it has significantly more mass than the pistons. The pistons therefore "recieve" more energy ...

 

(pause ... thinking ...)

 

No, I got it now, i think. The pistons do not "receive" more energy. Both, piston and engine receive the same amount. The energy is translated into motion - for both, engine and piston. The difference is just that the pistons move faster than the engine.

 

If a brick of 1kg hits something with 50 km/h or a brick of 0.5 kg with 100 km/h or a brick of 2kg with 25 km/h - the energy at impact is always the same .... riiight? :o)

[BitMaster]

@BitMaster:

I am unsure if that answers my question ... maybe I did not really understand your answer or I my question was based on wrong assumptions ...

...

...

 

If a brick of 1kg hits something with 50 km/h or a brick of 0.5 kg with 100 km/h or a brick of 2kg with 25 km/h - the energy at impact is always the same .... riiight? :o)

 

 

 

Ehhh not quite true:

 

T = ½ x m x v² ( x is the multiplier sign ) = 1/2mv²

 

as you can see, the velocity squares.

 

Now your examples:

 

1: 1kg @ 50km/h

T = ½ x 1kg x (13,89ms)² = 96,47 Joule

 

2: 0,5kg @ 100km/h

T = ½ x 0,5kg x (27,78ms)² = 192,92 Joule

 

3: 2kg @ 25km/h

T = ½ x 2kg x (6,945ms)² = 48,23 Joule

 

 

Your assumption is wrong and mislead. What is true is this, double velocity is a four-fold in energy.

 

Lets take example "1" and use 100km/h, double the original speed:

 

T = ½ x 1kg x (27,78ms)² = 385,86 Joule ( exactly 4 x the energy ( v² !! )).

 

 

A simple example from RL is your car. The meters needed to stop a car go up x 4 if you double the speed. Also if you crash into something....double the speed = 4 x more ouch ;)

 

 

THIS ALL "ONLY" APPLIES TO SPEEDS WAY BELOW "C" ( SPEED OF LIGHT ) = STANDARD, NON-RELATIVISTIC NEWTON LAWS.

 

AS SOON AS YOU GET LIKE 0,2C THINGS CHANGE DRAMATICALLY AND MASS AND SPEED SHOW THEIR CORRELATION THROUGH E = MC².

 

WITH NEWTON YOU CAN BUILD A HOUSE AND CONSTRUCT CARS AND BRIDGES BUT YOU WONT MAKE IT TO THE MOON OR GET A SATELLITE PLACED WELL. THAT ALL NEEDS EINSTEIN TO FUNCTION.

 

This, is a totally different story. There are very nice YT vids that demand no pre-knowledge to get the understanding for everyday life.

 

I am happy I did my Abitur ( kind of german high school you need to qualify for studying ) in Physics and Chemistry ( and english, shame on me ). I never actually needed those Heisenberg and Einstein equations or Pauli's Understanding of Electron spins in my job but it helped me to understand the world I am living in a lot better ;)

 

I hope this somehow explains the Ying and Yang of energy forms and that many things are squared and thus tilt the human brain. Humans cannot really think exponential. We do lack some

form of guessing how large things do get once we screw with them. Examples in RL are plenty.

 

The human brains just doesn't wanna think² or even³. This has been proven by an array of scientists.

 

Bit

[Blackeye]

3rd Newtons Law, Lex Tertia:

 

F a -> b = -F b -> a

 

 

I'm not sure Newtons Laws have a lot to do with this.

 

It's been a while but I think it's down to thermodynamics: you have some place hot and transfer the heat to somewhere cold and use some of that energy to generate mechanical movement, i.e. a heat engine.

 

The ideal representation of this is the carnot heat engine and according to Carnots theorem no heat engine can be more efficient than this theoretical device.

The efficiency of a carnot heat engine solely depends on the absolute temperatures of the hot and cold reservoirs: n = 1 - Tc/Th

 

For a piston engine these temperatures are strongly linked to the compression, i.e. a higher compression results in a larger difference between Tc and Th and thus a more efficient engine. (that's why Diesel engines are generally more efficient than Otto engines)

 

Real engines of course have additional losses like friction.

[BitMaster]

Men flew to the moon by using Newton's 3rd Law to take off, then Newton's 1st Law to travel the distance without further propellent and again the 3rd Law to slow down and land.

There is really no dispute about any of this. Some Kepler and some Einstein was needed too to precisely get into orbit and "stay" there.

 

 

Thermodynamics is still about ordinary baryonic matter, and matter has to follow the rules. It doesn't matter if you look at two cars colliding or hot gases escaping the nozzle, the law is the same.

 

I know about that engine you mention. There are many more theoretical principles about movement. The problem is to implement them as ideal as possible to not stumble over friction,

radiation aka 2nd thermodynamic law which say each system in motion radiates energy, no exclusion..even black holes do. SETI even tried to find 3rd level Civilizations ( those control complete Galaxies ) by the radiation their Galactic Protection Shield would emit ( Dyson Shield ). No joke !

 

We are far away from the Perpetum Mobile ;(

[Blackeye]

Sure Newton is helpful whenever you want to calculate forces and motion of bodies.

 

So if you want to know the forces a piston encounters during its movement you need Newton; when flying to the moon you definitely need Newton.

 

However Newton won't help you when dealing with the efficiency of a heat engine - like a piston engine.

 

However Carnots theorem tells you the lacking efficiency is not a problem with the actual implementation of your piston engine (it may add on on top of this though) but regardless of how your engine is designed, you fundamentally cannot get better than the value defined by the two working temperatures.

And you cannot calculate or explain this with the Laws of Newton.

 

Since you mention Perpetum Mobiles - there's nothing in the Three Laws of Motion that would disallow those - they do however violate the laws of Thermodynamics.

Edited September 2, 2014 by Blackeye

[BitMaster]

Blackeye,

 

I am not into Carnots theorem, however, the 2nd Law of Thermodynamics pretty much voids any

chances for any perpetual mobile. Sure, there are types of engines that transfer energy more efficiently than others. I was just about to say, either way you turn, as soon as motion is involved

50% of your energy goes the other way out.

 

But we should stick to the Ka's turbine...

 

Bit

[Blackeye]

I was just about to say, either way you turn, as soon as motion is involved 50% of your energy goes the other way out.

 

An that is not quite correct.

 

Let's take your trolley example and assume that the trolley is the thing you want to actually move. And also let the masses be 10kg for the trolley and 100kg for the one pushing.

 

The overall impulse (m*v) has to stay constant. So if we assume a final velocity of 10m/s for the trolley its impulse is 100 kg*m/s which results in a speed of 1m/s for the person (100kg)

The energy of the trolley is then 0.5*10kg*(10m/2)^2 = 500 kg*m2/s2 and for the person it's

0.5*100kg*(1m/2)^2 = 50 kg*m2/s2.

 

In this scenario 91% of the energy went into the trolley while 9% went into the person, so where the energy ends up is highly dependent on the masses involved.

 

 

Of course in this scenario we're not talking about the process of generating movement out of heat (like in a turbine or piston engine) but simply about energy distribution when you start to push freely moving things around.

 

The efficiency of heat engines i.e. converting heat into motion has nothing to do with this.

 

 

Edit: Going back to the Ka-50 we have

 

1) a turbine burning fuel and generating power on its shaft

This is a heat engine whose efficiency is limited by the carnot process and the accompanying theorem. Of course there are better formulas to calculate/estimate the efficiency of a real world turbine - still the temperature pools define the possible maximum. No Newton involved.

 

2) a rotor converting the motion of the drive shaft into thrust into motion of the helicopter

That's a pretty complex process and it's also not obvious how you would define efficiency. Newton is probably helpful here.

Edited September 2, 2014 by Blackeye

[KLR Rico]

Here is an excerpt from an engine service manual about turbine life:

The time-temperature-rpm relationship within the engine is the main factor in engine life. The most important of these is temperature. The strengths of the materials used in the engine decrease as high internal temperatures approach the melting points of the metals, even though the danger point may not be closely approached. There is a tendency for any material to take a permanent set, stretch, or bend. This tendency increases with both the load and the temperature. The amount of permanent set increases with the length of time that the load and/or temperature is applied. After a certain amount of permanent set is attained, the fiber or grains of the material begin to pull apart. Under inspection with a high powered microscope, the beginnings of fine cracks may be seen. With additional time, the material begins to elongate at faster rates as the cracks become bigger and deeper. Finally, the material breaks. This process is so slow that elongation is perceptible only with careful measurement. The term creep has been applied to the process because of the length of time required for elongation to become significant In a turbine engine, high load and high temperature are usually experienced at the same time. The loading on the turbine and compressor blades is principally the combined result of the centrifugal force, associated with rpm, and some gas or air load, associated with engine internal pressures. When the turbine discharge pressure, which is indicative of other internal pressures, is high, the EGT is also high. This means that when the turbine blades are subjected to their heaviest load, the material of which they are constructed will be at its weakest. The compound effect of high rpm and high temperature results in an astounding increase in the rate of creep at very high thrust settings when the centrifugal load is the greatest. The ends of the compressor blades and the rims of the turbine wheels tend to travel outward. The rate of creep, which is measured in millionths of an inch per hour, increases tremendously as the rpm and EGT approach maximum.

 

I'd like to also note that running at 100% isn't *nessisarly* bad, the T56 engine used in the C-130 runs at a constant 100% in flight. Also, I saw ceramic blades mentioned, those are in use, at least for the 1st stage of the T56-15, almost certainly in other engines. Some of the newer engine designs even have turbine blades "grown" from a single crystal.

[AlphaOneSix]

For these particular engines, the limit is 97.5% with no time limit, 99% with a 1-hour time limit, and 101.15% (the absolute/governor limit) with a 30-minute time limit.

 

EGT limits are 915C with no time limit, 955C with a 1-hour time limit, and 990C (again, this is the governed limit) for 30 minutes.

[BitMaster]

An that is not quite correct.

 

Let's take your trolley example and assume that the trolley is the thing you want to actually move. And also let the masses be 10kg for the trolley and 100kg for the one pushing.

 

The overall impulse (m*v) has to stay constant. So if we assume a final velocity of 10m/s for the trolley its impulse is 100 kg*m/s which results in a speed of 1m/s for the person (100kg)

The energy of the trolley is then 0.5*10kg*(10m/2)^2 = 500 kg*m2/s2 and for the person it's

0.5*100kg*(1m/2)^2 = 50 kg*m2/s2.

 

In this scenario 91% of the energy went into the trolley while 9% went into the person, so where the energy ends up is highly dependent on the masses involved.

 

 

Of course in this scenario we're not talking about the process of generating movement out of heat (like in a turbine or piston engine) but simply about energy distribution when you start to push freely moving things around.

 

The efficiency of heat engines i.e. converting heat into motion has nothing to do with this.

 

 

Edit: Going back to the Ka-50 we have

 

1) a turbine burning fuel and generating power on its shaft

This is a heat engine whose efficiency is limited by the carnot process and the accompanying theorem. Of course there are better formulas to calculate/estimate the efficiency of a real world turbine - still the temperature pools define the possible maximum. No Newton involved.

 

2) a rotor converting the motion of the drive shaft into thrust into motion of the helicopter

That's a pretty complex process and it's also not obvious how you would define efficiency. Newton is probably helpful here.

 

 

Please consider this:

 

The 50% energy being directed into the OPPOSITE direction will not always result in a motion that you can observe with your naked eye. The heating up of your body, the bending of the steel wires forming the cart, the twist and moves of your body while you actually stand still...sum ALL of this up and you get to your 50%.

 

BTW, your refer to the Law of Impulse, that really depends on the masses involved BUT you are NOT SLAMMING against the trolly, you already form 1 entity and from there on you try to push it. Please compare apples to apples and plums to plums. What you described is a different physical process.

 

I am afarid, there is no escape from this.

 

You are also arguing with Newton, not with me ;)

 

We should open a new thread, Basics of Physics ... and do further discussions there.

 

Bit

Edited September 3, 2014 by BitMaster

[Blackeye]

The 50% energy being directed into the OPPOSITE direction will not always result in a motion that you can observe with your naked eye.

 

Wrong.

There are no "50% of the energy directed in the opposite direction" - Newton talks about FORCES - those laws say nothing about energy.

If you want to know the energy distribution you'll have to look at the laws and formulas dealing with (kinetic) energy (and impulse in this case).

 

The heating up of your body, the bending of the steel wires forming the cart, the twist and moves of your body while you actually stand still...sum ALL of this up and you get to your 50%.

 

Wrong.

If you're talking about how the energy is generated in the first place (chemical reaction) then that has nothing to do Newton and the loss might amount to any value - 50% would be a huge coincidence.

 

The deformation energy of the bodies is pretty negligible as long as the push takes place over an extended period of time (i.e. no explosion)

You could also replace the pushing muscles with a loaded spring and the heat up of that spring expanding and pushing does definitely not amount to 50% of the kinetic energy of the two bodies afterwards.

 

 

BTW, your refer to the Law of Impulse, that really depends on the masses involved BUT you are NOT SLAMMING against the trolly, you already form 1 entity and from there on you try to push it.

 

Does not matter for the Law of Impulse. It applies regardless of how the bodies are composed before and after or how they interact - sum of V*m has to remain the same (V as vector) no matter how many parts make up that sum or what happens in between.

 

Please compare apples to apples and plums to plums. What you described is a different physical process.

 

Not at all. That's exactly what's happening when you push a body and you both are freely moving.

 

You are also arguing with Newton, not with me ;)

 

Not arguing with Newton here - he's right and dead anyway.

But your interpretation of those laws is wrong or more specifically they do not apply in the way (and where) you seem to think they do.

 

We should open a new thread, Basics of Physics ... and do further discussions there.

 

Feel free to do so or message me - in German if you want.

Edited September 4, 2014 by Blackeye